A method and system for improving the tolerance of a frequency converter-induction motor system

Abstract

The present invention provides a method and system for improving the tolerance of a frequency converter-induction motor system, and relates to the technical field of improving the tolerance of frequency converters. The method includes calculating the stator voltage excitation component reference value through VSC, AFR and AECR when the voltage is temporarily reduced; calculating the stator voltage armature component reference value through ASR, ATR and AACR; wherein the rotor flux reference value during the voltage sag is calculated through VSC, the stator current excitation component reference value is calculated through AFR, the electromagnetic torque reference value is calculated through ASR, and the stator current armature component reference value is calculated through ATR; the stator voltage excitation component reference value and the stator voltage armature component reference value are inverted to generate a three-phase voltage to supply the induction motor. In this method, the VFC in the excitation circuit can enhance the controllability of the induction motor; the MCC in the armature circuit can eliminate the hysteresis of the control system during the voltage sag and improve the anti-interference ability of the control system.

Description

Technical Field

[0001] The present invention relates to the technical field of frequency converter tolerance improvement, and in particular to a frequency converter-induction motor system tolerance improvement method and system. Background Art

[0002] With the continuous development of industrial modernization, frequency converters are widely used in the field of induction motor control. However, frequency converters containing a large number of power electronic devices are extremely sensitive to voltage changes. During the production process, a voltage drop causes the protection device to operate and the equipment to trip, which will cause industrial production to stop. Figure 1 As shown in the figure, variable-frequency drive (VFD) is used to control the operation of induction motors, including rectifier bridge, DC link, control system and inverter. The rectifier bridge is composed of diodes, which obtains pulsating DC voltage by rectifying the power frequency and sinusoidal voltage output by the power grid. Improving the tolerance of the inverter to avoid tripping is essentially to ensure that the induction motor continues to work when a voltage sag occurs.

[0003] At present, the research on improving the voltage sag tolerance of the inverter mainly includes: adding compensation devices, optimizing the topology structure and improving the control system. The addition of compensation devices such as uninterruptible power supply and dynamic voltage restorer usually has high investment cost and operation and maintenance cost. In addition, the introduction of more power electronic devices and switch control circuits to optimize the topology structure will increase power loss and fault risk. At the control strategy level: In the transient process of voltage sag, the voltage / frequency control has problems such as insufficient speed regulation performance and sudden change of stator resistance voltage; weak magnetic control cannot dynamically adjust the rotor flux according to the response characteristics of the induction motor; in the armature circuit of vector control, the speed is controlled by speed closed loop, but the electromagnetic torque drop caused by voltage sag is the essential reason for the speed drop. If the electromagnetic torque is not effectively controlled, the speed drop cannot be significantly suppressed. At the control parameter level: Traditional intelligent algorithms are prone to local optimal solutions due to poor population diversity, and it is difficult to take into account global search and local search during the search process. The control parameters of permanent magnet synchronous motors are optimized based on improved quantum genetic algorithms, but in the time-varying process of voltage sag, constant control parameters cannot provide precise control for induction motors. Fuzzy rules and membership functions are designed based on experience, lacking a scientific and systematic design process. For online optimization, the optimization process of control parameters is extremely complex. When the voltage drops, the response characteristics of the induction motor change rapidly, and the real-time performance of the control system cannot be guaranteed. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a method for improving the tolerance of a frequency converter based on improving control strategies and designing control parameters. The method is specifically a method for improving the tolerance of a frequency converter-induction motor system, which is applicable to the field of improving the tolerance of frequency converters. The specific technical solution includes:

[0005] Calculate the stator voltage excitation component reference value

[0006] Calculate the reference value of the stator voltage armature component

[0007] Reference value of stator voltage excitation component and stator voltage armature component reference value The inverter generates a three-phase voltage and supplies it to the induction motor.

[0008] Preferably, the stator voltage excitation component reference value is calculated include:

[0009] When the voltage drops temporarily, calculate the rotor flux reference value when the voltage drops temporarily

[0010]

[0011] Where V sag is the DC link voltage during voltage sag, V dc is the DC link voltage when there is no voltage sag, ψ * is the rotor flux reference value, T e is the electromagnetic torque, T L is the load torque, k1, k2, k3 are calculation constants;

[0012] Calculate the reference value of the stator current excitation component

[0013]

[0014] In the formula, ψ r is the rotor flux, K F_p and K F_i is the first control parameter pair, s is the Lagrangian operator;

[0015] Calculate the stator voltage excitation component reference value

[0016]

[0017] In the formula, i sd is the stator current excitation component, K EC_p and K EC_i is the second control parameter pair.

[0018] Preferably, the stator voltage armature component reference value is calculated include:

[0019] Calculate electromagnetic torque reference value

[0020]

[0021] In the formula, is the speed reference value, ω r is the rotation speed, K S_p and K S_i is the third control parameter pair;

[0022] Calculate the reference value of the armature component of the stator current

[0023]

[0024] In the formula, K T_p and K T_i is the fourth control parameter pair;

[0025] Calculate the reference value of the stator voltage armature component

[0026]

[0027] In the formula, i sq is the armature component of the stator current, K AC_p and K AC_i is the fifth control parameter pair.

[0028] Furthermore, the method further comprises correcting the stator voltage excitation component reference value

[0029] Calculate the stator voltage excitation component correction reference value

[0030]

[0031] In the formula, is the rated value of the stator voltage excitation component, u sd is the stator voltage excitation component, K EV_p is the sixth control parameter;

[0032] Corrected stator voltage excitation component reference value

[0033]

[0034] In the formula, is the corrected reference value of the stator voltage excitation component.

[0035] Furthermore, the method further comprises correcting the stator voltage armature component reference value

[0036] Calculate the stator voltage armature component correction reference value

[0037]

[0038] In the formula, is the rated value of the stator voltage armature component, u sq is the armature component of the stator voltage, K AV_p is the seventh control parameter;

[0039] Corrected stator voltage armature component reference value

[0040]

[0041] In the formula, is the corrected reference value of the stator voltage armature component.

[0042] Furthermore, the present invention also proposes a least square method (Weighted Least Squares, WLS) that divides the window and introduces a weight function to solve the PI control parameter (Proportional-Integral Control, proportional integral control parameter), so as to achieve adaptive adjustment according to the speed drop situation, specifically including:

[0043] During the voltage drop process, the speed ω r The changed part of the window is divided.

