Method for eliminating the influence of a double-fed wind turbine on a phase-locked loop

Abstract

The present application relates to the technical field of power electronic device small signal stability improvement and oscillation suppression technology, and provides a method for eliminating the influence of a double-fed wind turbine phase-locked loop, which comprises the following steps: obtaining a rotor current d-axis component first difference value of a double-fed wind turbine rotor-side current d-axis component reference value and a double-fed wind turbine rotor-side current d-axis component measured value; obtaining a rotor current q-axis component first difference value of a double-fed wind turbine rotor-side current q-axis component reference value and a double-fed wind turbine rotor-side current q-axis component measured value; inputting a double-fed wind turbine stator-side voltage q-axis component measured value into a d-axis impedance remodeling link and a q-axis impedance remodeling link respectively to obtain a rotor current d-axis component second difference value and a rotor current q-axis component second difference value; then obtaining a rotor-side voltage d-axis component reference value and a rotor-side voltage q-axis component reference value output by a machine-side converter, and finally generating a PWM signal of the machine-side converter. The present application reduces the risk of oscillation and simplifies parameter design.

Description

Technical Field

[0001] This invention relates to the field of research on small-signal stability improvement and oscillation suppression technology for power electronic equipment, and in particular to a method for eliminating the influence of the phase-locked loop in a doubly-fed wind turbine. Background Technology

[0002] Doubly fed induction generators (DFIGs) offer advantages over permanent magnet synchronous generators (PMSGs) such as flexible output power regulation and lower manufacturing and maintenance costs, attracting widespread attention from researchers both domestically and internationally and becoming one of the main power generation devices used in renewable energy power plants. They mainly consist of three parts: an asynchronous motor, a generator-side converter, and a grid-side converter. The generator-side converter primarily controls the stator-side output power of the asynchronous motor, while the grid-side converter stabilizes the DC-side capacitor voltage. Since power exchange is mainly completed at the generator side, the grid-side converter has little impact on the overall impedance characteristics of the wind turbine and can be ignored. For control, a classic grid-following control strategy is generally adopted.

[0003] Existing research has found that the use of phase-locked loops (PLLs) causes the port impedance of doubly-fed induction generator (DFIG) wind turbines to exhibit negative resistance characteristics at low frequencies, and introduces frequency coupling. When a weak AC power grid is interconnected with a DFIG, oscillations are prone to occur, jeopardizing the stability of the interconnected system. Furthermore, the introduction of frequency coupling also complicates the design of wind turbine parameters. Summary of the Invention

[0004] In view of this, the present invention provides a method for eliminating the influence of the phase-locked loop of a doubly fed wind turbine, so as to solve the technical problem of reducing the oscillation risk of wind turbine interconnection system and simplifying the design of wind turbine parameters in the prior art.

[0005] This invention provides a method for eliminating the influence of the phase-locked loop in a doubly-fed wind turbine, comprising:

[0006] S1. Obtain the reference value of the d-axis component of the rotor-side current of the doubly-fed induction generator (DFIG) and the first difference between the measured values ​​of the d-axis component of the rotor-side current of the DFIG; and

[0007] Obtain the reference value of the q-axis component of the rotor-side current of the doubly-fed wind turbine and the first difference between the measured values ​​of the q-axis component of the rotor-side current of the doubly-fed wind turbine.

[0008] S2. Obtain the measured value of the q-axis component of the stator side voltage of the doubly-fed wind turbine, and input the measured value of the q-axis component of the stator side voltage of the doubly-fed wind turbine into the d-axis impedance reshaping stage and the q-axis impedance reshaping stage respectively to obtain the second difference of the d-axis component of the rotor current and the second difference of the q-axis component of the rotor current.

[0009] S3. The second difference of the d-axis component of the rotor current and the second difference of the q-axis component of the rotor current are respectively passed through the current PI controller of the machine-side converter to obtain the reference value of the d-axis component of the rotor-side voltage and the reference value of the q-axis component of the rotor-side voltage output by the machine-side converter;

[0010] S4. Based on the reference values ​​of the d-axis component of the rotor-side voltage and the reference values ​​of the q-axis component of the rotor-side voltage, generate the PWM signal for the machine-side converter.

