In recent years, electric vehicle (EV) charging stations have experienced an increasing supply-demand mismatch due to their fluctuating renewable generation and unpredictable charging demands. To reduce their operating costs, this paper proposes a distributed online algorithm to promote energy sharing between charging stations. We begin with the offline and centralized version of the EV charging stations operation problem, whose objective is to minimize the long-term time-average total cost. Then, we develop an online implementation approach based on the Lyapunov optimization framework. Although the proposed online algorithm runs in a prediction-free manner, we prove that by properly choosing the parameters, the time-coupling constraints remain satisfied. We also provide a theoretical bound for the optimality gap between the offline and online optimums. Furthermore, an improved alternating direction method of multipliers (ADMM) algorithm with an iteration truncation is proposed to enable distributed computation. The proposed algorithm can protect privacy while being suitable for online implementation. Case studies validate the effectiveness of the theoretical results. Performance comparisons are carried out to demonstrate the advantages of the proposed method.

中文翻译：

---

一种促进电动汽车充电站间能量共享的分布式在线算法

近年来，由于波动的可再生能源发电和不可预测的充电需求，电动汽车 (EV) 充电站的供需失配日益严重。为了降低他们的运营成本，本文提出了一种分布式在线算法来促进充电站之间的能量共享。我们从 EV 充电站运营问题的离线和集中版本开始，其目标是最小化长期时间平均总成本。然后，我们开发了一种基于 Lyapunov 优化框架的在线实现方法。尽管所提出的在线算法以无预测的方式运行，但我们证明通过正确选择参数，时间耦合约束仍然得到满足。我们还为离线和在线优化之间的最优性差距提供了理论界限。此外，提出了一种改进的交替方向乘子法（ADMM）算法，该算法具有迭代截断功能，以实现分布式计算。所提出的算法可以保护隐私，同时适合在线实现。案例研究验证了理论结果的有效性。进行性能比较以证明所提出方法的优点。