Analysis of Battery Fault Tolerance in Modular Multilevel Converter with Integrated Battery Energy Storage System

Integrating batteries into modular multilevel converter (MMC) in a distributed manner improves the system reliability. For further reliability, MMC should also work normally in battery fault condition, which can cause serious unbalance of submodule power. In this paper, submodule voltage redistribution based method is proposed to balance submodule power. On the basis, a graphic method is proposed to study the system fault tolerance, which is mainly affected by the percentage of battery power, power factor and capacitor voltage balancing control method. Then an optimized control strategy with high fault tolerance is proposed. Finally, the analysis and control strategy is verified through MATLAB simulation.