A Virtual Vector Based DTC Scheme With Enhanced Resolution for Dual Inverter Fed Five-Phase IM Drives

A virtual voltage vector based direct torque control (DTC) scheme with enhanced resolution for five-phase induction motor (IM) drives with open-end stator windings, fed by two inverters, is proposed in this article. In the proposed scheme, the voltage space vector plane is divided into 20 sectors, by using 40 virtual voltage vectors produced as resultants of the virtual voltage vectors of the individual inverters thereby substantially increasing the sector resolution compared to the 10-sector based conventional five-phase DTC schemes. This DTC scheme incorporates a five-level hysteresis comparator for torque control and the required voltage vectors of different magnitudes are produced by appropriately combining the vectors of the two inverters. The increased sector resolution along with five-level hysteresis torque controller facilitates finer flux and torque control. As the effective common mode voltage in the motor windings is made zero in every switching period, both inverters can be connected to a common dc supply without causing circulation of zero sequence current. The proposed scheme is validated by performing experiment on a five-phase IM drive.