Test system of network-forming converter

Abstract

The invention discloses a test system for a network-forming converter. The test system comprises network-forming test equipment, a bypass switch and a power grid simulator, the output end of the network-forming converter is connected with the output end of the power grid simulator through the bypass switch, the input end of the power grid simulator is connected into a power grid, the input end of the network-forming test equipment is connected with the output end of the power grid simulator, and the output end of the network-forming test equipment is connected with the output end of the network-forming converter; the bypass switch is closed, the network construction test equipment does not operate, the output voltage and the output frequency of the power grid simulator are executed according to set instruction values, and the frequency and voltage regulation characteristics of the network construction type converter are tested; the bypass switch is switched off, the network construction test equipment operates, the power grid simulator operates or bypasses to the power grid, and the network construction test equipment is set according to test requirements to test the output impedance characteristic and the power grid adaptive capacity of the network construction type converter; the method has the advantages that the output characteristics and the network construction capability of the network construction type converter are detected.

Description

Technical Field

[0001] The present invention relates to the field of converter testing, and particularly to a testing system for a network-forming converter. Background Art

[0002] In order to provide the stability of new energy grid connection under high penetration, more and more converters are switched from grid-following control to network-forming control. The main feature of grid-following control is that the output voltage, frequency, and phase of the converter change following the grid, and its output characteristics mostly present as a current source characteristic with high impedance; while the main feature of network-forming control is that the output voltage, frequency, and phase of the converter are autonomously adjusted by the converter according to parameters such as active and reactive power output by itself, and its output characteristics mostly present as a voltage source characteristic with low impedance.

[0003] For a network-forming converter, due to its low-impedance voltage source characteristic, it can greatly improve the stability of the new energy grid connection system under high penetration during grid-connected operation. However, there is currently no good solution to detect the output characteristics and network-forming ability of the network-forming converter. Chinese Patent Publication No. CN119556585A discloses a hardware-in-the-loop simulation testing method and device for a network-forming energy storage converter, which adjusts the control parameters of the simulated energy storage system and the grid simulation device to achieve various types of hardware-in-the-loop testing and semi-physical testing such as fault ride-through testing, power adaptability testing, and black start testing, but it cannot detect the output characteristics and network-forming ability of the network-forming converter. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the prior art cannot detect the output characteristics and network-forming ability of the network-forming converter.

[0005] The present invention solves the above technical problems by the following technical means: A testing system for a network-forming converter, comprising a network-forming testing device, a bypass switch, and a grid simulator; the output end of the network-forming converter is connected to the output end of the grid simulator through the bypass switch, the input end of the grid simulator is connected to the grid, the input end of the network-forming testing device is connected to the output end of the grid simulator, and the output end of the network-forming testing device is connected to the output end of the network-forming converter; the testing system for the network-forming converter is used to test the frequency modulation and voltage regulation characteristics, output impedance characteristics, and grid adaptation ability of the network-forming converter.

[0006] Further, when the bypass switch is closed and the network-forming testing device does not operate, the output voltage and output frequency of the grid simulator are executed according to the set command values to test the frequency modulation and voltage regulation characteristics of the network-forming converter.

[0007] Further, the bypass switch is disconnected, the network-forming test equipment operates, the grid simulator operates or is bypassed to the grid, the network-forming test equipment is set according to the test requirements, and the output impedance characteristics and grid adaptability of the network-forming converter are tested.

[0008] Furthermore, the frequency and voltage regulation characteristics include frequency regulation characteristics. When testing the frequency regulation characteristics of the network-forming converter, the bypass switch is closed, the network-forming test equipment does not operate, the output voltage of the grid simulator is executed according to the preset voltage, and the output frequency changes according to the preset frequency requirements. The relationship characteristic curve of the active power of the network-forming converter changing with frequency is detected; the relationship characteristic curve of the active power changing with frequency matches the first standard curve. If the deviation between the two is within the first preset range, the frequency regulation characteristics are good; otherwise, the frequency regulation characteristics are poor.

