A testing device and method for voltage source operation capability of a wind turbine generator

Abstract

The application provides a kind of testing device and method for wind turbine voltage source operation ability, comprising: grid-connected switch, line impedance simulation and load simulation;Line impedance simulation is in series with grid-connected switch, forms a branch, branch is connected between the box transformer high voltage side of the wind turbine to be tested and grid-connected point in series, for testing the weak grid adaptation of wind turbine;Load simulation is connected in parallel to the box transformer high voltage side of the wind turbine to be tested, for testing the off-grid operation ability and black start ability of wind turbine;Wherein, wind turbine voltage source operation ability includes weak grid adaptation, off-grid operation ability and black start ability, different load types include one or more of the following: constant power load, constant current load and constant impedance load;The application can comprehensively test, detect and evaluate the voltage source operation ability of wind turbine, which makes up for the current lack of equipment and means for testing the voltage source operation ability of wind turbine.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of new energy grid connection and control, and particularly relates to a testing device and method for voltage source operation capability of a wind turbine. BACKGROUND

[0002] In a new type of power system mainly based on new energy, in addition to the traditional operation mode of passively following the power grid, wind turbines should also have the ability of grid building type control and self-network operation, so as to establish the grid voltage and support the system operation, and thus bear the responsibility as the main power source. Therefore, in recent years, the academic and industrial circles have carried out researches on voltage source type wind power grid connection control technology, and through direct control of the amplitude and frequency of the output voltage of the wind turbine, the wind turbine has the external characteristics of voltage source operation and the ability of self-network operation. Based on the related technical researches, the industry has also developed a wind turbine prototype with voltage source control mode and self-network operation capability.

[0003] However, from the perspective of industrial development, there is currently no equipment and means for testing the voltage source operation capability of wind turbines. For the models provided by wind turbine manufacturers, testing agencies cannot test and detect the voltage source operation capability of the wind turbines, and therefore cannot carry out certification and evaluation. This background and status limit the application and promotion of related technologies of voltage source type wind turbines, and restrict the optimization and upgrading of wind power grid connection technology. SUMMARY

[0004] In order to overcome the shortcomings of the prior art, the present application provides a testing device and testing method and system for voltage source operation capability of a wind turbine, comprising:

[0005] a grid connection switch, line impedance simulation and load simulation;

[0006] The line impedance simulation and the grid connection switch are connected in series to form a branch, and the branch is connected in series between the box transformer high voltage side of the wind turbine to be tested and the grid connection point, for simulating different line impedance values and testing the weak grid adaptation capability of the wind turbine voltage source operation capability;

[0007] The load simulation is connected in parallel to the box transformer high voltage side of the wind turbine to be tested, for simulating different load types and testing the off-grid operation capability and black start capability of the wind turbine voltage source operation capability;

[0008] The wind turbine voltage source operation capability includes weak grid adaptation capability, off-grid operation capability and black start capability, and the different load types include one or more of the following: constant power load, constant current load and constant impedance load.

[0009] Preferably, the grid connection switch comprises a grid connection circuit breaker.

[0010] Preferably, the line impedance simulation comprises:

[0011] a plurality of line impedance inductors, a plurality of line impedance switches and a bypass switch;

[0012] the plurality of line impedance inductors are respectively connected in series with corresponding line impedance switches to form a plurality of branches, and the plurality of branches and the bypass switch are connected in parallel;

[0013] wherein the number of line impedance inductors is the same as the number of line impedance switches.

[0014] Preferably, the load simulation comprises:

[0015] a load breaker, a load transformer and a load simulation system;

[0016] one end of the load breaker is connected to the high-voltage side of a transformer of a wind turbine to be tested, and the other end is connected in series with the load transformer and the load simulation system.

[0017] Based on the same concept, the present application also provides a test method for voltage source operation capability of a wind turbine, characterized in that it comprises:

[0018] setting a grid short-circuit ratio required for the wind turbine to be tested according to a rated voltage and a rated power of the wind turbine to be tested and a calculation formula of the grid short-circuit ratio, and calculating a line impedance value required for line impedance simulation in a test device according to the grid short-circuit ratio and a calculation formula of the line impedance;

[0019] testing weak grid adaptation capability of the voltage source operation capability of the wind turbine through the line impedance value and the line impedance simulation in the test device;

[0020] testing off-grid operation capability in the voltage source operation capability of the wind turbine through different load types and the load simulation in the test device;

[0021] testing black start capability in the voltage source operation capability of the wind turbine through different load types and the load simulation in the test device;

[0022] wherein the test device comprises any one of the test devices for voltage source operation capability of a wind turbine as described above.

