阅读说明：本技术 一种提高双馈风电场高电压穿越能力的无功控制方法 (Reactive power control method for improving high voltage ride through capability of double-fed wind power plant ) 是由 刘新宇 刘雪梅 王亚辉 樊要玲 李勇 顾波 张红涛 王继东 师永彪 刘延华 林政 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种提高双馈风电场高电压穿越能力的无功控制方法,包括：步骤一：列写出双馈风力发电机dq坐标系下感应发电机的数学模型；步骤二：根据双馈感应发电机在dq坐标系下的数学模型,找出电网运行时变频器加在转子上的外加电压与转子磁链之间的关系式和转子磁链与有功功率、无功功率的关系式；步骤三：根据转子磁链与外加控制电压及双馈感应发电机输出的有功功率、无功功率的关系式,建立双馈感应发电机转子磁链控制模型；步骤四：在双馈感应发电机转子磁链控制模型基础上,基于滑模变结构控制原理,建立双馈风力发电机转子磁链滑模变结构自适应控制率,实现对风电场中双馈风力发电机输出有功功率和无功功率的优化控制。(The invention discloses a reactive power control method for improving the high voltage ride through capability of a doubly-fed wind power plant, which comprises the following steps: the method comprises the following steps: writing a mathematical model of the induction generator under a dq coordinate system of the doubly-fed wind generator; step two: finding out a relational expression between an external voltage applied to a rotor by a frequency converter when a power grid operates and a rotor flux linkage and a relational expression between the rotor flux linkage and active power and reactive power according to a mathematical model of the doubly-fed induction generator under a dq coordinate system; step three: establishing a rotor flux linkage control model of the doubly-fed induction generator according to a relational expression of the rotor flux linkage, an external control voltage and active power and reactive power output by the doubly-fed induction generator; step four: on the basis of a rotor flux linkage control model of the doubly-fed induction generator, the self-adaptive control rate of the rotor flux linkage sliding mode variable structure of the doubly-fed wind driven generator is established based on the sliding mode variable structure control principle, and the optimal control of the output active power and the output reactive power of the doubly-fed wind driven generator in the wind power plant is realized.)

1. A reactive power control method for improving the high voltage ride through capability of a doubly-fed wind power plant is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps: writing a mathematical model of the induction generator under a dq coordinate system of the doubly-fed wind generator;

step two: finding out a relational expression between an external voltage applied to a rotor by a frequency converter when a power grid operates and a rotor flux linkage and a relational expression between the rotor flux linkage and active power and reactive power according to a mathematical model of the doubly-fed induction generator under a dq coordinate system;

step three: establishing a rotor flux linkage control model of the doubly-fed induction generator according to a relational expression of the rotor flux linkage, an external control voltage and active power and reactive power output by the doubly-fed induction generator;

step four: on the basis of a rotor flux linkage control model of the doubly-fed induction generator, the self-adaptive control rate of the rotor flux linkage sliding mode variable structure of the doubly-fed wind driven generator is established based on the sliding mode variable structure control principle, and the optimal control of the output active power and the output reactive power of the doubly-fed wind driven generator in the wind power plant is realized.

2. The reactive power control method for improving the high voltage ride through capability of the doubly-fed wind farm according to claim 1, characterized by comprising the following steps: the mathematical model of the induction generator under the dq coordinate system of the doubly-fed wind generator is as follows:

stator and rotor voltage equations:

stator and rotor flux linkage equations:

power output of stator terminal:

in the formula, L_s、L_rAnd L_mThe self inductance and mutual inductance of the stator and the rotor are respectively; r_s、R_rRespectively a stator resistor and a rotor resistor; omega₁And ω₂Synchronous speed and slip, respectively; u. of_dsStator voltage d-axis component u_qsStator voltage q-axis component, u_drRepresenting the d-axis component, u, of the rotor voltage_qrRepresenting a rotor voltage q-axis component; i.e. i_dsRepresenting the d-axis component, i, of the stator current_qsRepresenting stator current q-axis component, i_drRepresenting the d-axis component, i, of the rotor current_qrRepresenting a rotor current q-axis component;d-axis component of stator flux linkage,Stator flux q-axis componentD-axis component of rotor flux linkage,A rotor flux linkage q-axis component; p_sRepresenting active power, Q, of the stator_sAnd the sub-expression represents the stator reactive power.

