A testing method and system for the weak grid adaptability of a wind turbine generator set

Abstract

The present invention provides a method and system for testing the weak grid adaptability of a wind turbine generator set, including: collecting the current of the wind turbine generator set to be tested by using a grid simulation device connected in series between the high-voltage side of the transformer of the wind turbine generator set to be tested and the grid; setting different equivalent short-circuit ratios required for the test, obtaining the rated power and rated voltage of the wind turbine generator set to be tested, and combining with the equivalent short-circuit ratio calculation formula to obtain the impedance values corresponding to different equivalent short-circuit ratios required for the test; based on the impedance values corresponding to different short-circuit ratios, the current of the wind turbine generator set to be tested and the rated voltage of the wind turbine generator set to be tested, and combining with the reference voltage command calculation formula, obtaining the reference voltage commands corresponding to different impedance values; based on the reference voltage commands corresponding to different impedance values, using the grid simulation device to simulate different weak grid characteristics to test the weak grid adaptability of the wind turbine generator set; the present invention provides experimental verification conditions for the operating characteristics of the wind turbine in a weak grid environment by dynamically adjusting the impedance value and simulating different weak grid characteristics.

Description

Technical Field

[0001] The present invention belongs to the field of new energy access, and particularly relates to a method and system for testing the weak grid adaptability of a wind turbine generator set. Background Art

[0002] With the large-scale access of wind power to the power grid, the power grid is changing from a strong grid that can neglect the internal impedance to a weak grid that needs to consider the internal impedance. The risk of system disturbance increases. New energy represented by wind power should have good weak grid adaptability to ensure the safe and stable operation of the power system. Regarding the weak grid adaptability problem of wind turbine generator sets, relevant research has been carried out in the academic community, and methods such as voltage source type control of wind turbine generator sets and coordinated operation of wind power and energy storage have been proposed. However, due to the lack of relevant detection methods, the operating characteristics in the actual weak grid environment cannot be experimentally verified, which restricts the progress of wind power grid connection technology. Summary of the Invention

[0003] To overcome the deficiencies of the above-mentioned prior art, the present invention proposes a method for testing the weak grid adaptability of a wind turbine generator set, including: collecting the current of the unit under test by using a grid simulation device connected in series between the high-voltage side of the transformer of the wind turbine generator set under test and the power grid;

[0004] Setting different equivalent short-circuit ratios required for the test, obtaining the rated power and rated voltage of the unit under test, and combining with the equivalent short-circuit ratio calculation formula to obtain the impedance values corresponding to different equivalent short-circuit ratios required for the test;

[0005] Based on the impedance values corresponding to the different short-circuit ratios, the current of the unit under test and the rated voltage of the unit under test, and combining with the reference voltage command calculation formula, obtain the reference voltage commands corresponding to different impedance values;

[0006] Based on the reference voltage commands corresponding to the different impedance values, use the grid simulation device to simulate different weak grid characteristics and test the weak grid adaptability of the wind turbine generator set.

[0007] Preferably, the setting of different equivalent short-circuit ratios required for the test includes:

[0008] Taking the set first equivalent short-circuit ratio as the demarcation point, dividing the power grid into a strong grid interval and a weak grid interval, and taking the demarcation point, the equivalent short-circuit ratios before and after the demarcation point as the test points.

[0009] Preferably, the testing of the weak grid adaptability of the wind turbine generator set under test by using the grid simulation device to simulate different weak grid characteristics based on the reference voltage commands corresponding to the different impedance values includes:

[0010] Input the reference voltage commands corresponding to the different impedance values into the power grid simulation device respectively. Based on the output method of the reference voltage, the power grid simulation device controls and outputs the corresponding reference voltage to simulate the weak power grid characteristics under the impedance value corresponding to the reference voltage command;

[0011] Adjust the number of reference voltage commands used in a test to conduct a single impedance change test or a continuous impedance change test on the wind turbine.