[0044]

[0045] Where i is the window number, δ i is the control parameter to be solved, x j is the jth speed sampling point in the window, u i (x j ) is the corresponding output signal, is the corresponding given input signal;

[0046] For the i-th window, there exists a criterion function J,

[0047]

[0048] In the formula, x node is the speed sampling point at the midpoint of the window, is the corresponding weight function, z i (x j) is the corresponding detection output signal, and m is the number of speed sampling points;

[0049] The Gaussian function is used to assign different weights to the midpoint of the window and the edge of the window.

[0050]

[0051] In the formula, σ 2 is the standard deviation of the Gaussian function;

[0052] When the cumulative value of the criterion function J is the smallest, the corresponding control parameters and control parameter pairs to be solved in each window are solved based on the weighted least squares method.

[0053] Furthermore, the present invention also proposes to optimize the control parameters by using an improved Grey Wolf Optimizer (IGWO) to improve the control accuracy of the inverter. The mutation probability and crossover probability of the algorithm are obtained by nonlinear adjustment. When the voltage is temporarily reduced, the voltage reduction tolerance of the inverter is improved by dynamically adjusting the rotor flux and electromagnetic torque closed loop and adaptively adjusting the optimal control parameters, which specifically includes:

[0054] When the voltage drops temporarily, the speed ω r Introduce the objective function and calculate the objective function value F of all individuals in the population.

[0055]

[0056] Where, t ω is the speed response time, e(t ω ) is the speed error;

[0057] The crossover probability P is adjusted nonlinearly using the hyperbolic tangent function m and mutation probability P c ,

[0058]

[0059]

[0060] Where P m_max , P m_min is the maximum and minimum value of the mutation probability, P c_max , P c_min is the maximum and minimum value of the crossover probability, F avg is the average value of the population objective function, and F′ is the larger value of the objective function corresponding to the two individuals performing the crossover operation;

[0061] Introduce mutation, crossover and selection operations in genetic algorithm into the gray wolf algorithm;

[0062] Among them, the mutation operation,

[0063] H i (g+1)=X a (g)+P m [X b (g)-X c (g)];

[0064] In the formula, H i (g+1) is the variant individual, X a (g), X b (g) and X c (g) is the randomly selected individual in the g-th iteration;

[0065] Crossover operation,

[0066]

[0067] Where U i (g+1) is the individual obtained by the crossover operation, X i (g) is any individual in the population, r j is the random probability;

[0068] Select an action,

[0069]

[0070] Where, X i (g+1) is the next generation individual, F[U i (g+1)] is the objective function of the crossover operation, F[X i (g)] is the objective function of any individual in the population;

[0071] The corresponding control parameters and control parameter pairs in each window are optimized based on the improved grey wolf algorithm.

[0072] Preferably, the method further comprises calculating the electromagnetic torque T when the voltage drops temporarily e ,

[0073] T e =T L -ΔT e ;

[0074]

[0075] In the formula, ΔT e is the change of electromagnetic torque, n p is the pole pair number, L m is the stator-rotor mutual inductance, L r is the rotor inductance, Δi sq is the change in the armature component of the stator current.

[0076] Furthermore, the present invention also provides a method for calculating the phase shift angle θ, which specifically includes:

[0077] The three-phase stator current output by the induction motor is transformed by Clarke and Park in turn to obtain the stator current excitation component i sd and the stator current armature component i sq ;

[0078] Calculate the rotor flux ψ r ,

[0079]

[0080] In the formula, R r is the rotor resistance;

[0081] Calculate the phase shift angle θ,

[0082]

[0083] The phase shift angle is applied to the inverse Park transform of the phase shift process in the Park transform and the inverse Park transform.

[0084] In addition, the present invention also provides a frequency converter-induction motor system tolerance improvement system, including an inverter circuit and VFC and MCC respectively arranged in an excitation circuit and an armature circuit in a control system;

[0085] VFC is used to calculate and output the stator voltage excitation component reference value To the inverter circuit;

[0086] MCC is used to calculate and output the stator voltage armature component reference value To the inverter circuit;

[0087] The inverter circuit is used to set the stator voltage excitation component reference value of VFC and MCC output Reference value of stator voltage armature component The inverter generates a three-phase voltage and supplies it to the induction motor.

[0088] Preferably, the VFC includes a VSC, an AFR and an AECR; the VSC, the AFR and the AECR are connected in sequence, and the output end of the AECR is connected to the inverter circuit;

[0089] VSC is used to calculate the rotor flux reference value during voltage sag

[0090]

[0091] Where V sag is the DC link voltage during voltage sag, V dcis the DC link voltage when there is no voltage sag, ψ * is the rotor flux reference value, T e is the electromagnetic torque, T L is the load torque, k1, k2, k3 are calculation constants;

[0092] AFR is used to calculate the reference value of the stator current excitation component

[0093]

[0094] In the formula, ψ r is the rotor flux, K F_p and K F_i is the control parameter pair of AFR, s is the Lagrangian operator;

[0095] AECR is used to calculate the stator voltage excitation component reference value

[0096]

[0097] In the formula, i sd is the stator current excitation component, K EC_p and K EC_i is the control parameter pair of AECR.

[0098] Preferably, the MCC includes an ASR, an ATR and an AACR; the ASR, the ATR and the AACR are connected in sequence, and the output end of the AACR is connected to the inverter circuit;

[0099] ASR is used to calculate the electromagnetic torque reference value

[0100]

[0101] In the formula, is the speed reference value, ω r is the rotation speed, K S_p and K S_i is the control parameter pair of ASR;

[0102] ATR is used to calculate the reference value of the stator current armature component

[0103]

[0104] In the formula, K T_p and K T_i is the control parameter pair of ATR;

[0105] AACR is used to calculate the stator voltage armature component reference value

[0106]

[0107] In the formula, i sq is the armature component of the stator current, K AC_p and K AC_i is the control parameter pair of AACR;

[0108] MCC output stator voltage armature component reference value to the inverter circuit.

[0109] Furthermore, VFC also includes AEVR;

[0110] The AEVR output terminal is connected to the AECR output terminal to correct the stator voltage excitation component reference value.

[0111]

[0112]

[0113] In the formula, is the reference value for the stator voltage armature component correction, is the rated value of the stator voltage excitation component, u sd is the stator voltage excitation component, K EV_p is the control parameter of AEVR, is the corrected reference value of the stator voltage excitation component.

