Current Predictive Control System for Permanent Magnet Synchronous Motor

Abstract

A permanent magnet synchronous motor current prediction control system includes: a current command generation module, a current prediction control module, two coordinate transformation modules, and a position sensor. The position sensor collects the motor's rotor position signal and motor speed signal and sends them to the two coordinate transformation modules, the current command generation module, and the current prediction control module, respectively. The first coordinate transformation module generates a current feedback value based on the rotor position signal and outputs it to the current prediction control module. The current command generation module generates d- and q-axis current reference values based on the motor speed signal and outputs them to the current prediction control module. The second coordinate transformation module generates a command voltage in a stationary two-phase coordinate system based on the d- and q-axis command voltages from the current prediction control module and outputs it to a PWM inverter module to control the motor. The d- and q-axis command voltages are obtained by the current prediction control module based on a bus voltage sample value, a motor speed signal, a current feedback value, and the d- and q-axis current reference values fed back by the PWM inverter module. The present invention can effectively compensate for the nonlinear characteristics of the motor drive system, reduce current harmonics, improve output torque smoothness, and thus improve electromagnetic noise characteristics. It can also adapt to changes in prediction model parameters and maintain good control accuracy when the model parameters are disturbed.

Description

Technical Field

[0001] The present invention relates to a technology in the field of motor control, in particular to a current prediction control system for a permanent magnet synchronous motor. Background Art

[0002] Permanent magnet synchronous motor (PMSM) systems feature high control accuracy, high torque density, and excellent torque smoothness, and are widely used in new energy vehicle motor drive systems. To achieve optimal decoupling of torque and flux, PMSM drive systems typically employ vector control for current loop control. This involves transforming the three-phase current into quadrature and direct-axis current components in a rotating coordinate system and then controlling each component separately using a proportional-integral controller. However, due to nonlinear characteristics such as the inverter's dead zone and the forward voltage drop of power devices, the drive voltage generated by a vector control system can contain high-order harmonics. A closed-loop control system based solely on a proportional-integral controller struggles to effectively compensate for these nonlinear characteristics, resulting in high-order harmonics in the motor's phase currents. This can cause unexpected torque ripple in the motor's output electromagnetic torque and generate electromagnetic noise.

[0003] Model Predictive Control (MPC) can flexibly accommodate the nonlinear characteristics and constraints of complex control systems. As the performance of digital control systems improves, it has gradually become an emerging control method in the field of motor control. Model Predictive Control considers the impact of control parameters on system output based on a predictive model. Therefore, its control performance depends on the accuracy of system modeling. Model parameter mismatch will deteriorate control system performance and even cause system instability. Summary of the Invention

[0004] In response to the above-mentioned deficiencies in the prior art, the present invention proposes a permanent magnet synchronous motor current prediction control system, which can effectively compensate for the nonlinear characteristics of the motor drive system, reduce current harmonics, improve the output torque smoothness and thus improve the electromagnetic noise characteristics, and can adapt to changes in the prediction model parameters and maintain good control accuracy when the model parameters are disturbed.

[0005] The present invention is achieved through the following technical solutions:

[0006] The present invention relates to a permanent magnet synchronous motor current prediction control system, comprising: a permanent magnet synchronous motor drive control system comprising: a current instruction generation module, a current prediction control module, a first and a second coordinate transformation modules and a position sensor, wherein: the position sensor collects a rotor position signal and a motor speed signal of the motor and sends them to the first and the second coordinate transformation modules, the current instruction generation module and the current prediction control module respectively; the first coordinate transformation module generates a current feedback value according to the rotor position signal and outputs it to the current prediction control module; the current instruction generation module generates d-axis and q-axis current reference values according to the motor speed signal and outputs them to the current prediction control module; the second coordinate transformation module generates an instruction voltage in a stationary two-phase coordinate system according to the d-axis and q-axis instruction voltages of the current prediction control module and outputs it to a PWM inverter module to control the motor; the d-axis and q-axis instruction voltages are obtained by the current prediction control module according to a bus voltage sampling value, a motor speed signal, a current feedback value and a d-axis and q-axis current reference values fed back by the PWM inverter module.

[0007] The current prediction control module includes: two parallel feedback correction units, a voltage prediction unit, two parallel limiter units and a linear correction unit, wherein: the two parallel feedback correction units are respectively based on the d and q axis current reference values. and the current feedback value i d 、i q , after correction calculation, the corrected d and q axis current reference values i are obtained d_ref 、i q_ref , and sent to the voltage prediction unit; the voltage prediction unit is based on the corrected d and q axis current reference values i d_ref 、i q_ref and the current feedback value i d 、i q , and predict the initial command voltage based on the motor voltage model equation And send them to two parallel limiter units respectively; the two limiter units are respectively based on the initial instruction voltage After the amplitude limiting process, it is sent to the linear correction unit; the linear correction unit is based on the command voltage after the amplitude limiting process and the sampling value U of the bus voltage. dc , after linear correction calculation, the final command voltage is generated The command voltage is sent to the PWM inverter module after coordinate transformation, generating a drive voltage to drive the motor.