[0012] Preferably, the output method of the reference voltage, where the power grid simulation device controls and outputs the corresponding reference voltage, includes:

[0013] Collect the actual output voltage and current of the power grid simulation device, and obtain the positive and negative sequence dq components of the actual output voltage and current through the dq transformation and the positive and negative sequence component extraction algorithm;

[0014] Based on the dq transformation and the positive and negative sequence component extraction algorithm, calculate the reference voltage commands corresponding to the different impedance values to obtain the positive and negative sequence dq components of the reference voltage;

[0015] Subtract the positive sequence dq voltage component of the actual output voltage from the corresponding positive sequence dq voltage component of the reference voltage respectively to obtain the first voltage difference, use the first voltage difference as the object of PI control, and obtain the positive sequence dq components of the reference current through PI control;

[0016] Subtract the positive sequence dq components of the reference current from the corresponding positive sequence dq components of the actual current respectively to obtain the first current difference, use the first current difference as the object of PI control, and through PI control and dq-abc transformation, obtain the three-phase positive sequence target voltage and the three-phase negative sequence target voltage. Add the three-phase positive sequence target voltage and the three-phase negative sequence target voltage to obtain the total target voltage, and through the modulation wave generation algorithm and PWM modulation, obtain the converter switch control signal to control the output reference voltage through the converter switch control signal.

[0017] Preferably, the adjustment of the number of reference voltage commands used in a test to conduct a single impedance change test or a continuous impedance change test on the wind turbine includes:

[0018] When the number of reference voltage commands used in each test is adjusted to 1, conduct a single impedance change test on the weak power grid of the wind turbine;

[0019] When the number of reference voltage commands used in each test is adjusted to be greater than 1, conduct a continuous impedance change test on the weak power grid of the wind turbine.

[0020] Preferably, the single impedance change test on the wind turbine includes:

[0021] Based on the control differences of the wind turbine generator set in different power intervals, the wind turbine generator set is respectively operated in the high-power interval and the low-power interval, and each time only the reference voltage command corresponding to one impedance value is selected. The wind turbine generator set is started and maintained in operation for the first set duration, and the operation data and status of the wind turbine generator set are recorded. Then, the remaining reference voltage commands are used for testing in turn;

[0022] Test the adaptability of the wind turbine generator set based on the operation data and status of the wind turbine generator set;

[0023] Among them, the high-power interval is the rated power interval of the wind turbine generator set greater than the first set ratio, the low-power interval is the rated power interval of the wind turbine generator set greater than the third set ratio and less than the second set ratio, the first set ratio is greater than the second set ratio, and the second set ratio is greater than the third set ratio.

[0024] Preferably, the impedance continuous change test for the weak grid of the wind turbine generator set includes:

[0025] Based on the control differences of the wind turbine generator set in different power intervals, the wind turbine generator set is respectively operated in the high-power interval and the low-power interval. Each time, multiple reference voltage commands corresponding to impedance values are selected, and one of them is selected. After the wind turbine generator set is started and maintained in operation for the second set duration, the remaining reference voltage commands are replaced. After each replacement of the reference voltage command, the operation is continued for the same time, and the operation data and status of the wind turbine generator set are recorded;

[0026] Test the adaptability of the wind turbine generator set based on the operation data and status of the wind turbine generator set;

[0027] Among them, the high-power interval is the rated power interval of the wind turbine generator set greater than the first set ratio, the low-power interval is the rated power interval of the wind turbine generator set greater than the third set ratio and less than the second set ratio, the first set ratio is greater than the second set ratio, and the second set ratio is greater than the third set ratio.

[0028] Preferably, the testing of the adaptability of the wind turbine generator set based on the operation data and status of the wind turbine generator set includes:

[0029] If the status of the wind turbine generator set is off-grid, the wind turbine generator set does not have adaptability at the impedance value and power value corresponding to the reference voltage command in the test, otherwise it has adaptability at the impedance value and power value corresponding to the reference voltage command in the test.

[0030] Preferably, the impedance value is calculated according to the following formula:

[0031]

[0032] In the formula, U nis the rated voltage at the grid connection point of the wind turbine, P n is the rated power of the wind turbine, and SCR is the set equivalent short-circuit ratio.

[0033] Preferably, the reference voltage command calculation formula is as shown in the following formula:

[0034] U ref = U n + Z o I o

[0035] In the formula, U n is the rated voltage at the grid connection point of the wind turbine, Z o is the impedance value, and I o is the output current on the output side of the power grid simulation device.