[0023] Preferably, the line impedance inductor calculation formula comprises a first line impedance inductor calculation formula and other line impedance inductor calculation formulas connected in parallel with the line impedance inductor; wherein the first line impedance inductor calculation formula is as shown in the following formula:

[0024]

[0025] wherein, m = 1, SCRm is the 1st grid short circuit ratio required to be tested for the wind turbine, Xm is the 1st line impedance inductance, V n is the rated voltage of the system to be connected, P n is the rated power of the wind turbine to be tested.

[0026] The calculation formula of other line impedance inductances in parallel with the line impedance inductance is as follows:

[0027]

[0028] wherein, SCRm+1 is the (m+1)th grid short circuit ratio required to be tested for the wind turbine, SCRm is the grid short circuit ratio adjacent to SCRm+1, Xm+1 is the (m+1)th line impedance inductance, V n is the rated voltage of the system to be connected, P n is the rated power of the wind turbine to be tested.

[0029] Preferably, the line impedance simulation part in the grid-connected switch and the testing device simulates the line impedance value to test the weak grid adaptability of the voltage source operation capability of the wind turbine, comprising:

[0030] The grid-connected switch and the bypass switch are closed to directly connect the wind turbine to the grid, when the wind turbine is in the rated operation state, all the line impedance switches are closed and the bypass switch is opened, the first set time length is kept, and whether the wind turbine is off-grid is judged.

[0031] If the wind turbine is off-grid, the test duration and the off-grid time of the wind turbine are recorded; otherwise, one parallel line impedance switch is opened each time in order, the wind turbine is connected to the grid through the remaining parallel line impedance inductance each time, the first set time length is kept, and whether the wind turbine is off-grid is judged.

[0032] If the wind turbine is off-grid, the test duration and the off-grid time of the wind turbine are recorded; otherwise, the wind turbine is stopped, the state of the testing device is kept unchanged, the wind turbine is restarted, the wind turbine is connected to the grid through the first line impedance, the rated operation state is reached and the wind turbine is continuously operated for not less than the second set time length, and whether the wind turbine is off-grid is judged.

[0033] If the wind turbine is off-grid, the test duration and the off-grid time of the wind turbine are recorded; otherwise, it is considered that the wind turbine passes the weak grid adaptability test.

[0034] Preferably, the load simulation part in the grid-connected switch and the testing device simulates different load types to test the off-grid operation capability of the voltage source operation capability of the wind turbine, comprising:

[0035] In the S1 test process, the active power output of the wind turbine under test should be greater than the set proportion of the rated power except for the start-up and grid-connection process;

[0036] The grid-connection switch and the bypass switch are closed and the load breaker is closed, and the load simulation system is adjusted so that the current flowing through the grid-connection switch is less than the first set proportion of the rated current of the wind turbine under test, and after the system is stable, the grid-connection switch is opened;

[0037] In the S2, if the wind turbine under test keeps running, the time interval from the moment when the grid-connection switch is opened to the moment when the output current of the wind turbine reaches the second set proportion of the rated current is measured and step S3 is entered, otherwise, step S5 is entered;

[0038] In the S3, if the wind turbine keeps running, the running duration of the wind turbine is kept not less than the first set time length, the running data of the wind turbine is collected and measured, and step S4 is entered, otherwise, step S5 is entered;

[0039] In the S4, the off-grid running capability test is performed;

[0040] In the S5, the test duration and the off-grid time of the wind turbine are recorded.

[0041] The running data include output voltage, phase deviation, frequency deviation, total harmonic distortion rate of output voltage, unbalance degree of output voltage and fluctuation of output voltage, and the first set proportion is less than the second set proportion.

[0042] Preferably, the black start capability in the voltage source running capability of the wind turbine is tested by simulating different load types through the load simulation part in the testing device, and the testing includes:

[0043] The initial active load and the initial reactive load of the load simulation system are set according to the black start requirement of the wind turbine under test;

[0044] The grid-connection switch is opened, the load breaker is closed, the wind turbine under test is started and runs with load, after the system is stable, the load simulation device is adjusted so that the wind turbine under test reaches the rated running state, the running time is kept not less than the first set time length, if the wind turbine under test is off-grid, the test duration and the off-grid time of the wind turbine are recorded, otherwise, the black start capability test is performed.

