Electric Vehicle Charging Stations Feeded by Renewable: PV and Train Regenerative Braking

At present, electric vehicles are charged at home at night when lower off-peak rates could apply. The purpose of this pilot project is to demonstrate the viability of providing renewable power charging services for electric vehicles at railway station parking lots for commuters during the day. The power needed to feed the charging station comes from a photovoltaic system as well as from the regenerative braking of a 25-kV AC railway traction system (RTS) and a 3-kV DC RTS. The design of the proposed DC microgrid for the charging station also involves an energy storage system (ESS) (battery of variable size and supercapacitor) and the connection to a secondary distribution network (SDR). The paper analyses the two most challenging technical issues: (1) the strategy of power management and converter control; (2) the impact of the size of the ESS. Although an increase in the size of ESS benefits the charge from renewable power, this increases the total investment inevitably. The smart strategy developed from power management, based on DC bus sensing, aims at maximizing the usage of available renewable power by mitigating the impact of charging station on the SDR.