[0009] Furthermore, the frequency and voltage regulation characteristics include voltage regulation characteristics. When testing the voltage regulation characteristics of the network-forming converter, the bypass switch is closed, the network-forming test equipment does not operate, the output frequency of the grid simulator is executed according to the preset frequency, and the output voltage changes according to the preset voltage requirements. The relationship characteristic curve of the reactive power of the network-forming converter changing with the output voltage is detected. The relationship characteristic curve of the reactive power changing with the output voltage matches the second standard curve. If the deviation between the two is within the second preset range, the voltage regulation characteristics are good; otherwise, the voltage regulation characteristics are poor.

[0010] Furthermore, testing the output impedance characteristics of the network-forming converter includes:

[0011] The bypass switch is disconnected, the network-forming test equipment operates, the grid simulator operates or the grid simulator is bypassed to the grid. The network-forming test equipment superimposes a voltage with a fixed frequency or multiple fixed frequencies, or superimposes a voltage with a variable frequency or multiple variable frequencies on the basis of its input voltage, and detects the output impedance of the network-forming converter under different frequency points and different frequency bands to obtain the output impedance frequency characteristic curve of the network-forming converter, thereby detecting the output impedance characteristics of the network-forming converter.

[0012] Furthermore, testing the grid adaptability of the network-forming converter includes detecting the adaptability of the network-forming converter under different grid circuit impedances. The detection of the adaptability of the network-forming converter under different grid circuit impedances includes:

[0013] The bypass switch is disconnected, the network-forming test equipment operates, the grid simulator operates or the grid simulator is bypassed to the grid. The network-forming test equipment simulates the line impedance of the grid on the basis of its input voltage, and detects whether the network-forming converter can operate normally under different grid circuit impedances by changing the value of the line impedance simulated and set by the network-forming test equipment, thereby detecting the adaptability of the network-forming converter under different grid circuit impedances.

[0014] Furthermore, testing the grid adaptability of the grid-forming converter includes detecting the harmonic adaptability of the grid-forming converter. Detecting the harmonic adaptability of the grid-forming converter includes:

[0015] The bypass switch is disconnected, the grid-forming test equipment is operating, the grid simulator is operating or the grid simulator is bypassed to the grid. The grid-forming test equipment superimposes a voltage with a fixed frequency or multiple fixed frequencies on its input voltage, and detects whether the output harmonic current of the grid-forming converter exceeds the limit value specified by the grid. If so, the harmonic adaptability of the grid-forming converter is poor; otherwise, the harmonic adaptability is good. Or it is detected whether the grid-forming converter can operate normally. If so, the harmonic adaptability of the grid-forming converter is good; otherwise, the harmonic adaptability is poor.

[0016] Furthermore, testing the grid adaptability of the grid-forming converter includes detecting the harmonic adaptability of the grid-forming converter. Detecting the harmonic adaptability of the grid-forming converter includes:

[0017] The bypass switch is closed, the grid-forming test equipment is not operating, the fundamental wave frequency and harmonic content of the output voltage of the grid simulator are adjusted, and it is detected whether the output harmonic current of the grid-forming converter exceeds the limit value specified by the grid. If so, the harmonic adaptability of the grid-forming converter is poor; otherwise, the harmonic adaptability is good. Or it is detected whether the grid-forming converter can continuously operate normally. If so, the harmonic adaptability of the grid-forming converter is good; otherwise, the harmonic adaptability is poor.

[0018] Furthermore, testing the grid adaptability of the grid-forming converter includes detecting the voltage tolerance ability of the grid-forming converter. Detecting the voltage tolerance ability of the grid-forming converter includes:

[0019] The bypass switch is disconnected, the grid-forming test equipment is operating, the grid simulator is operating or the grid simulator is bypassed to the grid. The grid-forming test equipment superimposes a preset voltage on its input voltage, determines when the grid-forming converter cannot operate normally, and obtains the tolerance limit of the grid-forming converter, so as to detect the voltage tolerance ability of the grid-forming converter.

[0020] Furthermore, testing the grid adaptability of the grid-forming converter includes detecting the voltage tolerance ability of the grid-forming converter. Detecting the voltage tolerance ability of the grid-forming converter includes:

[0021] The bypass switch is closed, the grid-forming test equipment is not operating, the output voltage of the grid simulator is adjusted, the time for the grid-forming converter to continuously and stably operate is recorded, and it is determined when the grid-forming converter cannot operate normally, and the tolerance limit of the grid-forming converter is obtained, so as to detect the voltage tolerance ability of the grid-forming converter.

