CN121417330A - Photovoltaic energy storage inverter, control method thereof and photovoltaic energy storage power generation system - Google Patents

Abstract

The application provides a photovoltaic energy storage inverter, a control method thereof and a photovoltaic energy storage power generation system, and relates to the technical field of energy sources, so that the operation efficiency of the photovoltaic energy storage power generation system is improved, and the generated energy loss is avoided. The photovoltaic energy storage inverter comprises a direct current bus, an inverter circuit and a controller. The direct current bus is connected with the inverter circuit and used for transmitting direct current of the photovoltaic array to the inverter circuit. The direct current bus is also used for connecting the energy storage device so as to transmit direct current of the energy storage device to the inverter circuit. The inverter circuit is used for converting direct current of the photovoltaic array or the energy storage device into alternating current and transmitting the alternating current to a power grid or a load. The controller is used for controlling the energy storage device to stop working and then controlling the bus voltage of the direct current bus to be reduced under the condition that the output power of the photovoltaic array is larger than or equal to the load power and the charge state of the energy storage device is larger than or equal to a first preset threshold value, wherein the bus voltage is the absolute value of the voltage difference value between the positive electrode of the direct current bus and the negative electrode of the direct current bus.

Description

Photovoltaic energy storage inverter, control method thereof and photovoltaic energy storage power generation system

Technical Field

The application relates to the technical field of energy, in particular to a photovoltaic energy storage inverter, a control method thereof and a photovoltaic energy storage power generation system.

Background

Along with the continuous popularization of renewable energy source application, the application rate of the photovoltaic energy storage power generation system in the scenes of household use, self-home consumption, small-sized business and the like is continuously improved. The direct current bus coupling photovoltaic energy storage power generation system has been paid attention to widely because of the advantages of compact structure, high efficiency, suitability for off-grid application and the like. In such systems, the dc bus of the photovoltaic energy storage inverter is typically connected to an energy storage device and other dc loads. Therefore, energy control of the photovoltaic energy storage power generation system can be achieved by adjusting the voltage of the direct current bus.

The common dc bus voltage control strategy is complex to implement and maintains a high dc bus voltage in some modes of operation. The high-voltage operation state easily causes the overlarge pressure difference between the direct-current side and the alternating-current side of the photovoltaic energy storage inverter, and further triggers the protective action to limit the output power of the photovoltaic energy storage power generation system, so that the operation efficiency of the photovoltaic energy storage power generation system is reduced. Meanwhile, the high-voltage running state can further aggravate the loss of the photovoltaic energy storage inverter, and the ring temperature rise is caused, so that the running efficiency of the photovoltaic energy storage power generation system is further reduced, and the generated energy loss is caused.

Therefore, how to improve the operation efficiency of the photovoltaic energy storage power generation system to avoid the power generation loss becomes a problem to be solved.

Disclosure of Invention

The application provides a photovoltaic energy storage inverter, a control method thereof and a photovoltaic energy storage power generation system, which are used for improving the operation efficiency of the photovoltaic energy storage power generation system so as to avoid the loss of generated energy.

In order to achieve the above purpose, the embodiment of the present application adopts the following technical scheme:

In a first aspect, a photovoltaic energy storage inverter is provided that includes a dc bus, an inverter circuit, and a controller. The direct current bus is connected with the inverter circuit and used for transmitting direct current of the photovoltaic array to the inverter circuit. The direct current bus is also used for connecting an energy storage device so as to transmit direct current of the energy storage device to the inverter circuit. The inverter circuit is used for converting direct current of the photovoltaic array or the energy storage device into alternating current and transmitting the alternating current to a power grid or a load. The controller is used for controlling the energy storage device to stop working and then controlling the bus voltage of the direct current bus to be reduced under the condition that the output power of the photovoltaic array is larger than or equal to the load power and the charge state of the energy storage device is larger than or equal to a first preset threshold value, wherein the bus voltage is the absolute value of the voltage difference value between the positive electrode of the direct current bus and the negative electrode of the direct current bus.

According to the technical scheme, when the output power of the photovoltaic array is larger than or equal to the load power and the SOC of the energy storage device is larger than or equal to the first preset threshold, the energy storage device does not need to discharge to supply power to the load and does not need to charge. At this time, the controller in the reverse energy storage dc-to-ac converter of photovoltaic can control the energy storage device to stop working for can not carry out electric energy transmission between energy storage device and the photovoltaic array, and between energy storage device and the photovoltaic energy storage dc-to-ac converter, and under this kind of circumstances, the energy storage device stop working also can not influence the power supply of photovoltaic energy storage power generation system to the load. And then, the photovoltaic energy storage inverter can control the voltage reduction of the bus to reduce the voltage difference between the direct current side and the alternating current side of the photovoltaic energy storage inverter, so that a protection mechanism for the derating operation of the photovoltaic energy storage inverter is prevented from being triggered, the photovoltaic energy storage inverter can convert and output direct current of the photovoltaic array in a full-load state, and the condition of reducing the generated energy of a photovoltaic energy storage power generation system is avoided. Compared with the prior art that after the SOC of the energy storage device reaches 100%, the high bus voltage is still maintained, the technical scheme provided by the embodiment of the application can reduce the voltage difference between the direct current side and the alternating current side of the photovoltaic energy storage inverter, avoid the loss of the photovoltaic energy storage inverter, improve the operation efficiency of the photovoltaic energy storage power generation system and further avoid the loss of generated energy.

In addition, in the embodiment of the application, the energy storage device is controlled to stop working, and then the bus voltage is controlled to be reduced, so that the condition that the energy storage device discharges due to the reduction of the bus voltage can be avoided, and the electric quantity loss of the energy storage device can be further avoided.

With reference to the first aspect, in an implementation manner, the controller is further configured to control the energy storage device to supply power to the load and control the bus voltage to increase if the output power of the photovoltaic array is smaller than the load power after the energy storage device stops working.

Based on the technical scheme, the output power of the photovoltaic array is smaller than the load power, which means that the load power is larger at the moment, the electric energy provided by the photovoltaic array is smaller than the electric energy consumed by the load, and the energy storage device is required to discharge to supply power to the load. In this case, the energy storage device is controlled to supply power to the load, and the bus voltage is controlled to rise, so that the photovoltaic energy storage power generation system can be ensured to stably supply power to the load.