[0114] Furthermore, MCC also includes AAVR;

[0115] The AAVR output is connected to the AACR output to correct the stator voltage armature component reference value.

[0116]

[0117]

[0118] In the formula, is the reference value for the stator voltage armature component correction, is the rated value of the stator voltage armature component, u sq is the armature component of the stator voltage; K AV_p is the control parameter of AEVR, is the corrected reference value of the stator voltage armature component.

[0119] It can be seen that in the technical solution provided by the present invention, the VFC in the excitation circuit can enhance the controllability of the induction motor; the MCC in the armature circuit can eliminate the lag of the control system when the voltage is temporarily reduced and improve the anti-interference ability of the control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0120] Figure 1 Schematic diagram of the connection relationship between the power grid, inverter and induction motor.

[0121] Figure 2 The figure is a control strategy block diagram of the excitation circuit and the armature circuit in one embodiment of the present invention.

[0122] Figure 3 Schematic diagram of a model of a frequency converter and an induction motor in one embodiment of the present invention.

[0123] Figure 4 This is a control strategy block diagram of the excitation circuit and the armature circuit of a preferred solution in one embodiment of the present invention.

[0124] Figure 5 The figure is a schematic diagram of a model of a frequency converter and an induction motor of a preferred solution in one embodiment of the present invention.

[0125] Figure 6 Schematic diagram of stator current changes in one embodiment of the present invention.

[0126] Figure 7 Schematic diagram of electromagnetic torque change in one embodiment of the present invention.

[0127] Figure 8 Schematic diagram of rotation speed change in one embodiment of the present invention.

[0128] Fig. 9 FIG. 4 is a graph showing the mechanical characteristics of an induction motor according to an embodiment of the present invention.

[0129] Fig.10 It is a schematic diagram of dividing windows according to an embodiment of the present invention.

[0130] Fig.11 Schematic diagram of the relationship between voltage sag amplitude and tolerance time in one embodiment of the present invention.

[0131] Fig.12 Schematic diagram of the relationship between the voltage sag amplitude and the residual speed in one embodiment of the present invention. DETAILED DESCRIPTION

[0132] Compared with the traditional frequency converter, the present invention improves the control strategy and designs the control parameters based on the response characteristics of the induction motor (IM). In the excitation circuit, a variable flux control (VFC) that dynamically adjusts the rotor flux is proposed to enhance the controllability; in the armature circuit, a multiple combination control (MCC) based on voltage feedforward is proposed to eliminate hysteresis and improve anti-interference.

[0133] Among them, VFC includes variable stage control (VSC), dynamic flux regulator (Automatic Flux Regulator, AFR) and dynamic excitation current regulator (Automatic Excitation Current Regulator, AECR). In some actual cases, it also includes feedforward excitation voltage regulator (Feedforward Excitation Voltage Regulator, FEVR) or automatic excitation voltage regulator (Automatic Excitation Voltage Regulator, AEVR). MCC includes dynamic speed regulator (Automatic Speed ​​Regulator, ASR), dynamic torque regulator (Automatic Torque Regulato, ATR) and dynamic armature current regulator (Automatic Armature Current Regulator, AACR). In some actual cases, it also includes feedforward armature voltage regulator (Feedforward Armature Voltage Regulator, FAVR) or automatic armature voltage regulator (Automatic Armature Voltage Regulator, AAVR).

[0134] Among them, the variable magnetization control of the excitation circuit is composed of variable stage control and feedforward control. The variable stage control can adjust the rotor flux reference value according to different stages to enhance the controllability; the voltage feedforward control can achieve timely adjustment of the feedforward through the change of voltage to eliminate the lag. The composite control of the armature circuit is composed of feedback control and voltage feedforward control. The feedback control can make timely adjustment of the feedback through the change of torque to enhance the anti-interference performance; the voltage feedforward control can achieve timely adjustment of the feedforward through the change of voltage to eliminate the lag.

[0135] The present invention will be further described below in conjunction with embodiments and drawings.

[0136] Example 1

[0137] This embodiment provides a method for improving the tolerance of a frequency converter. Figure 2 As shown, it specifically includes steps S1 to S3.

[0138] like Figure 2 As shown, in the excitation circuit, calculating the reference value of the stator voltage excitation component is step S1, and calculating the reference value of the stator voltage armature component is step S2.

[0139] Step S1: Calculate the stator voltage excitation component reference value.

[0140] Step S11: When the voltage drops temporarily, calculate the rotor flux reference value when the voltage drops temporarily

[0141]

[0142] Where V sag is the DC link voltage during voltage sag, V dc is the DC link voltage when there is no voltage sag, ψ * is the rotor flux reference value, T e is the electromagnetic torque, T L is the load torque, k1, k2, k3 are calculation constants.

[0143] Step S12: Calculate the stator current excitation component reference value

[0144]

[0145] In the formula, ψ r is the rotor flux, K F_p and K F_i is the first control parameter pair, and s is the Laplace operator.

[0146] Step S13: Calculate the stator voltage excitation component reference value

[0147]

[0148] In the formula, i sd is the stator current excitation component, K EC_p and K EC_i is the second control parameter pair.

[0149] Step S2: Calculate the stator voltage armature component reference value.

[0150] Step S21: Calculate the electromagnetic torque reference value

[0151]

[0152] In the formula, is the speed reference value, ω r is the rotation speed, K S_p and K S_i is the third control parameter pair.

[0153] Step S22: Calculate the stator current armature component reference value

[0154]

[0155] In the formula, K T_p and K T_i is the fourth control parameter pair.

[0156] Step S23: Calculate the stator voltage armature component reference value through AACR

[0157]

[0158] In the formula, i sq is the armature component of the stator current, K AC_p and K AC_i is the fifth control parameter pair.

[0159] Step S3: Figure 3 As shown, the reference value of the stator voltage excitation component and stator voltage armature component reference value Inverting is performed to generate a three-phase voltage to supply the induction motor. Specifically, the stator voltage excitation component reference value and stator voltage armature component reference value Perform anti-Parker transformation and phase shift processing to obtain the voltage of the two-phase stationary coordinate system; perform SVPWM (Space Vector Pulse Width Modulation) processing on the voltage of the two-phase stationary coordinate system to obtain a pulse signal, and input the pulse signal and DC voltage into the inverter to control the operation of the induction motor.

