Active Disturbance Rejection And Sliding Mode Control Of Asynchronous Motor DTC System

In order to improve the torque and excessive flux ripple in the traditional direct torque control(DTC)speed regulation system,advanced control theories such as Active Disturbance Rejection Control(ADRC)and sliding mode control were applied to the DTC of induction motors,and a new control strategy was designed to effectively weaken the torque and flux ripple.The overall content is as follows:Firstly,the purpose and significance of this research as well as the research status of control methods of induction motors at home and abroad are described.Then the chapter arrangement and main research contents are briefly introduced.Secondly,the principle of traditional DTC based on hysteresis comparator and voltage vector switch selection table is introduced.The simulation experiment model is built and Matlab/Simulink software is used to complete the simulation experiment.Again,the ADRC and the principle of sliding mode control theory is expounded,in order to improve the dynamic response speed controller and enhance the steady state interference resistance,etc.,to adopt ADRC speed controller to replace the traditional PI controller,a new reaching law constitutes the torque and flux linkage of sliding mode controller instead of hysteresis comparator,and combining with the SVPWM technology driven induction motor.The comparative simulation experiment under Matlab/Simulink software environment shows that the control strategy can effectively reduce the torque,flux linkage and current pulsation of traditional DTC.Then,to improve the inherent chattering phenomenon of the traditional firstorder sliding mode,Super-twisting(St)and terminal sliding mode control principle is implied to make a Super twist controller and a non-singular terminal sliding mode magnetic chain and torque controller.Simulation results show that this control strategy has a fast response speed,and can effectively improve chattering and reduce the torque and current pulsation of traditional DTC.Finally,considering the traditional stator flux observation model,the induction motor is affected by the stator resistance change and the pure integrator when running at different speeds,which leads to the inaccuracy of flux estimation.Different modified stator flux observation models are designed to accurately estimate the stator flux changes.Existing in the practical control system for motor load is unknown and changeable situation,based on the theory of Super-twisting control design of the Super-twisting load torque observer as to reduce the uncertainty of the system,realize the precise control of the system.Simulation experiment results show that Super-twisting flux and torque observer can realize fast tracking and accurate observation.Finally,according to the loss model of induction motor under DTC and the relationship between steady state loss and stator flux linkage,electromagnetic torque and rotational speed,the optimal stator flux linkage under steady state is deduced,so that the efficiency of the motor can be optimized during steady state operation.The simulation results of Matlab/Simulink show that the loss can be reduced by the optimal stator flux linkage control method.In conclusion,based on the ADRC and sliding mode control theory,the design of the induction motor DTC system in reducing the torque and current ripple at the same time,has weakened the traditional sliding mode inherent chattering phenomenon,through different observer to enhance the precision of the motor control,and steady state operation can reduce losses,improve energy utilization,in the speed control system has good practical application value.