CN219780106U - Photovoltaic power generation system and its inverter, fault protection device and combiner box - Google Patents

Abstract

The utility model discloses a photovoltaic power generation system and its inverter, fault protection device and combiner box, and relates to the technical field of photovoltaic power generation. The inverter includes: multiple power conversion units; multiple protection switch units, each protection switch unit includes multiple protection switches, and each protection switch unit is suitable for correspondingly connecting a photovoltaic string unit to a power conversion unit, To form at least two photovoltaic string branches, the photovoltaic string branches are suitable for connecting one photovoltaic string or two parallel photovoltaic strings, and there are common positive or common negative power conversion units in multiple power conversion units. In this case, the protection switch units corresponding to the power conversion units with a common positive or a common negative share the protection switches when connecting the corresponding photovoltaic string units, so that when the protection switch units corresponding to the power conversion units with a common positive or common negative are disconnected The corresponding photovoltaic strings are disconnected through at least three protective switches. As a result, the number of protective switches can be reduced.

Description

Photovoltaic power generation system and its inverter, fault protection device and combiner box

Technical field

The utility model relates to the technical field of photovoltaic power generation, and in particular to a photovoltaic power generation system and its inverter, fault protection device and combiner box.

Background technique

In a photovoltaic power generation system, multiple photovoltaic strings are connected to the power conversion unit through a fault isolation circuit, so that the generated power is provided to the power conversion unit through the fault isolation circuit. Among them, the fault isolation circuit uses a DC switch with a breaking function. When the photovoltaic power generation system fails, such as a short circuit or reverse connection in the photovoltaic string, a fault occurs inside the power conversion unit, etc., the DC switch can be controlled to break. Isolation between photovoltaic strings and power conversion units.

However, the fault isolation circuit in the related art has a problem of high cost.

Utility model content

The utility model aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the purpose of this utility model is to propose a photovoltaic power generation system and its inverter, fault protection device and combiner box, which can reduce the number of protective switches without increasing the withstand voltage level of the protective switches, thereby reducing the Cost and size of the protection switch unit.

In a first aspect, embodiments of the present invention provide an inverter for a photovoltaic power generation system. The photovoltaic power generation system further includes a plurality of photovoltaic string units, and each of the plurality of photovoltaic string units includes at least N photovoltaic strings, N is an integer greater than or equal to 3. The inverter includes: multiple power conversion units; multiple protection switch units. Each protection switch unit in the multiple protection switch units includes multiple protection switches. The protection switch unit is adapted to correspondingly connect one photovoltaic string unit among the plurality of photovoltaic string units to one power conversion unit among the plurality of power conversion units to form at least two photovoltaic string branches. The photovoltaic string branches The circuit is suitable for connecting one photovoltaic string or two photovoltaic strings connected in parallel. In the case where there are co-positive or co-negative power conversion units in multiple power conversion units, the co-positive or co-negative power conversion units are When the corresponding protection switch unit is connected to the corresponding photovoltaic string unit, the protection switch is shared, so that when the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, at least three protection switches are used to connect the corresponding photovoltaic strings. separated in between.

According to the inverter of the photovoltaic power generation system according to the embodiment of the present invention, since the photovoltaic string branch is connected to one photovoltaic string or two parallel photovoltaic strings, the protection switch unit corresponding to the common positive or common negative power conversion unit When connecting corresponding photovoltaic string units, the protection switches are shared, so that when the protection switch units corresponding to the common positive or common negative power conversion units are disconnected, at least three protection switches are used to separate the corresponding photovoltaic strings. Therefore, It is possible to reduce the number of protection switches without increasing the withstand voltage level of the protection switches, thereby reducing the cost and volume of the protection switch unit.

According to an embodiment of the present invention, each protection switch unit includes at least two positive connection terminals and at least two negative connection terminals, and each positive connection terminal is suitable for at most one photovoltaic string unit corresponding to one power conversion unit. Two photovoltaic strings are connected, and each negative connection end is suitable to be connected to at most two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit. In this way, the safety of the photovoltaic string can be improved.

According to an embodiment of the present invention, in the protection switch unit corresponding to the commonly negative power conversion unit, at least one negative connection end is suitable for connecting photovoltaic strings in different photovoltaic string units, so that the commonly negative power conversion unit The corresponding protection switch unit shares the protection switch when connecting the corresponding photovoltaic string unit. In this way, for common-negative power conversion units, by sharing protection switches, the number of protection switches can be reduced, thereby reducing the cost and volume of the protection switch unit.

According to an embodiment of the present invention, when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, one of at least two negative connection terminals is adapted to connect the first power conversion unit. Two parallel photovoltaic strings corresponding to the conversion unit and one photovoltaic string corresponding to the second power conversion unit; or at least one of the two negative connection terminals is suitable for connecting the two parallel connection terminals corresponding to the first power conversion unit photovoltaic strings and two parallel photovoltaic strings corresponding to the second power conversion unit; or at least one of the two negative connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and the second A photovoltaic string corresponding to the power conversion unit. In this way, for common-negative power conversion units, multiple methods can be used to realize the sharing of at least one protection switch.

According to an embodiment of the present invention, when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, one of at least two negative connection terminals is adapted to connect the first power conversion unit. A photovoltaic group string corresponding to the conversion unit and a photovoltaic group string corresponding to the second power conversion unit, and at least the other negative connection end of the two negative connection terminals is suitable for connecting two parallel photovoltaic groups corresponding to the first power conversion unit Two parallel photovoltaic strings corresponding to the string and the second power conversion unit; or at least one of the two negative connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and the second power conversion unit Corresponding to one photovoltaic string, at least the other negative connection terminal among the two negative connection terminals is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit; Or at least one of the two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit, and at least two negative connection terminals are The other negative connection terminal among the connection terminals is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. In this way, for a common-negative power conversion unit, a variety of methods can be used to realize the sharing of at least two protection switches.

According to an embodiment of the present invention, when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, if there are more than three negative connection terminals, among the more than three negative connection terminals, The first negative connection terminal is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. The second negative connection terminal among the three or more negative connection terminals is The connection terminal is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. The third negative connection terminal among the three or more negative connection terminals is suitable for connecting the third negative connection terminal. One photovoltaic string corresponding to one power conversion unit and one photovoltaic string corresponding to the second power conversion unit. In this way, for a common-negative power conversion unit, at least three protection switches can be shared.

According to an embodiment of the present invention, in the protection switch unit corresponding to the common positive power conversion unit, at least one positive connection end is suitable for connecting photovoltaic strings in different photovoltaic string units, so that the common positive power conversion unit The corresponding protection switch unit shares the protection switch when connecting the corresponding photovoltaic string unit. In this way, for common-positive power conversion units, by sharing protection switches, the number of protection switches can be reduced, thereby reducing the cost and volume of the protection switch unit.

According to an embodiment of the present invention, when the co-positive power conversion unit includes a first power conversion unit and a second power conversion unit, one of at least two positive connection terminals is adapted to connect the first power Two parallel photovoltaic strings corresponding to the conversion unit and one photovoltaic string corresponding to the second power conversion unit; or at least one of the two positive connection terminals is suitable for connecting the two parallel connection terminals corresponding to the first power conversion unit photovoltaic strings and two parallel photovoltaic strings corresponding to the second power conversion unit; or at least one of the two positive connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and the second A photovoltaic string corresponding to the power conversion unit. In this way, for common-positive power conversion units, multiple ways can be used to realize the sharing of at least one protection switch.

According to an embodiment of the present invention, when the co-positive power conversion unit includes a first power conversion unit and a second power conversion unit, one of at least two positive connection terminals is adapted to connect the first power A photovoltaic group string corresponding to the conversion unit and a photovoltaic group string corresponding to the second power conversion unit, and at least the other positive connection end of the two positive connection terminals is suitable for connecting two parallel photovoltaic groups corresponding to the first power conversion unit. Two parallel photovoltaic strings corresponding to the string and the second power conversion unit; or at least one of the two positive connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and the second power conversion unit Corresponding to one photovoltaic string, at least the other one of the two positive connection terminals is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit; Or at least one of the two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit, and at least two positive connection terminals are The other positive connection end among the connection ends is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. In this way, for the common-positive power conversion unit, a variety of methods can be used to realize the sharing of at least two protection switches.

According to an embodiment of the present invention, when the co-positive power conversion unit includes a first power conversion unit and a second power conversion unit, if there are more than three positive connection terminals, among the more than three positive connection terminals, The first positive connection terminal is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. The second positive connection terminal among the three or more positive connection terminals is The connection terminal is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. The third positive connection terminal among the three or more positive connection terminals is suitable for connecting the third positive connection terminal. One photovoltaic string corresponding to one power conversion unit and one photovoltaic string corresponding to the second power conversion unit. In this way, for a common positive power conversion unit, at least three protection switches can be shared.

According to an embodiment of the present invention, when there are at least three commonly negative power conversion units, at least one negative connection end is suitable for connecting the photovoltaic strings in the photovoltaic string unit corresponding to each common negative power conversion unit. , so that the protection switch units corresponding to at least three commonly negative power conversion units share the same protection switch when connecting the corresponding photovoltaic string units. In this way, for a common-negative power conversion unit, the number of protection switches can be reduced, thereby reducing the cost and volume of the protection switch unit.

According to an embodiment of the present invention, the negative connection terminal corresponding to the same protection switch is suitable for connecting: one photovoltaic string corresponding to each common negative power conversion unit; or two corresponding to each common negative power conversion unit. Parallel-connected photovoltaic strings; or at least one photovoltaic string corresponding to a common negative power conversion unit, and two parallel-connected photovoltaic strings corresponding to at least one common negative power conversion unit. In this way, for the commonly negative power conversion units, various methods can be used to realize that the protection switch units corresponding to at least three commonly negative power conversion units share the same protection switch when connecting the corresponding photovoltaic string units.

According to an embodiment of the present invention, when there are at least three common-positive power conversion units, at least one positive connection end is suitable for connecting the photovoltaic strings in the photovoltaic string unit corresponding to each common-positive power conversion unit. , so that the protection switch units corresponding to at least three common positive power conversion units share the same protection switch when connecting the corresponding photovoltaic string units. In this way, for the common-positive power conversion unit, the number of protection switches can be reduced, thereby reducing the cost and volume of the protection switch unit.

According to an embodiment of the present invention, the positive connection end corresponding to the same protection switch is suitable for connecting to one photovoltaic string corresponding to each common-positive power conversion unit; or two corresponding to each common-positive power conversion unit. Parallel-connected photovoltaic strings; or one photovoltaic string corresponding to at least one common-positive power conversion unit, and two parallel-connected photovoltaic strings corresponding to at least one common-positive power conversion unit. In this way, for common-positive power conversion units, various methods can be used to realize that the protection switch units corresponding to at least three common-positive power conversion units share the same protection switch when connecting corresponding photovoltaic string units.

According to an embodiment of the present invention, when there are at least three positive or negative power conversion units, at least one power conversion unit shares at least one protection switch in the corresponding protection switch unit with other power conversion units. In this way, by sharing the protection switches, the number of protection switches can be reduced, thereby reducing the cost and volume of the protection switch unit.

According to an embodiment of the present invention, when the common positive or common negative power conversion unit includes a first power conversion unit, a second power conversion unit and a third power conversion unit, the protection switch unit corresponding to the first power conversion unit includes At least two positive connection terminals and at least two negative connection terminals, each positive connection terminal is adapted to be connected to at most two photovoltaic strings in the photovoltaic string unit corresponding to the first power conversion unit, and each negative connection terminal is suitable for At most two photovoltaic strings in the photovoltaic string unit corresponding to the first power conversion unit are connected, wherein if the first power conversion unit, the second power conversion unit and the third power conversion unit are both negative, then at least two The negative connection end is respectively connected to the photovoltaic string unit corresponding to the second power conversion unit and the photovoltaic string unit corresponding to the third power conversion unit; if the first power conversion unit, the second power conversion unit and the third power conversion unit are both positive, Then, the photovoltaic string unit corresponding to the second power conversion unit and the photovoltaic string unit corresponding to the third power conversion unit are respectively connected through at least two positive connection terminals. In this way, it is possible to realize that at least one power conversion unit and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

According to an embodiment of the present invention, when the first power conversion unit, the second power conversion unit and the third power conversion unit are all negative, one of the at least two negative connection terminals is suitable for connecting to the second power conversion unit. For the two parallel photovoltaic strings corresponding to the power conversion unit, at least the other negative connection terminal of the two negative connection terminals is suitable for connecting to a photovoltaic string corresponding to the third power conversion unit; or at least one of the two negative connection terminals One negative connection terminal is suitable for connecting two parallel photovoltaic strings corresponding to the second power conversion unit, and the other negative connection terminal of at least two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the third power conversion unit. string; or at least one of the two negative connection terminals is suitable for connecting to a photovoltaic string corresponding to the second power conversion unit, and at least the other of the two negative connection terminals is suitable for connecting to the third power A photovoltaic string corresponding to the conversion unit. In this way, it is possible to realize that at least one power conversion unit and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

According to an embodiment of the present invention, when the first power conversion unit, the second power conversion unit and the third power conversion unit are both positive, one of the at least two positive connection terminals is suitable for connecting to the second power conversion unit. For the two parallel photovoltaic strings corresponding to the power conversion unit, at least the other positive connection terminal of the two positive connection terminals is suitable for connecting to a photovoltaic string corresponding to the third power conversion unit; or at least one of the two positive connection terminals One positive connection terminal is suitable for connecting two parallel photovoltaic strings corresponding to the second power conversion unit, and the other positive connection terminal of at least two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the third power conversion unit. string; or at least one of the two positive connection terminals is suitable for connecting to a photovoltaic string corresponding to the second power conversion unit, and at least the other of the two positive connection terminals is suitable for connecting to the third power A photovoltaic string corresponding to the conversion unit. In this way, it is possible to realize that at least one power conversion unit and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

According to an embodiment of the present invention, when there are at least three power conversion units that are both positive or negative in common, any two of the power conversion units in the at least three power conversion units that are positive in common or negative in common have a negative impact on the corresponding protection switch unit. At least one protection switch must be shared. In this way, by sharing the protection switches, the number of protection switches can be reduced, thereby reducing the cost and volume of the protection switch unit.

According to an embodiment of the present invention, when the commonly positive or commonly negative power conversion unit includes a first power conversion unit, a second power conversion unit and a third power conversion unit, the first power conversion unit and the second power conversion unit At least one protection switch in the corresponding protection switch unit is shared. The first power conversion unit and the third power conversion unit share at least one protection switch in the corresponding protection switch unit. The second power conversion unit and the third power conversion unit At least one protective switch in the corresponding protective switch unit is shared. In this way, any two power conversion units can share at least one protection switch in the corresponding protection switch unit.