[0160] Furthermore, if Figure 4 As shown, the method also includes correcting the stator voltage excitation component reference value

[0161] Calculate the stator voltage excitation component correction reference value

[0162]

[0163] In the formula, is the rated value of the stator voltage excitation component, u sd is the stator voltage excitation component, K EV_p It is the sixth control parameter.

[0164] Corrected stator voltage excitation component reference value

[0165]

[0166] In the formula, is the corrected reference value of the stator voltage excitation component.

[0167] Furthermore, if Figure 4 As shown, this method corrects the stator voltage armature component reference value

[0168] Calculate the stator voltage armature component correction reference value

[0169]

[0170] In the formula, is the rated value of the stator voltage armature component, u sq is the armature component of the stator voltage, K AV_p It is the seventh control parameter.

[0171] Corrected stator voltage armature component reference value

[0172]

[0173] In the formula, is the corrected reference value of the stator voltage armature component.

[0174] At the same time, the model schematic diagram of the inverter and induction motor of the further scheme is as follows Figure 5 shown.

[0175] Preferably, when the voltage drops temporarily, the electromagnetic torque T is calculated e ,

[0176] T e =T L -ΔT e ;

[0177]

[0178] In the formula, ΔT e is the change of electromagnetic torque, n p is the pole pair number, L m is the stator-rotor mutual inductance, L r is the rotor inductance, Δi sq is the change in the armature component of the stator current.

[0179] Furthermore, the present invention also proposes a least square method (Weighted Least Squares, WLS) that divides the window and introduces a weight function to solve the PI control parameter (Proportional-Integral Control, proportional integral control parameter), so as to achieve adaptive adjustment according to the speed drop situation, which specifically includes the following steps:

[0180] Step Q1: During the voltage sag, the speed ωr The changed part of the window is divided.

[0181]

[0182] Where i is the window number, δ i is the control parameter to be solved among the first control parameter pair to the fifth control parameter pair, the sixth control parameter and the seventh control parameter, x j is the jth speed sampling point in the window, u i (x j ) is the corresponding output signal, is the corresponding given input signal.

[0183] Step Q2: For the i-th window, there exists a criterion function J,

[0184]

[0185] In the formula, x node is the speed sampling point at the midpoint of the window, is the corresponding weight function, z i (x j ) is the corresponding detection output signal, and m is the number of speed sampling points.

[0186] Step Q3: Use Gaussian function to assign different weights to the midpoint of the window and the edge of the window.

[0187]

[0188] In the formula, σ 2 is the standard deviation of the Gaussian function.

[0189] Step Q4: When the cumulative value of the criterion function J is the smallest, the control parameters to be solved in the first to fifth control parameter pairs, the sixth control parameter and the seventh control parameter in each window are solved based on the weighted least squares method.

[0190] Furthermore, the present invention also proposes to optimize the control parameters by improving the control accuracy of the inverter by using the Improved Grey Wolf Optimizer (IGWO). The mutation probability and crossover probability of the algorithm are obtained by nonlinear adjustment. When the voltage is temporarily reduced, the voltage reduction tolerance of the inverter is improved by dynamically adjusting the rotor flux and electromagnetic torque closed loop and adaptively adjusting the optimal control parameters, which specifically includes the following steps:

[0191] Step R1: When the voltage drops temporarily, the speed ω r Introduce the objective function and calculate the objective function value F of all individuals in the population.

[0192]

[0193] Where, t ω is the speed response time, e(t ω ) is the speed error.

[0194] Step R2: Use the hyperbolic tangent function to nonlinearly adjust the crossover probability P m and mutation probability P c ,

[0195]

[0196]

[0197] Where P m_max , P m_min is the maximum and minimum value of the mutation probability, P c_max , P c_min is the maximum and minimum value of the crossover probability, F avg is the average value of the population objective function, and F′ is the larger value of the objective function corresponding to the two individuals performing the crossover operation.

[0198] Step R3: Introduce the mutation, crossover and selection operations in the genetic algorithm into the gray wolf algorithm;

[0199] Among them, the mutation operation,

[0200] H i (g+1)=X a (g)+P m [X b (g)-X c (g)];

[0201] In the formula, H i (g+1) is the variant individual, X a (g), X b (g) and X c (g) is the randomly selected individual in the g-th iteration;

[0202] Crossover operation,

[0203]

[0204] Where U i (g+1) is the individual obtained by the crossover operation, X i (g) is any individual in the population, r j is the random probability;

[0205] Select an action,

[0206]

[0207] Where, Xi (g+1) is the next generation individual, F[U i (g+1)] is the objective function of the crossover operation, F[X i (g)] is the objective function of any individual in the population.

[0208] Step R4: Optimize the first to fifth control parameter pairs, the sixth control parameter and the seventh control parameter in each window based on the Grey Wolf Algorithm.

[0209] Furthermore, the present invention also provides a method for calculating the phase shift angle θ, which specifically includes:

[0210] The three-phase stator current output by the induction motor is transformed by Clarke and Park in turn to obtain the stator current excitation component i sd and the stator current armature component i sq ;

[0211] Calculate the rotor flux ψ r ,

[0212]

[0213] In the formula, R r is the rotor resistance;

[0214] Calculate the phase shift angle θ,

[0215]

[0216] The phase shift angle is applied to the inverse Park transform of the phase shift process in the Park transform and the inverse Park transform.

[0217] In addition, the present invention also provides a frequency converter-induction motor system tolerance improvement system, including an inverter circuit and VFC and MCC respectively arranged in an excitation circuit and an armature circuit in a control system.

[0218] The VFC includes a VSC, an AFR and an AECR; the VSC, the AFR and the AECR are connected in sequence, and an output end of the AECR is connected to an inverter circuit.

[0219] The MCC includes an ASR, an ATR and an AACR; the ASR, the ATR and the AACR are connected in sequence, and an output end of the AACR is connected to an inverter circuit.

[0220] VSC is used to calculate the rotor flux reference value during voltage sag

[0221]

[0222] Where V sag is the DC link voltage during voltage sag, V dcis the DC link voltage when there is no voltage sag, ψ * is the rotor flux reference value, T e is the electromagnetic torque, T L is the load torque, k1, k2, k3 are calculation constants.

[0223] AFR is used to calculate the reference value of the stator current excitation component

[0224]

[0225] In the formula, ψ r is the rotor flux, K F_p and K F_i is the control parameter pair of AFR, and s is the Laplace operator.

[0226] AECR is used to calculate the stator voltage excitation component reference value

[0227]

[0228] In the formula, i sd is the stator current excitation component, K EC_p and K EC_i is the control parameter pair of AECR.

