High Frequency Square Wave Voltage Injection Based Anti-disturbance Control Strategy Of Sensorless PMSM Drives

With the promotion of permanent magnet synchronous motors(PMSM)and the upgrading of control theory,PMSM sensorless dirves are used in more and more occasions.However,how to obtain accurate rotor position without a position sensor has become the key to the system.When the motor is operating at zero/low speed,additional high-frequency signals have to be injected due to the reduction of the back EMF,which causes a series of problems.Therefore,how to improve the control performance in the PMSM sensorless drive has attracted the attention of many scholars and become a current research hotspot.In order to realize the improvement of the system dynamic performance and anti-disturbance ability under the zero/low speed operating conditions of the PMSM,this paper analyzes and studies the corresponding solutions.First,this paper adopts the high-frequency square wave voltage signal injection to increase the injection frequency,simplify the signal processing process,and improve the performance of the PMSM sensorless control system.Then,this paper analyzes and compares the rotor position error extraction methods in different reference frames based on the high-frequency current response,and finally adopts the amplitude extraction scheme under the measured reference frame.Besides,the position observer estimates the rotor position and speed.A third-order extended state observer with torque feedforward is used.At the same time,the observer transfer function is analyzed in the frequency domain.The parameter design of the linear extended state observer and the nonlinear extended state observer is deduced and verified under the given frequency domain index.Secondly,the limitation of the traditional low-pass filter on the current loop bandwidth of the PMSM sensorless drive is analyzed,and then a moving average filter with a simpler structure and better filtering effect is proposed.The filter can effectively replace the low-pass filter,increase the system bandwidth.Then the influence of traditional band-pass filter and low-pass filter on the performance of rotor position estimation is analyzed.According to the analysis of the high-frequency current response in the time domain,this effect can be improved by using the moving average filter with different sampling intervals,and the Bode diagram is used in the frequency domain to verify the substitutability of the proposed method.Subsequently,an integral-proportional(IP)control strategy in speed loop based on disturbance compensation is studied.First,the transfer functions of different controllers are compared and the corresponding applicable occasions are analyzed.The IP controller is adopted to eliminate the zeros in the transfer function of the speed loop,which suppresses the oscillation of the speed response under a given step.At the same time,the lumped disturbance to the system is calculated by disturbance observer,then,it serves as a feedforwards for the IP controller to improve the anti-disturbance performance and stiffness of the system.The efal function is used to broaden the scope of application of the disturbance observer.Then,the coupling between the parameters is eliminated by moving the proportional coefficient forward.Finally,the position sensorless control algorithm is achieved on the inverter platform based on the TMS320F28075 control chip,and the experimental verification is carried out on the 7.5kW PMSM experimental platform.