With reference to the first aspect, in an implementation manner, the controller is further configured to control the bus voltage to increase before the energy storage device stops working and when the state of charge of the energy storage device is less than or equal to a second preset threshold, where the second preset threshold is less than the first preset threshold.

Based on the above technical solution, the energy storage device may be in a charged state before the energy storage device stops working. And under the condition that the charge state of the energy storage device is smaller than or equal to a second preset threshold value, controlling the voltage of the bus to rise, and further shortening the charging time of the energy storage device, so that the energy storage device can complete charging as soon as possible. In this way, under the condition of limited illumination time, the direct current provided by the photovoltaic array can be supplied to a load or a power grid as soon as possible after the energy storage device is charged.

With reference to the first aspect, in an implementation manner, the controller is further configured to control the bus voltage to increase when the state of charge of the energy storage device is less than or equal to a second preset threshold after the energy storage device supplies power to the load, where the second preset threshold is less than the first preset threshold.

Based on the technical scheme, the energy storage device is controlled to supply power to the load, and the bus voltage is controlled to rise under the condition that the state of charge of the energy storage device is smaller than or equal to a second preset threshold value, so that the electric energy output by the energy storage device can be directly transmitted to the load under the condition that the energy storage device supplies power to the load, and the photovoltaic energy storage inverter is not required to be supplied to enable the bus voltage to rise, the electric energy loss output by the energy storage device can be further reduced, and the electric energy utilization rate of the energy storage device is further improved.

In combination with the first aspect, in one implementation manner, the controller is further configured to, when the output power of the photovoltaic array is greater than or equal to the load power and the state of charge of the energy storage device is greater than or equal to a first preset threshold, control the energy storage device to stop working after a first period of time, and then control the bus voltage to decrease, where the first period of time is greater than or equal to 5 minutes and less than or equal to 10 minutes.

Based on the technical scheme, under the condition that the controller meets the conditions, after a first period of time, the controller sequentially controls the energy storage device to stop working and the bus voltage to be reduced, so that the condition that the locking condition is temporarily met due to the fact that the photovoltaic energy storage power generation system is greatly disturbed can be eliminated, and the photovoltaic energy storage power generation system can be ensured to supply power to a load stably. And the proper first time length is set, so that the relation between the output power and the load power of the photovoltaic array can be ensured to be in a continuous stable state, and the condition that the photovoltaic energy storage inverter is triggered to operate in a derating mode due to longer maintenance time of a high-voltage state of the bus voltage can be avoided.

With reference to the first aspect, in an implementation manner, the controller is further configured to control the energy storage device to supply power to the load and control the bus voltage to increase after a second period of time passes if the output power of the photovoltaic array is less than the load power after the energy storage device stops working, where the second period of time is greater than or equal to 5 minutes and less than or equal to 10 minutes.

Based on the technical scheme, under the condition that the controller meets the conditions, after the second time, the energy storage device is controlled to supply power to the load, and the bus voltage is controlled to rise, so that the condition that the unlocking condition is temporarily met due to the fact that the photovoltaic energy storage power generation system is greatly disturbed can be eliminated, and the photovoltaic energy storage power generation system can be ensured to supply power to the load stably. And the proper second time length is set, so that the relation between the output power of the photovoltaic array and the load power can be ensured to be in a continuous stable state, and the condition that the load stops running due to insufficient power supply of the load can be avoided.

In a second aspect, there is provided a photovoltaic energy storage power generation system comprising an energy storage device and a photovoltaic energy storage inverter as described in the first aspect or any implementation of the first aspect, the photovoltaic energy storage inverter being connected to the energy storage device.

In a third aspect, a control method of a photovoltaic energy storage inverter is provided, and the control method is applied to the photovoltaic energy storage inverter, wherein the photovoltaic energy storage inverter comprises a direct current bus and an inverter circuit. The direct current bus is connected with the inverter circuit and used for transmitting direct current of the photovoltaic array to the inverter circuit. The direct current bus is also used for connecting an energy storage device so as to transmit direct current of the energy storage device to the inverter circuit. The inverter circuit is used for converting direct current of the photovoltaic array or the energy storage device into alternating current and transmitting the alternating current to a power grid or a load. The method comprises the steps of firstly controlling the energy storage device to stop working and then controlling the bus voltage of the direct current bus to be reduced under the condition that the output power of the photovoltaic array is larger than or equal to the load power and the charge state of the energy storage device is larger than or equal to a first preset threshold value, wherein the bus voltage is the absolute value of the voltage difference value between the positive electrode of the direct current bus and the negative electrode of the direct current bus.

With reference to the third aspect, in one implementation manner, the method further includes controlling the energy storage device to supply power to the load and controlling the bus voltage to increase if the output power of the photovoltaic array is smaller than the load power after the energy storage device stops working.

With reference to the third aspect, in an implementation manner, the method further includes controlling the bus voltage to increase before the energy storage device stops working and when the state of charge of the energy storage device is less than or equal to a second preset threshold, where the second preset threshold is less than the first preset threshold.

With reference to the third aspect, in an implementation manner, the method further includes controlling the bus voltage to increase after the energy storage device supplies power to the load and when a state of charge of the energy storage device is less than or equal to a second preset threshold, where the second preset threshold is less than the first preset threshold.

In combination with the third aspect, in one implementation manner, the energy storage device is controlled to stop working first, and then the bus voltage of the direct current bus is controlled to be reduced, which includes controlling the energy storage device to stop working first after a first duration passes when the output power of the photovoltaic array is greater than or equal to the load power and the charge state of the energy storage device is greater than or equal to a first preset threshold, wherein the first duration is greater than or equal to 5 minutes and less than or equal to 10 minutes.

In combination with the third aspect, in one implementation manner, controlling the energy storage device to supply power to the load and controlling the bus voltage to increase includes controlling the energy storage device to supply power to the load and controlling the bus voltage to increase after a second period of time passes if the output power of the photovoltaic array is less than the load power after the energy storage device stops working, wherein the second period of time is greater than or equal to 5 minutes and less than or equal to 10 minutes.

It can be appreciated that the above-provided control method of any photovoltaic energy storage inverter and photovoltaic energy storage power generation system can achieve the beneficial effects corresponding to those of the photovoltaic energy storage inverter provided above, and will not be described herein.

