7 kW Converter Prototyping for EV Charging Network Development Supplied through Rail Traction Power Systems

― Electric vehicle (EV) charging is expected to impose a high loading demand on distribution systems in near future due to its fast-growing market. This will lead to an urgent need of expensive upgrades on distribution networks if no alternative energy supply is provided. Rail traction power networks benefit from substantial reserve capacity which can be used for this purpose. This paper reports on design, laboratory prototyping, and experimental testing of a 7 kW power electronic converter prototype which can be used for EV charging network development using a single-phase supply emulating AC traction system. The prototype consists of a single-phase voltage source converter (VSC) connected back to back via a DC link, to three half bridge VSCs feeding the charging network. The prototype enables connection of both single-phase and three-phase EV chargers while ensuring balanced three-phase output voltages from the grid forming converter. The converter also offers the possibility of power injection from its DC bus which is useful in DC rail traction application. Additionally, it supports reverse power flow from charging network towards traction substation which is advantageous for voltage support and improved stability of the traction network. Detailed design of main converter components is presented. Experimental results confirm the feasibility and appropriate performance of the studied converter.