Wind power converter reactive capability test system and control method thereof

Abstract

The invention discloses a wind power converter reactive capability test system and a control method thereof. The system comprises a wind power converter, a test platform and a control unit. The test platform comprises a first transformer, a second transformer, a self-aging switch and a filtering unit. The alternating current side of the grid-side converter is connected with one end of the first transformer and one end of the second transformer, the direct current side of the grid-side converter is connected with the direct current side of the machine-side converter through the bus capacitor, and the alternating current side of the machine-side converter is connected with the other end of the second transformer through the filtering unit and the self-aging switch. The other end of the first transformer is connected with a power grid; the control unit is configured to obtain a reactive power instruction issued by the upper computer; and controlling the machine-side converter and the grid-side converter to perform reactive power cancellation based on the reactive power instruction. According to the application, the requirement on test equipment is reduced, the reactive power output capability of the wind power converter can be tested by only one wind power converter, and the reactive power supporting capability of the converter is verified.

Description

Technical Field

[0001] The present application relates to the field of wind power technology, and in particular to a wind power converter power failure test system and a control method thereof. Background Art

[0002] As a large number of power electronic devices are connected to the power grid, the adaptability of the power grid has deteriorated, which in turn puts forward more requirements for the performance of new energy equipment, one of which is that new energy equipment needs to have reactive power support capabilities. Through the designed wind power converter reactive power test method and test platform, the reactive output capacity of the wind power converter can be tested to verify the reactive power support capacity of the converter, ensure that the wind turbine can operate stably under specific working conditions, and improve the adaptability of the power grid.

[0003] At present, the wind power converter has no functional capacity verification, which requires two converters to be tested side by side. However, this test method has high requirements on the test equipment and cannot fully test the capacity of wind turbine modules. Summary of the invention

[0004] In view of this, the purpose of the present application is to provide a wind power converter reactive power test system and control method thereof, so as to reduce the requirements for test equipment, test the reactive power output capacity of the wind power converter, and verify the reactive power support capacity of the converter.

[0005] The technical solutions adopted by this application to solve the above technical problems are as follows:

[0006] On one hand, the present application provides a wind power converter non-functional capacity test system, including a wind power converter, a test platform and a control unit;

[0007] The wind power converter includes a machine-side converter, a bus capacitor and a grid-side converter, and the test platform includes a first transformer, a second transformer, a self-aging switch and a filter unit;

[0008] The AC side of the grid-side converter is connected to one end of the first transformer and one end of the second transformer, the DC side of the grid-side converter is connected to the DC side of the machine-side converter through a bus capacitor, the AC side of the machine-side converter is connected to the other end of the second transformer through a filter unit and a self-aging switch, and the other end of the first transformer is connected to the grid;

[0009] The control unit is configured to obtain a reactive power instruction issued by a host computer; based on the reactive power instruction, the control unit controls the machine-side converter and the grid-side converter to perform reactive power cancellation.

[0010] In one example, the control unit is configured to control the grid-side converter to output inductive reactive power and control the generator-side converter to output corresponding capacitive reactive power based on the reactive power instruction.

[0011] In one example, the control unit is configured to control the grid-side converter to output capacitive reactive power and control the generator-side converter to output corresponding inductive reactive power based on the reactive power instruction.

[0012] In one example, the control unit is configured to determine a q-axis current set value of the grid-side converter; based on the q-axis current set value, convert the d-axis current of the machine-side converter; and control the machine-side converter to output a corresponding reactive power according to the d-axis current of the machine-side converter.

[0013] In an example, the control unit is configured to determine a q-axis current set value of the grid-side converter according to a reactive power set value of the grid-side converter and an effective value of an AC side voltage of the grid-side converter.

[0014] In one example, the control unit is configured to invert the given value of the q-axis current, and then convert the d-axis current of the machine-side converter according to the effective value of the AC side voltage of the grid-side converter and the effective value of the AC side voltage of the machine-side converter.

[0015] In one example, the control unit is configured to limit the d-axis current of the machine-side converter through a machine-side weak magnetic control loop to reduce the inductive reactive power output by the machine-side converter; based on the limited d-axis current of the machine-side converter, a q-axis current set value of the grid-side converter is obtained by calculation to reduce the capacitive reactive power output by the grid-side converter.