[0045] Compared with the closest prior art, the present application has the following beneficial effects:

[0046] The application provides a testing device and method for voltage source operation capability of a wind turbine, comprising: a grid-connected switch, a line impedance simulation and a load simulation; the line impedance simulation is connected in series with the grid-connected switch to form a branch, the branch is connected in series between a box transformer high-voltage side of the wind turbine to be tested and a grid-connected point, and is used for simulating different line impedance values to test weak grid adaptation capability of the wind turbine voltage source operation capability; the load simulation is connected in parallel to the box transformer high-voltage side of the wind turbine to be tested, and is used for simulating different load types to test off-grid operation capability and black start capability in the wind turbine voltage source operation capability; wherein the wind turbine voltage source operation capability comprises weak grid adaptation capability, off-grid operation capability and black start capability, and the different load types comprise one or more of the following: constant power load, constant current load and constant impedance load. The application can test the weak grid adaptation capability of the wind turbine to be tested by providing a testing device and method for the wind turbine, comprehensively test, detect and evaluate the voltage source operation capability of the wind turbine according to the test result, and comprehensively test, detect and evaluate the self-network operation capability and performance of the wind turbine, so as to solve the problem that there is no equipment and means for testing the voltage source operation capability of the wind turbine at present, the testing institution cannot test and detect the voltage source operation capability, and cannot perform authentication and evaluation. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 A testing device structure schematic diagram for voltage source operation capability of a wind turbine provided by the application is shown in the figure, comprising:

[0048] Figure 2 A testing method flowchart schematic diagram for voltage source operation capability of a wind turbine provided by the application is shown in the figure, comprising:

[0049] Figure 3 A reference structure schematic diagram of the testing device for voltage source operation capability of a wind turbine is shown in the figure, comprising:

[0050] Figure 4 A reference structure schematic diagram of the load simulation system is shown in the figure. DETAILED DESCRIPTION

[0051] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings.

[0052] Example 1:

[0053] A testing device structure schematic diagram for voltage source operation capability of a wind turbine provided by the application is shown in the figure, comprising: Figure 1

[0054] A grid-connected switch, a line impedance simulation and a load simulation;

[0055] ​The line impedance simulation is connected in series with the grid connection switch to form a branch, and the branch is connected in series between the high-voltage side of the transformer of the wind turbine to be tested and a grid connection point, for simulating different line impedance values to test the weak grid adaptability of the wind turbine voltage source operation capability.

[0056] The load simulation is connected in parallel to the high-voltage side of the transformer of the wind turbine to be tested, for simulating different load types to test the off-grid operation capability and black start capability of the wind turbine voltage source operation capability.

[0057] The wind turbine voltage source operation capability includes weak grid adaptability, off-grid operation capability and black start capability, and the different load types include one or more of constant power load, constant current load and constant impedance load.

[0058] The reference structure diagram of the test device for the wind turbine voltage source operation capability is shown in Figure 3 .

[0059] The grid connection switch includes a grid connection circuit breaker.

[0060] The line impedance simulation includes:

[0061] A plurality of line impedance inductors, a plurality of line impedance switches and a bypass switch.

[0062] The plurality of line impedance inductors are respectively connected in series with corresponding line impedance switches to form a plurality of branches, and the plurality of branches and the bypass switch are connected in parallel.

[0063] The number of line impedance inductors is the same as the number of line impedance switches.

[0064] The load simulation includes:

[0065] A load circuit breaker, a load transformer and a load simulation system.

[0066] One end of the load circuit breaker is connected to the high-voltage side of the transformer of the wind turbine to be tested, and the other end is connected in series with the load transformer and the load simulation system.

