CN103529335B - A kind of low voltage crossing detection device of grid-connected photovoltaic inverter - Google Patents

Abstract

The invention provides the low voltage crossing detection device of a kind of grid-connected photovoltaic inverter, described device includes dividing potential drop adjustment module, chopper C1, chopper C2, chopper C4 and short circuit fling-cut switch；Transformator two ends are connected with electrical network respectively and are connected with described dividing potential drop adjustment module by described chopper C1；The neutral point of described transformator, described short circuit fling-cut switch, described chopper C4 and described dividing potential drop adjustment module are sequentially connected with；Described dividing potential drop adjustment module is connected with photovoltaic DC-to-AC converter by described chopper C2.This switch of assembly of the invention ingenious use, it is possible to reduce the quantity of reactor；When falling amplitude switching, tested inverter is without shutting down, and decreases the detection time, improves efficiency.

Description

A low-voltage ride-through detection device for grid-connected photovoltaic inverters

technical field

The invention relates to a detection device in the field of photovoltaic power generation, in particular to a low-voltage ride-through detection device for a grid-connected photovoltaic inverter.

Background technique

With the increasing proportion of photovoltaic power generation in electric energy, the impact of photovoltaic power generation system on the power grid can no longer be ignored. Especially in Gansu and Qinghai in the west of China, photovoltaic power generation systems are integrated into the power grid through large-scale centralized access. When the power grid fails and the voltage at the grid-connected point drops, once the photovoltaic power station is disconnected from the grid on a large scale, it may cause the collapse of the grid voltage and frequency, which will seriously affect the safe and stable operation of the grid. Therefore, large-scale photovoltaic power plants must have low-voltage ride-through capabilities.

In 2012, my country promulgated the national standard GB/T19964-2012 "Technical Regulations for Connecting Photovoltaic Power Stations to Power Systems", which clearly stipulates that when the voltage of the grid-connected point of the photovoltaic power station drops below the curve 1 in Figure 1, the photovoltaic power station can Cut off from the grid; when the grid-connected point voltage of the photovoltaic power station is above curve 1, the photovoltaic power station should ensure continuous operation without disconnecting from the grid.

Different from the wind power generation device, the low voltage ride through function of the photovoltaic system is completely realized by the photovoltaic inverter. Therefore, relevant detection equipment is required to detect the low voltage ride-through capability of the inverter. The detection device generally uses a passive reactor ground short circuit or a phase-to-phase short circuit to simulate a grid fault, as shown in the schematic diagram of the low voltage ride through detection device in Figure 2.

The reactors X ₁ and X ₂ in the figure are both air-core reactors, and the reactor X ₁ is a current-limiting reactor, which is used to limit the impact on the upper-level power grid when the device is short-circuited; X ₁ is often connected in parallel with a bypass switch. X ₂ is a short-circuit reactor. When testing the photovoltaic inverter, first disconnect S ₁ and put in a current-limiting reactor; then close S ₂ and put in a short-circuit reactor to simulate the voltage drop when the power grid fails. The percentage of voltage drop satisfies the following formula: In the formula, Z ₁ and Z ₂ are the impedance values of the reactors X ₁ and X ₂ respectively, and Z _k is the equivalent impedance of the grid.

The traditional wind power converter or photovoltaic inverter low-voltage ride-through detection device uses multiple reactors with different inductances to form different parameters X ₁ and X ₂ through series-parallel combination, thereby simulating voltage drops of different depths, and detecting The device has the following disadvantages:

(1) According to the relevant domestic and foreign photovoltaic and wind power grid-connected standards, the drop points of the low-voltage ride-through detection device should be at least 5 points, and the drop points should be as many as possible and evenly distributed. However, since the detection device cannot be equipped with many reactors, or is limited by the number of reactor taps, the detection device cannot realize multiple drop amplitudes.

