Photovoltaic Inverter Test System

Abstract

The present application relates to a photovoltaic inverter test system, including: a first transformer, an AC / DC conversion device, a second transformer, a power grid simulation AC conversion device and a control device; the primary side of the first transformer is connected to the output side of the power grid simulation AC conversion device, and the secondary side of the first transformer is connected to the AC side of the AC / DC conversion device; the DC side of the AC / DC conversion device is connected to the DC side of the photovoltaic inverter under test; the primary side of the second transformer is connected to the AC side of the photovoltaic inverter under test, and the secondary side of the second transformer is connected to the input side of the power grid simulation AC conversion device; the control device is connected to the power grid simulation AC conversion device; the control device is used to obtain test parameters, and control the working state of the power grid simulation AC conversion device according to the test parameters to achieve the switching of the test conditions. The above-mentioned photovoltaic inverter test system can automatically switch the test conditions, which is conducive to improving the working efficiency of the photovoltaic inverter test process.

Description

Technical Field

[0001] The present application relates to the technical field of inverter testing, and in particular to a photovoltaic inverter testing system. Background Art

[0002] As energy issues become increasingly prominent, new energy technologies such as solar photovoltaic power generation technology have gained widespread attention worldwide. As the core component of the photovoltaic power generation system, the performance of the photovoltaic inverter is related to the power supply quality, operation reliability and power generation efficiency of the photovoltaic power generation system. In order to ensure the factory quality of the photovoltaic inverter, it is necessary to test the various performance indicators of the photovoltaic inverter.

[0003] In the traditional photovoltaic inverter testing process, the staff needs to connect the test equipment and conduct the test according to the steps specified in the corresponding test method. Since the photovoltaic inverter testing process involves a variety of test conditions, the staff needs to frequently perform wiring according to the test requirements of different test conditions, and the test operation is complicated. Therefore, the traditional photovoltaic inverter testing system has the disadvantage of low work efficiency. Summary of the invention

[0004] Based on this, it is necessary to provide a photovoltaic inverter testing system to address the above technical issues and improve the working efficiency of the photovoltaic inverter testing process.

[0005] A photovoltaic inverter test system comprises: a first transformer, an AC / DC conversion device, a second transformer, a power grid simulation AC conversion device and a control device; the primary side of the first transformer is connected to the output side of the power grid simulation AC conversion device, and the secondary side of the first transformer is connected to the AC side of the AC / DC conversion device; the DC side of the AC / DC conversion device is connected to the DC side of a photovoltaic inverter under test; the primary side of the second transformer is connected to the AC side of the photovoltaic inverter under test, and the secondary side of the second transformer is connected to the input side of the power grid simulation AC conversion device; the control device is connected to the power grid simulation AC conversion device;

[0006] The first transformer and the AC / DC converter are used to output DC power for testing to the photovoltaic inverter under test; the DC power for testing is inverted by the photovoltaic inverter under test to obtain feedback AC power;

[0007] The second transformer is used to transform the feedback AC power and then feed it back to the grid simulation AC conversion device; the grid simulation AC conversion device is used to perform AC conversion on the feedback AC power to simulate the grid power supply during the operation of the photovoltaic inverter under test;

[0008] The control device is used to obtain test parameters and control the working state of the power grid simulation AC conversion device according to the test parameters to achieve switching of test conditions.

[0009] In one of the embodiments, the AC-DC conversion device includes an AC-DC conversion unit and an energy storage unit;

[0010] The AC side of the AC / DC conversion unit is connected to the output side of the grid simulation AC conversion device through the first transformer; the DC side of the AC / DC conversion unit is connected to the DC side of the photovoltaic inverter under test; and the output side of the energy storage unit is connected to the DC side of the photovoltaic inverter under test.

[0011] In one embodiment, the photovoltaic inverter test system further includes a first switch device; the first switch device is connected to the grid simulation AC conversion device, the grid, the primary side of the first transformer, the secondary side of the second transformer and the control device; the AC / DC conversion unit and the energy storage unit are both connected to the control device;

[0012] The control device is also used to change the access state of the power grid simulation AC conversion device and the connection state of the photovoltaic inverter under test and the power grid by changing the working state of the first switch device.

[0013] In one of the embodiments, the first switch device includes a first switch unit, a second switch unit and a third switch unit;

[0014] The first switch unit connects the power grid and the primary side of the first transformer; the second switch unit connects the primary side of the first transformer and the secondary side of the second transformer; the third switch unit connects the power grid simulation AC conversion device; the third switch unit is also connected to the primary side of the first transformer and / or the secondary side of the second transformer;

[0015] The first switch unit, the second switch unit and the third switch unit are all connected to the control device.

[0016] In one of the embodiments, the first switch unit includes a first switch component, a second switch component and a first load component;

[0017] The two sides formed by the first switch component and the first load component being connected in series are respectively connected to the power grid and the primary side of the first transformer;

[0018] The second switch component is connected in parallel with the first load component;

[0019] The first switch assembly and the second switch assembly are both connected to the control device.

[0020] In one embodiment, the second switch unit includes a third switch component, a fourth switch component and a second load component;

[0021] Two sides formed by the third switch component and the second load component being connected in series are respectively connected to two sides of the fourth switch component;

[0022] The two sides of the fourth switch assembly are also connected to the primary side of the first transformer device and the secondary side of the second transformer device respectively;

[0023] The third switch assembly and the fourth switch assembly are both connected to the control device.