Drawings

Fig. 1 is a schematic diagram of an application scenario of a photovoltaic energy storage inverter provided in an embodiment of the present application;

fig. 2 is a schematic diagram of an application scenario of another photovoltaic energy storage inverter according to an embodiment of the present application;

fig. 3 is a schematic power flow diagram of a self-generating mode of the photovoltaic energy storage power generation system according to an embodiment of the present application;

fig. 4 is a schematic structural diagram of a photovoltaic energy storage inverter according to an embodiment of the present application;

fig. 5 is a flowchart of a control method of a photovoltaic energy storage inverter according to an embodiment of the present application;

Fig. 6 is a flowchart of another control method of a photovoltaic energy storage inverter according to an embodiment of the present application;

fig. 7 is a schematic diagram of a process for locking and unlocking an energy storage device according to an embodiment of the present application.

Detailed Description

The making and using of the various embodiments are discussed in detail below. It should be appreciated that the numerous applicable inventive concepts provided by the present application may be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the application and technology, and do not limit the scope of the application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

Each circuit or other component may be described or referred to as "for" performing one or more tasks. In this case, "for" is used to connote structure by indicating that circuitry/components includes structure (e.g., circuitry) that performs one or more tasks during operation. Thus, a given circuit/component may be said to be used to perform that task even when the circuit/component is not currently operational (e.g., not open). Circuits/components used with the term "for" include hardware, such as circuitry to perform operations, etc.

In the present application, the words "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.

The following description first describes the background art related to the embodiments of the present application with reference to the drawings.

Fig. 1 is a schematic diagram of an application scenario of a photovoltaic energy storage inverter 100 according to an embodiment of the present application. The photovoltaic energy storage inverter 100 is applied to the photovoltaic energy storage power generation system 200, and the photovoltaic energy storage power generation system 200 further comprises an energy storage device 300 connected with the photovoltaic energy storage inverter 100. Specifically, the dc bus of the photovoltaic energy storage inverter 100 is connected to the energy storage device 300. The photovoltaic energy storage inverter 100 may also be simply referred to as a photovoltaic inverter.

In one example, as shown in fig. 1 (a), the dc side of the photovoltaic energy storage inverter 100 is used to connect the photovoltaic array 400 and the ac side of the photovoltaic energy storage inverter 100 is used to connect the grid 500 or the load 600. When the photovoltaic array 400 includes a plurality of photovoltaic modules, the plurality of photovoltaic modules may be connected in series or in parallel, or some of the plurality of photovoltaic modules may be connected in series and the rest of the plurality of photovoltaic modules may be connected in parallel.

During the daytime, the photovoltaic array 400 is used to provide direct current to the photovoltaic energy storage inverter 100 and the energy storage device 300, the photovoltaic energy storage inverter 100 is used to convert the direct current into alternating current and transmit the alternating current to the grid 500 or the load 600, and the energy storage device 300 is used to receive the direct current and charge. At night, the photovoltaic array 400 cannot output direct current based on solar energy, the energy storage device 300 is used to provide direct current to the photovoltaic energy storage inverter 100, and the photovoltaic energy storage inverter 100 is used to convert the direct current into alternating current and transmit the alternating current to the grid 500 or the load 600.

In another example, as shown in (b) of fig. 1, the photovoltaic energy storage power generation system 200 further includes a first direct current-direct current (direct current direct current, DCDC) converter 210 and a second DCDC converter 220. Illustratively, the first DCDC converter 210 is connected between the photovoltaic energy storage inverter 100 and the photovoltaic array 400, and is configured to convert the dc power of the photovoltaic array 400 into a voltage and transmit the voltage to the photovoltaic energy storage inverter 100. The second DCDC converter 220 is connected between the photovoltaic energy storage inverter 100 and the energy storage device 300, and is configured to convert the dc power of the energy storage device 300 into a voltage and transmit the voltage to the photovoltaic energy storage inverter 100. The first DCDC converter 210 and the second DCDC converter 220 are further configured to convert the direct current of the photovoltaic array 400 into voltage, and then transmit the voltage to the energy storage device 300 to charge the energy storage device 300. The first DCDC converter may also be referred to as an optimizer, and may also be used to implement maximum power point tracking (maximum power point tracking, MPPT) of the photovoltaic array 400, i.e. by dynamically adjusting the voltage and current parameters of the photovoltaic array 400, it is ensured that the photovoltaic array 400 always maintains an optimal output state when the illumination intensity changes.

Fig. 2 is a schematic diagram of an application scenario of another photovoltaic energy storage inverter 100 according to an embodiment of the present application. The photovoltaic energy storage inverter 100 may also be applied to a micro grid system 700, the micro grid system 700 further comprising an energy storage device 300 connected to the photovoltaic energy storage inverter 100, and a converter 710 connected to the energy storage device 300. Specifically, the dc bus of the photovoltaic energy storage inverter 100 is connected to the energy storage device 300.

Illustratively, the dc side of the photovoltaic energy storage inverter 100 is used to connect to the photovoltaic array 400, the ac side of the photovoltaic energy storage inverter 100 is used to connect to the grid 500 or the load 600, and the photovoltaic energy storage inverter 100 is used to convert the dc power of the photovoltaic array 400 into ac power and then transmit the ac power to the grid 500 or the load 600. One end of the energy storage device 300 is connected with the direct current side of the photovoltaic energy storage inverter 100, the other end of the energy storage device 300 is connected with the power grid 500 or the load 600 through the converter 710, and the converter 710 is used for converting direct current of the energy storage device 300 into alternating current and transmitting the alternating current to the power grid 500 or the load 600.

By way of example, and not limitation, embodiments of the present application are described with respect to a photovoltaic energy storage power generation system.

In the photovoltaic energy storage power generation system 200 described in fig. 1, the dc bus of the photovoltaic energy storage inverter 100 is generally connected to the energy storage device 300 and other dc loads, and thus, energy control of the photovoltaic energy storage power generation system 200 can be achieved by adjusting the dc bus voltage.

The common dc bus voltage control strategy is complex to implement and maintains a high dc bus voltage in some modes of operation. For example, in the forced charging mode, forced charging of energy storage device 300 is achieved by raising the dc bus voltage to BaseBus +2Δ+2comp. For another example, in the forced discharge mode, the forced discharge of the energy storage device 300 is achieved by reducing the dc bus voltage to BaseBus +Δ. In this way, by combining different bus voltage thresholds and logic decisions, the photovoltaic energy storage power generation system 200 can be switched between various states, such as power generation of the photovoltaic array 400, charging of the energy storage device 300, and discharging of the energy storage device 300. Wherein BaseBus denotes a charging base bus voltage, and Δ and comp denote different voltage offsets, respectively.