[0016] In one example, the control unit is configured to determine the output current value of the machine-side weak magnetic control loop based on the actual value of the DC bus voltage, the effective value of the wave voltage of the machine-side converter, and the weak magnetic control loop coefficient; and limit the d-axis current of the machine-side converter based on the output current value of the machine-side weak magnetic control loop.

[0017] In one example, it further includes a power grid simulation device connected between the first transformer and the power grid;

[0018] The control unit is configured to control the grid-side converter and the machine-side converter to jointly perform reactive power support during grid fault ride-through based on the grid fault simulated by the grid simulation device.

[0019] On the other hand, the present application provides a control method for a wind power converter non-functional capacity test system, wherein the wind power converter non-functional capacity test system comprises a wind power converter and a test platform;

[0020] The wind power converter includes a machine-side converter, a bus capacitor and a grid-side converter, and the test platform includes a first transformer, a second transformer, a self-aging switch and a filter unit;

[0021] The AC side of the grid-side converter is connected to one end of the first transformer and one end of the second transformer, the DC side of the grid-side converter is connected to the DC side of the machine-side converter through a bus capacitor, the AC side of the machine-side converter is connected to the other end of the second transformer through a filter unit and a self-aging switch, and the other end of the first transformer is connected to the grid;

[0022] Control methods include:

[0023] Get the reactive power command issued by the host computer;

[0024] Based on the reactive power command, the machine-side converter and the grid-side converter are controlled to cancel reactive power.

[0025] The wind power converter reactive power test system and control method provided in the embodiments of the present application reduce the requirements for test equipment. Only one wind power converter is needed to test the reactive output capacity of the wind power converter and verify the reactive support capacity of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a wind power converter powerless capacity testing system provided in an embodiment of the present application;

[0027] Figure 2 A schematic diagram of a control method for a wind power converter powerless capacity test system provided in an embodiment of the present application;

[0028] Figure 3 A schematic diagram of the output control of the machine-side converter provided in an embodiment of the present application;

[0029] Figure 4 Schematic diagram of the machine-side weak magnetic control loop provided in an embodiment of the present application.

[0030] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0031] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer and more understandable, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0032] like Figure 1 As shown, the wind power converter non-functional capacity test system provided in the embodiment of the present application includes a wind power converter, a test platform and a control unit (not shown);

[0033] The wind power converter includes a machine-side converter, a bus capacitor C1 and a grid-side converter, and the test platform includes a first transformer T1, a second transformer T2, a self-aging switch and a filter unit;

[0034] The AC side of the grid-side converter is connected to one end of the first transformer T1 and one end of the second transformer T2, the DC side of the grid-side converter is connected to the DC side of the machine-side converter through the bus capacitor C1, the AC side of the machine-side converter is connected to the other end of the second transformer T2 through the filter unit and the self-aging switch, and the other end of the first transformer T1 is connected to the grid (shown as Grid in the figure).

[0035] In one example, the first transformer T1 or the second transformer T2 includes a step-down transformer, and the turns ratio of the primary and secondary windings of the step-down transformer is not limited.

[0036] In one example, the filtering unit includes an LC filter.

[0037] In one example, the wind power converter power failure test system further includes a power grid simulation device connected between the first transformer T1 and the power grid, and the power grid simulation device can simulate power grid faults, such as simulating a drop or surge in power grid voltage.

[0038] In an example, the control unit may be integrated in the wind power converter, or may be independent of the wind power converter. The control unit may be configured to execute a control method of a wind power converter non-functional capacity test system.

[0039] like Figure 2 As shown, in one example, a control method of a wind power converter powerless capacity test system includes the following steps:

[0040] S11, obtaining the reactive power instruction issued by the host computer;

[0041] S12. Based on the reactive power instruction, control the machine-side converter and the grid-side converter to perform reactive power cancellation.

