A test system and method for photovoltaic inverter grid harmonic adaptability

Abstract

The application provides a kind of test system and method for photovoltaic inverter grid harmonic adaptability, including terminal, rectifier power supply, DC bus, battery pack, DC voltmeter, AC bus, programmable AC source, multifunction meter, adjustable load, digital oscilloscope and harmonic generation module, the application can simulate the working condition of photovoltaic inverter during use, simulate the power generation working condition of photovoltaic panel by battery pack, since the inverter cannot be directly connected with the grid during testing, use programmable AC source as the AC source of simulated grid change, and through adjustable load as capacitive and inductive load that consumes reactive power and active power of AC bus, using harmonic generation module can also inject corresponding harmonic into the grid, so the actual working condition of inverter can be simulated to the greatest extent, the adaptability of photovoltaic inverter can be tested under various harmonic conditions, the test effect is better, and the accuracy is high.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic inverter grid connection testing technology, specifically to a testing system and method for the grid harmonic adaptability of photovoltaic inverters. Background Technology

[0002] In recent years, with the gradual depletion of fossil fuels such as oil and coal and the increasing severity of environmental pollution, the photovoltaic grid-connected power generation industry has developed rapidly. The photovoltaic grid-connected inverter is a key piece of equipment in a photovoltaic power generation system. An inverter is a conversion device that transforms direct current (DC) into alternating current (AC) to supply power to loads. Since photovoltaic systems generate DC power, an inverter must be configured to supply AC loads. An inverter is a conversion device that uses power semiconductor switches to control the conversion of DC power into AC power. Therefore, its functionality and reliability verification are crucial for the stable operation of the photovoltaic power generation system and the quality of the power grid. In the power grid connected to the inverter, many industrial and residential electrical devices with characteristics such as low power factor, nonlinearity, asymmetry, and impulsiveness are connected, resulting in a high amount of harmonics in the power grid. The presence of these harmonics can affect the operation of the inverter and even damage it. Therefore, before a photovoltaic inverter is connected to the grid, its grid harmonic adaptability needs to be tested to prevent damage caused by harmonics.

[0003] The publication number CN105182068A provides a test system and method for the grid harmonic adaptability of photovoltaic inverters. The test system and method acquire the voltage and current at both ends of the photovoltaic inverter through a data acquisition module, and finally measure the grid harmonic adaptability of the photovoltaic inverter. However, the device cannot completely simulate the grid-connected use of the photovoltaic inverter, especially it cannot completely simulate the harmonic situation inside the actual power grid, resulting in inaccurate test results. Summary of the Invention

[0004] The purpose of this invention is to provide a testing system and method for the grid harmonic adaptability of photovoltaic inverters, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A test system for the grid harmonic adaptability of photovoltaic inverters includes terminal blocks, a rectifier power supply, a DC bus, a battery bank, a DC voltmeter, an AC bus, a programmable AC source, a multifunction meter, an adjustable load, a digital oscilloscope, and a harmonic generation module, wherein:

[0007] The wiring terminals include an AC power terminal XT1, a DC input terminal XT2, and an AC output terminal XT3. The AC input terminal of the rectifier power supply is electrically connected to the wiring terminals, and the DC output terminal is electrically connected to the DC bus. The battery pack is composed of multiple batteries connected in series, and its output terminal is electrically connected to the DC bus. A DC voltmeter is electrically connected to the DC bus. The DC input terminal XT2 is electrically connected to the DC bus.

[0008] The AC bus is electrically connected to an AC output terminal XT3. The output terminal of the programmable AC source is connected in parallel with the AC bus and is used as an AC source to simulate grid voltage fluctuations, flicker, and frequency fluctuations. The multifunction meter is electrically connected to the AC bus and is used to measure and display the voltage, current, and reactive power of the AC bus. The adjustable load is connected in parallel with the AC bus and is used as a capacitive and inductive load that consumes the reactive and active power of the AC bus. The sampling terminal of the digital oscilloscope is electrically connected to the AC bus and is used to display the voltage and current waveforms of the AC bus. The harmonic generation module is electrically connected to the AC bus and is used to generate harmonics and inject them into the AC bus.

