As the penetration level of plug-in hybrid electric vehicles (PHEVs) increases, the charging demand of PHEVs is expected to have a major impact on the loading of distribution systems. Charging access control, which determines the starting time of PHEV charging, is critical to mitigate such impact. In this paper, we investigate how to achieve PHEV charging access control by leveraging the electricity price set by electricity retailer and the speculative prices of PHEV owners. A firm-union bargaining game approach is proposed to study the interactions between the electricity retailer and PHEV owners. In order to eliminate the requirement of a centralized energy management system, we extend the original centralized firm-union bargaining game approach to a semi-distributed approach. In particular, the retailer plays the role of the union for wage control by setting the electricity price for PHEV charging, while balancing the revenue and cost. On the other hand, each PHEV owner uses a responsive strategy to optimize his/her own benefit by choosing an appropriate charging starting time. Through nonlinear programming, a sub-game perfect Nash equilibrium solution can be attained. The PHEV owners in the game can determine their strategies independently to maximize their own benefits. The model is further extended to consider the cost of charging demand fluctuation reflected by the cost of purchasing frequency regulation or spinning reserve services by distribution utilities. Extensive numerical results are presented to evaluate the performance of the proposed approach.
