Research On Wide Speed Range Sensorless Control Strategy Of Permanent Magnet Synchronous Motor

Permanent Magnet Synchronous Motor(PMSM)is widely used in various fields of military and civil industry due to its many advantages such as high efficiency,high reliability and small size.Traditional PMSM control requires the installation of mechanical sensors,but these mechanical sensors are expensive and easily damaged.In order to solve these problems,this thesis combines high-frequency signal injection and sliding mode control and other sensorless control theories,with the goal of realizing PMSM wide-speed sensorless control.Through coordinate transformation,the mathematical model of PMSM is simplified and analyzed,and vector control is established.The model lays the foundation for the follow-up research on sensorless control.In the low-speed domain,the high-frequency signal injection method is adopted for sensorless control.Aiming at the problem of inaccurate estimation of the initial position of the rotor,a method based on the magnetic circuit saturation salient pole effect is proposed.Observation,to correctly judge the magnetic pole polarity.Simplify the design of the filtering link,and make the difference between the stator current and the extracted high-frequency component of the stator current,and the fundamental frequency component is fed back to the current regulator for current closed-loop control.Through simulation analysis,the feasibility of the designed pulsating high frequency voltage injection method is verified in the zero and low speed range.In the medium and high speed domain,the sliding mode observer method is adopted for sensorless control.Aiming at the problems of chattering,phase delay and steady-state error,the switching function in sliding mode control is replaced with a continuous smooth saturation function sigmoid.And design a moving average filter phase-locked loop(MAF-PLL)based on feedforward velocity input to accurately estimate position and velocity.Through simulation analysis,the feasibility of the designed sliding mode observation method in the medium and high speed domain is verified.In order to realize PMSM wide-speed range sensorless control,a speed switching algorithm is designed.The switching algorithm adopts the speed weighting method,and its weighting factor adopts the variable boundary saturation function sigmoid to calculate,which can avoid the interference caused by the intervention of another algorithm in the early stage of switching of a certain algorithm.In order to weaken the interference of the injected voltage signal to the sensorless algorithm in the middle and high speed stage,an attenuation function is designed to gradually reduce the injected voltage to zero to ensure the stability of the switching process.Through simulation analysis,the results show that the method combines the advantages of the low-speed domain pulse high-frequency voltage injection method and the medium-high-speed domain sliding mode observation method,and realizes the sensorless compound control in the wide-speed range of PMSM.