A Bidirectional Isolated Charger for Electric Vehicles in V2G Systems with the Capacity to Provide Ancillary Services

The increasing penetration of electric vehicles (EVs) in the electrical grid creates the opportunity to make use of the battery chargers and Plug-in EVs as a distributed energy resource to provide ancillary services. In this paper, a comprehensive control strategy for a bidirectional isolated charger for EVs with the capacity to provide ancillary services is proposed. This approach advances towards the off-board three-phase smart chargers, which are able to support the grid during voltage and frequency variations by injecting active and reactive power. The proposed charger is based on a bidirectional three-phase voltage source converter followed by an isolated dual active bridge. Simulation tests are conducted, using a power electronic converter under different load and power conditions, to validate the effectiveness and applicability of the proposed control strategy. The results show that the adopted scheme simultaneously sets an active and reactive power on the grid side according to the commands received from the smart grid operator. This control strategy also enables the operation of the smart charger in four-quadrant and considers the state-of-charge of the EVs battery.