A Regulated Electric Vehicle Charging Scheme in Coordination with Utility Pricing and Transformer Loading

Electric Vehicles (EVs) are becoming an integral part of the transportation fleet in many countries. They have substantially progressed to become a mainstream component of the smart electricity grid and are catalyzing changes in policies and regulations relating to power distribution systems. EVs represent distributed storage units whose load depends on the driving patterns and the battery charging characteristics. Random and uncontrolled EV charging has implications on both the network loading and the charging cost since time-based pricing is in effect for many utility companies. A well-managed charging system is thus important and must consider asset loading as well as time-varying tariff. This paper presents a regulated charging scheme that takes into account the charging cost which is reflective of both the transformer loading and the utility-level Time of Day (ToD) tariff. The task of finding a charging schedule that gives the least overall charging cost for the day has been formulated as an optimization problem for an actual distribution utility in India. The driving pattern was estimated based on a survey of EV owners plying in the utility license area. The results demonstrate how such a controlled charging scheme can save on the customers' money and help the utility manage its load curve by ensuring that the distribution transformers serving the EVs are not overloaded.