Double Half-Bridge Submodule-Based Modular Multilevel Converters With Reduced Voltage Sensors

The half-bridge (HB) submodule (SM) based MMC requires a large number of sensors to measure capacitor voltages. In this letter, a double half-bridge (DHB) SM based MMC is proposed, where each SM consists of two HBs. But only one voltage sensor is equipped in each DHB-SM for capacitor voltage estimation, which is connected between positive poles of two capacitors in the DHB-SM. A capacitor voltage estimation method is also proposed, which can estimate capacitor voltages in the proposed MMC with only a half number of voltage sensors in comparison with HB-SM based MMCs. A DHB-SM based MMC prototype is built to verify the effectiveness of the proposed method.