(2) When it is necessary to switch the amplitude of the voltage drop, it is necessary to switch the connection mode of the reactor or switch different taps of the reactor. Generally, manual and automatic methods are used:

Manually changing the reactor parameters of the main circuit is cumbersome, time-consuming, and has certain safety hazards. It is not conducive to quickly realizing voltage drops of various amplitudes and forms, but it is relatively low in cost and occupies a small area.

The parameters of the main circuit reactor are changed in an automatic way, and the switching of the reactor tap is generally realized by switching a thyristor or a circuit breaker. The cost of the device is high and the floor space is large.

(3) Whether it is manual modification, circuit breaker switching or thyristor switching, when changing the drop amplitude, it is necessary to stop the operation of the photovoltaic inverter under test before operating, which increases additional detection time and is not conducive to the overall detection Increased efficiency.

Contents of the invention

In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a low-voltage ride-through detection device for grid-connected photovoltaic inverters. The core of the device is to use the transformer voltage divider adjustment switch (including pressure regulating switch and no-load pressure regulating switch). Clever use of the switch can not only reduce the number of reactors; the inverter under test does not need to be shut down when the drop amplitude is switched, which reduces the detection time and improves efficiency. At the same time, the cost of transformer voltage divider adjustment switches (including on-load voltage divider adjustment switches and no-load voltage divider adjustment switches) is much lower than that of high-voltage circuit breakers and thyristor switching switches, and the floor space is also small. On the whole, the overall cost and floor area of the whole device are reduced, and the healthy development of the photovoltaic industry is promoted.

The solution adopted to achieve the above purpose is:

A low-voltage ride-through detection device for a grid-connected photovoltaic inverter, the improvement of which is that the device includes a voltage division adjustment module, a circuit breaker C1, a circuit breaker C2, a circuit breaker C4, and a short-circuit switching switch;

The two ends of the transformer are respectively connected to the power grid and the voltage division adjustment module through the circuit breaker C1; the neutral point of the transformer, the short-circuit switching switch, the circuit breaker C4 and the voltage division adjustment module connected in sequence; the voltage division adjustment module is connected to the photovoltaic inverter through the circuit breaker C2.

Further, the voltage division adjustment module includes a transformer voltage division adjustment switch WL2, N reactors L (N≥3) and a transformer voltage division adjustment switch WL3 connected in series in sequence; the reactor is a multi-tap reactor, so The transformer voltage divider adjustment switches WL2 and WL3 respectively control the connected reactor L;

The gear end of the transformer voltage dividing adjustment switch WL4 is connected between the zero gear end of the transformer voltage dividing adjusting switch WL3 and the reactor, and the zero gear end of the transformer voltage dividing adjusting switch WL4 passes through the circuit breaker C2 and the circuit breaker C3 are respectively connected to the zero gear end connected to the photovoltaic inverter and the transformer voltage divider adjustment switch WL1;

The circuit breaker C4 and the circuit breaker C1 are respectively connected to the zero gear end of the transformer voltage divider adjustment switch WL1 and the transformer voltage divider adjustment switch WL5;

The first and second gears of the transformer voltage division adjustment switch WL1 and the transformer voltage division adjustment switch WL5 are cross-connected; the zero gear ends of the transformer voltage division adjustment switch WL2 and the transformer voltage division adjustment switch WL3 are respectively connected to The first gear end and the second gear end of the transformer voltage division adjustment switch WL1 are connected.

Further, the zero gears of the transformer voltage dividing adjustment switches WL1 and WL5 are respectively connected to the circuit breaker C1 and the circuit breaker C4, and the first gear and the second gear of the transformer voltage dividing adjustment switches WL1 and WL5 are crossed. connect.

Further, the transformer voltage division adjustment switch WL1 and the transformer voltage division adjustment switch WL5 are two-gear adjustment switches, and the transformer voltage division adjustment switch WL1 and the transformer voltage division adjustment switch WL5 are switched at the same time. Gear switch;

The number of gears of the transformer voltage divider adjustment switches WL2 and WL3 corresponds to the number of taps of the reactor;

The number of gears of the transformer voltage divider adjustment switch WL4 is equal to the number of reactors;

The short-circuit switching switch is a transformer voltage dividing adjustment switch with ten gears.

