Full‐current‐based directional pilot protection for VSC‐DC distribution systems

Abstract

Line protection is of great challenge for Voltage Source Converter-Direct Current (VSC-DC) distribution systems because the protection scheme must selectively identify the fault section as fast as possible. This study proposes a full-current-based directional pilot protection to meet the above requirements. The proposed protection utilises the full-current (the measured current). The theoretical analyses, which have considered the influence of the VSC blocking, have proved that the full-current has a certain direction during a pole-to-pole short-circuit fault. Therefore, the protection is robust to the non-linearity of the DC system. The theoretical analyses have also pointed out that the protection is immune to the line-distributed capacitance. Both experimental and simulation results have demonstrated the analyses. The proposed protection can trip in <2 ms at a 1.6 kHz sampling rate in the experiments and within 1 ms at a 10 kHz sampling rate in the simulations. It can also correctly operate with 20 dB white noise and 20 Ω fault resistance. There is also no strict synchronisation requirement for the measurements of both the terminals. These features make the protection feasible for industry application.