Development of a decentralized smart charge controller for electric vehicles

Existing commercial battery charging posts for electric vehicles (EV) offer limited controllability and flexibility. These chargers are not designed to allow users to specify important criteria such as desired energy for next trip and waiting time whilst charging. In addition, the charging regime is not set to take into consideration the impact of charging (e.g. rate of charge) on the battery cycle life and the grid supply. With increased penetration of EVs and distributed generators (DG), complying with grid regulations will become more challenging, e.g. network voltage levels may deviate from the statutory limits. Moreover, as the battery is the most expensive part of an EV, consideration should be given to extending battery life and reduce the effective EV cost. Therefore, there is a need to develop a smart EV charge controller that can meet users’ requirements, extend battery cycle life and have minimum impact on the grid supply. In this paper, a smart controller is proposed which determines the optimal charging current based on grid voltage, battery state of health and user’s trip requirements. Models of a typical UK power distribution network and an EV battery (that allows simulation of battery aging process) are developed to investigate the performance of the “smart” charging system. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed controller.