The analysis of distance protection operation characteristics of power system based on VSC-HVDC interconnection

As the VSC-HVDC system has attractive advantages of high stability and controllability, it becomes a key development direction of the HVDC. Dynamic operation and controllability features of VSC-HVDC system differ a lot from that of conventional AC and DC transmission. During the grid fault, the VSC-HVDC export various short circuit current to AC system which can be a threat to the correct operation of distance protection. Based on the control principle of VSC-HVDC converter station, the voltage and phase features of the VSC-HVDC short-circuit current is analyzed. The measured impedance variation of the VSC-HVDC distance protection in AC side is also analyzed. The influence and interrelated factors of VSC-HVDC to distance protection are proposed. Digital simulation on PSCAD/EMTDC is done to verify the validity of the analysis.