A Novel Modular Multilevel Converter with Single Bridge Arm Per Phase for Size Reduction

This paper proposes a novel modular multilevel converter (MMC) with a single bridge arm per phase (SBA-MMC). In the conventional MMC, only half of the sub-modules (SMs) will be inserted at any moment and the other half are bypassed, causing insufficient utilization of the converter components. To solve this issue, in the proposed SBA-MMC, the corresponding SMs in the upper and lower arms share a common dc capacitor, which therefore reduces the number of capacitors by half. In addition, this topology enables a higher capacitor charging / discharging frequency, and thus can greatly mitigate the capacitor voltage ripples. In addition, this paper proposes a modified nearest level modulation (NLM) method specially for the SBA-MMC. Simulation results from both the proposed SBA-MMC and the conventional MMC verify the functionality and superior performance of the proposed SBA-MMC.