A rotor transient current-based rotor voltage compensation method for a doubly-fed wind turbine generator

Abstract

The application discloses a rotor voltage compensation method for a doubly-fed wind turbine based on rotor transient current, and the method comprises the following steps: step 1, during the low-voltage ride-through of the doubly-fed wind turbine, short-circuit fault analysis is carried out on the doubly-fed induction generator (DFIG) in different rotating coordinate systems; step 2, the rotor current composition and the equivalent circuit of the rotor winding in each coordinate system are obtained, and the equation relationship between the rotor current compositions in different coordinate systems is analyzed; and step 3, the steady-state rotor current and the transient-state rotor current in the rotor current are separated through the Park transformation, the compensation value of the rotor voltage is obtained by combining the transient-state rotor current and the rotor winding loop, the increase of the rotor current is inhibited, and the influence of the compensated rotor voltage on the stator flux decay is considered; the compensation value of the rotor voltage which needs to be compensated in the dq rotating coordinate system is obtained through the rotor winding loop in the transient process, so that the rotor current is controlled within the safety threshold, and the low-voltage ride-through range of the doubly-fed wind turbine is expanded.

Description

Technical Field

[0001] This invention relates to the field of new energy power generation management, and in particular to a method for rotor voltage compensation of doubly fed wind turbine generators based on rotor transient current. Background Technology

[0002] With the large-scale grid connection of new energy power generation, doubly-fed induction generators (DFIGs) are increasingly accounting for a significant portion of the power system. DFIGs achieve constant frequency and voltage control on the stator side through rotor control, enabling variable speed and constant frequency control. Since the stator is directly connected to the AC grid, it is most affected by the AC grid voltage. During AC grid voltage dips, on the one hand, the low voltage level makes power transmission to the wind turbine difficult; on the other hand, the free component generated by the stator flux during the voltage dip causes the rotor current to exceed its limit. Currently, the most commonly used low-voltage ride-through methods include fast short-circuit protection devices and DC-side capacitor energy storage, but these undoubtedly increase the power generation cost of DFIGs. Therefore, how to extend the low-voltage ride-through range and reduce power generation costs through the wind turbine's own software control is a key issue for efficient operation under high wind turbine penetration rates. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a rotor voltage compensation method for doubly-fed wind turbine generators based on rotor transient current, comprising the following steps:

[0004] Obtain the rotor current during the low-voltage ride-through process of the doubly-fed wind turbine and construct the rotor winding circuit;

[0005] Based on the rotor winding circuit, the transient rotor current is obtained to obtain the compensation value of the rotor voltage. The compensation value is used to suppress the increase of rotor current and compensate for the rotor voltage's effect on stator flux attenuation.

[0006] Preferably, during the low-voltage ride-through process of the doubly fed wind turbine, short-circuit fault analysis is performed on the DFIG in different rotating coordinate systems to obtain the rotor current.

[0007] Preferably, in the process of short-circuit fault analysis using DFIG, the complex vector form of the mathematical model of DFIG is:

[0008]

[0009] Among them, U s U r Representing the stator and rotor voltages respectively, ψ s ψ r Representing the stator and rotor flux linkages, I s I r Represent the stator and rotor currents, respectively, Rs L s R represents the stator resistance and inductance, respectively. r L r ω represents the rotor resistance and inductance, respectively. slip =ω e -ω r ω e ω r L represents the synchronous speed and the generator speed, respectively. m This indicates the mutual inductance between the stator and rotor.

[0010] Preferably, during the short-circuit fault analysis using DFIG, based on the degree of stator voltage drop and the characteristic that stator flux linkage cannot change abruptly, the forced component and free component in the stator flux linkage during low-voltage ride-through are obtained, and the rotor current under the current inner loop control of the doubly fed wind turbine converter is calculated.

[0011] Preferably, in the process of calculating the first rotor current under the current inner loop control of the doubly-fed wind turbine converter, the rotor current is expressed as:

[0012]

[0013] In the formula: i rd i rq The d-axis and q-axis components represent the rotor current of a doubly-fed induction generator (DFIG). rt =L r -L 2 m / L s ,L rt Let k be the equivalent inductance of the rotor circuit in the rotor coordinate system. p With k i Let I be the proportional and derivative constants of the PI controller, respectively. rdref I rqref e is the dq-axis reference value for the rotor current. nd e nq Let τ be the dq-axis component of the rotor's free transient electromotive force. s =L s / R s , where is the stator time constant.

