A DC fault clearance method for series multiterminal HVDC system

The DC line fault current clearance for series MTDC is discussed in this paper. A new method is proposed to increase the availability of the series MTDC system during DC line faults and decrease the dependency on telecommunication. In the proposed method, the DC lines in the series MTDC system are divided into several different protection zones. The DC faults at any low voltage DC lines can be cleared with the coordinated control of the converter stations adjacent the fault line while the DC power transmission at other DC lines are remained to some extent; for DC faults at high voltage DC line, although the power transmitted at the fault pole during the DC fault reaches zero, the emergency power support between inverters is possible. The DC fault clearance speed is fast because the telecommunication among the converters in the fault pole isn´t needed. The validity of proposed method is verified by simulation results.