[0036] Based on the same inventive concept, the present invention also provides a wind turbine weak grid adaptability test system, which is characterized by including:

[0037] an impedance value acquisition module, a reference voltage command calculation module, and a weak grid adaptability test module;

[0038] The impedance value acquisition module is used to obtain the impedance values corresponding to different equivalent short-circuit ratios required for testing according to the different equivalent short-circuit ratios required for the set test, the rated power and rated voltage of the unit under test, and in combination with the equivalent short-circuit ratio calculation formula;

[0039] The reference voltage command calculation module is used to obtain the reference voltage commands corresponding to different impedance values based on the impedance values corresponding to the different short-circuit ratios, the current of the unit under test, and the rated voltage of the unit under test, in combination with the reference voltage command calculation formula;

[0040] The weak grid adaptability test module is used to test the weak grid adaptability of the wind turbine by using the power grid simulation device to simulate different weak grid characteristics based on the reference voltage commands corresponding to the different impedance values.

[0041] Preferably, the weak grid adaptability test module includes:

[0042] a data input sub-module, which is used to input the reference voltage commands corresponding to the different impedance values into the power grid simulation device respectively, and the power grid simulation device simulates the grid characteristics corresponding to the impedance values of the reference voltage commands;

[0043] a test sub-module, which is used to adjust the number of reference voltage commands used in a test to perform a single impedance change test or a continuous impedance change test on the wind turbine.

[0044] Compared with the closest prior art, the beneficial effects of the present invention are as follows:

[0045] The present invention provides a method and system for testing the weak grid adaptability of a wind turbine generator set, including: collecting the current of the wind turbine generator set to be tested by using a grid simulation device connected in series between the high-voltage side of the transformer of the wind turbine generator set to be tested and the grid; setting different equivalent short-circuit ratios required for the test, obtaining the rated power and rated voltage of the wind turbine generator set to be tested, and combining with the equivalent short-circuit ratio calculation formula to obtain the impedance values corresponding to different equivalent short-circuit ratios required for the test; based on the impedance values corresponding to the different short-circuit ratios, the current of the wind turbine generator set to be tested and the rated voltage of the wind turbine generator set to be tested, and combining with the reference voltage command calculation formula, obtaining the reference voltage commands corresponding to different impedance values; based on the reference voltage commands corresponding to the different impedance values, using the grid simulation device to simulate different weak grid characteristics and testing the weak grid adaptability of the wind turbine generator set; the present invention proposes a grid disturbance simulation device with dynamic impedance simulation ability, dynamically adjusting the impedance setting value through the reference voltage command to simulate different weak grid characteristics, providing a test environment for the wind turbine generator set; solving the problem that the operating characteristics of the wind turbine generator set in a weak grid environment cannot be experimentally verified, providing an important means for testing the weak grid adaptability of the wind turbine generator set, and laying a foundation for the effective verification of the weak grid operation control technology of the wind turbine generator set and the safe and stable operation of the wind power system. Description of the Drawings

[0046] Figure 1 It is a schematic flow chart of a method for testing the weak grid adaptability of a wind turbine generator set provided by the present invention;

[0047] Figure 2 It is a schematic diagram of the principle for testing the weak grid adaptability of a wind turbine generator set provided by the present invention;

[0048] Figure 3 It is an equivalent diagram for testing the weak grid adaptability of a wind turbine generator set provided by the present invention;

[0049] Figure 4 It is a schematic diagram of the control principle of the grid simulation device provided by the present invention;

[0050] Figure 5 It is a schematic diagram of the structure of a system for testing the weak grid adaptability of a wind turbine generator set provided by the present invention. Detailed Embodiments

[0051] The following further elaborates in detail on the specific embodiments of the present invention in conjunction with the drawings.

[0052] Embodiment 1:

[0053] A schematic flow chart of a method for testing the weak grid adaptability of a wind turbine generator set provided by the present invention is as Figure 1 shown, including:

[0054] Step 1: Collect the current of the wind turbine to be tested by using a grid simulation device connected in series between the high-voltage side of the transformer of the wind turbine to be tested and the grid.