3. The reactive power control method for improving the high voltage ride through capability of the doubly-fed wind farm according to claim 1, characterized by comprising the following steps: when the power grid voltage operates symmetrically, the stator is linked with the magnetic fluxOriented on the d-axis of the synchronously rotating d-and q-coordinate systems, the flux linkages on the d-and q-axes are respectively:the induced electromotive force of the DFIG is approximately equal to the stator voltage, i.e. u_ds＝0，u_qs＝u_s；u_sIs the amplitude of the vector of the stator voltage, u after the stator is incorporated into the ideal grid_sThe amplitude is equal to the amplitude of the grid voltage; the resistance of the stator winding is far less than the reactance of the stator winding, and the stator flux linkage and the current equation are obtained at the moment:

when a high-voltage fault occurs to a power grid, the DFIG is in an unstable operation state, the stator voltage and the stator flux linkage of the DFIG are not constant, so that the change of the flux linkage cannot be ignored during the analysis of transient operation of the DFIG, the flux linkage change cannot be mutated, and the stator flux linkage change enables the stator exciting current to change along with the change of the stator flux linkage; in this case, in formula (4)Substituting equation (5) for the rotor flux linkage equation of equation (2) and the rotor voltage equation of equation (1) to obtain:

the formula (5) is substituted into the rotor flux linkage equations of the formula (3) and the formula (2) to obtain an active power equation and a reactive power equation:

during voltage sudden rise caused by grid failure, according to the equations (6) and (7), the reactive power generated by the doubly-fed wind farm depends on the q-axis component of the rotor flux linkage, and the q-axis component of the rotor flux linkage is controlled by the q-axis excitation voltage with the time constant of The derivative of the d-axis component of the rotor flux linkage is represented,the derivative of the q-axis component of the rotor flux linkage is represented.

4. The reactive power control method for improving the high voltage ride through capability of the doubly-fed wind farm according to claim 1, characterized by comprising the following steps: the third step specifically comprises: writing the applied voltage and flux linkage of the DFIG rotor into the following state space equation form

In the formula (I), the compound is shown in the specification,in order to be a state variable, the state variable,for control input, F represents a disturbance caused by a grid fault and has

Where F represents the disturbance caused by the grid fault,in order to be a state variable, the state variable,for control input, Z₁₁Representing d-axis flux linkage psi of rotor_dr，Z₂₁Representing rotor q-axis flux linkage psi_qr；Z₁₀Representing rotor d-axis flux linkage control signal u_dr，Z₂₀Representing rotor q-axis flux linkage control signal u_qr；f₁A component one representing a disturbance caused by a grid fault; f. of₂A second component representing a disturbance caused by a grid fault;

rank[B F]＝rank[B]＝2 (9)

according to the formula (9), the sliding mode of the double-fed wind power generation system meets the requirement of no external interference;

order toThe q-axis flux linkage error state equation for DFIG is shown below:

in the formula (I), the compound is shown in the specification,representing a generalized disturbance of the power system.

5. The reactive power control method for improving the high voltage ride through capability of the doubly-fed wind farm according to claim 1, characterized by comprising the following steps: the fourth step specifically comprises: integrating sliding mode surfaces:

in the formula k_pd、k_idAre respectively proportional, integral coefficient, and k_pd、k_idAre all larger than zero; the proportional term is used for accelerating the dynamic tracking response of the system, and the integral term is used for eliminating the steady-state error of the system; therefore, k is changed on the PI integral sliding mode hypersurface_pd、k_idThe value of (a) can change the dynamic characteristics of the sliding mode surface; e.g. of the type_dRepresenting d-axis flux linkage error;represents the p/q power of the d-axis flux linkage error;

if the generalized perturbation term | F_d|<k_d，k_dIs constant and is larger than zero, and the following reactive power control law of the doubly-fed wind driven generator is obtained

