Smart bidirectional charging for frequency support of a low-inertia vehicle-to-grid system in presence of energy storage systems

This paper focuses on the challenge to develop coordination between an electric vehicle (EV) charger, energy storage system (ESS), and smart charging/discharging strategy in a low-inertia grid-connected vehicle-to-grid system. Two smart bidirectional charging strategies are proposed to control EV and ESS for minimizing the frequency error by considering the EV constraints. A linear programming optimization algorithm with modified objective function is employed to design a smart charging technique for EVs. For ESS, three operating scenarios are assessed 1) without ESS, 2) with ESS, and 3) with ESS and considering the state of charge (SOC) drop. In the comprehensive charging strategy for ESS, the same LPOA designed for EV has been employed wherein EV SOC drop is observed to noticeably increase frequency regulation ability while the EV has a determined low SOC during a specified interval. The simulation results in MATLAB/SIMULINK environment validate the accuracy of these smart charging techniques.