According to an embodiment of the present invention, multiple protection switches in each protection switch unit are configured as multi-pole linkage switches.

According to an embodiment of the present invention, each power conversion unit includes a DC-DC converter, wherein when the negative terminals of any two DC-DC converters are connected together, the two power conversion units are collectively negative; or When the positive terminals of any two DC-DC converters are connected together, the two power conversion units are both positive. In this way, the power conversion units can be collectively positive or negative.

According to an embodiment of the present invention, when there is a reverse-connection fault branch in the photovoltaic power generation system, when the common positive or common negative power conversion unit disconnects the corresponding protection switch unit based on the reverse-connection fault branch, at least three The protection switch bears twice the PV string voltage. In this way, protection switches with lower voltage levels can be used for disconnection, thereby reducing the number of protection switches without increasing the withstand voltage level of the protection switches, thereby reducing the cost and volume of the protection switch unit.

In the second aspect, embodiments of the present utility model provide a fault protection device for a photovoltaic power generation system. The photovoltaic power generation system also includes a plurality of photovoltaic string units and a plurality of power conversion units, wherein, among the plurality of photovoltaic string units, Each photovoltaic string unit includes at least N photovoltaic strings, where N is an integer greater than or equal to 3. The fault protection device includes: multiple protection switch units, and each protection switch unit among the multiple protection switch units includes multiple protection switches. , each protection switch unit is adapted to connect one photovoltaic string unit among the plurality of photovoltaic string units to one power conversion unit among the plurality of power conversion units, so as to form at least two photovoltaic string branches. The photovoltaic group The string branch is suitable for connecting one photovoltaic string or two parallel photovoltaic strings. In the case where there are common positive or common negative power conversion units in multiple power conversion units, the common positive or common negative power conversion The protection switch units corresponding to the units share the protection switches when connecting the corresponding photovoltaic string units, so that when the protection switch units corresponding to the common positive or common negative power conversion units are disconnected, at least three protection switches are used to protect the corresponding photovoltaic groups. Split between strings.

According to the fault protection device of the photovoltaic power generation system according to the embodiment of the present invention, since the photovoltaic string branch is connected to one photovoltaic string or two parallel photovoltaic strings, the protection switch unit corresponding to the common positive or common negative power conversion unit When connecting corresponding photovoltaic string units, the protection switches are shared, so that when the protection switch units corresponding to the common positive or common negative power conversion units are disconnected, at least three protection switches are used to separate the corresponding photovoltaic strings. Therefore, It is possible to reduce the number of protection switches without increasing the withstand voltage level of the protection switches, thereby reducing the cost and volume of the protection switch unit.

In a third aspect, embodiments of the present invention provide a combiner box for a photovoltaic power generation system, including the aforementioned fault protection device. The fault protection device is configured to control multiple power conversion units when a fault occurs in the photovoltaic power generation system. The connections between multiple photovoltaic string units are fully or partially disconnected, so that when the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, at least three protection switches are used to protect the corresponding photovoltaic string units. Split between strings.

According to the combiner box of the photovoltaic power generation system according to the embodiment of the present invention, based on the aforementioned fault protection device, the number of protection switches can be reduced without increasing the voltage resistance level of the protection switches, thereby reducing the cost and volume of the protection switch unit. .

In the fourth aspect, embodiments of the present utility model propose a photovoltaic power generation system, including a plurality of photovoltaic string units. Each photovoltaic string unit in the plurality of photovoltaic string units includes at least N photovoltaic strings, where N is An integer greater than or equal to 3, the photovoltaic power generation system also includes: the aforementioned inverter; or the aforementioned fault protection device; or the aforementioned combiner box.

According to the photovoltaic power generation system according to the embodiment of the present invention, based on the aforementioned fault protection device, combiner box or inverter, the number of protection switches can be reduced without increasing the withstand voltage level of the protection switches, thereby reducing the number of protection switch units. cost and volume.

Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of the drawings

Figure 1 is a schematic structural diagram of a photovoltaic power generation system in related technologies;

Figure 2 shows the first connection method between a fault isolation circuit and multiple photovoltaic strings in the related art;

Figures 3a-3b show the second connection method between a fault isolation circuit and multiple photovoltaic strings in the related art;

Figures 4a-4c are schematic diagrams of protection switch units corresponding to two common negative power conversion units connected to photovoltaic string units according to some embodiments of the present invention;

Figures 5a-5c are schematic diagrams of two common positive power conversion units corresponding to the protection switch unit connected to the photovoltaic string unit according to some embodiments of the present invention;

Figures 6a-6g are schematic diagrams of the protection switch units corresponding to two common negative power conversion units connected to the photovoltaic string unit according to other embodiments of the present invention;

Figures 7a-7g are schematic diagrams of protection switch units corresponding to two common positive power conversion units connected to photovoltaic string units according to other embodiments of the present invention;

Figures 8a-8d are schematic diagrams of protection switch units corresponding to three common negative power conversion units connected to photovoltaic string units according to some embodiments of the present invention;

Figures 9a-9d are schematic diagrams of protection switch units corresponding to three common positive power conversion units connected to photovoltaic string units according to some embodiments of the present invention;

Figures 10a-10c are schematic diagrams of protection switch units corresponding to three common negative power conversion units connected to photovoltaic string units according to other embodiments of the present invention;

Figures 11a-11c are schematic diagrams of protection switch units corresponding to three common positive power conversion units connected to photovoltaic string units according to other embodiments of the present invention;

Figure 12 is a schematic diagram of the protection switch unit corresponding to three common negative power conversion units connected to the photovoltaic string unit according to yet another embodiment of the present invention;

Figure 13 is a schematic diagram of a fault protection device of a photovoltaic power generation system according to an embodiment of the present invention;

Figure 14 is a schematic diagram of a combiner box according to an embodiment of the present invention;

Figure 15 is a schematic diagram of a photovoltaic power generation system according to an embodiment of the present invention.

Detailed ways

The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the drawings, in which the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the drawings are exemplary and intended to explain the present invention, but should not be understood as limiting the present invention.

Referring to Figure 1, the photovoltaic power generation system includes multiple photovoltaic strings, multiple fault isolation circuits, multiple DC-DC converters and DC-AC converters. Each fault isolation circuit is connected to N photovoltaic strings PV1 and PV2. ,..., PVN, N photovoltaic strings are connected to the DC-DC converter through the fault isolation circuit, so that the generated power is provided to the DC-DC converter through the fault isolation circuit, and then passed to the DC-DC converter through the DC-DC converter. DC-AC converter. Among them, DC refers to direct current, AC refers to alternating current, DC-DC converter refers to DC-DC converter, and DC-AC converter refers to DC-AC converter.

The fault isolation circuit uses a DC switch with a breaking function. The DC switch can control the breaking manually or through the internal control part of the system. When a fault occurs in the photovoltaic power generation system, such as a short circuit or reverse connection in the photovoltaic string, a short circuit fault in the DC-DC converter, a short circuit fault in the DC-AC converter, etc., the DC can be controlled manually or automatically by the control unit. The switch is opened to isolate the photovoltaic string from the DC-DC converter and DC-AC converter.

In related technologies, there are two main ways of connecting a fault isolation circuit to multiple photovoltaic strings. However, both methods will cause the fault isolation circuit to have high costs.

The following description takes two DC-DC converters, two fault isolation circuits, and five photovoltaic strings connected to each fault isolation circuit as an example.

Exemplarily, Figure 2 shows a first connection method between a fault isolation circuit and multiple photovoltaic strings.

Referring to Figure 2, the fault isolation circuit 1 includes DC switches K1, K2,..., K6, and the fault isolation circuit 2 includes DC switches K7, K8,..., K12, where the DC switch K1 is connected to the positive electrode of the photovoltaic string PV1 PV1+ is connected, DC switch K2 is connected to the positive electrode PV2+ of photovoltaic string PV2 and the positive electrode PV3+ of photovoltaic string PV3, DC switch K3 is connected to the positive electrode PV4+ of photovoltaic string PV4 and the positive electrode PV5+ of photovoltaic string PV5,..., etc. etc., as shown in Figure 2 and will not be described in detail here.

Among them, when a photovoltaic string has a reverse connection fault, the DC switch needs to be disconnected to protect the photovoltaic string. When the DC switch is disconnected, the photovoltaic string that has a reverse connection fault and the photovoltaic string that has not experienced a reverse connection fault are composed of In the circuit, the number of DC switches is 0 or 4, that is, 4 DC switches are connected in series to break twice the voltage of the photovoltaic string. For example, when a reverse connection fault occurs in photovoltaic string PV1, in the circuit composed of photovoltaic string PV1 and photovoltaic string PV2, DC switches K2, K1, K6 and K5 will disconnect photovoltaic string PV1 and photovoltaic string PV2. voltage.

Figures 3a and 3b show a second connection method between a fault isolation circuit and multiple photovoltaic strings.

Referring to Figure 3a, fault isolation circuit 1 includes DC switches K1, K2, K3, K4, fault isolation circuit 2 includes DC switches K5, K6, K7, K8, specifically connected to photovoltaic strings PV1, PV2,..., PV10 The relationship is shown in Figure 3a and will not be described in detail here.

Among them, when a photovoltaic string has a reverse connection fault, the DC switch needs to be disconnected to protect the photovoltaic string. When the DC switch is disconnected, the photovoltaic string that has a reverse connection fault and the photovoltaic string that has not experienced a reverse connection fault are composed of In the circuit, the number of DC switches is 0 or 2, that is, two DC switches are connected in series to break twice the voltage of the photovoltaic string. For example, when a reverse connection fault occurs in photovoltaic string PV1, in the circuit composed of photovoltaic string PV1 and photovoltaic string PV2, DC switches K4 and K3 will interrupt the voltage of photovoltaic string PV1 and photovoltaic string PV2.

Referring to Figure 3b, the fault isolation circuit 1 includes DC switches K1, K2,..., K5, and the fault isolation circuit 2 includes DC switches K6, K7,..., K10, specifically related to the photovoltaic strings PV1, PV2,... , The connection relationship of PV10 is shown in Figure 3b and will not be described in detail here.

Among them, when a photovoltaic string has a reverse connection fault, the DC switch needs to be disconnected to protect the photovoltaic string. When the DC switch is disconnected, the photovoltaic string that has a reverse connection fault and the photovoltaic string that has not experienced a reverse connection fault are composed of In the circuit, the number of DC switches is 0 or 2, that is, two DC switches are connected in series to break twice the voltage of the photovoltaic string. For example, when a reverse connection fault occurs in photovoltaic string PV1, in the circuit composed of photovoltaic string PV1 and photovoltaic string PV2, DC switches K5 and K4 will break the voltage of photovoltaic string PV1 and photovoltaic string PV2.

It should be noted that according to the breaking voltage of the DC switch, the DC switch can be divided into a high-voltage DC switch and a low-voltage DC switch. Among them, two or less DC switches in series can break twice the voltage of the photovoltaic string. A DC switch is called a high-voltage DC switch; a DC switch that requires three or more DC switches in series and can break twice the voltage of the photovoltaic string is called a low-voltage DC switch.

On this basis, for the first connection method between the fault isolation circuit and multiple photovoltaic strings shown in Figure 2, although the fault isolation circuit can use a low-cost low-voltage DC switch to interrupt twice the voltage of the photovoltaic strings, However, each low-voltage DC switch can connect up to two photovoltaic strings, so 12 low-voltage DC switches need to be used. The larger number of low-voltage DC switches results in a higher cost of fault isolation circuits.

Regarding the second connection method between the fault isolation circuit and multiple photovoltaic strings shown in Figure 3a and Figure 3b, although the number of DC switches can be reduced by increasing the number of photovoltaic strings connected by the DC switch, as shown in Figure 3a The DC switch K1 connects 5 photovoltaic strings. The DC switch K1 shown in Figure 3b connects 3 photovoltaic strings. That is, one DC switch can connect three or more photovoltaic strings to reduce the number of DC switches. However, At this time, a high-cost high-voltage DC switch is required, resulting in a higher cost of the fault isolation circuit.

Based on the above analysis, the two connection methods of fault isolation circuits and multiple photovoltaic strings in related technologies will cause the fault isolation circuit to have high costs.

Based on this, embodiments of the present invention provide a photovoltaic power generation system and its inverter, fault protection device and combiner box, which can be used without increasing the withstand voltage level of the protection switch, even if a low-voltage protection switch is used. This reduces the number of protection switches, thereby reducing the cost and volume of the protection switch unit.

In order to enable those skilled in the art to better understand the technical solutions of the present utility model, the technical solutions in the embodiments of the present utility model are clearly described below in conjunction with the drawings in the embodiments of the present utility model.

The photovoltaic power generation system provided by the embodiment of the present invention may include: multiple photovoltaic string units, each of the multiple photovoltaic string units includes at least N photovoltaic strings, where N is an integer greater than or equal to 3. The inverter may include: multiple power conversion units and multiple protection switch units, each of the multiple protection switch units includes multiple protection switches, and each protection switch unit is adapted to connect multiple photovoltaic string units. One photovoltaic string unit is connected to one of the plurality of power conversion units to form at least two photovoltaic string branches. The photovoltaic string branches are suitable for connecting one photovoltaic string or two parallel ones. Photovoltaic string. Among them, when there are common positive or common negative power conversion units in multiple power conversion units, the protection switch units corresponding to the common positive or common negative power conversion units share the protection switches when connecting the corresponding photovoltaic string units. , so that when the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, at least three protection switches are used to separate the corresponding photovoltaic strings.

It should be noted that each photovoltaic string unit in the multiple photovoltaic string units includes at least N photovoltaic strings, where N is an integer greater than or equal to 3, which refers to each photovoltaic string in the multiple photovoltaic string units. The unit includes at least 3 photovoltaic strings, and the number of photovoltaic strings in different photovoltaic string units can be the same or different. For example, in multiple photovoltaic string units, some photovoltaic string units include three photovoltaic strings, and Some PV string units include 4 PV strings; alternatively, all PV string units include 3 PV strings; etc. For example, referring to Figure 4a, the photovoltaic string unit 1 and the photovoltaic string unit 2 each include three photovoltaic strings. Among them, the photovoltaic string can be formed by multiple photovoltaic modules connected in series and parallel. For example, multiple photovoltaic modules are directly connected in series, or first connected in parallel and then connected in series to form a photovoltaic string. The number and parameters of the photovoltaic modules contained in the specific photovoltaic string are not limited here. .

The power conversion unit refers to the power that can convert the electricity generated by the photovoltaic string unit into the electricity required by the user. For example, the power conversion unit can convert one type of DC power emitted by the photovoltaic string unit into another type of DC power. The other type of DC power can be directly provided to the load, or can be provided after inversion through a DC-AC converter. Given the load, there are no specific restrictions here. For example, based on requirements, the power conversion unit may be but is not limited to a DC-DC converter.