[0009] Preferably, a circuit breaker Q1 is connected in series in the circuit between the AC mains terminal XT1 and the AC input terminal of the rectifier power supply; a circuit breaker Q2 is connected in series in the circuit electrically connected to the output terminal of the battery pack and the DC bus; a circuit breaker Q3 is connected in series in the circuit electrically connected to the DC input terminal XT2 and the DC bus; a circuit breaker Q4 is connected in series in the circuit electrically connected to the AC bus and the AC output terminal XT3; and a circuit breaker Q5 is connected in series in the circuit parallel to the output terminal of the programmable AC source and the AC bus.

[0010] Preferably, a fuse FU1 is connected in series in the circuit that electrically connects the DC output terminal of the rectifier power supply to the DC bus, and a fuse FU2 is also connected in series in the circuit that electrically connects the DC input terminal XT2 to the DC bus.

[0011] Preferably, a current transformer is fitted onto the AC bus, and the current sampling terminal of the multifunction meter is electrically connected to the current transformer.

[0012] Preferably, the adjustable load includes three types of loads: an adjustable capacitor C3 and a load resistor R2 connected in series; an adjustable inductor L2 and a load resistor R2 connected in series; and an adjustable inductor L3, an adjustable capacitor C4, and a load resistor R2 connected in series. All three types of loads are connected in parallel to the AC bus. The load consisting of the adjustable capacitor C3 and the load resistor R2 connected in series is electrically connected to the AC bus through a circuit breaker Q7. The load consisting of the adjustable inductor L2 and the load resistor R2 connected in series is electrically connected to the AC bus through a circuit breaker Q8. The load consisting of the adjustable inductor L3, the adjustable capacitor C4, and the load resistor R2 connected in series is electrically connected to the AC bus through a circuit breaker Q9.

[0013] Preferably, the harmonic generation module includes a controller, a drive circuit, an H-bridge composed of transistors S1, S2, S3, S4 and diodes D1, D2, D3, D4, and a DC energy storage capacitor C1. The input terminal of the H-bridge is electrically connected to the DC bus, and the output terminal is electrically connected to the AC bus. The controller sends a control signal to the drive circuit. The drive circuit is electrically connected to the bases of transistors S1, S2, S3, S4 to control the switching of transistors S1, S2, S3, S4. The DC energy storage capacitor C1 is connected in parallel to the input terminal of the H-bridge. The input terminal of the H-bridge is electrically connected to the DC bus through a circuit breaker Q6.

[0014] Preferably, a resonant circuit is connected in parallel to the output terminal of the H-bridge. The resonant circuit includes a resonant inductor L1, a changeover switch QS, a resonant resistor R1, and a capacitor bank. The inductor L1, the changeover switch QS, the resonant resistor R1, and the capacitor bank are connected in series at the output terminal of the H-bridge. The capacitor bank consists of several resonant capacitors C2 connected in parallel. Each resonant capacitor C2 is connected in series with a moving contact of the changeover switch QS.

[0015] The present invention also provides a test method for the grid harmonic adaptability of photovoltaic inverters, wherein the test method is applicable to the above-mentioned test system, and the specific steps include:

[0016] S1: Electrically connect the DC input terminal and DC input terminal XT2 of the inverter to be tested, and electrically connect the AC output terminal and AC output terminal XT3.

[0017] S2: Turn on the programmable AC source to supply power to the AC bus and control the programmable AC source to simulate various possible grid changes such as grid voltage fluctuations, flicker, and frequency fluctuations.

[0018] S3: Deploy the appropriate number of battery packs as needed to power the DC bus, mimicking the power generation of a photovoltaic array.

[0019] S4: Enable the inverter under test to operate. The inverter converts the DC power generated by the battery pack into AC power and connects the converted AC power to the AC bus to the grid.

[0020] S5: Adjust the capacitive and inductive reactance of the adjustable load to simulate the usage of various loads in the power grid, generate power grid harmonics through the harmonic generation module, and inject the harmonics into the AC bus.

