Probabilistic Modelling of EV Charging Impact on the Sub-transmission Grid

Transport electrification in Sweden is moving at a fast pace. Grid impact studies from EVs predominantly consider low-voltage grids. However, as the share of electric cars is rapidly increasing, potential grid impact at higher voltage levels needs to be considered. This paper presents a probabilistic approach to generate aggregated charging profiles for home charging at a sub-transmission grid level. The charging profiles are based on the best available data for the study area of Skåne in southern Sweden. The study shows how charging behaviour considerably impacts the height and time of the daily peak loading from home charging. The results from the probabilistic load flow simulation show how aggregated home charging at low voltage levels will in some cases affect the sub-transmission grid, with an average increase of substation loading of up to 72%. 11 out of 85 substations do not have enough capacity to feed the simulated home charging.