A High Step-up Ratio DC-DC Converter with Fault Blocking Capability for Offshore Wind Farms

Offshore wind farms with internal medium voltage (MV) DC collection buses have become a research hotpot. High voltage (HV) DC-DC converters interconnecting MV DC collection buses and HV DC transmission cables are necessary. Besides, the high cost of operation and maintenance makes fault blocking capability especially important. In this paper, a non-isolated high step-up ratio modular DC-DC converter (HSRM-DC) satisfying this specific condition is proposed, which characterizes high power, low cost and light weight. By blocking gating signals to IGBTs of all sub-modules (SMs) and triggering signals to all thyristors in the HSRM-DC, the rapid rising short-circuit fault current can be blocked within few milliseconds, which protects the HSRM-DC from thermal damage. Corresponding control strategy has been developed and a scaled-down prototype has been built in the laboratory to verify the effectiveness of the proposed HSRM-DC converter topology and its fault blocking capability.