Further, the circuit breaker C1 , the circuit breaker C2 and the circuit breaker C4 are all AC circuit breakers; the circuit breaker C4 is a short-circuit circuit breaker.

Further, the circuit breaker C3 is an AC circuit breaker; the circuit breaker C3 is a bypass circuit breaker.

Further, the node voltage between the two reactors and the node voltage at the zero gear end of the transformer voltage divider adjustment switch WL4 are connected to the photovoltaic inverter, so as to realize the simulation of line short-circuit faults with different voltage amplitudes.

Further, the transformer voltage division adjustment switch WL2 and the transformer voltage division adjustment switch WL3 are used to switch the reactor taps of the input circuit;

The more taps of the reactor, the more gears of transformer voltage dividing adjustment switches are required, the more drop points, and the more uniform the distribution within the voltage range.

Further, the transformer voltage division regulating switch includes an on-load voltage dividing regulating switch and an off-load voltage dividing regulating switch.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The structure of the device of the present invention is simple. The traditional passive reactor detection device needs to be equipped with a current-limiting reactor and a short-circuit reactor separately, and each type of reactor needs to be equipped with multiple reactors for arrangement and combination. Each reactor of the device of the present invention can be used as a current-limiting reactor and a short-circuit reactor, reducing the number of reactors, thereby reducing the cost, volume and maintenance of the device.

(2) The device of the present invention is easy to operate, and the steps of changing the impedance in the traditional detection device in the form of a passive reactor are cumbersome, which is not conducive to quickly realizing voltage drops of various forms and amplitudes. The device of the present invention can quickly realize the drop of various amplitudes by using the gear position switching of the voltage dividing adjustment switch of the transformer, which reduces the time and workload of detection

(3) The device of the present invention switches with load. In the traditional passive reactor detection device, when switching the drop amplitude or drop type, it is necessary to cut off the power supply of the main circuit after the inverter under test is shut down. The device of the present invention utilizes the characteristics of on-load switching of the on-load voltage divider switch. When switching the drop amplitude and gear position, the inverter under test does not need to be shut down, which greatly improves the detection efficiency. If the no-load voltage divider adjustment switch is used, then Switching under load is not possible.

(4) The cost of the device of the present invention is low. The traditional passive reactor detection device uses a thyristor series valve or a high-voltage circuit breaker to switch between the drop amplitude and drop type. Circuit breakers and power electronic switches are expensive. The device of the present invention is realized by adopting the mode of shifting gears of the voltage dividing regulator switch of the transformer, and the cost is only 10% of the former, which greatly reduces the production cost of the detection device.

Description of drawings

Figure 1 is a schematic diagram of the national standard low-voltage ride-through capability requirements;

Figure 2 is a schematic diagram of a low voltage ride through detection device;

Fig. 3 is a connection diagram of a low voltage ride through detection device for a grid-connected photovoltaic inverter with 3 reactors;

Fig. 4 is a topological structure diagram of the first gear of the transformer voltage dividing adjustment switch WL1;

Fig. 5 is a topological structure diagram of the second gear of the transformer voltage dividing adjustment switch WL1;

Fig. 6 is a schematic diagram of a low-voltage ride-through detection device for a grid-connected photovoltaic inverter;

Fig. 7 is a structural diagram of the transformer voltage divider adjustment switch WL6.

detailed description

The specific embodiments of the present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 6, Figure 6 is a schematic diagram of a low-voltage ride-through detection device for a grid-connected photovoltaic inverter; the low-voltage ride-through detection device of the present invention includes a short-circuit switching switch, a circuit breaker C1, a circuit breaker C2, a circuit breaker C4 and a branch pressure regulator module. The voltage division adjustment module includes circuit breaker C3, transformer voltage division adjustment switch WL1, transformer voltage division adjustment switch WL2, transformer voltage division adjustment switch WL3, transformer voltage division adjustment switch WL4, transformer voltage division adjustment switch WL5 and N reactors L ( N is greater than or equal to 3).

