A novel pilot protection for VSC-HVDC transmission lines based on parameter identification

The shunt large capacitor, on both sides of voltage source converter based HVDC (VSC-HVDC) transmission lines, will rapidly discharge to the fault point when a fault occurs. The system side can be equivalent to the shunt large capacitance in the fault component model. According to this characteristic of the VSC-HVDC system, a novel pilot protection scheme for VSC-HVDC transmission lines based on parameter identification is proposed in this paper. The protection principle can distinguish internal faults from external faults by identifying the capacitance on two terminals with the timedomain algorithm. The capacitance on two terminals can be accurately identified simultaneously when an internal fault occurs, while the capacitance at both ends cannot be accurately identified simultaneously when an external fault occurs. Therefore, a pilot protection criterion is constructed. The simulation results show that the protection scheme can distinguish internal faults from external faults reliably and quickly, and it is not affected by transition resistance, distributed capacitance of lines, and the control mode. In addition, the method can be implemented easily with simple computation and has certain practical value.