Capacitive current compensation-based dual three-phase permanent magnet synchronous motor voltage stabilization control method

Abstract

The invention relates to the technical field of aviation motors, and provides a dual three-phase permanent magnet synchronous motor voltage stabilization control method based on capacitance current compensation, comprising the following steps: S1, decoupling two sets of three-phase windings of a dual three-phase permanent magnet synchronous motor to obtain a mathematical model of the dual three-phase motor; s2, initial controller parameters of a voltage outer loop and a current inner loop are determined based on the mathematical model, and a compensation coefficient is set; s3, collecting the voltage of the direct current bus in real time, and calculating to obtain the capacitance current value of the direct current bus; and S4, the compensation amount of the q-axis current instruction is obtained according to the compensation coefficient and the capacitance current value of the direct current bus voltage. According to the dual three-phase permanent magnet synchronous motor voltage stabilization control method based on capacitance current compensation, the transient change of the load is reflected according to the sudden change of the direct current bus capacitance current value, and then the capacitance current value is used for compensating the current instruction of the current inner ring, so that the current instruction is quicker, and the dynamic response of the system is accelerated.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation motors, and in particular to a voltage stabilization control method for a dual three-phase permanent magnet synchronous motor based on capacitor current compensation. Background Art

[0002] In addition to the advantages of ordinary three-phase permanent magnet synchronous motors such as high efficiency and energy saving, high power density, simple structure and strong reliability, the dual three-phase permanent magnet synchronous motor can also output high power using low-voltage power electronic devices, and the structure of the two sets of windings facilitates fault-tolerant control. It has broad prospects in the aviation field and has been widely studied. It is suitable for use as an aviation starter generator.

[0003] When the dual three-phase permanent magnet synchronous motor is used as a starter generator, it has two working modes: starting and generating. In the starting mode, the motor is an electric motor, driving the aircraft engine to the ignition speed, and then maintaining positive torque to provide power for the smooth start of the aircraft; in the generating mode, the motor is a generator, providing electrical energy to the onboard equipment through voltage stabilization control.

[0004] In terms of voltage control, the dual three-phase permanent magnet synchronous motor is different from the electric excitation motor. Its rotor magnetic field is generated by permanent magnets and is difficult to adjust. A rectifier voltage regulator is required to output a stable DC voltage. PWM controlled rectification can achieve bidirectional transmission of electric energy, and the output DC voltage can obtain high-quality control. It is the most popular rectification method at present. The FOC (field oriented) vector control strategy can be used in the control strategy of the PWM rectifier.

[0005] The traditional vector control strategy consists of three parts: the voltage outer loop, the current inner loop and the SVPWM part. The voltage outer loop control compares the measured DC bus voltage with the given value, makes the voltage error 0 through PI control, and then outputs the current given by the current inner loop through negative feedback. Then, the final rectifier PWM signal is obtained through the current inner loop PI controller and SVPWM to achieve voltage stabilization control, so that the bus voltage is stable at the given voltage. However, the traditional double closed-loop vector control method faces the problems of insufficient dynamic response and large changes in DC bus voltage when the load suddenly changes. The reason is that when the load suddenly changes, the current command can only change when the actual DC bus voltage detected by the voltage outer loop deviates from the reference DC voltage. However, due to the existence of the DC bus capacitor, the DC voltage will not suddenly change, which makes the voltage outer loop unable to generate fast and effective current commands to offset the impact of load disturbances, resulting in a decrease in control performance. Summary of the invention

[0006] In view of this, the present invention proposes a dual three-phase permanent magnet synchronous motor voltage stabilization control method based on capacitor current compensation, which reflects the instantaneous change of the load according to the sudden change of the DC bus capacitor current value, and then uses the capacitor current value to compensate the current command of the current inner loop, so that the current command is faster, thereby accelerating the dynamic response of the system.

