Control method and control system for reactive power coordination of doubly-fed fan

Abstract

The invention provides a double-fed fan reactive power coordination control method and system, and belongs to the technical field of double-fed fans, and the method comprises the steps: constructing a mathematical model and a passive control strategy structure of a double-fed fan passive control system; determining the relation between the common connection point voltage of the modular multilevel converter and the output voltage of the converter station according to the mathematical model of the passive control system, determining the maximum value of the output voltage of the converter station according to the passive control strategy, and obtaining the steady-state reactive power regulation capability of the passive control system; and constructing a reactive power regulation strategy of the passive control system based on the steady-state reactive power regulation capability, and performing reactive power coordination control on the doubly-fed fan. According to the invention, reactive power regulation is carried out by using the reactive power regulation capability of the wind turbine generator, the response speed is improved, and the reactive power of the converter station is ensured to be within a safe and stable operation range.

Description

Technical Field

[0001] The present invention belongs to the technical field of doubly-fed wind turbines, and in particular relates to a reactive power coordinated control method and a control system for doubly-fed wind turbines. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Direct transmission of wind power via flexible direct current is an effective way to solve the current difficulties in wind power consumption. When wind power is transmitted via flexible direct current, the converter station needs to simulate the output of a stable voltage by a synchronous generator to achieve reliable grid connection of wind power. When the reactive power output of the converter station exceeds the steady-state regulation capability of the converter station, the voltage at the common connection point will not be able to stabilize at the target value. Therefore, it is necessary to put forward requirements for reactive power compensation of the passive system to ensure that the reactive power of the converter station does not exceed its regulation range. In the current actual project operation, the ability of wind turbines to provide reactive power is not fully utilized, and the response to the system is insufficient.

[0004] When the converter station adopts passive control, the reactive power output by the converter station is uncontrollable. Influenced by economy, the converter station connected to the wind power side currently gives priority to transmitting active power. However, when the active power of wind power changes, because the converter station presents voltage source characteristics, the converter station will adjust the output reactive power to meet the system requirements. When the reactive power exceeds the limit, it may cause the controller of the converter station to saturate. For the problems caused by reactive power exceeding the limit and the control method after the reactive power of the passive system exceeds the limit, the existing technology mostly adopts the method of adding reactive compensation devices at the station, but this method has a slow effect time and poor economy. Summary of the invention

[0005] To overcome the above-mentioned deficiencies of the prior art, the present invention proposes a reactive coordination control method and control system for a doubly-fed wind turbine, which utilizes the reactive regulation capability of the wind turbine to perform reactive regulation and ensure that the reactive power of the converter station is within a safe and stable operating range.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: In a first aspect, a reactive coordination control method for a doubly-fed wind turbine is disclosed, comprising: Construct the mathematical model and passive control strategy structure of the doubly-fed wind turbine passive control system; According to the mathematical model of the passive control system, the relationship between the common connection point voltage of the modular multilevel converter and the output voltage of the converter station is determined, and the maximum output voltage of the converter station is determined according to the passive control strategy. Based on the relationship between the common connection point voltage and the output voltage of the converter station and the maximum output voltage of the converter station, the steady-state reactive power regulation capability of the passive control system is obtained; Based on the steady-state reactive power regulation capability, a reactive power regulation strategy of the passive control system is constructed to carry out reactive power coordinated control of the doubly-fed wind turbine.

[0007] Furthermore, in the passive control system of the doubly-fed wind turbine, the mathematical model of the AC side of the converter station in the dq coordinate system is:

[0008] in, R eq is the equivalent internal resistance of the modular multilevel converter, and R eq =R t +R arm / 2 ; L eq is the equivalent internal inductance of the modular multilevel converter, and L eq =L t +L arm / 2 ; R t is the transformer equivalent resistance; L t is the transformer equivalent inductance; L arm is the equivalent inductance of the bridge arm; R arm is the equivalent resistance of the bridge arm; is the rated rotation frequency; i c is the output current of the converter station at the sending end; u s is the voltage at the common connection point of the modular multilevel converter; u c is the output voltage of the converter station at the sending end; d, q Respectively dq Rotating coordinate system d Axis and q Axis electrical quantities.

