Research On Torque Pulsation Suppression For Permanent Magnet Synchronous Motor Based On Nonlinear Compensation

The permanent magnet synchronous motor has many advantages,such as high efficiency,small bulk,light quality,fine characteristic etc.With the development of high-performance permanent magnet materials and the improvement of manufacturing technology,permanent magnet synchronous motor have been widely used in various applications,such as electrical products,traffic and transportation,industrial equipments,national defense,e.g..Although permanent magnet synchronous motor has many advantages,there are still some problems as an emerging technology.One of which is torque pulsation.Permanent magnet synchronous motor is powered by voltage source inverter(VSI).The nonlinear distorted output voltage of the VSI produces the distortion of motor phase currents and enhances the motor loss.The current measurement errors can be equivalent to the reference current commands,and it can produce the control errors of currents,so the current measurement errors also produces torque pulsation.In addition,the inherent cogging torque of permanent magnet synchronous motor also gives rise to torque pulsation.The objective of this paper is to study the effective control strategies to reject the torque pulsation caused by nonlinear distorted output voltage of the VSI,current measurement error and cogging torque.The major works implemented in this paper are presented as follows:(1)According to the mechanisms of the system's disturbances,modeling the models of the system's disturbances.These models are the model of the nonlinear distorted voltage of the VSI,the model of current measurement errors,and the model of cogging torque.Given the system extended error model which is equivalent to permanent magnet synchronous motor drive system based on the cascaded PI control strategy.The theory analysis of torque pulsation for permanent magnet synchronous motor based on PI controller under the action of nonlinear distorted output voltage,current measurement errors and cogging torque is given.(2)In order to overcome the nonlinear distorted voltage of the VSI and the inherent one cycle input delay of digital controller,a novel adaptive predictive proportional-integral-resonant current control strategy for permanent magnet synchronous motor is proposed.The proposed method can predict the control errors of the currents and the nonlinear distorted voltage of the VSI when the resistor and inductance of the motor are unknown.Then,the predicted variables are used to execute the feedback control to compensate the system input delay and the nonlinear distorted voltage of the VSI.(3)In order to overcome the cogging torque and nonlinear distorted voltage of the VSI,an integral continuous fractional function sliding control with adaptive compensator control strategy is proposed.The proposed method substitutes the switching function of the conventional sliding control with continuous fractional function to suppress the output chattering phenomenon of the conventional sliding control.The robustness of sliding control can be used to suppress the nonlinear distorted output voltage of the VSI.Meanwhile,the adaptive compensator can ease the burden of the gains of the sliding controller and enhance the robustness to the cogging torque.(4)In order to overcome the nonlinear current measurement error in the surface mounted permanent magnet synchronous motor drive system,a composite proportional-integral speed controller is proposed.The nonlinear q-axis current measurement error is equivalent to the nonlinear load current,so the speed ripple caused by the nonlinear current measurement error can be suppressed by the proposed nonlinear compensator.Meanwhile,the integral model predictive control is introduced to reject the zero-current clamping phenomenon and to enhance the currents control accuracy.