A method for improving transient voltage support capability of doubly-fed wind turbine generator systems

Abstract

The present invention discloses a method for improving the transient voltage support capability of a doubly fed wind turbine generator set, which relates to the field of grid stability regulation and comprises the following steps: step S1: obtaining detailed parameters of a doubly fed wind power grid-connected system; step S2: calculating a phase-locked loop phase-locked error angle according to the detailed parameters; step S3: calculating a current reference value of a doubly fed wind turbine rotor-side converter taking into account phase jumps during low voltage ride-through; step S4: calculating a current reference value of a doubly fed wind turbine rotor-side converter taking into account phase jumps after grid voltage recovery; step S5: calculating a rotor-side converter voltage equation taking into account phase jumps; step S6: designing a control logic strategy according to the obtained detailed parameters of the doubly fed wind power grid-connected system and the calculated phase-locked error angle, suppressing the influence of the phase-locked error on the power output characteristics of the wind turbine by modifying the current reference value of the rotor-side converter and combining the improvement of the rotor-side voltage equation, thereby improving the transient voltage support capability of the doubly fed wind turbine after a short circuit fault.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid stabilization and regulation, and in particular to a method for improving the transient voltage support capability of a doubly-fed wind turbine generator set. Background Art

[0002] Doubly-fed wind turbines have certain reactive power source characteristics that can actively support grid transient voltage after a grid fault. However, after a short-circuit fault occurs in a doubly-fed wind power grid-connected system, the grid voltage phase angle will jump as the system's access impedance changes. If the doubly-fed wind turbine's phase-locked loop (PLL) cannot accurately lock phase at this time, the doubly-fed wind turbine will over- or under-generate reactive power, thereby reducing its transient voltage support capability and compromising the safe operation of the doubly-fed wind power system.

[0003] Existing methods often suppress the impact of phase-locked loop (PLL) errors on the transient voltage support capability of a doubly fed wind turbine by compensating for the phase-locked loop (PLL) phase angle. However, existing methods for improving transient voltage support capability suffer from the following three issues: 1) Improving the wind turbine's transient voltage support capability by changing the PLL's control structure complicates the PLL's structure and affects its robustness; 2) they fail to consider the impact of PLL errors on the DC-axis current decoupling of the DFIG's rotor-side converter; and 3) they typically focus only on a specific phase of the wind turbine's transient voltage support, lacking a comprehensive transient voltage support capability improvement method that encompasses both the turbine's low-voltage ride-through phase and the grid voltage recovery phase. Furthermore, the control of a DFIG system primarily focuses on the power control of the DFIG, achieved through control of its rotor-side converter. The grid-side converter is primarily responsible for controlling the DC bus voltage stability and ensuring good AC input performance, and does not directly participate in controlling the DFIG. Therefore, the control performance of the rotor-side converter directly impacts the operational performance of the DFIG system. The rotor-side converter uses a phase-locked loop (PLL) to obtain frequency and phase information from the grid voltage. Phase-lock errors can cause doubly-fed wind turbines to over- or under-generate power, further deteriorating the voltage level at the wind farm's grid connection point. Therefore, a method to improve the transient voltage support capability of doubly-fed wind turbines throughout the entire process, taking phase jumps into account, is urgently needed to enhance the stable operation of wind power grid-connected systems. Summary of the Invention

[0004] In view of the above-mentioned prior art, the present invention provides a method for improving the transient voltage support capability of a doubly-fed wind turbine generator system, mainly to solve the technical problems existing in the above-mentioned background technology.

[0005] To achieve the above-mentioned purpose, the technical solution of the embodiment of the present invention is implemented as follows:

[0006] A method for improving the transient voltage support capability of a doubly-fed wind turbine generator system, the method comprising the following steps:

[0007] Step S1: Obtain detailed parameters of the doubly-fed wind power grid-connected system;

[0008] Step S2: Calculate the phase-locked loop phase error angle based on the detailed parameters, and analyze the impact of the phase-locked error angle on the electrical quantities of the doubly fed wind turbine;

[0009] Step S3: calculating a current reference value of a doubly-fed wind turbine rotor-side converter taking into account phase jump during low voltage ride-through;

[0010] Step S4: calculating a current reference value of the doubly-fed wind turbine rotor-side converter taking into account phase jump after grid voltage recovery;

[0011] Step S5: Calculating the rotor-side converter voltage equation taking into account the phase jump;

[0012] Step S6: designing a control logic strategy based on the acquired detailed parameters of the doubly-fed wind power grid-connected system and the calculated phase-lock error angle.