[0011] Further, in step S1, the measured values ​​of the d-axis component and q-axis component of the doubly-fed induction generator (DFIG) rotor-side current are obtained by performing a Park transformation on the three-phase current vector of the DFIG rotor-side current in the stationary coordinate system. The angle used in the Park transformation is θ. pll -θ r θ pll The stator voltage phase angle, θ r This is called the fan rotor phase angle.

[0012] Furthermore, in step S2, the measured value of the q-axis component of the stator voltage of the doubly-fed induction generator (DFIG) is obtained by performing a Park transformation on the three-phase voltage vector of the stator side of the DFIG in a stationary coordinate system. The angle used in the Park transformation is θ. pll .

[0013] Furthermore, step S2 specifically includes the following steps:

[0014] S21. Obtain the measured value of the q-axis component of the stator side voltage of the doubly fed wind turbine, and input the measured value of the q-axis component of the stator side voltage of the doubly fed wind turbine into the d-axis impedance reshaping circuit and the q-axis impedance reshaping circuit respectively to obtain the d-axis feedforward amount and the q-axis feedforward amount;

[0015] S22. Combine the d-axis feedforward and the q-axis feedforward with the first difference of the rotor current d-axis component and the first difference of the rotor current q-axis component, respectively, to calculate the second difference of the rotor current d-axis component and the second difference of the rotor current q-axis component.

[0016] Further, in step 2, the second difference of the d-axis component of the rotor current and the second difference of the q-axis component of the rotor current are obtained by the following expressions:

[0017]

[0018] Where, Δi rd2 Δi represents the second difference between the d-axis components of the rotor current. rq2 Δx1 represents the second difference of the q-axis component of the rotor current, Δx2 represents the d-axis feedforward, Δx2 represents the q-axis feedforward, and Δi represents the second difference of the q-axis component of the rotor current. rd Δi represents the first difference of the d-axis components of the rotor current. rq This represents the first difference of the q-axis component of the rotor current.

[0019] Further, step S2 includes:

[0020] The measured values ​​of the q-axis component of the stator voltage of the doubly fed wind turbine after coordinate transformation are processed through the d-axis impedance reshaping stage and the q-axis impedance reshaping stage to obtain the d-axis feedforward quantity and the q-axis feedforward quantity.

[0021] Furthermore, the d-axis impedance reshaping stage and the q-axis impedance reshaping stage respectively adopt transfer functions:

[0022]

[0023] Among them, G vd (s) represents the transfer function of the d-axis impedance reshaping stage, G vq (s) represents the transfer function of the q-axis impedance reshaping stage, s represents the Laplace operator, and K pPLL K represents the proportional gain of the phase-locked loop PI controller. iPLL I represents the integral gain of the phase-locked loop PI controller. rdref I represents the reference value of the d-axis component of the rotor-side current of a doubly-fed induction generator. rqref G represents the reference value of the q-axis component of the rotor-side current of a doubly-fed wind turbine. HPF (s) represents the transfer function of a second-order high-pass filter.

[0024] Furthermore, the second-order high-pass filter transfer function G HPF (s) includes the following expressions:

[0025]

[0026] Where A(∞) represents the gain coefficient and Q represents the quality factor, typically both the gain coefficient A(∞) and the quality factor Q are taken as 1, ω HPF This represents the cutoff angular frequency of a second-order high-pass filter.

[0027] Furthermore, step S4 specifically includes the following steps:

[0028] S41. Generate a modulation signal to control the doubly-fed wind turbine's machine-side converter based on the reference values ​​of the rotor-side voltage d-axis component and the rotor-side voltage q-axis component;

[0029] S42. The modulation signal of the doubly fed wind turbine's machine-side converter is transmitted to the PWM generator to generate the PWM signal of the machine-side converter.

[0030] The advantages of this invention compared to the prior art are:

[0031] 1. This invention adopts a voltage feedforward method based on the asymmetry of the generator-side converter to reduce the risk of oscillation when the doubly fed wind turbine is interconnected with the AC weak grid and to simplify parameter design.

