Electric vehicle charging scheduling under local renewable energy and stochastic grid power price

In the paper, we consider delay-optimal charging scheduling of the electric vehicles (EVs) at a renewable energy aided charging station with multiple charge points. The uncertainty of the EV arrival, the intermittence of the renewable energy, and the variation of the grid power price are taken into account. In each period, the station determines the number of charging EVs during this period. Meanwhile, it also chooses the amount of renewables used for charging (the rest amount of energy will be purchased from the grid). The goal is to minimize the mean waiting time of EVs under the long-term constraint on the cost. We formulate a stochastic optimization problem, in which the charging EV number sequence and the allocated renewable energy sequence compose the two-dimensional optimization variable vector sequence, to investigate this scheduling problem. We derive the formal solution of the problem. Specifically, we prove that the optimal variable vector can be successively obtained: the optimal number of charging EVs is the solution of a reduced stochastic optimization problem and the greedy renewable energy allocation is optimal for given number of charging EVs. Finally, based on theoretical analysis, we propose two strategies for the problem and we investigate the proposed strategies numerically.