A Low Common-Mode EMI Modulation Method for MMC Based on Phase-Compensated Carrier Phase-Shifted PWM

Modular multi-level converter (MMC) has extensive application prospect in voltage source converter based high voltage direct current (VSC-HVDC) transmission and high voltage motor drive. The existing MMC low common mode (CM) electromagnetic interference (EMI) modulation methods with excellent EMI suppression effect have the disadvantage of reducing the dc voltage utilization ratio to various degrees or increasing SM switching frequency. To solve this problem, this paper proposes a phase-compensated carrier phase-shifted PWM (PC-CPS-SPWM) for MMC to realize the low common-mode EMI, while the normal dc voltage utilization ratio and the number of SM switching times are the same as typical CPS-SPWM. Moreover, there is no increase in sampling frequency of the modulation signal, and it is suitable for MMC with the phase unit independent control. The mechanism of MMC CM EMI caused by modulation is introduced first. Then, the principle of the proposed PC-CPS-SPWM method is analyzed. Finally, the proposed method is validated by simulation results of MATLAB/Simulink.