Hierarchical Charging Coordination Of Large-scale Plug-in Electric Vehicles

A hierarchical charging coordination of large-scale plug-in electric vehicles is studied in this paper. The charging behaviors of large-scale plug-in electric vehicles without any control will cause many negative effects on the grid. Centralized or decentralized charging schedules of large-scale plug-in electric vehicles(PEVs) coordinated by a system operator usually require significant management, computation and communication capabilities on the system. Alternatively, this paper firstly constructs a hierarchical model for the PEV charging coordination problems based on one-node model, where a collection of agents are introduced between the system operator and individual vehicles, and propose an off-line decentralized method for the constructed hierarchical optimization problems. To reimburse the transaction operation costs on agents, the charging price on the PEVs under an agent comprises both the generation price broadcasted from the system operator and the operation price set by this agent under this method. Each PEV implements its best behavior with respect to a given local charging price curve set by its agent. The operator then updates the electricity generation price based on the aggregate load demand collected from all the agents and broadcasts it to PEVs via agents. This paper shows that, under certain conditions, the proposed dynamical procedure converges to the efficient solution. In order to further study the PEVs’ charging behaviors under the condition of the actual network structure and power transmission constraints, this paper constracts a charging model of large-scale PEVs based on multi-nodes, and proposes two kinds of off-line decentralized algorithms by introducing Optimal Power Flow(OPF). The operating characteristics of the system are analyzed by using the 2-nodes model, and the convergence of the algorithm is verified by using the model based on 14-nodes. In the model constracted in this paper, the practical constraints of the power grid are considered, the convergence of the hierarchical charging model is verified, the load imbalance in power system is reduced obviously, and there are only low computation and communication capability requirements on the system.