[0022] Further, the test system also improves the power quality of the power grid. The specific process is as follows:

[0023] When the bypass switch is disconnected, the grid-forming test equipment operates, the grid simulator operates or is bypassed to the power grid. The grid-forming test equipment reversely superimposes high-order harmonic voltages other than the fundamental voltage input on the basis of its input voltage. The reversely superimposed high-order voltages cancel out the harmonic voltages of the power grid, thereby improving the power quality of the power grid input at the output port of the grid-forming converter; the grid-forming test equipment reversely superimposing high-order harmonic voltages other than the fundamental voltage input means that the grid-forming test equipment superimposes a set of high-order harmonic voltages with the same amplitude as the input high-order harmonic voltage and a phase difference of 180° on the basis of its input fundamental voltage.

[0024] The advantages of the present invention are as follows:

[0025] The present invention provides a test system for a grid-forming converter, which is used to test the frequency modulation and voltage regulation characteristics, output impedance characteristics and grid adaptation ability of the grid-forming converter, and solves the problem that the prior art cannot detect the output characteristics and grid-forming ability of the grid-forming converter.

[0026] By closing the bypass switch, the grid-forming test equipment does not operate, and the output voltage and output frequency of the grid simulator are executed according to the test requirements to test the frequency modulation and voltage regulation characteristics of the grid-forming converter, thereby detecting the output characteristics of the grid-forming converter; when the bypass switch is disconnected, the grid simulator operates or is bypassed to the power grid, and the grid-forming test equipment is set according to the test requirements to test the output impedance characteristics and grid adaptation ability of the grid-forming converter, thereby detecting the grid-forming ability of the grid-forming converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of a test system for a grid-forming converter disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] Such as Figure 1As shown in the figure, the present invention provides a test system for a network-forming converter, which includes a bypass switch 2, a grid simulator 3, and a network-forming test device 4. The network-forming converter 1 is directly supplied with direct current through a photovoltaic module 5 and a storage battery 6. The output end of the network-forming converter 1 is connected to the output end of the grid simulator 3 through the bypass switch 2. The input end of the grid simulator 3 is connected to the power grid. The input end of the network-forming test device 4 is connected to the output end of the grid simulator 3, and the output end of the network-forming test device 4 is connected to the output end of the network-forming converter 1. The network-forming test device 4 is a test power source, but it is only applied in the test field of the network-forming converter 1, so it is named the network-forming test device 4. This embodiment includes testing the output characteristics and network-forming ability of the network-forming converter 1, where the output characteristics and network-forming ability mainly include frequency modulation and voltage regulation characteristics, output impedance characteristics, and grid adaptability. Details are as follows.

[0030] When testing the frequency modulation and voltage regulation characteristics of the network-forming converter 1, the bypass switch 2 is closed, the network-forming test device 4 does not operate, and the output voltage and frequency of the grid simulator 3 are executed according to the set parameters required by the test. The test process of the frequency modulation and voltage regulation characteristics is as follows:

[0031] The frequency modulation and voltage regulation characteristics include frequency modulation characteristics. When testing the frequency modulation characteristics of the network-forming converter 1, the bypass switch 2 is closed, the network-forming test device 4 does not operate, the output voltage of the grid simulator 3 is executed according to the preset voltage, the output frequency changes according to the preset frequency requirements, and the relationship characteristic curve of the active power of the network-forming converter 1 changing with the frequency is detected; the relationship characteristic curve of the active power changing with the frequency matches the first standard curve. If the deviation between the two is within the first preset range, the frequency modulation characteristics are good; otherwise, the frequency modulation characteristics are poor.

[0032] The frequency modulation and voltage regulation characteristics include voltage regulation characteristics. When testing the voltage regulation characteristics of the network-forming converter 1, the bypass switch 2 is closed, the network-forming test device 4 does not operate, the output frequency of the grid simulator 3 is executed according to the preset frequency, the output voltage changes according to the preset voltage requirements, and the relationship characteristic curve of the reactive power of the network-forming converter 1 changing with the output voltage is detected. The relationship characteristic curve of the reactive power changing with the output voltage matches the second standard curve. If the deviation between the two is within the second preset range, the voltage regulation characteristics are good; otherwise, the voltage regulation characteristics are poor.