The protection switch may be the aforementioned DC switch, and each protection switch unit includes multiple protection switches. For example, referring to Figure 4a, the protection switch unit 1 includes five protection switches K1, K2,..., K5. The protection switch unit 2Including five protection switches K6, K7,...,K10. Each protection switch unit is adapted to connect a photovoltaic string unit to a power conversion unit to form at least two photovoltaic string branches. For example, referring to Figure 4a, the protection switch unit 1 connects the photovoltaic string unit 1 The protection switch unit 2 connects the photovoltaic string unit 2 to the power conversion unit 2 correspondingly, and forms six photovoltaic string branches. Branch circuit (before the protection switch is shared).

Photovoltaic string branch refers to the branch corresponding to each protection switch, that is, one protection switch corresponds to one photovoltaic string branch. For example, referring to Figure 4a, protection switch K1 corresponds to one photovoltaic string branch, and protection switch K2 corresponds to A PV string branch, etc. The photovoltaic string branch is suitable for connecting one photovoltaic string or two photovoltaic strings connected in parallel. For example, for any protection switch unit, each of the at least two photovoltaic string branches formed is suitable for Connecting one photovoltaic string; alternatively, each of the at least two photovoltaic string branches formed is suitable for connecting two parallel photovoltaic strings; alternatively, the at least two photovoltaic string branches formed It includes: at least one photovoltaic string branch is suitable for connecting one photovoltaic string, and at least one photovoltaic string branch is suitable for connecting two parallel photovoltaic strings.

For example, referring to Figure 4a, the protection switch unit 1 is suitable for connecting the photovoltaic string unit 1 to the power conversion unit 1, and forming six photovoltaic string branches (before the protection switches are not shared). Among them, the photovoltaic string branch corresponding to the protection switch K1 is connected to the photovoltaic string PV1 in the photovoltaic string unit 1, and the photovoltaic string branch corresponding to the protection switch K2 is connected to the photovoltaic string PV2 in the photovoltaic string unit 1. The protection switch The photovoltaic string branch corresponding to K3 is connected to the photovoltaic string PV3 in the photovoltaic string unit 1, the photovoltaic string branch corresponding to the protection switch K4 is connected to the photovoltaic string PV3 in the photovoltaic string unit 1, and the photovoltaic string branch corresponding to the protection switch K5 is connected to the photovoltaic string branch K3. The string branch is connected to the photovoltaic string PV2 in the photovoltaic string unit 1. Before the protection switch is not shared, there is still a photovoltaic string branch corresponding to the protection switch connected to the photovoltaic string PV1 in the photovoltaic string unit 1. The protection switch unit 2 will not be described again here. In this example, each of the at least two photovoltaic string branches formed by each protection switch unit is adapted to connect one photovoltaic string in the corresponding photovoltaic string unit.

For example, referring to Figure 4b, the protection switch unit 1 is suitable for connecting the photovoltaic string unit 1 to the power conversion unit 1, and forming four photovoltaic string branches (before the protection switches are not shared). Among them, the photovoltaic string branch corresponding to the protection switch K1 is connected to the photovoltaic strings PV1 and PV2 in the photovoltaic string unit 1, and the photovoltaic string branch corresponding to the protection switch K2 is connected to the photovoltaic strings PV3 and PV2 in the photovoltaic string unit 1. PV4, the photovoltaic string branch corresponding to the protection switch K3 is connected to the photovoltaic strings PV3 and PV4 in the photovoltaic string unit 1, and the photovoltaic string branch corresponding to the protection switch K4 is connected to the photovoltaic strings PV1 and PV in the photovoltaic string unit 1. PV2. Regarding the protection switch unit 2, it should be noted that before the protection switches are shared, there is still a photovoltaic string branch corresponding to the protection switch connected to the photovoltaic strings PV7 and PV8 in the photovoltaic string unit 2. In this example, each of the at least two photovoltaic string branches formed by each protection switch unit is adapted to connect two photovoltaic strings in the corresponding photovoltaic string unit.

For example, referring to Figure 4c, the protection switch unit 1 is suitable for connecting the photovoltaic string unit 1 to the power conversion unit 1, and forming four photovoltaic string branches (before the protection switches are not shared). Among them, the photovoltaic string branch corresponding to the protection switch K1 is connected to the photovoltaic string PV1 in the photovoltaic string unit 1, and the photovoltaic string branch corresponding to the protection switch K2 is connected to the photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1. The photovoltaic string branch corresponding to the protection switch K3 is connected to the photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1. Before the protection switch is shared, there is still a photovoltaic string branch corresponding to the protection switch connected to the photovoltaic string unit 1. Medium photovoltaic string PV1. The protection switch unit 2 will not be described again here. In this example, among at least two photovoltaic string branches formed by each protection switch unit, the two photovoltaic string branches are suitable for connecting one photovoltaic string in the corresponding photovoltaic string unit, and the two photovoltaic string branches The circuit is suitable for connecting two photovoltaic strings in the corresponding photovoltaic string unit.

The existence of power conversion units that are commonly positive or commonly negative among multiple power conversion units means that some of the power conversion units among the multiple power conversion units are commonly positive or commonly negative, or that all power conversion units among the multiple power conversion units are commonly positive. Or share the responsibility. A co-positive power conversion unit means that the positive terminals of any multiple power conversion units are connected together, and these multiple power conversion units are co-positive; a co-negative power conversion unit means that the negative terminals of any multiple power conversion units are connected together. , these multiple power conversion units share the negative voltage.

Exemplarily, referring to Figures 4a-4c, the negative input terminal of the power conversion unit 1 is connected to the negative output terminal, the negative input terminal of the power conversion unit 2 is connected to the negative output terminal, and the negative output terminal of the power conversion unit 1 is connected to the power The negative output terminal of the conversion unit 2 is connected, for example, both are connected to the negative pole BUS- of the DC bus. At this time, the power conversion unit 1 and the power conversion unit 2 are both negative. Referring to Figure 5a-Figure 5c, the positive input terminal of the power conversion unit 1 is connected to the negative pole BUS- of the DC bus. The positive output terminal is connected, the positive input terminal of power conversion unit 2 is connected to the positive output terminal, and the positive output terminal of power conversion unit 1 is connected to the positive output terminal of power conversion unit 2. If both are connected to the negative pole BUS+ of the DC bus, this When the power conversion unit 1 and the power conversion unit 2 are both positive.

Further, the power conversion unit may include a DC-DC converter. When each power conversion unit includes a DC-DC converter, when the positive terminals of any two DC-DC converters are connected together, the two The power conversion units have a common positive value; when the negative terminals of any two DC-DC converters are connected together, the two power conversion units have a common negative value. For specific instructions, please refer to the foregoing examples and will not be described in detail here.

The protection switch units corresponding to the power conversion units that are both positive or negative in common are shared when connecting the corresponding photovoltaic string units. This means that at least one of the multiple protection switch units corresponding to the power conversion units that are both positive or negative in common exists. A protection switch is simultaneously connected to part of the photovoltaic strings of at least two photovoltaic string units of multiple photovoltaic string units corresponding to common positive or common negative power conversion units. By sharing the protection switches, the number of protection switches can be reduced, thereby reducing Cost and size of the protection switch unit.

For example, referring to Figure 4a, the power conversion unit 1 and the power conversion unit 2 share a negative voltage. When the protection switch unit 1 corresponding to the power conversion unit 1 is connected to the corresponding photovoltaic string unit 1, the protection switch K5 is shared. When the protection switch unit 2 corresponding to the power conversion unit 2 is connected to the corresponding photovoltaic string unit 2, the protection switch K6 is shared, that is, the protection switch K5 is connected to the photovoltaic string PV2 and the photovoltaic string unit in the photovoltaic string unit 1 at the same time. The photovoltaic string PV6 in 2, the protection switch K6 is connected to the photovoltaic string PV1 in the photovoltaic string unit 1 and the photovoltaic string PV5 in the photovoltaic string unit 2 at the same time. The protection switches K5 and K6 are connected by the photovoltaic string unit 1 and the photovoltaic string unit 2. Shared by string unit 2. And if the protection switches K5 and K6 are not shared, as mentioned above, then in the protection switch unit 1, a protection switch is needed to be connected to the negative electrode PV1- of the photovoltaic string PV1, and at the same time, in the protection switch unit 2, a protection switch is also needed. It is connected to the negative pole PV6- of the photovoltaic string PV6. Compared with sharing, there are two more protection switches. Therefore, the number of protection switches used can be reduced by sharing protection switches.

For example, referring to Figure 4b, the power conversion unit 1 and the power conversion unit 2 share a common negative, and the protection switch unit 1 corresponding to the power conversion unit 1 is connected to the corresponding photovoltaic string unit 1, and the protection switch corresponding to the power conversion unit 2 When unit 2 is connected to the corresponding photovoltaic string unit 2, the protection switch K4 is shared, that is, the protection switch K4 is simultaneously connected to the photovoltaic strings PV1 and PV2 in the photovoltaic string unit 1 and the photovoltaic string PV7 in the photovoltaic string unit 2. and PV8, protection switch K4 is shared by photovoltaic string unit 1 and photovoltaic string unit 2. And if the protection switch K4 is not shared, as mentioned above, then in the protection switch unit 2, a protection switch is also needed to be connected to the negative electrode PV7- of the photovoltaic string PV7 and the negative electrode PV8- of the photovoltaic string PV8. Compared with sharing, there are more A protection switch is provided, so the number of protection switches used can be reduced by sharing the protection switches.

For example, referring to Figure 4c, the power conversion unit 1 and the power conversion unit 2 share a negative voltage. When the protection switch unit 1 corresponding to the power conversion unit 1 is connected to the corresponding photovoltaic string unit 1, the protection switch K3 is shared. When the protection switch unit 2 corresponding to the power conversion unit 2 is connected to the corresponding photovoltaic string unit 2, the protection switch K4 is shared, that is, the protection switch K3 is connected to the photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic group at the same time. The photovoltaic string PV6 in string unit 2 and the protection switch K4 are connected to the photovoltaic string PV1 in the photovoltaic string unit 1 and the photovoltaic strings PV4 and PV5 in the photovoltaic string unit 2. The protection switches K3 and K4 are connected to the photovoltaic strings. Unit 1 and photovoltaic string unit 2 are shared. And if the protection switches K3 and K4 are not shared, as mentioned above, then in the protection switch unit 1, a protection switch is needed to be connected to the negative electrode PV1- of the photovoltaic string PV1, and at the same time, in the protection switch unit 2, a protection switch is also needed. It is connected to the negative pole PV6- of the photovoltaic string PV6. Compared with sharing, there are two more protection switches. Therefore, the number of protection switches used can be reduced by sharing protection switches.

It should be noted that for the sharing of protection switches when the power conversion units 1 and 2 are both positive, please refer to the relevant description of the power conversion units 1 and 2 when they are both negative, which will not be described in detail here.

When the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, the corresponding photovoltaic strings are disconnected through at least three protection switches. This means that when the photovoltaic power generation system fails, such as photovoltaic strings In the event of a reverse connection fault or short circuit fault, in the circuit composed of the failed photovoltaic string and the non-faulty photovoltaic string, at least three protective switches can interrupt twice the voltage of the photovoltaic string, so that it can continue to be used. Low cost low voltage protection switch. Among them, a reverse connection fault means that the positive and negative poles of the photovoltaic string are connected in reverse, and a short-circuit fault means that the positive and negative poles of the photovoltaic string are grounded at the same time. The disconnection of the protection switch unit means that all the protection switches in the protection switch unit are disconnected. For example, referring to Figure 4a, the disconnection of the protection switch unit 1 means that the protection switches K1, K2,..., K5 are all disconnected.

For example, referring to Figure 4a, assuming that a reverse connection fault occurs in the photovoltaic string PV1, in the circuit composed of the photovoltaic string PV1 and the photovoltaic string PV2, there will be four protection switches K2, K1, K6 and K5 to protect the photovoltaic string. PV1 and photovoltaic string PV2 are disconnected. Among them, the circuit composed of photovoltaic string PV1 and photovoltaic string PV2 is: the positive electrode PV2+ of photovoltaic string PV2→protection switch K2→protection switch K1→the positive electrode PV1+ of photovoltaic string PV1→the negative electrode PV1- of photovoltaic string PV1→protection Switch K6 → the negative pole BUS- of the DC bus → protection switch K5 → the negative pole PV2- of the photovoltaic string PV2.

For example, referring to Figure 4b, assuming that a reverse connection fault occurs in photovoltaic string PV7, in the circuit composed of photovoltaic string PV6 and photovoltaic string PV7, there will be four protection switches K6, K7, K4 and K5 to protect the photovoltaic string. PV6 and photovoltaic string PV7 are disconnected. Among them, the circuit composed of photovoltaic string PV6 and photovoltaic string PV7 is: the positive electrode PV6+ of photovoltaic string PV6→protection switch K6→protection switch K7→the positive electrode PV7+ of photovoltaic string PV7→the negative electrode PV7- of photovoltaic string PV7→protection Switch K4 → the negative pole BUS- of the DC bus → protection switch K5 → the negative pole PV6- of the photovoltaic string PV6.

It should be noted that other situations will not be described in detail here. In addition, the above descriptions take two power conversion units and two protection switch units as examples, but this cannot be regarded as a limitation on the present application. The examples mentioned below are included for convenience of explanation.

The following is a further analysis of how the inverter can reduce the number of protection switches and thus reduce the number of protection switch units without increasing the withstand voltage level of the protection switches, that is, while being able to continue to use low-cost protection switches. cost and volume. In order to be able to contrast with related technologies, the following description takes two power conversion units such as DC-DC converters, two protection switch units, and each protection switch unit connected to five photovoltaic strings as an example.

Referring to Figure 6a, DC-DC converter 1 and DC-DC converter 2 share a common negative, and the protection switch K5 and the protection switch K6 share the same. Since the protection switches K5 and K6 share the same, only 10 protection switches need to be used. Compared with For the 12 DC switches shown in Figure 2, the number of protection switches is reduced by two, thereby reducing the cost of the protection switch and thereby reducing the cost and volume of the protection switch unit. In this way, by sharing the protection switches, the cost and size of the protection switch unit can be reduced.

