A Voltage-Based Controller for an Electric-Vehicle Charger

Electric vehicle (EV) integration into the distribution system has been a topic of great interest lately due to the potential challenges that it poses. Previous works have focused on either centralized charge control or distributed charge control to solve these issues. In this paper, an adaptive voltage-feedback controller for an onboard EV charger is proposed, which, unlike other proposed methods, requires no real-time communication between the EV and the utility. This controller compares the system voltage at the point of charging with a preset reference voltage. EV charging is reduced as the system voltage approaches this reference. The reduced charging rate takes into account the EV battery state of charge (SOC) and the owner's end-of-charge time (ECT) preference. To validate the proposed control structure, extensive simulations are carried out on a distribution system with and without other voltage control mechanisms. Simulation results show that this method can eliminate system voltage violations that would otherwise be caused by EV charging while ensuring fairness among the various EVs, even with different system configurations and EV penetration levels. The proposed controller shows good performance in the presence of other voltage control devices and distributed generation units. Moreover, it can integrate with vehicle-to-grid services as the lowest level of hierarchical control.