[0067] Embodiment 2:

[0068] Based on the same inventive concept, the present application provides a test method for wind turbine voltage source operation capability, and a test method flow diagram for wind turbine voltage source operation capability is shown in Figure 2 , which includes:

[0069] Step 1: According to the rated voltage and rated power of the wind turbine to be tested, and combining the calculation formula of the short-circuit ratio of the power grid, set the short-circuit ratio required for the wind turbine to be tested, and according to the short-circuit ratio, combine the calculation formula of the line impedance to obtain the line impedance value required to be simulated by the line impedance simulation part of the test device;

[0070] Step 2: Simulate the line impedance value through the line impedance simulation part of the test device, and test the weak grid adaptability of the voltage source operation capability of the wind turbine;

[0071] Step 3: Simulate different load types through the grid-connected switch and the load simulation part of the test device, and test the off-grid operation capability of the voltage source operation capability of the wind turbine

[0072] Step 4: Simulate different load types through the load simulation part of the test device, and test the black start capability of the voltage source operation capability of the wind turbine;

[0073] The test device includes any one of the above-mentioned test devices for the voltage source operation capability of the wind turbine.

[0074] Specifically, step 1 includes:

[0075] determining the rated voltage V of the system to which the test device is connected n and the rated power P of the wind turbine to be tested n According to the weak grid operation capability test requirement, determine the short-circuit ratio value SCR1-SCR4 required for the wind turbine to be tested, wherein SCR1<SCR2<SCR3<SCR4. The recommended values are SCR1=1.05, SCR2=1.33, SCR3=2.67, and SCR4=4.00.

[0076] According to the determined value of SCR1, determine the value of line impedance X1

[0077]

[0078] According to the determined values of SCR1 and SCR2, determine the value of line impedance X2

[0079]

[0080] According to the determined values of SCR2 and SCR3, determine the value of line impedance X3

[0081]

[0082] According to the determined values of SCR3 and SCR4, determine the value of line impedance X4

[0083]

[0084] Step 2 includes:

[0085] When the weak grid adaptability test is performed, the grid-connected breaker CB1 is kept in a closed state, the load breaker CB3 is kept in an open state, and the active power output of the wind turbine under test should be the rated power during the test except for starting the grid-connected process. The test is performed by using the following specific steps.

[0086] In the initial state, the bypass switch CB2 is in a closed state, the line impedance switches S1-S4 are in a closed state, and the wind turbine under test is directly grid-connected through the bypass switch CB2 and the grid-connected breaker CB1.

[0087] The wind turbine under test is started to normally grid-connect and operate.

[0088] When the wind turbine under test is in a rated operating state, the bypass switch CB2 is opened, the wind turbine under test is grid-connected through the parallel-connected line impedances X1-X4, and is kept in this state for a duration of not less than 60 minutes. During the test, if the wind turbine under test is off-grid, the test duration and the off-grid time of the wind turbine are recorded.

[0089] If the wind turbine under test is kept in normal operation in the above step, the line impedance switch S4 is opened, the wind turbine under test is grid-connected through the parallel-connected line impedances X1-X3, and is kept in this state for a duration of not less than 60 minutes. During the test, if the wind turbine under test is off-grid, the test duration and the off-grid time of the wind turbine are recorded.

[0090] Referring to the above step, the line impedance switches S3 and S2 are sequentially opened, the wind turbine under test is grid-connected through the corresponding line impedances, and is kept in the corresponding state for a duration of not less than 60 minutes, respectively. During the test, if the wind turbine under test is off-grid, the test duration and the off-grid time of the wind turbine are recorded.

[0091] If the wind turbine under test is kept in normal operation in the above step, the wind turbine is stopped, the state of the test device is kept unchanged, the wind turbine under test is restarted, is grid-connected through the line impedance X1, reaches the rated operating state, and continuously operates for not less than 10 minutes. During the test, if the wind turbine under test is off-grid, the test duration and the off-grid time of the wind turbine are recorded.

[0092] If the wind turbine under test passes each item in the above steps, it is considered to pass the weak grid adaptability test, otherwise, it is considered to fail the test.

[0093] Step 3 includes:

[0094] When the off-grid operation test is performed, the bypass switch CB2 is kept in the closed state, the line impedance switches S1-S4 are in the open state, and the active power output of the wind turbine under test should be above 80% of the rated power during the test except for the grid-connected process. The test is performed by using the following specific steps.

[0095] In the initial state, the grid-connected breaker CB1 is in the closed state, the load breaker CB3 is in the open state, and the load simulation system is in the standby state. The reference structure of the load simulation system is shown in Figure 4 .

