Optimal planning of Off-Grid Renewable Electric Vehicle Charging Stations based on Demand Side Management and Smart Charging

This paper presents a new planning scheme based on demand side management and smart charging for off-grid renewable based electric vehicle (EV) charging stations. The demand side section is driven by the data of the charging requests that are sent by the EV owners to the EV charging station central system which includes the arrival time, departure time, and requested energy. Also, the smart charging is based on delivering the requested energy to each vehicle in the charging station with minimum deviation from the designated amount of energy requested by each vehicle within the specified charging interval (between arrival and departure time) and by managing the power of each EV charger using open charge point protocol (OCPP). The developed smart charging scheme is able to distribute the available energy generated by the renewables and stored in the battery energy storage systems (BESS) between the available vehicles in the charging station with the goal of charging them in the time interval specified by the EV owners. This research also introduces a penalty policy for cases where the charging station is fined if it fails to deliver the specified energy to any vehicle. According to the demand side management and the smart charging scheme, the charging station central system specifies which vehicles can be admitted for charging according to the charging request they sent. This concept is used for sizing an off-grid renewable based charging station and the problem is formulated as a mixed integer linear programming (MILP) optimisation. In this research two types of chargers including fast chargers (7kW and 22kW) and rapid chargers (45kW and 75kW) are studied. The results illustrate the efficiency of the demand side management and smart charging scheme for managing an off-grid renewable based EV charging station, especially when dealing with low power chargers such as 7 kW chargers[AK4.1]. The results show that for the 7kW and 22kW chargers and preventing incomplete charging of vehicles (by considering high penalty coefficients) 58% and 70% of the requests are accepted[AK5.1]. The results indicate when incomplete charging is allowed (with a penalty of half the charging price per kWh) 67% and 72% of charging requests are accepted and the profit of these charging stations increase 16.8% and 0.9% respectively. For rapid chargers (45kW and 75kW), 85% and 87% of the vehicle requests are accepted respectively and for various penalties, almost all of them are charged completely.