Direct Torque Control Scheme for a Nine-Phase Induction Motor With Reduced Current Harmonic

This paper discusses a modified Direct Torque Control (DTC) method in order to reduce phase current harmonic distortion in a nine-phase asymmetrical induction motor drive system. Since the classical DTC is a direct adaptation from the three-phase case, it does not take into account the presence of the non-producing torque current components obtained from the Space Vector Decomposition (SVD) technique. Thus, in classical DTC these non-producing torque components assume high amplitudes, causing distortion in phase currents. In this way, it is shown that modified DTC minimizes the undesired components, reducing significantly the distortion in phase currents while maintaining the fast dynamic response of classical DTC.