[0007] The technical solution of the present invention is implemented as follows: The present invention provides a voltage stabilization control method for a dual three-phase permanent magnet synchronous motor based on capacitor current compensation, comprising the following steps:

[0008] S1 decouples two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor to obtain a mathematical model of the dual three-phase motor;

[0009] S2 determines the initial controller parameters of the voltage outer loop and the current inner loop based on the mathematical model and sets the compensation coefficients;

[0010] S3 collects the voltage of the DC bus in real time and calculates the capacitance current value of the DC bus;

[0011] S4 obtains the compensation amount of the q-axis current command according to the compensation coefficient and the capacitance current value of the DC bus voltage;

[0012] S5 determines the transfer function of the voltage outer loop after adding capacitor current compensation according to the compensation amount of the q-axis current command;

[0013] S6 adjusts the initial controller parameters of the voltage outer loop according to the transfer function after adding capacitor current compensation to the voltage outer loop, obtains the final controller parameters of the voltage outer loop, and performs voltage stabilization control on the motor through the final controller parameters of the voltage outer loop.

[0014] On the basis of the above technical solution, preferably, in step S1, the mathematical model includes a voltage equation, a flux equation and a torque equation, and the voltage equation, the flux equation and the torque equation are respectively:

[0015]

[0016] T e =3p[(L d -L q )i d i q +ψ f i q ]

[0017] Among them, u d1 、u d2 、u q1 、u q2 are the dq axis voltages of the two windings, i d1 、i d2 、iq1 、i q2 are the dq axis currents of the two windings, ψ d1 , d2 , q1 , q2 are the dq axis flux of the two sets of windings, ω e is the electrical angular velocity of the motor, ψ f is the permanent magnet flux, L d , L q is the dq axis inductance, L dd , L dq is the d-axis mutual inductance and q-axis mutual inductance between the two sets of windings, T e is the electromagnetic torque of the motor, and p is the number of motor pole pairs.

[0018] On the basis of the above technical solution, preferably, step S1 includes the following steps:

[0019] S11 transforms the currents of the two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor into two independent dq coordinate systems respectively;

[0020] S12 In the dq coordinate system, the voltage equations of the two sets of windings of the motor are expressed as independent dq axis voltage equations;

[0021] S13 associates the flux equations of the two sets of windings with the corresponding dq-axis current and inductance matrices, respectively, and decouples the flux to obtain a mathematical model of the dual three-phase motor.

[0022] On the basis of the above technical solution, preferably, step S2 includes the following steps:

[0023] S21 determines the controller parameters of the current inner loop according to the mathematical model;

[0024] S22 obtains the closed-loop transfer function of the current inner loop through the controller parameters of the current inner loop;

[0025] S23 obtains initial controller parameters of the voltage outer loop according to the closed-loop transfer function of the current inner loop.

[0026] Further preferably, in step S21, the bandwidth of the current outer loop is set to 1 / 10 of the switching frequency, and the controller parameters of the current inner loop are:

[0027]

[0028] Among them, k id , k pd are the integral coefficient and proportional coefficient of the d-axis current controller, k iq , k pqare the integral coefficient and proportional coefficient of the q-axis current controller, R is the motor stator resistance, T s is the switching period, ω c is the cut-off frequency of the current inner loop.

[0029] More preferably, in step S22, the transfer function of the current inner loop and its simplified result are:

[0030]

[0031] Among them, k i is the integral coefficient of the current inner loop d-axis and q-axis controller, and S is the complex frequency variable.

[0032] More preferably, in step S23, the initial controller parameters of the voltage outer loop are:

[0033]

[0034] Among them, k p , k i are the integral coefficient and proportional coefficient of the voltage outer loop controller, ω cu is the cut-off frequency of the voltage outer loop, T is the equivalent time constant of the current inner loop, R L is the load resistance, and C is the DC bus capacitance.

[0035] On the basis of the above technical solution, preferably, in step S3, the capacitance current value of the DC bus is expressed as:

[0036]

[0037] Among them, I c is the capacitor current value, T delay is the delay time between obtaining the voltage twice, and ΔU is the difference between obtaining the DC bus voltage twice.