[0009] Furthermore, the relationship between the common connection point voltage and the converter station output voltage is:

[0010] in, i c is the output current of the sending-end converter station; u s is the voltage at the common connection point of the modular multilevel converter; u cis the output voltage of the converter station at the sending end; d, q Respectively dq Rotating coordinate system d Axis and q Shaft electrical quantities; is the rated rotation frequency; L eq is the equivalent internal inductance of the modular multilevel converter.

[0011] Furthermore, the maximum value of the converter station output voltage is, which satisfies the following expression:

[0012] The maximum voltage must meet the following constraints: The control requirement is limited by the maximum steady-state current:

[0013] When the converter station is connected to the wind turbine, the active power can only flow into the converter station:

[0014] in, u cmax is the maximum output voltage of the converter station; I max is the maximum value of steady-state current; the reactive current transmitted by the converter station is limited to meet the steady-state operation of the converter station. Furthermore, the operating range of the q-axis current in steady state is:

[0015] The above formula indicates that, when the d-axis current is constant, there is a limit to the reactive current operating range of the converter station; the maximum reactive current flowing out of the converter station is greater than the maximum reactive current flowing into the converter station; the larger the amplitude of the output voltage of the converter station, the larger the operating range of the reactive current, and there is a maximum operating range; the smaller the common connection point voltage operating target value of the modular multilevel converter, the larger the reactive current adjustment space, and there is a maximum operating range.

[0016] Furthermore, the priority of reactive power regulation strategy is: (1) Reactive power control of grid-side converter of doubly-fed wind turbine; (2) Reactive power control on the stator side of the doubly-fed wind turbine; (3) Reactive power compensation of the system reactive power compensation device.

[0017] Furthermore, in the reactive power regulation strategy, the grid-side converter and the stator-side reactive power control are decoupled, and the threshold of the reference voltage is set to satisfy the relationship:

[0018] in, U ref is the grid-side converter voltage reference value; U ref0 is the initial value of the grid-side converter voltage reference value; U ref1 is the threshold value of the reference voltage; U ref2 is the maximum voltage allowed by the grid-side converter, Q stator It is the reactive power generated by the stator. The judgment logic is: when the grid-side converter voltage is greater than the threshold but still cannot meet the reactive power demand of the system, the stator takes over the reactive power dynamic adjustment capability, and the stator starts to generate reactive power. At this time, the grid-side converter voltage target value is the set value, and it no longer participates in dynamic adjustment. When the reactive power generated by the stator side is less than 0, the stator gives up the reactive power dynamic adjustment capability, the reactive power constant is set to 0, and the grid-side converter takes over the reactive power dynamic adjustment capability.

[0019] In a second aspect, a reactive coordination control system for a doubly-fed wind turbine is disclosed, comprising: Model building module: it is configured to: build a mathematical model and passive control strategy structure of a doubly-fed wind turbine passive control system; A capacity calculation module is configured to: determine the relationship between the common connection point voltage and the converter station output voltage according to the mathematical model of the passive control system, determine the maximum value of the converter station output voltage according to the passive control strategy, and obtain the steady-state reactive power regulation capacity of the passive control system based on the relationship between the common connection point voltage and the converter station output voltage and the maximum value of the converter station output voltage; The coordinated control module is configured to: construct a reactive power regulation strategy for a passive control system based on steady-state reactive power regulation capability, and perform reactive power coordinated control on the double-fed wind turbine.

[0020] In a third aspect, an electronic device is disclosed, including a memory and a processor, and computer instructions stored in the memory and running on the processor, wherein when the computer instructions are run by the processor, the steps of the control method for reactive power coordination of the doubly-fed wind turbine are completed.

