Abstract：The floating capacitor voltage balancing control is one of the key issues in modular multilevel converter (MMC). Based on analysis of the redundant switching states of carrier disposition SPWM, the paper proposes a carrier-rotation strategy which reconstructs the corresponding relation between carriers and power modules by rotating carriers. The proposed strategy makes good use of redundant switch states to reduce charging and discharging time difference among floating capacitors, so as to realize the floating capacitor voltage balancing control. The simulation and experimental results show that the strategy is effective in eliminating voltage fluctuation of each floating capacitor and voltage difference among them.
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