Permanent Magnet Synchronous Motor Based On Improved Position Sensorless Research On Full-speed Domain Control Strategy

Permanent magnet synchronous motor is widely used in many different industries due to their simple structure,small size,high power density,fast dynamic performance and many other advantages.The position sensorless control technology overcomes the disadvantages of high cost and high complexity of traditional mechanical sensors,and increases the compactness of the system structure and the applicability in harsh environments.This thesis takes the innermounted permanent magnet synchronous motor as the research object,aiming to realize the accurate observation of the rotor position and speed in the full speed domain,and proposes corresponding solutions for some problems existing in the traditional position sensorless control method.In this thesis,the improved sliding-mode observer method is used in the mediumhigh-speed domain,and the improved rotating high-frequency signal injection method is used in the low-speed domain.The position sensorless control of the permanent magnet synchronous motor at full speed is realized by the hybrid control strategy.First,the superhelical function in the super-twisting sliding mode observer is used to replace the sign function in the traditional sliding mode observer,which effectively suppresses the chattering problem in the traditional sliding mode observer.Secondly,in order to suppress the pulsation phenomenon of the position observation error in the sliding mode observer,based on the analysis of the causes of the position error pulsation,a frequency adaptive complex coefficient filter is proposed to filter out the harmonics generated by the nonlinearity of the inverter.By this method,the pulsation phenomenon of the position observation error is suppressed,and the position observation accuracy is further improved.In addition,for the position observation error caused by the phase shift of the band-pass filter and the high-pass filter in the rotating high-frequency signal injection method in the low-speed domain,based on the principle of that high frequency positive sequence current response and high frequency negative sequence current response have the same phase deviation,a method of extracting the phase deviation value from the positive sequence component of the high-frequency current response is proposed,and then the position error angle is obtained by the arc tangent operation,so as to realize the precise compensation of the position error.Finally,the weighted average switching algorithm is used,and by setting a reasonable speed switching interval,the smooth switching of the two control methods in the low-speed domain and the medium-high-speed domain is realized,and the position sensorless control in the full-speed domain is realized.On the basis of theoretical analysis,in order to verify the effectiveness of the proposed strategy,the selected innermounted permanent magnet synchronous motor is experimentally verified on the Matlab/Simulink simulation platform.The rotor speed and position observation experiments under the three motor operating states of steady state,sudden speed change and sudden torque change were carried out respectively.Through the experimental results,it is verified that the proposed method can improve the position and velocity observation accuracy,and realize the position sensorless control in the full-speed domain.