[0042] In one example, controlling the generator-side converter and the grid-side converter to perform reactive power cancellation based on the reactive power instruction includes:

[0043] Based on the reactive power instruction, the grid-side converter is controlled to output inductive reactive power and the machine-side converter is controlled to output corresponding capacitive reactive power.

[0044] Specifically, after the control unit obtains the reactive power instruction issued by the host computer, it controls the grid-side converter and the machine-side converter to be connected to the grid on the test platform. The grid-side converter is controlled to output inductive reactive power, and then the control unit determines the q-axis current set value of the grid-side converter; based on the q-axis current set value, the d-axis current of the machine-side converter is converted; according to the d-axis current of the machine-side converter, the machine-side converter is controlled to output the corresponding capacitive reactive power.

[0045] During the implementation, the q-axis current given value of the grid-side converter can be determined according to the reactive power given value of the grid-side converter and the effective value of the AC side voltage of the grid-side converter. As shown in the following formula 1:

[0046] I q_Rec =Q Rec_Ref / U Rec_RMS ; Among them, I q_Rec is the q-axis current given value of the grid-side converter,

[0047] Q Rec_Ref is the reactive power given value of the grid-side converter, U Rec_RMS is the effective value of the AC side voltage of the grid-side converter.

[0048] During the implementation process, the q-axis current given value can be inverted, and then the d-axis current of the machine-side converter can be converted according to the effective value of the AC side voltage of the grid-side converter and the effective value of the AC side voltage of the machine-side converter. The conversion process can be shown in the following formula 2:

[0049] I d_Inv =U Rec_RMS I q_Rec / U Inv_RMS ; Among them, I d_Inv is the d-axis current of the machine-side converter, U Rec_RMS is the effective value of the AC side voltage of the grid-side converter, U Inv_RMS is the effective value of the AC side voltage of the machine-side converter. At this time, the reactive power output of the grid-side converter is Q Rec The reactive power output Q of the machine-side converter Inv equal.

[0050] like Figure 3 As shown, the d-axis current I of the machine-side converter is obtained based on the conversion d_Inv , the d-axis current setting value I of the machine-side converter can be determined dSet_Inv After being adjusted by the PI controller and modulated by the PWM wave generating unit, the generator-side converter is controlled to output capacitive reactive power, completing the reactive support capability verification of the wind power converter.

[0051] In one example, controlling the generator-side converter and the grid-side converter to perform reactive power cancellation based on the reactive power instruction includes:

[0052] Based on the reactive power instruction, the grid-side converter is controlled to output capacitive reactive power and the machine-side converter is controlled to output the corresponding inductive reactive power.

[0053] Specifically, after the control unit obtains the reactive power instruction issued by the host computer, it controls the grid-side converter and the machine-side converter to be connected to the grid on the test platform. The grid-side converter is controlled to output capacitive reactive power, and then the control unit determines the q-axis current given value of the grid-side converter; based on the q-axis current given value, the d-axis current of the machine-side converter is converted; according to the d-axis current of the machine-side converter, the machine-side converter is controlled to output the corresponding inductive reactive power.

[0054] Similar to the above, during the implementation process, the q-axis current given value of the grid-side converter can be determined according to the reactive power given value of the grid-side converter and the effective value of the AC side voltage of the grid-side converter. As shown in the following formula 1:

[0055] I q_Rec =Q Rec_Ref / U Rec_RMS ; Among them, I q_Rec is the q-axis current given value of the grid-side converter,

[0056] Q Rec_Ref is the reactive power given value of the grid-side converter, U Rec_RMS is the effective value of the AC side voltage of the grid-side converter.

[0057] During the implementation process, the q-axis current given value can be inverted, and then the d-axis current of the machine-side converter can be converted according to the effective value of the AC side voltage of the grid-side converter and the effective value of the AC side voltage of the machine-side converter. The conversion process can be shown in the following formula 2:

[0058] I d_Inv =U Rec_RMS I q_Rec / U Inv_RMS ; Among them, I d_Inv is the d-axis current of the machine-side converter, U Rec_RMS is the effective value of the AC side voltage of the grid-side converter, U Inv_RMS is the effective value of the AC side voltage of the machine-side converter. At this time, the reactive power output of the grid-side converter is Q Rec The reactive power output Q of the machine-side converter Inv equal.