One end of the transformer is connected to the power grid, and the other end is connected to the voltage division adjustment module through the circuit breaker C1. The neutral point of the transformer, the short-circuit switching switch, the circuit breaker C4 and the voltage division adjustment module are connected in sequence; the voltage division adjustment module is connected to the photovoltaic system through the circuit breaker C2. The inverter is connected. The neutral point of the transformer is connected to the zero gear end of the short-circuit switching switch WL6, one end of the circuit breaker C4 is connected to any gear of the short-circuit switching switch WL6, and the other end of the circuit breaker C4 is connected to the zero gear end of the transformer voltage divider adjustment switch WL5 connected.

The transformer voltage division adjustment switch WL2 of the voltage division adjustment module, N reactors L (N≥3) and transformer voltage division adjustment switch WL3 are connected in series in sequence; the N reactors L are all multi-tap reactors, and the transformer voltage division adjustment switch WL2 and WL3 control the connected reactor L; the gear end of the transformer voltage divider adjustment switch WL4 is respectively connected to the zero gear end of the transformer voltage divider adjustment switch WL3 and between the two reactors, and the zero end of the transformer voltage divider adjustment switch WL4 The gear end is respectively connected to the zero gear end of the photovoltaic inverter and the transformer voltage divider adjustment switch WL1 through the circuit breaker C2 and the circuit breaker C3; the circuit breaker C4 and the circuit breaker C1 are respectively connected to the transformer voltage divider adjustment switch WL1 and the transformer voltage divider adjustment The zero gear end of the switch WL5 is connected; the first gear and the second gear of the transformer voltage divider adjustment switch WL1 and the transformer voltage divider adjustment switch WL5 are cross-connected; the zero gear of the transformer voltage divider adjustment switch WL2 and the transformer voltage divider adjustment switch WL3 Terminals are respectively connected to the first gear end and the second gear end of the transformer voltage divider adjustment switch WL1.

The circuit breakers C1, C2, C3 and C4 are all AC circuit breakers, the circuit breaker C3 is a bypass circuit breaker, and the circuit breaker C4 is a short-circuit circuit breaker. There are three reactors for each reactor, which are used to control the three-phase electricity respectively, and the reactor parameters between phases are equivalent. The transformer voltage division adjustment switch WL1 and the transformer voltage division adjustment switch WL5 are two-position adjustment switches, the transformer voltage division adjustment switch WL1 and the transformer voltage division adjustment switch WL5 are coaxial switches, and the two transformer voltage division adjustment switches are combined in one At the same time, the same gear is switched at the same time, that is, both are put into 1st gear or both are put into 2nd gear at the same time.

The number of gears of the transformer voltage divider adjustment switch WL2 and WL3 corresponds to the number of taps of the reactor; the number of gears of the transformer voltage divider adjustment switch WL4 is equal to the number of reactors; the short-circuit switch WL6 is a ten-gear transformer voltage divider Adjust the switch.

The transformer voltage division adjustment switch includes an on-load voltage division adjustment switch and an off-load voltage division adjustment switch. During the test, the on-load voltage divider adjustment switch or the no-load voltage divider adjustment switch is uniformly used.

As shown in Figure 3, Figure 3 is the connection diagram of the low-voltage ride-through detection device of the grid-connected photovoltaic inverter; the number of reactors in this device is 3, and the device includes circuit breakers C1, C2, C4, and short-circuit switching switch WL6 and a voltage division adjustment module, the voltage division adjustment module includes transformer voltage division adjustment switches (WL1, WL2, WL3, WL4 and WL5), reactors (L1, L2, L3) and a circuit breaker C3.