In addition, when a reverse connection fault occurs in any photovoltaic string, there will be 0 or 4 protection switch pairs in the circuit composed of the photovoltaic string with the reverse connection fault and the photovoltaic string without the reverse connection fault. The photovoltaic strings are separated from the photovoltaic strings that do not have reverse connection faults, so a low-cost low-voltage protection switch can be used. For example, when a reverse connection fault occurs in photovoltaic string PV1, in the circuit composed of photovoltaic string PV1 and photovoltaic string PV2, there will be protective switches K2, K1, K6 and K5 to perform protection on photovoltaic string PV1 and photovoltaic string PV2. Break; wait. In this way, when the protection switch unit corresponding to the common negative power conversion unit is disconnected, at least three protection switches are used to separate the corresponding photovoltaic strings, and low-cost low-voltage protection switches can continue to be used, while Figure 3a and In the situation shown in Figure 3b, a low-cost low-voltage protective switch cannot be used.

It should be noted that Figure 7a shows the situation where DC-DC converter 1 and DC-DC converter 2 are both positive. For specific analysis, please refer to the situation where DC-DC converter 1 and DC-DC converter 2 are both negative as shown in Figure 6a. The specific situation will not be repeated here.

Based on the above analysis, by sharing the protection switches and when the protection switch units corresponding to the common positive or common negative power conversion units are disconnected, at least three protection switches are used to separate the corresponding photovoltaic strings, so that they can continue to be used. In the case of low-cost protection switches, the number of protection switches is reduced, thereby reducing the cost and volume of the protection switch unit.

In some embodiments, each protection switch unit includes at least two positive connection terminals and at least two negative connection terminals, and each positive connection terminal is suitable for at most two photovoltaic string units corresponding to one power conversion unit. The strings are connected, and each negative connection end is suitable for being connected to at most two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit.

It should be noted that the positive connection end of the protection switch unit refers to the end connected to the positive electrode of the photovoltaic string, and the negative connection end of the protection switch unit refers to the end connected to the negative electrode of the photovoltaic string.

Before the protection switch is shared, each protection switch unit includes at least two positive connection terminals and at least two negative connection terminals, and each positive connection terminal and each negative connection terminal are suitable for the photovoltaic string corresponding to one power conversion unit. One or two photovoltaic strings in the unit are connected, so that when the protection switch unit is disconnected, at most two photovoltaic strings in the corresponding photovoltaic string unit are connected in parallel, so that one photovoltaic string can withstand at most one When a normal photovoltaic string outputs current, when a reverse connection fault or short circuit fault occurs in a photovoltaic string, at most one normal photovoltaic string will output current to it. At this time, the current is within the limit that the faulty photovoltaic string can withstand. within the range, thereby protecting the photovoltaic strings from damage.

For example, referring to Figure 4a, after the protective switch unit 1 is controlled to be turned off, each photovoltaic string in the photovoltaic string unit 1 is not connected in parallel.

For example, referring to Figure 4b, after the protective switch unit 1 is controlled to be disconnected, the photovoltaic strings PV1 and PV2 in the photovoltaic string unit 1 are connected in parallel, and the photovoltaic strings PV3 and PV4 are connected in parallel. Assume that the photovoltaic string PV1 is connected at this time. If a reverse connection fault occurs, the normal photovoltaic string PV2 will output current to the faulty photovoltaic string PV1. Since the current does not exceed the range that the photovoltaic string PV1 can withstand, the photovoltaic string PV1 will not be damaged.

For example, referring to Figure 4c, after the control protection switch unit 1 is disconnected, the photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 are connected in parallel. Assuming that a reverse connection fault occurs in the photovoltaic string PV2 at this time, then the normal photovoltaic The string PV3 will output current to the faulty photovoltaic string PV2. Since the current does not exceed the range that the photovoltaic string PV2 can withstand, the photovoltaic string PV2 will not be damaged.

For example, referring to Figure 6a, before the protection switches K5 and K6 are not shared, the protection switch unit 1 includes three positive connection terminals and three negative connection terminals (before they are not shared, one negative connection terminal is also required to be connected to the photovoltaic string PV1 The negative electrode PV1- is connected), the protection switch unit 2 includes three positive connecting terminals and three negative connecting terminals (before sharing, one negative connecting terminal needs to be connected to the negative electrode PV10- of the photovoltaic string PV10), and some positive connections The negative terminal is connected to the positive electrode of one photovoltaic string, the negative terminal is connected to the positive terminal of two photovoltaic strings, the negative terminal is connected to the negative terminal of one photovoltaic string, and the negative terminal is connected to the negative terminal of two photovoltaic strings. Based on this connection relationship, after the protection switch unit 1 and the protection switch unit 2 are disconnected, the photovoltaic strings PV2 and PV3 are connected in parallel, the photovoltaic strings PV4 and PV5 are connected in parallel, the photovoltaic strings PV6 and PV7 are connected in parallel, and the photovoltaic strings are connected in parallel. PV8 and PV9 are connected in parallel. Since each group has at most two photovoltaic strings connected in parallel, when a reverse connection fault occurs in any photovoltaic string, only the current of one normal photovoltaic string flows into the failed photovoltaic string. It does not exceed the range that the failed photovoltaic string can withstand, so the failed photovoltaic string will not be damaged, which improves the safety of the photovoltaic string.

In this way, each positive connection end is suitable to be connected to at most two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit, and each negative connection end is suitable to be connected to one photovoltaic string unit corresponding to one power conversion unit. At most two photovoltaic strings are connected, which can improve the safety of the photovoltaic strings.

In some embodiments, in the protection switch unit corresponding to the commonly negative power conversion unit, at least one negative connection terminal is adapted to connect the photovoltaic strings in different photovoltaic string units, so that the common negative power conversion unit corresponds to The protection switch unit shares the protection switch when connecting the corresponding photovoltaic string unit.

That is to say, for a power conversion unit with a common negative, the negative connection end of the protection switch unit can be connected to the photovoltaic strings in different photovoltaic string units to realize the sharing of protection switches and reduce the number of protection switches. During connection, one or more negative connection terminals may be connected to photovoltaic strings in different photovoltaic string units to realize the sharing of one or more protection switches.

For example, referring to Figure 6a, the power conversion unit 1 includes a DC-DC converter 1, the power conversion unit 2 includes a DC-DC converter 2, and the DC-DC converter 1 and the DC-DC converter 2 are in common negative, that is, The power conversion unit 1 and the power conversion unit 2 have a common negative voltage, and the protection switch units corresponding to the common negative power conversion unit 1 and the power conversion unit 2 are the protection switch unit 1 and the protection switch unit 2. Among them, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic string PV10 in the photovoltaic string unit 2; In the protection switch unit 2, the negative connection end of the protection switch unit 2 corresponding to the protection switch K6 is connected to the photovoltaic strings PV8 and PV9 in the photovoltaic string unit 2 and the photovoltaic string PV1 in the photovoltaic string unit 1. Protection switches K5 and K6 are shared by photovoltaic string unit 1 and photovoltaic string unit 2. Compared with not sharing, there are two fewer protection switches and the number of protection switches is reduced.

For example, referring to Figure 6b, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic string unit 2. The photovoltaic string PV10, the negative connection end of the protection switch unit 1 corresponding to the protection switch K4 is connected to the photovoltaic strings PV4 and PV5 in the photovoltaic string unit 1 and the photovoltaic strings PV6 and PV7 in the photovoltaic string unit 2; in In the protection switch unit 2, the negative connection end of the protection switch unit 2 corresponding to the protection switch K6 is connected to the photovoltaic strings PV8 and PV9 in the photovoltaic string unit 2 and the photovoltaic string PV1 in the photovoltaic string unit 1. Protection switches K4, K5 and K6 are shared by photovoltaic string unit 1 and photovoltaic string unit 2. Compared with not sharing, there are three fewer protection switches and the number of protection switches is reduced. Compared with the sharing in Figure 6a, it is reduced. A protection switch is installed, further reducing the number of protection switches.

In this way, for a common negative power conversion unit, the photovoltaic strings in different photovoltaic string units can be connected through one or more negative connection terminals of the corresponding protection switch unit, which can reduce the number of protection switches and thereby reduce the load of the protection switch unit. Cost and volume.

In some embodiments, when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, one of the at least two negative connection terminals is adapted to connect two corresponding terminals of the first power conversion unit. A parallel photovoltaic string and a photovoltaic string corresponding to the second power conversion unit; or at least one of the two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and Two parallel photovoltaic strings corresponding to the second power conversion unit; or at least one of the two negative connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a corresponding photovoltaic string of the second power conversion unit. A photovoltaic string.

Specifically, each protection switch unit includes at least two negative connection terminals, and each negative connection terminal is suitable for being connected to one or two photovoltaic strings in the photovoltaic string unit corresponding to a power conversion unit. Therefore, for a common negative connection The power conversion unit can be connected to the same power conversion unit through one or two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit and one or two photovoltaic strings in the corresponding photovoltaic string unit of another power conversion unit. A negative connection terminal is used to realize the sharing of the protection switches corresponding to the negative connection terminal, thereby realizing the sharing of at least one protection switch, wherein there are multiple ways of sharing the protection switches.

For example, referring to Figure 6a, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV2 and PV3 corresponding to the power conversion unit 1 and the corresponding power conversion unit 2. A photovoltaic string PV10. In this way, based on a negative connection terminal connecting two parallel photovoltaic strings corresponding to one power conversion unit and one photovoltaic string corresponding to another power conversion unit, the sharing of the protection switch K5 is realized.

For example, referring to Figure 6b, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K4 is connected to the two parallel photovoltaic strings PV4 and PV5 corresponding to the power conversion unit 1 and the corresponding power conversion unit 2. Two parallel photovoltaic strings PV6 and PV7. In this way, based on a negative connection terminal connecting two parallel photovoltaic strings corresponding to one power conversion unit and two parallel photovoltaic strings corresponding to another power conversion unit, the sharing of the protection switch K4 is realized.

For example, referring to Figure 6c, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K7 is connected to a photovoltaic string PV2 corresponding to the power conversion unit 1 and a photovoltaic string corresponding to the power conversion unit 2. PV10. In this way, based on a negative connection terminal connecting a photovoltaic string corresponding to one power conversion unit and a photovoltaic string corresponding to another power conversion unit, the sharing of the protection switch K7 is realized.

In this way, for common-negative power conversion units, multiple methods can be used to realize the sharing of at least one protection switch.

In some embodiments, when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, one of the at least two negative connection terminals is adapted to be connected to a corresponding one of the first power conversion unit. One photovoltaic string corresponding to the photovoltaic string and the second power conversion unit, and at least the other negative connection terminal of the two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and the second power conversion unit. Two parallel photovoltaic strings corresponding to the conversion unit; or at least one of the two negative connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic group corresponding to the second power conversion unit string, at least the other of the two negative connection terminals is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit; or at least two negative connection terminals. One of the negative connection terminals is suitable for connecting the two parallel photovoltaic strings corresponding to the first power conversion unit and the two parallel photovoltaic strings corresponding to the second power conversion unit, and at least the other of the two negative connection terminals is One negative connection end is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit.

Specifically, each protection switch unit includes at least two negative connection terminals, and each negative connection terminal is suitable for being connected to one or two photovoltaic strings in the photovoltaic string unit corresponding to a power conversion unit. Therefore, for a common negative connection The power conversion unit can be connected to the same power conversion unit through one or two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit and one or two photovoltaic strings in the corresponding photovoltaic string unit of another power conversion unit. A negative connection terminal is used to realize the sharing of the protection switches corresponding to the negative connection terminal, thereby realizing the sharing of at least two protection switches. There are many ways of sharing the protection switches.

For example, referring to Figure 6d, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K7 is connected to a photovoltaic string PV2 corresponding to the power conversion unit 1 and a photovoltaic string corresponding to the power conversion unit 2. PV10, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV4 and PV5 corresponding to the power conversion unit 1 and the two parallel photovoltaic strings PV6 and PV7 corresponding to the power conversion unit 2. . In this way, based on the fact that one negative connection terminal is connected to a photovoltaic string corresponding to a power conversion unit and a photovoltaic string corresponding to another power conversion unit, and the other negative connection terminal is connected to two parallel photovoltaic groups corresponding to a power conversion unit The two parallel photovoltaic strings corresponding to the string and another power conversion unit realize the sharing of protection switches K7 and K5.

For example, referring to Figure 6e, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K7 is connected to a photovoltaic string PV2 corresponding to the power conversion unit 1 and a photovoltaic string corresponding to the power conversion unit 2. PV10, the negative connection end of the protection switch unit 1 corresponding to the protection switch K6 is connected to a photovoltaic string PV3 corresponding to the power conversion unit 1 and two parallel photovoltaic strings PV6 and PV7 corresponding to the power conversion unit 2. In this way, based on a negative connection terminal connecting a photovoltaic string corresponding to a power conversion unit and a photovoltaic string corresponding to another power conversion unit, and the other negative connection terminal connecting a photovoltaic string corresponding to a power conversion unit and another Two parallel photovoltaic strings corresponding to one power conversion unit realize the sharing of protection switches K7 and K6.

For example, referring to Figure 6f, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K4 is connected to the two parallel photovoltaic strings PV4 and PV5 corresponding to the power conversion unit 1 and the corresponding power conversion unit 2. Two parallel photovoltaic strings PV6 and PV7, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to a photovoltaic string PV1 corresponding to the power conversion unit 1 and two parallel photovoltaics corresponding to the power conversion unit 2 Strings PV8 and PV9. In this way, based on the fact that one negative connection terminal is connected to two parallel photovoltaic strings corresponding to one power conversion unit and two parallel photovoltaic strings corresponding to another power conversion unit, and the other negative connection terminal is connected to one corresponding power conversion unit. One photovoltaic string and two parallel photovoltaic strings corresponding to another power conversion unit realize the sharing of protection switches K4 and K5.

In this way, for a common-negative power conversion unit, a variety of methods can be used to realize the sharing of at least two protection switches.

In some embodiments, when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, if there are more than three negative connection terminals, the first negative connection terminal among the more than three negative connection terminals is The connection terminal is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. The second negative connection terminal among the three or more negative connection terminals is suitable for connecting. For connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit, the third negative connection terminal among the three or more negative connection terminals is suitable for connecting the first power conversion unit One photovoltaic string corresponding to the second power conversion unit and one photovoltaic string corresponding to the second power conversion unit.

Specifically, each protection switch unit includes at least three negative connection terminals, and each negative connection terminal is suitable to be connected to one or two photovoltaic strings in the photovoltaic string unit corresponding to a power conversion unit. Therefore, for a common negative connection The power conversion unit can be connected to the same power conversion unit through one or two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit and one or two photovoltaic strings in the corresponding photovoltaic string unit of another power conversion unit. A negative connection terminal is used to realize the sharing of the protection switches corresponding to the negative connection terminal, thereby realizing the sharing of at least three protection switches.