The q-axis flux linkage error e of the DFIG can be converged to zero within a limited time, and the system is robust and stable;

wherein, the gain is switched eta'_qThe expression is as follows:

in the formula eta_qIndicating the switching gain, Q, of the system during normal operation₀Representing a given value of reactive power, Q representing the actual reactive power, lambda_qIs a set constant and 0 < lambda_q＜1；A given value representing a rotor q-axis flux linkage; k is a radical of_iqRepresents a scaling factor;represents the p/q power of the q-axis flux linkage error; eta 'of'_qRepresents the fast switching gain; s_qA q-axis mode surface representing a rotor flux linkage;

when the system has instantaneous high voltage, the control gain is switched toThe double-fed wind power plant can quickly absorb redundant reactive power by rapid increase, so that the system voltage can be quickly recovered to a given value; when the system works normally, the switching control gain is recovered to the conventional set value eta_q。

Technical Field

The invention belongs to the field of intelligent power grids, can be applied to the fields of new energy power generation, new energy grid connection and the like, and particularly relates to a reactive power control method for improving the high voltage ride through capability of a double-fed wind power plant.

Background

Most of large wind power plants in China are located in remote areas, are far away from a load center of a power system, and have typical weak grid characteristics. The high-proportion wind power plant is switched into the weak grid-connected operation, so that the contradiction between the wind power grid-connection and the safe and stable operation of the power system is more and more prominent. Therefore, strict wind power grid-connection related specifications are developed in the major wind power countries such as the United states and China in succession, and the wind power plants are required to have low voltage ride through capability and also to absorb certain dynamic reactive power rapidly so as to enhance the high voltage ride through capability during the period of grid fault and voltage fluctuation.

Disclosure of Invention

In order to solve the problems, a reactive power control method for improving the high voltage ride through capability of the doubly-fed wind power plant is provided.

The object of the invention is achieved in the following way:

a reactive power control method for improving the high voltage ride through capability of a doubly-fed wind power plant is characterized by comprising the following steps: the method comprises the following steps:

the method comprises the following steps: writing a mathematical model of the induction generator under a dq coordinate system of the doubly-fed wind generator;

step two: finding out a relational expression between an external voltage applied to a rotor by a frequency converter when a power grid operates and a rotor flux linkage and a relational expression between the rotor flux linkage and active power and reactive power according to a mathematical model of the doubly-fed induction generator under a dq coordinate system;

step three: establishing a rotor flux linkage control model of the doubly-fed induction generator according to a relational expression of the rotor flux linkage, an external control voltage and active power and reactive power output by the doubly-fed induction generator;

step four: on the basis of a rotor flux linkage control model of the doubly-fed induction generator, the self-adaptive control rate of the rotor flux linkage sliding mode variable structure of the doubly-fed wind driven generator is established based on the sliding mode variable structure control principle, and the optimal control of the output active power and the output reactive power of the doubly-fed wind driven generator in the wind power plant is realized.

The mathematical model of the induction generator under the dq coordinate system of the doubly-fed wind generator is as follows:

stator and rotor voltage equations:

stator and rotor flux linkage equations:

power output of stator terminal:

in the formula, L_s、L_rAnd L_mThe self inductance and mutual inductance of the stator and the rotor are respectively; r_s、R_rRespectively a stator resistor and a rotor resistor; omega₁And ω₂Synchronous speed and slip, respectively; u. of_dsStator voltage d-axis component u_qsStator voltage q-axis component, u_drRepresenting the d-axis component, u, of the rotor voltage_qrRepresenting a rotor voltage q-axis component; i.e. i_dsRepresenting the d-axis component, i, of the stator current_qsRepresenting stator current q-axis component, i_drRepresenting the d-axis component, i, of the rotor current_qrRepresenting a rotor current q-axis component;d-axis component of stator flux linkage,Stator flux q-axis componentD-axis component of rotor flux linkage,A rotor flux linkage q-axis component; p_sRepresenting active power, Q, of the stator_sAnd the sub-expression represents the stator reactive power.

When the power grid voltage operates symmetrically, the stator is linked with the magnetic fluxOriented on the d-axis of the synchronously rotating d-and q-coordinate systems, the flux linkages on the d-and q-axes are respectively:the induced electromotive force of the DFIG is approximately equal to the stator voltage, i.e. u_ds＝0，u_qs＝u_s；u_sIs the amplitude of the vector of the stator voltage, u after the stator is incorporated into the ideal grid_sThe amplitude is equal to the amplitude of the grid voltage; the resistance of the stator winding is far less than the reactance of the stator winding, and the stator flux linkage and the current equation are obtained at the moment:

when a high-voltage fault occurs to a power grid, the DFIG is in an unstable operation state, the stator voltage and the stator flux linkage of the DFIG are not constant, so that the change of the flux linkage cannot be ignored during the analysis of transient operation of the DFIG, the flux linkage change cannot be mutated, and the stator flux linkage change enables the stator exciting current to change along with the change of the stator flux linkage; in this case, in formula (4)Substituting equation (5) for the rotor flux linkage equation of equation (2) and the rotor voltage equation of equation (1) to obtain:

the formula (5) is substituted into the rotor flux linkage equations of the formula (3) and the formula (2) to obtain an active power equation and a reactive power equation:

during voltage sudden rise caused by grid failure, according to the equations (6) and (7), the reactive power generated by the doubly-fed wind farm depends on the q-axis component of the rotor flux linkage, and the q-axis component of the rotor flux linkage is controlled by the q-axis excitation voltage with the time constant of The derivative of the d-axis component of the rotor flux linkage is represented,the derivative of the q-axis component of the rotor flux linkage is represented.

The third step specifically comprises: writing the applied voltage and flux linkage of the DFIG rotor into the following state space equation form

In the formula (I), the compound is shown in the specification,in order to be a state variable, the state variable,for control input, F represents a disturbance caused by a grid fault and has

Where F represents the disturbance caused by the grid fault,in order to be a state variable, the state variable,for control input, Z₁₁Representing d-axis flux linkage psi of rotor_dr，Z₂₁Representing rotor q-axis flux linkage psi_qr；Z₁₀Representing rotor d-axis flux linkage control signal u_dr，Z₂₀Representing rotor q-axis flux linkage control signal u_qr；f₁A component one representing a disturbance caused by a grid fault; f. of₂A second component representing a disturbance caused by a grid fault;

rank[B F]＝rank[B]＝2 (9)

according to the formula (9), the sliding mode of the double-fed wind power generation system meets the requirement of no external interference;

order toThe q-axis flux linkage error state equation for DFIG is shown below:

in the formula (I), the compound is shown in the specification,representing a generalized disturbance of the power system.

The fourth step specifically comprises: integrating sliding mode surfaces:

in the formula k_pd、k_idAre respectively proportional, integral coefficient, and k_pd、k_idAre all larger than zero; the proportional term is used for accelerating the dynamic tracking response of the system, and the integral term is used for eliminating the steady-state error of the system; therefore, k is changed on the PI integral sliding mode hypersurface_pd、k_idThe value of (a) can change the dynamic characteristics of the sliding mode surface; e.g. of the type_dRepresenting d-axis flux linkage error;represents the p/q power of the d-axis flux linkage error;

if the generalized perturbation term | F_d|<k_d，k_dIs constant and greater than zero, resulting in a double feed as followsThe reactive power control law of the wind driven generator is

The q-axis flux linkage error e of the DFIG can be converged to zero within a limited time, and the system is robust and stable;

wherein, the gain is switched eta'_qThe expression is as follows:

in the formula eta_qIndicating the switching gain, Q, of the system during normal operation₀Representing a given value of reactive power, Q representing the actual reactive power, lambda_qIs a set constant and 0 < lambda_q＜1；A given value representing a rotor q-axis flux linkage; k is a radical of_iqRepresents a scaling factor;represents the p/q power of the q-axis flux linkage error; eta 'of'_qRepresents the fast switching gain; s_qA q-axis mode surface representing a rotor flux linkage;

when the system has instantaneous high voltage, the control gain is switched toThe double-fed wind power plant can quickly absorb redundant reactive power by rapid increase, so that the system voltage can be quickly recovered to a given value; when the system works normally, the switching control gain is recovered to the conventional set value eta_q。

Compared with the prior art, the method for improving the voltage ride through control is superior to the traditional PI control method, and the optimization control of the grid-connected high voltage ride through capability of the double-fed wind power plant is realized.

Drawings

FIG. 1 is a diagram of the relationship between the applied voltage and the flux linkage of a DFIG rotor.

Fig. 2 is a system control flow chart.

Fig. 3 is a conventional PI control common bus voltage response curve.

FIG. 4 is a common bus voltage response curve for an improved control strategy.

Fig. 5 is a conventional PI control rotor current response curve.

FIG. 6 is a robust sliding-mode controlled rotor current response curve that accounts for wake effects.

Fig. 7 is a conventional PI control reactive power response curve.