[0038] On the basis of the above technical solution, preferably, the step S2 further comprises determining the value of the compensation coefficient K according to the transfer function of the load disturbance signal, and the transfer function of the load disturbance signal is:

[0039]

[0040] Among them, G I is the current inner loop closed loop transfer function, i L is the load current, U is the bus voltage, S is the complex frequency variable, C is the DC bus capacitance, T s is the switching period, k p , k i They are the integral coefficient and proportional coefficient of the voltage outer loop controller respectively.

[0041] On the basis of the above technical solution, preferably, the transfer function of the voltage outer loop after adding capacitor current compensation is:

[0042]

[0043] Among them, G I is the current inner loop closed-loop transfer function, S is the complex frequency variable, C is the DC bus capacitance, T s is the switching period, k p is the integral coefficient of the voltage outer loop controller, ω c is the cut-off frequency of the current inner loop, and K is the compensation coefficient.

[0044] The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention has the following beneficial effects compared with the prior art:

[0045] (1) By introducing a real-time compensation mechanism for capacitor current, the dynamic response problem of traditional dual closed-loop vector control in the case of load mutation is significantly improved. Compared with the traditional method, this scheme not only relies on the detection of bus voltage in the voltage outer loop, but also calculates the capacitor current of the DC bus in real time and uses it as the compensation amount to directly adjust the q-axis current command, so that the current inner loop can respond quickly to load changes. This compensation mechanism effectively reduces the large fluctuations of the DC bus voltage, enhances the dynamic response capability of the system and the accuracy of voltage regulation control, and significantly improves the control performance and stability of the system, especially in the case of load mutation.

[0046] (2) The DC bus capacitance is calculated by using the difference between the two DC bus voltage acquisitions and the delay time between the two voltage acquisitions. The calculation based on the instantaneous voltage change can reflect the change of capacitor current in real time, which helps to quickly respond to dynamic changes in the system. By accurately calculating the capacitor current, the accuracy of the voltage outer loop control can be effectively improved, the voltage regulation performance of the system can be enhanced, and voltage fluctuations can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0048] Figure 1 It is a schematic diagram of the steps of the voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention;

[0049] Figure 2A block diagram of a dual three-phase permanent magnet synchronous motor voltage stabilization control method based on capacitor current compensation of the present invention;

[0050] Figure 3 It is a voltage outer loop block diagram of the voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention;

[0051] Figure 4 It is a current inner loop block diagram of the voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention;

[0052] Figure 5 A schematic diagram of capacitor current calculation of a dual three-phase permanent magnet synchronous motor voltage stabilization control method based on capacitor current compensation according to the present invention;

[0053] Figure 6 It is a schematic diagram of the response of the system when the load current changes stepwise in the voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention;

[0054] Figure 7 Bode diagram of system transfer function corresponding to different K values ​​of the voltage stabilization control method of dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention;

[0055] Figure 8 It is a schematic diagram of a simulation implementation example of a voltage stabilization control method for a dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention;

[0056] Fig. 9 This is an example diagram comparing capacitor current waveforms before and after compensation of the dual three-phase permanent magnet synchronous motor voltage stabilization control method based on capacitor current compensation of the present invention;

[0057] Fig.10 It is an example diagram of the current command waveform before and after compensation of the voltage stabilization control method of the dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention;

[0058] Fig.11 It is a stereoscopic diagram of the voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention. DETAILED DESCRIPTION

[0059] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0060] When faced with a sudden load change, the current command of the inner current loop of the traditional vector control rectifier voltage stabilization strategy is not fast enough, resulting in insufficient system dynamic response, large DC voltage changes, and long voltage recovery time. It cannot meet some applications with high requirements for power generation quality, such as aviation starter generators. Therefore, a dual three-phase permanent magnet synchronous motor voltage stabilization control method based on capacitor current compensation is proposed in this scheme. According to the sudden change of the DC bus capacitor current value, the instantaneous change of the load is reflected, and then the capacitor current value is used to compensate the current command of the inner current loop, making the current command faster, thereby accelerating the dynamic response of the system.

[0061] like Figure 1-7 As shown, the voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation of the present invention specifically includes steps S1-S6.