[0229] VFC output stator voltage excitation component reference value to the inverter circuit.

[0230] ASR is used to calculate the electromagnetic torque reference value

[0231]

[0232] In the formula, is the speed reference value, ω r is the rotation speed, K S_p and K S_i is the control parameter pair of ASR.

[0233] ATR is used to calculate the reference value of the stator current armature component

[0234]

[0235] In the formula, K T_p and K T_i is the control parameter pair of ATR.

[0236] AACR is used to calculate the stator voltage armature component reference value

[0237]

[0238] In the formula, i sq is the armature component of the stator current, K AC_p and K AC_i is the control parameter pair of AACR.

[0239] MCC output stator voltage armature component reference value to the inverter circuit.

[0240] The inverter circuit is used to set the stator voltage excitation component reference value of VFC and MCC output Reference value of stator voltage armature component The inverter generates a three-phase voltage and supplies it to the induction motor.

[0241] Furthermore, the VFC of the system also includes AEVR;

[0242] The AEVR output terminal is connected to the AECR output terminal to correct the stator voltage excitation component reference value.

[0243]

[0244]

[0245] In the formula, is the stator voltage armature component correction reference value, is the rated value of the stator voltage excitation component, u sd is the stator voltage excitation component, K EV_p is the control parameter of AEVR, is the corrected reference value of the stator voltage excitation component.

[0246] Optionally, AEVR can be replaced by FEVR.

[0247] Furthermore, the MCC of the system also includes AAVR;

[0248] The AAVR output is connected to the AACR output to correct the stator voltage armature component reference value.

[0249]

[0250]

[0251] In the formula, is the stator voltage armature component correction reference value, is the rated value of the stator voltage armature component, u sq is the armature component of the stator voltage; K AV_p is the control parameter of AEVR, is the corrected reference value of the stator voltage armature component.

[0252] Optionally, AAVR can be replaced by FAVR.

[0253] Example 2

[0254] This embodiment discloses a method for improving the tolerance of a frequency converter based on improving a control strategy and designing control parameters, which specifically includes the following steps:

[0255] Step S11: When subjected to voltage sag, the response characteristics of the IM can be divided into three operating stages according to the changes in stator current, electromagnetic torque and speed.

[0256] Step S12: Operation phase 1: Figure 6 As shown, the rated operation before the voltage sag occurs.

[0257] Before the voltage sag, the rated voltage U of the VFD input grid N , IM operates at rated working condition, that is, speed ω r Maintain rated speedω N , electromagnetic torque T e Equal to the load torque T N .

[0258] Step S13: Operation phase 2: Figure 7 As shown, during the voltage sag.

[0259] (1) Operation stage 2.1: Electromagnetic torque drops. When the voltage drops temporarily, the DC link voltage decreases with the load power loss, causing the stator current to decrease. During the time when the DC link voltage drops to the grid voltage, the electromagnetic torque drops. When the electromagnetic torque is less than the load torque, the speed starts to drop and the slip rate increases.

[0260] (2) Operation phase 2.2: Electromagnetic torque recovery I: lower than the load torque. When the DC link voltage decreases to the grid voltage, the grid voltage supplies power to the load. The increase in slip rate causes the rotor current to increase. According to the law of electromagnetic induction, the stator current increases with the rotor current, resulting in an increase in both the excitation component and the armature component of the stator current. The increase in the armature component of the stator current can increase the electromagnetic torque.

[0261] (3) Operation stage 2.3: Electromagnetic torque recovery II: higher than the load torque. Due to the continuous increase of the armature component of the stator current, the electromagnetic torque continues to increase after recovering to the load torque, and then exceeds the load torque. When the electromagnetic torque is greater than the load torque, the speed begins to recover.

[0262] (4) Operation stage 2.4: electromagnetic torque is stable. With the change of electromagnetic torque and the recovery of speed, when IM reaches transient stability, the electromagnetic torque drops back to the load torque and the speed remains stable.

[0263] Step S14: Operation phase 3: Figure 8 As shown, stable operation after voltage sag.

[0264] After suffering a voltage sag, the grid voltage is higher than the DC link voltage and will directly power the load. The electromagnetic torque surges and drops instantly and stabilizes at the load torque, and the speed recovers to the rated speed and remains stable.

[0265] Step S2 includes the following sub-steps:

[0266] Step S21: The change in electromagnetic torque is:

[0267]

[0268] In the formula, ΔT e is the change of electromagnetic torque, i sq is the armature component of the stator current, Δi sq is the change in the armature component of the stator current, ψ r is the rotor flux, Δψ r is the rotor flux change, n p is the pole pair number, L m is the stator-rotor mutual inductance, L r is the rotor inductance.

[0269] Step S22: When a voltage sag occurs, Δψ r Compared to ψ r is a very small amount, and the change of electromagnetic torque is rewritten as:

[0270]

[0271] The change of electromagnetic torque is positively correlated with the change of the armature component of the stator current.

[0272] Step S23: The change in the armature component of the stator current is:

[0273]

[0274] In the formula, i s is the stator current, Δi s is the stator current variation.

[0275] A decrease in the change in the rotor flux will cause an increase in the change in the armature component of the stator current, thereby causing an increase in the change in the electromagnetic torque.

[0276] Step S24: The VSC capable of dynamically adjusting the rotor flux is:

[0277]

[0278] In the formula, is the rotor flux reference value when subjected to voltage sag, V sag is the DC link voltage when it is subjected to voltage sag, V dc is the DC link voltage when there is no voltage sag, k1, k2, k3 are calculation constants, and smooth switching is achieved by adjusting the rotor flux reference value to be equal during the switching control stage, ψ * is the rotor flux reference value, ΔV dc is the DC link voltage fluctuation.

[0279] Step S25: In operation phase 2.1, in order to quickly reduce the rotor flux, the DC link voltage that changes first is used as a key factor. The VSC quickly reduces the rotor flux according to the DC link voltage. The speed drop rate is suppressed by suppressing the reduction of the armature component of the stator current and the reduction of the electromagnetic torque.

[0280] Step S26: In operation phase 2.2, the DC link voltage is constant. In order to continuously reduce the rotor flux, the gradually recovered electromagnetic torque is used as a key factor. The VSC continuously reduces the rotor flux according to the electromagnetic torque. The speed drop time is shortened by promoting the increase of the armature component of the stator current and the recovery of the electromagnetic torque.