For example, referring to Figure 6g, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV6 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV7, PV8, ..., PV12 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV5 and PV6 corresponding to the power conversion unit 1 and the corresponding power conversion unit 2. Two parallel photovoltaic strings PV7 and PV8. The negative connection end of the protection switch unit 1 corresponding to the protection switch K7 is connected to a photovoltaic string PV3 corresponding to the power conversion unit 1 and two parallel photovoltaic strings corresponding to the power conversion unit 2. For strings PV9 and PV10, the negative connection end of the protection switch unit 1 corresponding to the protection switch K8 is connected to a photovoltaic string PV2 corresponding to the power conversion unit 1 and a photovoltaic string PV12 corresponding to the power conversion unit 2. In this way, based on the connection relationship between the three negative connection terminals and the photovoltaic strings corresponding to the two power conversion units, the protection switches K5, K7 and K8 are shared.

In this way, for a common negative power conversion unit, at least three protection switches can be shared.

In some embodiments, in the protection switch unit corresponding to the common positive power conversion unit, at least one positive connection terminal is adapted to connect the photovoltaic strings in different photovoltaic string units, so that the common positive power conversion unit corresponds to The protection switch unit shares the protection switch when connecting the corresponding photovoltaic string unit.

That is to say, for a common positive power conversion unit, the photovoltaic strings in different photovoltaic string units can be connected through the positive connection end of the protection switch unit to realize the sharing of protection switches and reduce the number of protection switches. During the connection, one or more positive connection terminals may be connected to the photovoltaic strings in different photovoltaic string units to realize the sharing of one or more protection switches.

Exemplarily, referring to Figure 7a, the power conversion unit 1 includes a DC-DC converter 1, the power conversion unit 2 includes a DC-DC converter 2, and the DC-DC converter 1 and the DC-DC converter 2 are co-positive, that is, The power conversion unit 1 and the power conversion unit 2 are co-positive, and the protection switch units corresponding to the co-positive power conversion unit 1 and the power conversion unit 2 are the protection switch unit 1 and the protection switch unit 2. Among them, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic string PV10 in the photovoltaic string unit 2; In the protection switch unit 2, the positive connection end of the protection switch unit 2 corresponding to the protection switch K6 is connected to the photovoltaic strings PV8 and PV9 in the photovoltaic string unit 2 and the photovoltaic string PV1 in the photovoltaic string unit 1. Protection switches K5 and K6 are shared by photovoltaic string unit 1 and photovoltaic string unit 2. Compared with not sharing, there are two fewer protection switches and the number of protection switches is reduced.

For example, referring to Figure 7b, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic string unit 2. The photovoltaic string PV10, the positive connection end of the protection switch unit 1 corresponding to the protection switch K4 is connected to the photovoltaic strings PV4 and PV5 in the photovoltaic string unit 1 and the photovoltaic strings PV6 and PV7 in the photovoltaic string unit 2; in In the protection switch unit 2, the positive connection end of the protection switch unit 2 corresponding to the protection switch K6 is connected to the photovoltaic strings PV8 and PV9 in the photovoltaic string unit 2 and the photovoltaic string PV1 in the photovoltaic string unit 1. Protection switches K4, K5 and K6 are shared by photovoltaic string unit 1 and photovoltaic string unit 2. Compared with not sharing, there are three fewer protection switches and the number of protection switches is reduced. Compared with the sharing in Figure 7a, it is reduced. A protection switch is installed, further reducing the number of protection switches.

In this way, for a common positive power conversion unit, the photovoltaic strings in different photovoltaic string units can be connected through one or more positive connection terminals of the corresponding protection switch unit, which can reduce the number of protection switches and thereby reduce the load of the protection switch unit. Cost and volume.

In some embodiments, when the co-positive power conversion unit includes a first power conversion unit and a second power conversion unit, one of the at least two positive connection terminals is adapted to connect two corresponding terminals of the first power conversion unit. A parallel photovoltaic string and a photovoltaic string corresponding to the second power conversion unit; or at least one of the two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and Two parallel photovoltaic strings corresponding to the second power conversion unit; or at least one of the two positive connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. A photovoltaic string.

Specifically, each protection switch unit includes at least two positive connection terminals, and each positive connection terminal is suitable to be connected to one or two photovoltaic strings in the photovoltaic string unit corresponding to a power conversion unit. Therefore, for a common positive connection The power conversion unit can be connected to the same power conversion unit through one or two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit and one or two photovoltaic strings in the corresponding photovoltaic string unit of another power conversion unit. A positive connection end is used to realize the sharing of the protection switches corresponding to the positive connection end, and thereby realize the sharing of at least one protection switch. There are many ways of sharing the protection switches.

For example, referring to Figure 7a, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV2 and PV3 corresponding to the power conversion unit 1 and the corresponding power conversion unit 2. A photovoltaic string PV10. In this way, based on a positive connection terminal connecting two parallel photovoltaic strings corresponding to one power conversion unit and one photovoltaic string corresponding to another power conversion unit, the sharing of the protection switch K5 is realized.

For example, referring to Figure 7b, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K4 is connected to the two parallel photovoltaic strings PV4 and PV5 corresponding to the power conversion unit 1 and the corresponding power conversion unit 2. Two parallel photovoltaic strings PV6 and PV7. In this way, based on a positive connection terminal connecting two parallel photovoltaic strings corresponding to one power conversion unit and two parallel photovoltaic strings corresponding to another power conversion unit, the sharing of the protection switch K4 is realized.

For example, referring to Figure 7c, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K7 is connected to a photovoltaic string PV2 corresponding to the power conversion unit 1 and a photovoltaic string corresponding to the power conversion unit 2. PV10. In this way, based on a positive connection terminal connecting a photovoltaic string corresponding to one power conversion unit and a photovoltaic string corresponding to another power conversion unit, the sharing of the protection switch K7 is realized.

In this way, for common-positive power conversion units, multiple ways can be used to realize the sharing of at least one protection switch.

In some embodiments, when the co-positive power conversion unit includes a first power conversion unit and a second power conversion unit, one of the at least two positive connection terminals is suitable for connecting to a corresponding one of the first power conversion unit. One photovoltaic string corresponding to the photovoltaic string and the second power conversion unit, and at least the other positive connection terminal of the two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and the second power conversion unit. Two parallel photovoltaic strings corresponding to the conversion unit; or at least one of the two positive connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic group corresponding to the second power conversion unit string, at least the other of the two positive connection terminals is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit; or at least two positive connection terminals. One of the positive connection terminals is suitable for connecting the two parallel photovoltaic strings corresponding to the first power conversion unit and the two parallel photovoltaic strings corresponding to the second power conversion unit, and at least the other of the two positive connection terminals is One positive connection end is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit.

Specifically, each protection switch unit includes at least two positive connection terminals, and each positive connection terminal is suitable to be connected to one or two photovoltaic strings in the photovoltaic string unit corresponding to a power conversion unit. Therefore, for a common positive connection The power conversion unit can be connected to the same power conversion unit through one or two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit and one or two photovoltaic strings in the corresponding photovoltaic string unit of another power conversion unit. A positive connection end is used to realize the sharing of the protection switches corresponding to the positive connection end, and then realize the sharing of at least two protection switches. Among them, there are many ways of sharing the protection switches.

For example, referring to Figure 7d, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K7 is connected to a photovoltaic string PV2 corresponding to the power conversion unit 1 and a photovoltaic string corresponding to the power conversion unit 2. PV10, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV4 and PV5 corresponding to the power conversion unit 1 and the two parallel photovoltaic strings PV6 and PV7 corresponding to the power conversion unit 2. . In this way, based on the fact that one positive connection terminal is connected to a photovoltaic string corresponding to a power conversion unit and a photovoltaic string corresponding to another power conversion unit, and the other positive connection terminal is connected to two parallel photovoltaic groups corresponding to a power conversion unit. The two parallel photovoltaic strings corresponding to the string and another power conversion unit realize the sharing of protection switches K7 and K5.

For example, referring to Figure 7e, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K7 is connected to a photovoltaic string PV2 corresponding to the power conversion unit 1 and a photovoltaic string corresponding to the power conversion unit 2. PV10, the positive connection end of the protection switch unit 1 corresponding to the protection switch K6 is connected to a photovoltaic string PV3 corresponding to the power conversion unit 1 and two parallel photovoltaic strings PV6 and PV7 corresponding to the power conversion unit 2. In this way, based on a positive connection terminal connecting a photovoltaic string corresponding to a power conversion unit and a photovoltaic string corresponding to another power conversion unit, and the other positive connection terminal connecting a photovoltaic string corresponding to a power conversion unit and another Two parallel photovoltaic strings corresponding to one power conversion unit realize the sharing of protection switches K7 and K6.

For example, referring to Figure 7f, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV6, PV7, ..., PV10 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K4 is connected to the two parallel photovoltaic strings PV4 and PV5 corresponding to the power conversion unit 1 and the corresponding power conversion unit 2. Two parallel photovoltaic strings PV6 and PV7, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to a photovoltaic string PV1 corresponding to the power conversion unit 1 and two parallel photovoltaics corresponding to the power conversion unit 2 Strings PV8 and PV9. In this way, based on the fact that one positive connection terminal is connected to two parallel photovoltaic strings corresponding to one power conversion unit and two parallel photovoltaic strings corresponding to another power conversion unit, and the other positive connection terminal is connected to one corresponding power conversion unit. One photovoltaic string and two parallel photovoltaic strings corresponding to another power conversion unit realize the sharing of protection switches K4 and K5.

In this way, for the common-positive power conversion unit, a variety of methods can be used to realize the sharing of at least two protection switches.

In some embodiments, when the co-positive power conversion unit includes a first power conversion unit and a second power conversion unit, if there are more than three positive connection terminals, the first positive connection terminal among the more than three positive connection terminals is Suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit, and the second positive connection terminal among the three or more positive connection terminals is suitable for connecting One photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. The third positive connection terminal among the three or more positive connection terminals is suitable for connecting to the first power conversion unit corresponding to the photovoltaic string. A photovoltaic string and a photovoltaic string corresponding to the second power conversion unit.

Specifically, each protection switch unit includes at least three positive connection terminals, and each positive connection terminal is suitable to be connected to one or two photovoltaic strings in the photovoltaic string unit corresponding to a power conversion unit. Therefore, for a common positive connection The power conversion unit can be connected to the same power conversion unit through one or two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit and one or two photovoltaic strings in the corresponding photovoltaic string unit of another power conversion unit. A positive connection end is used to realize the sharing of the protection switches corresponding to the positive connection end, thereby realizing the sharing of at least three protection switches.

For example, referring to Figure 7g, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV6 in the photovoltaic string unit 1. The power conversion unit may be the power conversion unit 2, and its corresponding photovoltaic strings are the photovoltaic strings PV7, PV8, ..., PV12 in the photovoltaic string unit 2. When the protection switch is shared, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV5 and PV6 corresponding to the power conversion unit 1 and the corresponding power conversion unit 2. Two parallel photovoltaic strings PV7 and PV8. The positive connection end of the protection switch unit 1 corresponding to the protection switch K7 is connected to a photovoltaic string PV3 corresponding to the power conversion unit 1 and two parallel photovoltaic strings corresponding to the power conversion unit 2. For strings PV9 and PV10, the positive connection end of the protection switch unit 1 corresponding to the protection switch K8 is connected to a photovoltaic string PV2 corresponding to the power conversion unit 1 and a photovoltaic string PV12 corresponding to the power conversion unit 2. In this way, based on the connection relationship between the three positive connection terminals and the photovoltaic strings corresponding to the two power conversion units, the protection switches K5, K7 and K8 are shared.

In this way, for a common positive power conversion unit, at least three protection switches can be shared.

In some embodiments, when there are at least three commonly negative power conversion units, at least one negative connection end is adapted to connect the photovoltaic strings in the photovoltaic string units corresponding to each common negative power conversion unit, so that at least The protection switch units corresponding to the three commonly negative power conversion units share the same protection switch when connected to the corresponding photovoltaic string unit.

Specifically, for co-negative power conversion units, the number of co-negative power conversion units can be two, three or more. When there are three or more, different photovoltaic groups can be connected through the negative connection end of the protection switch unit. The photovoltaic strings in the string unit are used to realize that the protection switch units corresponding to three or more commonly negative power conversion units share the same protection switch when connecting the corresponding photovoltaic string units to reduce the number of protection switches and thereby reduce the Cost and size of the protection switch unit.

In some embodiments, the negative connection end corresponding to the same protection switch is suitable for connecting one photovoltaic string corresponding to each common negative power conversion unit; or two parallel photovoltaic strings corresponding to each common negative power conversion unit. string; or one photovoltaic string corresponding to at least one common negative power conversion unit, and two parallel photovoltaic strings corresponding to at least one common negative power conversion unit.

Take three co-negative power conversion units 1, 2 and 3 as an example. Referring to Figure 8a, power conversion unit 1 includes DC-DC converter 1, power conversion unit 2 includes DC-DC converter 2, power conversion unit 3 includes DC-DC converter 3, DC-DC converters 1, 2 and 3 Commonly negative, that is, power conversion units 1, 2, and 3 are commonly negative. The protection switch units corresponding to the commonly negative power conversion units 1, 2, and 3 are protection switch units 1, 2, and 3. Among them, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K6 is connected to the photovoltaic string PV1 in the photovoltaic string unit 1, the photovoltaic string PV10 in the photovoltaic string unit 2 and the photovoltaic group. In the photovoltaic string PV15 in string unit 3, the protection switch K6 is shared by photovoltaic string units 1, 2 and 3. Compared with not sharing, there are two fewer protection switches and the number of protection switches is reduced. In this way, the negative connection end of the protection switch unit corresponding to the same protection switch is connected to a photovoltaic string of each common negative power conversion unit, thereby realizing that the protection switch unit corresponding to the common negative power conversion unit is connected to the corresponding photovoltaic string. unit, share the same protection switch.

For example, referring to Figure 8b, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV2 and PV3, the photovoltaic group in the photovoltaic string unit 1 For the two parallel-connected photovoltaic strings PV6 and PV7 in string unit 2 and the two parallel-connected photovoltaic strings PV11 and PV12 in photovoltaic string unit 3, the protection switch K5 is shared by photovoltaic string units 1, 2 and 3. Compared with not sharing, there are two fewer protection switches and the number of protection switches is reduced. In this way, the two parallel-connected photovoltaic strings of each common-negative power conversion unit are connected through the negative connection end of the protection switch unit corresponding to the same protection switch, thereby realizing that the protection switch unit corresponding to the common-negative power conversion unit is connected to the corresponding Photovoltaic string units share the same protection switch.

