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

摘要

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 the capacitor voltage estimation, which is connected between the 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 three-phase MMC is simulated with power systems computer aided design/electromagnetic transients including DC (PSCAD/EMTDC) and a DHB-SM-based single-phase MMC prototype is built in the laboratory. Both the simulation and experimental results confirm the effectiveness of the proposed method.