[0281] Step S27: In operation stage 2.3, the electromagnetic torque changes too complexly. In order to continuously reduce the rotor flux, the gradually recovered speed is taken as the key factor. The VSC continuously reduces the rotor flux according to the speed. The speed recovery is promoted by promoting the increase of the armature component of the stator current and the recovery of the electromagnetic torque.

[0282] Step S28: In operation phase 2.4, in order to maintain a constant rotor flux, a stable speed is taken as a key factor. The VSC maintains the stability of the rotor flux according to the speed. The speed transient stability is maintained by maintaining the stability of the stator current armature component and the electromagnetic torque.

[0283] Step S3 includes the following sub-steps:

[0284] Step S31: According to the mechanical characteristic curve of IM Fig. 9 As shown, when the voltage drops, the electromagnetic torque T e T from point A e 'A fall occurs, and the fall is T at point B e ", speed ω r Maintain ω' due to inertia r However, the electromagnetic torque T e Less than load torque TL When the speed ω r Start to fall, and finally reach point C ω" r As the slip rate increases, the electromagnetic torque T e promote.

[0285] Step S32: The reference value of the armature component of the stator current can be adjusted only after the speed changes, causing a significant drop in the electromagnetic torque, thereby increasing the speed drop rate.

[0286] Step S33: The change of the rotor flux affects the calculation of the reference value of the stator current excitation component, interferes with the recovery process of the electromagnetic torque, and thus prolongs the speed drop time.

[0287] Step S34: The ASR calculates the electromagnetic torque reference value according to the difference between the speed reference value and the measured value.

[0288] Step S35: The ATR calculates a stator current armature component reference value according to the difference between the electromagnetic torque reference value and the measured value.

[0289] Step S36: When the voltage drops temporarily, the ATR can timely adjust the reference value of the stator current armature component according to the drop of the electromagnetic torque to avoid a sharp drop of the electromagnetic torque, thereby reducing the speed drop rate.

[0290] Step S37: ATR can eliminate the influence of the rotor flux change on the reference value of the stator current armature component, suppress the interference with the electromagnetic torque recovery, and thus shorten the speed drop time.

[0291] Step S4 includes the following sub-steps:

[0292] Step S41: Divide the window according to the speed drop situation. Fig.10 As shown, the operating condition is a voltage sag that can cover the complete speed drop situation.

[0293] Step S42: The i-th window is:

[0294]

[0295] In the formula, x j is the speed sampling point in the window, u is the calculated output signal, h is the given input signal, θ i are the PI control parameters to be solved.

[0296] Step S43: The i-th window criterion function J is:

[0297]

[0298] In the formula, x node is the speed sampling point at the midpoint of the window, z i (xj ) is the output signal of the detection, is the weight function.

[0299] Step S44: Use a Gaussian function to assign different weights to the window midpoint and the window edge.

[0300]

[0301] In the formula, σ 2 is the standard deviation of the Gaussian function.

[0302] Step S45: In the control strategy of the excitation circuit and the armature circuit, according to the given input signal and the detected output signal, when the cumulative value of the weighted square deviation calculated by the criterion function is minimized, the PI control parameters of AFR, ASR and ATR in each window are solved based on WLS, so as to achieve adaptive adjustment according to the speed drop situation.

[0303] Step S5 includes the following sub-steps:

[0304] Step S51: When the voltage is temporarily reduced, it is necessary to suppress the speed drop to prevent the equipment from tripping. Therefore, the speed is introduced into the objective function, and the objective function values ​​of all individuals in the population are calculated.

[0305]

[0306] Where, t ω is the speed response time, e(t ω ) is the speed error.

[0307] Step S52: Adjust the mutation and crossover probabilities. The mutation and crossover probabilities determine the performance of the algorithm. If the values ​​are large, the global search capability is strong; if the values ​​are small, the local search capability is strong. However, if the values ​​are constant or linearly changed, the global search capability is insufficient due to poor population diversity in the early stage, and the local search capability is insufficient due to poor rapid convergence in the later stage. Therefore, the hyperbolic tangent function is used to nonlinearly adjust the crossover and mutation probabilities.

[0308]

[0309]

[0310] In the formula, F is the individual objective function value, F max is the maximum value of the population objective function, F avg is the average value of the population objective function, F′ is the larger value of the objective function when two individuals perform the crossover operation, and P m is the mutation probability, P c is the crossover probability, P m_max and P c_max is the maximum mutation probability and crossover probability, Pm_min and P c_min is the minimum mutation probability and crossover probability.

[0311] Step S53: Introduce the mutation, crossover and selection operations in the genetic algorithm into the grey wolf algorithm.

[0312] Step S54: The mutation operation is:

[0313] H i (g+1)=X a (g)+P m [X b (g)-X c (g)];

[0314] Where, X a (g), X b (g) and X c (g)X c (g) is the randomly selected individual in the g-th iteration, H i (g+1) is the mutant individual.

[0315] Step S55: The crossover operation is:

[0316]

[0317] Where U i (g+1) is the individual obtained by the crossover operation, X i (g) is the individual in the population, r j is a random probability.

[0318] Step S56: Select the operation:

[0319]

[0320] Where, X i (g+1) is the next generation individual, F[U i (g+1)] is the objective function of the crossover operation, F[X i (g)] is the objective function of any individual in the population.

[0321] Step S57: Optimize the PI control parameters of AFR, ASR and ATR in each window based on IGW. Build a model of the inverter and induction motor according to the improved control strategy and the designed control parameters, including the improved control strategies VFC and MCC, and the designed control parameters in AFR, ASR and ATR. According to the measured stator three-phase current, the stator current excitation component and armature component of the dq coordinate system are converted by Park (Park transformation), and the amplitude and phase of the rotor flux are output after calculation. In the excitation circuit, the VFC is used to output the rotor flux reference value, and the difference between it and the rotor flux amplitude is input into the AFR, so as to output the stator current excitation component reference value. In the armature circuit, according to the speed reference value, the speed measurement value, the electromagnetic torque reference value and the electromagnetic torque measurement value, the stator current armature component reference value is output through the ASR and ATR in the MCC. The reference values ​​of the excitation component and the armature component of the stator current, as well as the rotor flux phase are inversely transformed into three-phase current reference values ​​by Park, and are input into PWM together with the three-phase current measurement value, so as to output a pulse signal. The inverter provides three-phase voltage to the IM according to the DC voltage and pulse signal.

