Open-Circuit Fault Detection Method for Full-Bridge Modular Multilevel Converter Sub-Modules

The full-bridge modular multilevel converter (FBMMC) has received widespread attention. The open-circuit fault (OCF) of full-bridge sub-module (FBSM) may lead to catastrophic failures of the whole system. For the sake of guaranteeing the steady operation of FBMMC, a method for detecting OCF is proposed in the paper. Based on the analysis of FBSM operation and its OCF characteristics, the paper proposes an OCF detection method. Due to the distinct FBSM port voltage characteristics, the method enables fast and accurate detection by the inconsistency between the FBSM port voltage and switching signal. The paper only measures the port voltage, and the capacitor voltage is obtained through logical operation without extra sensors. The simulation results verify the correctness and effectiveness of the method.