A Novel Online Charging Algorithm for Electric Vehicles Under Stochastic Net-Load

Abstract

In this paper, we propose a novel charging algorithm for electric vehicles (EVs) in smart grids. Unlike traditional charging methods, this algorithm is designed to exploit the flexibility of the EVs’ load to absorb the unforeseen fluctuations in the net-load caused mainly by the intermittency of the renewable energy sources (RES) (wind energy). In this paper, we first formulate the problem with traditional charging algorithms in the presence of RESs. Second, we show that the overall energy consumed by the overall load in the system can be estimated ahead of time despite the stochastic behavior of the net-load. Third, a detailed description of our online algorithm shows how EVs’ charging decision is taken by the utility server in real time—not ahead of time—according to the current situation of the net-load. Also, unlike most of the charging algorithms in literature, our proposed algorithm considers keeping the charging current constant, thus, imposing less technical and engineering requirements and complexity on the EVs’ charging infrastructure. Finally, to test the performance of our online charging algorithm, a tool has been developed in Java to simulate our algorithm. A comprehensive performance evaluation of our algorithm against a traditional ahead-of-time charging algorithm shows clear improvements achieved by our algorithm in absorbing the unexpected fluctuations in the net-load caused mainly by the stochastic behavior of the produced wind power.