A Novel Zero/Reduced Common-Mode Voltage Modulation Scheme for a Dual Three-Phase Motor Drive System in Full Modulation Span

Common-mode voltage (CMV) is one of the major concerns in modern motor drive systems using pulsewidth modulation (PWM) controls. To alleviate the CMV issue, a series of different PWM methods have been proposed. However, due to the physical limits of the three-phase structure, none of those reduced-CMV PWMs (RCMV-PWMs) can fully eliminate the CMV. As the motor phases have been extended to even numbers, such as six phases, opportunities to eliminate the CMV by a proper modulation scheme emerge. This article proposes a new modulation method to fully eliminate or reduce the CMV for the full modulation span of a dual-three-phase motor drive system, thereby helping to shrink the CM filter. Mathematical models are built indicating its effectiveness of eliminating the CMV in the linearity range of the modulation index and reducing the CMV in the overmodulation range. Simulation results along with experiments implemented on field-programmable gate array controlled dual inverters validated the effectiveness of the proposed control algorithm.