[0014] Preferably, during the construction of the rotor winding circuit, the rotor current in the synchronous rotating coordinate system is obtained by analyzing the composition of the rotor current, and the rotor winding circuit is constructed, wherein the rotor current is expressed as:

[0015]

[0016] In the formula, i r rc1The frequency sω is determined by the periodic components of the rotor voltage and back electromotive force. e AC steady-state components, i r rc2 Is with τ s The time constant decays in relation to the transient component of the back electromotive force, and is expressed in terms of τ. r The frequency of the time constant decay is -ω r The communication component, i r rn Representing rotor current in terms of τ r The DC current component decaying with a time constant, where τ r =L rt / R r , where is the rotor time constant.

[0017] The rotor current in the synchronous rotating coordinate system is expressed as:

[0018] i rd =i rc1d +i rc2d +i rnd

[0019] i rq =i rc1q +i c2q +i rnq

[0020] In the formula, i rc1d For rotor current pair k i i rdref The forced response, whose value is i rdref i, that is, the rotor current reference value; rc2d Is with τ s The transient component of back electromotive force e decaying with a time constant nd Related, and with τ r The frequency of the time constant decay is -ω e The exchange component; i rnd This is the natural response of the rotor d-axis current, which is related to the current instantaneously before and after a fault in the rotor circuit, and is expressed as τ. r The alternating current component with a time constant decay.

[0021] Preferably, in the process of constructing the rotor winding circuit, based on the rotor current in the synchronous rotating coordinate system, and according to the complex form of the vector of the DFIG mathematical model, coordinate transformation is performed to obtain the rotor winding circuit in the rotor coordinate system, wherein the rotor winding circuit is a circuit composed of rotor voltage, rotor back electromotive force, rotor resistance and inductance.

[0022] Preferably, in the process of obtaining the transient rotor current of the rotor current, the steady-state rotor current and the transient rotor current in the synchronous rotating coordinate system are separated by Park transformation, and the transient rotor current is combined with the rotor winding circuit to generate a compensation value.

[0023] Preferably, in the process of obtaining the compensation value, the compensation value is expressed as:

[0024]

[0025] Where, Δu rn Represented as the compensation value for the rotor voltage, i rn This represents the rotor transient current in the rotor coordinate system. Since the angular velocity of the rotor transient voltage is -ω... r The reactance value in the rotor circuit is -ω r L rt .

[0026] Preferably, the doubly-fed wind turbine rotor voltage compensation system for implementing the doubly-fed wind turbine rotor voltage compensation method includes:

[0027] The data acquisition module is used to acquire the rotor current during the low-voltage ride-through process of the doubly-fed wind turbine.

[0028] The rotor circuit construction module is used to construct rotor winding circuits;

[0029] The compensation module is used to obtain the compensation value of the rotor voltage based on the rotor winding circuit by acquiring the transient rotor current. The compensation value is used to suppress the increase of rotor current and suppress the attenuation of stator flux linkage.

[0030] The present invention discloses the following technical effects:

[0031] This invention employs additional rotor voltage control during the low-voltage ride-through process of a doubly-fed induction generator (DFIG) wind turbine. By increasing the rotor voltage, the increase in rotor current is suppressed. Given a reference value for rotor current, the steady-state rotor current and transient rotor current are separated. The compensation value of the rotor voltage that needs to be compensated in the dq rotating coordinate system is obtained through the rotor winding circuit under the transient process, thereby controlling the rotor current within a safe threshold and expanding the low-voltage ride-through range of the DFIG wind turbine. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a flowchart illustrating the method described in this invention;

[0034] Figure 2 This is a simulation topology diagram of the doubly fed wind turbine generator described in this invention;

[0035] Figure 3 This is a control block diagram of rotor voltage compensation based on rotor transient current as described in this invention;

[0036] Figure 4 This is the equivalent circuit of the rotor winding before the fault as described in this invention;

[0037] Figure 5 This is the equivalent circuit of the rotor winding after the fault as described in this invention;

[0038] Figure 6 This is a vector diagram illustrating the effect of rotor transient current on stator transient flux linkage as described in this invention.