[0055] Step 2: Set different equivalent short-circuit ratios required for the test, the rated power and rated voltage of the wind turbine to be tested, and combine the equivalent short-circuit ratio calculation formula to obtain the impedance values corresponding to different equivalent short-circuit ratios required for the test.

[0056] Step 3: Based on the impedance values corresponding to the different short-circuit ratios, the current of the wind turbine to be tested, and the rated voltage of the wind turbine to be tested, combine the reference voltage command calculation formula to obtain the reference voltage commands corresponding to different impedance values.

[0057] Step 4: Based on the reference voltage commands corresponding to the different impedance values, use the grid simulation device to simulate different weak grid characteristics and test the weak grid adaptability of the wind turbine.

[0058] Specifically, Step 1 includes:

[0059] During the test, connect the grid simulation device in series between the high-voltage side of the transformer of the wind turbine and the grid. As shown in the appendix, the grid simulation device collects the output voltage U Figure 2 and current I o at the output side (generator transformer side) of the grid simulation device. o .

[0060] Step 2 includes:

[0061] Taking the division of strong and weak grids with SCR = 3 as the boundary as an example, respectively take the weak grid intervals SCR = 1, 2 and the strong grid intervals SCR = 5, 10, and add the boundary point (SCR = 3) as the test point. The equivalent short-circuit ratio can be expressed as:

[0062]

[0063] In the formula, P n is the rated power of the wind turbine;

[0064] Correspondingly, the impedance value can be obtained as

[0065] Step 3 includes:

[0066] Calculate the reference voltage command of the grid simulation device according to the set impedance value Z o , and the calculation method is as follows:

[0067] U ref = U n + Z o I o

[0068] In the formula, U nis the rated voltage at the grid connection point of the wind turbine generator set.

[0069] According to the calculation formula, an equivalent diagram for testing the weak grid adaptability of the wind turbine generator set can be obtained. The equivalent diagram is as shown in Figure 3 .

[0070] Step 4 includes:

[0071] Input the reference voltage commands corresponding to the different impedance values into the grid simulation device respectively. Based on the output method of the reference voltage, the grid simulation device controls and outputs the corresponding reference voltage to simulate the characteristics of the weak grid under the impedance values corresponding to the reference voltage commands;

[0072] Considering the control differences of the wind turbine generator set in different power intervals, the adaptability of the unit is tested respectively in the high-power interval (P > 0.8P n ) and the low-power interval (0.2P n ≤ P ≤ 0.5P n ).

[0073] When the wind turbine generator set is operating normally, the weak grid adaptability of the unit is tested respectively in the high-power interval (P > 0.8P n ) and the low-power interval (0.2P n ≤ P ≤ 0.5P n ). The following steps are adopted during the test:

[0074] Single impedance change test

[0075] ① According to Figure 2 , connect the grid simulation device. The control schematic diagram of the grid simulation device is as shown in Figure 4 .

[0076] ② Set the impedance value of the grid simulation device to Z5, start the wind turbine generator set, keep it running for 10 minutes, and record the operation data and status of the wind turbine generator set;

[0077] ③ Refer to step ② and set the impedance values to Z4, Z3, Z2, and Z1 respectively, and record the operation data and status of the wind turbine generator set.

[0078] Continuous impedance change test

[0079] ① According to Figure 2 , connect the grid simulation device;

[0080] ② Set the impedance value of the grid simulation device to Z5, start the wind turbine generator set, keep it running for 5 minutes, then set the impedance value to Z1, and keep it running for 5 minutes, and record the operation data and status of the wind turbine generator set;

[0081] ③ Refer to step ② and set the impedance values according to the pre-set continuous impedance change test content, and record the operation data and status of the wind turbine generator set.

[0082] Test result determination: If the wind turbine is disconnected from the grid during the test, it is regarded as failed.

