Virtual Vector based DTC with CMV Reduction for Five-Phase Induction Motor Drive

The common-mode voltage (CMV) is a significant problem for the two-level VSI fed motor drive because it causes winding insulation failure and bearing destruction. In this paper, the impact of CMV is studied using a five-phase two-level voltage source inverter (FPTL-VSI) fed five-phase induction motor drive. For FPTL-VSI, the CMV cannot be completely canceled out, but it can be reduced by using appropriate switching vector selection. In this paper, a Virtual Vector (VV) based direct torque control (DTC) method for near-constant switching frequency is developed to improve CMV. A CMV is reduced by 80% when compared to its peak value under the proposed VVDTC scheme. This technique analyzes the response of the resultant speed and torque of the voltage vector across a wide range of speeds using a volt-second balancing method. The high-powered FPIM drive laboratory prototype is used to validate the proposed controller experimentally over a wide range of speeds.