[0039] Figure 7 This is a schematic diagram illustrating the AC power grid voltage drop situation described in this invention;

[0040] Figure 8 The figure shows the simulation results of the traditional vector control method described in this invention.

[0041] Figure 9 The figure shows the simulation results obtained using the method described in this invention. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0043] like Figure 1-9 As shown, Figure 1 This is a flowchart of the rotor voltage compensation system and method based on rotor transient current for a doubly-fed wind turbine according to an embodiment of the present invention, as shown below. Figure 1 As shown, it includes the following steps:

[0044] Step 1: During the low voltage ride-through process of the doubly fed wind turbine, short-circuit fault analysis is performed on the DFIG in different rotating coordinate systems.

[0045] Step 2: Obtain the rotor current composition and equivalent circuit of the rotor winding in each coordinate system. Analyze the equational relationships between the rotor current compositions in different coordinate systems.

[0046] Step 3: Separate the steady-state rotor current from the transient rotor current through Parker transformation, and combine the transient rotor current with the rotor winding circuit to obtain the compensation value of the rotor voltage, suppress the increase of rotor current, and consider the effect of the compensated rotor voltage on the stator flux attenuation.

[0047] In step 1: The equivalent circuit of the DFIG in the synchronous coordinate system is the basis for studying the transient response of the wind turbine stator and rotor under external grid voltage drops. The rotor-side parameters of the DFIG are reduced to the stator side, and following motor conventions, the complex vector form of the mathematical model of the DFIG can be expressed as:

[0048]

[0049] In the formula: U s U r Representing the stator and rotor voltages respectively, ψ s ψ r Representing the stator and rotor flux linkages, I s I r Represent the stator and rotor currents, respectively, R s L s R represents the stator resistance and inductance, respectively. r L r ω represents the rotor resistance and inductance, respectively. slip =ω e -ω r ω e ω r L represents the synchronous speed and the generator speed, respectively. m This indicates the mutual inductance between the stator and rotor.

[0050] By performing coordinate transformation on the complex vector form of the DFIG mathematical model, we can obtain that the rotor winding circuit in the rotor coordinate system consists of rotor voltage, rotor back electromotive force, and rotor resistance R. r The sum is L rt A circuit composed of inductors, such as Figure 4 As shown.

[0051] The equivalent circuit of the rotor winding in the rotor coordinate system can be obtained as follows: Figure 4 As shown, the superscript "r" indicates that the expression is in the rotor coordinate system, and the subscript "0" indicates that the variable is in the state before the power grid symmetrical fault.

[0052] Based on the degree of stator voltage drop and the characteristic that stator flux linkage cannot change abruptly, we can conclude that:

[0053] During low-voltage ride-through, the stator flux linkage contains forced and free components, which generate forced and free back electromotive forces in the rotor winding circuit, respectively.

[0054] The stator flux linkage contains forced and free components, which generate forced and free back electromotive forces in the rotor winding circuit, respectively.

[0055] The rotor current of a doubly-fed wind turbine converter under the current inner loop control can be expressed as:

[0056]

[0057] In the formula: i rd i rq The d-axis and q-axis components represent the rotor current of a doubly-fed induction generator (DFIG). rt =L r -L 2 m / L s ,L rt Let k be the equivalent inductance of the rotor circuit in the rotor coordinate system. p With k i Let I be the proportional and derivative constants of the PI controller, respectively. rdref ,I rqref e is the dq-axis reference value for the rotor current. nd e nq Let τ be the dq-axis component of the rotor's free transient electromotive force. s =L s / R s , where is the stator time constant. Therefore, the dynamic equation for the rotor current under rotor-side converter control can be obtained as follows:

[0058]

[0059] In step 2: Before and after the fault, the change in stator flux linkage generates a transient back electromotive force in the rotor winding circuit. Where e f n For steady-state back electromotive force, e r n This is the transient back electromotive force.

