Method and device for optimizing current instruction of wind farm under unbalanced voltage fault

Abstract

The application discloses a wind power plant current instruction optimization method and equipment under unbalanced voltage fault, and constructs a complete unbalanced voltage fault double-fed wind power plant current instruction optimization model, which can maximize the current regulation capacity of the wind turbine, can improve the support capacity of the wind power plant to the power grid frequency while guaranteeing the voltage support capacity of the wind power plant during the unbalanced voltage fault, and can simultaneously suppress the stator current imbalance degree, electromagnetic torque oscillation and DC bus voltage oscillation of each wind turbine in the wind power plant during the fault.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wind power generation technology, in particular to a wind farm station current instruction optimization method and device under unbalanced voltage fault. BACKGROUND

[0002] Ensuring the quality of user electricity and avoiding power failure are the primary goals of power grid operation in the world. However, with the increasing complexity of power grid structure and the gradual expansion of the types and scale of power generation resources within the power grid, large-scale power failures occur from time to time worldwide. In order to ensure the frequency and voltage stability of the power system in China under large-scale wind power access, wind farms are required to have dynamic reactive power support capability, that is, when a voltage drop fault occurs in the power system, the wind farm should inject dynamic reactive current into the system to support the recovery of the system voltage. When a three-phase unbalanced voltage fault occurs in the power system, the wind farm should inject positive sequence dynamic reactive current into the system to support the recovery of the positive sequence voltage at the grid connection point, and at the same time absorb negative sequence dynamic reactive current from the system to suppress the rise of negative sequence voltage at the grid connection point.

[0003] The current control strategy of the wind farm station under unbalanced voltage fault has the following problems:

[0004] On the one hand, the traditional current constraint equation cannot accurately describe the current amplitude of the wind turbine under unbalanced voltage fault, and the current constraint model of the wind turbine under unbalanced voltage fault should be expanded to a set of equations composed of current amplitude expressions of each phase.

[0005] On the other hand, under unbalanced voltage fault, due to the simultaneous existence of positive and negative sequence components of the grid connection point voltage and positive and negative sequence components of the wind turbine output current, the doubly-fed motor will simultaneously face problems such as stator current imbalance, electromagnetic power oscillation and DC bus voltage oscillation. Stator current imbalance will cause uneven heating of the stator winding of the doubly-fed motor, thereby damaging the safety and operating life of the components of the doubly-fed motor, electromagnetic power oscillation will cause electromagnetic torque oscillation of the doubly-fed motor, thereby increasing the mechanical burden of the wind turbine, and DC bus voltage oscillation will cause the operating stability of the doubly-fed motor to decline, and in severe cases, will cause the doubly-fed motor to lose stability and trigger the generator tripping.

[0006] Therefore, it is necessary to propose a solution to the problem of how to improve the control performance of multiple wind turbines in the station under unbalanced voltage fault. SUMMARY

[0007] Based on the above background technology, the present application aims to provide a wind farm station current instruction optimization method and device under unbalanced voltage fault, which solves the problem that the traditional current constraint equation cannot accurately describe the operation of multiple wind turbines in the wind farm station under unbalanced voltage fault, thereby causing incorrect control of multiple wind turbines in the wind farm station.

[0008] The application is achieved by the following technical solutions:

[0009] The application provides a wind farm station current instruction optimization method under unbalanced voltage fault, comprising the following steps:

[0010] The grid-connected point voltage of the wind farm station is collected, and the grid-connected voltage is calculated to obtain a three-phase current amplitude expression under unbalanced voltage fault;

[0011] The double-frequency pulsation component amplitude of the doubly-fed motor is calculated based on the grid-connected point voltage;

[0012] A doubly-fed wind farm station current instruction optimization model under unbalanced voltage fault is constructed; wherein the double-frequency pulsation component amplitude is used to construct the optimization objective of the doubly-fed wind farm station current instruction optimization model, and the current amplitude expression is used to construct the constraint condition of the doubly-fed wind farm station current instruction optimization model;

[0013] The doubly-fed wind farm station current instruction optimization model is solved to obtain the doubly-fed wind farm station current instruction.

[0014] In the above technical solution, the grid-connected point voltage of the wind farm station is measured and collected, the grid-connected point voltage is calculated by taking the positive and negative sequence active and reactive current instructions as independent variables, and the current amplitude expression of each phase is obtained; which provides a data basis for constructing the constraint condition of the doubly-fed wind farm station current instruction optimization model under unbalanced voltage fault.

[0015] Then, the double-frequency pulsation component amplitude of the doubly-fed motor is calculated based on the data of the grid-connected point voltage, wherein the double-frequency pulsation component amplitude includes the double-frequency pulsation component amplitude of the output electromagnetic power of the doubly-fed motor and the active and reactive power of the stator side, and the double-frequency pulsation component amplitude of the active power transmission of the grid-side converter and the DC bus capacitor. The purpose is to evaluate the power output characteristics of the doubly-fed motor under the current working state, and to evaluate the power transmission characteristics of the grid-side converter and the DC bus under the current working state, and to provide a data basis for constructing the optimization objective of the doubly-fed wind farm station current instruction optimization model under unbalanced voltage fault.

[0016] The doubly-fed wind farm station current instruction optimization model is constructed, which aims to minimize the active power drop, stator current imbalance, electromagnetic power oscillation and DC bus voltage oscillation of the wind farm and the wind turbine under unbalanced voltage fault, so as to optimize the performance of the wind farm by adjusting the current instruction. The doubly-fed wind farm station current instruction optimization model is constructed by taking the current amplitude expression of each phase as the constraint condition and the double-frequency pulsation component amplitude as the optimization objective. The optimization model is solved to obtain the optimal current instruction, and the instructions are sent to the controllers of each wind turbine to realize the performance optimization of the wind farm.

[0017] By the above steps, the current regulation capability of the wind turbine can be maximized, the voltage support capability of the wind farm during unbalanced voltage fault can be ensured, the support capability of the wind farm to the grid frequency can be improved, and the stator current imbalance degree, electromagnetic torque oscillation and DC bus voltage oscillation of each wind turbine in the farm during the fault can be cooperatively inhibited.

[0018] In an alternative embodiment, the amplitude of the double-frequency pulsating component comprises:

[0019] the amplitude of the double-frequency pulsating component of the active power and the reactive power of the doubly-fed machine on the stator side, and the amplitude of the double-frequency pulsating component of the electromagnetic power output by the doubly-fed machine;

[0020] the amplitude of the double-frequency pulsating component of the active power output by the grid-side converter of the doubly-fed machine, and the amplitude of the double-frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed machine.