[0024] In one embodiment, the third switch unit connects the grid simulation AC conversion device, the primary side of the first transformer device and the secondary side of the second transformer device;

[0025] The third switch unit includes a fifth switch component, a sixth switch component, a seventh switch component and a third load component;

[0026] One side of the fifth switch assembly is connected to the primary side of the first transformer; the other side of the fifth switch assembly is connected to the output side of the grid simulation AC conversion device;

[0027] Two sides formed by the sixth switch component and the third load component being connected in series are respectively connected to two sides of the seventh switch component;

[0028] The two sides of the seventh switch assembly are also connected to the secondary side of the second transformer and the input side of the grid simulation AC conversion device respectively;

[0029] The fifth switch assembly, the sixth switch assembly and the seventh switch assembly are all connected to the control device.

[0030] In one embodiment, the photovoltaic inverter test system further includes a load device and a second switch device; the second switch device is connected to the secondary side of the second transformer device, the load device and the control device;

[0031] The control device is also used to change the access state of the load device by controlling the opening and closing of the second switch device according to the test parameters.

[0032] In one of the embodiments, the photovoltaic inverter test system further includes a sensor device; the sensor device is connected to the control device and is used to collect electrical parameters in the photovoltaic inverter test system and send them to the control device.

[0033] In one embodiment, the sensing device comprises a first sensing unit, a second sensing unit and a third sensing unit; the first sensing unit, the second sensing unit and the third sensing unit are all connected to the control device;

[0034] The first sensing unit is used to collect electrical parameters of the secondary side of the first transformer;

[0035] The second sensing unit is used to collect electrical parameters of the AC side of the photovoltaic inverter under test;

[0036] The third sensor unit is used to collect electrical parameters of the secondary side of the second transformer.

[0037] The above-mentioned photovoltaic inverter test system is configured with a first transformer and an AC / DC conversion device to convert the AC power output by the power grid simulation AC conversion device into DC power for testing, and output it to the photovoltaic inverter under test, and is configured with a control device to obtain test parameters, and control the working state of the power grid simulation AC conversion device according to the test parameters to simulate the power grid power supply during the working process of the photovoltaic inverter under test. The switching of test conditions can be automatically realized without the participation of staff, which is beneficial to improving the working efficiency of the photovoltaic inverter test process. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A block diagram of a photovoltaic inverter test system in one embodiment;

[0039] Figure 2 A block diagram of a photovoltaic inverter test system in another embodiment;

[0040] Figure 3 4 is a circuit schematic diagram of a photovoltaic inverter test system in one embodiment. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0043] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0044] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0045] In one embodiment, Figure 1 As shown, a photovoltaic inverter test system is provided, including: a first transformer 100, an AC / DC conversion device 200, a second transformer 300, a power grid simulation AC conversion device 400 and a control device 500. The primary side of the first transformer 100 is connected to the output side of the power grid simulation AC conversion device 400, and the secondary side of the first transformer 100 is connected to the AC side of the AC / DC conversion device 200; the DC side of the AC / DC conversion device 200 is connected to the DC side of the photovoltaic inverter under test; the primary side of the second transformer 300 is connected to the AC side of the photovoltaic inverter under test, and the secondary side of the second transformer 300 is connected to the input side of the power grid simulation AC conversion device 400; the control device 500 is connected to the power grid simulation AC conversion device 400.

[0046] Among them, the first transformer 100 and the second transformer 300 are devices that use the principle of electromagnetic induction to change the AC voltage, and when the first transformer 100 is a step-up transformer, the second transformer 300 is a step-down transformer, and when the first transformer 100 is a step-down transformer, the second transformer 300 is a step-up transformer. The specific types of the first transformer 100 and the second transformer 300 are not unique, for example, they can be transformers including dry-type transformers, or transformers including oil-immersed transformers. Further, the specific types of the first transformer 100 and the second transformer 300 do not have to be the same. The AC-DC conversion device 200 is a hardware device that includes a rectifier circuit and can convert AC input into DC output. The rectifier circuit can be a half-wave rectifier circuit, a full-wave rectifier circuit, or a bridge rectifier circuit. The power grid simulation AC conversion device 400 is a hardware device that includes an AC conversion circuit and can convert the voltage and frequency of AC power. The AC conversion circuit can be an AC voltage regulation circuit or a frequency conversion circuit. The control device 500 may be a hardware module including various processing chips and their peripheral circuits and having a logic operation function. The processing chip may be a single chip microcomputer, a DSP (Digital Signal Process) chip or an FPGA (Field Programmable Gate Array) chip.

[0047] Specifically, the first transformer 100 and the AC / DC conversion device 200 are used to output DC power for testing to the photovoltaic inverter under test, and the DC power for testing is inverted by the photovoltaic inverter under test to obtain feedback AC power. The second transformer 300 is used to transform the AC power and then feed it back to the power grid simulation AC conversion device 400. The power grid simulation AC conversion device 400 is used to perform AC conversion on the feedback AC power to simulate the power grid supply during the operation of the photovoltaic inverter under test. The control device 500 is used to obtain test parameters and control the working state of the power grid simulation AC conversion device 400 according to the test parameters to achieve the switching of the test working conditions.

