A MILP Model for Coordinated Charging of Electric Vehicles in Smart Unbalanced LV Distribution Networks Using Floating Charge Method

In this paper, a mixed-integer linear programming (MILP) model is proposed to solve the charging problem of electric vehicles (EVs) using floating charge method meaning that the EV, could be supplied by each of the three phases connected to a special bus. In other words, unlike a usual household load which is only supplied by a particular phase, in the floating charge method it is assumed that each of the phases can supply the EV. Because of the importance of the loss reduction in the smart distribution networks, the active power loss is considered as the objective function of the proposed model. To evaluate the presented model, it is compared with two charging methods, namely uncoordinated and coordinated methods, using modified IEEE 31 bus distribution test system. The obtained results show that the proposed model, on one hand, decreases the total loss of the network and on the other hand, satisfies the voltage drop constraint in all of the considered cases adequately. Also, using the floating charge method, the system operator is able to improve the voltage magnitude of the neutral conductor.