A stochastic resource-sharing network for electric vehicle charging

We consider a distribution grid used to charge electric vehicles subject to voltage stability and various other constraints. We model this as a class of resource-sharing networks known as bandwidth-sharing networks in the communication network literature. Such networks have proved themselves to be an effective flow-level model of data traffic in wired and wireless networks. We focus on resource sharing networks that are driven by a class of greedy control rules that can be implemented in a decentralized fashion. For a large number of such control rules, we can characterize the performance of the system, subject to voltage stability constraints, by a fluid approximation. This leads to a set of dynamic equations that take into account the stochastic behavior of cars. We show that the invariant point of these equations is unique and can be computed by solving a specific ACOPF problem, which admits an exact convex relaxation. For the class of weighted proportional fairness control, we show additional appealing properties under the linearized Distflow model, such as fairness, and a product form property of the stochastic model.