[0013] Specifically, the detailed parameters of the doubly-fed wind power grid-connected system obtained in step S1 include:

[0014] Grid connection point voltage U s , double-fed wind turbine stator output active power reference value P sref , actual value P s , double-fed wind turbine stator output reactive power reference value Q sref , actual value Q s , the maximum allowable current of the rotor-side converter of the doubly fed wind turbine , rated current of the rotor-side converter of the doubly fed wind turbine , reactive current proportional coefficient K , the grid connection point voltage output by the phase-locked loop d Axis component u dPLL 、 q Axis component u qPLL , rotor side resistance of doubly fed wind turbine R r ,inductance L r , magnetic flux leakage coefficient σ , the rotor current of the doubly fed wind turbine d Axis component 、 q Axis component , stator side inductance L s , the mutual inductance between the stator and the rotor L m , rotor rotation angular velocity ωr , synchronous angular velocity ω 1.

[0015] Specifically, the grid connection point voltage output by the phase-locked loop in step S2 is d Axis component u dPLL 、 q Axis component u qPLL Calculate the phase-lock error angle. The specific formula is as follows:

[0016]

[0017] in, is the phase-lock error angle.

[0018] Specifically, step S3 includes: during the low voltage ride-through period, the active / reactive outer loop of the wind turbine rotor-side converter is disconnected, and the doubly-fed wind turbine generator system should be guaranteed to operate continuously without disconnecting from the grid within a certain voltage range, that is, without taking into account the phase jump. At this time, the current reference value of the inner loop can be directly given according to the traditional current reference value:

[0019]

[0020] in, For wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, For wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, is the maximum allowable current of the wind turbine rotor side converter, is the stator side inductance, is the mutual inductance between the stator and the rotor, is the synchronous angular velocity, is the grid connection point voltage, is the reactive current proportional coefficient, is the rated current of the doubly fed wind turbine rotor-side converter, Output current on the stator side of the fan Initial value of the axis component; when the doubly fed wind turbine generator system is off-grid, the reference value of the doubly fed wind turbine rotor-side converter current taking into account the phase jump during the low voltage ride-through period is as follows:

[0021]

[0022] in, Considering phase jump for wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, Considering phase jump for wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, is the sine value of the phase-locking error angle, is the cosine value of the phase-lock error angle.

[0023] Specifically, step S4 includes: after the grid voltage is restored, the active / reactive outer loop of the wind turbine rotor-side converter is reconnected. At this time, the current reference value of the inner loop is given by the outer loop. Then, after the grid voltage is restored, the current reference value of the inner loop of the rotor-side converter is as follows:

[0024] in, After the grid voltage is restored, the wind turbine rotor side converter Shaft current reference value, After the grid voltage is restored, the wind turbine rotor side converter Shaft current reference value, 、 are the active power outer loop PI control parameters, 、 are the reactive power outer loop PI control parameters, 、 are the reference value and actual value of the stator output active power of the doubly fed wind turbine, 、 are the reference value and actual value of the reactive power output of the doubly fed wind turbine stator respectively; when the reference value of the converter inner loop current cannot be directly given after the outer loop is connected, a compensation value is added on the basis of the inner loop current reference value, which is as follows: in, A wind turbine rotor-side converter that takes into account phase jumps after grid voltage recovery Shaft current reference value, A wind turbine rotor-side converter that takes into account phase jumps after grid voltage recovery Shaft current reference value.

[0025] Specifically, the step S5 specifically includes: after the short circuit fault occurs, the phase-locked error causes the phase angle locked by the phase-locked loop to be no longer equal to the actual grid voltage phase angle, and the rotation angular velocity output by the phase-locked loop is Synchronous angular velocity are no longer equal, the voltage equation of the doubly fed wind turbine rotor-side converter after taking into account the phase jump is:

[0026]

[0027] in, 、 The rotor voltage is 、 Axis component, 、 are the rotor side resistance and inductance, 、 The rotor current is 、 Axis component, is the rotor rotation angular velocity, is the angular velocity of the phase-locked loop output, is the magnetic flux leakage coefficient.

