Submodule Open-Circuit Fault Detection For Modular Multilevel Converters Under Light Load Condition With Rearranged Bleeding Resistor Circuit

Fault detection is one of the important issues for the modular multilevel converter (MMC). However, few have studied the fault detection of MMCs under light load condition, where the faulty submodules’ (SMs’) capacitor voltages and healthy SMs’ capacitor voltages are almost close to each other in the faulty arm. This article analyzes the performance in detail of the MMC under switch open-circuit faults (OCFs), where the MMC works under light load conditions. And then, a rearranged bleeding resistor circuit (RBRC) based SM is proposed for fault detection in the MMC under light load conditions which can effectively detect the switch OCF based on the logical output of RBRC and the SM switching function. The proposed method can not only detect the fault in the MMC under light load condition, but can also detect the fault in serval microseconds. A 1.5-kW MMC prototype is built in the laboratory and the experimental results confirm the effectiveness of the proposed method.