Study on bi-directional energy transfer of EV charging station on micro-grid operation

This paper proposes a micro-grid structure of EV charging station, which combined with new energy sources and energy storage. The core bi-directional converters DC/DC and AC/DC are introduced, with their principles and control strategies detailed. Among them, a kind of current limited closed-loop control strategy is adopted to control DC/DC, while double-loop control strategy of voltage outer inductor current inner adopted to control bi-directional AC/DC when that works as a rectifier, double-loop control strategy of voltage outer inductor current inner adopted to PQ control inverter, and double-loop control strategy of voltage outer capacitor current inter used to Droop control inverter. Corresponding simulation platform has been built on the Simulink, the results of which show that the system can realize the bi-directional energy transfer technology fast and stably in the grid-connected mode, and also operate stably and supply power reliably in the single-islanded mode. It is of practical reference value to the designing and engineering implementation of a new style of electric vehicle charging station.