[0048] Among them, the test parameters include the test type and the electrical parameters corresponding to the test type. For example, the test type can be a grid voltage and / or frequency characteristic test, a low voltage test, and a zero voltage test, and correspondingly, the test parameters can be a grid voltage amplitude, a grid voltage frequency, and a grid voltage duration, etc. Take the case where the test type is a grid voltage and frequency characteristic test as an example. During the test, the control device 500 can adjust the output voltage amplitude and frequency of the grid simulation AC conversion device 400 to test whether the photovoltaic inverter under test can trigger the protection function when the grid is overvoltage, undervoltage, or underfrequency.

[0049] Furthermore, the control device 500 may also be connected to the AC / DC conversion device 200 and the photovoltaic inverter under test, so as to control the working states of the AC / DC conversion device 200 and the photovoltaic inverter under test during the test.

[0050] The above-mentioned photovoltaic inverter test system, on the one hand, is configured with a power grid simulation AC conversion device 400 for simulating the power grid energy supply during the working process of the photovoltaic inverter under test, and is configured with a control device 500 to obtain test parameters, and controls the working state of the power grid simulation AC conversion device 400 according to the test parameters to simulate the power grid energy supply during the working process of the photovoltaic inverter under test. Without the participation of staff, the switching of test conditions can be automatically realized, which is beneficial to improving the working efficiency of the photovoltaic inverter test process; on the other hand, the second transformer 300 is configured to transform the feedback AC power output by the photovoltaic inverter under test, and then feed it back to the power grid simulation AC conversion device 400, which is equivalent to using energy mutual feedback during the test process, which is beneficial to reducing test power consumption, improving energy utilization, and reducing test costs.

[0051] In one embodiment, Figure 2 As shown, the AC / DC conversion device 200 includes an AC / DC conversion unit 210 and an energy storage unit 220. The AC side of the AC / DC conversion unit 210 is connected to the output side of the grid simulation AC conversion device 400 through the first transformer 100; the DC side of the AC / DC conversion unit 210 is connected to the DC side of the photovoltaic inverter under test; and the output side of the energy storage unit 220 is connected to the DC side of the photovoltaic inverter under test.

[0052] Among them, the AC / DC conversion unit 210 is a circuit unit including a rectifier circuit, which can convert AC input into DC output. For the specific definition of the rectifier circuit, please refer to the above and will not be repeated here. The energy storage unit 220 is a circuit unit including an energy storage element, which can realize electrical energy storage. The energy storage element can be an energy storage battery or an energy storage capacitor. In one embodiment, the energy storage unit 220 is a circuit unit including a photovoltaic cell, and the AC / DC conversion device 200 is a photovoltaic cell simulation AC / DC converter, which adopts high-performance PWM rectification technology to simulate the characteristics of photovoltaic cells and provide a "clean" power source for testing, and can provide the system with a full range of 420VDC-1000VDC test static voltage to ensure the accuracy of the test data.

[0053] Further, such as Figure 2As shown, the input side of the energy storage unit 220 can also be connected to the grid so as to obtain electric energy from the grid and charge the energy storage unit 220, thereby ensuring that the energy storage unit 220 has sufficient power during the test to meet the electric energy requirements of various test conditions; the output side of the grid simulation AC conversion device 400 can also be connected to the grid. During the test, the AC electric energy output by the tested photovoltaic inverter can be fed back to the grid through the grid simulation AC conversion device 400 to reduce losses and save test costs.

[0054] In the above embodiment, the energy storage unit 220 is configured in the AC / DC conversion device 200. During the test, no external power supply is required, and the energy storage unit 220 directly supplies power to the test system, which is conducive to improving the convenience of use of the test system.

[0055] In one embodiment, please continue to refer to Figure 2 The photovoltaic inverter test system further includes a first switch device 600. The first switch device 600 is connected to the grid simulation AC conversion device 400, the grid, the primary side of the first transformer 100, the secondary side of the second transformer 300, and the control device 500; the AC / DC conversion unit 210 and the energy storage unit 220 are both connected to the control device 500. The control device 500 is also used to change the access state of the grid simulation AC conversion device 400 and the connection state of the photovoltaic inverter under test and the grid by changing the working state of the first switch device 600.

[0056] The first switch device 600 may be a circuit device including various switch devices that can be controlled to close and open. The switch device may be a disconnector, a contactor, or a switch tube, etc., and the number of switch devices in the first switch device 600 may be multiple.

[0057] Specifically, when the photovoltaic inverter under test is electrically connected to the power grid, the photovoltaic inverter under test is in a grid-connected operation state, otherwise, the photovoltaic inverter under test is in an off-grid operation state. As described above, when the power grid simulation AC conversion device 400 is connected to the circuit, the control device 500 can perform grid voltage and / or frequency characteristic tests, low voltage tests, and zero voltage tests on the photovoltaic inverter under test by controlling the working state of the power grid simulation AC conversion device 400. When the power grid simulation AC conversion device 400 is not connected to the circuit, the energy storage unit 220 can provide the electrical energy required for the test to perform a static operating condition test on the photovoltaic inverter under test.

[0058] Take the case where the energy storage unit 220 is a circuit unit including a photovoltaic cell, the AC / DC conversion device 200 is a photovoltaic cell simulating AC / DC converter, and the photovoltaic inverter under test is electrically connected to the power grid as an example. Specifically, the control device 500 is connected to the photovoltaic cell simulating AC / DC converter, and the test voltage can be changed by changing the output of the photovoltaic cell simulating AC / DC converter to perform a full-range static working condition test on the photovoltaic inverter under test. Furthermore, after the test voltage passes through the photovoltaic inverter under test, it is fed back to the power grid through the second transformer 300 and the first switch device 600. In addition, during the full-range static working condition test, the grid-connected current of the photovoltaic inverter under test can be changed, and when the current exceeds the overcurrent protection value, whether the photovoltaic inverter under test can trigger the protection function to evaluate whether the overcurrent protection of the photovoltaic inverter under test meets the standard. Based on the same principle, the overtemperature setting value can also be adjusted to test whether the overtemperature protection function of the photovoltaic inverter under test meets the standard.

