A comprehensive AC side single line to ground fault ride through strategy of a modular multilevel converter for HVDC system

The AC side Single Line to Ground (SLG) fault is one of the most frequent faults in power systems. And, in an HVDC system based on modular multilevel converter it calls for the fault ride through strategy to transmit maximum possible electricity during the fault to secure power system stability. It presents different characteristics of SLG faults at the voltage regulator side and the power dispatcher side. In this paper a comprehensive fault ride through strategy for AC side SLG fault occurred at both converters of the HVDC system is proposed. The proposed method presents fast dynamics and promises maximum possible electricity transmission during the faults. Voltage fluctuation and current overshoot in transmission line during SLG fault can be fully suppressed by the proposed method. Moreover, the proposed control strategy is free of inter-station communication and secures the reliability of HVDC transmission system. Validity of the proposed method is verified by simulation of a ±200kV, 400MW point-to-point HVDC system (216 sub-modules per arm).