For example, referring to Figure 8c, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV2 and PV3, the photovoltaic group in the photovoltaic string unit 1 For one photovoltaic string PV10 in string unit 2 and two parallel photovoltaic strings PV11 and PV12 in photovoltaic string unit 3, the protection switch K5 is shared by photovoltaic string units 1, 2 and 3. Compared with not sharing, Two protection switches are reduced, reducing the number of protection switches. In this way, one photovoltaic string corresponding to at least one common negative power conversion unit and two parallel photovoltaic strings corresponding to at least one common negative power conversion unit are connected through the negative connection end of the protection switch unit corresponding to the same protection switch. , it is realized that the protection switch units corresponding to the shared negative power conversion units share the same protection switch when connected to the corresponding photovoltaic string units.

For example, referring to Figure 8d, in the protection switch unit 1, the negative connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV2 and PV3, the photovoltaic group in the photovoltaic string unit 1 One photovoltaic string PV10 in string unit 2 and one photovoltaic string PV15 in photovoltaic string unit 3. The protection switch K5 is shared by photovoltaic string units 1, 2 and 3. Compared with not sharing, three protection switches are reduced. switch, reducing the number of protection switches. In this way, one photovoltaic string corresponding to at least one common negative power conversion unit and two parallel photovoltaic strings corresponding to at least one common negative power conversion unit are connected through the negative connection end of the protection switch unit corresponding to the same protection switch. , it is realized that the protection switch units corresponding to the shared negative power conversion units share the same protection switch when connected to the corresponding photovoltaic string units.

It should be noted that for the sharing of protection switches of three or more commonly negative power conversion units, reference may be made to the relevant description of three commonly negative power conversion units, which will not be described again here.

In this way, various methods can be used to realize that the protection switch units corresponding to at least three commonly negative power conversion units share the same protection switch when connecting the corresponding photovoltaic string units.

In one embodiment, when there are at least three common-positive power conversion units, at least one positive connection end is adapted to connect the photovoltaic strings in the photovoltaic string unit corresponding to each common-positive power conversion unit, so that at least The protection switch units corresponding to the three common positive power conversion units share the same protection switch when connected to the corresponding photovoltaic string unit.

Specifically, for common-positive power conversion units, the number of common-positive power conversion units can be two, three or more. When there are three or more, different photovoltaic groups can be connected through the positive connection end of the protection switch unit. The photovoltaic strings in the string unit are used to realize that the protection switch units corresponding to three or more common positive power conversion units share the same protection switch when connecting the corresponding photovoltaic string units to reduce the number of protection switches and thereby reduce the Cost and size of the protection switch unit.

In one embodiment, the positive connection end corresponding to the same protection switch is suitable for connecting one photovoltaic string corresponding to each common positive power conversion unit; or two parallel photovoltaic strings corresponding to each common positive power conversion unit. string; or one photovoltaic string corresponding to at least one common positive power conversion unit, and two parallel photovoltaic strings corresponding to at least one common positive power conversion unit.

For example, three co-positive power conversion units 1, 2 and 3 are taken as an example. Referring to Figure 9a, power conversion unit 1 includes DC-DC converter 1, power conversion unit 2 includes DC-DC converter 2, power conversion unit 3 includes DC-DC converter 3, DC-DC converters 1, 2 and 3 Commonly positive, that is, power conversion units 1, 2, and 3 are collectively positive. The protection switch units corresponding to the commonly positive power conversion units 1, 2, and 3 are protection switch units 1, 2, and 3. Among them, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K6 is connected to the photovoltaic string PV1 in the photovoltaic string unit 1, the photovoltaic string PV10 in the photovoltaic string unit 2 and the photovoltaic group. In the photovoltaic string PV15 in string unit 3, the protection switch K6 is shared by photovoltaic string units 1, 2 and 3. Compared with not sharing, there are two fewer protection switches and the number of protection switches is reduced. In this way, the positive connection end of the protection switch unit corresponding to the same protection switch is connected to a photovoltaic string of each common-positive power conversion unit, so that the protection switch unit corresponding to the common-positive power conversion unit is connected to the corresponding photovoltaic string. unit, share the same protection switch.

For example, referring to Figure 9b, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV2 and PV3, the photovoltaic group in the photovoltaic string unit 1 For the two parallel-connected photovoltaic strings PV6 and PV7 in string unit 2 and the two parallel-connected photovoltaic strings PV11 and PV12 in photovoltaic string unit 3, the protection switch K5 is shared by photovoltaic string units 1, 2 and 3. Compared with not sharing, there are two fewer protection switches and the number of protection switches is reduced. In this way, the two parallel photovoltaic strings of each common-positive power conversion unit are connected through the positive connection end of the protection switch unit corresponding to the same protection switch, thereby realizing that the protection switch unit corresponding to the common-positive power conversion unit is connected to the corresponding Photovoltaic string units share the same protection switch.

For example, referring to Figure 9c, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV2 and PV3, the photovoltaic group in the photovoltaic string unit 1 For one photovoltaic string PV10 in string unit 2 and two parallel photovoltaic strings PV11 and PV12 in photovoltaic string unit 3, the protection switch K5 is shared by photovoltaic string units 1, 2 and 3. Compared with not sharing, Two protection switches are reduced, reducing the number of protection switches. In this way, one photovoltaic string corresponding to at least one common positive power conversion unit and two parallel photovoltaic strings corresponding to at least one common positive power conversion unit are connected through the positive connection end of the protection switch unit corresponding to the same protection switch. , it is realized that the protection switch units corresponding to the common positive power conversion units share the same protection switch when connected to the corresponding photovoltaic string units.

For example, referring to Figure 9d, in the protection switch unit 1, the positive connection end of the protection switch unit 1 corresponding to the protection switch K5 is connected to the two parallel photovoltaic strings PV2 and PV3, the photovoltaic group in the photovoltaic string unit 1 One photovoltaic string PV10 in string unit 2 and one photovoltaic string PV15 in photovoltaic string unit 3. The protection switch K5 is shared by photovoltaic string units 1, 2 and 3. Compared with not sharing, three protection switches are reduced. switch, reducing the number of protection switches. In this way, one photovoltaic string corresponding to at least one common positive power conversion unit and two parallel photovoltaic strings corresponding to at least one common positive power conversion unit are connected through the positive connection end of the protection switch unit corresponding to the same protection switch. , it is realized that the protection switch units corresponding to the common positive power conversion units share the same protection switch when connected to the corresponding photovoltaic string units.

It should be noted that for the sharing of protection switches of more than three common-positive power conversion units, reference may be made to the relevant description of three common-positive power conversion units, which will not be described again here.

In this way, various methods can be used to realize that the protection switch units corresponding to at least three common-positive power conversion units share the same protection switch when connecting the corresponding photovoltaic string units.

In some embodiments, when there are at least three co-positive or co-negative power conversion units, at least one power conversion unit shares at least one protection switch in the corresponding protection switch unit with other power conversion units.

That is to say, when there are three or more power conversion units that are both positive or negative, there are one or more power conversion units that are connected to one or more protection switches in the protection switch units corresponding to each other power conversion unit. Sharing, in order to reduce the number of protection switches through the sharing of protection switches, thereby reducing the cost and volume of the protection switch unit.

In some embodiments, when the common positive or common negative power conversion unit includes a first power conversion unit, a second power conversion unit and a third power conversion unit, the protection switch unit corresponding to the first power conversion unit includes at least two A positive connection end and at least two negative connection ends, each positive connection end is suitable for being connected to at most two photovoltaic strings in the photovoltaic string unit corresponding to the first power conversion unit, and each negative connection end is suitable for being connected to the first At most two photovoltaic strings in the photovoltaic string units corresponding to the power conversion unit are connected, wherein if the first power conversion unit, the second power conversion unit and the third power conversion unit are all negative, then at least two negative connection terminals The photovoltaic string unit corresponding to the second power conversion unit and the photovoltaic string unit corresponding to the third power conversion unit are respectively connected; if the first power conversion unit, the second power conversion unit and the third power conversion unit are both positive, then at least The two positive connection terminals are respectively connected to the photovoltaic string unit corresponding to the second power conversion unit and the photovoltaic string unit corresponding to the third power conversion unit.

That is to say, three power conversion units are taken as an example, which are respectively recorded as the first power conversion unit, the second power conversion unit and the third power conversion unit. Further, the first power conversion unit is taken as an example. When the protection switch unit corresponding to the first power conversion unit is connected to the photovoltaic string unit corresponding to the first power conversion unit, each positive connection end and each negative connection end need to be connected to the photovoltaic string unit corresponding to the first power conversion unit. One or two photovoltaic strings in the unit are connected, and when the three power conversion units are both negative, the photovoltaic string in the photovoltaic string unit corresponding to the second power conversion unit and the third power conversion unit are connected through the negative connection terminal. The photovoltaic strings in the corresponding photovoltaic string units are connected to realize the sharing of protection switches; when the three power conversion units are both positive, the photovoltaic strings in the photovoltaic string unit corresponding to the second power conversion unit are connected through the positive connection end. The photovoltaic strings in the string and the photovoltaic string unit corresponding to the third power conversion unit are connected to realize the sharing of the protection switch. In this way, the number of protection switches can be reduced by sharing the protection switches, thereby reducing the cost and volume of the protection switch unit.

It should be noted that for the second power conversion unit and the third power conversion unit, the protection switch can also be shared in the same manner as the first power conversion unit, and there is no specific limitation here.

In some embodiments, when the first power conversion unit, the second power conversion unit and the third power conversion unit are both negative, one of the at least two negative connection terminals is suitable for connecting to the second power conversion unit. For the corresponding two parallel photovoltaic strings, at least the other negative connection terminal of the two negative connection terminals is suitable for connecting to a photovoltaic string corresponding to the third power conversion unit; or at least one of the two negative connection terminals is connected negatively. The terminal is suitable for connecting two parallel photovoltaic strings corresponding to the second power conversion unit, and the other negative connection terminal of at least two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the third power conversion unit; Or at least one of the two negative connection terminals is suitable for connecting to a photovoltaic string corresponding to the second power conversion unit, and the other negative connection terminal of at least two negative connection terminals is suitable for connecting to the corresponding photovoltaic string of the third power conversion unit. of a photovoltaic string.

For example, referring to Figure 10a, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be power conversion unit 2, and its corresponding photovoltaic strings may be photovoltaic strings PV6, PV7, ..., PV10 in photovoltaic string unit 2. The third power conversion unit may be power conversion unit 3, And the corresponding photovoltaic strings are photovoltaic strings PV11, PV12, ..., PV15 in photovoltaic string unit 3.

When the protection switch is shared, in the protection switch unit 1, the protection switch K5 connects the two parallel photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the two parallel photovoltaic strings PV6 in the photovoltaic string unit 2. and PV7, protection switch K5 is shared by photovoltaic string units 2 and 1, that is, shared by power conversion units 2 and 1; protection switch K4 is connected to the two parallel photovoltaic strings PV4 and PV5 in photovoltaic string unit 1 and the photovoltaic For one photovoltaic string PV15 in string unit 3, the protection switch K4 is shared by photovoltaic string units 1 and 3, that is, it is shared by power conversion units 1 and 3. In this way, it is realized that the power conversion unit 1 and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

For example, referring to Figure 10b, when the protection switch is shared, in the protection switch unit 1, the protection switch K5 connects the two parallel photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic string unit 2. For the two parallel-connected photovoltaic strings PV6 and PV7, the protection switch K5 is shared by the photovoltaic string units 1 and 2, that is, by the power conversion units 1 and 2; the protection switch K4 is connected to the two parallel-connected photovoltaic string units 1. For the photovoltaic strings PV4 and PV5 and the two parallel photovoltaic strings PV14 and PV15 in the photovoltaic string unit 3, the protection switch K4 is shared by the photovoltaic string units 3 and 1, that is, it is shared by the power conversion units 3 and 1. In this way, it is realized that the power conversion unit 1 and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

For example, referring to Figure 10c, when the protection switch is shared, in the protection switch unit 1, the protection switch K5 connects the two parallel photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic string unit 2. For a photovoltaic string PV10, the protection switch K5 is shared by the photovoltaic string units 1 and 2, that is, it is shared by the power conversion units 1 and 2; the protection switch K4 is connected to the two parallel photovoltaic strings PV4 and PV in the photovoltaic string unit 1. PV5 and one photovoltaic string PV15 in the photovoltaic string unit 3, the protection switch K4 is shared by the photovoltaic string units 1 and 3, that is, it is shared by the power conversion units 1 and 3. In this way, it is realized that the power conversion unit 1 and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

It can be understood that in Figures 8a-8d, the power conversion unit 1 also shares at least one protection switch in the corresponding protection switch unit 1 with the power conversion unit 2, and the power conversion unit 1 and the power conversion unit 3 share the corresponding protection switch. At least one protection switch in the switch unit 1 is shared.

It should be noted that the above description takes the first power conversion unit as an example, and the second power conversion unit and the third power conversion unit can also use the same sharing method as the first power conversion unit, and can be used with other power conversion units. For sharing of protection switches, there are no specific restrictions here. In addition, the above is only an illustrative description and is not intended to limit the present application.

In some embodiments, when the first power conversion unit, the second power conversion unit and the third power conversion unit are both positive, one of the at least two positive connection terminals is suitable for connecting to the second power conversion unit. For the corresponding two parallel photovoltaic strings, at least the other positive connection terminal of the two positive connection terminals is suitable for connecting to a photovoltaic string corresponding to the third power conversion unit; or at least one of the two positive connection terminals is connected The terminal is suitable for connecting two parallel photovoltaic strings corresponding to the second power conversion unit, and the other positive connection terminal of at least two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the third power conversion unit; Or at least one of the two positive connection terminals is suitable for connecting to a photovoltaic string corresponding to the second power conversion unit, and at least the other positive connection terminal of the two positive connection terminals is suitable for connecting to the corresponding photovoltaic string of the third power conversion unit. of a photovoltaic string.

For example, referring to Figure 11a, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1, and the second The power conversion unit may be power conversion unit 2, and its corresponding photovoltaic strings may be photovoltaic strings PV6, PV7, ..., PV10 in photovoltaic string unit 2. The third power conversion unit may be power conversion unit 3, And the corresponding photovoltaic strings are photovoltaic strings PV11, PV12, ..., PV15 in photovoltaic string unit 3.

