Novel pilot protection for AC transmission line connected to LCC-HVDC inverter station

Abstract

As known, after AC transmission line fault occurs, LCC-HVDC inverter station has three different statuses: no commutation failure, single commutation failure and continuous commutation failure. And the different statuses of inverter station could lead to wrong operation of traditional protection principles (such as current differential protection and directional pilot protection). Firstly, the paper establishes inverter station’s equivalent model under different statuses and analyzes relationship between voltage and current vectors. Secondly, the paper analyzes the adaptability of conventional protection principles including current differential protection and directional pilot protection. Thirdly, using empirical mode decomposition algorithm, novel pilot protection principle suitable for AC transmission line which is connected to inverter station is proposed. The novel protection principle is only based on power frequency current signal of two ends, and it requires no time synchronization system. Eventually, a PSCAD/EMTDC simulation model of ±800 kV LCC-HVDC and 500 kV AC transmission system is established. And the simulation results prove that the novel protection principle is immune to inverter station working status, fault resistance and fault type.