However, this control method based on a fixed voltage threshold has the following problems in actual operation. For example, taking a 12kW three-phase four-wire photovoltaic energy storage inverter and an energy storage device with the model number S1 as an example, by adopting the above bus voltage control strategy, the dc bus voltage of the photovoltaic energy storage inverter can be raised to 780V or more. After the state of charge (SOC) of the energy storage device 300 reaches 100%, if the high bus voltage is still maintained, the voltage difference between the input side of the photovoltaic array 400 and the dc side of the photovoltaic energy storage inverter 100 will be too large. This high voltage difference is very likely to trigger the built-in protection mechanism of the photovoltaic energy storage inverter 100, resulting in de-rated operation of the photovoltaic energy storage inverter 100 and limited output power, reducing the operating efficiency of the photovoltaic energy storage power generation system 200. Meanwhile, the operation state with the higher voltage difference can further increase the loss of the photovoltaic energy storage inverter 100, and lead to high ring temperature rise, further reduce the operation efficiency of the photovoltaic energy storage power generation system 200, and cause the loss of the generated energy.

Fig. 3 is a schematic power flow diagram of a self-generating mode of the photovoltaic energy storage power generation system according to an embodiment of the present application. The energy storage device discharges to supply power to the load, the energy storage device stands by to indicate that the energy storage device is neither charged nor discharged, and the energy storage device charges to supply power to the energy storage device through the photovoltaic array.

Before time T1, the energy storage device discharges to supply power to the load under the condition that the output power of the photovoltaic array is zero and smaller than the load power. Until time T1, the soc=0% of the energy storage device, and the energy storage device enters a standby state.

And between the time T1 and the time T2, the power grid supplies power to the load under the condition that the output power of the photovoltaic array is zero and less than the load power, and supplies power to the load together with the photovoltaic array under the condition that the output power of the photovoltaic array is greater than zero and less than the load power. At this time, the photovoltaic array does not have redundant electric energy to charge the energy storage device, and the energy storage device is still in a standby state.

And between the time T2 and the time T3, the output power of the photovoltaic array is larger than the load power, the photovoltaic array supplies power to the load and transmits redundant electric energy to the energy storage device to supply power, the energy storage device enters a charging state from a standby state until the time T3, the SOC of the energy storage device is=100%, and the energy storage device enters the standby state from the charging state.

And between the time T3 and the time T4, the output power of the photovoltaic array is larger than the load power, the photovoltaic array supplies power to the load, and the redundant electric energy is transmitted to the power grid with rated power. And until the time T4, the output power of the energy storage photovoltaic array is smaller than or equal to the load power, and the energy storage device enters a discharging state from a standby state.

After time T4, the energy storage device discharges to power the load in the event that the output power of the photovoltaic array is less than the load power and gradually decreases to zero.

Referring to fig. 1, as shown in fig. 3, in the case of soc=100% of the energy storage device 300 (e.g. from time T3 to time T4) in the self-power mode of the photovoltaic power generation system, the operation state of the higher voltage difference triggers the derating operation of the photovoltaic energy storage inverter 100, so that the photovoltaic energy storage inverter 100 cannot feed the surplus photovoltaic power into the grid 500 with the rated power. This phenomenon directly results in unnecessary "light rejection" behavior, further reducing the operating efficiency of the photovoltaic energy storage power generation system 200, resulting in power generation loss.

In view of this, embodiments of the present application provide a photovoltaic energy storage inverter, a control method thereof, and a photovoltaic energy storage power generation system, so as to control an operation state of an energy storage device and a bus voltage according to a relationship between output power and load power of a photovoltaic array and a state of charge of the energy storage device, thereby avoiding a problem of reduced operation efficiency of the photovoltaic energy storage power generation system caused by triggering derated operation of the photovoltaic energy storage inverter.

The following describes the technical solution provided by the embodiment of the present application in detail with reference to fig. 4 and 5.

In an embodiment, as shown in fig. 4, a schematic structural diagram of a photovoltaic energy storage inverter according to an embodiment of the present application is shown. The photovoltaic energy storage inverter 100 includes a dc bus, an inverter circuit 110, and a controller 120.

In a first example, as shown in fig. 4 (a), a boost circuit 130 may also be included in the photovoltaic energy storage inverter 100.

One end of the boost circuit 130 is used for connecting the photovoltaic array 400, and the other end of the boost circuit 130 is connected with the inverter circuit 110 through a direct current bus. For example, two input terminals of the boost circuit 130 are respectively used for connecting the positive pole pv+ and the negative pole PV-of the photovoltaic array 400, and two output terminals of the boost circuit 130 are respectively connected with the inverter circuit 110 through the positive pole bus+ and the negative pole BUS-of the direct current BUS. The boost circuit 130 is configured to perform voltage conversion on dc power of the photovoltaic array 400, and the dc bus is configured to transmit the dc power subjected to voltage conversion to the inverter circuit 110.

The dc bus is also used to connect the energy storage device 300. For example, the positive bus+ of the dc BUS is connected to the positive electrode+ of the energy storage device 300, and the negative BUS-of the dc BUS is connected to the negative electrode of the energy storage device 300. The dc bus may transmit the dc power of the energy storage device 300 to the inverter circuit 110, or the dc bus may transmit the dc power converted by the voltage to the energy storage device 300. The process of transmitting the dc power of the energy storage device 300 to the inverter circuit 110 may be referred to as discharging the energy storage device 300, and the process of transmitting the dc power converted by the voltage to the energy storage device 300 by the dc bus may be referred to as charging the energy storage device 300.

The inverter circuit 110 is used for converting direct current of the photovoltaic array 400 or direct current of the energy storage device 300 into alternating current and transmitting the alternating current to the power grid 500 or the load 600. For example, two input terminals of the inverter circuit 110 are connected to a positive bus+ and a negative BUS of the direct current BUS, respectively, and an output terminal of the inverter circuit 110 is used to connect to the power grid 500 or the load 600 to supply power to the power grid 500 or the load 600.

The circuit topologies of the booster circuit 130 and the inverter circuit 110 described above can be referred to those in the related art. For example, the boost circuit 130 may include a capacitor C, an inductance L, a diode D, and a switching tube Q, the connection relationship of the devices in the boost circuit 130 may refer to (a) in fig. 4, and the inverter circuit 110 may be a half-bridge inverter circuit or a full-bridge inverter circuit, which is not limited in particular in the embodiment of the present application.