[0028] Specifically, the control logic strategy designed in step S6 according to the obtained detailed parameters of the doubly fed wind power grid-connected system and the calculated phase-locked error angle specifically includes: when a short-circuit fault occurs, if the per-unit value of the grid-connected point voltage amplitude is less than 0.9, the control outer loop of the doubly fed wind turbine rotor-side converter is disconnected. At this time, if the phase-locked error angle is 0, the traditional low voltage ride-through control strategy is adopted. At this time, the rotor current reference values ​​are respectively 、 If the phase-locked error angle is not 0, the control strategy of the current reference value of the doubly fed wind turbine rotor side converter taking into account the phase jump is adopted. At this time, the rotor current reference values ​​are 、 ;

[0029] When the short-circuit fault is cleared, the grid voltage begins to recover. If the per-unit value of the grid-connected voltage amplitude is greater than 0.9, the control outer loop of the doubly fed wind turbine rotor-side converter is reconnected. At this time, if the phase-locked error angle is 0, the control is terminated. At this time, the rotor current reference values ​​are 、 If the phase-locked error angle is not 0, a compensation control strategy is added to the inner loop current reference value. At this time, the rotor current reference value is added 、 ;At the same time, the rotation angular velocity output by the phase-locked loop Replace the synchronous angular velocity term in the rotor-side converter voltage equation .

[0030] The beneficial effects of the present invention are:

[0031] (1) Traditional control methods often suppress the influence of phase-locked error on the transient voltage support capability of the doubly fed wind turbine by modifying the control structure of the phase-locked loop, which results in a complex phase-locked loop structure and poor robustness. The control method proposed in the present invention suppresses the influence of phase-locked error by adjusting the current reference value of the rotor-side converter of the doubly fed wind turbine. There is no need to modify the control structure of the phase-locked loop and the robustness is good.

[0032] (2) The traditional control method does not consider the influence of the phase-locked loop error on the decoupling effect of the AC- and DC-axis currents of the doubly-fed wind turbine rotor-side converter. The control method proposed in this invention improves the decoupling effect of the AC- and DC-axis currents by improving the rotor-side voltage equation of the doubly-fed wind turbine. Compared with the traditional control method, the control method proposed in this invention has better control effect.

[0033] (3) Phase-locked error occurs both during the duration of the fault and after the fault is cleared. Traditional control methods often only consider one of the two stages. The control method proposed in this invention covers both the duration of the fault and the stage after the fault is cleared. It is a method for improving the transient voltage support capability of the entire process. Compared with the traditional control method that only considers a single stage, the control method proposed in this invention is more in line with the actual situation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A flowchart of the steps of this method is provided;

[0035] Figure 2 The control block diagram provided for this method;

[0036] Figure 3 Schematic diagram of the control logic strategy provided by this method;

[0037] Figure 4 The structure diagram of the doubly-fed wind power grid-connected system provided by this method;

[0038] Figure 5 is the voltage amplitude of the grid connection point under different control methods during a slight voltage drop;

[0039] Figure 6 is the voltage amplitude of the grid connection point under different control methods during severe voltage drop. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further elaborated in detail below in conjunction with the drawings and specific embodiments of the specification. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In the following description, reference is made to "some embodiments", which describes a subset of all possible embodiments, but it should be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0041] In the following description, numerous specific details are provided to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without one or more of these details. In other instances, certain technical features well known in the art are not described to avoid confusion with the present invention.

[0042] It should be understood that the present invention can be implemented in different forms and should not be interpreted as being limited to the embodiments proposed herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. And the purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates another way. It should also be understood that the terms "comprising" and / or "comprising" when used in this specification determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0043] It should also be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "inner," "outer," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only implementation methods.

[0044] In order to fully understand the present invention, a detailed structure will be provided in the following description to illustrate the technical solution proposed by the present invention. Optional embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementations.

