Improvement of DC Microgrid Voltage Regulation Based on Bidirectional Intelligent Charging Systems

In several cities, there are existing DC tram/subway grids. These existing grids in some cases cover a big part of the city and create the opportunity to install EV charging infrastructures. Such implementation could be built in order to contribute to the DC grid stability, enhancing the DC grid voltage regulation, through vehicle-to-tram concept. This can be reached with bidirectional DC/DC converters which enable energy transfer from vehicles to the DC grid to support such starts. Hereafter, the energy may flow normally from the grid to the vehicles. However, these improvements come with certain challenges in terms of power conversion, voltage regulation, grid coordination and intelligence. This paper defines the design principles of a tram DC-microgrid, which enables fast-charging, supported by fuzzy controllers that follow dynamically the overhead line voltages and the charging/discharging conditions of the proposed EV charging infrastructure. A discussion and conclusion about the practical applicability of the tram DC microgrid and its the complementarity with the EV charging infrastructure are demonstrated evaluating the results of DC-microgrid voltage regulation with the proposed methodology.