Impact of unbalanced electric vehicle charging on low-voltage grids

During the past years, the rising market penetration of electric vehicles (EV) has gained significant attention due to its influence on power system stability. Voltage unbalances caused by single-phase charging EVs and plug-in hybrid electric vehicles (PHEV) becomes a major power quality issue in weak low voltage grids. Therefore, this paper presents an asymmetric power flow calculation analyzing the impact of EVs and PHEVs on voltage stability. The advantages of the developed methodology is shown in three use cases. The use cases analyses a generalized low voltage grid and daily load profiles, which depict single and three phase components such as households, heat pumps, photovoltaic systems and electrical vehicles. The impact of EVs and PEVs are presented comparing a reference case to a future scenario with a high penetration of them. The results show that asymmetric EV/PEV charging cause significant voltage unbalances that exceed the allowed voltage limits of 2 %.