An Improved Direct Torque Control of Three Level Dual Inverter fed Open-Ended Winding Induction Motor Drive Based on Modified Look-Up Table

In this project, Induction Motor (IM) drive with Direct Torque Control scheme (DTC) turns prominent for industrial applications. However, it retains disadvantage of high torque ripples. The conventional look-up table for DTC scheme is structured with selection of reverse voltage vectors (VVs) when flux and torque errors crosses lower hysteresis boundary condition. 

This consequences higher torque ripples and increase in switching frequency. In this paper, modified look-up table for DTC of three-level dual Voltage Source Inverter (VSI) fed Open Ended Winding IM drive is proposed, where the VVs selection for lower hysteresis boundary conditions of torque and flux are restructured with null voltage states. 

The selection of suitable null voltage switching states from the various possible combinations of dual inverter switching's is based on minimization of switching state transitions. To nullify flux instability at zero speed, proper active VVs are placed at hysteresis flux +1 and torque 0 condition in modified look-up table. These overall effective modifications in proposed DTC scheme enjoys the benefits of reduction in torque ripple, switching frequency and stable flux maintenance. The MATLAB simulations and practical investigations are conducted for existing and proposed DTC schemes.

Keywords: Direct Torque Control (DTC), Open-Ended Winding IM (OEWIM) drive, Modified Look-Up table.