[0059] In the above embodiment, the first switch device 600 is configured to change the access state of the power grid simulation AC conversion device 400. When the power grid simulation AC conversion device 400 is not connected to the circuit, the AC / DC conversion device 200 provides a test voltage, and a static operating condition test can be performed on the photovoltaic inverter under test, which is conducive to expanding the application scenarios of the photovoltaic inverter test system.

[0060] In one embodiment, Figure 3 As shown, the first switch device 600 includes a first switch unit 610, a second switch unit 620 and a third switch unit 630. The first switch unit 610 connects the power grid and the primary side of the first transformer 100; the second switch unit 620 connects the primary side of the first transformer 100 and the secondary side of the second transformer 300; the third switch unit 630 connects the power grid simulation AC conversion device 400; the third switch unit 630 is also connected to the primary side of the first transformer 100 and / or the secondary side of the second transformer 300. The first switch unit 610, the second switch unit 620 and the third switch unit 630 are all connected to the control device 500.

[0061] The specific definition of the first switch unit 610, the second switch unit 620 and the third switch unit 630 can be found in the above definition of the first switch device 600, which will not be repeated here. The third switch unit 630 is also connected to the primary side of the first transformer 100 and / or the secondary side of the second transformer 300, which means that the branch formed by the third switch unit 630 and the power grid simulation AC conversion device 400 is connected in parallel with the branch where the second switch unit 620 is located. Figure 3 In the embodiment, the third switch unit 630 connects the input side and the output side of the grid simulation AC conversion device 400 , and the primary side of the first transformer 100 and the secondary side of the second transformer 300 .

[0062] Specifically, the control device 500 changes the connection state between the tested photovoltaic inverter and the power grid by changing the working state of the first switch unit 610; and changes the access state of the power grid simulation AC conversion device 400 by changing the working state of the second switch unit 620 and the third switch unit 630. Further, the control device 500 can also change the connection state between the AC / DC conversion device 200 and the power grid by changing the working state of the first switch unit 610.

[0063] In one embodiment, please continue to refer to Figure 3 The first switch unit 610 includes a first switch component QF1, a second switch component KM1 and a first load component 611. The two sides formed by the first switch component QF1 and the first load component 611 are connected in series, and are respectively connected to the power grid and the primary side of the first transformer 100; the second switch component KM1 is connected in parallel with the first load component 611; the first switch component QF1 and the second switch component KM1 are both connected to the control device 500.

[0064] Among them, the first switch component QF1 and the second switch component KM1 are circuit components including switch devices. The first load component 611 is a circuit component including a load resistor. The two sides formed by the first switch component QF1 and the first load component 611 being connected in series are respectively connected to the power grid and the primary side of the first transformer 100, which means: the first switch component QF1 is connected in series with the first load component 611, the other side of the first switch component QF1 is connected to the power grid, and the other side of the first load component 611 is connected to the primary side of the first transformer 100, or the other side of the first switch component QF1 is connected to the primary side of the first transformer 100, and the other side of the first load component 611 is connected to the power grid.

[0065] Specifically, when the first switch component QF1 is closed, the power grid is connected to the photovoltaic inverter test system. At this time, if the second switch component KM1 is disconnected, the first load component 611 is connected to the system; if the second switch component KM1 is closed, the first load component 611 is not connected to the system. The control device 500 can realize the slow start of the tested photovoltaic inverter by controlling the second switch component KM1: first, at the moment of the photovoltaic inverter being started and connected to the grid, the second switch component KM1 is controlled to be disconnected, and the first load component 611 is connected to the system. After the grid connection is completed, the second switch component KM1 is controlled to be closed, and the first load component 611 is not connected to the system.

[0066] It should be noted that when the power grid is a three-phase power grid, the switch component and the load component in this application refer to the switch device arranged in a certain phase in the switch component and the load resistor arranged in the corresponding phase in the load component being connected in series. Similarly, the switch component and the load component are connected in parallel, which means that the switch device arranged in a certain phase in the switch component and the load resistor arranged in the corresponding phase in the load component are connected in parallel.

[0067] Specifically, Figure 3 As shown, the power grid is a three-phase power grid. The first switch component QF1 includes three switch devices, and the second switch component KM1 also includes three switch devices. The switch devices in the first switch component QF1 and the second switch component KM1 are grouped in pairs and are respectively connected to the three phases A, B and C. The first load component 611 includes three groups of load resistors, which are respectively connected to the three phases A, B and C. The first switch component QF1 is connected in series with the first load component 611, which means that the switch device set in a certain phase in the first switch component QF1 is connected in series with the load resistor set in the corresponding phase in the first load component 611. Similarly, the second switch component KM1 is connected in parallel with the first load component 611, which means that the switch device set in a certain phase in the second switch component KM1 is connected in parallel with the load resistor set in the corresponding phase in the first load component 611. In addition, in each group of load resistors, the number of resistors is not unique, for example, it can be one or more, and when there are multiple load resistors, the connection relationship between the load resistors can be series, parallel or mixed. As shown in FIG. Figure 3 The number of resistors included in the three groups of load resistors are all one, namely resistor R1, resistor R2 and resistor R3.