[0062] Step S1: decoupling two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor to obtain a mathematical model of the dual three-phase motor.

[0063] There is coupling between the two sets of windings of the dual three-phase motor. In order to obtain a better control effect, the two sets of windings need to be decoupled. The existing decoupling methods include dual dq decoupling and vector space decoupling. In this embodiment, the dual dq decoupling method is used to perform coordinate transformation on the two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor respectively, and obtain the decoupled dual three-phase motor equivalent mathematical model, which includes a voltage equation, a flux equation and a torque equation. The voltage equation, the flux equation and the torque equation are respectively:

[0064]

[0065] T e =3p[(L d -L q )i d i q +ψ f i q ]

[0066] Among them, u d1 、u d2 、u q1 、u q2 are the dq axis voltages of the two windings, i d1 、i d2 、i q1 、i q2 are the dq axis currents of the two windings, ψ d1 , d2 , q1 , q2 are the dq axis flux of the two sets of windings, ω e is the electrical angular velocity of the motor, ψ f is the permanent magnet flux, Ld , L q is the dq axis inductance, L dd , L dq is the d-axis mutual inductance and q-axis mutual inductance between the two sets of windings, T e is the electromagnetic torque of the motor, and p is the number of motor pole pairs.

[0067] The dual dq decoupling method is a commonly used decoupling technology in dual three-phase permanent magnet synchronous motor control. It mainly realizes the decoupling control of the motor by transforming the coordinates of the currents of the two sets of three-phase windings. Specifically, steps S11-S13 can be used.

[0068] Step S11: transform the currents of the two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor into two independent dq coordinate systems respectively.

[0069] The dual dq decoupling method first introduces two independent dq coordinate systems, which are used to describe the two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor. The selection of these two dq coordinate systems is usually based on the motor rotor flux, so that the AC component of the stator current can be converted into a DC component for easy control.

[0070] Then, through dq transformation, the two sets of three-phase stator currents are transformed into two independent dq coordinate systems respectively.

[0071] Step S12: In the dq coordinate system, the voltage equations of the two sets of windings of the motor are expressed as independent dq axis voltage equations respectively.

[0072] In this way, the voltage of each set of windings can be controlled separately, thereby achieving preliminary decoupling. In the dq coordinate system, the voltage equation is expressed as dq axis components in an independent manner, which can be controlled separately to independently adjust the voltage of the two sets of windings and reduce the coupling between them.

[0073] Step S13: Associating the flux equations of the two sets of windings with the corresponding dq axis current and inductance matrices respectively, decoupling the flux, and obtaining a mathematical model of the dual three-phase motor.

[0074] For each set of windings, the flux can be expressed as the product of the current and the inductance matrix. In actual motors, there is a certain mutual inductance between the two sets of windings, which will cause the flux equations to affect each other. By decoupling the dq current and flux, the torque equation is established to achieve independent control of the total electromagnetic torque.

[0075] Step S2: Based on the mathematical model, determine the initial controller parameters of the voltage outer loop and the current inner loop, and set the compensation coefficient.

[0076] According to the mathematical model of the dual three-phase motor, the motor torque can be controlled by controlling the q-axis current, and the motor magnetic field can be controlled by controlling the d-axis current. On this basis, the voltage outer loop can be set. First, the actual DC voltage value is obtained by sampling, and compared with the set DC voltage reference value to obtain the voltage error. The voltage error is input into the PI controller of the voltage outer loop for adjustment. The output of the PI controller is used as the q-axis current given value of the current inner loop to further control the motor torque.

[0077] In the current inner loop, the d-axis current reference value is fixed to 0. This is because the d-axis current mainly affects the magnetic field of the motor. Under this control strategy, the magnetic field remains unchanged to simplify the control process. The main task of the current inner loop is to control the q-axis current. The q-axis current given value generated by the voltage outer loop is used as the target value of the current inner loop. The actual q-axis current is adjusted by the PI controller to accurately track the target value to control the torque output of the motor. It should be noted that the given values ​​of the dq-axis currents of the two sets of windings must be the same at all times, ensuring that the d-axis and q-axis controls of the motor are independent of each other to avoid cross interference, thereby achieving effective decoupling control.