[0021] S6: Use a digital oscilloscope and multimeter to observe the grid conditions after the inverter is connected to the grid, thereby determining the grid harmonic adaptability of the inverter under test;

[0022] S7: After the test is completed, remove the inverter to be tested, connect the AC terminal XT1 to the AC power source, and the rectifier power supply will convert the AC power into DC power and inject it into the DC bus to charge the battery pack connected to the DC bus.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] This invention can completely simulate the working conditions of a photovoltaic inverter during use. It uses a battery pack to simulate the power generation of the photovoltaic panels. Since the inverter cannot be directly connected to the grid during testing, a programmable AC source is used as the AC source to simulate grid changes. An adjustable load is used as a capacitive and inductive load to consume the reactive and active power of the AC bus. A harmonic generation module can also inject corresponding harmonics into the grid. Therefore, it can simulate the actual working conditions of the inverter to the greatest extent and test the adaptability of the photovoltaic inverter under various harmonic conditions. The test results are good and the accuracy is high. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall system structure of the present invention;

[0026] Figure 2 This is a schematic diagram of the system structure of the harmonic generation module in this invention;

[0027] Figure 3 This is a schematic diagram of the system structure of the adjustable load in this invention;

[0028] Figure 4 This is a schematic diagram of the connection structure between the multi-function meter and the AC bus in this invention;

[0029] Figure 5 This is a flowchart illustrating the testing method of the present invention.

[0030] In the diagram: 1. Terminal block, 2. Rectifier power supply, 3. DC bus, 4. Battery pack, 5. DC voltmeter, 6. AC bus, 7. Programmable AC power source, 8. Multifunction meter, 9. Adjustable load, 10. Digital oscilloscope, 11. Harmonic generator module. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0032] Please see Figures 1 to 5 The present invention provides a technical solution:

[0033] A test system for the grid harmonic adaptability of photovoltaic inverters includes a terminal block 1, a rectifier power supply 2, a DC bus 3, a battery pack 4, a DC voltmeter 5, an AC bus 6, a programmable AC source 7, a multifunction meter 8, an adjustable load 9, a digital oscilloscope 10, and a harmonic generation module 11, wherein:

[0034] The terminal block 1 includes an AC power terminal XT1, a DC input terminal XT2, and an AC output terminal XT3. Terminal block 1 is primarily for convenient wiring. The AC input terminal of the rectifier power supply 2 is electrically connected to terminal block 1, and the DC output terminal is electrically connected to the DC bus 3. A circuit breaker Q1 is connected in series between the AC power terminal XT1 and the AC input terminal of the rectifier power supply 2. A fuse FU1 is connected in series between the DC output terminal of the rectifier power supply 2 and the DC bus 3. Circuit breaker Q1 controls the operation of the rectifier power supply 2, ensuring that it is not connected to the power grid during testing, thereby improving test accuracy. The rectifier power supply 2 is a rectifier that converts AC power into DC power, ensuring that the DC bus 3 provides power to the battery pack 4 when its charge is insufficient, thus charging the battery pack 4. The fuse FU1 limits the current, preventing excessive current fluctuations during charging, which could damage the charging battery pack 4 due to excessive current in the DC bus 3.

[0035] The battery pack 4 consists of multiple batteries connected in series, with its output terminal electrically connected to the DC bus 3. Multiple battery packs 4 are provided, each acting as a photovoltaic panel generating electricity, thus simulating the operation of an inverter to the greatest extent possible and reducing interference. A circuit breaker Q2 is connected in series in the circuit connecting the output terminal of the battery pack 4 to the DC bus 3. Each battery pack 4 is controlled by a circuit breaker Q2, which controls whether the corresponding battery pack 4 is in use, thereby adjusting the simulated photovoltaic panel usage as needed. A DC voltmeter 5 is electrically connected to the DC bus 3 to display the voltage on the DC bus 3. The DC input terminal XT2 is electrically connected to the DC bus 3. A circuit breaker Q3 is connected in series in the circuit connecting the DC input terminal XT2 and the DC bus 3. A fuse FU2 is also connected in series in the circuit connecting the DC input terminal XT2 and the DC bus 3. When in use, the DC input terminal XT2 is electrically connected to the DC input terminal of the inverter under test. In essence, the DC bus 3 of this application is equivalent to the combiner box in photovoltaic power generation and also acts as a DC power source. The circuit breaker Q3 is used to control the DC input of the inverter under test, and the fuse FU2 is used to limit the DC input of the inverter under test to prevent the DC current input to the inverter under test from being too large and causing damage to the inverter.

