Research On DTC Optimization Of PMSM Based On Sliding Mode Observer

Permanent magnet synchronous motor(PMSM)has been widely applied in social production especially in the electric vehicle industry,because of its high power density,high efficiency and good speed regulation performance.Direct torque control(DTC)has great advantages such as simple structure and rapid torque response,which has been widely concerned and studied in recent years.At the same time,there are also shortcomings of high torque and flux ripple and poor performance at low speed.Therefore,how to suppress the torque ripple has always been the focus of academic research.In this paper,some problems of stator flux observation and suppression of torque and flux ripple in the direct torque control of permanent magnet synchronous motor are studied.Firstly,this paper summarizes the development history of the AC motor drive technology and the research status of direct torque control technology at home and abroad.This paper introduces the basic structure,coordinate transformation and mathematical model of permanent magnet synchronous motor,and expounds the basic principle and implementation process of direct torque control technology.On this basis,there are analyzed the reasons for the large flux and torque ripple: the characteristics of the torque hysteresis loop and the flux hysteresis loop determine the existence of the ripple.Secondly,aiming at the problem of large torque and flux ripple,it designed a method based on sliding mode observer combined with duty cycle modulation to optimize direct torque control from the perspective of control strategy.On the one hand,the sliding mode observer is used to improve the observing accuracy of stator flux,and verify its convergence by using Lyapunov stability theorem.Using the concept of effective flux to establish the extended state observing equation to reduce the dependence on motor parameters.Based on the concept of effective flux,the extended state observation equation is established to reduce the dependence on motor parameters.On the other hand,calculating the duty cycle according to the variation of torque and flux,which reduces the flux and torque ripple.Through the comparative analysis of MATLAB/Simulink software modeling and simulation,the results show that the proposed control strategy can effectively suppress the torque and flux ripple.Finally,it is built that the experiment platform of PMSM driving technology by using dSPACE and Typhoon hardware-in-the-loop simulation system.The experimental test of PMSM-DTC optimal control scheme based on sliding mode observer and duty cycle modulation is carried out by using the experimental platform.The experimental results show that the improved control system can accurately observe the stator flux and significantly reduce the torque and flux ripple,which verifies the accuracy of the control scheme in this paper.