[0021] In an alternative embodiment, the calculation process of the amplitude of the double-frequency pulsating component of the active power and the reactive power of the doubly-fed machine on the stator side is as follows:

[0022] obtaining the positive sequence instruction and the negative sequence instruction of the stator current in the synchronous rotating coordinate system, and calculating the positive sequence component and the negative sequence component of the grid point voltage in the synchronous rotating coordinate system;

[0023] calculating the apparent power transmitted by the stator winding of the doubly-fed machine under unbalanced voltage fault according to the positive sequence instruction, the negative sequence instruction, the positive sequence component and the negative sequence component;

[0024] virtually and actually decomposing the apparent power to obtain the amplitude of the double-frequency pulsating component of the active power and the reactive power of the doubly-fed machine on the stator side.

[0025] In an alternative embodiment, the calculation process of the amplitude of the double-frequency pulsating component of the electromagnetic power output by the doubly-fed machine is as follows:

[0026] when the negative sequence active current instruction is set to 0, the amplitude of the double-frequency pulsating component of the reactive power of the doubly-fed machine on the stator side is taken as the amplitude of the double-frequency pulsating component of the stator side reactive power;

[0027] calculating the amplitude of the double-frequency pulsating component of the stator side reactive power to obtain the amplitude of the double-frequency pulsating component of the electromagnetic power output by the doubly-fed machine.

[0028] In an alternative embodiment, the calculation process of the amplitude of the double-frequency pulsating component of the active power output by the grid-side converter of the doubly-fed machine is as follows:

[0029] determine positive sequence current instruction and negative sequence current instruction of the grid-side converter in the synchronous rotating coordinate system according to the grid-connected point voltage;

[0030] calculate positive sequence component amplitude and negative sequence component amplitude of the grid-side converter terminal voltage based on the positive sequence current instruction and the negative sequence current instruction;

[0031] calculate apparent power transmitted to the power grid by the grid-side converter and the filter circuit of the doubly-fed motor under the unbalanced voltage fault according to the positive sequence current instruction, the negative sequence current instruction, the positive sequence component amplitude and the negative sequence component amplitude;

[0032] perform real part and imaginary part decomposition on the apparent power to obtain the amplitude of the two-frequency pulsating component of the active power output by the grid-side converter of the doubly-fed motor.

[0033] In an alternative embodiment, the calculation process of the amplitude of the two-frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed motor is as follows:

[0034] construct a mathematical model of the DC bus voltage of the doubly-fed motor;

[0035] obtain electromagnetic power and stator-side active power, and substitute the electromagnetic power, the stator-side active power and the amplitude of the two-frequency pulsating component of the active power output by the grid-side converter of the doubly-fed motor into the mathematical model to obtain the amplitude of the two-frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed motor.

[0036] In an alternative embodiment, the optimization target comprises a first optimization target, a second optimization target, a third optimization target and a fourth optimization target;

[0037] The first optimization target is constructed based on the active power of the wind farm and the active power of each wind turbine; the second optimization target is constructed based on the negative sequence reactive current instruction output by each wind turbine stator; the third optimization target is constructed based on the amplitude of the two-frequency pulsating component of the electromagnetic power output by the doubly-fed motor; and the fourth optimization target is constructed based on the amplitude of the two-frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed motor.

[0038] The second aspect of the present application provides a wind farm station current instruction optimization system under unbalanced voltage fault, comprising:

[0039] a current amplitude calculation module configured to acquire grid-connected point voltage of the wind farm station, calculate the grid-connected voltage, and obtain current amplitude expression of three phases under unbalanced voltage fault;

[0040] a component amplitude calculation module configured to calculate the amplitude of the two-frequency pulsating component of the doubly-fed motor based on the grid-connected point voltage;

[0041] An instruction optimization module is configured to construct a double-fed wind power plant current instruction optimization model under unbalanced voltage fault; wherein, the double-fed wind power plant current instruction optimization model is constructed by using the amplitude of the twice-frequency fluctuation component as an optimization target, and the current amplitude expression is used as a constraint condition of the double-fed wind power plant current instruction optimization model;

[0042] A solving module is configured to solve the double-fed wind power plant current instruction optimization model to obtain a double-fed wind power plant current instruction.

[0043] The third aspect of the present application provides an electronic device, which comprises a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the wind power plant current instruction optimization method under unbalanced voltage fault when executing the program.

[0044] The fourth aspect of the present application provides a computer readable storage medium, which stores a computer program, and the program is executed by a processor to implement the wind power plant current instruction optimization method under unbalanced voltage fault.

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

[0046] A complete double-fed wind power plant current instruction optimization model under unbalanced voltage fault is constructed, which can maximize the current regulation capability of the wind turbine, can improve the support capability of the wind power plant to the power grid frequency while ensuring the voltage support capability of the wind power plant during unbalanced voltage fault, and can simultaneously suppress the stator current imbalance degree, electromagnetic torque oscillation and DC bus voltage oscillation of each wind turbine in the wind power plant during the fault. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be considered as a limitation to the scope, and for those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0048] Figure 1 The flowchart of the wind power plant current instruction optimization method under unbalanced voltage fault provided for the first embodiment of the present application is shown in the figure;

[0049] Figure 2 The wind turbine stator current waveform diagram provided for the first scheme in the first embodiment of the present application is shown in the figure;

[0050] Figure 3 The wind turbine stator current negative sequence component diagram provided for the first scheme in the first embodiment of the present application is shown in the figure;

[0051] Figure 4 This is the electromagnetic power oscillation diagram of the wind turbine provided in Solution 1 of Example 1 of the present invention;

[0052] Figure 5 This is a power oscillation diagram of the DC side of the fan provided in Solution 1 of Example 1 of the present invention;

[0053] Figure 6 This is a wind turbine stator current waveform diagram provided by Solution 2 in Example 1 of the present invention;

[0054] Figure 7 This is a diagram of the negative sequence component of the wind turbine stator current provided by Solution 2 in Example 1 of the present invention;

[0055] Figure 8 This is the electromagnetic power oscillation diagram of the wind turbine provided in Solution 2 of Example 1 of the present invention;