[0083] Embodiment 2:

[0084] Based on the same inventive concept, the present invention provides a test system for the weak grid adaptability of a wind turbine;

[0085] The structure of the system is as Figure 5 shown, and includes:

[0086] An impedance value acquisition module, a reference voltage command calculation module, and a weak grid adaptability test module;

[0087] The impedance value acquisition module is used to obtain the impedance values corresponding to different equivalent short-circuit ratios required for the test according to the different equivalent short-circuit ratios required for the set test, the rated power and rated voltage of the unit under test, and in combination with the equivalent short-circuit ratio calculation formula;

[0088] The reference voltage command calculation module is used to obtain the reference voltage commands corresponding to different impedance values based on the impedance values corresponding to the different short-circuit ratios, the current of the unit under test, and the rated voltage of the unit under test, in combination with the reference voltage command calculation formula;

[0089] The weak grid adaptability test module is used to test the weak grid adaptability of the wind turbine under test by using the grid simulation device to simulate different weak grid characteristics based on the reference voltage commands corresponding to the different impedance values.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the scope of its protection. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: After reading the present invention, those skilled in the art can still make various changes, modifications, or equivalent replacements to the specific implementation manners of the application, but these changes, modifications, or equivalent replacements are all within the scope of the protection of the claims pending for approval of the application.

Claims

1. A test method for the weak grid adaptability of a wind turbine, characterized in that, Including: Collecting the current of the to-be-tested wind turbine unit by using a grid simulation device connected in series between the high-voltage side of the transformer of the to-be-tested wind turbine unit and the grid; Setting different equivalent short-circuit ratios required for the test, obtaining the rated power and rated voltage of the to-be-tested unit, and combining with the equivalent short-circuit ratio calculation formula to obtain the impedance values corresponding to different equivalent short-circuit ratios required for the test; Based on the impedance values corresponding to the different equivalent short-circuit ratios, the current of the to-be-tested unit and the rated voltage of the to-be-tested unit, and combining with the reference voltage command calculation formula, obtaining the reference voltage commands corresponding to different impedance values; Based on the reference voltage commands corresponding to the different impedance values, using the grid simulation device to simulate different weak grid characteristics and testing the weak grid adaptability of the wind turbine unit; The testing the weak grid adaptability of the to-be-tested wind turbine unit by using the grid simulation device to simulate different weak grid characteristics based on the reference voltage commands corresponding to the different impedance values includes: Respectively inputting the reference voltage commands corresponding to the different impedance values into the grid simulation device, and based on the output method of the reference voltage, controlling and outputting the corresponding reference voltage by the grid simulation device to simulate the weak grid characteristics under the impedance value corresponding to the reference voltage command; Adjusting the number of reference voltage commands used in a test to perform a single impedance change test or a continuous impedance change test on the wind turbine unit.

2. The method according to claim 1, characterized in that, The setting different equivalent short-circuit ratios required for the test includes: Taking the set first equivalent short-circuit ratio as the demarcation point, dividing the grid into a strong grid interval and a weak grid interval, and taking the demarcation point, the equivalent short-circuit ratios before and after the demarcation point as the test points.

3. The method according to claim 1, characterized in that, The controlling and outputting the corresponding reference voltage by the grid simulation device based on the output method of the reference voltage includes: Collecting the actual output voltage and current of the grid simulation device, and obtaining the positive and negative sequence dq components of the actual output voltage and current through dq transformation and positive and negative sequence component extraction algorithm; Based on the dq transformation and positive and negative sequence component extraction algorithm, calculating the reference voltage commands corresponding to the different impedance values to obtain the positive and negative sequence dq components of the reference voltage; Subtracting the positive sequence dq voltage component of the actual output voltage from the corresponding positive sequence dq voltage component of the reference voltage respectively to obtain a first voltage difference, taking the first voltage difference as the object of PI control, and obtaining the positive sequence dq component of the reference current through PI control; Subtracting the positive sequence dq component of the reference current from the corresponding positive sequence dq component of the actual current respectively to obtain a first current difference, taking the first current difference as the object of PI control, and through PI control and dq-abc transformation, obtaining the three-phase positive sequence target voltage and the three-phase negative sequence target voltage, adding the three-phase positive sequence target voltage and the three-phase negative sequence target voltage to obtain the total target voltage, and obtaining the converter switch control signal through the modulation wave generation algorithm and PWM modulation, and controlling the output reference voltage through the converter switch control signal.

4. The method according to claim 1, characterized in that, The adjusting the number of reference voltage commands used in a test to perform a single impedance change test or a continuous impedance change test on the wind turbine unit includes: When the number of reference voltage commands used in each test is adjusted to 1, a single impedance change test is performed on the weak grid of the wind turbine generator set; When the number of reference voltage commands used in each test is adjusted to be greater than 1, a continuous impedance change test is performed on the weak grid of the wind turbine generator set.