In a second example, as shown in fig. 4 (b), the boost circuit 130 may not be included in the photovoltaic energy storage inverter 100.

The dc bus is used to connect to the photovoltaic array 400 through the first DCDC converter 210, and the dc bus is connected to the inverter circuit 110. The first DCDC converter 210 converts the voltage of the dc power of the photovoltaic array 400, and then transmits the dc power to the inverter circuit 110 through a dc bus.

The dc bus is also used to connect the second DCDC converter 220 and the energy storage device 300. The second DCDC converter 220 is configured to convert the dc voltage of the energy storage device 300 into a voltage and then transmit the voltage to the inverter circuit 110 through a dc bus, or the second DCDC converter 220 is configured to convert the dc voltage of the photovoltaic array 400 into a voltage and then transmit the voltage to the energy storage device 300 through a dc bus.

The inverter circuit 110 is used for converting direct current of the photovoltaic array 400 or direct current of the energy storage device 300 into alternating current and transmitting the alternating current to the power grid 500 or the load 600.

As shown in fig. 5, in the case where the output power of the photovoltaic array 400 is greater than or equal to the load power and the SOC of the energy storage device 300 is greater than or equal to the first preset threshold, the controller 120 is configured to execute step S801.

S801, firstly controlling the energy storage device 300 to stop working, and then controlling the BUS voltage of the direct current BUS to be reduced, wherein the BUS voltage is the absolute value of the voltage difference between the positive bus+ of the direct current BUS and the negative BUS of the direct current BUS.

Wherein, the output power of the photovoltaic array 400 is greater than or equal to the load power, which means that the electrical energy provided by the photovoltaic array 400 is greater than the electrical energy consumed by the load 600, and the energy storage device 300 is not required to discharge to supply power to the load 600. An SOC of the energy storage device 300 that is greater than or equal to the first preset threshold indicates that the energy storage device 300 is charged or has been charged, and the energy storage device 300 does not need to receive power from the photovoltaic array 400.

In addition, the magnitude relationship between the output power and the load power of the photovoltaic array 400 is compared based on the same time. For example, at time T2 shown in fig. 3, the output power of the photovoltaic array 400 is equal to the load power, and at time T3 shown in fig. 3, the output power of the photovoltaic array 400 is greater than the load power. The load power at time T3 is not comparable to the output power of the photovoltaic array 400 at time T2.

Furthermore, the control bus voltage reduction means that the control bus voltage is reduced to a voltage value that can enable the photovoltaic energy storage inverter 100 to operate at full capacity, so as to avoid the protection mechanism that the photovoltaic energy storage inverter 100 triggers the derating operation due to the bus voltage being too high. The reduced bus voltage may be greater than or equal to the minimum charging voltage of energy storage device 300.

For example, the input voltage of the dc side of the photovoltaic energy storage inverter 100 is 400V, the power is 6.4kW, the ac output of the ac side of the photovoltaic energy storage inverter 100 is 230V, the power of the three-phase ac balance grid-connected output is 12kW, and when the soc=100% of the energy storage device 300 is set to 780V, the controller 120 controls the bus voltage to be reduced to 710V, so that the derating operation of the photovoltaic energy storage inverter 100 can be avoided, and the photovoltaic energy storage inverter 100 can continue to output the ac at full power.

The first preset threshold is related to the actual operation condition of the photovoltaic energy storage power generation system 200, which is not specifically limited in the embodiment of the present application. For example, the first preset threshold may be any value greater than or equal to 90% and less than or equal to 100%. For example, the first preset threshold may be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or 100%.

If the first preset threshold is equal to 90%, the controller 120 may control the energy storage device 300 to stop working when the output power of the photovoltaic array 400 is greater than or equal to the load power and the SOC of the energy storage device 300 is greater than or equal to 90%. Or the first preset threshold value is equal to 99%, and the controller 120 may control the energy storage device 300 to stop working when the output power of the photovoltaic array 400 is greater than or equal to the load power and the SOC of the energy storage device 300 is equal to or greater than 99%. Still alternatively, the first preset threshold is equal to 100%, and when the output power of the photovoltaic array 400 is greater than or equal to the load power and the soc=100% of the energy storage device 300, the controller 120 may control the energy storage device 300 to stop working.

The control of the energy storage device 300 to stop may also be referred to as controlling the energy storage device 300 to latch, and correspondingly, if the condition that the output power of the photovoltaic array 400 is greater than or equal to the load power and the SOC of the energy storage device 300 is greater than or equal to the first preset threshold is satisfied, the control may also be referred to as simply satisfying the latch condition. For example, the controller 120 may output a lockout command to the energy storage device 300, which may be used to instruct the energy storage device 300 to cease operation. With the energy storage device 300 latched, the photovoltaic energy storage power generation system 200 may be considered a pure photovoltaic power generation system, or referred to as a pure photovoltaic power generation system.

As shown in fig. 5, in the case where the lock condition is not satisfied, the controller 120 does not perform an operation until it is detected that the lock condition is satisfied, and the controller 120 performs the above-described step S801.

In the embodiment of the present application, in the case that the output power of the photovoltaic array 400 is greater than or equal to the load power and the SOC of the energy storage device 300 is greater than or equal to the first preset threshold, it means that the energy storage device 300 does not need to discharge to supply power to the load 600 and the energy storage device 300 does not need to be charged. At this time, the controller 120 in the photovoltaic inverse energy storage inverter may control the energy storage device 300 to stop working, so that no electric energy is transmitted between the energy storage device 300 and the photovoltaic array 400 and between the energy storage device 300 and the photovoltaic energy storage inverter 100, and in this case, the stop of the energy storage device 300 will not affect the power supply of the photovoltaic energy storage power generation system 200 to the load 600. After that, the photovoltaic energy storage inverter 100 may control the busbar voltage to decrease, so as to decrease the voltage difference between the dc side and the ac side of the photovoltaic energy storage inverter 100, thereby avoiding triggering a protection mechanism for derating the photovoltaic energy storage inverter 100, so that the photovoltaic energy storage inverter 100 can convert and output the direct current of the photovoltaic array 400 in a full load state, and avoiding the occurrence of the situation of decreasing the generated energy of the photovoltaic energy storage power generation system 200. Compared with the prior art that after the SOC of the energy storage device 300 reaches 100%, the high bus voltage is still maintained, the technical scheme provided by the embodiment of the application can reduce the voltage difference between the direct current side and the alternating current side of the photovoltaic energy storage inverter 100, avoid the loss of the photovoltaic energy storage inverter 100, improve the operation efficiency of the photovoltaic energy storage power generation system 200, and further avoid the loss of the generated energy.

