An improved Fault Current Limiter for self-clearing MMC-based dc distribution network

Considering the investment cost and operation safety, an improved fault current limiter (FCL) for dc distributed network based on self-clearing converters is proposed in this paper. Before self-clearing converters being blocked, dc fault current can be automatically limited, which provides enough time for selective protection to identify fault lines and reduce the action speed requirements on mechanical switches. During normal operation, the proposed FCL does not deteriorate the transient response characteristics of dc system. The circuit design, control strategy and protection are simple. The threshold values on the voltage, current and capacity of power electronic devices are low, which greatly reduces the cost and conducting loss, because the power of dc reactor is divided from the dc cable.