When the protection switch is shared, in the protection switch unit 1, the protection switch K5 connects the two parallel photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the two parallel photovoltaic strings PV6 in the photovoltaic string unit 2. and PV7, protection switch K5 is shared by photovoltaic string units 2 and 1, that is, shared by power conversion units 2 and 1; protection switch K4 is connected to the two parallel photovoltaic strings PV4 and PV5 in photovoltaic string unit 1 and the photovoltaic For one photovoltaic string PV15 in string unit 3, the protection switch K4 is shared by photovoltaic string units 1 and 3, that is, it is shared by power conversion units 1 and 3. In this way, it is realized that the power conversion unit 1 and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

For example, referring to Figure 11b, when the protection switch is shared, in the protection switch unit 1, the protection switch K5 connects the two parallel photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic string unit 2. For the two parallel-connected photovoltaic strings PV6 and PV7, the protection switch K5 is shared by the photovoltaic string units 1 and 2, that is, by the power conversion units 1 and 2; the protection switch K4 is connected to the two parallel-connected photovoltaic string units 1. For the photovoltaic strings PV4 and PV5 and the two parallel photovoltaic strings PV14 and PV15 in the photovoltaic string unit 3, the protection switch K4 is shared by the photovoltaic string units 3 and 1, that is, it is shared by the power conversion units 3 and 1. In this way, it is realized that the power conversion unit 1 and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

For example, referring to Figure 11c, when the protection switch is shared, in the protection switch unit 1, the protection switch K5 connects the two parallel photovoltaic strings PV2 and PV3 in the photovoltaic string unit 1 and the photovoltaic string unit 2. For a photovoltaic string PV10, the protection switch K5 is shared by the photovoltaic string units 1 and 2, that is, it is shared by the power conversion units 1 and 2; the protection switch K4 is connected to the two parallel photovoltaic strings PV4 and PV in the photovoltaic string unit 1. PV5 and one photovoltaic string PV15 in the photovoltaic string unit 3, the protection switch K4 is shared by the photovoltaic string units 1 and 3, that is, it is shared by the power conversion units 1 and 3. In this way, it is realized that the power conversion unit 1 and each other power conversion unit share at least one protection switch in the corresponding protection switch unit.

It can be understood that in Figures 9a-9d, the power conversion unit 1 also shares at least one protection switch in the corresponding protection switch unit 1 with the power conversion unit 2, and the power conversion unit 1 and the power conversion unit 3 share the corresponding protection switch. At least one protection switch in the switch unit 1 is shared.

It should be noted that the above description takes the first power conversion unit as an example, and the second power conversion unit and the third power conversion unit can also use the same sharing method as the first power conversion unit, and can be used with other power conversion units. For sharing of protection switches, there are no specific restrictions here. In addition, the above is only an illustrative description and is not intended to limit the present application.

In this way, when there are three or more power conversion units that are both positive or negative, at least one power conversion unit can share at least one protection switch in the corresponding protection switch unit with each other power conversion unit, thereby reducing the number of Number of protection switches.

In some embodiments, when there are at least three co-positive or co-negative power conversion units, any two power conversion units among the at least three co-positive or co-negative power conversion units are critical to at least one of the corresponding protection switch units. Protection switches are shared.

That is to say, when there are three or more co-positive or co-negative power conversion units, any two power conversion units among at least three co-positive or co-negative power conversion units will cause damage to one of the corresponding protection switch units. Or multiple protection switches can be shared to reduce the number of protection switches through the sharing of protection switches, thereby reducing the cost and volume of the protection switch unit.

In some embodiments, when the co-positive or co-negative power conversion unit includes a first power conversion unit, a second power conversion unit and a third power conversion unit, the first power conversion unit and the second power conversion unit provide corresponding protection At least one protection switch in the switch unit is shared, the first power conversion unit and the third power conversion unit share at least one protection switch in the corresponding protection switch unit, and the second power conversion unit and the third power conversion unit share the corresponding protection switch. At least one protective switch in the switch unit is shared.

For example, referring to Figure 12, the first power conversion unit may be the power conversion unit 1, and its corresponding photovoltaic strings may be the photovoltaic strings PV1, PV2, ..., PV5 in the photovoltaic string unit 1. The power conversion unit may be power conversion unit 2, and its corresponding photovoltaic strings may be photovoltaic strings PV6, PV7, ..., PV10 in photovoltaic string unit 2. The third power conversion unit may be power conversion unit 3, And the corresponding photovoltaic strings are photovoltaic strings PV11, PV12, ..., PV15 in photovoltaic string unit 3.

When the protection switch is shared, protection switch K5 is connected to two parallel photovoltaic strings PV2 and PV3 in photovoltaic string unit 1 and one photovoltaic string PV10 in photovoltaic string unit 2. Protection switch K5 is connected to photovoltaic string unit 1. Shared with 2, that is, shared by power conversion units 1 and 2; protection switch K4 connects two parallel photovoltaic strings PV4 and PV5 in photovoltaic string unit 1 and one photovoltaic string PV15 in photovoltaic string unit 3, Protection switch K4 is shared by photovoltaic string units 1 and 3, that is, shared by power conversion units 1 and 3; protection switch K11 is connected to the two parallel photovoltaic strings PV13 and PV14 in photovoltaic string unit 3 and the photovoltaic string unit. For one photovoltaic string PV1 in 1, the protection switch K11 is shared by the photovoltaic string units 3 and 1, that is, it is shared by the power conversion units 3 and 1; the protection switch K12 connects the two parallel photovoltaic groups in the photovoltaic string unit 3. For the strings PV11 and PV12 and the two parallel photovoltaic strings PV6 and PV7 in the photovoltaic string unit 2, the protection switch K12 is shared by the photovoltaic string units 3 and 2, that is, it is shared by the power conversion units 3 and 2. In this way, any two power conversion units can share at least one protection switch in the corresponding protection switch unit.

It should be noted that FIG. 12 takes a co-negative power conversion unit as an example. The co-positive power conversion unit is similar to the co-negative power conversion unit and will not be described again here. In addition, for the case of three or more, please refer to the case of three, which will not be repeated here.

In this way, when there are three or more common positive or common negative power conversion units, any two power conversion units can share at least one protection switch in the corresponding protection switch unit, thereby reducing the number of protection switches.

In some embodiments, multiple protection switches in each protection switch unit may be configured as multi-pole linkage switches. A multi-pole linkage switch refers to a switch that includes multiple pole switches and the multiple pole switches can be linked. For example, multiple pole switches can be turned on or off at the same time. Among them, the pole switch includes a positive pole switch and a negative pole switch. The positive pole switch refers to the switch connected to the positive pole of the photovoltaic string, such as the protection switches K1, K2 and K3 in Figure 12. The negative pole switch refers to the switch connected to the negative pole of the photovoltaic string. Switches, such as protection switches K4, K5, etc. in Figure 12, the structure and model of the positive switch and the negative switch can be the same or different. That is to say, the switch itself does not need to be distinguished, and both can be but are not limited to DC circuit breakers. Devices etc.

Based on the foregoing analysis, it can be seen that in embodiments of the present invention, the number of protection switches can be reduced. Therefore, when the protection switch unit is a multi-pole linkage switch, a smaller number of protection switches is beneficial to reducing the manufacturing difficulty of the multi-pole linkage switch and Improve the linkage reliability of multi-pole linkage switches.

In some embodiments, when there is a reverse-connected faulty branch in the photovoltaic power generation system, at least three protection switches bear the responsibility when the common positive or common negative power conversion unit disconnects the corresponding protection switch unit based on the reverse-connected faulty branch. Twice the PV string voltage.

It should be noted that the reverse connection fault branch refers to the photovoltaic string branch where the reverse connection fault occurs. For example, referring to Figure 4a, when a feedback fault occurs in the photovoltaic string PV1, the photovoltaic string branch corresponding to the protection switch K1 The photovoltaic string branch corresponding to the circuit and protection switch K6 is a reverse connection fault branch.

When a reverse connection fault occurs in the photovoltaic power generation system, the photovoltaic string with the reverse connection fault can be detected, that is, the reverse connection fault branch can be detected, and the protection switch unit corresponding to the reverse connection fault branch can be controlled to open. For example, referring to Figure 4a, when a reverse connection fault occurs in the photovoltaic string PV1, the protective switch units 1 and 2 are controlled to be disconnected. Furthermore, when the protective switch units 1 and 2 are controlled to be turned off, at least three protective switches will withstand twice the photovoltaic string voltage. For example, referring to Figure 4a, when a reverse connection fault occurs in the photovoltaic string PV1, in the circuit composed of the photovoltaic strings PV2 and PV1, there will be protective switches K2, K1, K6 and K5 to withstand twice the photovoltaic string voltage. ;In the loop composed of photovoltaic strings PV3 and PV1, there will be protective switches K3, K1, K6 and K4 to withstand twice the photovoltaic string voltage, but photovoltaic strings PV4, PV5 and PV6 cannot form a loop with photovoltaic string PV1 , correspondingly, the unprotected switch can withstand twice the photovoltaic string voltage. Since it is sufficient to withstand twice the PV string voltage via at least three protective switches, low-cost low-voltage protective switches can be used.

It should be noted that for other situations, you can refer to the above, and the details will not be repeated here.

In this way, protection switches with lower voltage levels can be used for disconnection, which reduces the number of protection switches without increasing the withstand voltage level of the protection switches, that is, while low-cost low-voltage protection switches can continue to be used. , thereby reducing the cost and volume of the protection switch unit.

To sum up, according to the inverter of the photovoltaic power generation system according to the embodiment of the present invention, since the photovoltaic string branch is connected to one photovoltaic string or two parallel photovoltaic strings, the power conversion unit of a common positive or a common negative When the corresponding protection switch unit is connected to the corresponding photovoltaic string unit, the protection switch is shared, so that when the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, at least three protection switches are used to connect the corresponding photovoltaic strings. Therefore, the number of protection switches can be reduced without increasing the withstand voltage level of the protection switch, thereby reducing the cost and volume of the protection switch unit.

In some embodiments, a fault protection device 100 for a photovoltaic power generation system is also provided.

Referring to Figure 13, the photovoltaic power generation system also includes multiple photovoltaic string units (such as photovoltaic string units 1 and 2) and multiple power conversion units (such as power conversion units 1 and 2), wherein among the multiple photovoltaic string units Each photovoltaic string unit includes at least N photovoltaic strings (such as photovoltaic strings PV1, PV2 and PV3, etc.), where N is an integer greater than or equal to 3.

The fault protection device 100 includes: multiple protection switch units (such as protection switch units 1 and 2), each of the multiple protection switch units includes multiple protection switches (such as protection switches K1, K2, K3, etc.), Each protection switch unit is adapted to correspondingly connect one photovoltaic string unit among the plurality of photovoltaic string units to one power conversion unit among the plurality of power conversion units to form at least two photovoltaic string branches. The photovoltaic strings The branch is suitable for connecting one photovoltaic string or two parallel photovoltaic strings. Among them, when there are common positive or common negative power conversion units in multiple power conversion units, the protection switch units corresponding to the common positive or common negative power conversion units share the protection switches when connecting the corresponding photovoltaic string units. , so that when the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, at least three protection switches are used to separate the corresponding photovoltaic strings.

It should be noted that for relevant descriptions of the fault protection device 100, please refer to the aforementioned relevant descriptions of the inverter, which will not be described again here. In addition, FIG. 13 is only an illustrative description and is not intended to limit the present application.

In some embodiments, a combiner box 200 is also provided. Referring to Fig. 14, the combiner box 200 may include the aforementioned fault protection device 100. The fault protection device 100 is configured to, in the event of a fault in the photovoltaic power generation system, protect multiple power conversion units (such as power conversion unit 1, .. ., power conversion unit M) and multiple photovoltaic string units (such as photovoltaic string unit 1, .., photovoltaic string unit M) are fully disconnected or partially disconnected so that they can be in a common positive or common state. When the protection switch unit corresponding to the negative power conversion unit is turned off, at least three protection switches are used to separate the corresponding photovoltaic strings (such as photovoltaic strings PV1, PV2 and PV3, etc.).

It should be noted that fully or partially disconnecting the connections between the multiple power conversion units and the multiple photovoltaic string units means that the multiple protection switch units in the fault protection device 100 are partially disconnected or fully disconnected. On, specifically, it means that only some of the multiple protection switch units may be disconnected, or all the protection switch units may be disconnected. The details can be determined based on the fault detection results and actual needs. For example, based on the safety of the photovoltaic power generation system, when a fault in the photovoltaic power generation system is detected, all the protection switch units can be controlled to be disconnected; based on the power supply reliability of the photovoltaic power generation system, when a fault in the photovoltaic power generation system is detected, In the event of a fault, multiple protection switch units are controlled to be partially disconnected based on the fault detection results, and the remaining protection switch units maintain their current status, so that the photovoltaic power generation system can continue to provide power and ensure the reliability of the power supply.

There are many situations when controlling partial disconnection of multiple protection switch units based on fault detection results. For example, without considering cost, etc., current sensors can be installed on the positive and negative poles of each photovoltaic string. The current sensors can detect photovoltaic strings that have reverse connection faults or short-circuit faults, and then control the photovoltaic strings. The corresponding protection switch unit is disconnected.

In consideration of cost, etc., it is possible to install a current sensor only on the positive pole of each photovoltaic string. However, the current sensor can only detect photovoltaic strings with reverse connection faults and cannot detect photovoltaic strings with short circuit faults. In this case, you can first determine whether a reverse connection fault or a short-circuit fault occurs in the photovoltaic power generation system. The details can be based on the voltage. For example, when a reverse connection fault occurs, the protection switch corresponding to the photovoltaic string will withstand twice the voltage of the photovoltaic string. Based on this voltage, a reverse connection fault in the photovoltaic power generation system can be detected. When it is determined that a reverse connection fault occurs in the photovoltaic power generation system, the photovoltaic string that has the reverse connection fault can be determined based on the current detected by the current sensor, and then the protection switch unit corresponding to the photovoltaic string is controlled to be disconnected. When it is determined that a short-circuit fault occurs in the photovoltaic power generation system, since the photovoltaic string with the short-circuit fault cannot be determined based on the current detected by the current sensor, multiple protection switch units need to be controlled to be turned off. For example, referring to Figure 13, in the photovoltaic group When the positive electrode PV1+ of PV string PV1 is grounded, since the current of the negative electrode PV1- of PV string PV1 cannot be detected, it is not certain whether the negative electrode PV1- of PV string PV1 is grounded. It may be that the negative electrode PV1- of PV string PV1 is grounded. It may also be that the negative pole of other photovoltaic strings is grounded, so it is impossible to determine which photovoltaic string is grounded and causes a short-circuit fault in the photovoltaic string. Therefore, multiple protection switch units need to be controlled to open all.

In addition, for relevant descriptions of the fault protection device 100 in the combiner box 200 , reference may be made to the foregoing relevant descriptions of the inverter, which will not be described again here.

According to the combiner box of the photovoltaic power generation system according to the embodiment of the present invention, based on the aforementioned fault protection device, the number of protection switches can be reduced without increasing the voltage resistance level of the protection switches, thereby reducing the cost and volume of the protection switch unit. .

