Influence of HVDC commutation failure on directional comparison pilot protection of AC system

Several incidents of transient power converse due to the interaction of AC/DC system have been reported recently, and the incidents result in the malfunction of directional comparison pilot protection (DCPP) and the miss-trip of vital AC transmission lines. Taking Jingling-Echeng HVDC and its connected inverter side AC system into account, the corresponding electromagnetic transient simulation model is established in PSCAD/EMTDC based on the operating environment of a mal-operation incident. The response characteristics of HVDC system and the fault features of AC system are studied in this paper while faults occur at the inverter side AC system on the basis of the analysis of the real recorded fault data. Results show that the rapid response of HVDC results in the malfunction of DCPP while AC fault occurs. The mechanism of transient power converse and the variations of AC fault features are analyzed. The corresponding measures are also proposed.