Design considerations for DC charging station for plug-in vehicles

This paper looks at the optimizing the electric vehicle supply equipment (EVSE) design for level 3 DC charging stations. By studying the power demand of the charging station, we conclude that the size of the grid tie can be reduced substantially by sizing for average rather than the peak power demand. Therefore the charging station architecture with a single AC/DC conversion and a DC distribution to DC/DC charging units is proposed. An energy storage system connected to the DC bus is used to supply power when the demand exceeds the capability of the grid tie. Specifically, this paper looks at the integration of energy storage on the DC bus to (1) provide power to the chargers in instances when their requirements exceed the grid tie capability (2) eliminate DC side ripple and (3) eliminate AC side harmonics.