In some embodiments, a photovoltaic power generation system 300 is also provided. Referring to FIG. 15 , the photovoltaic power generation system 300 includes a plurality of photovoltaic string units (such as photovoltaic string units 1, ..., photovoltaic string units M). Each photovoltaic string unit in the plurality of photovoltaic string units includes at least N photovoltaic strings (such as photovoltaic strings PV1, PV2 and PVN), N is an integer greater than or equal to 3. The photovoltaic power generation system also includes: the aforementioned fault protection device 100, or the aforementioned combiner box; or the aforementioned inverter .

It should be noted that for relevant descriptions of the fault protection device 100, the combiner box and the inverter, please refer to the foregoing description and will not be repeated here.

According to the photovoltaic power generation system according to the embodiment of the present invention, based on the aforementioned fault protection device, combiner box or inverter, the number of protection switches can be reduced without increasing the withstand voltage level of the protection switches, thereby reducing the number of protection switch units. cost and volume.

It should be noted that the logic and/or steps represented in the flowcharts or otherwise described herein, for example, may be considered to be a sequenced list of executable instructions for implementing logical functions, which may be embodied in any computer. in a readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a system including a processor, or other system that can retrieve and execute instructions from the instruction execution system, apparatus, or device) Used by instruction execution systems, devices or equipment. For the purposes of this specification, a "computer-readable medium" may be any device that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. More specific examples (non-exhaustive list) of computer readable media include the following: electrical connections with one or more wires (electronic device), portable computer disk cartridges (magnetic device), random access memory (RAM), Read-only memory (ROM), erasable and programmable read-only memory (EPROM or flash memory), fiber optic devices, and portable compact disc read-only memory (CDROM). Additionally, the computer-readable medium may even be paper or other suitable medium on which the program may be printed, as the paper or other medium may be optically scanned, for example, and subsequently edited, interpreted, or otherwise suitable as necessary. process to obtain the program electronically and then store it in computer memory.

It should be understood that various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, various steps or methods may be implemented in software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if it is implemented in hardware, as in another embodiment, it can be implemented by any one or a combination of the following technologies known in the art: a logic gate circuit with a logic gate circuit for implementing a logic function on a data signal. Discrete logic circuits, application specific integrated circuits with suitable combinational logic gates, programmable gate arrays (PGA), field programmable gate arrays (FPGA), etc.

In the description of this specification, reference to the terms "one embodiment," "some embodiments," "an example," "specific examples," or "some examples" or the like means that specific features are described in connection with the embodiment or example. , structures, materials or features are included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. In addition, the terms “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features. Therefore, features defined as "first" and "second" may explicitly or implicitly include at least one of these features. In the description of the present invention, "plurality" means at least two, such as two, three, etc., unless otherwise clearly and specifically limited. In this utility model, unless otherwise expressly stipulated and limited, the terms "installation", "connection", "connection", "fixing" and other terms should be understood in a broad sense. For example, it can be a fixed connection or a detachable connection. Connection, or integration; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be an internal connection between two elements or an interaction between two elements, unless otherwise clear limits. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. Although the embodiments of the present invention have been shown and described above, it can be understood that the above-mentioned embodiments are illustrative and cannot be construed as limitations of the present invention. Those of ordinary skill in the art are within the scope of the present invention. Changes, modifications, substitutions and variations may be made to the above-described embodiments.

Claims (26)

1. An inverter for a photovoltaic power generation system, characterized in that the photovoltaic power generation system further includes a plurality of photovoltaic string units, and each of the plurality of photovoltaic string units includes at least N Photovoltaic string, N is an integer greater than or equal to 3, and the inverter includes: Multiple power conversion units; A plurality of protection switch units, each of the plurality of protection switch units includes a plurality of protection switches, and each protection switch unit is adapted to correspond to one of the plurality of photovoltaic string units. connected to one power conversion unit among the plurality of power conversion units to form at least two photovoltaic string branches, the photovoltaic string branches being suitable for connecting one photovoltaic string or two parallel photovoltaic strings, in, In the case where there are common positive or common negative power conversion units in the plurality of power conversion units, the protection switch units corresponding to the common positive or common negative power conversion units share the protection switches when connecting the corresponding photovoltaic string units. , so that when the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, at least three protection switches are used to separate the corresponding photovoltaic strings. 2. The inverter according to claim 1, characterized in that each protection switch unit includes at least two positive connection terminals and at least two negative connection terminals, and each of the positive connection terminals is adapted to be connected to a power conversion terminal. At most two photovoltaic strings in the photovoltaic string unit corresponding to the unit are connected, and each of the negative connection terminals is suitable to be connected to at most two photovoltaic strings in the photovoltaic string unit corresponding to one power conversion unit. 3. The inverter according to claim 1, characterized in that, in the protection switch unit corresponding to the commonly negative power conversion unit, at least one negative connection end is suitable for connecting photovoltaic strings in different photovoltaic string units. , so that the protection switch units corresponding to the shared negative power conversion units share the protection switches when connecting the corresponding photovoltaic string units. 4. The inverter according to claim 3, characterized in that when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, wherein, One of at least two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and one photovoltaic string corresponding to the second power conversion unit; or One of at least two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit; or One of at least two negative connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. 5. The inverter according to claim 3, characterized in that when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, wherein, One of at least two negative connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. The other negative connection end is suitable for connecting the two parallel photovoltaic strings corresponding to the first power conversion unit and the two parallel photovoltaic strings corresponding to the second power conversion unit; or One of at least two negative connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. The other negative connection end is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit; or At least one of the two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit, at least The other negative connection terminal among the two negative connection terminals is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. 6. The inverter according to claim 3, wherein when the commonly negative power conversion unit includes a first power conversion unit and a second power conversion unit, if there are more than three negative connection terminals, wherein , The first negative connection terminal among the three or more negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. , the second negative connection end among the three or more negative connection ends is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. Three The third negative connection terminal among the more than one negative connection terminal is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. 7. The inverter according to claim 2, wherein in the protection switch unit corresponding to the common positive power conversion unit, at least one positive connection end is suitable for connecting photovoltaic strings in different photovoltaic string units. , so that the protection switch units corresponding to the common positive power conversion units share the protection switches when connecting the corresponding photovoltaic string units. 8. The inverter according to claim 7, characterized in that when the common positive power conversion unit includes a first power conversion unit and a second power conversion unit, wherein, One of at least two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and one photovoltaic string corresponding to the second power conversion unit; or One of at least two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit; or One of at least two positive connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. 9. The inverter according to claim 7, wherein when the common positive power conversion unit includes a first power conversion unit and a second power conversion unit, wherein, One of at least two positive connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. The other positive connection end is suitable for connecting the two parallel photovoltaic strings corresponding to the first power conversion unit and the two parallel photovoltaic strings corresponding to the second power conversion unit; or One of at least two positive connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. The other positive connection end is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit; or At least one of the two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit, at least The other of the two positive connection terminals is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. 10. The inverter according to claim 7, wherein when the common positive power conversion unit includes a first power conversion unit and a second power conversion unit, if there are more than three positive connection terminals, wherein , The first positive connection terminal among the three or more positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. , the second positive connection terminal among the three or more positive connection terminals is suitable for connecting one photovoltaic string corresponding to the first power conversion unit and two parallel photovoltaic strings corresponding to the second power conversion unit. Three The third positive connection terminal among the more than one positive connection terminals is suitable for connecting a photovoltaic string corresponding to the first power conversion unit and a photovoltaic string corresponding to the second power conversion unit. 11. The inverter according to claim 3, characterized in that when there are at least three commonly negative power conversion units, at least one negative connection end is adapted to connect the photovoltaic power conversion unit corresponding to each common negative power conversion unit. The photovoltaic strings in the string unit are configured so that the protection switch units corresponding to at least three commonly negative power conversion units share the same protection switch when connecting the corresponding photovoltaic string units. 12. The inverter according to claim 11, characterized in that the negative connection end corresponding to the same protection switch is suitable for connection: One photovoltaic string corresponding to each common negative power conversion unit; or Two parallel photovoltaic strings corresponding to each common negative power conversion unit; or One photovoltaic string corresponding to at least one common negative power conversion unit, and two parallel photovoltaic strings corresponding to at least one common negative power conversion unit. 13. The inverter according to claim 7, wherein when there are at least three common-positive power conversion units, at least one positive connection end is adapted to connect the photovoltaic power conversion unit corresponding to each common-positive power conversion unit. The photovoltaic strings in the string units are configured so that the protection switch units corresponding to at least three common positive power conversion units share the same protection switch when connecting the corresponding photovoltaic string units. 14. The inverter according to claim 13, characterized in that the positive connection terminal corresponding to the same protection switch is suitable for connection, One photovoltaic string corresponding to each common positive power conversion unit; or Two parallel photovoltaic strings corresponding to each common positive power conversion unit; or One photovoltaic string corresponding to at least one common positive power conversion unit, and two parallel photovoltaic strings corresponding to at least one common positive power conversion unit. 15. The inverter according to claim 1, characterized in that when there are at least three co-positive or co-negative power conversion units, at least one power conversion unit is in a corresponding protection switch unit with other power conversion units respectively. At least one protection switch must be shared. 16. The inverter according to claim 15, wherein when the common positive or common negative power conversion units comprise a first power conversion unit, a second power conversion unit and a third power conversion unit, the third power conversion unit A protection switch unit corresponding to a power conversion unit includes at least two positive connection terminals and at least two negative connection terminals, and each of the positive connection terminals is suitable for at least one of the photovoltaic string units corresponding to the first power conversion unit. Two photovoltaic strings are connected, and each negative connection end is suitable to be connected to at most two photovoltaic strings in the photovoltaic string unit corresponding to the first power conversion unit, wherein, If the first power conversion unit, the second power conversion unit and the third power conversion unit are all negative, then the photovoltaic string unit corresponding to the second power conversion unit and the third power conversion unit are respectively connected through at least two negative connection terminals. The photovoltaic string unit corresponding to the three power conversion units; If the first power conversion unit, the second power conversion unit and the third power conversion unit are all positive, then the photovoltaic string unit corresponding to the second power conversion unit and the third power conversion unit are respectively connected through at least two positive connection terminals. The photovoltaic string unit corresponding to the three power conversion units. 17. The inverter according to claim 16, characterized in that when the first power conversion unit, the second power conversion unit and the third power conversion unit are both negative, wherein, One of the at least two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the second power conversion unit, and the other of the at least two negative connection terminals is suitable for connecting the A photovoltaic string corresponding to the third power conversion unit; or One of the at least two negative connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the second power conversion unit, and the other of the at least two negative connection terminals is suitable for connecting the Two parallel photovoltaic strings corresponding to the third power conversion unit; or One of at least two negative connection terminals is suitable for connecting to a photovoltaic string corresponding to the second power conversion unit, and the other negative connection terminal of at least two negative connection terminals is suitable for connecting to the third power A photovoltaic string corresponding to the conversion unit. 18. The inverter according to claim 16, characterized in that when the first power conversion unit, the second power conversion unit and the third power conversion unit are both positive, wherein, One of the at least two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the second power conversion unit, and the other of the at least two positive connection terminals is suitable for connecting the A photovoltaic string corresponding to the third power conversion unit; or One of the at least two positive connection terminals is suitable for connecting two parallel photovoltaic strings corresponding to the second power conversion unit, and the other of the at least two positive connection terminals is suitable for connecting the Two parallel photovoltaic strings corresponding to the third power conversion unit; or One of at least two positive connection terminals is suitable for connecting to a photovoltaic string corresponding to the second power conversion unit, and the other of at least two positive connection terminals is suitable for connecting to the third power A photovoltaic string corresponding to the conversion unit. 19. The inverter according to claim 1, characterized in that when there are at least three co-positive or co-negative power conversion units, any two power conversion units among the at least three co-positive or co-negative power conversion units The conversion unit shares at least one protection switch in the corresponding protection switch unit. 20. The inverter according to claim 19, wherein when the commonly positive or commonly negative power conversion units comprise a first power conversion unit, a second power conversion unit and a third power conversion unit, the third power conversion unit A power conversion unit and the second power conversion unit share at least one protection switch in the corresponding protection switch unit, and the first power conversion unit and the third power conversion unit share at least one protection switch unit in the corresponding protection switch unit. The protection switches are shared, and the second power conversion unit and the third power conversion unit share at least one protection switch in the corresponding protection switch unit. 21. The inverter according to any one of claims 1-20, characterized in that the plurality of protection switches in each protection switch unit are configured as multi-pole linkage switches. 22. The inverter according to any one of claims 1-20, wherein each power conversion unit includes a DC-DC converter, wherein, When the negative terminals of any two DC-DC converters are connected together, the two power conversion units are both negative; or When the positive terminals of any two DC-DC converters are connected together, the two power conversion units are both positive. 23. The inverter according to any one of claims 1 to 20, characterized in that when there is a reverse-connection fault branch in the photovoltaic power generation system, the power conversion unit with a common positive or a common negative is based on the When the reverse connection fault branch disconnects the corresponding protection switch unit, at least three protection switches bear twice the photovoltaic string voltage. 24. A fault protection device for a photovoltaic power generation system, characterized in that the photovoltaic power generation system further includes a plurality of photovoltaic string units and a plurality of power conversion units, wherein each of the plurality of photovoltaic string units The photovoltaic string unit includes at least N photovoltaic strings, N is an integer greater than or equal to 3, and the fault protection device includes: A plurality of protection switch units, each of the plurality of protection switch units includes a plurality of protection switches, and each protection switch unit is adapted to correspond to one of the plurality of photovoltaic string units. connected to one power conversion unit among the plurality of power conversion units to form at least two photovoltaic string branches, the photovoltaic string branches being suitable for connecting one photovoltaic string or two parallel photovoltaic strings, in, In the case where there are common positive or common negative power conversion units in the plurality of power conversion units, the protection switch units corresponding to the common positive or common negative power conversion units share the protection switches when connecting the corresponding photovoltaic string units. , so that when the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, at least three protection switches are used to separate the corresponding photovoltaic strings. 25. A combiner box for a photovoltaic power generation system, characterized by comprising a fault protection device according to claim 24, the fault protection device being configured to perform a fault on the photovoltaic power generation system when a fault occurs in the photovoltaic power generation system. The connections between the plurality of power conversion units and the plurality of photovoltaic string units are fully disconnected or partially disconnected, so that when the protection switch unit corresponding to the common positive or common negative power conversion unit is disconnected, at least three A protective switch separates the corresponding photovoltaic strings. 26. A photovoltaic power generation system, characterized in that it includes a plurality of photovoltaic string units, each of the plurality of photovoltaic string units includes at least N photovoltaic strings, and N is greater than or equal to 3. Integer, the photovoltaic power generation system also includes: The inverter according to any one of claims 1-23; or A fault protection device according to claim 24; or The combiner box according to claim 25.