[0008] Technical Effects

[0009] The present invention effectively compensates and corrects the nonlinear characteristics such as the dead zone effect of the inverter and the conduction voltage drop of the power device in the motor vector control system, while avoiding the adverse effects of model parameter mismatch on the performance of the predictive control system.

[0010] Compared with the existing technology, the present invention can compensate for the nonlinear characteristics of the motor drive system, reduce current harmonics, significantly improve the electromagnetic noise characteristics, and maintain good control accuracy when the motor parameters change; through limiting and linear correction calculations, it further avoids the disturbance of command and feedback signals affecting the stable operation of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of a permanent magnet synchronous motor drive control system;

[0012] Figure 2 This is a schematic diagram of the current prediction control unit;

[0013] Figure 3 A flow chart of the current feedback correction system used in the embodiment;

[0014] Figure 4 The waveform of the motor dq axis current when no feedback correction is taken;

[0015] Figure 5 This is the waveform of the motor's three-phase current when no feedback correction is taken;

[0016] Figure 6 This is a schematic diagram of the motor phase current harmonic analysis results when no feedback correction is taken;

[0017] Figure 7 This is a diagram showing the motor dq axis current waveform when the current prediction control system of the present invention is used;

[0018] Figure 8 The three-phase current waveform of the motor when the current prediction control system of the present invention is adopted;

[0019] Figure 9 Schematic diagram of the motor phase current harmonic analysis results when the current prediction control system of the present invention is adopted. DETAILED DESCRIPTION

[0020] like Figure 1As shown, the permanent magnet synchronous motor drive control system involved in this embodiment includes: a current command generation module 201, a current prediction control module 202, first and second coordinate transformation modules 204, 203 and a position sensor 207, wherein: the position sensor 207 collects the rotor position signal and motor speed signal of the motor 206 and sends them to the first and second coordinate transformation modules 204, 203, the current command generation module 201 and the current prediction control module 202 respectively; the first coordinate transformation module 204 generates a current feedback value according to the rotor position signal and outputs it to the current prediction control module 207; the current command generation module 201 generates d-axis and q-axis current reference values according to the motor speed signal and outputs them to the current prediction control module 207; the second coordinate transformation module 203 generates a command voltage in a stationary two-phase coordinate system according to the d-axis and q-axis command voltages of the current prediction control module 207 and outputs it to the PWM inverter module to control the motor; the d-axis and q-axis command voltages are obtained by the current prediction control module according to the bus voltage sampling value, the motor speed signal, the current feedback value and the d-axis and q-axis current reference values fed back by the PWM inverter module.

[0021] like Figure 2 As shown, the current prediction control module includes: feedback correction units 101 and 102, voltage prediction unit 103, limiter units 104 and 105, linear correction unit 106, wherein: feedback correction units 101 and 102 are respectively based on the d and q axis current reference values Current feedback value i d 、i q , after correction calculation, the corrected d and q axis current reference values i are obtained d_ref 、i q_ref , and sent to the voltage prediction unit 103; the voltage prediction unit 103 is based on the corrected d and q axis current reference values i d_ref 、i q_ref and the current feedback value i d 、i q , and predict the initial command voltage based on the motor voltage model equation And send them to the limiter units 104 and 105 respectively; the limiter units 104 and 105 respectively according to the initial instruction voltage After the amplitude limiting process, it is sent to the linear correction unit 106; the linear correction unit 106 calculates the command voltage after the amplitude limiting process and the sampling value U of the bus voltage. dc , after linear correction calculation, the final command voltage is generated The command voltage is sent to the PWM inverter module after coordinate transformation, generating a drive voltage to drive the motor.

[0022] The feedback correction units 101 and 102 use a moving average filtering method to perform feedback correction, specifically as follows: Figure 3 The corresponding expressions are as follows:

[0023]

[0024] in: is the d and q axis current reference value, i d_ref 、i q_ref is the corrected d and q axis current reference value, i d 、i q is the d and q axis current feedback value, N represents the sampling time, j is the sampling step, k j is the filter coefficient, k c is the correction factor.

[0025] In this embodiment, k0=0.85, k1=0.05, k2=0.05, k3=0.05, k c =1.

[0026] The motor voltage model equation is:

[0027]

[0028] in: is the initial command voltage, i d_ref 、i q_ref is the corrected d and q axis current reference value, i d 、i q is the d and q axis current feedback value, R s , L d , L q 、 are the phase resistance, d-axis inductance, q-axis inductance and permanent magnet flux parameters of the motor, ω e Indicates the motor speed, T s is the sampling time interval. In this embodiment, T s =100us.