In addition, in the embodiment of the present application, the energy storage device 300 is controlled to stop working first, and then the bus voltage is controlled to decrease, so that the situation that the energy storage device 300 discharges due to the decrease of the bus voltage can be avoided, and the electric quantity loss of the energy storage device 300 can also be further avoided.

In the case where the photovoltaic energy storage power generation system 200 is greatly disturbed, for example, the light intensity of the photovoltaic array 400 suddenly drops due to shielding, or the load power drops greatly due to switching of the load 600, or the load power suddenly increases due to adding a new load 600, the magnitude relationship between the output power of the photovoltaic array 400 and the load power may be suddenly changed. In this case, controlling the energy storage device 300 to latch may directly affect the power supply of the direct photovoltaic energy storage power generation system 200 to the load 600. Where "throw" refers to the load 600 accessing the grid 500 and "switch" refers to the load 600 disconnecting from the grid 500.

In view of this, in one embodiment, when the output power of the photovoltaic array 400 is greater than or equal to the load power and the state of charge of the energy storage device 300 is greater than or equal to the first preset threshold, the controller 120 is further configured to control the energy storage device 300 to stop working after the first period of time elapses, and then control the bus voltage to decrease.

For example, in the case that the above-mentioned locking condition is detected, the controller 120 may further sequentially control the energy storage device 300 to stop operating and the bus voltage to decrease after the first period of time. In this way, the situation that the blocking condition is temporarily satisfied due to the large disturbance of the photovoltaic energy storage power generation system 200 can be eliminated, so that the photovoltaic energy storage power generation system 200 can be ensured to stably supply power to the load 600.

The first time period is greater than or equal to 5 minutes and less than or equal to 10 minutes. The first duration may be, for example, any value between 5 minutes and 10 minutes. For example, the first duration may be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes. If the first time period is less than 5 minutes, the relationship between the output power and the load power of the photovoltaic array 400 cannot be ensured to be in a continuous stable state, and if the first time period is greater than 10 minutes, the high-voltage state of the bus voltage is maintained for a long time, so that the photovoltaic energy storage inverter 100 is triggered to operate in a derated mode.

In one embodiment, as shown in fig. 6, after the energy storage device 300 stops working, if the output power of the photovoltaic array 400 is smaller than the load power, the controller 120 is further configured to execute step S802.

S802, controlling the energy storage device 300 to supply power to the load 600, and controlling the bus voltage to rise.

The output power of the photovoltaic array 400 is smaller than the load power, which means that the load power is larger at this time, the power provided by the photovoltaic array 400 is smaller than the power consumed by the load 600, and the energy storage device 300 is required to discharge to supply power to the load 600.

The control bus voltage increase may be a voltage value before the control bus voltage is restored to the step-down voltage, or may be a voltage threshold at which the control bus voltage increases to a voltage that does not trigger the derating operation. The embodiment of the present application is not particularly limited thereto.

Controlling the energy storage device 300 to power the load 600 may also be referred to as controlling the energy storage device 300 to unlatch, or controlling the energy storage device 300 to unlatch. Accordingly, if the condition that the output power of the photovoltaic array 400 is smaller than the load power is satisfied, the unlocking condition may be simply satisfied. For example, the controller 120 may output an unlock command to the energy storage device 300, which may be used to instruct the energy storage device 300 to power the load 600, i.e., the energy storage device 300 begins to operate. In the event that the unlock condition is met, it indicates that the energy storage device 300 is required to discharge power to the load 600. At this time, the controller 120 may control the energy storage device 300 to start operating, so that it can be ensured that the photovoltaic energy storage power generation system 200 can stably supply power to the load 600.

As shown in fig. 6, when the energy storage device 300 is locked and the unlock condition is not satisfied, the controller 120 does not perform the operation until it is detected that the unlock condition is satisfied, and the controller 120 performs the above-described step S802.

In one embodiment, after the energy storage device 300 stops operating, if the output power of the photovoltaic array 400 is less than the load power, the controller 120 is further configured to control the energy storage device 300 to supply power to the load 600 and control the bus voltage to increase after the second period of time elapses.

For example, in the case that the above-mentioned unlocking condition is detected, the controller 120 may further control the energy storage device 300 to supply power to the load 600 after the second period of time elapses, and control the bus voltage to rise. In this way, the situation that the unlocking condition is temporarily satisfied due to the large disturbance of the photovoltaic energy storage power generation system 200 can be eliminated, so that the photovoltaic energy storage power generation system 200 can be ensured to stably supply power to the load 600.

The second time period is greater than or equal to 5 minutes and less than or equal to 10 minutes. The second time period may be, for example, any value between 5 minutes and 10 minutes. For example, the second time period may be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes. If the second period is less than 5 minutes, the relationship between the output power of the photovoltaic array 400 and the load power cannot be ensured to be in a continuous stable state, and if the second period is longer than 10 minutes, insufficient power supply to the load 600 is caused, so that the load 600 stops running.

In addition, setting the first duration and the second duration can also avoid the situation that the energy storage device 300 is frequently controlled to be locked or unlocked due to the fact that the locking condition or the unlocking condition is temporarily met, so that equipment damage caused by frequent locking or unlocking of the energy storage device 300 is avoided.

After the unlocking condition is satisfied, the sequence of unlocking the energy storage device 300 and increasing the bus voltage is not specifically limited in the embodiment of the present application. In a first example, the controller 120 may simultaneously control the energy storage device 300 to power the load 600 and control the bus voltage rise. In a second example, the controller 120 may control the bus voltage to increase before controlling the energy storage device 300 to power the load 600. In a third example, the controller 120 may first control the energy storage device 300 to supply power to the load 600 and then control the bus voltage to rise.

The latter example may enable the energy storage device 300 to directly transfer the electrical energy output by the energy storage device 300 to the load 600 without supplying the photovoltaic energy storage inverter 100 to raise the bus voltage while powering the load 600, and may further reduce the electrical energy loss output by the energy storage device 300, as compared to the former two examples. And when the energy storage device 300 discharges to supply power to the load 600, the bus voltage is maintained at a lower level, so that the energy storage device 300 can work near the rated voltage, which is beneficial to prolonging the service life of the energy storage device 300.

