A Multirate Multilevel Carrier Space Vector Modulation DTC Based IM Drive: A Novel Approach for Torque Ripple Minimization

This paper describes the implementation of multirate sampling technique for 3-level 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 for medium to high power applications. The benefit of the proposed multirate technique for 3-level 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. The 3-level inverter gives the smaller voltage steps lead to the production of higher power quality waveforms. This give superior performance compared to two-level inverters from the view point of lower common-mode voltage, lower harmonics in output voltage and current, and reduced voltage on the power switches Using simulation results relative merits of the multirate 3-level and single rate 2-level control strategy have been evaluated from the viewpoint of torque ripple minimization. The simulation results are experimentally validated.