Research On Position Sensorless Technology Of Permanent Magnet Synchronous Motor In Low-speed And Medium-high-speed Regions

The accuracy of the rotor position information acquisition is the key to achieving dual closed-loop vector control of permanent magnet synchronous motors and directly affects the performance of the overall control system.Rotor position information is usually obtained by installing a position sensor,but position sensors have the disadvantages of being expensive,resource intensive,easily damaged and less reliable,Therefore,the study of the estimation of rotor position information by software algorithms without the installation of position sensors has great practical application value.This paper presents a series of research works on position sensorless vector control of PMSM in the low and medium to high speed domains.Firstly,a detailed theoretical analysis of the coordinate transformation,the modulation principle of the SVPWM algorithm,the speed loop and current loop PI rectification parts of the vector control was carried out,a simulation model of vector control,current feed-forward decoupling control and maximum torque to current ratio control was built and the simulation waveforms were analysed in preparation for the subsequent work.The innovative content of this work is as follows:(1)In the low speed domain position sensorless control,for embedded permanent magnet synchronous motor position sensorless control has the problems of complex structure,difficult rotor position detection and cumbersome signal extraction.A new method is proposed which injects a high frequency square wave current signal onto the straight axis of an estimated synchronous rotating coordinate system,processes the high frequency response voltage signal in the stationary coordinate system by means of integral discretization,and finally designs a tangent phase locked loop to estimate the rotor position.Comparing the principle of pulse oscillation high frequency injection method,the proposed method has the characteristics of simple structure,eliminating the processing of feedback current,no filter used in the signal processing process,no need to judge the positive and negative of the injected signal and simple adjustment of the phase locked loop PI parameters,and the effectiveness of the method is verified by building a simulation model.(2)In the medium and high speed domain position sensorless control,the problem of severe jittering and large rotor position estimation error is addressed in the conventional sliding mode observer.A new exponential sliding mode function with continuity and exponential variation characteristics inside the boundary layer and saturation characteristics outside the boundary layer is provided,and the functional characteristics of the new exponential sliding mode function,switching function,exponential sliding mode function and saturation function are compared and analysed,and an adaptive law is designed to handle the higher harmonic components of the equivalent counter-electromotive force signal according to the counter-electromotive force model,and the stability of the system is analysed using Lyapunov theory The stability of the system is analysed and finally the method is experimentally validated with a 200 W permanent magnet synchronous motor.The experimental results show that the method has the characteristics of weakened jitter,smaller error in the estimated rotor position and smaller harmonic components of the equivalent counter-electromotive force.The design principles of some of the hardware circuits in the hardware platform used to validate the method and the software design in C on the CCS6.2 software platform are presented in Chapter 5.