[0056] Figure 9 This is a diagram of the DC side power oscillation of the fan provided in Solution 2 of Example 1 of the present invention;

[0057] Figure 10 This is a structural diagram of an electronic device provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0058] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0059] Example 1

[0060] Figure 1 This is a flow chart of a method for optimizing wind farm current instructions under unbalanced voltage fault conditions provided in Example 1 of the present invention. Figure 1 As shown in FIG, the method for optimizing the current command of a wind farm under an unbalanced voltage fault includes the following steps:

[0061] Collecting the grid connection point voltage of the wind farm station, calculating the grid connection voltage, and obtaining the current amplitude expression of the three phases under the unbalanced voltage fault;

[0062] Calculating the amplitude of the double frequency pulsation component of the doubly-fed generator based on the grid connection point voltage;

[0063] Constructing a doubly-fed wind farm station current instruction optimization model under an unbalanced voltage fault; wherein, the optimization target of the doubly-fed wind farm station current instruction optimization model is constructed using the amplitude of the double frequency pulsation component, and the constraint condition of the doubly-fed wind farm station current instruction optimization model is constructed using the current amplitude expression;

[0064] Solving the double-fed wind farm station current instruction optimization model to obtain a double-fed wind farm station current instruction.

[0065] It should be noted that the grid-connected point voltage of the wind farm station is measured and collected, and the grid-connected point voltage is calculated with the positive and negative sequence active and reactive current instructions as independent variables to obtain the current amplitude expression of each phase; which provides a data basis for the constraint conditions of the double-fed wind farm station current instruction optimization model under unbalanced voltage fault.

[0066] Then the double-frequency pulsating component amplitude of the doubly-fed motor is calculated based on the data of the grid-connected point voltage, wherein the double-frequency pulsating component amplitude includes the double-frequency pulsating component amplitude of the output electromagnetic power of the doubly-fed motor and the active and reactive power of the stator side, and the double-frequency pulsating component amplitude of the active power transmitted by the grid-side converter and the DC bus capacitor of the doubly-fed motor. The purpose is to evaluate the power output characteristics of the doubly-fed motor under the current working state, and to evaluate the power transmission characteristics of the grid-side converter and the DC bus under the current working state, and to provide a data basis for the optimization objective of the double-fed wind farm station current instruction optimization model under unbalanced voltage fault.

[0067] The double-fed wind farm station current instruction optimization model is constructed, which aims to minimize the active power drop, stator current imbalance, electromagnetic power oscillation and DC bus voltage oscillation of the wind farm and the wind turbine under unbalanced voltage fault, so as to optimize the performance of the wind farm by adjusting the current instruction. The double-fed wind farm station current instruction optimization model is constructed with the current amplitude expression of each phase as the constraint condition and the double-frequency pulsating component amplitude as the optimization objective. Solving the optimization model obtains the optimal current instruction, and the instructions are sent to the controllers of each wind turbine to realize the performance optimization of the wind farm.

[0068] Through the above steps, the current regulation capability of the wind turbine can be maximized, the voltage support capability of the wind farm during unbalanced voltage fault can be ensured, the support capability of the wind farm to the grid frequency can be improved, and the stator current imbalance, electromagnetic torque oscillation and DC bus voltage oscillation of each wind turbine in the station during the fault period can be cooperatively suppressed.

[0069] In an alternative embodiment, the grid-connected voltage is calculated, including the following steps:

[0070] According to the instantaneous symmetrical component theory, the grid-connected voltage is separated into positive and negative sequences to obtain the positive sequence component, the negative sequence component, and the phase angle difference between the positive sequence component and the negative sequence component;

[0071] According to the Park inverse transformation and the constant amplitude principle, the phase angle difference is calculated to obtain a three-phase current expression;

[0072] The three-phase current expression is calculated using the auxiliary angle formula to obtain a three-phase current amplitude expression.

[0073] Where, according to the instantaneous symmetrical component theory, the grid-connected point voltage U a , U b , U c can be decomposed into three-phase symmetrical positive sequence component U a+ , U b+ , U c+ and negative sequence component U a- , U b- , U c- , specifically:

[0074]

[0075] Then, the phase angles of the three-phase positive sequence component and the negative sequence component are calculated, and the calculation process is as follows:

[0076]

[0077] Wherein, represents the initial phase angle of the a-phase positive sequence voltage component U a+ , and represents the initial phase angle of the a-phase negative sequence voltage component U a- .

[0078] Further, the phase angle difference between the positive sequence component and the negative sequence component is a fixed angle β.

[0079] According to the instantaneous symmetrical component theory, the three-phase current I a , I b , I c output by the converter or the stator winding can be decomposed into three-phase symmetrical positive sequence component I a+ , I b+ , I c+ and negative sequence component I a- , I b- , I c- .

[0080] According to the Park inverse transformation, the relationship between the three-phase current amplitude output by the converter or the stator winding under the constant amplitude principle and the positive and negative sequence active and reactive current commands can be expressed as:

[0081]

[0082] Wherein, I d+ and I q+ represent the positive sequence active current command and the positive sequence reactive current command, respectively, and I d- and I q- represent the negative sequence active current command and the negative sequence reactive current command, respectively.

[0083] Further, the embodiment takes the a-phase current as an example, which can be expanded as follows at the instantaneous value of any active current instruction or reactive current instruction:

[0084] I a = cos θ a+ I d+ -sin θ a+ I q+ + cos θ a- I d- + sin θ a- I q-

[0085] = cos θ a+ I d+ -sin θ a+ I q+ + cos(β + θ a+ )I d- + sin(β + θ a+ )I q-

[0086] = (I d+ + cos βI d- + sin βI q- )cos θ a+ -(I q+ + sin βI d- -cos βI q- )sin θ a+

[0087] Similarly, the b-phase and c-phase currents can be further expanded as follows:

[0088]

[0089] According to the current expressions of the above three phases, the amplitude expressions of each phase current with the positive and negative sequence active and reactive current instructions as the independent variables can be calculated by using the auxiliary angle formula; further, the amplitude expressions of each phase current under unbalanced voltage fault are as follows:

[0090]

[0091] In an alternative embodiment, the double-frequency pulsating component amplitude includes:

[0092] The double-frequency pulsating component amplitude of the active power and the reactive power on the stator side of the doubly-fed motor, and the double-frequency pulsating component amplitude of the electromagnetic power output by the doubly-fed motor;

[0093] The double-fed machine outputs a double-frequency pulsating component amplitude of active power at the grid-side converter, and a double-frequency pulsating component amplitude of active power transmitted by the DC bus capacitor of the double-fed machine.