[0096] The load breaker CB3 is closed, and the load simulation system is started and adjusted so that the current flowing through the grid-connected breaker CB1 is less than 1% of the rated current of the wind turbine under test.

[0097] After the system is stabilized, the grid-connected breaker CB1 is opened. If the wind turbine under test keeps running, the time interval from the time when the grid-connected breaker CB1 is opened to the time when the output current of the wind turbine reaches 90% of the rated current is measured. If the wind turbine under test is disconnected from the grid, the test duration and the disconnection time of the wind turbine are recorded.

[0098] The running duration of the wind turbine is kept for not less than 60 minutes. During the test, if the wind turbine under test is disconnected from the grid, the test duration and the disconnection time of the wind turbine are recorded. During this process, the output voltage, phase deviation, frequency deviation, total harmonic distortion rate of the output voltage, unbalance degree of the output voltage, and voltage fluctuation of the wind turbine are collected and measured.

[0099] If the wind turbine under test passes each item in the above steps, it is considered to pass the off-grid operation capability test, otherwise it is considered to fail the test.

[0100] Step 4 includes:

[0101] When the black start capability test is performed, the grid-connected breaker CB1 is kept in the open state, the bypass switch CB2 is kept in the closed state, and the line impedance switches S1-S4 are in the open state. The test is performed by using the following specific steps.

[0102] In the initial state, the load breaker CB3 is in the open state, and the load simulation system sets the initial active load P L0 and the initial reactive load Q L0 according to the black start requirements of the wind turbine under test.

[0103] The black start instruction is issued to the wind turbine under test, and the load breaker CB3 is closed so that the wind turbine under test starts running with the load.

[0104] After the system is stable, the setting value of the load simulation device is gradually adjusted so that the wind turbine to be tested reaches the rated operating state, and the load simulation system is powered in isolation, and the duration of the state is maintained for no less than 60 minutes. During the test, if the wind turbine to be tested is disconnected from the grid, the test duration and the time of disconnection of the wind turbine from the grid are recorded.

[0105] If the wind turbine to be tested passes each item in the above steps, it is considered to pass the black start capability test, otherwise, it is considered to fail the black start capability test.

[0106] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit the scope of protection, although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that: after reading the present application, those skilled in the art can still make various changes, modifications or equivalent replacements to the specific embodiments of the application, but these changes, modifications or equivalent replacements are all within the scope of protection of the claims to be approved.

Claims

1. A test method for the voltage source operating capability of wind turbine generators, characterized in that, include: Based on the rated voltage and rated power of the wind turbine under test, and combined with the formula for calculating the grid short-circuit ratio, the grid short-circuit ratio to be tested for the wind turbine is set. Based on the grid short-circuit ratio and the formula for calculating line impedance, the line impedance value to be simulated in the line impedance simulation part of the test device is calculated. By simulating the line impedance value in the grid-connected switch and the test device, the weak grid adaptability of the wind turbine voltage source operation capability is tested. By simulating different load types through the load simulation part of the grid-connected switch and the testing device, the off-grid operation capability of the wind turbine voltage source operation capability is tested. By simulating different load types using the load simulation section of the testing device, the black start capability of the wind turbine voltage source operation capability is tested. The testing device includes: Grid-connected switch, line impedance simulation, and load simulation; The line impedance simulation is connected in series with the grid-connected switch to form a branch. The branch is connected in series between the high-voltage side of the transformer substation of the wind turbine under test and the grid connection point. It is used to simulate different line impedance values ​​and test the weak grid adaptability of the wind turbine's voltage source operation capability. The load simulation is connected in parallel to the high-voltage side of the transformer substation of the wind turbine under test to simulate different load types and test the off-grid operation capability and black start capability of the wind turbine voltage source operation capability. The wind turbine voltage source operating capability includes weak grid adaptability, off-grid operation capability and black start capability, and the different load types include one or more of the following: constant power load, constant current load and constant impedance load. The line impedance simulation includes: Multiple line impedance inductors, multiple line impedance switches, and bypass switches; The multiple line impedance inductors are connected in series with the corresponding line impedance switches to form multiple branches, and the multiple branches are connected in parallel with the bypass switch; The number of line impedance inductors is the same as the number of line impedance switches. The load simulation includes: Load circuit breakers, load transformers, and load simulation systems; One end of the load circuit breaker is connected to the high-voltage side of the transformer box of the wind turbine under test, and the other end is connected in series with the load transformer and the load simulation system.