[0059] like Figure 3As shown, the d-axis current I of the machine-side converter is obtained based on the conversion d_Inv , the d-axis current setting value I of the machine-side converter can be determined dSet_Inv After being adjusted by the PI controller and modulated by the PWM wave generating unit, the generator-side converter is controlled to output inductive reactive power, completing the reactive support capability verification of the wind power converter.

[0060] In one example, the control method further includes:

[0061] Limiting the d-axis current of the machine-side converter by a machine-side weak magnetic control loop to reduce the inductive reactive power output by the machine-side converter;

[0062] Based on the limited d-axis current of the machine-side converter, a q-axis current given value of the grid-side converter is converted to reduce the capacitive reactive power output by the grid-side converter.

[0063] In this example, when the inductive reactive power output by the machine-side converter is too large, it is easy to cause the AC side voltage of the machine-side converter to be too large, so that the DC bus voltage cannot meet the AC voltage output of the machine-side converter. At this time, the d-axis current of the machine-side converter can be limited by the machine-side weak magnetic control loop to reduce the inductive reactive power output by the machine-side converter and the capacitive reactive power output by the grid-side converter, thereby completing the reactive support capability verification of the wind power converter.

[0064] During the implementation process, the output current value of the machine-side weak magnetic control loop can be determined based on the actual value of the DC bus voltage, the effective value of the wave voltage of the machine-side converter and the weak magnetic control loop coefficient; based on the output current value of the machine-side weak magnetic control loop, the d-axis current of the machine-side converter is limited.

[0065] like Figure 4 As shown, the output current value of the machine-side weak magnetic control loop is calculated by the following formula 3:

[0066]

[0067] Among them, I PIOut_WeakMagn is the output current value of the machine-side weak magnetic control loop, k p k is the proportional coefficient of the weak magnetic control loop; i is the integral coefficient of the weak magnetic control loop; U dc is the actual value of DC bus voltage; U Inv_PWM It is the effective value of the generator-side converter voltage.

[0068] The output current value I based on the machine-side weak magnetic control loop PIOut_WeakMagn , the d-axis current of the machine-side converter can be limited, thereby obtaining the corresponding d-axis current setting value I of the machine-side converterdSet_Inv , thereby limiting the inductive reactive power output by the machine-side converter.

[0069] The output current value I based on the machine-side weak magnetic control loop PIOut_WeakMagn , through the above formula 2, the corresponding q-axis current of the grid-side converter can be reversely converted to thereby limit the capacitive reactive power output by the grid-side converter.

[0070] In one example, the control method further includes:

[0071] Based on the grid fault simulated by the grid simulation device, the grid-side converter and the machine-side converter are controlled to jointly perform reactive support during the grid fault ride-through period.

[0072] In this example, the test platform uses a power grid simulation device to test the grid fault ride-through capability of the wind power converter. During the simulation test, the grid voltage drops or rises suddenly, the wind power converter triggers the fault ride-through flag, and the active output of the machine-side converter is reduced according to the actual grid voltage. During the fault ride-through period, the machine-side converter uses a control logic similar to that of the grid-side converter to provide reactive support, ensuring the normal operation of the wind turbine during the fault ride-through period. After the grid voltage is restored, the wind power converter continues to perform reactive compensation operation.

[0073] In the specific implementation process, first, under the premise of the aforementioned operating conditions, a grid simulation device is used to simulate a grid voltage drop or surge on the test platform. Then the wind power converter triggers the fault ride-through flag, and the active output of the machine-side converter is reduced according to the actual grid voltage. Then, during the fault ride-through period, the machine-side converter and the grid-side converter jointly provide reactive support to ensure the normal operation of the wind turbine. Finally, when the grid voltage is restored, the wind power converter continues to operate according to the instructions before the fault ride-through.

[0074] Among them, in the process of the machine-side converter and the grid-side converter jointly performing reactive support, the reactive support current during the fault ride-through period is first calculated, and then the machine-side converter and the grid-side converter are controlled to output reactive power.