[0060] Circuit theory analysis reveals that the steady-state component of the rotor voltage, together with the steady-state back electromotive force (EMF), forms the steady-state AC component. The presence of the transient back EMF generates a large transient rotor current in the rotor winding circuit, which needs to be eliminated. Furthermore, since the rotor winding circuit contains inductive elements, the rotor current cannot undergo abrupt changes, thus generating a decaying DC component in the rotor coordinate system. Analyzing the rotor current composition in different coordinate systems yields their equations, specifically including: During low-voltage ride-through, the rotor current composition in the rotor rotating coordinate system is as follows:

[0061]

[0062] i r rc1 The frequency sω is determined by the periodic components of the rotor voltage and back electromotive force. e AC steady-state components, i r rc2 Is with τ s The time constant decays in relation to the transient component of the back electromotive force, and is expressed in terms of τ. r The frequency of the time constant decay is -ω r The exchange component, where τ r =L rt / R r After a momentary voltage drop in the mains, the current in the rotor circuit cannot change abruptly due to the presence of the rotor's instantaneous inductance. Therefore, the rotor current can be calculated as follows: With τ r The DC current component that decays with a time constant.

[0063] By solving the dynamic differential equation of the rotor current, the rotor current configuration in the synchronous rotating coordinate system can be obtained as follows:

[0064] i rd =i rc1d +i rc2d +i rnd

[0065] i rq =i rc1q +i c2q +i rnq

[0066] i rc1d For rotor current pair k i i rdref The forced response, whose value is i rdref This refers to the rotor current reference value. rc2d Is with τ s The transient component of back electromotive force e decaying with a time constant nd Related, and with τ r The frequency of the time constant decay is -ωe The amount of communication. rnd This is the natural response of the rotor d-axis current, which is related to the current instantaneously before and after a fault in the rotor circuit, and is expressed as τ. r The alternating current component with a time constant decay.

[0067] i re1q For rotor current pair k i i rqref The forced response, whose value is i rqref This refers to the rotor current reference value. rc2q Is with τ s The transient component of the back electromotive force e with time constant decay nq Related, and with τ s The frequency of the time constant decay is -ω e The amount of communication. rnq This is the natural response of the rotor q-axis current, which is related to the current instantaneously before and after a fault in the rotor circuit, and is expressed as τ. s The time constant decays the AC current component. This shows that the rotor current components obtained in different coordinate systems are in one-to-one correspondence, and that the rotor current components under rotor-side converter control contain reference values ​​for the rotor current dq axis.

[0068] In step 3: the steady-state rotor current and transient rotor current are separated through Parker transformation, and the transient rotor current is combined with the rotor winding circuit to obtain the compensation value of the rotor voltage, suppressing the increase of rotor current, and considering the effect of the compensated rotor voltage on stator flux attenuation. Specifically, this includes:

[0069] By setting corresponding rotor current dq-axis reference values ​​for different AC voltage drop levels, the rotor transient current component in the dq coordinate system can be obtained during low-voltage ride-through. The rotor transient current in the rotor coordinate system is obtained through Park transform, and combined with the rotor winding circuit, the rotor voltage requiring compensation can be obtained. This can be expressed in the frequency domain as follows:

[0070]

[0071] In the formula: Δu m Represented as the rotor voltage that needs to be compensated, i rn This represents the rotor transient current in the rotor coordinate system. The compensation value of the rotor voltage dq axis under rotor-side converter control can be obtained through the inverse Park transform. Compensation of the rotor transient voltage suppresses the increase in rotor current. Due to the presence of inductance parameters, the process of calculating the transient voltage can be separated. The response between the rotor transient current and the inductance can be filtered and differentiated using a high-pass filter, as shown in the following process... Figure 3 As shown, this step allows for a relatively accurate determination of the required rotor transient voltage value for compensation.

[0072] Considering only the influence between transient stator flux linkage and transient rotor current, we can obtain:

[0073]

[0074] In the formula: ψ snd ,ψ snq τ represents the value of the stator transient flux linkage on the dq axis. rs τ represents the effect of rotor transient current on stator flux linkage. rs =R s L m / L s ,I rnd with I rnq The transient current of the rotor dq axis has the following vector states for each component: Figure 5 As shown, u rn Let Δu be the rotor compensation voltage. rn / e r n =P can be obtained as follows:

[0075]

[0076] The characteristic root of the stator transient flux linkage is: λ 1，2 =-(σ s +k)±jω s The stator flux linkage attenuation coefficient is approximately σ. st =R s / L s +K.

[0077] Analysis reveals that the presence of rotor transient current promotes the attenuation of stator flux linkage. Compensation of the rotor voltage reduces both the rotor transient current and its attenuation of the stator flux linkage. In the absence of rotor transient current, the time constant for stator flux linkage attenuation is τ. s .

