Impact of gradual increase in electric vehicle chargers in low voltage grids

Abstract: The presence of EV chargers in low voltage distribution grids increases through both public-usefacilities and at-home installations. EV charger grid impact studies are commonly focused onlarger installations such as fast-charging stations and charging pole arrays, or consider one or afew scenarios with respect to at-home EV charger amounts. In this study, a gradual increase inat-home EV chargers is instead examined. Their grid impact is assessed by viewing voltagelevels, voltage imbalances, voltage harmonic content and current harmonic content as functionsof the amount of EV chargers present in a grid. This is achieved by means of power flow andharmonic flow simulations with stochastic EV charger placements. Four different low voltagedistribution grids in Västerås are investigated, and average and worst-case scenarios (asrepresented by 95% confidence intervals) are examined. This way, it is ascertained how thecompounded grid impact of at-home EV chargers increases and at which point different powerquality regulations may be violated.The results indicate that there is a large difference between grids in the amount of EV chargersthat can be accommodated. Both voltage levels and voltage imbalances can be the limitingfactor with respect to regulation violations, while harmonic content is of little concern. The gridimpact of EV chargers is shown to depend on the power demand of the customers, and to differgreatly within the grid depending on its topology.