[0094] In an alternative embodiment, the double-fed machine outputs a double-frequency pulsating component amplitude of active power and reactive power at the stator side, and the calculation process is as follows:

[0095] The positive-sequence instruction and the negative-sequence instruction of the stator current in the synchronous rotating coordinate system are obtained, and the positive-sequence component and the negative-sequence component of the grid point voltage in the synchronous rotating coordinate system are calculated;

[0096] The apparent power transmitted by the double-fed machine through the stator winding under unbalanced voltage fault is calculated according to the positive-sequence instruction, the negative-sequence instruction, the positive-sequence component and the negative-sequence component;

[0097] The real and imaginary parts of the apparent power are separated to obtain the double-frequency pulsating component amplitude of active power and reactive power at the stator side of the double-fed machine.

[0098] In an alternative embodiment, the double-fed machine outputs a double-frequency pulsating component amplitude of electromagnetic power, and the calculation process is as follows:

[0099] When the negative-sequence active current instruction is set to 0, the double-frequency pulsating component amplitude of reactive power at the stator side of the double-fed machine is the double-frequency pulsating component amplitude of stator-side reactive power;

[0100] The double-frequency pulsating component amplitude of stator-side reactive power is calculated to obtain the double-frequency pulsating component amplitude of electromagnetic power output by the double-fed machine.

[0101] Specifically, the calculation expression of the apparent power transmitted by the double-fed machine through the stator winding under unbalanced voltage fault is as follows according to the positive-sequence instruction, the negative-sequence instruction, the positive-sequence component and the negative-sequence component:

[0102]

[0103] Wherein, U +,dq+ and U -,dq- represent the positive-sequence component and the negative-sequence component of the grid point voltage in the synchronous rotating coordinate system, respectively. Correspondingly, I s,dq+ and I s,dq- represent the positive-sequence instruction and the negative-sequence instruction of the stator current in the synchronous rotating coordinate system, respectively, and ω g is the angular frequency of the grid point voltage.

[0104] In this embodiment, the coordinate transformation adopts the constant amplitude principle.

[0105] In the embodiment, based on the grid point voltage orientation, the positive sequence component of the grid point voltage in the forward synchronous rotating coordinate system and the negative sequence component of the grid point voltage in the reverse synchronous rotating coordinate system can be further expressed as:

[0106]

[0107] wherein, U + and U - respectively represent the amplitude of the positive sequence component and the negative sequence component of the grid point voltage.

[0108] Similarly, the stator current can also be further decomposed according to the grid point voltage orientation as follows:

[0109]

[0110] wherein, I s,d+ and I s,q+ respectively represent the positive sequence active and reactive current instructions, while I s,d- and I s,q- respectively represent the negative sequence active and reactive current instructions.

[0111] The virtual-real part decomposition of the apparent power can derive the mathematical model of the active power and the reactive power of the doubly-fed motor at the stator side under the unbalanced voltage fault, through which the amplitude of the double-frequency pulsating component of the active power and the reactive power of the doubly-fed motor at the stator side can be determined. Specifically, the mathematical model is expressed as follows:

[0112]

[0113] wherein, P s,0 and Q s,0 respectively represent the direct current components of the active power and the reactive power at the stator side, P s,cos2 and P s,sin2 respectively represent the amplitudes of the cosine component and the sine component of the double-frequency pulsating of the active power, while Q s,cos2 and Q s,sin2 respectively represent the amplitudes of the cosine component and the sine component of the double-frequency pulsating of the reactive power.

[0114] Further, when the negative sequence active current instruction is set to 0, the amplitude of the double-frequency pulsating component of the reactive power of the doubly-fed motor at the stator side can be expressed as:

[0115]

[0116] Further, by calculating the amplitude of the double-frequency pulsating component of the reactive power at the stator side, the amplitude of the double-frequency pulsating component of the electromagnetic power output by the doubly-fed motor can be obtained, and the calculation process is as follows:

[0117]

[0118] In an alternative embodiment, the calculation of the amplitude of the double frequency pulsating component of the active power output by the grid-side converter is as follows:

[0119] determining positive and negative sequence current commands of the grid-side converter in a synchronous rotating reference frame according to the grid point voltage;

[0120] calculating positive and negative sequence component amplitudes of the grid-side converter terminal voltage based on the positive and negative sequence current commands;

[0121] calculating the apparent power of the doubly-fed machine transmitted to the grid through the grid-side converter and the filter circuit under unbalanced voltage fault according to the positive and negative sequence current commands, the positive and negative sequence component amplitudes;

[0122] performing real and imaginary part decomposition on the apparent power to obtain the amplitude of the double frequency pulsating component of the active power output by the grid-side converter.

[0123] In an alternative embodiment, the calculation of the amplitude of the double frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed machine is as follows:

[0124] constructing a mathematical model of the DC bus voltage of the doubly-fed machine;

[0125] obtaining electromagnetic power and stator-side active power, and substituting the electromagnetic power, the stator-side active power and the amplitude of the double frequency pulsating component of the active power output by the grid-side converter into the mathematical model to obtain the amplitude of the double frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed machine.

[0126] Specifically, the voltage equation of the grid-side converter filter circuit in the synchronous rotating reference frame is as follows:

[0127]

[0128] wherein R g and L g represent the resistance and inductance in the filter circuit respectively. I g,dq+ and I g,dq- represent the positive and negative sequence current commands of the grid-side converter in the synchronous rotating reference frame, and the coordinate transformation adopts the constant amplitude principle. V +,dq+ represents the positive sequence component of the grid-side converter terminal voltage in the forward synchronous rotating reference frame, and V -,dq- represents the negative sequence component of the terminal voltage in the reverse synchronous rotating reference frame.

[0129] Further, the calculation process of positive sequence current command and negative sequence current command of the grid-side converter in the synchronous rotating coordinate system according to the grid-connected point voltage is as follows:

[0130]

[0131] Wherein, I g,d+ and I g,q+ represent the positive sequence active and reactive current commands of the grid-side converter, and I g,d- and I g,q- represent the negative sequence active and reactive current commands of the grid-side converter.

