A Novel Hybrid DC/DC Converter With Residual DC Fault Current Blocking Capability for All-DC Offshore Wind Farms

All-DC offshore wind farms have received extensive attention in recent years, but DC fault protection poses a significant challenge for their development. This paper proposes a novel hybrid DC/DC converter with fault current blocking circuit, which is capable of quickly suppressing the residual DC fault current to enable fast DC fault isolation using DC switches (DCSs). The fault clearance time is significantly reduced from around 500 ms to less than 14 ms, yielding quick system recovery. The operating principle of the proposed topology during normal operation and DC faults is elaborated and an enhanced power sharing control is also proposed to achieve DC voltage and current sharing among the modules of the proposed topology. In addition, the DC reactance of the proposed topology is significantly reduced by using interleaved control. The presented simulation results confirm the effectiveness of the proposed hybrid DC/DC converter and its control scheme in blocking circulating fault currents and facilitating DC fault ride-through using DCSs.