[0021] In a fourth aspect, a computer-readable storage medium is disclosed for storing computer instructions, which, when executed by a processor, complete the steps of the above-mentioned control method for reactive power coordination of a doubly-fed wind turbine.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present application proposes a control method for reactive power coordination when changes in active power generation cause changes in reactive power. The grid-side converter directly adjusts the reactive power command of the converter to quickly adjust the output reactive power, thereby improving the response speed of reactive power coordination control. The rotor-side converter indirectly adjusts the output power by adjusting the rotor excitation voltage. When the reactive power output by the wind turbine rotor-side converter does not meet the system requirements, it is continuously supplemented from the stator side of the doubly-fed wind turbine. Long-term reactive power regulation can be adjusted by the reactive power compensation device of the system according to the dispatching command, thereby improving both the response speed and the reactive power coordination effect.

[0023] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 This is an equivalent circuit diagram of the doubly-fed wind turbine passive system connected to the MMC as described in the first embodiment of the present invention.

[0026] Figure 2 It is a schematic diagram of the structure of the flexible DC passive control strategy with a current inner loop described in the first embodiment of the present invention.

[0027] Figure 3 This is an equivalent circuit diagram of the AC side of the converter station described in the first embodiment of the present invention.

[0028] Figure 4 It is the operating space of the DQ axis current described in the first embodiment of the present invention.

[0029] Figure 5 This is a control block diagram for generating a reference voltage for a grid-side converter as described in Embodiment 1 of the present invention.

[0030] Figure 6 This is a block diagram of stator-side reactive power control described in Embodiment 1 of the present invention. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0032] It should be noted that the terms used herein are for describing specific embodiments only and are not intended to be limiting of exemplary embodiments according to the present invention.

[0033] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0034] Embodiment 1 In one or more embodiments, a control method for reactive coordination of a doubly-fed wind turbine is disclosed, comprising: Step S1: constructing a mathematical model and passive control strategy structure of a doubly-fed wind turbine passive control system.

[0035] like Figure 1 As shown in the figure, the passive system of the wind farm double-fed wind turbine is connected to the modular multilevel converter (MMC). u w is the voltage at the point of common coupling (PCC) of the fan, and its effective value is ; u s is the PCC point voltage of the MMC, and its effective voltage is ; u c is the output voltage of the converter station at the sending end, and its effective value is ; The positive direction of current and power is from the doubly fed wind turbine to the MMC, is the voltage phase of the wind turbine grid connection point, is the voltage phase of the MMC grid connection point, is the potential phase inside the MMC, is the impedance of the nth line from the wind turbine to the MMC, is the line impedance angle, SM1,...,SMn represent the n submodules of MMC, is the active power of the MMC grid connection point, It is the reactive power of MMC grid connection point.

[0036] Output voltage of the converter station at the sending end u c and the common connection point voltage of the MMC u s And the common connection point voltage of MMC u s and fan common connection point voltage u w The relationship between them is: (1) Among them, the subscript abc Represents the electrical quantity of the three-phase stationary coordinate system; R eq is the equivalent internal resistance of MMC, and R eq =Rt +R arm / 2 ; L eq is the equivalent internal inductance of the MMC, and L eq =L t +L arm / 2 ; R t is the transformer equivalent resistance; L t is the transformer equivalent inductance; L arm is the equivalent inductance of the bridge arm; R arm is the equivalent resistance of the bridge arm; R w Collect the equivalent line resistance for the wind turbine; L w Collect the equivalent line inductance for the wind turbine; i sabc is the current in the line between the fan and the MMC.

[0037] By performing dq transformation on equation (1), equation (2) can be obtained, which is the mathematical model of the AC side of the converter station in the dq coordinate system: (2) Among them, the subscript dq Respectively dq Rotating coordinate system d Axis and q Shaft electrical quantities; is the rated rotation frequency; i c is the output current of the sending-end converter station.

[0038] like Figure 2 As shown in the figure, the structure of the flexible DC passive control strategy with a current inner loop is that the outer loop adopts constant voltage control, the outer loop outputs a current reference value, which is input into the inner loop current control, and the inner loop current control outputs a reference value of the internal potential to realize MMC voltage control; in the figure, the subscript w represents the wind farm variable, the subscripts d and q represent the d-axis and q-axis components in the dq rotating coordinate system respectively, the superscript "cf" represents the variable in the coordinate system where the controller is located, and the superscript "*" represents the reference value.

