Impact of Electric Vehicle Charging on Low Voltage Network Stability

The global shift of vehicular transportation from conventional cars to electric vehicles present yet another challenge for the power utilities in meeting the growing demand for Electric Vehicles (EV). Large penetration of electric vehicles can have numerous impacts on the electric grid if left unaddressed. This paper presents the assessment of the impact of EV charging on the electricity distribution network at different penetration levels. A model of an existing electricity distribution network of Thimphu, the capital city of Bhutan was developed in DIgSILENT power factory simulation software. The impact of EV charging on the existing electricity distribution network was analysed based on three hypothetical assumptions, current status-quo, low uptake level, and high uptake level. The impacts were evaluated on two key parameters, the voltage stability, and the transformer loading. The load flow simulation indicated that a low voltage violation was triggered even at a low penetration level of 0.28% and the maximum penetration level is attained at 37.68% where the whole system is likely to breakdown due to severe voltage collapse on the distribution system. Based on the simulation results, a mitigation technique for voltage correction has been discussed.