[0032] 2. After applying the asymmetric voltage feedforward to the converter on the machine side of the doubly fed wind turbine, the low-frequency negative resistance range of the doubly fed wind turbine is greatly eliminated, and the frequency coupling characteristics are also reduced.

[0033] 3. This invention incorporates a second-order high-pass filter in the impedance reshaping stage, thereby preventing the impedance reshaping stage from affecting the steady-state operating point of the doubly-fed wind turbine.

[0034] 4. The measured value of the q-axis component of the stator voltage of the doubly fed wind turbine in this invention, after passing through the d-axis and q-axis impedance reshaping stage, effectively improves the grid connection stability of the doubly fed wind turbine.

[0035] 5. The method of the present invention has a simple structure, is easy to apply in engineering practice, and has good results even when the bandwidth of the phase-locked loop changes. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in this invention, the accompanying drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of a method for eliminating the influence of a doubly-fed fan phase-locked loop provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the control principle of the existing doubly fed wind turbine machine-side converter based on vector control, provided in an embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram of the method for eliminating the influence of the doubly-fed wind turbine phase-locked loop based on the asymmetric voltage feedforward of the machine-side converter, provided by an embodiment of the present invention.

[0040] Figure 4 This is a Bode plot of the equivalent single-input single-output impedance and grid impedance of the doubly fed wind turbine before the impedance reshaping method provided in this embodiment of the invention;

[0041] Figure 5The equivalent single-input single-output impedance and grid impedance Bode plot of the doubly-fed wind turbine after applying the impedance reshaping method provided in the embodiments of the present invention;

[0042] Figure 6 The equivalent single-input single-output impedance and Bode plot of the positive sequence impedance of the doubly fed wind turbine after applying the impedance reshaping method provided in the embodiments of the present invention;

[0043] Figure 7 The waveforms of simulated voltage, current and power before and after applying the impedance reshaping method provided in the embodiments of the present invention are shown. Detailed Implementation

[0044] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0045] The following will describe in detail, with reference to the accompanying drawings, a method for eliminating the influence of the phase-locked loop in a doubly-fed fan.

[0046] Figure 1 This is a flowchart of a method for eliminating the influence of the phase-locked loop in a doubly-fed wind turbine, provided by an embodiment of the present invention.

[0047] Figure 2 This is a schematic diagram of the control principle of the existing doubly fed wind turbine converter based on vector control, provided in an embodiment of the present invention.

[0048] Figure 3 This is a schematic diagram of the method for eliminating the influence of the doubly-fed wind turbine phase-locked loop based on the asymmetric voltage feedforward of the machine-side converter, provided by an embodiment of the present invention.

[0049] like Figure 1 As shown, the method for eliminating the influence of the doubly-fed wind turbine phase-locked loop includes:

[0050] S1. Obtain the reference value of the d-axis component of the rotor-side current of the doubly-fed induction generator (DFIG) and the first difference between the measured values ​​of the d-axis component of the rotor-side current of the DFIG; and

[0051] Obtain the reference value of the q-axis component of the rotor-side current of the doubly-fed wind turbine and the first difference between the measured values ​​of the q-axis component of the rotor-side current of the doubly-fed wind turbine.

[0052] In step S1, the measured values ​​of the d-axis component and q-axis component of the doubly-fed induction generator (DFIG) rotor-side current are obtained by performing a Park transformation on the three-phase current vector of the DFIG rotor-side current in the stationary coordinate system. The angle used in the Park transformation is θ. pll -θ r , where θ pll The stator voltage phase angle, θ r The phase angle of the fan rotor, θ pll θ is obtained by tracking the phase of the stator-side voltage using a phase-locked loop. r Obtained by the encoder.

[0053] S2. Obtain the measured value of the q-axis component of the stator side voltage of the doubly-fed wind turbine, and input the measured value of the q-axis component of the stator side voltage of the doubly-fed wind turbine into the d-axis impedance reshaping stage and the q-axis impedance reshaping stage respectively to obtain the second difference of the d-axis component of the rotor current and the second difference of the q-axis component of the rotor current.

[0054] In step S2, the measured value of the q-axis component of the stator voltage of the doubly-fed induction generator (DFIG) is obtained by performing a Park transformation on the three-phase voltage vector of the stator side of the DFIG in a stationary coordinate system. The angle used in the Park transformation is θ. pll .

