Research On Position Sensorless Control Technology Of Permanent Magnet Synchronous Motor In Full Speed Range

Permanent Magnet Synchronous Motor(PMSM)is widely used in electric transmission and servo system because of its small size,high power density and high efficiency.At present PMSM sensorless algorithm is mainly divided into two categories,one is suitable for zero,low speed,depending on the salient characteristics of the motor to achieve;The other kind is suitable for medium and high speed,depending on the fundamental frequency model of the motor.However,it is difficult for each single sensorless algorithm to meet the running requirements from static to rated speed due to the limitations of their respective mechanisms.Therefore,this thesis designs a hybrid algorithm combining the pulsed high-frequency voltage injection method and the sliding mode observer method to realize the sensorless control within the rated speed of PMSM.The main work is as follows:Based on the control strategy of i_d=0,the sliding mode observer method is studied for medium and high speed operation of PMSM.Aiming at the chattering and low-speed problems of the traditional sliding mode observer,an adaptive feedback gain sliding mode observer is designed.By introducing the feedback value of the estimated back electromotive force into the current observation equation and designing the adaptive rate reasonably,make amount of the equivalent control of sliding mode observer is no longer affected by rotation speed,and is equal to the ratio of the rotor permanent magnet flux linkage and the control coefficient.By selecting appropriate control parameters,better low-speed performance can be obtained.At the same time,it is convenient to design the sliding mode gain coefficient,avoiding the problem that the gain coefficient is too large and the low-speed chattering is serious,and the effectiveness of the improved method is verified by simulation and experiment.Aiming at the problem that the sliding mode observer method will fail at zero and low speed,this thesis studies the high frequency pulse voltage injection method to realize the motor start from zero speed to low speed.The problems existing in the traditional pulsed high-frequency voltage injection method are analyzed,and the filtering process and carrier signal recovery are improved respectively.In order to compensate for the estimated angular error caused by the inherent delay of the digital control system,a compensation method based on the current prediction method is adopted.Finally,the effectiveness of the predicted current control method for angle compensation is verified by simulation and experiment.The key to the hybrid algorithm is to select the speed switching interval and take appropriate switching methods.The selection basis of the speed switching interval is analyzed,and the optimal speed switching interval is obtained through experiments.A weighting algorithm is designed in the switching interval to avoid the situation of speed and position jump when the two algorithms transition.Finally,experiments show that the composite algorithm studied can realize the full range of position sensorless control of PMSM from low speed to rated speed.