Sizing of stationary energy storage systems for electric vehicle charging plazas

Abstract

Increasing numbers of electric vehicles (EV) and their fast charging stations might cause problems for electrical grids. These problems can be prevented by energy storage systems (ESS). Levelling the power demand of an EV charging plaza by an ESS decreases the required connection power of the plaza and smooths variations in the power it draws from the grid. In this article, a study of sizing of stationary ESSs for EV charging plazas is presented based on one year of data compiled from four direct current fast charging (DCFC) stations. Effects of the charging plaza size, grid connection power, and temporal resolution of input data on ESS requirements were studied. The ESS was controlled to reduce the connection power below certain limits which were altered from 5% to 100% with respect to the nominal power of the charging plaza. The charging plaza size ranged from 1 to 40 DCFC stations. The results show that the relative ESS power and energy requirements and the utilization rate of the ESS decrease, as the connection power and charging plaza size increase. The required connection power of an EV charging plaza can be decreased considerably by a relatively small ESS capacity. The effects of temporal resolution were studied, for the first time, by averaging the charging power time series of the charging plaza with averaging time intervals ranging from 1 s to 1 h. The temporal resolution of EV charging data had a notable effect on the results of ESS sizing: too sparse data distorts the results leading to an underestimation of ESS specifications and utilization.