Torque ripple minimization in direct torque control based induction motor drive using optimal multirate sampling technique

This paper describes the implementation of multirate sampling technique for carrier space vector pulse width modulation based direct torque control (CSVPWM DTC) of induction motor (IM) drive with an objective to reduce the electromagnetic torque ripple. The benefit of the proposed technique for CSVPWM DTC based IM drive; it gives lower torque ripple as compared to single rate sampling technique. In multirate sampling technique, for the same digital signal processor, two sampling periods are used. The fundamental sampling period which is smaller than the sampling period used in single rate sampling technique, is used for data capturing and estimation of speed, torque and flux parameters. The other sampling period which is an integer multiple of the fundamental sampling period, is used for speed, flux and torque error processing and also for the implementation of CSVPWM algorithm for synthesizing gate pulses. Further, due to lower fundamental sampling period in multirate sampling technique better resolution in switching pulse widths can be obtained. Using simulation results relative merits of the multirate and single rate control strategy have been evaluated from the viewpoint of torque ripple minimization. The simulation results are experimentally validated.