5. The method according to claim 4, wherein The single impedance change test performed on the wind turbine generator set includes: Based on the control differences of the wind turbine generator set in different power ranges, the wind turbine generator set is respectively operated in the high-power range and the low-power range of the wind turbine generator set, and each time only a reference voltage command corresponding to one impedance value is selected. The wind turbine generator set is started and maintained for the first set duration, and the operation data and status of the wind turbine generator set are recorded. Then, the remaining reference voltage commands are used for testing in turn; Based on the operation data and status of the wind turbine generator set, the adaptability of the wind turbine generator set is tested; Among them, the high-power range is the rated power range of the wind turbine generator set greater than the first set ratio, the low-power range is the rated power range of the wind turbine generator set greater than the third set ratio and less than the second set ratio, the first set ratio is greater than the second set ratio, and the second set ratio is greater than the third set ratio.

6. The method according to claim 4, wherein The continuous impedance change test performed on the weak grid of the wind turbine generator set includes: Based on the control differences of the wind turbine generator set in different power ranges, the wind turbine generator set is respectively operated in the high-power range and the low-power range of the wind turbine generator set. Each time, multiple reference voltage commands corresponding to impedance values are selected, and one of them is selected. The wind turbine generator set is started and maintained for the second set duration, and then the remaining reference voltage commands are replaced. After each replacement of the reference voltage command, it continues to run for the same time, and the operation data and status of the wind turbine generator set are recorded; Based on the operation data and status of the wind turbine generator set, the adaptability of the wind turbine generator set is tested; Among them, the high-power range is the rated power range of the wind turbine generator set greater than the first set ratio, the low-power range is the rated power range of the wind turbine generator set greater than the third set ratio and less than the second set ratio, the first set ratio is greater than the second set ratio, and the second set ratio is greater than the third set ratio.

7. The method according to claim 5 or 6, characterized in that, The testing of the adaptability of the wind turbine generator set based on the operation data and status of the wind turbine generator set includes: If the state of the wind turbine generator set is off-grid, the impedance value corresponding to the reference voltage command in the test and the power value do not have adaptability, otherwise, they have adaptability at the impedance value corresponding to the reference voltage command in the test and the power value.

8. The method according to claim 1, wherein The impedance value is calculated according to the following formula: Where U n is the rated voltage of the wind turbine grid connection point, P n is the rated power of the wind turbine, and SCR is the set equivalent short-circuit ratio.

9. The method according to claim 1, characterized in that, The calculation formula of the reference voltage command is as shown in the following formula: U ref = U n + Z o I o Where, U n is the rated voltage at the grid connection point of the wind turbine, Z o is the impedance value, and I o is the output current on the output side of the power grid simulation device.

10. A test system for the weak grid adaptability of a wind turbine generator set, characterized in that, It includes: An impedance value acquisition module, a reference voltage command calculation module, and a weak grid adaptability test module; The impedance value acquisition module is used to obtain the impedance values corresponding to different equivalent short-circuit ratios required for the test according to the different equivalent short-circuit ratios required for the set test, the rated power and rated voltage of the unit under test, and in combination with the equivalent short-circuit ratio calculation formula; The reference voltage command calculation module is used to obtain the reference voltage commands corresponding to different impedance values based on the impedance values corresponding to the different equivalent short-circuit ratios, the current of the unit under test, and the rated voltage of the unit under test, and in combination with the reference voltage command calculation formula; The weak grid adaptability test module is used to simulate different weak grid characteristics by using a grid simulation device based on the reference voltage commands corresponding to different impedance values, and test the weak grid adaptability of the wind turbine generator set; The weak grid adaptability test module includes: A data input sub-module, which is used to input the reference voltage commands corresponding to different impedance values into the grid simulation device respectively, and the grid simulation device simulates the grid characteristics corresponding to the impedance values of the reference voltage commands; A test sub-module, which is used to adjust the number of reference voltage commands used in a test, and perform a single impedance change test or a continuous impedance change test on the wind turbine generator set.

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