A Method to Strength the DC Fault Current Limiting Capability of Arm Inductors of MMC

Limiting the dc fault current is an effective way to reduce the requirement of the dc circuit breaker (DCCB). Employing large dc side inductors to limit the dc fault current will affect the response speed of the system, while using converters to limit the dc fault current does not have this problem. The existing studies are focused on reducing the converter's dc voltage to limit the dc fault current. The dc fault current limiting capability of arm inductors is not utilized well yet. A method is proposed in this paper to strengthen the dc fault current limiting capability of arm inductors of modular multilevel converters (MMCs). When the proposed method is applied, the current path is changed, and arm inductors are series-connected to limit the dc fault current. The dc fault current limiting capability of arm inductors is significantly strengthened with the proposed method.