Protection of VSC-multi-terminal HVDC against DC faults

Voltage-source converters (VSCs), by themselves, are defenseless against DC faults. Their anti-parallel diodes conduct as rectifier bridges to feed the fault. Their IGBTs (insulated gate bipolar transistors) are helplessly by-passed, unable to extinguish the fault current. This paper shows how a VSC-multi-terminal high voltage direct current (MTDC) transmission system can survive DC faults by a using protection scheme based on: (1) fast, reliable fault detection; (2) blocking of IGBT-circuit breakers (IGBT-CBs) and blocking of the IGBTs of VSCs; (3) locating of the faulted DC line; (4) isolation of the faulted DC line by economical fast DC switches; and (5) de-blocking of IGBT-CBs and IGBTs of VSCs to resume normal service.