Fractional Order Controller for DVR to Mitigate Torque Pulsations of an Induction Motor during Voltage Sags

In this study to enhance dynamic performance of DVR, a novel and an emerging control methodology 'fractional order PI (FO-PI) controller' with multi-loop control scheme is proposed to counteract the ill effects of torque peak/ pulsations of voltage sags on an Induction Motor. It is seen that the proposed controller, which tunes five (K-p, K-i, K-d, lambda and mu) independent parameters, provides a powerful and efficient framework to mitigate the effects of voltage variations on induction motor. For fine tuning gain and order of the FO-PI controllers a MATLAB toolbox FOMCON is used here. The simulation results show that the reliability and robustness of the DVR systems to mitigate the torque peaks/pulsations at the fault and recovery instants of an induction motor is greatly improved using fractional order controller. The control energy necessary to alleviate the effects of voltage sags on induction motor for the suggested FO-PI controller is found to be lesser, ensuring energy efficiency of the controller scheme. With FO-PI controller a reduction in time performance error indices viz. IAE, ISE, and per-cent THD is observed as compared to the present day PI controllers.