A Smart On-Line Centralized Coordinated Charging Strategy in Residential Distribution Networks

Environmental and economic aspects encourage the transition of conventional fuel-based vehicles to electric vehicles (EVs). However, the uncoordinated charging activities of EVs may increase the stress on the distribution networks. Coordination between EVs charging activities is the perfect way to avoid the negative consequences of unscheduled charging activities without reinforcing the existing network infrastructure. Many previous works proposed coordinated charging strategies but without considering some influencing factors like EV departure time and energy tariff. Some others used impractical assumptions like a very large parking period or forced the users to choose the preferred charging period before the vehicles' arrival. In this work, a centralized coordinated charging strategy is proposed to reduce EVs charging costs from users' point of view side by side with the safe operation of the distribution network considering vehicle departure time and charging prices. The proposed strategy mainly determines the proper starting instant and the suitable charger power rate of the charging process. The proper starting instant of the EV charging process is calculated by ranking the charging priority of the arrived vehicles. In contrast, the charging power rate is estimated based on the available duration from starting instant to the instant of vehicle departure. The strategy is applied to a modified IEEE 31 bus residential distribution system with 22 residential distribution feeders. The results proved the proposed strategy's effectiveness in reducing the charging costs, alleviating overloading on the main substation, improving voltage deviations, and reducing the power loss.