[0068] In one embodiment, please continue to refer to Figure 3 The second switch unit 620 includes a third switch component KM3, a fourth switch component KM2 and a second load component 621. The two sides formed by the third switch component KM3 and the second load component 621 being connected in series are respectively connected to the two sides of the fourth switch component KM2; the two sides of the fourth switch component KM2 are also respectively connected to the primary side of the first transformer 100 and the secondary side of the second transformer 300; the third switch component KM3 and the fourth switch component KM2 are both connected to the control device 500.

[0069] Among them, the specific limitations on the third switch component KM3 and the fourth switch component KM2 refer to the above limitations on the first switch component QF1 and the second switch component KM1, and the specific limitations on the second load component 621 refer to the above limitations on the first load component 611, which will not be repeated here.

[0070] Specifically, when performing a static working condition test, the control device 500 can realize a slow start of the photovoltaic inverter under test by controlling the third switch component KM3 and the fourth switch component KM2: first, at the moment of starting the photovoltaic inverter under test, the fourth switch component KM2 is controlled to be disconnected, the third switch component KM3 is closed, and the second load component 621 is connected to the system. After the photovoltaic inverter under test is started, the fourth switch component KM2 is controlled to be closed, and the second load component 621 is not connected to the system. It should be noted that when performing a static working condition test, under the condition of current, considering the arcing phenomenon, the third switch component KM3 and the fourth switch component KM2 are both kept closed, and the branch where the third switch component KM3 is located is bypassed by the branch where the fourth switch component KM2 is located.

[0071] When the power grid is a three-phase power grid, the connection relationship between the third switch component KM3, the fourth switch component KM2 and the components in the second load component 621 is as described above and will not be repeated here. Similarly, in each group of load resistors in the second load component 621, the number of resistors is not unique, for example, it can be one or more, and when there are multiple load resistors, the connection relationship between the load resistors can be series, parallel or mixed. Figure 3 The number of resistors included in the three groups of load resistors are all one, namely resistor R4, resistor R5 and resistor R6.

[0072] In one embodiment, the third switch unit 630 connects the grid simulation AC conversion device 400, the primary side of the first transformer 100, and the secondary side of the second transformer 300. In this embodiment, please continue to refer to Figure 3 The third switch unit 630 includes a fifth switch component QF2, a sixth switch component KM5, a seventh switch component KM4 and a third load component 631; one side of the fifth switch component QF2 is connected to the primary side of the first transformer 100; the other side of the fifth switch component QF2 is connected to the output side of the power grid simulation AC conversion device 400; the two sides formed by the sixth switch component KM5 and the third load component 631 being connected in series are respectively connected to the two sides of the seventh switch component KM4; the two sides of the seventh switch component KM4 are also respectively connected to the secondary side of the second transformer 300 and the input side of the power grid simulation AC conversion device 400; the fifth switch component QF2, the sixth switch component KM5 and the seventh switch component KM4 are all connected to the control device 500.

[0073] Among them, the specific limitations on the fifth switch component QF2, the sixth switch component KM5 and the seventh switch component KM4 refer to the above limitations on the first switch component QF1 and the second switch component KM1, and the specific limitations on the third load component 631 refer to the above limitations on the first load component 611, which will not be repeated here.

[0074] Specifically, when conducting grid voltage and / or frequency characteristic test, low voltage test and zero voltage test, the control device controls the fifth switch component QF2 to close, and can realize the slow start of the photovoltaic inverter under test by controlling the sixth switch component KM5 and the seventh switch component KM4: first, at the moment of starting the photovoltaic inverter under test, the seventh switch component KM4 is controlled to be disconnected, the sixth switch component KM5 is closed, and the third load component 631 is connected to the system, and after the photovoltaic inverter under test is started, the seventh switch component KM4 is controlled to be closed, and the third load component 631 is not connected to the system. Similarly, under the condition of current, considering the arcing phenomenon, the sixth switch component KM5 and the seventh switch component KM4 are both kept closed, and the branch where the sixth switch component KM5 is located is bypassed by the branch where the seventh switch component KM4 is located.

[0075] When the power grid is a three-phase power grid, the connection relationship between the fifth switch component QF2, the sixth switch component KM5, the seventh switch component KM4 and the components in the third load component 631 is as described above and will not be repeated here. Similarly, in each group of load resistors in the third load component 631, the number of resistors is not unique, for example, it can be one or more, and when there are multiple load resistors, the connection relationship between the load resistors can be series, parallel or mixed. Figure 3 The number of resistors included in the three groups of load resistors are all one, namely resistor R7, resistor R8 and resistor R9.

[0076] The above is the specific structure of the first switch device 600, which has a simple structure and is conducive to reducing circuit costs.

[0077] In one embodiment, Figure 3 As shown, the photovoltaic inverter test system also includes a second switch device 700 and a load device 800; the second switch device 700 is connected to the secondary side of the second transformer device 300, the load device 800 and the control device 500. The control device 500 is also used to change the access state of the load device 800 by controlling the opening and closing of the second switch device 700 according to the test parameters.

[0078] The specific definition of the second switch device 700 refers to the definition of the first switch device 600 mentioned above, which will not be repeated here. The specific type of the load device 800 is not unique, for example, it can be an inductive load, a capacitive load or a resistive load. In one embodiment, Figure 3 As shown, the load device 800 is an RLC load.

