Robust sliding mode speed controller for hybrid SVPWM based direct torque control of induction motor

The conventional direct torque control (CDTC) is known to produce quick and robust response in induction motor drives. However, during steady state, torque, flux and current occur, which results in acoustical noise and incorrect speed estimations. The main objective of this paper is to present different hybrid space vector PWM (HSVPWM) methods for direct torque controlled induction motor for reduced inverter switching losses and the steady state ripple in torque, flux and current. The proposed PWM techniques are designed based on the notion of stator flux ripple, which is a measure of line current ripple. Expressions for RMS ripple, over a sub-cycle are derived and this analysis together with the total harmonic distortion (THD) performance of the different sequences is used to design HSVPWM techniques, which utilize the zero voltage vector redundancy that leads to clamping sequences. To validate the proposed method, the simulation has been carried out using MATLAB-SIMULINK and the results are presented. The simulation results verify the superiority of the proposed method to the conventional method.