[0036] An AC output terminal XT3 is electrically connected to the AC bus 6. During use, the AC output terminal XT3 is electrically connected to the AC output terminal of the test inverter. A circuit breaker Q4 is connected in series in the circuit connecting the AC bus 6 and the AC output terminal XT3. The circuit breaker Q4 controls the AC output of the inverter. The output terminal of the programmable AC source 7 is connected in parallel with the AC bus 6. The programmable AC source 7 uses an ES18000W AC power supply. A circuit breaker Q5 is connected in series in the circuit connecting the output terminal of the programmable AC source 7 and the AC bus 6. The circuit breaker Q5 controls whether the power supply of the programmable AC source 7 is input into the AC bus 6. The output of the programmable AC source 7 can be controlled to generate stepped over / under voltage and over / under frequency voltage signals, simulating various possible grid changes such as grid voltage fluctuations, flicker, and frequency fluctuations, thus effectively simulating grid conditions.

[0037] The multifunction meter 8 is electrically connected to the AC bus 6. A current transformer is fitted on the AC bus 6. The current sampling terminal of the multifunction meter 8 is electrically connected to the current transformer. The voltage sampling terminal of the multifunction meter 8 is directly connected in parallel to the AC bus 6. The multifunction meter 8 is a Sync-D series multifunction power meter used to measure and display the voltage, current, and reactive power of the AC bus 6. The sampling terminal of the digital oscilloscope 10 is electrically connected to the AC bus 6 and used to display the voltage and current waveforms of the AC bus 6. The digital oscilloscope 10 is a wideband digital oscilloscope with an analog input channel. It is mainly used for functions such as capturing the action time of various protection functions, recording the output voltage and current waveforms of low voltage ride-through tests, and recording the tracking process of maximum power point tracking tests. It can completely display the electrical parameters of the AC bus 6. In this embodiment, the AC bus 6 is equivalent to the power grid connected to the photovoltaic power generation.

[0038] The adjustable load 9 is connected in parallel with the AC bus 6, serving as a capacitive and inductive load consuming the reactive and active power of the AC bus. The adjustable load 9 comprises three types of loads: an adjustable capacitor C3 and a load resistor R2 connected in series; an adjustable inductor L2 and a load resistor R2 connected in series; and an adjustable inductor L3 connected in series with an adjustable capacitor C4 and a load resistor R2. All three types of loads are connected in parallel to the AC bus 6. These three types of loads can simulate the inductive and capacitive reactance of various loads in the power grid. The capacitive reactance values ​​of the adjustable capacitors C3 and C4 and the adjustable inductors L2 and L3 are... The inductive reactance values ​​are all adjustable, which can simulate various load conditions in the power grid. The load formed by the adjustable capacitor C3 and the load resistor R2 connected in series is electrically connected to the AC bus 6 through the circuit breaker Q7. The load formed by the adjustable inductor L2 and the load resistor R2 connected in series is electrically connected to the AC bus 6 through the circuit breaker Q8. The load formed by the adjustable inductor L3, the adjustable capacitor C4, and the load resistor R2 connected in series is electrically connected to the AC bus 6 through the circuit breaker Q9. The circuit breakers Q7, Q8, and Q9 can control the connection and disconnection of the three types of loads to meet the requirements.

[0039] The harmonic generation module 11 is electrically connected to the AC bus 6 and is used to generate harmonics and inject them into the AC bus 6. The harmonic generation module 11 includes a controller, a drive circuit, an H-bridge composed of transistors S1, S2, S3, S4 and diodes D1, D2, D3, D4, and a DC energy storage capacitor C1. The input terminal of the H-bridge is electrically connected to the DC bus 3, and the output terminal is electrically connected to the AC bus 6. The controller is based on a DSP chip based on TMS320F2812, and the drive circuit uses a PWM circuit. The controller sends a control signal to the drive circuit. The drive circuit is electrically connected to the bases of transistors S1, S2, S3, and S4 to control the switching of transistors S1, S2, S3, and S4, thereby performing DC power in a manner similar to an inverter and generating harmonic signals at the output. The DC energy storage capacitor C1 is connected in parallel to the input of the H-bridge. The input of the H-bridge is electrically connected to the DC bus 3 through the circuit breaker Q6. The DC bus 3 serves as the input power supply for the H-bridge. The circuit breaker Q6 controls whether the harmonic generation module 11 is activated.