[0078] As for the current inner loop and the voltage outer loop, when the capacitor current compensation is not added, the initial controller parameters are obtained through steps S21-S23, so that when the current compensation is performed, the initial controller parameters are modified and adjusted to achieve voltage stabilization control.

[0079] Step S21: Determine controller parameters of the current inner loop according to the mathematical model.

[0080] The selection of current inner loop controller parameters needs to consider bandwidth, phase margin and dynamic performance. The bandwidth of the current inner loop is usually set high to ensure that the current can respond quickly to external changes. The phase margin is used to ensure the stability of the system. The dynamic performance can balance the response speed and system stability, which is achieved by selecting appropriate proportional and integral gains.

[0081] In a specific embodiment, the bandwidth of the current outer loop is set to 1 / 10 of the switching frequency, and the controller parameters of the current inner loop are:

[0082]

[0083] Among them, k id , k pd are the integral coefficient and proportional coefficient of the d-axis current controller, k iq , k pq are the integral coefficient and proportional coefficient of the q-axis current controller, R is the motor stator resistance, T s is the switching period, ω c is the cut-off frequency of the current inner loop.

[0084] Step S22: Obtaining the closed-loop transfer function of the current inner loop through the controller parameters of the current inner loop.

[0085] According to the mathematical model of the motor and the designed PI controller parameters, the open-loop transfer function of the current inner loop can be obtained. Then, the open-loop transfer function is substituted into the derivation formula of the closed-loop transfer function to obtain the closed-loop transfer function of the current inner loop.

[0086] According to the above controller parameters of the current inner loop, the closed-loop transfer function of the current inner loop and its simplified result can be obtained:

[0087]

[0088] Among them, k i is the integral coefficient of the current inner loop d-axis and q-axis controller, and S is the complex frequency variable.

[0089] The closed-loop transfer function describes the response characteristics of the actual current under a given current reference value.

[0090] Step S23: Obtaining initial controller parameters of the voltage outer loop according to the closed-loop transfer function of the current inner loop.

[0091] The main goal of the voltage outer loop is to control the DC bus voltage so that it stabilizes at the set value by adjusting the q-axis current reference value of the current inner loop. The closed-loop transfer function of the current loop describes the dynamic behavior of the current loop and can be used to analyze the response time and stability of the current loop.

[0092] The bandwidth of the voltage outer loop needs to be selected according to the actual DC voltage requirements, and the initial controller parameters of the voltage outer loop can be set according to the simplified current loop transfer function.

[0093] According to the above current inner loop closed-loop transfer function, the initial controller parameters of the voltage outer loop are set as:

[0094]

[0095] Among them, k p , k i are the integral coefficient and proportional coefficient of the voltage outer loop controller, ω cu is the cut-off frequency of the voltage outer loop, T is the equivalent time constant of the current inner loop, R L is the load resistance, and C is the DC bus capacitance.

[0096] It should be noted that if only relying on the voltage outer loop controller, it is impossible to generate fast and effective current instructions. Therefore, a capacitor current compensation link is added. First, the capacitor current value must be obtained, and then the compensation coefficient K is introduced.

[0097] like Figure 6 As shown, in this embodiment, the compensation coefficient K needs to be set, and the specific value of the compensation coefficient K needs to be determined according to the actual system conditions. Specifically, the value of the compensation coefficient K can be determined by the transfer function of the load disturbance signal. The transfer function of the load disturbance signal is:

[0098]

[0099] Among them, G I is the current inner loop closed loop transfer function, i L is the load current, U is the bus voltage, S is the complex frequency variable, C is the DC bus capacitance, T s is the switching period, k p , k i They are the integral coefficient and proportional coefficient of the voltage outer loop controller respectively.

[0100] As shown in the figure, based on the transfer function of the load disturbance signal, the anti-disturbance capability of the system facing a step disturbance signal is calculated under different K values, and then the appropriate value of the compensation coefficient K is determined according to the actual voltage requirements.