[0045] Please refer to the attached Figure 1The present application provides a method for improving the transient voltage support capability of a doubly-fed wind turbine generator system, the method comprising the following steps: step S1: obtaining detailed parameters of a doubly-fed wind power grid-connected system; step S2: calculating a phase-locked loop phase-locked error angle based on the detailed parameters, and analyzing the influence of the phase-locked error angle on the electrical quantities of the doubly-fed wind turbine; step S3: calculating a current reference value of a doubly-fed wind turbine rotor-side converter taking into account phase jumps during low voltage ride-through; step S4: calculating a current reference value of a doubly-fed wind turbine rotor-side converter taking into account phase jumps after grid voltage recovery; step S5: calculating a rotor-side converter voltage equation taking into account phase jumps; step S6: designing a control logic strategy based on the obtained detailed parameters of the doubly-fed wind power grid-connected system and the calculated phase-locked error angle.

[0046] Specifically, the detailed parameters of the doubly-fed wind power grid-connected system obtained in step S1 include:

[0047] Grid connection point voltage U s , double-fed wind turbine stator output active power reference value P sref , actual value P s , double-fed wind turbine stator output reactive power reference value Q sref , actual value Q s , the maximum allowable current of the rotor-side converter of the doubly fed wind turbine , rated current of the rotor-side converter of the doubly fed wind turbine , reactive current proportional coefficient K , the grid connection point voltage output by the phase-locked loop d Axis component u dPLL 、 q Axis component u qPLL , rotor side resistance of doubly fed wind turbine R r ,inductance L r , magnetic flux leakage coefficient σ , the rotor current of the doubly fed wind turbine d Axis component 、 q Axis component , stator side inductance L s , the mutual inductance between the stator and the rotor L m , rotor rotation angular velocity ω r , synchronous angular velocity ω 1.

[0048] Specifically, the grid connection point voltage output by the phase-locked loop in step S2 is d Axis component u dPLL 、 q Axis component u qPLL Calculate the phase-lock error angle. The specific formula is as follows:

[0049]

[0050] in, is the phase-lock error angle.

[0051] The influence of phase-locking error on the electrical quantity of the doubly fed wind turbine is analyzed as follows:

[0052] The rotor side converter obtains the grid connection point voltage information through the phase-locked loop, and the phase-locked error affects the grid connection point voltage. 、 The influence of the axial components can be derived from the following equation:

[0053]

[0054] in, and They are the grid connection point voltages output by the phase-locked loop when the phase-locked error is not taken into account. Axis component, Axis component.

[0055] Considering that the control speed of the phase-locked loop is much lower than that of the current inner loop, the influence of the phase-locked error on the output current of the doubly fed wind turbine rotor side can be approximately ignored.

[0056] When there is no phase-locking error, the output power on the stator side of the doubly fed wind turbine is:

[0057]

[0058] in, P s is the actual value of the active power output of the doubly fed wind turbine stator, Q s The actual value of the reactive power output of the doubly-fed wind turbine stator.

[0059] When affected by the phase-locked error, the output power on the stator side of the doubly fed wind turbine is:

[0060]

[0061] in, 、 They are respectively the active and reactive power output on the stator side of the doubly fed wind turbine affected by the phase-locked error;

[0062] It can be seen that the phase-locking error will affect the stator-side output power of the doubly fed wind turbine, and thus affect its transient voltage support capability.

[0063] Specifically, step S3 includes: during the low voltage ride-through period, the active / reactive outer loop of the wind turbine rotor-side converter is disconnected, and the doubly-fed wind turbine generator system should be guaranteed to operate continuously without disconnecting from the grid within a certain voltage range, that is, without taking into account the phase jump. At this time, the current reference value of the inner loop can be directly given according to the traditional current reference value:

[0064]

[0065] in, For wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, For wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, is the maximum allowable current of the wind turbine rotor side converter, is the stator side inductance, is the mutual inductance between the stator and the rotor, is the synchronous angular velocity, is the grid connection point voltage, is the reactive current proportional coefficient, is the rated current of the doubly fed wind turbine rotor-side converter, Output current on the stator side of the fan Initial value of the axis component; when the doubly fed wind turbine generator system is off-grid, the reference value of the doubly fed wind turbine rotor-side converter current taking into account the phase jump during the low voltage ride-through period is as follows:

[0066]

[0067] in, Considering phase jump for wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, Considering phase jump for wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, is the sine value of the phase-locking error angle, is the cosine value of the phase-lock error angle.