[0079] Specifically, the control device 500 can control the second switch device 700 to close at a specified test time according to the test parameters, connect the load device 800, simulate the island test condition, and test whether the tested photovoltaic inverter can activate the island protection function. Figure 3As shown, when the power grid is a three-phase power grid, the second switch device 700 includes at least three switch devices, which are respectively arranged in corresponding phases.

[0080] In the above embodiment, a second switch device 700 and a load device 800 are configured, and the control device 500 can change the access state of the load device 800 by controlling the opening and closing of the second switch device 700 to simulate an island test condition, which is conducive to expanding the application scenarios of the photovoltaic inverter test system.

[0081] In one embodiment, the photovoltaic inverter test system further includes a sensor device; the sensor device is connected to the control device 500 and is used to collect electrical parameters in the photovoltaic inverter test system and send the electrical parameters to the control device 500 .

[0082] The electrical parameter may be current and / or voltage, and correspondingly, the sensing device may be a hardware device including various current sensors and / or voltage sensors. Specifically, the sensing device may be arranged in the branch where the photovoltaic inverter under test is located, for example Figure 2 At any position on the branch formed by the first transformer 100 , the AC / DC converter 200 , the photovoltaic inverter under test and the second transformer 300 , the electrical parameters during the test are collected and sent to the control device 500 .

[0083] In one embodiment, Figure 3 As shown, the sensing device includes a first sensing unit 910, a second sensing unit 920 and a third sensing unit 930; the first sensing unit 910, the second sensing unit 920 and the third sensing unit 930 are all connected to the control device 500; the first sensing unit 910 is used to collect electrical parameters of the secondary side of the first transformer 100; the second sensing unit 920 is used to collect electrical parameters of the AC side of the photovoltaic inverter under test; the third sensing unit 930 is used to collect electrical parameters of the secondary side of the second transformer 300.

[0084] In the above embodiment, the sensor device is arranged to collect the electrical parameters during the test and send them to the control device 500, so that the control device 500 can evaluate the performance of the photovoltaic inverter under test according to the electrical parameters.

[0085] Furthermore, a display device and a communication device connected to the control device 500 may be provided to display and output corresponding electrical parameters, test results, as well as fault, operation and power supply status, so that the staff can understand the test status in a timely manner.

[0086] For ease of understanding, the following Figure 3 , the photovoltaic inverter test system involved in this application is described in detail.

[0087] In one embodiment, Figure 3As shown, the photovoltaic inverter test system includes a first transformer 100 (transformer T1), an AC / DC conversion device 200, a second transformer 300 (transformer T2), a power grid simulation AC conversion device 400, a control device 500, a load device 800 and a sensor device. A first switch unit 610 is connected between the primary side of the transformer T1 and the power grid; a second switch unit 620 is connected between the primary side of the transformer T1 and the secondary side of the transformer T2; the power grid simulation AC conversion device 400 is connected to the system through a third switch unit 630; and the load device 800 is connected to the system through a second switch device KM6.

[0088] Among them, the AC / DC conversion device 200 is a photovoltaic cell simulation AC / DC converter, which adopts high-performance PWM rectification technology to simulate the characteristics of photovoltaic cells and provide a "clean" power source for testing, and can provide the system with a full range of 420VDC-1000VDC test static voltage. The power grid simulation AC conversion device 400 converts the electric energy output by the photovoltaic cell simulation AC / DC converter to simulate the power supply of the power grid during the operation of the photovoltaic inverter under test. The load device 800 is an RLC load, which can simulate island protection tests of different load levels.

[0089] The first switch unit 610 includes a first switch component QF1, a second switch component KM1 and a first load component 611. The two sides formed by the first switch component QF1 and the first load component 611 are connected in series, and are respectively connected to the power grid and the primary side of the transformer T1; the second switch component KM1 is connected in parallel with the first load component 611; the first switch component QF1 and the second switch component KM1 are both connected to the control device 500.

[0090] The second switch unit 620 includes a third switch component KM3, a fourth switch component KM2, and a second load component 621. The two sides formed by the third switch component KM3 and the second load component 621 being connected in series are respectively connected to the two sides of the fourth switch component KM2; the two sides of the fourth switch component KM2 are also respectively connected to the primary side of the transformer T1 and the secondary side of the transformer T2; the third switch component KM3 and the fourth switch component KM2 are both connected to the control device 500.

[0091] The third switch unit 630 includes a fifth switch component QF2, a sixth switch component KM5, a seventh switch component KM4 and a third load component 631; one side of the fifth switch component QF2 is connected to the primary side of the transformer T1; the other side of the fifth switch component QF2 is connected to the output side of the power grid simulation AC conversion device 400; the two sides formed by the sixth switch component KM5 and the third load component 631 being connected in series are respectively connected to the two sides of the seventh switch component KM4; the two sides of the seventh switch component KM4 are also respectively connected to the secondary side of the transformer T2 and the input side of the power grid simulation AC conversion device 400; the fifth switch component QF2, the sixth switch component KM5 and the seventh switch component KM4 are all connected to the control device 500.

[0092] The sensing device includes a first sensing unit 910, a second sensing unit 920 and a third sensing unit 930; the first sensing unit 910, the second sensing unit 920 and the third sensing unit 930 are all connected to the control device 500; the first sensing unit 910 is used to collect electrical parameters of the secondary side of the transformer T1; the second sensing unit 920 is used to collect electrical parameters of the AC side of the photovoltaic inverter under test; the third sensing unit 930 is used to collect electrical parameters of the secondary side of the transformer T2.