Further, in a third example, the controller 120 may control the bus voltage based on the SOC of the energy storage device 300.

In one embodiment, the controller 120 is further configured to control the bus voltage to increase after the energy storage device 300 supplies power to the load 600 and when the SOC of the energy storage device 300 is less than or equal to a second preset threshold. Wherein the second preset threshold is smaller than the first preset threshold.

The second preset threshold is related to the actual operation condition of the photovoltaic energy storage power generation system 200, which is not specifically limited in the embodiment of the present application. For example, the second preset threshold may be any value (e.g., 90%) greater than or equal to 50% and less than the first preset threshold. For example, the second preset threshold may be 50%, 55%, 60%, 65%, 70%, 75%, 77%, 80%, 85%, or 89%.

If the second preset threshold is 89%, after the energy storage device 300 is unlocked and supplies power to the load 600, the controller 120 does not control the bus voltage to increase until the SOC of the energy storage device 300 is less than or equal to 89%. Or the second preset threshold is equal to 50%, and after the energy storage device 300 has been unlocked and the load 600 is powered, until the SOC of the energy storage device 300 is equal to or less than 50%, the controller 120 again controls the bus voltage to increase. Or the second preset threshold is equal to 75%, after the energy storage device 300 has been unlocked and the load 600 is powered, until the SOC of the energy storage device 300 is less than or equal to 75%, the controller 120 controls the bus voltage to increase again.

In one embodiment, as shown in fig. 6, the controller 120 is further configured to execute step S800 before the energy storage device 300 stops operating and the SOC of the energy storage device 300 is less than or equal to the second preset threshold.

And S800, controlling the voltage rise of the bus. Wherein the second preset threshold is smaller than the first preset threshold. The explanation about the second preset threshold is as described above, and will not be repeated here.

Before the energy storage device 300 stops working, the energy storage device 300 may be in a charging state, and if the SOC of the energy storage device 300 is less than or equal to the second preset threshold value, the bus voltage is controlled to be increased, so that the charging time of the energy storage device 300 can be further shortened, and the SOC of the energy storage device 300 can be charged as soon as possible. In this way, in the case of limited illumination time, the photovoltaic array 400 can supply power to the grid 500 or the load 600 as soon as possible after the energy storage device 300 is charged.

As shown in fig. 6, the controller 120 does not perform the operation step S800 before the energy storage device 300 stops operating and the SOC does not satisfy the above condition.

Fig. 7 is a schematic diagram of a process for locking and unlocking an energy storage device 300 according to an embodiment of the present application. In one embodiment, when the photovoltaic energy storage inverter 100 is applied in the photovoltaic energy storage power generation system 200, the photovoltaic energy storage power generation system 200 further comprises a monitoring device 230, and the monitoring device 230 is configured to enable rapid communication between the photovoltaic energy storage inverter 100 and the energy storage device 300.

In the first step, the energy storage device 300 is controlled to be locked under the condition that the locking condition is met. Illustratively, the photovoltaic energy storage inverter 100 issues a blocking instruction to the monitoring device 230 after detecting that the blocking condition is satisfied, the monitoring device 230 issues the blocking instruction to the energy storage device 300, and the energy storage device 300 performs a blocking operation after receiving the blocking instruction. And after performing the blocking operation, feeding back to the monitoring device 230 that the blocking has been completed, and after receiving the indication signal indicating that the blocking has been completed, the monitoring device 230 feeds back to the photovoltaic energy storage inverter 100 that the energy storage device 300 is in the blocking state.

And step two, reducing the bus voltage. Illustratively, the photovoltaic energy storage inverter 100 controls the bus voltage reduction after receiving feedback that the energy storage device 300 is in the lockout state.

And thirdly, controlling the energy storage device 300 to unlock under the condition that the unlocking condition is met. Illustratively, after detecting that the unlocking condition is met, the photovoltaic energy storage inverter 100 issues an unlocking instruction to the monitoring device 230, the monitoring device 230 issues the unlocking instruction to the energy storage device 300, and the energy storage device 300 performs the unlocking operation after receiving the locking instruction. And after the unlocking operation is performed, feeding back to the monitoring device 230 that the unlocking is completed, and after receiving the indication signal indicating that the unlocking is completed, the monitoring device 230 feeds back to the photovoltaic energy storage inverter 100 that the energy storage device 300 is in the unlocked state.

And step four, raising the bus voltage. For example, the photovoltaic energy storage inverter 100 may control the bus voltage to increase after issuing the unlock command and before receiving no information of the unlock state feedback. The photovoltaic energy storage inverter 100 may also control the increase of the bus voltage after receiving the feedback information of the unlock state.

The embodiment of the application also provides a photovoltaic energy storage power generation system, which comprises an energy storage device and a photovoltaic energy storage inverter, wherein the photovoltaic energy storage inverter is connected with the energy storage device. The structure of the photovoltaic energy storage inverter may be as described above.

The embodiment of the application also provides a control method of the photovoltaic energy storage inverter, which can be applied to the photovoltaic energy storage inverter comprising a direct current bus and an inverter circuit, and the structure of the photovoltaic energy storage inverter can be referred to the description above. The method comprises the steps of firstly controlling the energy storage device to stop working and then controlling the bus voltage of the direct current bus to be reduced under the condition that the output power of the photovoltaic array is larger than or equal to the load power and the charge state of the energy storage device is larger than or equal to a first preset threshold value, wherein the bus voltage is the absolute value of the voltage difference value between the positive electrode of the direct current bus and the negative electrode of the direct current bus.

In one embodiment, the method further comprises controlling the energy storage device to supply power to the load and controlling the bus voltage to rise if the output power of the photovoltaic array is less than the load power after the energy storage device stops operating.

In one embodiment, the method further comprises controlling the bus voltage to rise before the energy storage device stops working and when the state of charge of the energy storage device is less than or equal to a second preset threshold, wherein the second preset threshold is less than the first preset threshold.

In one embodiment, the method further comprises controlling the bus voltage to rise after the energy storage device supplies power to the load and if the state of charge of the energy storage device is less than or equal to a second preset threshold, wherein the second preset threshold is less than the first preset threshold.

