Consensus-based coordination of electric vehicle charging considering transformer hierarchy

The paper considers the coordination of electric vehicle (EV) charging where the loading on the transformers that serve the distribution feeders is taken into account. A decentralized control method is designed such that self-interested EVs are motivated to achieve global benefits. The formulation has a hierarchical structure. At the lower level, each transformer broadcasts a price signal to the EVs that it supplies, and the EVs individually determine their optimal charging strategies. At the upper level, the communication network between transformers is described as a graph and a consensus algorithm among the transformers is used to obtain a group consensus price that reflects the system generation cost. Each transformer then establishes a price which is composed of the consensus price together with a contribution that accounts for its loading characteristic. An update algorithm is developed which converges in a few (typically around ten) iterations to the unique and efficient (socially optimal) solution.