Enhanced Voltage Switching States for Direct Torque Controlled Open End Winding Permanent Magnet Synchronous Motor Drive

Abstract

Direct torque control (DTC) is most popular technique used in industries for adjustable speed of drives. It has simple control algorithm without any pulse width modulation technique and vector transformations involvement. Two level voltage source inverter (VSI)-fed permanent magnet synchronous motor (PMSM) operated with DTC has higher torque and flux ripple problems due to the limited voltage vectors availability, which affects the performance of drive. To alleviate these problems, more number of voltage space vectors should be available for DTC of PMSM drive. In this article, DTC for open-end winding PMSM drive (OEW-PMSM) is proposed. A two level dual VSI-fed OEW-PMSM drive configuration attains three level inversion with an equal dc link voltage to VSIs. Similarly four level inversion can also be attained with an unequal dc link voltage of 2:1 ratio given to dual VSIs. Therefore availability voltage space vectors are increased for PMSM drive operation. The effective voltage switching tables for DTC operated OEW-PMSM drive at different speed conditions are proposed to make its performance more satisfactory, thus achieving less torque and flux ripples and also reduced common mode voltage (CMV). To validate this, Simulink/MATLAB and real time experimentation are performed on 3.7 kW PMSM drive.