An investigation into the impact of electric vehicle load on the electric utility distribution system

The impact of electric vehicle charging on the energy and power demand is determined not only by the number of electric vehicles (EVs) in use and their usage pattern, but also by the number of EVs being charged at an instant and the charging profile of the battery module. Case studies that reveal several important issues regarding the impacts EV load may have on utility distribution systems are examined. First, it is not adequate to have only sufficient generation capacity during off-peak hours to assure a system´s ability to absorb EV loads without adverse effects. The constraints at the distribution level must be properly studied. Second, a sizable EV load can introduce a new peak in the early off-peak period. This may have scheduling implications and can completely throw any load management programs off balance. Third, at the present state of EV technology, including that of battery modules and chargers, a typical distribution system may not be able to supply EV loads beyond 20% penetration level. This constraint is created by the long (up to 12 hours) charging cycle of batteries