[0033] The above embodiments are for the test system with the bypass switch 2 and the network-forming test device 4. Since the closing of the bypass switch 2 is equivalent to the direct connection between the output of the network-forming converter 1 and the output of the grid simulator 3, therefore, regardless of whether the output of the network-forming converter 1 is directly connected to the output of the grid simulator 3 or not, as long as the frequency modulation and voltage regulation characteristics of the network-forming converter 1 are tested according to the above embodiment scheme, they are within the protection scope of this application.

[0034] When testing the output impedance characteristics of the network-forming converter 1, the bypass switch 2 is disconnected, the network-forming test equipment 4 operates, and the grid simulator 3 operates or the grid simulator 3 is bypassed to the grid. The detailed test process is as follows:

[0035] The network-forming test equipment 4 superimposes a voltage output with a fixed frequency or multiple fixed frequencies on the basis of its input voltage, or superimposes a voltage output with a variable frequency or multiple variable frequencies, and detects the output impedance of the network-forming converter 1 under different frequency points and different frequency bands, so as to detect the characteristic curve of the output impedance of the network-forming converter 1 changing with frequency; at each frequency point, the smaller the output impedance of the network-forming converter 1, the stronger the network-forming ability.

[0036] When testing the grid adaptability of the network-forming converter 1, the bypass switch 2 is disconnected, the network-forming test equipment 4 operates, and the grid simulator 3 operates or the grid simulator 3 is bypassed to the grid. The detailed test process is as follows:

[0037] The grid adaptability includes the adaptability under different grid circuit impedances. When testing the adaptability of the network-forming converter 1 under different grid circuit impedances, the network-forming test equipment 4 simulates the line impedance of the grid on the basis of its input voltage and then outputs it to the output of the network-forming converter 1. By changing the value of the line impedance simulated and set by the network-forming test equipment 4, it is detected whether the network-forming converter 1 can operate normally under different grid circuit impedances, so as to detect the adaptability of the network-forming converter 1 under different grid circuit impedances. In practical applications, the adaptability is judged by setting the line impedance range. If the network-forming converter 1 can operate normally within the set line impedance range, it means that the network-forming converter 1 has good adaptability under the set line impedance range.

[0038] As a further improved solution, the grid adaptability further includes harmonic adaptability. When testing the harmonic adaptability of the network-forming converter 1 under different grid voltage harmonics, the network-forming test equipment 4 superimposes a voltage output with a fixed frequency or multiple fixed frequencies on the basis of its input voltage, and detects whether the output harmonic current of the network-forming converter 1 exceeds the limit value specified by the grid. If so, the harmonic adaptability of the network-forming converter 1 is poor; otherwise, the harmonic adaptability is good; or it is detected whether the network-forming converter can operate normally. If so, the harmonic adaptability of the network-forming converter is good; otherwise, the harmonic adaptability is poor.

[0039] As a further improved solution, the grid adaptability further includes voltage tolerance ability. When testing the voltage tolerance ability of the network-forming converter 1, the network-forming test equipment 4 superimposes a preset voltage output on the basis of its input voltage, judges when the network-forming converter 1 cannot operate normally, and obtains the tolerance limit of the network-forming converter 1, so as to detect the voltage tolerance ability of the network-forming converter 1.

[0040] When testing the harmonic adaptability and voltage tolerance of the grid-connected converter 1, the bypass switch 2 can also be closed, the grid-connected test equipment 4 does not operate, and the output voltage and frequency of the grid simulator 3 are adjusted to complete the test. Specifically, to detect the harmonic adaptability of the grid-connected converter 1, it includes:

[0041] Close the bypass switch 2, the grid-connected test equipment 4 does not operate, adjust the fundamental wave frequency and harmonic content of the output voltage of the grid simulator 3, and detect whether the output harmonic current of the grid-connected converter 1 exceeds the limit value specified by the grid. If so, the harmonic adaptability of the grid-connected converter 1 is poor; otherwise, the harmonic adaptability is good. Or detect whether the grid-connected converter 1 can operate normally. If so, the harmonic adaptability of the grid-connected converter 1 is good; otherwise, the harmonic adaptability is poor.

