A Single-Ended Protection for Multi-terminal Flexible DC Distribution System

Abstract

Because the power electronic components in the multi-terminal flexible DC power distribution system have poor ability to withstand fault current and different voltage levels affect each other, it is required the protection accurately remove the fault area within a few milliseconds after severe DC faults occur, so it is of great significance to study the rapid protection of multi-terminal flexible DC distribution systems. The existing protection method based on single-ended transient current measurement is greatly affected by the transition resistance, and the system branch is complicated, which makes it difficult to identify fault areas. Therefore, based on the fault characteristics of different fault locations under different voltage levels, the waveform changes characteristics of current and voltage are analyzed. Further, the law of energy conservation is used to analyze the voltage waveform variation range after the fault, and the voltage and current waveform changes are combined to form a comprehensive criterion for protection, and finally the fault area is quickly removed by the DC circuit breaker. The simulation results of PSCAD/EMTDC proves the proposed method can quickly and effectively identify the fault area.