[0132] The calculation process of the positive sequence component amplitude and the negative sequence component amplitude of the grid-side converter terminal voltage based on the positive sequence current command and the negative sequence current command is as follows:

[0133]

[0134] Wherein, V +,d+ and V +,q+ represent the d-axis component and the q-axis component of the positive sequence component of the terminal voltage in the forward synchronous rotating coordinate system based on the grid-connected point voltage orientation, and V -,d- and V -,q- represent the d-axis component and the q-axis component of the negative sequence component of the terminal voltage in the reverse synchronous rotating coordinate system based on the grid-connected point voltage orientation.

[0135] Further, the apparent power transmitted by the doubly-fed motor to the grid through the grid-side converter and the filter circuit under unbalanced voltage fault can be represented as:

[0136]

[0137] By decomposing the real part and the imaginary part of the apparent power in the above formula, the mathematical model of the active power transmitted by the doubly-fed motor to the grid through the grid-side converter and the filter circuit under unbalanced voltage fault can be derived:

[0138] P g = Re{S g} = P g,0 + P g,cos2 cos(2ω g t) + P g,sin2 sin(2ω g t)

[0139] Wherein, P g,0 and Q g,0 represent the direct current components of the active power transmitted by the doubly-fed motor to the grid through the grid-side converter and the filter circuit, P g,cos2 and P g,sin2cosine component and the sine component of the double frequency pulsation of the active power transmitted to the power grid by the grid-side converter and the filter circuit of the doubly-fed motor respectively.

[0140] There is a difference in the value between the apparent power output by the grid-side converter of the doubly-fed motor and the apparent power finally transmitted to the power grid, and the expression of the former is:

[0141]

[0142] By separating the real part and the imaginary part of the apparent power, the amplitude of the double frequency pulsation component of the active power output by the grid-side converter of the doubly-fed motor is obtained. Specifically, the active power output by the grid-side converter after separation can be expressed as:

[0143] P c = Re{S c} = P c,0 + P c,cos2 cos(2ω g t) + P c,sin2 sin(2ω g t)

[0144] Wherein, P c,0 represents the direct current component of the active power and the reactive power output by the grid-side converter, and P c,cos2 and P c,sin2 represent the amplitude of the cosine component and the sine component of the double frequency pulsation of the active power output by the grid-side converter respectively.

[0145] Since the resistance in the filter circuit can be ignored compared with the inductance, and the negative sequence active current command is set to 0, the amplitude of the double frequency pulsation component of the active power output by the grid-side converter can be further simplified as:

[0146]

[0147] Further, the mathematical model of the DC bus voltage of the doubly-fed motor is:

[0148]

[0149] Wherein, C represents the DC bus capacitor of the doubly-fed motor.

[0150] The amplitudes of the cosine component and the sine component of the double frequency pulsation of the active power transmitted by the DC bus capacitor are:

[0151]

[0152] In an optional embodiment, the optimization target includes a first optimization target, a second optimization target, a third optimization target and a fourth optimization target.

[0153] The first optimization target is constructed based on the active power of the wind farm and the active power of each wind turbine. The second optimization target is constructed based on the negative sequence reactive current instruction output by the stator side of each wind turbine. The third optimization target is constructed based on the amplitude of the double-frequency pulsating component of the output electromagnetic power of the doubly-fed motor. The fourth optimization target is constructed based on the amplitude of the double-frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed motor.

[0154] The first optimization target is to minimize the sum of the active power drop of the wind farm and the active power drop of each wind turbine.

[0155] Further, the active power output by the wind turbine and the active power output by the wind farm are calculated based on the positive sequence component amplitude of the grid-connected point voltage and the positive sequence active current instruction of the stator side and the grid side converter of the doubly-fed motor. The active power output by the wind farm is the sum of the active power output by each wind turbine.

[0156] Specifically, the active power output expressions of the wind farm and the wind turbine are:

[0157]

[0158] wherein P e,WF and P e,i represent the active power output by the wind farm and the wind turbine respectively, and n represents the number of wind turbines in the wind farm.

[0159] The second optimization target is to minimize the sum of the negative sequence reactive current instructions output by the stator side of each wind turbine.

[0160] Further, the positive sequence active current instruction of the grid side converter is calculated based on the positive sequence active current instruction of the stator side and the slip of the doubly-fed motor. The negative sequence active current instructions of the stator side and the grid side converter are both set to 0.

[0161] Specifically, in order to maintain the stability of the DC bus voltage, considering the proportional relationship between the active power output by the stator side and the rotor side of the doubly-fed motor, the positive sequence active current instruction of the grid side converter is set as:

[0162]

[0163] wherein the superscript i represents the i-th wind turbine inside the wind farm. i represents the slip of the doubly-fed motor.

[0164] Considering that the negative sequence active current is set to 0, the second optimization target is constructed as follows:

[0165]

[0166] The third optimization target is the sum of squares of the amplitude of the second frequency fluctuation component of the electromagnetic power output by each fan, and is constructed based on the amplitude of the second frequency fluctuation component of the electromagnetic power output by the double-fed motor calculated in the foregoing, as follows:

[0167]

[0168] The fourth optimization target is the sum of squares of the amplitude of the second frequency fluctuation component of the active power transmitted by the DC bus capacitor of each fan, and is constructed based on the amplitude of the second frequency fluctuation component of the active power transmitted by the DC bus capacitor of the double-fed motor calculated in the foregoing, as follows:

[0169]

[0170] The four optimization targets above collectively constitute the total optimization target in the current instruction optimization model of the double-fed wind power plant under unbalanced voltage fault.

[0171] In the embodiment, the constraint condition of the current instruction optimization model of the double-fed wind power plant is constructed by using the current amplitude expression, including:

[0172] The first constraint condition: positive and negative sequence reactive current constraint;

[0173] The sum of the positive and negative sequence reactive current instructions of the stator side and the grid side converter of each fan is equal to the value specified in the national standard GB / T 19963.1-2021, that is, the reactive current output by the wind power plant under fault should meet the requirements in the national standard GB / T 19963.1-2021.

[0174] Specifically, the dynamic positive and negative sequence reactive current proportional coefficient is set for the wind power plant, and the first constraint condition is constructed as follows:

[0175]

[0176] wherein, I q+,WF and I q-,WF represent the positive and negative sequence reactive current instructions of the wind power plant during unbalanced voltage fault, I 0,WF represents the reactive current output by the wind power plant before voltage fault, I rat,WF represents the rated current of the wind power plant, K + and K - represent the positive and negative sequence reactive current droop coefficients of the wind power plant.