[0029] The linear correction is calculated as:

[0030] in: is the d and q axis command voltage, is the initial command voltage U dc is the sampling value of the bus voltage, min() is the minimum value function, k m is the modulation coefficient. In this embodiment,

[0031] The coordinate transformation is to transform the d and q axis command voltages output by the linear correction unit 106 into Transformed into the command voltage in the stationary two-phase coordinate system The three-phase current i of the motor is sent to the PWM inverter module 205, and the coordinate transformation module 204 converts the three-phase current i of the motor into a 、i b 、i c Transformed into d and q axis current feedback values i d 、i q Sent to the current prediction control module 202; the PWM inverter module receives the command voltage After modulation, a three-phase driving voltage is generated to drive the motor 206 to output electromagnetic torque to drive the load to operate.

[0032] In this embodiment, the dead time of the PWM inverter module is 2 μs.

[0033] like Figures 4 to 9 As shown in the figure, at time t=0, the motor accelerates from rest to 1000rpm, and at t=0.5s, the load is suddenly added.

[0034] like Figures 4 to 6 As shown in the figure, there are current waveforms and harmonic analysis results when no feedback correction is taken and only predictive control is adopted. It can be seen that due to the existence of the inverter dead zone effect, the dq axis current fluctuates, the corresponding phase current is also distorted, and there is an obvious high-order harmonic distribution in the current.

[0035] like Figures 6 to 9 Figure 2 shows the operating results of this system. It can be seen that the dq axis current is more stable and the content of various high-order harmonics is significantly reduced. Combined with the above results, it shows that this system can effectively compensate for the nonlinear characteristics of the motor drive system, reduce current harmonics, and improve electromagnetic noise characteristics.

[0036] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A permanent magnet synchronous motor current prediction control system, characterized in that: include: The permanent magnet synchronous motor drive control system includes: a current command generation module, a current prediction control module, a first and a second coordinate transformation module, and a position sensor, wherein: the position sensor collects the rotor position signal and the motor speed signal of the motor and sends them to the first and the second coordinate transformation modules, the current command generation module, and the current prediction control module respectively; the first coordinate transformation module generates a current feedback value according to the rotor position signal and outputs it to the current prediction control module; the current command generation module generates d-axis and q-axis current reference values according to the motor speed signal and outputs them to the current prediction control module; the second coordinate transformation module generates a command voltage in a stationary two-phase coordinate system according to the d-axis and q-axis command voltages of the current prediction control module and outputs it to the PWM inverter module to control the motor; the d-axis and q-axis command voltages are obtained by the current prediction control module according to the bus voltage sampling value, the motor speed signal, the current feedback value, and the d-axis and q-axis current reference values fed back by the PWM inverter module; The current prediction control module includes: two parallel feedback correction units, a voltage prediction unit, two parallel limiter units and a linear correction unit, wherein: the two parallel feedback correction units are respectively based on the d and q axis current reference values. 、 and current feedback value 、 , after correction calculation, the corrected d and q axis current reference values are obtained 、 , and sent to the voltage prediction unit; the voltage prediction unit is based on the corrected d and q axis current reference values 、 and current feedback value 、 , and predict the initial command voltage based on the motor voltage model equation 、 , and sent to two parallel limiter units respectively; the two limiter units are respectively based on the initial instruction voltage 、 , and then send it to the linear correction unit after amplitude limiting processing; the linear correction unit calculates the sampling value of the command voltage and bus voltage after amplitude limiting processing. , after linear correction calculation, the final command voltage is generated 、 , the command voltage is sent to the PWM inverter module after coordinate transformation, which generates a driving voltage to drive the motor; The feedback correction unit uses a moving average filtering method to perform feedback correction, specifically: ,in: 、 is the d and q axis current reference value, 、 is the corrected d and q axis current reference value, 、 is the d and q axis current feedback value, N represents the sampling time, j is the sampling step, is the filter coefficient, is the correction factor.

2. The permanent magnet synchronous motor current prediction control system according to claim 1, characterized in that: The motor voltage model equation is: ,in: 、 is the initial command voltage, 、 is the corrected d and q axis current reference value, 、 is the d and q axis current feedback value, 、 、 、 They are the phase resistance, d-axis inductance, q-axis inductance and permanent magnet flux parameters of the motor, Indicates the motor speed, is the sampling time interval.

3. The permanent magnet synchronous motor current prediction control system according to claim 1, characterized in that: The linear correction is: ,in: 、 is the d and q axis command voltage, 、 is the initial command voltage is the sampling value of the bus voltage, min() is the minimum value function, is the modulation coefficient.

4. The permanent magnet synchronous motor current prediction control system according to claim 1, characterized in that: The coordinate transformation process is to transform the d and q axis command voltages output by the linear correction unit into 、 Transformed into the command voltage in the stationary two-phase coordinate system 、 Send to PWM inverter module, coordinate transformation module converts the three-phase current of the motor 、 、 Converted into d and q axis current feedback values 、 Sent to the current prediction control module; the PWM inverter module receives the command voltage 、 After modulation, a three-phase drive voltage is generated to drive the motor to output electromagnetic torque to drive the load.

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