[0039] In steady state, the converter station takes the PCC point voltage of the MMC as the rated voltage as the control target, and the converter station presents a voltage source with a constant PCC point voltage. Analogous to a synchronous generator, the MMC outlet voltage u cPhysically, it can be equivalent to the internal potential of MMC. The PCC of MMC Voltage u s In terms of physics, it can be equivalent to the terminal voltage. At this time, by adjusting the potential in the converter station, the terminal voltage can be guaranteed to be the target value, such as Figure 3 shown. Figure 3 middle, f 1 (u c ) The relationship determined by formula (2).

[0040] In steady state, the converter station provides a stable voltage for the double-fed wind turbine to be connected to the grid, showing voltage source characteristics. The double-fed wind turbine shows current source characteristics. According to the current source characteristics, the current flowing into the converter station is determined by the double-fed wind turbine, and the external constraint of the converter station is the current constraint, that is, (3) in, i s is the current of the MMC common connection point; i w is the current at the common connection point of the wind turbine; dq Respectively dq Rotating coordinate system d Axis and q Axis electrical quantities.

[0041] Different from active control, according to the characteristics of the PI controller, in passive control, since the actual current is controlled by the doubly fed wind turbine, the converter station cannot control the current flowing into the converter. Therefore, the inner loop current controller realizes the function of the reference current tracking the actual current. When the reference current tracks the actual current, the system reaches a steady state.

[0042] Step S2: Determine the relationship between the PCC point voltage and the converter station output voltage according to the mathematical model of the passive control system, and obtain the maximum value of the converter station output voltage according to the passive control strategy.

[0043] According to formula (2), the resistance is small and can be ignored in steady state, and the voltage at the common connection point of MMC is u s and converter station output voltage u c The relationship between them is: (4) According to the control target, steady state u sd =u sdref , u sq =0 , and because of the voltage limit, the maximum output voltage of the converter station isu cmax , so it can be seen that in order to meet the control requirements, it is necessary to meet: (5) Maximum steady-state current I max The restrictions exist (6) When the converter station is connected to the wind turbine, the active power can only flow into the converter station, so there are constraints: (7) Combining equations (5), (6) and (7), and considering the rated active power of the converter station, the feasible range of the dq axis current in steady state can be obtained as follows: Figure 4 shown.

[0044] Because the passive control converter station mainly transmits active power, when the active current is constant, it is necessary to limit the reactive current transmitted by the converter station to meet the steady-state operation of the converter station. According to equations (5) and (6), the operating range of the q-axis current in steady state can be obtained as: (8) in, I max is the maximum steady-state current.

[0045] From formula (8), we can know that: (1) When the d-axis current is constant, there are limitations on the reactive current operating range of the converter station; (2) The maximum reactive current flowing out of the converter station is greater than the maximum reactive current flowing into the converter station; (3) The larger the amplitude of the voltage that the converter station can output, the larger the operating range of the reactive current, and there is a maximum operating range, that is, the range of the inner loop current limit; (4) The smaller the PCC voltage operating target value of the MMC converter, the larger the reactive current regulation space. There is also a maximum operating range, that is, within the range of the inner loop current limit.

[0046] Step S3: construct a reactive power regulation strategy for a passive control system based on the steady-state reactive power regulation capability, and perform reactive power coordinated control on the doubly-fed wind turbine.

[0047] From the analysis of steps 1-2, it can be seen that when the reactive power output by the converter station exceeds the steady-state regulation capability of the converter station, the PCC point voltage of the MMC converter will not be able to stabilize at the target value. Therefore, it is necessary to make requirements for reactive compensation of the passive system to ensure that the reactive power of the converter station does not exceed its regulation range.

[0048] Both the grid-side converter and the stator of a doubly-fed wind turbine can generate reactive power, but the grid-side converter is limited by the withstand voltage and current of the device and the modulation ratio, and the reactive power regulation capability of the grid-side converter is limited. In addition, the active and reactive power on the stator side are controlled by the rotor current, and the magnitude of the rotor current is limited by the withstand voltage and current of the rotor-side converter, so there is also a certain range.

