DC-Link High-Frequency Current Ripple Elimination Strategy for MMCs Using Phase-Shifted Double-Group Multicarrier-Based Phase-Disposition PWM

The active circulating current suppression may cause high-frequency current ripple in the dc link of modular multilevel converters (MMCs). In this article, a phase-shifted double-group multicarrier-based phase-disposition pulsewidth modulation strategy is proposed to eliminate the dc-link high-frequency current ripple of MMCs, where the fundamental frequency component and the second-order component of the arm reference are modulated, respectively, by two groups of carriers. By shifting the phase angles of double-group multicarrier in each carrier period, the high-frequency current ripple injected into the dc link of MMCs can be eliminated. The proposed strategy not only eliminates the dc-link current ripple, but also extends the active and reactive power region of MMCs in comparison with the existing method. Simulation and experimental studies are conducted, and their results verify the effectiveness of the proposed strategy.