Smart DC node to recharge electric vehicles from PV power, electric railway systems and secondary distribution network: Assessment of fault currents

A multi-terminal dc node consists of voltage-source converters (VSCs) and dc-dc converters (DC-DCCs) is presented in this paper as promising topology to feed electric vehicle (EV) charging stations from renewable power. The research focuses on the detailed analysis of the characteristic behaviour of node currents under dc faults, and in particular its natural response, which can produce particular protection requirements. Thus, the protection system design is presented based on the use of solid state and ultra-fast hybrid dc circuit breakers, associated with converters, which monitor local quantities to detect and isolate dc faults. The results show that an overcurrent derivate-based scheme can be adopted from available devices to meet the fast required response.