In one embodiment, the control of the energy storage device to stop working and then the control of the reduction of the bus voltage of the direct current bus includes controlling the energy storage device to stop working and then the control of the reduction of the bus voltage after a first period of time passes when the output power of the photovoltaic array is greater than or equal to the load power and the state of charge of the energy storage device is greater than or equal to a first preset threshold, wherein the first period of time is greater than or equal to 5 minutes and less than or equal to 10 minutes.

In one embodiment, controlling the energy storage device to supply power to the load and controlling the bus voltage to rise includes controlling the energy storage device to supply power to the load and controlling the bus voltage to rise after a second period of time passes if the output power of the photovoltaic array is less than the load power after the energy storage device stops working, wherein the second period of time is greater than or equal to 5 minutes and less than or equal to 10 minutes.

It can be understood that all relevant contents related to the embodiments of the photovoltaic energy storage power generation system and all relevant contents related to the embodiments of the control method may be cited in the embodiments of the photovoltaic energy storage inverter, and the embodiments of the present application are not described herein.

It should be noted that the above description is only a specific embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (13)

1. The photovoltaic energy storage inverter is characterized by comprising a direct current bus, an inverter circuit and a controller;

the direct current bus is connected with the inverter circuit and used for transmitting direct current of the photovoltaic array to the inverter circuit;

The direct current bus is also used for connecting an energy storage device so as to transmit direct current of the energy storage device to the inverter circuit;

The inverter circuit is used for converting direct current of the photovoltaic array or the energy storage device into alternating current and transmitting the alternating current to a power grid or a load;

And the controller is used for controlling the energy storage device to stop working and then controlling the bus voltage of the direct current bus to be reduced under the condition that the output power of the photovoltaic array is larger than or equal to the load power and the charge state of the energy storage device is larger than or equal to a first preset threshold value, wherein the bus voltage is the absolute value of the voltage difference value between the positive electrode of the direct current bus and the negative electrode of the direct current bus.

2. The photovoltaic energy storage inverter of claim 1 wherein,

And the controller is also used for controlling the energy storage device to supply power to the load and controlling the bus voltage to rise if the output power of the photovoltaic array is smaller than the load power after the energy storage device stops working.

3. The photovoltaic energy storage inverter of claim 1 or 2, wherein,

The controller is further configured to control the bus voltage to increase before the energy storage device stops working and when the state of charge of the energy storage device is less than or equal to a second preset threshold, where the second preset threshold is less than the first preset threshold.

4. The photovoltaic energy storage inverter of claim 1 or 2, wherein the controller is further configured to control the bus voltage to rise after the energy storage device supplies power to the load and if the state of charge of the energy storage device is less than or equal to the second preset threshold, wherein the second preset threshold is less than the first preset threshold.

5. The photovoltaic energy storage inverter of any of claims 1-4,

The controller is further configured to, when the output power of the photovoltaic array is greater than or equal to the load power and the state of charge of the energy storage device is greater than or equal to the first preset threshold, control the energy storage device to stop working after a first period of time, and then control the bus voltage to decrease, where the first period of time is greater than or equal to 5 minutes and less than or equal to 10 minutes.

6. The photovoltaic energy storage inverter of any of claims 1-5,

And the controller is also used for controlling the energy storage device to supply power to the load and controlling the bus voltage to rise after the energy storage device stops working if the output power of the photovoltaic array is smaller than the load power for a second time period, wherein the second time period is longer than or equal to 5 minutes and is smaller than or equal to 10 minutes.

7. A photovoltaic energy storage power generation system, characterized in that the photovoltaic energy storage power generation system comprises an energy storage device and the photovoltaic energy storage inverter of any one of claims 1-6, wherein the photovoltaic energy storage inverter is connected with the energy storage device.

8. The control method of the photovoltaic energy storage inverter is characterized by being applied to the photovoltaic energy storage inverter, wherein the photovoltaic energy storage inverter comprises a direct current bus and an inverter circuit;

the direct current bus is connected with the inverter circuit and used for transmitting direct current of the photovoltaic array to the inverter circuit;

The direct current bus is also used for connecting an energy storage device so as to transmit direct current of the energy storage device to the inverter circuit;

The inverter circuit is used for converting direct current of the photovoltaic array or the energy storage device into alternating current and transmitting the alternating current to a power grid or a load;

the method comprises the following steps:

And under the condition that the output power of the photovoltaic array is larger than or equal to the load power and the charge state of the energy storage device is larger than or equal to a first preset threshold value, controlling the energy storage device to stop working, and then controlling the bus voltage of the direct current bus to be reduced, wherein the bus voltage is the absolute value of the voltage difference value between the positive electrode of the direct current bus and the negative electrode of the direct current bus.

9. The control method according to claim 8, characterized in that the method further comprises:

And after the energy storage device stops working, if the output power of the photovoltaic array is smaller than the load power, controlling the energy storage device to supply power to the load, and controlling the bus voltage to rise.

10. The control method according to claim 8 or 9, characterized in that the method further comprises:

And controlling the bus voltage to rise before the energy storage device stops working and under the condition that the charge state of the energy storage device is smaller than or equal to a second preset threshold value, wherein the second preset threshold value is smaller than the first preset threshold value.

11. The control method according to claim 8 or 9, characterized in that the method further comprises:

And controlling the bus voltage to rise after the energy storage device supplies power to the load and under the condition that the state of charge of the energy storage device is smaller than or equal to the second preset threshold, wherein the second preset threshold is smaller than the first preset threshold.

12. The control method according to any one of claims 8 to 11, wherein the first controlling the energy storage device to stop operation and then controlling the bus voltage of the dc bus to decrease includes:

And under the condition that the output power of the photovoltaic array is larger than or equal to the load power and the charge state of the energy storage device is larger than or equal to the first preset threshold value, after a first period of time, the energy storage device is controlled to stop working, and then the bus voltage is controlled to be reduced, wherein the first period of time is larger than or equal to 5 minutes and smaller than or equal to 10 minutes.

13. A control method according to any one of claims 8-12, wherein the controlling the energy storage device to supply power to the load and controlling the bus voltage rise comprises:

And after the energy storage device stops working, if the output power of the photovoltaic array is smaller than the load power, controlling the energy storage device to supply power to the load after a second time period, and controlling the bus voltage to rise, wherein the second time period is longer than or equal to 5 minutes and is shorter than or equal to 10 minutes.