Asynchronous motor direct torque control based on the sliding mode variable structure

Aimed at the problems of larger torque ripple and non-constant inverter switch frequency in the direct torque control for asynchronous motor, this article puts forward a new idea. In same words, the idea is that the traditional PI controller is replaced by speed controller of sliding mode variable structure (SMVS). What´s more, according to the mathematical models of induction motor in synchronous rotation coordinates and control theory of sliding mode variable structure, a new variable structure sliding mode controller based on torque and flux errors is proposed. Using the reference voltage vectors which are the outputs of the controller, the switching control signals of the inverter are generated by space vector PWM(SVPWM) technology. The simulation research verifies that the proposed control scheme reduces torque and flux ripple significantly, ensures the inverter switching frequency to be fixed, and it also has strong robustness to motor parameter and disturbance.