[0042] To detect the voltage tolerance of the grid-connected converter 1, it includes:

[0043] Close the bypass switch 2, the grid-connected test equipment 4 does not operate, adjust the output voltage of the grid simulator 3, record the time that the grid-connected converter 1 can continuously and stably operate, judge when the grid-connected converter 1 cannot operate normally, and obtain the tolerance limit of the grid-connected converter 1, so as to detect the voltage tolerance of the grid-connected converter 1.

[0044] The above embodiments are the embodiments for detecting the grid-forming characteristics and grid-forming capabilities listed in this application. However, a test system for a grid-connected converter provided by this application can not only detect the grid-forming characteristics and grid-forming capabilities of the grid-connected converter, but also improve the voltage power quality of the output port of the grid-connected converter to be tested.

[0045] When the bypass switch 2 is disconnected, the grid-connected test equipment 4 operates, the grid simulator 3 operates or the grid simulator 3 is bypassed to the grid. The grid-connected test equipment 4 reversely superimposes a high-order voltage input other than the fundamental voltage input on the basis of its input voltage. The reversely superimposed high-order voltage cancels out the harmonic voltage of the grid, thereby improving the power quality of the grid input at the output port of the grid-connected converter 1 to be tested. The grid-connected test equipment 4 reversely superimposing a high-order harmonic voltage other than the fundamental voltage input means that the grid-connected test equipment 4 superimposes a group of high-order harmonic voltages with the same amplitude as its input high-order harmonic voltage and a phase difference of 180° on the basis of its input fundamental voltage.

[0046] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A test system for a network-forming converter, characterized in that, It includes a network-forming test device, a bypass switch, and a power grid simulator; the output end of the network-forming converter is connected to the output end of the power grid simulator through the bypass switch, the input end of the power grid simulator is connected to the power grid, the input end of the network-forming test device is connected to the output end of the power grid simulator, and the output end of the network-forming test device is connected to the output end of the network-forming converter; the test system of the network-forming converter is used to test the frequency modulation and voltage regulation characteristics, output impedance characteristics, and grid adaptation ability of the network-forming converter.

2. The test system for a network-forming converter according to claim 1, characterized in that, When the bypass switch is closed and the network-forming test device is not operating, the output voltage and output frequency of the power grid simulator are executed according to the set command values to test the frequency modulation and voltage regulation characteristics of the network-forming converter.

3. The test system for a network-forming converter according to claim 1, characterized in that, When the bypass switch is opened, the network-forming test device operates, the power grid simulator operates or is bypassed to the power grid, and the network-forming test device is set according to the test requirements to test the output impedance characteristics and grid adaptation ability of the network-forming converter.

4. The test system of a network-forming converter according to claim 2, characterized in that, The frequency modulation and voltage regulation characteristics include frequency modulation characteristics. When testing the frequency modulation characteristics of the network-forming converter, the bypass switch is closed and the network-forming test device does not operate. The output voltage of the power grid simulator is executed according to the preset voltage, and the output frequency changes according to the preset frequency requirements. The relationship characteristic curve of the active power of the network-forming converter changing with frequency is detected; the relationship characteristic curve of the active power changing with frequency matches the first standard curve. If the deviation between the two is within the first preset range, the frequency modulation characteristics are good; otherwise, the frequency modulation characteristics are poor.

5. The test system for a network-forming converter according to claim 2, characterized in that, The frequency modulation and voltage regulation characteristics include voltage regulation characteristics. When testing the voltage regulation characteristics of the network-forming converter, the bypass switch is closed and the network-forming test device does not operate. The output frequency of the power grid simulator is executed according to the preset frequency, and the output voltage changes according to the preset voltage requirements. The relationship characteristic curve of the reactive power of the network-forming converter changing with the output voltage is detected. The relationship characteristic curve of the reactive power changing with the output voltage matches the second standard curve. If the deviation between the two is within the second preset range, the voltage regulation characteristics are good; otherwise, the voltage regulation characteristics are poor.

6. The test system for a network-forming converter according to claim 3, characterized in that The testing of the output impedance characteristics of the network-forming converter includes: When the bypass switch is opened, the network-forming test device operates, the power grid simulator operates or the power grid simulator is bypassed to the power grid. The network-forming test device superimposes a voltage with a fixed frequency or multiple fixed frequencies, or superimposes a voltage with a variable frequency or multiple variable frequencies on the basis of its input voltage, and detects the output impedance of the network-forming converter at different frequency points, so as to obtain the output impedance frequency characteristic curve of the network-forming converter.