FIG. 8 is a joint additive control reactive power response curve that accounts for wake effects.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same technical meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and it should be further understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, devices, components, and/or combinations thereof.

In the present invention, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only terms of relationships determined for convenience of describing structural relationships of the parts or elements of the present invention, and are not intended to refer to any parts or elements of the present invention, and are not to be construed as limiting the present invention.

In the present invention, terms such as "fixedly connected", "connected", and the like are to be understood in a broad sense, and mean either a fixed connection or an integrally connected or detachable connection; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be determined according to specific situations by persons skilled in the relevant scientific or technical field, and are not to be construed as limiting the present invention.

A reactive power control method for improving the high voltage ride through capability of a doubly-fed wind power plant comprises the following steps:

the method comprises the following steps: writing a mathematical model of the induction generator under a dq coordinate system of the doubly-fed wind generator;

step two: finding out a relational expression between an external voltage applied to a rotor by a frequency converter when a power grid operates and a rotor flux linkage and a relational expression between the rotor flux linkage and active power and reactive power according to a mathematical model of the doubly-fed induction generator under a dq coordinate system;

step three: establishing a rotor flux linkage control model of the doubly-fed induction generator according to a relational expression of the rotor flux linkage, an external control voltage and active power and reactive power output by the doubly-fed induction generator;

step four: on the basis of a rotor flux linkage control model of the doubly-fed induction generator, the self-adaptive control rate of the rotor flux linkage sliding mode variable structure of the doubly-fed wind driven generator is established based on the sliding mode variable structure control principle, and the optimal control of the output active power and the output reactive power of the doubly-fed wind driven generator in the wind power plant is realized.

Equivalent mathematical model of DFIG in accordance with motor convention under synchronous rotation d, q coordinate system:

stator and rotor voltage equations:

stator and rotor flux linkage equations:

power output of stator terminal:

in the formula, L_s、L_rAnd L_mThe self inductance and mutual inductance of the stator and the rotor are respectively; r_s、R_rRespectively a stator resistor and a rotor resistor; omega₁And ω₂Synchronous speed and slip, respectively; u. of_ds、u_qsu_dr、u_qrStator and rotor excitation voltages respectively; i.e. i_ds、i_qs、i_dr、i_qrStator and rotor exciting currents respectively;respectively carrying out stator and rotor excitation; p_s、Q_sThe active power and the reactive power of the stator are respectively.

When the power grid voltage operates symmetrically, the stator is linked with the magnetic fluxOriented on the d-axis of the synchronously rotating d-and q-coordinate systems, the flux linkages on the d-and q-axes are respectively:the induced electromotive force of the DFIG is approximately equal to the stator voltage, i.e. u_ds＝0，u_qs＝u_s(ii) a Is the amplitude of the vector of the stator voltage, u after the stator is incorporated into the ideal grid_sAnd the amplitude is equal to the amplitude of the power grid voltage. The resistance of the stator winding is much smaller than the reactance of the stator winding, and the influence of the stator resistance can be ignored. The stator flux linkage and current equations are now obtained:

when a high-voltage fault occurs to a power grid, the DFIG is in an unstable operation state, the stator voltage and the stator flux linkage of the DFIG are not constant, therefore, the change of the flux linkage cannot be ignored during the analysis of transient operation of the DFIG, the flux linkage change cannot be mutated, and the stator excitation current is changed along with the stator flux linkage change. In this case, in formula (4)In consideration of the above, equation (5) is substituted for the rotor flux linkage equation of equation (2) and the rotor voltage equation of equation (1) to obtain:

in order to highlight the main problems of research, the equation (5) is substituted into the rotor flux linkage equations (3) and (2) to obtain an active power equation and a reactive power equation:

during voltage sudden rise caused by grid failure, according to the equations (6) and (7), the reactive power generated by the doubly-fed wind farm depends on the q-axis component of the rotor flux linkage, and the q-axis component of the rotor flux linkage is controlled by the q-axis excitation voltage with the time constant ofThe time is generally 8-15 ms; therefore, the speed of reactive power regulation of the doubly-fed wind power plant belongs to millisecond-level rapid control and is almost equal to the reactive power compensation speed of the static reactive power compensator.

According to the equation (6), the structure diagram of the relationship between the applied voltage of the inverter to the rotor and the rotor flux linkage in the power generation operation is shown in fig. 1.

