Research On Startup Based On Position Sensorless Of Permanent Magnet Synchronous Motor

Permanent Magnet Synchronous Motors(IPMSM)have the advantages of high efficiency,high power density,and good control performance,and are widely used in the industrial field.The permanent magnet synchronous drive system based on vector control requires accurate position information to be obtained in real time,and is currently acquired by a mechanical position sensor.The use of the mechanical sensor leads to problems such as reducing system reliability,increasing cost,and reducing anti-interference ability.Therefore,the position sensorless control strategy of permanent magnet synchronous motor has become a research hotspot.According to different speed grades,the position sensorless technology of PMSM is mainly divided into low speed(including zero speed)and medium and high speed.However,due to the low back-EMF during low speed operation,it is difficult to obtain accurate position information,making the motor fail to start with the maximum torque,even causing the starting to fail or reverse.Therefore,the position sensorless starting control of a permanent magnet synchronous motor has become a problem.In this paper,the following research is carried out for the starting control strategy of the sensorless permanent magnet synchronous motor system.The main contents are as follows:Firstly,the high-frequency(HF)mathematical model of permanent magnet synchronous motor is established,which lays a theoretical foundation for realizing the position sensorless starting control of the motor.Secondly,the two-step process of the permanent magnet synchronous motor without position sensor is introduced.The first is the rotor initial position identification,such as the high frequency signal injection method and pre-positioning method;the second is the constant starting current voltage,such as the magnetic field oriented control and reverse electromotive force closed loop method.In order to obtain accurate rotor position information,this paper studies a position sensorless control strategy based on high frequency square wave voltage signal injection.Firstly,this method uses a filterless signal processing method to extract the position error signal,and then obtains location information through the design position observation.At the same time,in order to improve the anti-disturbance performance of the system,an extended state observer(ESO)with strong robustness is proposed and parameters are adjusted.In order to solve the problems of rotor pole polarity(N/S pole)identification errors leading to start-up failure or inversion,a new rotor pole polarity identification method is proposed in this paper.Namely,applying a low-frequency sinusoidal current to the estimated d-axis,and compare the accumulation of the magnitudes of d-axis HF response current.This method is combined with the high-frequency square wave injection method to determine the initial position of the rotor.The experiment shows that the proposed method can accurately detect the initial position of the rotor when the motor is stationary and free-running.At the same time,By designing the current regulator and the speed regulator,the system start-up response performance is improved.Finally,on the sensorless vector control platform of the permanent magnet synchronous motor,the experimental results of the position sensorless control starting strategy proposed in this paper are verified by experiments.The experimental results show that the starting control strategy proposed in this paper is correct and effective,and the start response performance of motor system has been greatly improved.