[0078] This invention has built a system on the Matlab / Simulink platform, such as Figure 2 The simulation model of the doubly-fed induction generator (DFIG) wind turbine is shown in Table 1. The stator of the DFIG is directly connected to the AC power grid, while the rotor is connected to the AC power grid via RSC and GSC. In the simulation results, the turbine output power is considered positive when the power flows towards the AC power grid. The basic parameters of the simulation model are shown in Table 1.

[0079] Table 1

[0080]

[0081]

[0082] An example of this invention is a wind farm consisting of 2×100 doubly-fed induction generator (DFIG) wind turbines. Before a grid fault, the DFIG operates at a per-unit speed of 1.06, and the active power output of the wind turbines is 0.87 pu. At t=4s, a symmetrical voltage drop occurs in the AC grid, with a drop amplitude of 0.8 pu. Due to the continuity of the stator flux linkage, the instantaneous AC voltage drop will cause a forced component in the stator flux linkage. This forced component generates a transient back electromotive force in the rotor winding circuit, causing the rotor current to rise. When the system experiences an AC voltage drop, the equilibrium state is disrupted, and the reference value of the dq-axis rotor current deviates from the actual value. By controlling the additional transient voltage, part of the transient back electromotive force is offset, and the rise in rotor current is suppressed. During the low-voltage ride-through of wind turbines under traditional vector control, the rotor current reaches a maximum of 3pu, far exceeding the safe threshold of rotor current, and the wind turbine output power fluctuates greatly, which is not conducive to system recovery and safe operation. When the wind turbine is controlled by this invention during the low-voltage ride-through, the rotor current is limited to around the safe threshold of 2, the peak rotor current is reduced by about 50%, and the fluctuation of the active power output of the wind turbine is also effectively reduced, which is conducive to system recovery and safe operation. At the same time, the stator flux decay time is extended compared to the previous method.

[0083] Simulation results verify the correctness of the proposed rotor voltage compensation system and method based on rotor transient current for doubly fed wind turbines.

[0084] This invention provides a rotor voltage compensation system and method for doubly-fed induction generator (DFIG) wind turbines based on rotor transient current. First, the short-circuit fault analysis of the DFIG wind turbine's feed path is performed in both the synchronous rotating coordinate system and the rotor coordinate system. The equivalent circuit and circuit parameters of the rotor winding are obtained through the rotor coordinate system. Different components of the rotor current in the two coordinate systems are obtained through circuit analysis and dynamic equation solving. An equation relationship exists between these components, and by analogy, the steady-state and transient components of the rotor current can be separated. When a low-voltage ride-through occurs, the reference value and actual value of the dq-axis rotor current deviate, triggering the rotor voltage compensation circuit, which increases the rotor voltage output. Compared to traditional vector control methods, this invention can actively compensate for the transient back electromotive force in the rotor winding circuit, suppressing the rise in rotor current and limiting the rotor current within a safe threshold, thus facilitating system recovery and safe operation.

[0085] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0086] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0087] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for rotor voltage compensation in a doubly-fed induction generator (DFIG) based on rotor transient current, characterized in that, Includes the following steps: Obtain the rotor current during the low-voltage ride-through process of the doubly-fed wind turbine and construct the rotor winding circuit; Based on the rotor winding circuit, by obtaining the transient rotor current of the rotor current, the compensation value of the rotor voltage is obtained, wherein the compensation value is used to suppress the increase of the rotor current and compensate for the attenuation of the stator flux linkage by the rotor voltage. During the low voltage ride-through process of the doubly fed wind turbine, short-circuit fault analysis is performed on the DFIG under different rotating coordinate systems to obtain the rotor current. In the process of short-circuit fault analysis using DFIG, the complex vector form of the mathematical model of DFIG is as follows: Among them, U s U r Representing the stator and rotor voltages respectively, ψ s ψ r Representing the stator and rotor flux linkages, I s I r Represent the stator and rotor currents, respectively, R s L s R represents the stator resistance and inductance, respectively. r L r ω represents the rotor resistance and inductance, respectively. slip =ω e -ω r ,ω e ω r L represents the synchronous speed and the generator speed, respectively. m This indicates the mutual inductance between the stator and rotor; During the short-circuit fault analysis using DFIG, based on the stator voltage drop and the characteristic that the stator flux linkage cannot change abruptly, the forced component and free component in the stator flux linkage during the low-voltage ride-through are obtained, and the rotor current under the current inner loop control of the doubly fed wind turbine converter is calculated.