2. The method as described in claim 1, characterized in that, The line impedance inductance calculation formula includes a first line impedance inductance calculation formula and other line impedance inductance calculation formulas connected in parallel with the line impedance inductance; wherein, the first line impedance inductance calculation formula is shown below: Where m = 1, SCRm is the first grid short-circuit ratio to be tested for the wind turbine, Xm is the first line impedance inductance, and V n P is the rated voltage of the system to which it is connected. n The rated power of the wind turbine unit under test; The calculation formulas for other line impedance inductances connected in parallel with the aforementioned line impedance inductance are shown below: Where SCRm+1 is the (m+1)th grid short-circuit ratio to be tested for the wind turbine, SCRm is the grid short-circuit ratio adjacent to SCRm+1, Xm+1 is the (m+1)th line impedance inductance, and V... n P is the rated voltage of the system to which it is connected. n The rated power of the wind turbine being tested.

3. The method as described in claim 1, characterized in that, The method involves simulating line impedance values ​​using the line impedance simulation section of the grid-connected switch and testing device to test the weak grid adaptability of the wind turbine's voltage source operation capability, including: Close the grid connection switch and bypass switch to directly connect the wind turbine under test to the grid. When the wind turbine under test is in rated operating condition, close all line impedance switches and open the bypass switch. Maintain this for the first set time to determine whether the wind turbine under test is disconnected from the grid. If the wind turbine under test is disconnected from the grid, record the test duration and the time the unit is disconnected from the grid; otherwise, disconnect one parallel line impedance switch in sequence each time, so that the wind turbine under test is connected to the grid through the remaining parallel line impedance inductor each time, and maintain the first set time to determine whether the wind turbine under test is disconnected from the grid. If the wind turbine under test is disconnected from the grid, record the test duration and the time the unit is disconnected from the grid; otherwise, stop the wind turbine from running, keep the test device in the same state, restart the wind turbine under test, make the wind turbine under test connect to the grid through the first line impedance, reach the rated operating state and run continuously for no less than the second set time, and determine whether the wind turbine under test is disconnected from the grid. If the wind turbine under test is disconnected from the grid, the test duration and the disconnection time are recorded; otherwise, it is considered to have passed the weak grid adaptability test.

4. The method as described in claim 1, characterized in that, The method involves simulating different load types through the load simulation section of the grid-connected switch and testing device to test the off-grid operation capability of the wind turbine voltage source, including: During the S1 test, except for the start-up and grid connection process, the active power output of the wind turbine under test should be greater than the rated power of the set ratio. Close the grid connection switch, bypass switch and load circuit breaker, and adjust the load simulation system so that the current flowing through the grid connection switch is less than the first set ratio of the rated current of the wind turbine under test. After the system stabilizes, disconnect the grid connection switch. If the wind turbine under test continues to run, measure the time interval from the moment the grid connection switch is disconnected until the wind turbine output current reaches the second set ratio of the rated current and proceed to step S3; otherwise, proceed to step S5. S3 If the wind turbine continues to operate, the wind turbine will continue to operate for a duration of not less than the first set duration. The wind turbine's operating data will be collected and measured, and the process will proceed to step S4. Otherwise, the process will proceed to step S5. S4 passed the off-network operation capability test; S5 records the test duration and the unit's offline time; The operating data includes: output voltage, phase deviation, frequency deviation, total harmonic distortion of output voltage, output voltage unbalance, and output voltage fluctuation, wherein the first set ratio is less than the second set ratio.

5. The method as described in claim 1, characterized in that, The test device uses a load simulation section to simulate different load types and tests the black start capability of the wind turbine's voltage source operation, including: The initial active and reactive loads of the load simulation system are set according to the black start requirements of the wind turbine under test. Disconnect the grid connection switch and close the load circuit breaker to start the wind turbine under test with the load. After the system stabilizes, adjust the load simulation device to bring the wind turbine under test to the rated operating state and maintain the operation time for no less than the first set duration. If the wind turbine under test goes offline, record the test duration and the time the unit goes offline. Otherwise, pass the black start capability test.

6. The method as described in claim 1, characterized in that, The grid-connected switch includes a grid-connected circuit breaker.

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