标题：Imbalance Mechanism and Balanced Control of Capacitor Voltage for a Hybrid Modular Multilevel Converter

作者：路茂增; 胡家兵; Zeng, Rong; Li, Wuhua; Lin, Lei

摘要：Due to different charging and discharging characteristics of full-bridge submodules and half-bridge submodules in hybrid modular multilevel converters (MMC), capacitor voltage imbalance will occur under boosted ac voltage or reduced dc voltage conditions. To address this issue, the mechanism of capacitor voltage imbalance is carefully studied, with three main factors—modulationindex,powerangle,andhybridizationratio— summarized and their effect on capacitor voltage imbalance analyzed.Further,acontrolstrategybasedonfundamentalfrequency reactivecirculatingcurrentinjectionisproposedtokeepthecapacitorvoltagebalancedinthehybridMMC.Theamplitudeandphase angle of the injected circulating current are calculated and their influence on the energy fluctuation in the submodules’ capacitors and the semiconductors’ current stress is explored. Experimental resultsunderboostedacvoltageandreduceddcvoltageconditions demonstrate the feasibility and validity of the proposed scheme.

发表于：IEEE TRANSACTIONS ON POWER ELECTRONICS

发表时间：JUL, 2018