For this purpose, equation (6) is written in the form of the following state space equation

In the formula (I), the compound is shown in the specification,in order to be a state variable, the state variable,for control input, F represents a disturbance caused by a grid fault and has

Where F represents the disturbance caused by the grid fault,in order to be a state variable, the state variable,for control input, Z₁₁Representing d-axis flux linkage psi of rotor_dr，Z₂₁Representing rotor q-axis flux linkage psi_qr。Z₁₀Representing rotor d-axis flux linkage control signal u_dr，Z₂₀Representing rotor q-axis flux linkage control signal u_qr。

Easy certificate

rank[B F]＝rank[B]＝2 (9)

According to the formula (9), the sliding mode of the double-fed wind power generation system meets the requirement of being free from external interference. Therefore, a proper sliding mode controller is designed, so that the doubly-fed wind power generator set has complete robustness to disturbance caused by grid faults, and the sliding mode of the doubly-fed wind power generator set is not influenced by the grid faults.

Based on the above analysis, the DFIG rotor q-axis flux linkage controller is first designed herein. Order toThe q-axis flux linkage error state equation for DFIG is shown below:

in the formula (I), the compound is shown in the specification,representing a generalized disturbance of the power system.

In view of the above, the following integral slip form surfaces are proposed herein:

in the formula k_pd、k_idAre respectively proportional, integral coefficient, and k_pd、k_idAre all greater than zero. The proportional term is used for accelerating the dynamic tracking response of the system, and the integral term is used for eliminating the steady-state error of the system. Therefore, k is changed on the PI integral sliding mode hypersurface_pd、k_idThe value of (a) may change the dynamic characteristics of the slip-form surfaces.

According to the integral terminal sliding mode surface provided by the invention, if the generalized disturbance term | F_d|<k_d，k_dIs constant and is larger than zero, and the following reactive power control law of the doubly-fed wind driven generator is obtained

The q-axis flux linkage error e of the DFIG can be converged to zero in a limited time, and the system is robust and stable.

Wherein, the gain is switched eta'_qThe expression is as follows:

in the formula eta_qIndicating the switching gain, Q, of the system during normal operation₀Representing a given value of reactive power, Q representing the actual reactive power, lambda_qIs a set constant and 0 < lambda_q＜1。

When the system has instantaneous high voltage, the control gain is switched toAnd the double-fed wind power plant can quickly absorb redundant reactive power by rapid increase, so that the system voltage can be quickly recovered to a given value. When the system works normally, the switching control gain is recovered to the conventional set value eta_q。

The simulation results are shown in fig. 3-8.

Fig. 3 and 4 are dynamic response curves of the common bus voltage when the conventional PI control strategy and the joint additional control strategy are adopted, respectively. As can be seen from fig. 3, when the conventional PI control strategy is adopted, during a system fault, the burst increment of the common bus voltage is 0.47pu, the high voltage duration is 500ms, and after the fault disappears, the bus voltage returns to normal again. Fig. 4 shows that when a high-voltage fault is triggered by using the joint additional control strategy considering the wake effect, the sudden increment of the common bus voltage is 0.25pu, and the bus voltage returns to normal again after the fault disappears.

Fig. 5 and 6 are rotor excitation current dynamic response curves when a conventional PI control strategy and a joint additional control strategy considering wake effect are adopted, respectively. As can be seen, under the conventional control strategy, after a high-voltage fault is triggered, the DFIG rotor current hardly changes greatly. After the combined additional control strategy is adopted, the rotor current of the DFIG is rapidly increased to 1.5 times of the original rotor current during the fault occurrence period, so that the DFIG can rapidly generate reactive power, and sudden rise of the voltage of the common bus is effectively inhibited.

Fig. 7 and 8 are dynamic response curves of the reactive power of the DFIG when the conventional PI control strategy and the joint additional control strategy considering the wake effect are adopted, respectively. As can be seen from the figure, by adopting a conventional PI control strategy, the reactive power output by the double-fed fan is in violent oscillation during the fault period, and the reactive power tends to be stable after the fault is eliminated. And a combined additional control strategy is adopted, the double-fed fan can rapidly output reactive power reaching-2.41 pu during the fault period, and the high voltage is subjected to inhibition regulation.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.