[0101] Step S3: collecting the voltage of the DC bus in real time, and calculating the capacitance current value of the DC bus.

[0102] There is usually no current sensor on the DC bus capacitor, so the capacitor current value needs to be calculated from the DC bus voltage using the capacitor current formula.

[0103] like Figure 5 As shown, the capacitance current value of the DC bus is expressed as:

[0104]

[0105] Among them, I c is the capacitor current value, T delay is the delay time between obtaining the voltage twice, and ΔU is the difference between obtaining the DC bus voltage twice.

[0106] Since the capacitor current is a reactive current, if T delay If the value is too small, the calculated current will fluctuate greatly, which will cause voltage fluctuation after compensation. delay If the value is too large, the load change cannot be reflected instantaneously and the system dynamic response cannot be accelerated. Therefore, it is necessary to select an appropriate T according to the actual voltage outer loop response speed. delay Note that T delay It cannot be greater than the time T when the current command reaches the required command without capacitor current compensation. If the capacitor current is negative, it means that the capacitor is discharged, the DC bus voltage drops, and the load change is a sudden load increase. According to the power expression of the dual three-phase permanent magnet synchronous motor, P = 3pω mψ f I q (ω m is the mechanical angular velocity), at this time, it is necessary to increase the q-axis current given value to increase the motor output power, thereby raising the DC bus voltage; similarly, if the capacitor current is positive, it means that the capacitor is charged, the DC bus voltage rises, and the load change is a sudden load unloading. At this time, it is necessary to reduce the q-axis current given value to reduce the motor output power, thereby reducing the DC bus voltage.

[0107] Step S4: Obtain the compensation amount of the q-axis current command according to the compensation coefficient and the capacitor current value of the DC bus voltage.

[0108] The compensation coefficient in step S2 and the capacitor current value calculated in step S3 are used to calculate the compensation amount of the q-axis current command, and the compensation amount is used to adjust the q-axis current reference value to cope with the fluctuation of the DC bus voltage.

[0109] Specifically, the capacitor current value is multiplied by the compensation coefficient K as the compensation amount, and the q-axis current command of the current inner loop output by the original voltage outer loop is used, and the compensation amount is subtracted to obtain the new q-axis current command value.

[0110] Step S5: According to the compensation amount of the q-axis current command, determine the transfer function of the voltage outer loop after adding the capacitor current compensation.

[0111] Based on the compensated q-axis current command, the transfer function of the voltage outer loop is recalculated. The compensated transfer function takes into account the influence of the capacitor current and can more accurately describe the dynamic behavior of the system.

[0112] Step S6: According to the transfer function of the voltage outer loop after adding capacitor current compensation, the initial controller parameters of the voltage outer loop are adjusted to obtain the final controller parameters of the voltage outer loop, and the motor is controlled by the final controller parameters of the voltage outer loop.

[0113] According to the voltage outer loop compensation transfer function obtained in step S5, adjust the initial controller parameter K p and K i , so that the response of the system in actual operation meets the design requirements. This step ensures that the compensated controller can effectively control the DC bus voltage and avoid overshoot or instability in the system.

[0114] In a specific embodiment, the open-loop transfer function of the voltage outer loop after adding capacitor current compensation is:

[0115]

[0116] Among them, G I is the current inner loop closed-loop transfer function, S is the complex frequency variable, C is the DC bus capacitance, Ts is the switching period, k p is the integral coefficient of the voltage outer loop controller, ω c is the cut-off frequency of the current inner loop, and K is the compensation coefficient.

[0117] like Figure 7 As shown, by analyzing the transfer function of the system, it can be obtained that at this time, the capacitor current compensation has already played an effect of accelerating the dynamic response of the system and increased the gain margin of the system. Therefore, appropriately increasing the voltage outer loop gain can further accelerate the dynamic response of the system and enhance the control effect of the system.

[0118] Through the adjusted final controller parameters, the voltage outer loop can stabilize the DC bus voltage under working conditions, ensuring the stability and efficiency of the motor operation.