[0177] The second constraint condition: power safety constraint;

[0178] The active power output by each fan cannot exceed its safety threshold, that is, the active power output of each fan under fault cannot exceed its upper limit of active power output, wherein the second constraint is constructed as follows:

[0179]

[0180] wherein P max,i represents the upper limit of the active power output of the wind turbine, which can be set as the active power output of each wind turbine before the fault.

[0181] The third constraint condition: current safety constraint;

[0182] The amplitude of each phase current of the stator and the grid-side converter cannot exceed the respective safety threshold, and according to the foregoing obtained current amplitude expression of three-phase under unbalanced voltage fault, the amplitude of each phase current of the stator and the grid-side converter cannot exceed the respective safety threshold.

[0183] Specifically, according to the foregoing obtained current amplitude expression of three-phase under unbalanced voltage fault, the amplitude of the stator current and the grid-side converter output current of each wind turbine cannot exceed the maximum safety current threshold, and the stator current constraint equation group of each wind turbine is constructed as follows:

[0184]

[0185] wherein I s,max represents the maximum safety current threshold of the stator winding of the doubly-fed motor.

[0186] The current constraint equation group of the grid-side converter of each wind turbine can be described as:

[0187]

[0188] wherein I g,max represents the maximum safety current threshold of the grid-side converter of the doubly-fed motor.

[0189] In summary, the complete optimization objective of the current instruction optimization model of the doubly-fed wind power station under unbalanced voltage fault includes:

[0190]

[0191] wherein c1 to c4 represent the weight coefficients corresponding to different optimization objectives.

[0192] The complete constraint condition of the current instruction optimization model of the doubly-fed wind power station under unbalanced voltage fault is:

[0193]

[0194] Solve the above-mentioned current instruction optimization model of the doubly-fed wind power station to obtain the current instruction, and issue the obtained current instruction to the controller of each wind turbine.

[0195] A complete current command optimization model of DFIG-based wind farm under unbalanced voltage fault is constructed, which can maximize the current regulation capability of wind turbines, improve the frequency support capability of wind farm while ensuring the voltage support capability of wind farm during unbalanced voltage fault, and simultaneously suppress the stator current unbalance, electromagnetic torque oscillation and DC bus voltage oscillation of each wind turbine in wind farm.

[0196] In this embodiment, the current command optimization method of wind farm under unbalanced voltage fault is verified based on MATLAB / Simulink simulation environment to reflect the specific effect.

[0197] Specifically, the wind farm contains 200 wind turbines in 4 rows, and the rated capacity of each wind turbine is 2 MW. The filter inductance of wind turbine is 250 μH, the filter capacitance on DC side is 16 mF, and the rated voltage on DC side is 1200 V. The active power output of each row of wind turbines before fault is 0.83 p.u., 0.70 p.u., 0.58 p.u. and 0.37 p.u. respectively. The positive sequence and negative sequence reactive current droop factors are both set to 2. The maximum safe current threshold of stator winding of DFIG is set to 1.2 p.u., and the maximum safe current threshold of grid-side converter is set to 0.36 p.u. The rated frequency of the system is 50 Hz. The weight coefficients of the four optimization objectives are set to 10, 1, 1 and 2 respectively.

[0198] Various dynamic reactive power support schemes of wind farm under voltage fault are used for comparative analysis:

[0199] Scheme 1 is the conventional dynamic reactive power support scheme of wind farm, the reactive current droop factor of each wind turbine is 2, and the remaining converter capacity is used to output active current;

[0200] Scheme 2 is the current command optimization method of wind farm under unbalanced voltage fault with only the first optimization objective, i.e. single-objective optimization;

[0201] Scheme 3 is the current command optimization method of wind farm under unbalanced voltage fault with all optimization objectives, i.e. multi-objective optimization.

[0202] Among them, Table 1 and Table 2 show the control performance comparison of each scheme under single-phase voltage fault, and Table 3 and Table 4 show the control performance comparison of each scheme under two-phase voltage fault. It can be found that the wind farm under the three control schemes can output the required positive sequence and negative sequence reactive current.

[0203] Table 1

[0204]

[0205] Table 2

[0206]

[0207] Table 3

[0208]

[0209]

[0210] Table 4

[0211]

[0212] However, since the wind turbines in different operating states in scheme 1 output corresponding reactive currents according to fixed reactive current droop coefficients, scheme 1 does not realize coordinated allocation of active power and reactive power among different wind turbines, and fails to fully utilize the current capacity of the wind turbines, so that the active power of the wind farm gradually decreases with the increase of the voltage drop during voltage fault, which is not conducive to maintaining the frequency stability of the power grid.

[0213] Schemes 2 and 3 can fully utilize the current capacity of the wind turbines, and coordinate the allocation of active power and reactive power of the wind turbines according to different operating states, so that the ability to maintain the overall active power of the wind farm during fault is significantly enhanced.

[0214] Since scheme 2 only contains one optimization target, and scheme 3 contains limiting targets such as stator current imbalance, electromagnetic torque oscillation, and DC bus voltage oscillation, the effect of scheme 2 on maintaining the active power of the wind farm during fault is slightly better than that of scheme 3.

[0215] Further, in order to reflect the superiority of the current instruction optimization method for wind farm under unbalanced voltage fault provided by the present application in the multi-objective optimization level, two cases are proposed, i.e., the voltage a-phase amplitude at the grid connection point of the wind farm drops to 0.1 p.u., and the voltage ab-phase amplitudes at the grid connection point of the wind farm drop to 0.2 p.u.

[0216] When the voltage at the point of common coupling (PCC) of the wind farm drops to 0.1 p.u. in phase a, both scheme 2 and scheme 3 can output the required reactive current while maintaining the active power output of the wind farm. The stator current waveforms of the wind turbines in different schemes are shown in the figures, from which it can be inferred that the wind turbines have sufficient current margin to support the voltage and maintain the active power output. The figures show the negative sequence component of the stator current, electromagnetic power oscillation and DC side power oscillation of the wind turbines in different schemes. The negative sequence component of the stator current of the wind turbines in scheme 2 differs greatly, with the negative sequence component of the stator current of the fourth row of wind turbines reaching more than 0.6 p.u. After multi-objective optimization, the negative sequence component of the stator current of the wind turbines in scheme 3 is maintained below 0.5 p.u. At the same time, the amplitude of the two-frequency component of the electromagnetic power of the fourth row of wind turbines in scheme 2 is close to 0.4 p.u., indicating that the mechanical burden of the fourth row of wind turbines in scheme 2 is high. After multi-objective optimization, the amplitude of the two-frequency component of the electromagnetic power of the first three rows of wind turbines in scheme 3 is close to that in scheme 2, while the amplitude of the two-frequency component of the electromagnetic power of the fourth row of wind turbines is significantly suppressed. At the same time, the control effect of the DC side power oscillation of the wind turbines in scheme 3 is close to that in scheme 2.

