DC fault blocking methods in DC transmission system for remote wind farms

Wind power technology has become one of the most promising renewable power generation technology. Due to the development of wind farms in remote and offshore areas, long distance power transmission is indispensable. Modular multilevel converter (MMC) is a promising ingredient to build a high voltage direct current system or for grid interconnection. However, before the converter system is constructed, the dc side fault blocking capability must be considered. This paper first introduces three categories of methods to achieve dc side fault isolation. Then, several existing topologies with dc side fault blocking capability are evaluated in this paper. The number of semiconductor devices and the conduction voltage drop are compared in this paper. After the comparison, the topology with the lowest cost and loss is chosen to verify the dc side fault blocking capability. The simulation result validates the dc side fault blocking capability of the converter system.