Super-Twisting and Nonsingular Terminal Sliding Mode Direct Torque Control of Induction Motor Drives

This paper proposes a non-linear and robust Direct Torque Control (DTC) strategy for induction motor, which with Space Vector Pulse Width Modulation (SVPWM). In order to overcome the disadvantages of large torque and current ripple in traditional DTC of induction motor, Super-twisting (St) speed controller is designed to replace the traditional Proportional Integral (PI) controller. According to the induction motor's mathematical model and Nonsingular Terminal Sliding Mode (NTSM) control theory, a robust sliding mode controller based on torque error and stator flux squared error is designed. For the sake of estimating the load torque applied to motor precisely, as well eliminating uncertainties of the system, an observer based on Super-twisting algorithm is designed. Super-twisting stator flux observer is applied to improve the observation accuracy. Simulation results indicate that this control strategy can reduce torque and current ripple effectively, and has a strong inhibition effect on external disturbance, with good dynamic and steady performance.