[0217] In summary, under the multi-objective optimization of the wind farm station current instruction optimization method (i.e. scheme 3), the active power output of the wind farm and the DC side power oscillation are close to those under the single-objective optimization of the wind farm station current instruction optimization method (i.e. scheme 2), while the stator current imbalance and electromagnetic power oscillation are significantly lower than those in scheme 2.

[0218] When the voltage at the point of common coupling (PCC) of the wind farm drops to 0.1 p.u. in phase a, both scheme 2 and scheme 3 can output the required reactive current while maintaining the active power output of the wind farm. The stator current waveforms of the wind turbines in different schemes are shown in the figures, from which it can be inferred that the wind turbines have sufficient current margin to support the voltage and maintain the active power output. The figures show the negative sequence component of the stator current, electromagnetic power oscillation and DC side power oscillation of the wind turbines in different schemes. The negative sequence component of the stator current of the wind turbines in scheme 2 differs greatly, with the negative sequence component of the stator current of the fourth row of wind turbines reaching more than 0.6 p.u. After multi-objective optimization, the negative sequence component of the stator current of the wind turbines in scheme 3 is maintained below 0.5 p.u. At the same time, the amplitude of the two-frequency component of the electromagnetic power of the fourth row of wind turbines in scheme 2 is close to 0.4 p.u., indicating that the mechanical burden of the fourth row of wind turbines in scheme 2 is high. After multi-objective optimization, the amplitude of the two-frequency component of the electromagnetic power of the first three rows of wind turbines in scheme 3 is close to that in scheme 2, while the amplitude of the two-frequency component of the electromagnetic power of the fourth row of wind turbines is significantly suppressed. At the same time, the control effect of the DC side power oscillation of the wind turbines in scheme 3 is close to that in scheme 2.

[0219] In summary, under the multi-objective optimization of the wind farm station current instruction optimization method under unbalanced voltage fault (i.e. scheme 3), the active power output and DC side power oscillation of the wind farm are close to those under the single-objective optimization of the wind farm station current instruction optimization method under unbalanced voltage fault (i.e. scheme 2), while the stator current imbalance and electromagnetic power oscillation are obviously lower than those under scheme 2.

[0220] It is proved by the above embodiments that the wind farm station current instruction optimization method under unbalanced voltage fault provided by the present application can not only enhance the active power output capability of the wind farm during the fault, but also simultaneously optimize the stator current imbalance, electromagnetic torque oscillation, DC bus voltage oscillation and the like of the wind turbine during the fault. In the method, the current margin of each wind turbine is fully utilized, and the coordinated control between wind turbines in different operating states is effectively realized.

[0221] Embodiment 2

[0222] The embodiment 2 of the present application provides a wind farm station current instruction optimization system under unbalanced voltage fault, comprising:

[0223] a current amplitude calculation module, configured to collect grid-connected point voltage of the wind farm station, calculate the grid-connected voltage, and obtain a current amplitude expression of three phases under unbalanced voltage fault;

[0224] a component amplitude calculation module, configured to calculate a double-frequency pulsation component amplitude of the doubly-fed motor based on the grid-connected point voltage;

[0225] an instruction optimization module, configured to construct a doubly-fed wind farm station current instruction optimization model under unbalanced voltage fault; wherein the double-frequency pulsation component amplitude is used to construct an optimization objective of the doubly-fed wind farm station current instruction optimization model, and the current amplitude expression is used to construct a constraint condition of the doubly-fed wind farm station current instruction optimization model;

[0226] a solving module, configured to solve the doubly-fed wind farm station current instruction optimization model to obtain a doubly-fed wind farm station current instruction.

[0227] Embodiment 3

[0228] Figure 10 A structural schematic diagram of an electronic device provided by the embodiment 3 of the present application is shown in FIG. 1, which includes a processor 21, a memory 22, an input device 23 and an output device 24. The number of processors 21 in the computer device can be one or more, and one processor 21 is taken as an example in the embodiment. Figure 10 The processor 21, the memory 22, the input device 23 and the output device 24 in the electronic device can be connected through a bus or other means, and the connection through a bus is taken as an example in the embodiment. Figure 10 Figure 10 ​​

[0229] The memory 22 can be used to store software programs, computer executable programs and modules as a computer readable storage medium. The processor 21 executes various functions and data processing of the electronic device by running the software programs, instructions and modules stored in the memory 22, that is, implements the wind farm station current instruction optimization method under unbalanced voltage fault of embodiment 1.

[0230] The memory 22 can mainly include a program storage area and a data storage area, wherein the program storage area can store an operating system and at least one application required by a function; the data storage area can store data created according to the use of the terminal, etc. In addition, the memory 22 can include a high-speed random access memory, and can also include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, or other non-volatile solid-state memory device. In some examples, the memory 22 can further include a memory remotely arranged with respect to the processor 21, which can be connected to the electronic device through a network. Examples of the above network include but are not limited to the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0231] The input device 23 can be used to receive the id and password input by the user, etc. The output device 24 is used to output the network configuration page.

[0232] Embodiment 4

[0233] The embodiment 4 of the present application also provides a computer readable storage medium, and the computer executable instructions are used to implement the wind farm station current instruction optimization method under unbalanced voltage fault as provided in embodiment 1 when executed by a computer processor.

[0234] The storage medium provided by the embodiment of the present application includes computer executable instructions, which are not limited to the method operations provided in embodiment 1, and can also perform related operations in the wind farm station current instruction optimization method under unbalanced voltage fault provided by any embodiment of the present application.

