Low-speed Dynamic Performance Improvement Strategy For Pmsm Sensorless Control System

Permanent magnet synchronous motor(PMSM)has become increasingly popular in industrial drive field due to the advantages such as good dynamic performance,high torque inertia ratio,high torque current ratio an d flexible control.However,due to the reduction of system robustness and increasing of cost caused by position sensors,sensorless control schemes become a research hotspot.Generally,the dynamic performance of interior permanent magnet synchronous motor(IPMSM)drive will be degraded if adopting the position sensorless control mode,leading to the reduction of high-performance applications.The high frequency(HF)signal injection method can achieve sensorless operation in the lowand,zero-speed range,but the applying of digital filters degrades system bandwidth.Meanwhile,the inaccurate observation feedback or observer parameters,as well as the controller with poor dynamic quality degrade system stiffness.Therefore,this paper studies the improvement of bandwidth and stiffness of high frequency injection based sensorless control system.Based on the mathematical model of PMSM,the influence of non-ideal factors on the bandwidth of current-loop and speed-loop of sensorless control system is analyzed.The effect of position observer on the stability of the control system is analyzed under the condition of parameter mismatch.The removal of digital filter used for signal processing and the low-pass filter can improve the system bandwidth.In order to remove the digital filter to improve the bandwidth of the control system,a model prediction based high-frequency square wave injection sensorless control strategy is studied.From the temporal relationship of the injected voltage and the response current,the signal separation and rotor position error extraction control algorithm are simplified to remove the digital filter.Applying an improved rotor position observer,the speed feedback low-pass filter is removed while the observed speed is obtained with a smaller torque ripple.Based on the model prediction method,the predictive speed ahead of the observed speed is obtained,which is used as the speed feedback to enhance the dynamic performance of the system.In order to improve the stiffness of the control system,an active disturbance rejection control strategy based sensorless control scheme for IPMSM drive is proposed.The influence of system parameters and the bandwidth of the observer on the stiffness is analyzed.Considering the mathematical model of the state equation of the speed-loop active disturbance rejection controller,the extended state observer is used to observe and compensate the disturbance,and the nonlinear error feedback controller is used to obtain the feedback error fast and smoothly,which improve the robustness of the system.The parameter design methods of the extended state observer and the nonlinear error feedback controller are studied.Finally,based on the theoretical analysis and Matlab/Simulink simulation,the dynamic performance of active disturbance rejection control strategy based sensorless control scheme is verified on an IPMSM platform.The acceleration and deceleration experiment verifies the operating characteristics of the system.The current-loop and speed-loop bandwidth test verify the effectiveness of high bandwidth strategy.The stiffness test shows that the stiffness of the control system is improved.The studied strategy improves the dynamic performance of the system.