One end of the transformer is connected to the zero gear end of the transformer voltage dividing adjustment switch WL1 through the circuit breaker C1, and the other end is connected to the power grid; the neutral point of the transformer, the short-circuit switching switch WL6, the circuit breaker C4 and the transformer voltage dividing adjustment switch WL5 are connected in sequence; The zero gear end of the transformer voltage divider adjustment switch WL4 is connected to the photovoltaic inverter through the circuit breaker C2.

Transformer voltage divider adjustment switches WL1 and WL5 are two-position adjustment switches, the first gear and second gear are cross-connected, and the transformer voltage divider adjustment switches WL2 and WL3 are respectively connected to the second gear terminal and One gear end.

Reactors L1, L2, and L3 are all four-tap reactors. Transformer voltage divider adjustment switches WL2 and WL3 are four-position adjustment switches. Transformer voltage division adjustment switches WL2, WL3 respectively control reactors L1 and L2.

The transformer voltage divider adjustment switch WL4 is a three-gear adjustment switch. The gear end of the transformer voltage divider adjustment switch WL4 is respectively connected to between the reactor L1 and L2, between the reactor L2 and L3, and to the terminal of the transformer voltage divider adjustment switch WL3. Zero position, the zero position of the transformer voltage divider adjustment switch WL4 is respectively connected to the zero position end of the photovoltaic inverter and the transformer voltage divider adjustment switch WL1 through the circuit breaker C2 and the circuit breaker C3.

The circuit breakers C1, C2, C3 and C4 are all AC circuit breakers, the circuit breaker C3 is a bypass circuit breaker, and the circuit breaker C4 is a short-circuit circuit breaker.

The transformer voltage divider adjustment switch is to complete the switching of the transformer tap without cutting off the load current, that is, to change the transformation ratio of the transformer under the premise of the transformer running with load, thereby changing the output voltage of the transformer. The transformer voltage divider adjustment switch generally adopts the method of switching in oil or air, and adopts a resistance transition structure. The switch adopts a rotary motor to complete the direct voltage regulation method of switching and operation integration, with simple structure and convenient installation and maintenance.

The characteristic of the transformer voltage divider adjustment switch is that the transformer does not need to stop running when switching. The present invention uses the characteristics of the switch to switch the taps of the transformer and the topological structure of the main circuit, so that when the low voltage ride-through detection device switches the drop amplitude, the measured photovoltaic inverter The detector does not need to stop running, which reduces the detection time and improves the detection efficiency.

As shown in Figures 4 and 5, they are respectively the topological structure diagrams of the first gear and the second gear of the transformer voltage divider adjustment switch WL1. When the circuit breaker C4 is in the closed state, when the transformer voltage divider adjustment switch WL1 is at 1 When in gear, the voltage value n1>n2>n3, where n1 is the node voltage value between reactor L1 and L2, n2 is the node reactance value between reactor L2 and L3, and n3 is the transformer voltage divider adjustment switch WL3 Node voltage value of zero gear.

When the transformer voltage divider adjustment switch WL1 is in the 2nd position, the voltage value n1'<n2'<n3', where n1' is the node voltage value between the reactor L1 and L2, and n2' is the node voltage value between the reactor L2 and L3 The node reactance value between them, n3' is the node voltage value of the zero gear of the transformer voltage divider adjustment switch WL3.

As long as the appropriate reactor parameters are selected, the voltage value n1>n2>n3>n3’>n1’>n2’ can be satisfied. The role of the transformer voltage divider adjustment switch WL4 is to connect the voltage value of the above nodes to the photovoltaic inverter to realize the simulation of line short circuit faults with different voltage amplitudes.

The transformer voltage divider adjustment switches WL2 and WL3 are four-position adjustment switches, which are used to switch the taps of the reactors input into the circuit. The more taps of the reactor, the more gears of the required OLTC, the more drop points, and it is easier to achieve uniform distribution in the voltage range.

The transformer voltage divider adjustment switch WL6 is used as a short-circuit switching switch to switch the grounding mode of the detection device. Generally, there are 10 fault modes in the power grid, as shown in Figure 7, which is a structural diagram of the transformer voltage divider adjustment switch WL6.