[0093] Specifically, the DC side of the photovoltaic cell simulation AC / DC converter is connected to the DC side of the photovoltaic inverter under test to provide DC power for the photovoltaic inverter under test. The control device 500 obtains the test parameters, and according to the test parameters, by controlling the opening and closing of each switch unit and the switch device, as well as the working state of the photovoltaic cell simulation AC / DC converter and the power grid simulation AC conversion device 400, the photovoltaic inverter under test can be subjected to a full range of static working condition tests, power grid voltage / frequency characteristic tests, low voltage and zero voltage tests, overcurrent and overtemperature protection performance tests, and island tests, etc., which is conducive to improving the test efficiency.

[0094] Further, when conducting a full range static working condition test, the control sequence of the control device 500 is as follows: control QF1 to close, QF2 to disconnect, KM2 to disconnect, and KM3 to disconnect; start the photovoltaic cell to simulate the output voltage of the AC / DC converter, and after the photovoltaic cell simulates the AC / DC converter to start, control KM1 to close and start the photovoltaic inverter under test. At this time, the photovoltaic inverter under test is in an off-grid operation state; control KM3 to close and KM2 to disconnect, and the photovoltaic inverter under test is connected to the grid and starts slowly. After the start is completed, control KM2 to close and KM3 to be in a closed state; at this time, the photovoltaic inverter under test is in a grid-connected operation state; control the photovoltaic cell to simulate the AC / DC converter output test voltage required, and perform a static working condition test on the inverter in grid operation. During the above test mode switching and testing process, KM6, KM4, KM5 and QF2 are all in a disconnected state, and the feedback AC power output by the photovoltaic inverter under test is transformed by transformer T2 and fed into the grid through the branch where KM2 is located, which is conducive to reducing the test cost. In addition, during the full-range static condition test, the grid-connected current of the tested photovoltaic inverter can be changed, and the protection function of the tested photovoltaic inverter can be triggered when the current exceeds the overcurrent protection value to evaluate whether the overcurrent protection of the tested photovoltaic inverter meets the standard. Based on the same principle, the overtemperature set value can also be adjusted to test whether the overtemperature protection function of the tested photovoltaic inverter meets the standard.

[0095] When conducting grid voltage / frequency characteristics, low voltage and zero voltage tests, the control sequence of the control device 500 is as follows: control KM2 and KM3 to be disconnected, QF1 and QF2 to be closed; start the photovoltaic cell to simulate the output voltage of the AC / DC converter; control QF2 to be closed, start the grid simulation AC conversion device 400, and output the required grid voltage for the test through voltage transformation simulation; after the grid simulation AC conversion device 40 is started, control KM1 to be closed, and start the photovoltaic inverter under test. At this time, the photovoltaic inverter under test is in an off-grid operation state; control K M5 is closed, KM4 and KM1 are disconnected, and the photovoltaic inverter under test is connected to the grid and starts slowly. After the startup is completed, KM1 and KM4 are controlled to be closed, and KM5 is disconnected. At this time, the photovoltaic inverter under test is in a grid-connected operation state; the working parameters of the power grid simulation AC conversion device 400 are controlled to change the power grid voltage and frequency characteristics, and the power grid voltage / frequency characteristics of the photovoltaic inverter under test are tested, or the power grid voltage amplitude and duration are changed by controlling the power grid simulation AC conversion device 400 to perform low voltage and zero voltage tests on the photovoltaic inverter under test. During the test, the control device 500 can also adjust the output voltage amplitude and frequency of the power grid simulation AC conversion device 400 to test whether the photovoltaic inverter under test can trigger the protection function when the power grid is over-voltage, under-voltage or under-frequency. In addition, during the test, energy can be fed back to the power grid through the power grid simulation AC conversion device 400.

[0096] When performing an islanding test, the control sequence of the control device 500 is as follows: control QF1 to close, QF2 to disconnect, KM2 to disconnect, and KM3 to disconnect; start the photovoltaic cell to simulate the output voltage of the AC / DC converter, close KM1, and start the photovoltaic inverter under test. At this time, the photovoltaic inverter under test is in an off-grid operation state; control KM3 to close, KM2 to disconnect, and the photovoltaic inverter under test is connected to the grid for slow start. After the startup is completed, control KM2 to close. At this time, the photovoltaic inverter under test is in a grid-connected operation state; control KM6 to close at a specified time, and put RLC load into operation to simulate an islanding condition to test whether the inverter can complete the anti-islanding protection function.

[0097] In addition, the photovoltaic inverter test system is also provided with a display device and a communication device connected to the control device 500 to display and output corresponding electrical parameters, test results, as well as faults, operation and power supply status, so that the staff can understand the test situation in time.

[0098] The above-mentioned photovoltaic inverter test system can automatically switch the test conditions without the participation of staff, which is beneficial to improving the work efficiency of the photovoltaic inverter test process; the feedback AC power output by the tested photovoltaic inverter is transformed and fed back to the power grid, which is equivalent to using energy mutual feedback during the test process, which is beneficial to reducing test power consumption, improving energy utilization, and reducing test costs; the photovoltaic cell simulation AC / DC converter is configured to adopt high-performance PWM rectification technology to simulate the characteristics of photovoltaic cells and provide a "clean" power source to ensure the accuracy of test data; the sensor device is configured to measure multiple electrical parameters and provide display and output, which is beneficial to improving the ease of use of the test system.