[0055] like Figure 2 As shown, in the prior art, impedance reshaping methods all adopt a symmetrical structure to transmit the modulation signal to the PWM generator to generate the PWM signal for controlling the converter on the machine side.

[0056] The impedance reshaping method of this invention features an asymmetric control structure. It primarily utilizes the measured q-axis component of the stator voltage of a doubly-fed induction generator (DFIG) after coordinate transformation. These components are then processed through an impedance reshaping stage to obtain d-axis feedforward values ​​Δx1 and q-axis feedforward values ​​Δx2. These feedforward values ​​are then introduced into the input terminal of the converter current PI controller on the turbine side, thereby achieving the impedance reshaping objective. This method significantly eliminates the low-frequency negative resistance range of the DFIG and reduces frequency coupling characteristics.

[0057] This invention is equivalent to adding two special voltage feedforward branches to the original converter current loop, with corresponding transfer functions for the d-axis and q-axis impedance reshaping stages. Details are as follows:

[0058] Step S2 specifically includes the following steps:

[0059] S21. Obtain the measured value of the q-axis component of the stator side voltage of the doubly fed wind turbine, and input the measured value of the q-axis component of the stator side voltage of the doubly fed wind turbine into the d-axis impedance reshaping circuit and the q-axis impedance reshaping circuit respectively to obtain the d-axis feedforward amount and the q-axis feedforward amount;

[0060] This invention uses only the measured value of the q-axis component of the stator side voltage of the doubly fed wind turbine. After passing through the d-axis and q-axis impedance reshaping stage, the d-axis feedforward quantity Δx1 and the q-axis feedforward quantity Δx2 are obtained. The above feedforward quantities are introduced into the input terminal of the current PI controller of the turbine-side converter to perform impedance reshaping, which effectively improves the grid connection stability of the doubly fed wind turbine.

[0061] S22. Combine the d-axis feedforward and the q-axis feedforward with the first difference of the rotor current d-axis component and the first difference of the rotor current q-axis component, respectively, to calculate the second difference of the rotor current d-axis component and the second difference of the rotor current q-axis component.

[0062] In step 2, the second difference of the d-axis component of the rotor current and the second difference of the q-axis component of the rotor current are obtained by the following expressions:

[0063]

[0064] Where, Δi rd2 Δi represents the second difference between the d-axis components of the rotor current. rq2 Δx1 represents the second difference of the q-axis component of the rotor current, Δx2 represents the d-axis feedforward, Δx2 represents the q-axis feedforward, and Δi represents the second difference of the q-axis component of the rotor current. rd Δi represents the first difference of the d-axis components of the rotor current. rq This represents the first difference of the q-axis component of the rotor current.

[0065] Step S2 includes:

[0066] The measured values ​​of the q-axis component of the stator voltage of the doubly fed wind turbine after coordinate transformation are processed through the d-axis impedance reshaping stage and the q-axis impedance reshaping stage to obtain the d-axis feedforward quantity and the q-axis feedforward quantity.

[0067] The d-axis impedance reshaping stage and the q-axis impedance reshaping stage respectively adopt the following transfer functions:

[0068]

[0069] Among them, G vd (s) represents the transfer function of the d-axis impedance reshaping stage, G vq (s) represents the transfer function of the q-axis impedance reshaping stage, s represents the Laplace operator, and K pPLL K represents the proportional gain of the phase-locked loop PI controller. iPLL I represents the integral gain of the phase-locked loop PI controller. rdref I represents the reference value of the d-axis component of the rotor-side current of a doubly-fed induction generator. rqref G represents the reference value of the q-axis component of the rotor-side current of a doubly-fed wind turbine. HPF(s) represents the transfer function of the second-order high-pass filter. This invention incorporates a second-order high-pass filter into the impedance reshaping stage, thus preventing the impedance reshaping stage from affecting the steady-state operating point of the doubly-fed wind turbine.