[0068] When the above current reference value is adopted, the output power on the stator side of the doubly fed wind turbine is:

[0069]

[0070] in, 、 They are respectively the active power and reactive power outputted on the stator side of the doubly-fed wind turbine after adopting the control method proposed in the present invention.

[0071] It can be seen that the use of the current reference value proposed in the present invention can eliminate the influence of the phase-locking error on the output power of the wind turbine stator side.

[0072] Specifically, step S4 includes: after the grid voltage is restored, the active / reactive outer loop of the wind turbine rotor-side converter is reconnected. At this time, the current reference value of the inner loop is given by the outer loop. Then, after the grid voltage is restored, the current reference value of the inner loop of the rotor-side converter is as follows:

[0073]

[0074] in, After the grid voltage is restored, the wind turbine rotor side converter Shaft current reference value, After the grid voltage is restored, the wind turbine rotor side converter Shaft current reference value, 、 are the active power outer loop PI control parameters, 、 are the reactive power outer loop PI control parameters, 、 are the reference value and actual value of the stator output active power of the doubly fed wind turbine, 、 are the reference value and actual value of the reactive power output of the doubly fed wind turbine stator respectively; when the reference value of the converter inner loop current cannot be directly given after the outer loop is connected, a compensation value is added on the basis of the inner loop current reference value, which is as follows:

[0075]

[0076] in, A wind turbine rotor-side converter that takes into account phase jumps after grid voltage recovery Shaft current reference value, A wind turbine rotor-side converter that takes into account phase jumps after grid voltage recovery Shaft current reference value.

[0077] Specifically, when there is no phase-lock error and grid voltage-oriented vector control is adopted, the voltage equation of the wind turbine rotor-side converter is:

[0078]

[0079] After a short circuit occurs, the phase-locked error causes the phase angle of the phase-locked loop to be no longer equal to the actual grid voltage phase angle. At this time, the rotational angular velocity output by the phase-locked loop is Synchronous angular velocity are no longer equal, if the rotor side converter still uses synchronous angular velocity Building decoupled items will affect 、 The shaft current decoupling effect is achieved. Therefore, the voltage equation of the doubly fed wind turbine rotor-side converter after taking into account the phase jump is:

[0080]

[0081] in, 、 The rotor voltage is 、 Axis component, 、 are the rotor side resistance and inductance, 、 The rotor current is 、 Axis component, is the rotor rotation angular velocity, is the angular velocity of the phase-locked loop output, is the magnetic flux leakage coefficient.

[0082] Please refer to Appendix 2 and Appendix Figure 3 Specifically, the control logic strategy designed in step S6 according to the obtained detailed parameters of the doubly fed wind power grid-connected system and the calculated phase-locked error angle specifically includes: when a short-circuit fault occurs, if the per-unit value of the grid-connected point voltage amplitude is less than 0.9, the control outer loop of the doubly fed wind turbine rotor-side converter is disconnected. At this time, if the phase-locked error angle is 0, the traditional low voltage ride-through control strategy is adopted. At this time, the rotor current reference values ​​are respectively 、 If the phase-locked error angle is not 0, the control strategy of the current reference value of the doubly fed wind turbine rotor side converter taking into account the phase jump is adopted. At this time, the rotor current reference values ​​are 、 ;

[0083] When the short-circuit fault is cleared, the grid voltage begins to recover. If the per-unit value of the grid-connected voltage amplitude is greater than 0.9, the control outer loop of the doubly fed wind turbine rotor-side converter is reconnected. At this time, if the phase-locked error angle is 0, the control is terminated. At this time, the rotor current reference values ​​are 、 If the phase-locked error angle is not 0, a compensation control strategy is added to the inner loop current reference value. At this time, the rotor current reference value is added 、 ;At the same time, the rotation angular velocity output by the phase-locked loop Replace the synchronous angular velocity term in the rotor-side converter voltage equation .