[0075] The preferred embodiments of the present application are described above with reference to the accompanying drawings, but the scope of the present application is not limited thereby. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the present application shall be within the scope of the present application.

Claims

1. A wind power converter powerless capacity test system, characterized in that: Including wind power converter, test platform and control unit; The wind power converter includes a machine-side converter, a bus capacitor and a grid-side converter, and the test platform includes a first transformer, a second transformer, a self-aging switch and a filter unit; The AC side of the grid-side converter is connected to one end of the first transformer and one end of the second transformer, the DC side of the grid-side converter is connected to the DC side of the generator-side converter through the bus capacitor, the AC side of the generator-side converter is connected to the other end of the second transformer through the filter unit and the self-aging switch, and the other end of the first transformer is connected to the grid; The control unit is configured to obtain a reactive power instruction issued by a host computer; based on the reactive power instruction, control the machine-side converter and the grid-side converter to perform reactive power cancellation.

2. The wind power converter non-functional capacity testing system according to claim 1, characterized in that: The control unit is configured to control the grid-side converter to output inductive reactive power and control the generator-side converter to output corresponding capacitive reactive power based on the reactive power instruction.

3. The wind power converter non-functional capacity testing system according to claim 1, characterized in that: The control unit is configured to control the grid-side converter to output capacitive reactive power and control the generator-side converter to output corresponding inductive reactive power based on the reactive power instruction.

4. The wind power converter non-functional capacity testing system according to claim 2 or 3, characterized in that: The control unit is configured to determine a given value of the q-axis current of the grid-side converter; based on the given value of the q-axis current, convert the d-axis current of the machine-side converter; and according to the d-axis current of the machine-side converter, control the reactive power corresponding to the output of the machine-side converter.

5. The wind power converter non-functional capacity testing system according to claim 4, characterized in that: The control unit is configured to determine a q-axis current set value of the grid-side converter according to a reactive power set value of the grid-side converter and an effective value of an AC side voltage of the grid-side converter.

6. The wind power converter non-functional capacity testing system according to claim 4, characterized in that: The control unit is configured to, after inverting the given value of the q-axis current, convert the d-axis current of the generator-side converter according to the effective value of the AC side voltage of the grid-side converter and the effective value of the AC side voltage of the generator-side converter.

7. The wind power converter non-functional capacity testing system according to claim 3, characterized in that: The control unit is configured to limit the d-axis current of the machine-side converter through a machine-side weak magnetic control loop to reduce the inductive reactive power output by the machine-side converter; and based on the limited d-axis current of the machine-side converter, calculate the q-axis current given value of the grid-side converter to reduce the capacitive reactive power output by the grid-side converter.

8. The wind power converter non-functional capacity testing system according to claim 7, characterized in that: The control unit is configured to determine the output current value of the machine-side weak magnetic control loop based on the actual value of the DC bus voltage, the effective value of the wave voltage of the machine-side converter and the weak magnetic control loop coefficient; Based on the output current value of the machine-side weak magnetic control loop, the d-axis current of the machine-side converter is limited.

9. The wind power converter non-functional capacity testing system according to claim 1, characterized in that: Also included is a power grid simulation device connected between the first transformer and the power grid; The control unit is configured to control the grid-side converter and the generator-side converter to jointly perform reactive support during a grid fault ride-through period based on the grid fault simulated by the grid simulation device.

10. A control method for a wind power converter powerless capacity test system, characterized in that: The wind power converter non-functional capacity test system comprises a wind power converter and a test platform; The wind power converter includes a machine-side converter, a bus capacitor and a grid-side converter, and the test platform includes a first transformer, a second transformer, a self-aging switch and a filter unit; The AC side of the grid-side converter is connected to one end of the first transformer and one end of the second transformer, the DC side of the grid-side converter is connected to the DC side of the generator-side converter through the bus capacitor, the AC side of the generator-side converter is connected to the other end of the second transformer through the filter unit and the self-aging switch, and the other end of the first transformer is connected to the grid; The control method comprises: Get the reactive power command issued by the host computer; Based on the reactive power instruction, the machine-side converter and the grid-side converter are controlled to perform reactive power cancellation.

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