[0070] The second-order high-pass filter transfer function G HPF (s) includes the following expressions:

[0071]

[0072] Where A(∞) represents the gain coefficient and Q represents the quality factor, typically both the gain coefficient A(∞) and the quality factor Q are taken as 1, ω HPF This represents the cutoff angular frequency of a second-order high-pass filter. The cutoff angular frequency of this second-order high-pass filter is below 2π×5rad / s, which has a good decoupling and stability improvement effect.

[0073] S3. The second difference of the d-axis component of the rotor current and the second difference of the q-axis component of the rotor current are respectively passed through the current PI controller of the machine-side converter to obtain the reference value of the d-axis component of the rotor-side voltage and the reference value of the q-axis component of the rotor-side voltage output by the machine-side converter;

[0074] S4. Based on the reference values ​​of the d-axis component of the rotor-side voltage and the reference values ​​of the q-axis component of the rotor-side voltage, generate the PWM signal for the machine-side converter.

[0075] Step S4 specifically includes the following steps:

[0076] S41. Generate a modulation signal to control the doubly-fed wind turbine's machine-side converter based on the reference values ​​of the rotor-side voltage d-axis component and the rotor-side voltage q-axis component;

[0077] S42. The modulation signal of the doubly-fed induction generator (DFIG) on the machine-side converter is transmitted to the PWM generator to generate the PWM signal for the machine-side converter. Reference value for the d-axis component of the rotor-side voltage output by the DFIG on the machine-side converter of this invention. Reference value of q-axis component of rotor-side voltage They are represented by the following formulas:

[0078]

[0079]

[0080] Where s represents the Laplace operator, K p K is the proportional gain of the PI controller for the doubly fed wind turbine's machine-side converter current. i The integral gain of the PI controller for the current of the doubly fed wind turbine converter on the machine side; This represents the measured value of the d-axis component of the rotor-side current of a doubly-fed induction generator (DFIG). This represents the measured value of the q-axis component of the rotor-side current of a doubly-fed induction generator (DFIG). rdref Indicates the reference value of the d-component of the rotor-side current of the doubly fed wind turbine, I rqref This represents the reference value of the q-component of the rotor-side current in a doubly-fed wind turbine; G HPF (s) represents the transfer function of a second-order high-pass filter; K pPLL K represents the proportional gain of the phase-locked loop PI controller. iPLL This represents the integral gain of the phase-locked loop PI controller. This is the measured value of the q-axis component of the stator voltage.

[0081] Figure 4 This is a Bode plot of the equivalent single-input single-output impedance and grid impedance of the doubly fed wind turbine before the impedance reshaping method provided in this embodiment of the invention.

[0082] Figure 5 The equivalent single-input single-output impedance and grid impedance Bode plot of the doubly-fed wind turbine after applying the impedance reshaping method provided in the embodiments of the present invention.

[0083] Figure 6 The equivalent single-input single-output impedance and Bode plot of the positive sequence impedance of the doubly fed wind turbine after applying the impedance reshaping method provided in the embodiments of the present invention.

[0084] Figure 7 The waveforms of simulated voltage, current and power before and after applying the impedance reshaping method provided in the embodiments of the present invention are shown.

[0085] like Figures 4 to 7 As shown, Figure 4 Bode plots of the equivalent single-input single-output impedance and grid impedance of the doubly-fed wind turbine before applying the impedance reshaping method, where the solid line is the equivalent single-input single-output impedance of the doubly-fed wind turbine and the dashed line is the grid impedance. Figure 5 Bode plots of the equivalent single-input single-output impedance and grid impedance of the doubly-fed wind turbine after applying the impedance reshaping method of the present invention are shown, wherein the solid line is the equivalent single-input single-output impedance of the doubly-fed wind turbine and the dashed line is the grid impedance. Figure 6 After applying the impedance reshaping method of the present invention, the equivalent single-input single-output impedance and the positive-sequence impedance of the doubly-fed wind turbine are Bode plots, where the solid line represents the equivalent single-input single-output impedance of the doubly-fed wind turbine and the dashed line represents the positive-sequence impedance of the wind turbine.

