Reduced torque ripple and switching frequency using optimal DTC switching strategy for open-end winding of induction machines

This paper presents an optimal switching strategy to minimize torque ripple and switching frequency for Direct Torque Control of induction machines. In this proposed method, two inverters are connected to the terminals of open-end windings of an induction machine. By doing so, number of voltage vectors is greater same as available in three-level multilevel inverters. The most optimal voltage vectors will be used to improve DTC performances, i.e. reduced torque ripple and switching frequency. The identification of the vectors are based on operating conditions, specifically by examining the behaviors of torque error and switching frequency of error status produced from the hysteresis controllers. It can be shown that, the proposed optimal switching vectors according to the operating conditions can reduce the rate of change of torque and hence minimize torque ripple and switching frequency. The improvements offered in the proposed method were verified through experimental results.