As shown in the line fault type table in Table 1 below, the 10-position transformer voltage divider adjustment switch can be selected to realize it.

Table 1 Line fault type table

The impedance values of the four taps of the reactor L1 are Z11, Z12, Z13, Z13 respectively, the impedance values of the four taps of the reactor L3 are Z31, Z32, Z33, Z34 respectively, and the impedance value of the reactor L2 is Z2, then the detection The relationship between the drop amplitude of the device and the non-excitation switch is shown in Table 2 below:

Table 2 Correspondence table of drop amplitudes formed by the switch positions of WL1, WL2, WL3, and WL4 of the low-voltage ride-through detection device

Note: Z _x in the table represents the equivalent impedance of the power system;

It can be seen from Table 2 that the device has 18 kinds of drop amplitudes. If the reactor tap is selected to select an appropriate value, it can ensure that the detection device has the same total short-circuit capacity and has different drop amplitudes.

The transformer voltage divider adjustment switch WL6 is used as a short-circuit switching switch to switch the grounding mode of the detection device, but when simulating a ground fault, the grounding point is generally connected to the neutral point of the secondary side of the isolation transformer in the figure.

The present invention is described in detail in conjunction with embodiment, and a kind of embodiment of the present invention is as follows:

Photovoltaic inverter testing The inverter with the largest capacity in the market is 630kW, and the access voltage level of testing laboratories is mostly 10kV. According to the relevant requirements of domestic and foreign photovoltaic standards, the device of the present invention designs a low-voltage ride-through detection device with the following scheme:

The power supply is connected to the laboratory after being stepped down by 110/10.5kV in the substation. In order to prevent the impact on the power quality of the grid, the power supply is designed to be connected to the low voltage ride-through detection device after passing through a 4MVA isolation transformer. On the premise that the parameters of the main transformer and the isolation transformer of the substation are known, the following calculation is performed first:

(1) Reactance value of main transformer in substation

Transformer parameters: 110/10.5kV short-circuit impedance Uk=10.5% capacity 31.5MVA;

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; tl</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.105</span>}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 31.5</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.333</span>}$

(2) Isolation variable reactance value:

Transformer parameters: 10/10kV d short-circuit impedance Uk=8%, capacity 4MVA

${\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.08</span>}<span\; class="notranslate">\; \&times;</span>\frac{{\mathrm{<span\; class="notranslate">\; 10</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{\mathrm{<span\; class="notranslate">\; 4</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 2</span>}$

Total system reactance X _t =2.0+0.333=2.333

Considering the reactance factor of the line, the total system impedance is estimated to be around 2.5.

When designing the reactor, the total system reactance is considered to meet various voltage drop requirements, and the drop points are evenly distributed within the range of 0% to 90%, so L1 and L2 use 5-tap reactors. According to different requirements, choose a different number of reactor taps. The parameters of the three reactors are as follows:

Reactor L1:

5-tap reactor, inductance values are 8mH, 16mH, 24mH, 32mH, 40mH

Reactor L2:

Separate reactor: 40mH

Reactor L3:

5-tap reactor, the inductance values are 72mH, 80mH, 88mH, 96mH, 104mH

The above three kinds of reactors are controlled by the transformer voltage divider adjustment switch, and the voltage drop amplitude that the detection device can generate is shown in the corresponding table of the drop amplitude of the detection device in Table 3 below:

Table 3 Correspondence table of the drop amplitude of the detection device

Note: In theory, with the increase of L1 and L3 voltage taps, more voltage drop amplitude points can be added, but due to the error of voltage drop amplitude controlled by domestic and foreign standards within ±5%, too dense drop amplitude points It is meaningless in itself, and the detection device manufactured by the scheme of this embodiment has achieved no dead zone of the voltage drop amplitude.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application rather than to limit the scope of protection thereof. Although the present application has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: After reading this application, those skilled in the art can still make various changes, modifications or equivalent replacements to the specific implementation methods of the application, but these changes, modifications or equivalent replacements are all within the protection scope of the pending claims of the application.

