Influence of Electric Vehicle Charging Station Access on Distribution Network Relay Protection

The discharging behaviour of EV charging stations connected to the distribution network will undoubtedly bring unprecedented challenges to the traditional distribution network protection. When discharging to the grid as a distributed power source, the structure of the traditional distribution network will become a double-ended (multi-ended) power supply network. In the discharging state, the fault current output characteristics of EV charging stations are related to the control strategy of the converter, and the fault current output characteristics differ from those of the traditional power supply, resulting in the traditional protection of the distribution network not being able to meet the requirements. Therefore, it is necessary to analyse the impact of EV charging stations on relay protection to provide a basis for researching relay protection methods applicable to EV charging stations connected to the distribution network. In this paper, starting from the distribution network relay protection, the impact of charging station as a distributed source on the three-level current protection when different types of faults occur at different locations on the distribution network side is analysed by considering the discharge characteristics of the electric vehicle charging station.