Common Mode Voltage reduction on three phase two-level Back-to-Back Converters

This paper addresses the challenge of commonmode voltage (CMV) generation in three-phase two-level back-to-back converters, which are a significant source of electromagnetic interference (EMI) in variable-speed drive (VSD) applications. The rapid switching in these converters often produces high CMV, inducing damaging shaft voltages in motor bearings and requiring costly EMI filtering to meet electromagnetic compatibility (EMC) standards. A novel pulsewidth modulation (PWM) strategies are proposed in two steps and evaluated to reduce CMV amplitudes without compromising inverter performance. These strategies operate by controlling the switching sequences of both rectifier and inverter, effectively limiting CMV to two distinct levels: $\pm \frac{2}{3} V d c, \pm \frac{1}{3} V d c$. Simulation results demonstrate significant CMV reductions for each method, validating their effectiveness and practical feasibility. This work provides a promising approach to improving the EMI profile of back-to-back converters used in industrial drives, high-voltageDC transmission, and renewable energy systems, with applications in electric vehicles and microgrids.