[0099] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A photovoltaic inverter test system, characterized in that: include: A first transformer, an AC / DC converter, a second transformer, a power grid simulation AC converter and a control device; the primary side of the first transformer is connected to the output side of the power grid simulation AC converter, and the secondary side of the first transformer is connected to the AC side of the AC / DC converter; the DC side of the AC / DC converter is connected to the DC side of the photovoltaic inverter under test; the primary side of the second transformer is connected to the AC side of the photovoltaic inverter under test, and the secondary side of the second transformer is connected to the input side of the power grid simulation AC converter; the control device is connected to the power grid simulation AC converter; The first transformer and the AC / DC converter are used to output DC power for testing to the photovoltaic inverter under test; the DC power for testing is inverted by the photovoltaic inverter under test to obtain feedback AC power; The second transformer is used to transform the feedback AC power and then feed it back to the grid simulation AC conversion device; the grid simulation AC conversion device is used to perform AC conversion on the feedback AC power to simulate the grid power supply during the operation of the photovoltaic inverter under test; The control device is used to obtain test parameters and control the working state of the power grid simulation AC conversion device according to the test parameters to achieve the switching of the test working conditions; The photovoltaic inverter test system further includes a first switch device; the first switch device is connected to the power grid simulation AC conversion device, the power grid, the primary side of the first transformer device, the secondary side of the second transformer device and the control device; The control device is also used to change the access state of the power grid simulation AC conversion device and the connection state of the photovoltaic inverter under test and the power grid by changing the working state of the first switch device; The first switch device includes a first switch unit, a second switch unit and a third switch unit; The first switch unit connects the power grid and the primary side of the first transformer; the second switch unit connects the primary side of the first transformer and the secondary side of the second transformer; the third switch unit connects the power grid simulation AC conversion device; the third switch unit is also connected to the primary side of the first transformer and / or the secondary side of the second transformer; The first switch unit, the second switch unit and the third switch unit are all connected to the control device.

2. The photovoltaic inverter test system according to claim 1, characterized in that: The AC / DC conversion device includes an AC / DC conversion unit and an energy storage unit; The AC side of the AC / DC conversion unit is connected to the output side of the grid simulation AC conversion device through the first transformer; the DC side of the AC / DC conversion unit is connected to the DC side of the photovoltaic inverter under test; the output side of the energy storage unit is connected to the DC side of the photovoltaic inverter under test; The AC / DC conversion unit and the energy storage unit are both connected to the control device.

3. The photovoltaic inverter test system according to claim 1, characterized in that: The test parameters include a test type and an electrical parameter corresponding to the test type.

4. The photovoltaic inverter test system according to claim 1, characterized in that: The system further comprises a display device and a communication device connected to the control device.

5. The photovoltaic inverter test system according to claim 1, characterized in that: The first switch unit includes a first switch component, a second switch component and a first load component; The two sides formed by the first switch component and the first load component being connected in series are respectively connected to the power grid and the primary side of the first transformer; The second switch component is connected in parallel with the first load component; The first switch assembly and the second switch assembly are both connected to the control device.

6. The photovoltaic inverter test system according to claim 1, characterized in that: The second switch unit includes a third switch component, a fourth switch component and a second load component; Two sides formed by the third switch component and the second load component being connected in series are respectively connected to two sides of the fourth switch component; The two sides of the fourth switch assembly are also connected to the primary side of the first transformer device and the secondary side of the second transformer device respectively; The third switch assembly and the fourth switch assembly are both connected to the control device.

7. The photovoltaic inverter test system according to claim 1, characterized in that: The third switch unit is connected to the grid simulation AC conversion device, the primary side of the first transformer device and the secondary side of the second transformer device; The third switch unit includes a fifth switch component, a sixth switch component, a seventh switch component and a third load component; One side of the fifth switch assembly is connected to the primary side of the first transformer; the other side of the fifth switch assembly is connected to the output side of the grid simulation AC conversion device; Two sides formed by the sixth switch component and the third load component being connected in series are respectively connected to two sides of the seventh switch component; The two sides of the seventh switch assembly are also connected to the secondary side of the second transformer and the input side of the grid simulation AC conversion device respectively; The fifth switch assembly, the sixth switch assembly and the seventh switch assembly are all connected to the control device.

8. The photovoltaic inverter testing system according to any one of claims 1 to 7, characterized in that: It also includes a load device and a second switch device; the second switch device is connected to the secondary side of the second transformer device, the load device and the control device; The control device is also used to change the access state of the load device by controlling the opening and closing of the second switch device according to the test parameters.

9. The photovoltaic inverter testing system according to any one of claims 1 to 7, characterized in that: It also includes a sensor device; the sensor device is connected to the control device and is used to collect electrical parameters in the photovoltaic inverter test system and send them to the control device.

10. The photovoltaic inverter test system according to claim 9, characterized in that: The sensing device comprises a first sensing unit, a second sensing unit and a third sensing unit; the first sensing unit, the second sensing unit and the third sensing unit are all connected to the control device; The first sensing unit is used to collect electrical parameters of the secondary side of the first transformer; The second sensing unit is used to collect electrical parameters of the AC side of the photovoltaic inverter under test; The third sensor unit is used to collect electrical parameters of the secondary side of the second transformer.

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