Direct torque control for five-phase induction motor drives with reduced common-mode voltage

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and the reduction in the total power per phase are required. This is possible thanks to the extension of modulation and control techniques to the multiphase case. However, the design of techniques to reduce the common-mode voltage (CMV) in multiphase drives is still under development. This work analyzes the CMV of a five-phase drive and proposes two direct torque control (DTC) strategies with reduced CMV. Elimination of certain switching states is proposed to obtain good torque and flux response as well as lower peak-to-peak CMV. The reduction of CMV is achieved at the expense of a small increase of the current distortion. Simulation results are provided to confirm the viability of the proposed schemes which reduce for five-phase induction motor drives the peak-to-peak CMV by 40% and 80% compared to the original DTC scheme.