[0086] Figure 7 The simulation results show the voltage, current, and stator power waveforms of the stator and rotor sides of the doubly fed wind turbine before and after using the impedance reshaping method of this invention on the turbine side converter. Figure 7 In the x-axis, t represents time, in seconds, i.e., [s]. Figure 7 In the ordinate: v sa For the stator-side phase a voltage of the wind turbine, take the per-unit value [pu]; i saFor the stator-side phase a current of the wind turbine, take the per-unit value [pu]; i ra Let P be the phase a current on the rotor side of the wind turbine, and take the per-unit value [pu]. s and Q s The power injected into the stator side of the doubly fed fan is taken as the per-unit value [pu].

[0087] Before and after using the impedance reshaping method of the present invention, from Figure 4 , Figure 5 and Figure 6 The following conclusions can be drawn: Figure 4 After considering the influence of the phase-locked loop, the amplitude-frequency characteristic curves of the equivalent single-input single-output impedance of the doubly-fed wind turbine and the grid impedance intersect at 186Hz, and the phase difference at the intersection point exceeds 180°, indicating that the system has the risk of oscillation. Figure 5 After using the impedance reshaping method of the present invention to eliminate the influence of the phase-locked loop, the amplitude-frequency characteristic curves of the equivalent single-input single-output impedance of the doubly fed wind turbine and the grid impedance intersect at 284Hz, and the phase difference corresponding to the intersection point is much less than 180°, indicating that the stability margin of the wind turbine grid-connected system has been greatly improved. Figure 6 By comparing the equivalent single-input single-output impedance and the positive-sequence impedance characteristics of the doubly-fed wind turbine after impedance reshaping, it can be seen that the two are basically the same, indicating that the frequency coupling characteristics of the doubly-fed wind turbine are basically eliminated after the impedance reshaping method is adopted, and the wind turbine can be approximated as a single-input single-output system.

[0088] Figure 7 During the stable operation of the doubly-fed induction generator (DFIG) wind turbine simulation, the phase-locked loop (PLL) bandwidth was modified, and the impedance reshaping method of this invention was applied. The DFIG remained stable in grid connection for 2 seconds. At 2 seconds, the PLL bandwidth was increased, indicating that the PLL's influence on the wind turbine interconnection system increased, ultimately leading to oscillations. Subsequently, the impedance reshaping method of this invention was applied at 3 seconds. It was observed that after applying this method, the system oscillations were suppressed, demonstrating that the impedance reshaping method can effectively improve the low-frequency negative resistance characteristics of the DFIG and reduce the risk of interconnection system oscillations.

[0089] The method employed in this invention reduces the risk of oscillation when a doubly-fed induction generator (DFIG) is interconnected with a weak AC power grid, simplifying parameter design. By applying this asymmetric voltage feedforward, the low-frequency negative resistance range of the DFIG is greatly eliminated, and the frequency coupling characteristics are also reduced. Only the q-axis component of the stator voltage is used for measurement. The d-axis and q-axis impedance reshaping process effectively improves the grid connection stability of the doubly fed wind turbine; the structure is simple, making it easy to apply in engineering projects, and it has good results even when the phase-locked loop bandwidth changes.

[0090] All of the above-mentioned optional technical solutions can be combined in any way to form the optional embodiments of this application, and will not be described in detail here.

[0091] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0092] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for eliminating the influence of the phase-locked loop in a doubly-fed wind turbine, characterized in that, include: S1. Obtain the reference value of the d-axis component of the rotor-side current of the doubly fed fan and the first difference between the measured values ​​of the d-axis component of the rotor-side current of the doubly fed fan. as well as Obtain the reference value of the q-axis component of the rotor-side current of the doubly-fed wind turbine and the first difference between the measured values ​​of the q-axis component of the rotor-side current of the doubly-fed wind turbine. S2. Obtain the measured value of the q-axis component of the stator side voltage of the doubly-fed wind turbine, and input the measured value of the q-axis component of the stator side voltage of the doubly-fed wind turbine into the d-axis impedance reshaping circuit and the q-axis impedance reshaping circuit respectively to obtain the d-axis feedforward amount and the q-axis feedforward amount; By combining the d-axis feedforward and the q-axis feedforward with the first difference of the rotor current d-axis component and the first difference of the rotor current q-axis component, respectively, the second difference of the rotor current d-axis component and the second difference of the rotor current q-axis component are calculated. S3. The second difference of the d-axis component of the rotor current and the second difference of the q-axis component of the rotor current are respectively passed through the current PI controller of the machine-side converter to obtain the reference value of the d-axis component of the rotor-side voltage and the reference value of the q-axis component of the rotor-side voltage output by the machine-side converter; S4. Based on the reference values ​​of the d-axis component of the rotor-side voltage and the reference values ​​of the q-axis component of the rotor-side voltage, generate the PWM signal for the machine-side converter.