[0235] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for optimizing wind farm current instructions under unbalanced voltage fault conditions, characterized in that: The steps include: Collecting the grid connection point voltage of the wind farm station, calculating the grid connection voltage, and obtaining the current amplitude expression of the three phases under the unbalanced voltage fault; The amplitude of the double frequency pulsation component of the doubly-fed generator is calculated based on the grid connection point voltage; wherein the amplitude of the double frequency pulsation component includes: The amplitude of the double frequency pulsating component of the active power and reactive power on the stator side of the doubly fed machine, and the amplitude of the double frequency pulsating component of the output electromagnetic power of the doubly fed machine; The amplitude of the double-frequency pulsating component of the active power output by the doubly-fed generator at the grid-side converter, and the amplitude of the double-frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed generator; Constructing a doubly-fed wind farm station current instruction optimization model under an unbalanced voltage fault; wherein, the optimization target of the doubly-fed wind farm station current instruction optimization model is constructed using the amplitude of the double-frequency pulsation component, and the constraint conditions of the doubly-fed wind farm station current instruction optimization model are constructed using the current amplitude expression; wherein, the optimization targets include a first optimization target, a second optimization target, a third optimization target, and a fourth optimization target; Among them, the first optimization target is constructed based on the active power of the wind farm and the active power of each wind turbine; the second optimization target is constructed based on the negative sequence reactive current command output from the stator side of each wind turbine; the third optimization target is constructed based on the amplitude of the double frequency pulsating component of the electromagnetic power output by the doubly fed generator; the fourth optimization target is constructed based on the amplitude of the double frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly fed generator; The doubly-fed wind farm station current instruction optimization model is solved to obtain the doubly-fed wind farm station current instruction.

2. The method for optimizing wind farm current instructions under unbalanced voltage fault according to claim 1, characterized in that: The calculation process of the amplitude of the double frequency pulsation component of the active power and reactive power on the stator side of the doubly fed machine is as follows: Obtaining a positive sequence instruction and a negative sequence instruction of the stator current in a synchronous rotating coordinate system, and calculating a positive sequence component and a negative sequence component of the grid connection point voltage in the synchronous rotating coordinate system; Calculating the apparent power transmitted by the doubly-fed generator through the stator winding under an unbalanced voltage fault according to the positive-sequence command, the negative-sequence command, the positive-sequence component, and the negative-sequence component; The apparent power is decomposed into real and imaginary parts to obtain the amplitude of the double frequency pulsating component of the active power and reactive power of the doubly fed generator on the stator side.

3. The method for optimizing wind farm current instructions under unbalanced voltage fault according to claim 2, characterized in that: The calculation process of the amplitude of the double frequency pulsation component of the output electromagnetic power of the doubly fed generator is as follows: When the negative sequence active current command is set to 0, the amplitude of the double frequency pulsation component of the reactive power on the stator side of the doubly fed machine is used as the amplitude of the double frequency pulsation component of the reactive power on the stator side; The amplitude of the double frequency pulsating component of the stator-side reactive power is calculated to obtain the amplitude of the double frequency pulsating component of the output electromagnetic power of the doubly-fed motor.

4. The method for optimizing wind farm current instructions under unbalanced voltage fault according to claim 1, characterized in that: The calculation process of the amplitude of the double frequency pulsation component of the active power output by the doubly fed machine at the grid-side converter is as follows: Determining a positive sequence current command and a negative sequence current command of a grid-side converter in a synchronous rotating coordinate system according to the grid connection point voltage; Calculating the positive-sequence component amplitude and the negative-sequence component amplitude of the grid-side converter terminal voltage based on the positive-sequence current instruction and the negative-sequence current instruction; Calculating the apparent power transmitted from the doubly-fed generator to the grid via the grid-side converter and the filter circuit under an unbalanced voltage fault according to the positive-sequence current command, the negative-sequence current command, the positive-sequence component amplitude, and the negative-sequence component amplitude; The apparent power is decomposed into real and imaginary parts to obtain the amplitude of the double frequency pulsating component of the active power output by the doubly fed generator at the grid-side converter.

5. The method for optimizing wind farm current instructions under unbalanced voltage fault according to claim 4, characterized in that: The calculation process of the amplitude of the double frequency pulsation component of the active power transmitted by the DC bus capacitor of the doubly fed machine is as follows: Construct a mathematical model of the DC bus voltage of a doubly-fed generator; The electromagnetic power and the stator-side active power are obtained, and the electromagnetic power, the stator-side active power and the amplitude of the double-frequency pulsating component of the active power output by the doubly-fed machine at the grid-side converter are substituted into the mathematical model to obtain the amplitude of the double-frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed machine.

6. Wind farm current instruction optimization system under unbalanced voltage fault, characterized by: include: A current amplitude calculation module is used to collect the grid connection point voltage of the wind farm station, calculate the grid connection voltage, and obtain the current amplitude expression of the three phases under the unbalanced voltage fault; A component amplitude calculation module calculates the amplitude of the double frequency pulsation component of the doubly fed generator based on the grid connection point voltage; wherein the amplitude of the double frequency pulsation component includes: The amplitude of the double frequency pulsating component of the active power and reactive power on the stator side of the doubly fed machine, and the amplitude of the double frequency pulsating component of the output electromagnetic power of the doubly fed machine; The amplitude of the double-frequency pulsating component of the active power output by the doubly-fed generator at the grid-side converter, and the amplitude of the double-frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly-fed generator; An instruction optimization module is used to construct a doubly-fed wind farm station current instruction optimization model under an unbalanced voltage fault; wherein the optimization target of the doubly-fed wind farm station current instruction optimization model is constructed using the amplitude of the double-frequency pulsation component, and the constraint conditions of the doubly-fed wind farm station current instruction optimization model are constructed using the current amplitude expression; wherein the optimization targets include a first optimization target, a second optimization target, a third optimization target, and a fourth optimization target; Among them, the first optimization target is constructed based on the active power of the wind farm and the active power of each wind turbine; the second optimization target is constructed based on the negative sequence reactive current command output from the stator side of each wind turbine; the third optimization target is constructed based on the amplitude of the double frequency pulsating component of the electromagnetic power output by the doubly fed generator; the fourth optimization target is constructed based on the amplitude of the double frequency pulsating component of the active power transmitted by the DC bus capacitor of the doubly fed generator; The solution module is used to solve the doubly-fed wind farm station current instruction optimization model to obtain the doubly-fed wind farm station current instruction.

7. An electronic device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the method for optimizing the current instruction of a wind farm station under an unbalanced voltage fault according to any one of claims 1 to 5 is implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for optimizing wind farm current instructions under unbalanced voltage fault conditions as claimed in any one of claims 1 to 5 is implemented.

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