[0084] In order to verify the control effect of the method for improving the transient voltage support capability of the doubly fed wind turbine generator system proposed in this invention, the Figure 4 The control effects of the proposed method and the traditional control method under the wind power grid-connected system structure are shown. The working condition is as follows: at 3 seconds, a three-phase ground short circuit fault occurs at the grid-connected point of the doubly fed wind farm, and the fault lasts for 0.2 seconds.

[0085] (1) Mild voltage drop

[0086] Attachment Figure 5 The figure shows the grid connection point voltage amplitude under different control methods during a mild voltage sag. It can be seen that compared with the traditional control method, the control method proposed in this invention can significantly improve the grid connection point voltage during the fault period, which is beneficial to the safe operation of the system. After the grid voltage recovers, the grid connection point voltage peak value is 1.083 pu using the traditional control method, while the grid connection point voltage peak value is 1.051 pu using the control method proposed in this invention. It can be seen that the method proposed in this invention can effectively reduce the overvoltage peak value of the grid connection point.

[0087] (2) Severe voltage drop

[0088] Attachment Figure 6 The figure shows the grid connection point voltage amplitude under different control methods during a severe voltage drop. It can be seen that the control method proposed in this invention can, to a certain extent, raise the grid connection point voltage during the fault period. After the grid voltage recovers, the peak grid connection point voltage is 1.157 pu using the traditional control method. Wind turbines may be disconnected from the grid due to excessive terminal voltage, which in turn triggers a series of cascading failures and is not conducive to the safe and stable operation of the wind power grid-connected system. However, the peak grid connection point voltage is 1.108 pu using the control method proposed in this invention. It can be seen that the control method proposed in this invention can effectively suppress transient overvoltages at the grid connection point after the fault is cleared.

[0089] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. The scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for improving the transient voltage support capability of a doubly-fed wind turbine generator system, characterized in that: The method comprises the following steps: Step S1: Obtain detailed parameters of the doubly-fed wind power grid-connected system; Step S2: Calculate the phase-locked loop phase error angle based on the detailed parameters, and analyze the impact of the phase-locked error angle on the electrical quantities of the doubly fed wind turbine; Step S3: calculating a current reference value of a doubly-fed wind turbine rotor-side converter taking into account phase jump during low voltage ride-through; Step S4: calculating a current reference value of the doubly-fed wind turbine rotor-side converter taking into account phase jump after grid voltage recovery; Step S5: Calculating the rotor-side converter voltage equation taking into account the phase jump; Step S6: designing a control logic strategy based on the acquired detailed parameters of the doubly-fed wind power grid-connected system and the calculated phase-lock error angle.

2. A method for improving the transient voltage support capability of a doubly-fed wind turbine generator system according to claim 1, characterized in that: The detailed parameters of the doubly-fed wind power grid-connected system obtained in step S1 specifically include: Grid connection point voltage U s , double-fed wind turbine stator output active power reference value P sref , actual value P s , double-fed wind turbine stator output reactive power reference value Q sref , actual value Q s , the maximum allowable current of the rotor-side converter of the doubly fed wind turbine , rated current of the rotor-side converter of the doubly fed wind turbine , reactive current proportional coefficient K , the grid connection point voltage output by the phase-locked loop d Axis component u dPLL 、 q Axis component u qPLL , rotor side resistance of doubly fed wind turbine R r ,inductance L r , magnetic flux leakage coefficient σ , the rotor current of the doubly fed wind turbine d Axis component 、 q Axis component , stator side inductance L s , the mutual inductance between the stator and the rotor L m , rotor rotation angular velocity ω r , synchronous angular velocity ω 1.

3. The method for improving the transient voltage support capability of a doubly-fed wind turbine generator system according to claim 2, characterized in that: The step S2 outputs the grid connection point voltage through the phase-locked loop d Axis component u dPLL 、 q Axis component u qPLL Calculate the phase-lock error angle. The specific formula is as follows: in, is the phase-lock error angle.