2. The method for eliminating the influence of the phase-locked loop in a doubly-fed wind turbine according to claim 1, characterized in that, In step S1, the measured values ​​of the d-axis component and q-axis component of the rotor-side current of the doubly-fed induction generator (DFIG) are obtained by performing a Park transformation on the three-phase current vector of the DFIG rotor side in a stationary coordinate system. The angle used in the Park transformation is θ. pll -θ r θ pll The stator voltage phase angle, θ r This is called the fan rotor phase angle.

3. The method for eliminating the influence of the doubly-fed wind turbine phase-locked loop according to claim 1, characterized in that, In step S2, the measured value of the q-axis component of the stator voltage of the doubly-fed induction generator (DFIG) is obtained by performing a Park transformation on the three-phase voltage vector of the stator side of the DFIG in a stationary coordinate system. The angle used for the Park transformation is θ. pll .

4. The method for eliminating the influence of the doubly-fed wind turbine phase-locked loop according to claim 1, characterized in that, In step S2, the second difference of the d-axis component of the rotor current and the second difference of the q-axis component of the rotor current are obtained by the following expressions: Where, Δi rd2 Δi represents the second difference between the d-axis components of the rotor current. rq2 Δx1 represents the second difference of the q-axis component of the rotor current, Δx2 represents the d-axis feedforward, Δx2 represents the q-axis feedforward, and Δi represents the second difference of the q-axis component of the rotor current. rd Δi represents the first difference of the d-axis components of the rotor current. rq This represents the first difference of the q-axis component of the rotor current.

5. The method for eliminating the influence of the doubly-fed fan phase-locked loop according to claim 1, characterized in that, Step S2 includes: The measured values ​​of the q-axis component of the stator voltage of the doubly fed wind turbine after coordinate transformation are processed through the d-axis impedance reshaping stage and the q-axis impedance reshaping stage to obtain the d-axis feedforward quantity and the q-axis feedforward quantity.

6. The method for eliminating the influence of the doubly-fed fan phase-locked loop according to claim 5, characterized in that, The d-axis impedance reshaping stage and the q-axis impedance reshaping stage respectively adopt the following transfer functions: Among them, G vd (s) represents the transfer function of the d-axis impedance reshaping stage, G vq (s) represents the transfer function of the q-axis impedance reshaping stage, s represents the Laplace operator, and K pPLL K represents the proportional gain of the phase-locked loop PI controller. iPLL I represents the integral gain of the phase-locked loop PI controller. rdref I represents the reference value of the d-axis component of the rotor-side current of a doubly-fed induction generator. rqref G represents the reference value of the q-axis component of the rotor-side current of a doubly-fed wind turbine. HPF (s) represents the transfer function of a second-order high-pass filter.

7. The method for eliminating the influence of the doubly-fed fan phase-locked loop according to claim 6, characterized in that, The second-order high-pass filter transfer function G HPF (s) includes the following expressions: Where A(∞) represents the gain coefficient and Q represents the quality factor, typically both the gain coefficient A(∞) and the quality factor Q are taken as 1, ω HPF This represents the cutoff angular frequency of a second-order high-pass filter.

8. The method for eliminating the influence of the doubly-fed wind turbine phase-locked loop according to claim 1, characterized in that, Step S4 specifically includes the following steps: S41. Generate a modulation signal to control the doubly-fed wind turbine's machine-side converter based on the reference values ​​of the rotor-side voltage d-axis component and the rotor-side voltage q-axis component; S42. The modulation signal of the doubly fed wind turbine's machine-side converter is transmitted to the PWM generator to generate the PWM signal of the machine-side converter.

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