Research On Direct Torque Control System Of Induction Motor Based On Flux Identification

Induction motor is widely used in theoretical research and practical application because of its simple structure,low cost,easy manufacturing,stable performance and so on.At present,the control system composed of induction motor and drive control circuit is widely used in the field of transportation,CNC machine tools and so on.Direct torque control(DTC)as a high-performance frequency control technology in the field of induction motor AC speed control has been studied in depth,especially the direct torque control and its control strategy has been concerned for low dependence on the parameters and fast response on the torque.However,the traditional direct torque technique uses pure integrator stator flux observer,the inevitable DC disturbance will lead to the accumulation of pure integrator error,thus reducing the accuracy of stator flux observation,affecting the stability of the entire system.At the same time,the traditional direct torque control technology in the low speed of the induction motor torque ripple and other issues greatly limit its application areas.At present,studying the new direct torque control technology to improve the accuracy of flux linkage identification and solve the problem of magnetic flux and torque ripple is imminent.In this paper,the induction motor drive system is used as the object of study.The extended Kalman filter(EKF)method is used to identify the stator flux linkage,and the on-line estimation of the stator flux based on EKF is studied deeply.The aim is to reduce the torque ripple of the motor drive system,To further improve the reliability and stability of induction motor direct torque control system.Firstly,the development of high performance control technology and the research status of direct torque control technology of induction motor are introduced.On the basis of constructing the mathematical model of induction motor,the principle and basic structure of direct torque control are expounded.And a method of identifying the flux linkage of induction motor based on extended Kalman filter is proposed.Secondly,this paper uses the graphical simulation tool Matlab/Simulink to build the simulation model of this scheme.The traditional direct torque control system and the direct torque control system based on EKF are simulated respectively to verify the superiority and stability of the flux linkage based on EKF.Finally,using TMS320F28335 to build control system experimental research platform,and execute the direct torque control system hardware design and software design.Simulation and experimental results show that the direct torque control of induction motor based on EKF flux linkage can effectively reduce the torque ripple and improve the control performance of induction motor.