[0119] In a specific example, MAXWELL and SIMPLORER are used for joint simulation. The simulation is set up as follows: Figure 8 As shown in the figure, the parameters of the dual three-phase permanent magnet synchronous motor used in the simulation are: pole pair number: 2, permanent magnet flux: 0.0693Wb, rated power: 250KW, rated speed: 18500r / min, stator resistance: 0.014ohm, d-axis inductance: 76.32uh, q-axis inductance: 84.88uH, bus capacitance is two 1600uF capacitors in parallel, totaling 3200uF, and target voltage is 540V. The simulation lasts for 50ms, with a load of 20% load at 0-10ms, 160% load at 10-30ms, and 20% load at 30-50ms.

[0120] According to the double dq decoupling method, the control of the dual three-phase motor is converted into the control of two parallel three-phase motors. The simulation is built as follows Figure 8 As shown in the figure. In the simulation, the q-axis currents of the two windings are given by the voltage outer loop, the d-axis current given values ​​are both 0, and the d-axis and q-axis current given values ​​of the two windings are the same. The switching frequency is set to 25000Hz.

[0121] Design the controller parameters of the current inner loop and the voltage outer loop. Select the current loop bandwidth as 1 / 10 of the switching frequency, and obtain the current loop controller parameters and the current loop closed-loop transfer function according to the bandwidth method. When calculating the voltage loop controller parameters, the current loop is equivalent to its simplified closed-loop transfer function. The voltage loop bandwidth is selected according to the actual voltage requirements and fine-tuned according to the simulation results. Run the simulation, observe the current command waveform output by the voltage outer loop when the load changes suddenly, and obtain the time T when the current command reaches the required command.

[0122] Design the capacitor current calculation part and select the appropriate delay time T delay The selected delay time cannot be greater than the time T obtained in step 2, otherwise the purpose of accelerating dynamic response cannot be achieved.delay For 3 switching cycles, the calculated capacitor current waveform is as follows Fig. 9 shown.

[0123] Derive the system transfer function and the transfer function of the load disturbance signal under different K values ​​(the load disturbance signal is the load current), draw the Bode diagram of the system transfer function and the step response of the load disturbance corresponding to different K values ​​in MATLAB, and determine the appropriate K value.

[0124] At this time, readjust the voltage loop controller parameters designed in step 2 to expand the voltage loop gain by 1.5 to 2 times. Use MATLAB to draw the Bode diagram of the system again to verify whether the system is stable at this time and select a larger voltage loop gain multiple while ensuring sufficient phase margin.

[0125] Run the simulation and observe the q-axis current command waveform and DC bus voltage waveform before and after adding capacitor current compensation. The current command waveform is as follows: Fig.10 As shown, the voltage waveform is Fig.11 As shown. Fig.10 , after adding capacitor current compensation, the current is more rapid. Fig.11 When capacitor current compensation is not performed, the voltage decreases by 86.85V when the load is suddenly added, and the voltage increases by 109.94V when the load is suddenly unloaded. After capacitor current compensation is performed, the voltage decreases by 61.87V when the load is suddenly added, and the voltage increases by 80.22V when the load is suddenly unloaded. In addition, the voltage recovery speed after adding capacitor current compensation is faster than before compensation.

[0126] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A voltage stabilization control method for a dual three-phase permanent magnet synchronous motor based on capacitor current compensation, characterized in that: The following steps are involved: S1 decouples two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor to obtain a mathematical model of the dual three-phase motor; S2 determines the initial controller parameters of the voltage outer loop and the current inner loop based on the mathematical model and sets the compensation coefficients; S3 collects the voltage of the DC bus in real time and calculates the capacitance current value of the DC bus; S4 obtains the compensation amount of the q-axis current command according to the compensation coefficient and the capacitance current value of the DC bus voltage; S5 determines the transfer function of the voltage outer loop after adding capacitor current compensation according to the compensation amount of the q-axis current command; S6 adjusts the initial controller parameters of the voltage outer loop according to the transfer function after adding capacitor current compensation to the voltage outer loop, obtains the final controller parameters of the voltage outer loop, and performs voltage stabilization control on the motor through the final controller parameters of the voltage outer loop.

2. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation as claimed in claim 1, characterized in that: In step S1, the mathematical model includes a voltage equation, a flux equation and a torque equation, and the voltage equation, the flux equation and the torque equation are respectively: T e =3p[(L d -L q )i d and q +ψ f and q ] Among them, u d1 、u d2 、u q1 、u q2 are the dq axis voltages of the two windings, i d1 、i d2 、i q1 、i q2 are the dq axis currents of the two windings, ψ d1 , d2 , q1 , q2 are the dq axis flux of the two sets of windings, ω e is the electrical angular velocity of the motor, ψ f is the permanent magnet flux, L d , L q is the dq axis inductance, L dd , L dq is the d-axis mutual inductance and q-axis mutual inductance between the two sets of windings, T e is the electromagnetic torque of the motor, and p is the number of motor pole pairs.

3. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation as claimed in claim 1, characterized in that: The step S1 comprises the following steps: S11 transforms the currents of the two sets of three-phase windings of the dual three-phase permanent magnet synchronous motor into two independent dq coordinate systems respectively; S12 In the dq coordinate system, the voltage equations of the two sets of windings of the motor are expressed as independent dq axis voltage equations; S13 associates the flux equations of the two sets of windings with the corresponding dq-axis current and inductance matrices, respectively, and decouples the flux to obtain a mathematical model of the dual three-phase motor.

4. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation as claimed in claim 1, characterized in that: The step S2 comprises the following steps: S21 determines the controller parameters of the current inner loop according to the mathematical model; S22 obtains the closed-loop transfer function of the current inner loop through the controller parameters of the current inner loop; S23 obtains initial controller parameters of the voltage outer loop according to the closed-loop transfer function of the current inner loop.

5. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation as claimed in claim 4, characterized in that: In step S21, the bandwidth of the current outer loop is set to 1 / 10 of the switching frequency, and the controller parameters of the current inner loop are: Among them, k id , k pd are the integral coefficient and proportional coefficient of the d-axis current controller, k iq , k pq are the integral coefficient and proportional coefficient of the q-axis current controller, R is the motor stator resistance, T s is the switching period, ω c is the cut-off frequency of the current inner loop.

6. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation as claimed in claim 5, characterized in that: In step S22, the transfer function of the current inner loop and its simplified result are: Among them, k i is the integral coefficient of the current inner loop d-axis and q-axis controller, and S is the complex frequency variable.

7. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation as claimed in claim 6, characterized in that: In step S23, the initial controller parameters of the voltage outer loop are: Among them, k p , k i are the integral coefficient and proportional coefficient of the voltage outer loop controller, ω cu is the cut-off frequency of the voltage outer loop, T is the equivalent time constant of the current inner loop, R L is the load resistance, and C is the DC bus capacitance.

8. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation as claimed in claim 1, characterized in that: In step S3, the capacitance current value of the DC bus is expressed as: Among them, I c is the capacitor current value, T delay is the delay time between obtaining the voltage twice, ΔU is the difference between obtaining the DC bus voltage twice, and C is the DC bus capacitance.

9. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation according to claim 1, characterized in that: The step S2 further includes determining the value of the compensation coefficient K according to the transfer function of the load disturbance signal, wherein the transfer function of the load disturbance signal is: Among them, G I is the current inner loop closed loop transfer function, i L is the load current, U is the bus voltage, S is the complex frequency variable, C is the DC bus capacitance, T s is the switching period, k p , k i They are the integral coefficient and proportional coefficient of the voltage outer loop controller respectively.

10. The voltage stabilization control method of a dual three-phase permanent magnet synchronous motor based on capacitor current compensation according to claim 1, characterized in that: The open-loop transfer function of the voltage outer loop after adding capacitor current compensation is: Among them, G I is the current inner loop closed-loop transfer function, S is the complex frequency variable, C is the DC bus capacitance, T s is the switching period, k p is the integral coefficient of the voltage outer loop controller, ω c is the cut-off frequency of the current inner loop, and K is the compensation coefficient.

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