[0049] Because the response time of the passive control converter station is extremely short, at the millisecond level, in order to meet the needs of rapid response, the wind turbine grid-side converter, which is also an MMC converter, is used to quickly control the system's reactive power and compensate for the reactive power changes caused by the active power changes in the system.

[0050] Due to the limited reactive power regulation capability of the grid-side converter, when the grid-side converter of the wind turbine cannot meet the reactive power demand of the system, it is necessary to use the reactive power regulation capability of the stator side of the doubly fed wind turbine to perform reactive power regulation. Long-term reactive power regulation can be adjusted by the reactive power compensation device of the system according to the dispatching instructions.

[0051] Therefore, the priority of reactive power regulation strategy is determined as follows: (1) Reactive power control of grid-side converter of doubly-fed wind turbine; (2) Reactive power control on the stator side of the doubly-fed wind turbine; (3) Reactive power compensation of the system reactive power compensation device.

[0052] In this embodiment, a communication-based reactive power control strategy for the doubly-fed wind turbine is adopted to coordinately control the reactive power of the doubly-fed wind turbine according to a preset priority.

[0053] First, the reactive power control of the grid-side converter of the doubly-fed wind turbine with the highest priority is adopted. In order to achieve rapid adjustment of reactive power, the reactive power control strategy of the grid-side converter of the doubly-fed wind turbine is controlled as fixed AC voltage control. Specifically, the passive control converter station sends the reactive power of the PCC point of the converter station to the wind turbine in real time. When it is detected that the reactive power of the converter station is greater than the upper limit of operation, the grid-side converter of the wind turbine first adjusts the AC voltage reference value to send out the corresponding reactive power. The control block diagram is shown in the figure. Figure 5 shown.

[0054] In order to ensure the decoupling of grid-side converter and stator reactive power control, so as to avoid interaction of control modes and affect the stability of the control system, the threshold of reference voltage is set. U ref1 , satisfying the relationship: (9) in, U ref is the grid-side converter voltage reference value; U ref0 is the initial value of the grid-side converter voltage reference value; Uref2 is the maximum voltage allowed by the grid-side converter, Q stator is the reactive power generated by the stator. Formula (9) is Figure 5 The judgment logic in the judgment logic is that the grid-side converter first adjusts the reactive power. If the reference voltage generated by the converter station exceeds the threshold U ref1 , it still cannot meet the reactive power demand of the system, and when the stator side of the doubly fed wind turbine starts to generate reactive power, the reference voltage of the converter station is set to a constant value, and it no longer participates in the dynamic regulation of reactive power. The dynamic regulation capability is transferred to the stator of the doubly fed wind turbine.

[0055] Then, the second priority doubly fed wind turbine stator side reactive power control is adopted. The control strategy of the doubly fed wind turbine stator is as follows: Figure 6 As shown, the judgment logic is (10) in, Q statorref is the stator reactive power reference value; Q statorref 0 is the initial value of the stator reactive power reference value; the meaning of the judgment logic is that the stator side of the doubly fed wind turbine does not generate reactive power in steady state. When the system has reactive power demand, the grid-side converter is adjusted first. After the grid-side converter voltage is greater than the threshold, if it still cannot meet the system reactive power demand, the stator takes over the reactive power dynamic adjustment capability, and the stator starts to generate reactive power. At this time, the grid-side converter voltage target value is the set value, and it no longer participates in dynamic adjustment. When the reactive power generated by the stator side is less than 0, the stator surrenders the reactive power dynamic adjustment capability, the reactive power constant is set to 0, and the grid-side converter takes over the reactive power dynamic adjustment capability.

[0056] Finally, reactive power compensation is performed by the reactive power compensation device of the system with the lowest priority. For reactive power regulation over a long period of time, the reactive power compensation device of the system can be used for adjustment according to the dispatching instructions.