[0322] The effectiveness and applicability of the proposed method in improving the voltage sag tolerance of the inverter are verified by comparing the immune voltage sag amplitude (IVSA), voltage sag tolerance time (VSTT), trip voltage sag amplitude (TVSA) and induction motor residual speed (IMRS). Among them, IVSA represents the minimum amplitude without tripping of the device; VSTT represents the maximum time from voltage sag to device tripping; TVSA represents the maximum amplitude of device tripping; IMRS represents the minimum speed after voltage sag.

[0323] The voltage sag range is [0.5pu, 1pu], and 51 simulations are performed with a step size of 0.01pu. Control system 1 is a traditional control strategy and undesigned control parameters, control system 2 is an improved control strategy and undesigned control parameters, and control system 3 is an improved control strategy and designed control parameters. The relationship between the voltage sag amplitude and the tolerance time is shown in Fig.11 , as shown in Table 1 and Table 2.

[0324] Table 1

[0325] Control System 1 2 3 Immune voltage sag amplitude 0.76 0.68 0.63

[0326] Table 2

[0327] Control System 1 2 3 0.5pu 12 18 25 … … … … 0.62pu 12 21 32 0.63pu 12 22 / … … … … 0.67pu 25 42 / 0.68pu 26 / / … … … … 0.75pu 50 / / 0.76pu / / / … … … …

[0328] Compared with control system 1, control system 2 has IVSA reduced from 0.76pu to 0.68pu, with a reduction of 10.53%; within the voltage sag range of [0.5pu0.67pu], VSTT is increased by 6ms-17ms, with an average increase of 8.94ms, that is, an increase of 50%-83.33%, with an average increase of 62.31%.

[0329] Compared with control system 2, control system 3 reduces IVSA from 0.68pu to 0.63pu, a decrease of 7.35%; in the voltage sag range of [0.5pu, 0.62pu], VSTT increases by 7ms-12ms, an average increase of 8.08ms, that is, an increase of 31.58%-52.38%, an average increase of 43.28%. The above analysis shows that the improved control strategy and designed control parameters of the present invention can improve the tolerance of the inverter. The relationship between the voltage sag amplitude and the residual speed is as follows: Fig.12 , as shown in Table 3 and Table 4.

[0330] Table 3

[0331] Control System 1 2 3 Trip voltage drop amplitude 0.75 0.67 0.62

[0332] Table 4

[0333] Control System 1 2 3 … … … … 0.62pu / / / 0.63pu / / 1350 … … … … 0.67pu / / 1380 0.68pu / 1349 1386 … … … … 0.75pu / 1399 1420 0.76pu 1351 1405 1424 … … … … 1pu 1460 1460 1460

[0334] Compared with control system 1, TVSA of control system 2 is reduced from 0.75pu to 0.67pu, with a reduction of 10.67%; within the voltage sag range of [0.76pu, 1pu), IMRS increases from 0r / min to 54r / min, with an average increase of 16.43r / min, that is, an increase of 0.00% to 4.00%, with an average increase of 1.18%. Compared with control system 2, TVSA of control system 3 is reduced from 0.67pu ​​to 0.62pu, with a reduction of 7.46%; within the voltage sag range of [0.68pu, 1pu), IMRS increases from 0.1r / min to 37r / min, with an average increase of 10.83r / min, that is, an increase of 0.01% to 2.74%, with an average increase of 0.78%.

[0335] It can be seen that in the technical solution provided by the present invention, the VFC in the excitation circuit can enhance the controllability of the induction motor; the MMC in the armature circuit can eliminate the lag of the control system when the voltage is temporarily reduced and improve the anti-interference ability of the control system.

[0336] Furthermore, on the basis of achieving the above-mentioned beneficial effects, each preferred scheme has also achieved the following beneficial effects: by taking into account the stator current excitation component correction reference value and the stator current armature component correction reference value, their values ​​can be set to an accuracy that ensures the control accuracy of the inverter; by solving the PI control parameters by the window least squares method that divides the window and introduces the weight function, adaptive adjustment can be achieved according to the speed drop situation; by optimizing the control parameters by nonlinearly adjusting the mutation probability and the crossover probability of the improved grey wolf algorithm, the control accuracy of the inverter can be improved; and the calculation of the phase shift angle can ensure the smooth progress of the inverter processing and system regulation.

[0337] In addition, the system corresponding to the method can ensure the specific implementation of the technical solution provided by the present invention in various application environments.

Claims

1. A method for improving the tolerance of a frequency converter-induction motor system, characterized in that: For induction motors, these include: Calculate the stator voltage excitation component reference value Calculate the reference value of the stator voltage armature component Reference value for stator voltage excitation component and stator voltage armature component reference value Perform inversion processing to generate three-phase voltage to supply the induction motor; The calculated stator voltage excitation component reference value include: When the voltage drops temporarily, calculate the rotor flux reference value when the voltage drops temporarily Where V sag is the DC link voltage during voltage sag, V dc is the DC link voltage when there is no voltage sag, ψ * is the rotor flux reference value, T e is the electromagnetic torque, T L is the load torque, k1, k2, k3 are calculation constants; Calculate the reference value of the stator current excitation component In the formula, ψ r is the rotor flux, K F_p and K F_i is the first control parameter pair, s is the Lagrangian operator; Calculate the stator voltage excitation component reference value In the formula, i sd is the stator current excitation component, K EC_p and K EC_i is the second control parameter pair; The calculated stator voltage armature component reference value include: Calculate electromagnetic torque reference value In the formula, is the speed reference value, ω r is the rotation speed, K S_p and K S_i is the third control parameter pair; Calculate the reference value of the armature component of the stator current In the formula, K T_p and K T_i is the fourth control parameter pair; Calculate the reference value of the stator voltage armature component In the formula, i sq is the armature component of the stator current, K AC_p and K AC_i is the fifth control parameter pair.

2. A method for improving the tolerance of a frequency converter-induction motor system as claimed in claim 1, characterized in that: Also includes the reference value of the corrected stator voltage excitation component Calculate the stator voltage excitation component correction reference value In the formula, is the rated value of the stator voltage excitation component, u sd is the stator voltage excitation component, K EV_p is the sixth control parameter; Corrected stator voltage excitation component reference value In the formula, is the corrected reference value of the stator voltage excitation component.