[0040] A resonant circuit is connected in parallel to the output of the H-bridge. The resonant circuit includes a resonant inductor L1, a changeover switch QS, a resonant resistor R1, and a capacitor bank. The inductor L1, changeover switch QS, resonant resistor R1, and capacitor bank are connected in series at the output of the H-bridge. The capacitor bank consists of several resonant capacitors C2 connected in parallel with different capacitive reactance values. Each resonant capacitor C2 is connected in series with a moving contact of the changeover switch QS. Rotating the changeover switch QS can engage resonant capacitors C2 with different capacitive reactance values. The resonant inductor L1, resonant resistor R1, and resonant capacitor C2 form an RLC oscillation circuit, ensuring the stability of the resonant signal. This embodiment can simulate the actual working conditions of the inverter to the greatest extent and can test the adaptability of the photovoltaic inverter under various harmonic conditions. The test results are good and the accuracy is high.

[0041] Please see Figure 5 The present invention also provides a test method for the grid harmonic adaptability of photovoltaic inverters, wherein the test method is applicable to the above-mentioned test system, and the specific steps include:

[0042] S1: Electrically connect the DC input terminal and DC input terminal XT2 of the inverter under test, and electrically connect the AC output terminal and AC output terminal XT3.

[0043] S2: Turn on the programmable AC source 7 to supply power to the AC bus 6, and control the programmable AC source 7 to simulate various possible changes in the power grid, such as voltage fluctuations, flicker, and frequency fluctuations.

[0044] S3: Deploy the appropriate number of battery packs 4 as needed, and let the battery packs 4 supply power to the DC bus 3, simulating the situation of photovoltaic array power generation.

[0045] S4: Enable the inverter under test to operate. The inverter converts the DC power generated by the battery pack 4 into AC power and connects the converted AC power to the AC bus 6 for grid connection.

[0046] S5: Adjust the capacitive and inductive reactance of the adjustable load 9 to simulate the usage of various loads in the power grid, generate power grid harmonics through the harmonic generation module 11, and inject the harmonics into the AC bus 6.

[0047] S6: Use the digital oscilloscope 10 and multifunction meter 8 to view the grid conditions after the inverter is connected to the grid, thereby obtaining the grid harmonic adaptability of the inverter under test.

[0048] S7: After the test is completed, remove the inverter to be tested, connect the mains terminal XT1 to the mains power, and the rectifier power supply 2 converts the mains power into DC power and injects it into the DC bus 3 to charge the battery pack 4 connected to the DC bus 3.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A test system for grid harmonic adaptability of photovoltaic inverters, comprising terminal blocks (1), rectifier power supply (2), DC bus (3), battery pack (4), DC voltmeter (5), AC bus (6), programmable AC source (7), multifunction meter (8), adjustable load (9), digital oscilloscope (10), and harmonic generation module (11), characterized in that: The terminal block (1) includes an AC power terminal XT1, a DC input terminal XT2 and an AC output terminal XT3. The AC input terminal of the rectifier power supply (2) is electrically connected to the terminal block (1), and the DC output terminal is electrically connected to the DC bus (3). The battery pack (4) is composed of multiple batteries connected in series, and its output terminal is electrically connected to the DC bus (3). A DC voltmeter (5) is electrically connected to the DC bus (3). The DC input terminal XT2 is electrically connected to the DC bus (3). The AC bus (6) is electrically connected to an AC output terminal XT3. The output terminal of the programmable AC source (7) is connected in parallel with the AC bus (6) and is used as an AC source to simulate grid voltage fluctuations, flicker, and frequency fluctuations. The multifunction meter (8) is electrically connected to the AC bus (6) and is used to measure and display the voltage, current, and reactive power of the AC bus (6). The adjustable load (9) is connected in parallel with the AC bus (6) and is used as a capacitive and inductive load that consumes the reactive and active power of the AC bus. The sampling terminal of the digital oscilloscope (10) is electrically connected to the AC bus (6) and is used to display the voltage and current waveforms of the AC bus (6). The harmonic generation module (11) is electrically connected to the AC bus (6) and is used to generate harmonics and inject them into the AC bus (6).

2. The test system for grid harmonic adaptability of photovoltaic inverters according to claim 1, characterized in that: A circuit breaker Q1 is connected in series in the circuit between the AC input terminal of the mains power terminal XT1 and the AC input terminal of the rectifier power supply (2). A circuit breaker Q2 is connected in series in the circuit between the output terminal of the battery pack (4) and the DC bus (3). A circuit breaker Q3 is connected in series in the circuit between the DC input terminal XT2 and the DC bus (3). A circuit breaker Q4 is connected in series in the circuit between the AC bus (6) and the AC output terminal XT3. A circuit breaker Q5 is connected in series in the circuit between the output terminal of the programmable AC source (7) and the AC bus (6) in parallel.