[0057] There are two converters in the wind turbine, namely the grid-side converter and the machine-side converter. The machine-side converter is connected to the wind turbine rotor, and the grid-side is directly connected to the power grid. The grid-side converter directly adjusts the converter reactive power command to quickly adjust the output reactive power. The rotor-side converter indirectly adjusts the output power by adjusting the rotor excitation voltage. From the perspective of response speed and the links involved, grid-side converter control is preferred. However, the wind turbine rotor-side converter can output limited reactive power. When it does not meet the system requirements, it needs to be supplemented from the machine side. Through the reactive power regulation control method of the present invention, the efficiency of reactive power regulation is improved, the output reactive power is quickly adjusted, and the stator side of the doubly fed wind turbine has the reactive coordination and supplementary regulation capability to ensure that the reactive power of the converter station is within the safe and stable operation range.

[0058] Embodiment 2 In one or more embodiments, a control system for reactive power coordination of a doubly-fed wind turbine is disclosed, specifically comprising: Model building module: it is configured to: build a mathematical model and passive control strategy structure of a doubly-fed wind turbine passive control system; A capacity calculation module is configured to: determine the relationship between the common connection point voltage of the modular multilevel converter and the output voltage of the converter station according to the mathematical model of the passive control system, determine the maximum output voltage of the converter station according to the passive control strategy, and obtain the steady-state reactive power regulation capacity of the passive control system based on the relationship between the common connection point voltage and the output voltage of the converter station and the maximum output voltage of the converter station; The coordinated control module is configured to: construct a reactive power regulation strategy for a passive control system based on steady-state reactive power regulation capability, and perform reactive power coordinated control on the double-fed wind turbine.

[0059] Embodiment 3 This embodiment provides an electronic device, including a memory and a processor, and computer instructions stored in the memory and running on the processor. When the computer instructions are run by the processor, the steps of the control method for reactive power coordination of the doubly-fed wind turbine are completed.

[0060] Embodiment 4 This embodiment provides a computer-readable storage medium for storing computer instructions. When the computer instructions are executed by a processor, the steps of the control method for reactive power coordination of a doubly-fed wind turbine are completed.

[0061] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0062] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0063] These computer program instructions can also be loaded onto a computer or other programmable data processing device, and a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0064] The description of each embodiment in the above embodiments has different emphases. For parts not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control method for reactive coordination of a doubly-fed wind turbine, characterized in that: include: Construct the mathematical model and passive control strategy structure of the doubly-fed wind turbine passive control system; According to the mathematical model of the passive control system, the relationship between the common connection point voltage of the modular multilevel converter and the output voltage of the converter station is determined, and the maximum output voltage of the converter station is determined according to the passive control strategy. Based on the relationship between the common connection point voltage and the output voltage of the converter station and the maximum output voltage of the converter station, the steady-state reactive power regulation capability of the passive control system is obtained; Based on the steady-state reactive power regulation capability, a reactive power regulation strategy of the passive control system is constructed to carry out reactive power coordinated control of the doubly-fed wind turbine.

2. A control method for reactive coordination of a doubly-fed wind turbine as claimed in claim 1, characterized in that: The mathematical model of the AC side of the converter station in the dq coordinate system of the double-fed wind turbine passive control system is: in, R eq is the equivalent internal resistance of the modular multilevel converter, and R eq =R t +R arm / 2 ; L eq is the equivalent internal inductance of the modular multilevel converter, and L eq =L t +L arm / 2 ; R t is the transformer equivalent resistance; L t is the transformer equivalent inductance; L arm is the equivalent inductance of the bridge arm; R arm is the equivalent resistance of the bridge arm; is the rated rotation frequency; i c is the output current of the converter station at the sending end; u s is the voltage at the common connection point of the modular multilevel converter; u c is the output voltage of the converter station at the sending end; d, q Respectively dq Rotating coordinate system d Axis and q Axis electrical quantities.