3. A method for improving the tolerance of a frequency converter-induction motor system as claimed in claim 1, characterized in that: Also includes the reference value of the corrected stator voltage armature component Calculate the stator voltage armature component correction reference value In the formula, is the rated value of the stator voltage armature component, u sq is the armature component of the stator voltage, K AV_p is the seventh control parameter; Corrected stator voltage armature component reference value In the formula, is the corrected reference value of the armature component of the stator voltage.

4. A method for improving the tolerance of a frequency converter-induction motor system as claimed in any one of claims 1 to 3, characterized in that: Also includes: During the voltage drop process, the speed ω r The changed part of the window is divided. Where i is the window number, δ i is the control parameter or control parameter pair to be solved, x j is the jth speed sampling point in the window, u i (x j ) is the corresponding output signal, is the corresponding given input signal; For the i-th window, there exists a criterion function J, In the formula, x node is the speed sampling point at the midpoint of the window, is the corresponding weight function, z i (x j ) is the corresponding detection output signal, and m is the number of speed sampling points; The Gaussian function is used to assign different weights to the midpoint and edge of the window. In the formula, σ 2 is the standard deviation of the Gaussian function; When the cumulative value of the criterion function J is the smallest, the corresponding control parameters and control parameter pairs to be solved in each window are solved based on the weighted least squares method.

5. A method for improving the tolerance of a frequency converter-induction motor system as claimed in claim 4, characterized in that: Also includes: When the voltage drops temporarily, the speed ω r Introduce the objective function and calculate the objective function value F of all individuals in the population. Where, t ω is the speed response time, e(t ω ) is the speed error; The crossover probability P is adjusted nonlinearly using the hyperbolic tangent function m and mutation probability P c , Where P m_max , P m_min is the maximum and minimum value of the mutation probability, P c_max , P c_min is the maximum and minimum value of the crossover probability, F avg is the average value of the population objective function, and F′ is the larger value of the objective function corresponding to the two individuals performing the crossover operation; Introduce mutation, crossover and selection operations in genetic algorithm into the gray wolf algorithm; Among them, the mutation operation, H i (g+1)=X a (g)+P m [X b (g)-X c (g)]; In the formula, H i (g+1) is the variant individual, X a (g), X b (g) and X c (g) is the randomly selected individual in the g-th iteration; Crossover operation, Where U i (g+1) is the individual obtained by the crossover operation, X i (g) is any individual in the population, r j is the random probability; Select an action, Where, X i (g+1) is the next generation individual, F[U i (g+1)] is the objective function of the crossover operation, F[X i (g)] is the objective function of any individual in the population; The corresponding control parameters and control parameter pairs in each window are optimized based on the improved grey wolf algorithm.

6. A method for improving the tolerance of a frequency converter-induction motor system as claimed in any one of claims 1 to 3, characterized in that: It also includes the calculation of the electromagnetic torque T when the voltage drops temporarily. e , T e =T L -ΔT e ; In the formula, ΔT e is the change of electromagnetic torque, n p is the pole pair number, L m is the stator-rotor mutual inductance, L r is the rotor inductance, Δi sq is the change in the armature component of the stator current.

7. A method for improving the tolerance of a frequency converter-induction motor system as claimed in any one of claims 1 to 3, characterized in that: It also includes calculating the phase shift angle θ; The three-phase stator current output by the induction motor is transformed by Clarke and Park in turn to obtain the stator current excitation component i sd and the stator current armature component i sq ; Calculate the rotor flux ψ r , In the formula, R r is the rotor resistance; Calculate the phase shift angle θ, The phase shift angle is applied to the inverse Park transform of the phase shift process in the Park transform and the inverse Park transform.

8. A frequency converter-induction motor system tolerance improvement system, characterized in that: It includes an inverter circuit and VFC and MCC respectively arranged in an excitation circuit and an armature circuit in a control system; VFC is used to calculate and output the stator voltage excitation component reference value To the inverter circuit; MCC is used to calculate and output the stator voltage armature component reference value To the inverter circuit; The inverter circuit is used to set the stator voltage excitation component reference value of VFC and MCC output Reference value of stator voltage armature component Perform inversion processing to generate three-phase voltage to supply the induction motor; The VFC includes a VSC, an AFR and an AECR; the VSC, the AFR and the AECR are connected in sequence, and the output end of the AECR is connected to an inverter circuit; VSC is used to calculate the rotor flux reference value during voltage sag Where V sag is the DC link voltage during voltage sag, V dc is the DC link voltage when there is no voltage sag, ψ * is the rotor flux reference value, T e is the electromagnetic torque, T L is the load torque, k1, k2, k3 are calculation constants; AFR is used to calculate the reference value of the stator current excitation component In the formula, ψ r is the rotor flux, K F_p and K F_i is the control parameter pair of AFR, s is the Lagrangian operator; AECR is used to calculate the stator voltage excitation component reference value In the formula, i sd is the stator current excitation component, K EC_p and K EC_i is the control parameter pair of AECR; The MCC includes an ASR, an ATR and an AACR; the ASR, the ATR and the AACR are connected in sequence, and the output end of the AACR is connected to an inverter circuit; ASR is used to calculate the electromagnetic torque reference value In the formula, is the speed reference value, ω r is the rotation speed, K S_p and K S_i is the control parameter pair of ASR; ATR is used to calculate the reference value of the stator current armature component In the formula, K T_p and K T_i is the control parameter pair of ATR; AACR is used to calculate the stator voltage armature component reference value In the formula, i sq is the armature component of the stator current, K AC_p and K AC_i is the control parameter pair of AACR; MCC output stator voltage armature component reference value to the inverter circuit.

9. A frequency converter-induction motor system tolerance improvement system as claimed in claim 8, characterized in that: VFC also includes AEVR; The AEVR output terminal is connected to the AECR output terminal to correct the stator voltage excitation component reference value. In the formula, is the stator voltage armature component correction reference value, is the rated value of the stator voltage excitation component, u sd is the stator voltage excitation component, K EV_p is the control parameter of AEVR, is the corrected reference value of the stator voltage excitation component.

10. The inverter-induction motor system tolerance improvement system according to claim 8, characterized in that: MCC also includes AAVR; The AAVR output is connected to the AACR output to correct the stator voltage armature component reference value. In the formula, is the stator voltage armature component correction reference value, is the rated value of the stator voltage armature component, u sq is the armature component of the stator voltage; K AV_p is the control parameter of AEVR, is the corrected reference value of the armature component of the stator voltage.

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