Bidirectional EV charger integration into LV DC traction grid

Integration of bidirectional electric vehicle (EV) chargers into low voltage (LV) DC traction grids can potentially reduce chargers installation cost, as well as provide ancillary services for the DC grid, such as voltage stabilization, energy recuperation and reduced peak load. However, due to high LV DC grid voltage fluctuations and excessive load that EV chargers can create on a grid, their integration is challenging. In order to solve the problem, an EV charger connection scheme, converters parameters, as well as charger control algorithm must be considered wisely. This paper presents different connection solutions for bidirectional EV chargers integration into traction substations. A comparison of possible converter topologies that can be used in the system is made, depending on their efficiency, cost and applicability. Consequently, the system main parameters such as converters nominal power, voltage ratings and smart charging principle are presented. As a result, the proposed solution can be beneficial for developing EVs and public electric transport, which uses LV DC grids, such as trams/trolleybuses/metro.