3. A control method for reactive coordination of a doubly-fed wind turbine as claimed in claim 1, characterized in that: The relationship between the common connection point voltage of the modular multilevel converter and the output voltage of the converter station is: in, i c is the output current of the converter station at the sending end; u s is the voltage at the common connection point of the modular multilevel converter; u c is the output voltage of the converter station at the sending end; d, q Respectively dq Rotating coordinate system d Axis and q Axis electrical quantities; is the rated rotation frequency; L eq is the equivalent internal inductance of the modular multilevel converter.

4. A control method for reactive coordination of a doubly-fed wind turbine as claimed in claim 1, characterized in that: The maximum output voltage of the converter station satisfies the following expression: The maximum voltage must meet the following constraints: The control requirement is limited by the maximum steady-state current: When the converter station is connected to the wind turbine, the active power can only flow into the converter station: in, u cmax is the maximum output voltage of the converter station; I max is the maximum value of steady-state current; the reactive current transmitted by the converter station is limited to meet the steady-state operation of the converter station.

5. A control method for reactive coordination of a doubly-fed wind turbine as claimed in claim 4, characterized in that: The operating range of the q-axis current in steady state is: The above formula indicates that, when the d-axis current is constant, there is a limit to the reactive current operating range of the converter station; the maximum reactive current flowing out of the converter station is greater than the maximum reactive current flowing into the converter station; the larger the amplitude of the output voltage of the converter station, the larger the operating range of the reactive current, and there is a maximum operating range; the smaller the common connection point voltage operating target value of the modular multilevel converter, the larger the reactive current adjustment space, and there is a maximum operating range.

6. A control method for reactive coordination of a doubly-fed wind turbine as claimed in claim 1, characterized in that: The priority of the reactive power regulation strategy is: (1) Reactive power control of grid-side converter of doubly-fed wind turbine; (2) Reactive power control on the stator side of the doubly-fed wind turbine; (3) Reactive power compensation of the system reactive power compensation device.

7. A control method for reactive coordination of a doubly-fed wind turbine as claimed in claim 1, characterized in that: In the reactive power regulation strategy, the grid-side converter and the stator-side reactive power control are decoupled, and the threshold of the reference voltage is set to satisfy the relationship: in, U ref is the grid-side converter voltage reference value; U ref0 is the initial value of the grid-side converter voltage reference value; U ref1 is the threshold value of the reference voltage; U ref2 is the maximum voltage allowed by the grid-side converter, Q stator It is the reactive power generated by the stator. The judgment logic is: when the grid-side converter voltage is greater than the threshold but still cannot meet the reactive power demand of the system, the stator takes over the reactive power dynamic adjustment capability, and the stator starts to generate reactive power. At this time, the grid-side converter voltage target value is the set value, and it no longer participates in dynamic adjustment. When the reactive power generated by the stator side is less than 0, the stator gives up the reactive power dynamic adjustment capability, the reactive power constant is set to 0, and the grid-side converter takes over the reactive power dynamic adjustment capability.

8. A control system for reactive power coordination of a doubly-fed wind turbine, characterized in that: include: Model building module: it is configured to: build a mathematical model and passive control strategy structure of a double-fed wind turbine passive control system; A capability calculation module is configured to: determine the relationship between the common connection point voltage of the modular multilevel converter and the output voltage of the converter station according to the mathematical model of the passive control system, determine the maximum output voltage of the converter station according to the passive control strategy, and obtain the steady-state reactive power regulation capability of the passive control system based on the relationship between the common connection point voltage of the modular multilevel converter and the output voltage of the converter station and the maximum output voltage of the converter station; The coordinated control module is configured to: construct a reactive power regulation strategy for a passive control system based on steady-state reactive power regulation capability, and perform reactive power coordinated control on the double-fed wind turbine.

9. An electronic device, characterized in that: The method comprises a memory and a processor and computer instructions stored in the memory and executed on the processor. When the computer instructions are executed by the processor, the control method for reactive power coordination of a doubly-fed wind turbine as claimed in any one of claims 1 to 7 is completed.

10. A computer-readable storage medium, characterized in that: Used to store computer instructions, which, when executed by a processor, complete the control method for reactive power coordination of a doubly-fed wind turbine as described in any one of claims 1 to 7.

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