Sensorless direct torque control of induction motor based on hybrid space vector pulsewidth modulation to reduce ripples and switching losses-a variable structure controller approach

Abstract

The conventional direct torque control (DTC) has more ripples in steady state, which results in acoustical noise and incorrect speed estimations. The main objective of this paper is to present a scheme for direct torque control of induction machines using hybrid space vector pulsewidth modulation (HSVPWM) to reduce switching losses and the steady state ripple in torque and flux. The HSVPWM technique utilizes the zero voltage vector redundancy that leads to clamping sequences, which improves the performance of the drive at higher modulation indices. In order to avoid the problems with encoder, the speed is estimated by the model referencing adaptive system to extract the information of speed at shaft by using the motor terminal voltages and currents. In this paper a fuzzy based variable structure speed controller is designed to improve the speed performance. To validate the proposed method, the simulation has been carried out and the results are presented. The results of the simulation have been compared and are in good agreement with the published work.