Torque ripple reduction in direct torque control based induction motor drive using novel optimal controller design technique

In the present work a novel strategy for optimum design of flux and torque controller for carrier space vector pulse width modulation based direct torque control (CSVPWM DTC) of induction motor (IM) drive has been implemented. Two positive and one negative torque slope levels per half the switching period has been predicted for CSVPWM DTC IM drive based on which a new optimal control strategy is proposed for the design of flux and torque controllers where, a P controller is used in the flux loop and a PI controller is used in the torque loop. Performance investigation shows that optimally tuned controllers used in CSVPWM DTC technique are helpful in reducing torque ripple. In proposed control strategy flux and torque slopes are derived using d-q axis induction motor model in stationary reference frame. These slope parameters are respectively utilized to find the transfer function (TF) of flux and torque loops. Using these TF, flux P and torque PI controller settings are obtained such that they give the best results in terms of reduced torque ripple for any flux and torque slopes. In order to show the superiority of the proposed control strategy for CSVPWM DTC IM drive over conventional DTC technique, comparison of simulation and hardware results are presented.