4. A method for improving the transient voltage support capability of a doubly-fed wind turbine generator system according to claim 3, characterized in that: The step S3 specifically includes: during the low voltage ride-through period, the active / reactive outer loop of the wind turbine rotor-side converter is disconnected, and the doubly-fed wind turbine generator set should be guaranteed to operate continuously without disconnecting from the grid within a certain voltage range, that is, without taking into account the phase jump. At this time, the current reference value of the inner loop can be directly given according to the traditional current reference value: in, For wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, For wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, is the maximum allowable current of the wind turbine rotor side converter, is the stator side inductance, is the mutual inductance between the stator and the rotor, is the synchronous angular velocity, is the grid connection point voltage, is the reactive current proportional coefficient, is the rated current of the doubly fed wind turbine rotor-side converter, Output current on the stator side of the fan Initial value of the axis component; when the doubly fed wind turbine generator system is off-grid, the reference value of the doubly fed wind turbine rotor-side converter current taking into account the phase jump during the low voltage ride-through period is as follows: in, Considering phase jump for wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, Considering phase jump for wind turbine rotor-side converter during low voltage ride-through Shaft current reference value, is the sine value of the phase-locking error angle, is the cosine value of the phase-lock error angle.

5. A method for improving the transient voltage support capability of a doubly-fed wind turbine generator system according to claim 4, characterized in that: The step S4 specifically includes: after the grid voltage is restored, the active / reactive outer loop of the wind turbine rotor-side converter is reconnected. At this time, the current reference value of the inner loop is given by the outer loop. Then, after the grid voltage is restored, the current reference value of the inner loop of the rotor-side converter is as follows: in, After the grid voltage is restored, the wind turbine rotor side converter Shaft current reference value, After the grid voltage is restored, the wind turbine rotor side converter Shaft current reference value, 、 are the active power outer loop PI control parameters, 、 are the reactive power outer loop PI control parameters, 、 are the reference value and actual value of the stator output active power of the doubly fed wind turbine, 、 are the reference value and actual value of the reactive power output of the doubly fed wind turbine stator respectively; when the reference value of the converter inner loop current cannot be directly given after the outer loop is connected, a compensation value is added on the basis of the inner loop current reference value, which is as follows: in, A wind turbine rotor-side converter that takes into account phase jumps after grid voltage recovery Shaft current reference value, A wind turbine rotor-side converter that takes into account phase jumps after grid voltage recovery Shaft current reference value.

6. A method for improving the transient voltage support capability of a doubly-fed wind turbine generator system according to claim 5, characterized in that: The step S5 specifically includes: after a short circuit fault occurs, the phase-locked loop phase angle is no longer equal to the actual grid voltage phase angle due to the phase-locked error. At this time, the rotation angular velocity output by the phase-locked loop is Synchronous angular velocity are no longer equal, the voltage equation of the doubly fed wind turbine rotor-side converter after taking into account the phase jump is: in, 、 The rotor voltage is 、 Axis component, 、 are the rotor side resistance and inductance, 、 The rotor current is 、 Axis component, is the rotor rotation angular velocity, is the angular velocity of the phase-locked loop output, is the magnetic flux leakage coefficient.

7. A method for improving the transient voltage support capability of a doubly-fed wind turbine generator system according to claim 6, characterized in that: In step S6, the control logic strategy is designed based on the obtained detailed parameters of the doubly fed wind power grid-connected system and the calculated phase-locked error angle, specifically including: when a short-circuit fault occurs, if the per-unit value of the grid-connected point voltage amplitude is less than 0.9, the control outer loop of the doubly fed wind turbine rotor-side converter is disconnected. At this time, if the phase-locked error angle is 0, the traditional low voltage ride-through control strategy is adopted. At this time, the rotor current reference values ​​are respectively 、 If the phase-locked error angle is not 0, the control strategy of the current reference value of the doubly fed wind turbine rotor side converter taking into account the phase jump is adopted. At this time, the rotor current reference values ​​are 、 ; When the short-circuit fault is cleared, the grid voltage begins to recover. If the per-unit value of the grid-connected voltage amplitude is greater than 0.9, the control outer loop of the doubly fed wind turbine rotor-side converter is reconnected. At this time, if the phase-locked error angle is 0, the control is terminated. At this time, the rotor current reference values ​​are 、 If the phase-locked error angle is not 0, a compensation control strategy is added to the inner loop current reference value. At this time, the rotor current reference value is added 、 ; At the same time, the rotation angular velocity term output by the phase-locked loop is used Replace the synchronous angular velocity term in the rotor-side converter voltage equation .

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