Optimal sizing of battery storage units integrated into fast charging EV stations

Abstract

The paper brings a mixed integer linear programming (MILP) solution for defining optimal size and operational strategy of battery storage systems (BSS) integrated with fast charging electric vehicle stations (FCS). The idea emerged as a solution for issues arising from strategies promoting installations of fast charging electric vehicle stations. Short, high power period peaks of fast charging increase the volatility of voltage in distribution networks and result in line congestions, requiring grid reinforcements by the distribution system operator (DSO). Additionally, transmission system operators (TSO) need to treat these power spikes, characterized by uncertainty of occurrence, by ensuring additional system flexibility. Coupling battery storage systems with FCS so that they serve as a buffer between the power system, reducing the stress of fast charging, and the electric vehicle (EV) users, providing the desired comfort in terms of charging speed, create multiple benefits for system participants. The results of the developed optimization model demonstrate that there is a feasible investment case for the proposed concept even in cases where only energy arbitrage is in place. Uncertainty aspects, such as unknown time of EV arrival or energy required by EVs, are considered for multiple locations where FCS are going to be installed.