7. The test system for a network-forming converter according to claim 3, characterized in that, Testing the grid adaptation ability of the network-forming converter includes detecting the adaptation ability of the network-forming converter under different grid circuit impedances. Detecting the adaptation ability of the network-forming converter under different grid circuit impedances includes: When the bypass switch is opened, the network-forming test device operates, the power grid simulator operates or the power grid simulator is bypassed to the power grid. The network-forming test device simulates the line impedance of the power grid on the basis of its input voltage, and detects whether the network-forming converter can operate normally under different grid circuit impedances by changing the value of the line impedance simulated and set by the network-forming test device, so as to detect the adaptation ability of the network-forming converter under different grid circuit impedances.

8. The test system for a network-forming converter according to claim 3, characterized in that, Testing the grid adaptability of a grid-forming converter includes detecting the harmonic adaptability of the grid-forming converter. Detecting the harmonic adaptability of the grid-forming converter includes: The bypass switch is disconnected, the grid-forming test equipment is operating, the grid simulator is operating or the grid simulator is bypassed to the grid. The grid-forming test equipment superimposes a voltage with a fixed frequency or multiple fixed frequencies on the basis of its input voltage, and detects whether the output harmonic current of the grid-forming converter exceeds the limit value specified by the grid. If so, the harmonic adaptability of the grid-forming converter is poor; otherwise, the harmonic adaptability is good. Or it is detected whether the grid-forming converter can operate normally. If so, the harmonic adaptability of the grid-forming converter is good; otherwise, the harmonic adaptability is poor.

9. The test system for a network-forming converter according to claim 3, characterized in that, Testing the grid adaptability of a grid-forming converter includes detecting the harmonic adaptability of the grid-forming converter. Detecting the harmonic adaptability of the grid-forming converter includes: The bypass switch is closed, the grid-forming test equipment is not operating, the fundamental wave frequency and harmonic content of the output voltage of the grid simulator are adjusted, and it is detected whether the output harmonic current of the grid-forming converter exceeds the limit value specified by the grid. If so, the harmonic adaptability of the grid-forming converter is poor; otherwise, the harmonic adaptability is good. Or it is detected whether the grid-forming converter can operate normally. If so, the harmonic adaptability of the grid-forming converter is good; otherwise, the harmonic adaptability is poor.

10. The test system for a network-forming converter according to claim 3, characterized in that, Testing the grid adaptability of a grid-forming converter includes detecting the voltage tolerance ability of the grid-forming converter. Detecting the voltage tolerance ability of the grid-forming converter includes: The bypass switch is disconnected, the grid-forming test equipment is operating, the grid simulator is operating or the grid simulator is bypassed to the grid. The grid-forming test equipment superimposes a preset voltage on the basis of its input voltage, records the continuous and stable operation time of the grid-forming converter, and obtains the tolerance limit of the grid-forming converter, so as to detect the voltage tolerance ability of the grid-forming converter.

11. The test system of a network-forming converter according to claim 3, characterized in that, Testing the grid adaptability of a grid-forming converter includes detecting the voltage tolerance ability of the grid-forming converter. Detecting the voltage tolerance ability of the grid-forming converter includes: The bypass switch is closed, the grid-forming test equipment is not operating, the output voltage and frequency of the grid simulator are adjusted, and it is judged when the grid-forming converter cannot operate normally, and the tolerance limit of the grid-forming converter is obtained, so as to detect the voltage tolerance ability of the grid-forming converter.

12. The test system for a network-forming converter according to claim 3, characterized in that, The test system also improves the power quality of the grid. The specific process is as follows: When the bypass switch is disconnected, the grid-forming test equipment is operating, the grid simulator is operating or the grid simulator is bypassed to the grid, and the grid-forming test equipment reversely superimposes high-order harmonic voltages other than the fundamental voltage input on the basis of its input voltage. The grid-forming test equipment reversely superimposing high-order harmonic voltages other than the fundamental voltage input means that the grid-forming test equipment superimposes a group of high-order harmonic voltages with the same amplitude as the input high-order harmonic voltage and a phase difference of 180° on the basis of its input fundamental voltage.

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