A Lyapunov Optimization Approach to the Quality of Service for Electric Vehicle Fast Charging Stations

In this paper, an optimal power allocation strategy of a fast charging station (FCS) is presented to maximize the quality of service (QoS) of electric vehicle (EV) charging when the charging demand is greater than the available power at the station. In this regard, the problem is formulated in the form of a Lyapunov optimization problem that enables solving the problem online while eliminating the need for future information. The QoS is modeled through Jain’s fairness index to account for the charging time increase for each customer due to the power limit. Moreover, each EV’s demand is characterized by the amount of charging power. The power is calculated with the help of a second-order equivalent circuit model of the battery pack of the EV. Lastly, the problem is evaluated in a case study.