3. The test system for grid harmonic adaptability of photovoltaic inverters according to claim 2, characterized in that: A fuse FU1 is connected in series on the circuit that electrically connects the DC output terminal of the rectifier power supply (2) and the DC bus (3), and a fuse FU2 is also connected in series on the circuit that electrically connects the DC input terminal XT2 and the DC bus (3).

4. The test system for grid harmonic adaptability of photovoltaic inverters according to claim 1, characterized in that: A current transformer is fitted on the AC bus (6), and the current sampling terminal of the multifunction meter (8) is electrically connected to the current transformer.

5. A test system for grid harmonic adaptability of photovoltaic inverters according to claim 1, characterized in that: The adjustable load (9) includes three types of loads: adjustable capacitor C3 and load resistor R2 connected in series, adjustable inductor L2 and load resistor R2 connected in series, and adjustable inductor L3 connected in series with adjustable capacitor C4 and load resistor R2. All three types of loads are connected in parallel on the AC bus (6). The load formed by adjustable capacitor C3 and load resistor R2 connected in series is electrically connected to the AC bus (6) through circuit breaker Q7. The load formed by adjustable inductor L2 and load resistor R2 connected in series is electrically connected to the AC bus (6) through circuit breaker Q8. The load formed by adjustable inductor L3, adjustable capacitor C4 and load resistor R2 connected in series is electrically connected to the AC bus (6) through circuit breaker Q9.

6. A test system for grid harmonic adaptability of photovoltaic inverters according to claim 1, characterized in that: The harmonic generation module (11) includes a controller, a drive circuit, an H-bridge composed of transistors S1, S2, S3, S4 and diodes D1, D2, D3, D4, and a DC energy storage capacitor C1. The input terminal of the H-bridge is electrically connected to the DC bus (3), and the output terminal is electrically connected to the AC bus (6). The controller sends a control signal to the drive circuit. The drive circuit is electrically connected to the bases of transistors S1, S2, S3, S4 to control the switching of transistors S1, S2, S3, S4. The DC energy storage capacitor C1 is connected in parallel to the input terminal of the H-bridge. The input terminal of the H-bridge is electrically connected to the DC bus (3) through a circuit breaker Q6.

7. A test system for grid harmonic adaptability of photovoltaic inverters according to claim 6, characterized in that: The output terminal of the H-bridge is connected in parallel with a resonant circuit. The resonant circuit includes a resonant inductor L1, a changeover switch QS, a resonant resistor R1, and a capacitor bank. The inductor L1, the changeover switch QS, the resonant resistor R1, and the capacitor bank are connected in series at the output terminal of the H-bridge. The capacitor bank consists of several resonant capacitors C2 connected in parallel. Each resonant capacitor C2 is connected in series with a moving contact of the changeover switch QS.

8. A test method for the grid harmonic adaptability of photovoltaic inverters, characterized in that: The testing method is applicable to the testing system according to any one of claims 1-7, and the specific steps include: S1: Electrically connect the DC input terminal and DC input terminal XT2 of the inverter to be tested, and electrically connect the AC output terminal and AC output terminal XT3. S2: Turn on the programmable AC source (7) to supply power to the AC bus (6) and control the programmable AC source (7) to simulate various possible changes in the power grid, such as voltage fluctuations, flicker, and frequency fluctuations. S3: Invest the appropriate number of battery packs (4) according to the demand, so that the battery packs (4) can supply power to the DC bus (3) to simulate the power generation of the photovoltaic array; S4: The inverter to be tested is put into operation. The inverter converts the DC power generated by the battery pack (4) into AC power and connects the converted AC power to the AC bus (6) to the grid. S5: Adjust the capacitive and inductive reactance of the adjustable load (9) to simulate the usage of various loads in the power grid, generate power grid harmonics through the harmonic generation module (11), and inject the harmonics into the AC bus (6); S6: Use a digital oscilloscope (10) and a multi-function meter (8) to check the grid conditions after the inverter is connected to the grid, and thus determine the grid harmonic adaptability of the inverter under test; S7: After the test is completed, remove the inverter to be tested, connect the mains terminal XT1 to the mains power, and the rectifier power supply (2) converts the mains power into DC power and injects it into the DC bus (3) to charge the battery pack (4) connected to the DC bus (3).

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