2. The rotor voltage compensation method for a doubly-fed induction generator based on rotor transient current as described in claim 1, characterized in that: In calculating the first rotor current under the current inner loop control of the doubly-fed wind turbine converter, the rotor current is expressed as: In the formula: i rd i rq L represents the d-axis and q-axis components of the rotor current of a doubly-fed wind turbine. rt =L r -L 2 m / L s ,L rt Let k be the equivalent inductance of the rotor circuit in the rotor coordinate system. p With k i Let I be the proportional and derivative constants of the PI controller, respectively. rdref I rqref e is the dq-axis reference value for the rotor current. nd e nq Let τ be the dq-axis component of the rotor's free transient electromotive force. s =L s / R s , where is the stator time constant.

3. The rotor voltage compensation method for a doubly-fed induction generator based on rotor transient current as described in claim 2, characterized in that: In the process of constructing the rotor winding circuit, the rotor current in the synchronous rotating coordinate system is obtained by analyzing the composition of the rotor current, and the rotor winding circuit is constructed accordingly. The rotor current is expressed as: In the formula, i r rc1 The frequency sω is determined by the periodic components of the rotor voltage and back electromotive force. e AC steady-state components, i r rc2 Is with τ s The time constant decays in relation to the transient component of the back electromotive force, and is expressed in terms of τ. r The frequency of the time constant decay is -ω r The communication component, i r rn Representing rotor current in terms of τ r The DC current component decaying with a time constant, where τ r =L rt / R r , where is the rotor time constant; The rotor current in the synchronous rotating coordinate system is expressed as: i rd =i rc1d +i rc2d +i rnd i rq =i rc1q +i rc2q +i rnq In the formula, i rc1d i rc1q For rotor current pair k i i rdref ,k i i rqref The forced response, whose value is i rdref i rqref That is, the rotor current reference value; i rc2d i rc2q Is with τ s The transient component of back electromotive force e decaying with a time constant nd ,e nq Related, and with τ r The frequency of the time constant decay is -ω e The exchange component; i rnd i rnq These are the natural responses of the rotor d-axis and q-axis currents, respectively. They are related to the currents instantaneously before and after a rotor circuit fault, and are expressed as τ. r The alternating current component with a time constant decay.

4. The rotor voltage compensation method for a doubly-fed induction generator based on rotor transient current as described in claim 3, characterized in that: In the process of constructing the rotor winding circuit, based on the rotor current in the synchronous rotating coordinate system, and according to the complex form of the vector of the mathematical model of the DFIG, coordinate transformation is performed to obtain the rotor winding circuit in the rotor coordinate system. The rotor winding circuit is a circuit composed of rotor voltage, rotor back electromotive force, rotor resistance and inductance.

5. The rotor voltage compensation method for a doubly-fed induction generator based on rotor transient current as described in claim 4, characterized in that: In the process of obtaining the transient rotor current of the rotor current, the steady-state rotor current in the synchronous rotating coordinate system is separated from the transient rotor current by Park transformation. After the transient rotor current is combined with the rotor winding circuit, the compensation value is generated.

6. The rotor voltage compensation method for a doubly-fed induction generator based on rotor transient current as described in claim 5, characterized in that: In the process of obtaining the compensation value, the compensation value is represented as follows: in, This is expressed as the compensation value for the rotor voltage. This represents the rotor transient current in the rotor coordinate system; since the angular velocity of the rotor transient voltage is -ω r The reactance value in the rotor circuit is -ω r L rt .

7. The rotor voltage compensation method for a doubly-fed induction generator based on rotor transient current as described in claim 6, characterized in that: A doubly-fed wind turbine rotor voltage compensation system for implementing the aforementioned doubly-fed wind turbine rotor voltage compensation method includes: The data acquisition module is used to acquire the rotor current during the low-voltage ride-through process of the doubly-fed wind turbine. The rotor circuit construction module is used to construct rotor winding circuits; The compensation module is used to obtain a compensation value for the rotor voltage based on the rotor winding circuit by acquiring the transient rotor current of the rotor current, wherein the compensation value is used to suppress the increase of rotor current and reduce the attenuation of stator flux linkage.

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