Claims (5)

1. A low-voltage ride-through detection device for a grid-connected photovoltaic inverter, characterized in that: the device includes a voltage division adjustment module, a circuit breaker C1, a circuit breaker C2, a circuit breaker C4 and a short-circuit switching switch; The two ends of the transformer are respectively connected to the power grid and the voltage division adjustment module through the circuit breaker C1; the neutral point of the transformer, the short-circuit switching switch, the circuit breaker C4 and the voltage division adjustment module connected in sequence; the voltage division adjustment module is connected to the photovoltaic inverter through the circuit breaker C2; The voltage division adjustment module includes a transformer voltage division adjustment switch WL2 and N reactors L connected in series, wherein N≥3 and a transformer voltage division adjustment switch WL3; the reactor is a multi-tap reactor, and the transformer Voltage division adjustment switches WL2 and WL3 respectively control the reactors L connected to each other; The gear end of the transformer voltage dividing adjustment switch WL4 is connected between the zero gear end of the transformer voltage dividing adjusting switch WL3 and the reactor, and the zero gear end of the transformer voltage dividing adjusting switch WL4 passes through the circuit breaker respectively. C2 and circuit breaker C3 are connected to the zero gear end of the photovoltaic inverter and transformer voltage divider adjustment switch WL1; The circuit breaker C4 is connected to the zero gear end of the transformer voltage divider adjustment switch WL5, and the circuit breaker C1 is connected to the zero gear end of the transformer voltage divider adjustment switch WL1; The first and second gears of the transformer voltage division adjustment switch WL1 and the transformer voltage division adjustment switch WL5 are cross-connected; the zero gear ends of the transformer voltage division adjustment switch WL2 and the transformer voltage division adjustment switch WL3 are respectively connected to The second gear end of the transformer voltage dividing adjustment switch WL1 is connected to the first gear end; The circuit breaker C1, the circuit breaker C2 and the circuit breaker C4 are all AC circuit breakers; the circuit breaker C4 is a short-circuit circuit breaker; The transformer voltage divider adjustment switch uniformly uses an on-load voltage divider regulator switch or an off-load voltage divider adjuster switch. 2. A low-voltage ride-through detection device for a grid-connected photovoltaic inverter according to claim 1, characterized in that: the transformer voltage divider adjustment switch WL1 and the transformer voltage divider adjustment switch WL5 are two-position Adjusting switches, the transformer voltage division adjustment switch WL1 and the transformer voltage division adjustment switch WL5 are switches for switching the same gear at the same time; The number of gears of the transformer voltage divider adjustment switches WL2 and WL3 is equal to the number of taps of the respectively connected reactors; The number of gears of the transformer voltage divider adjustment switch WL4 is equal to the number of reactors; The short-circuit switching switch is a transformer voltage dividing adjustment switch with ten gears. 3. A low-voltage ride-through detection device for a grid-connected photovoltaic inverter according to claim 1, wherein the circuit breaker C3 is an AC circuit breaker; the circuit breaker C3 is a bypass circuit breaker. 4. A low-voltage ride-through detection device for a grid-connected photovoltaic inverter according to claim 1, characterized in that: the node voltage between two reactors and the zero gear of the transformer voltage divider adjustment switch WL4 The node voltage at the bit end is connected to the photovoltaic inverter to realize the simulation of line short-circuit faults with different voltage amplitudes. 5. A low-voltage ride-through detection device for a grid-connected photovoltaic inverter according to claim 1, characterized in that: the transformer voltage divider adjustment switch WL2 and the transformer voltage divider adjustment switch WL3 are used to switch the input circuit The reactor tap; The more reactor taps connected to the transformer voltage divider adjustment switches WL2 and WL3 are, the more gears of the transformer voltage divider adjustment switches are required, the more drop points, and the more uniform the distribution within the voltage range.