3. Hierarchical Coordinated Control Strategies for Plug-in Electric Vehicle Charging

Currently in most of the works in the literature, a group of plug-in electric vehicles (PEVs) is controlled by an “aggregator”. The aggregator is responsible for making the charging schedule for each PEV and also participates in power system regulation or electricity market bidding. However, practically, to coordinate the charging of large scale PEVs in power system, the diversities in charging infrastructure, PEV types and local operational constraints in the power system should also be well considered. Therefore, hierarchical control of PEVs is regarded as an effective way to achieve charging cost minimization and system operational security. This book chapter introduces hierarchical control frameworks for PEV charging, which includes coordinated charging strategy for charging station (or virtual charging station), coordinated charging strategy for battery swapping station, hierarchical coordinated charging strategy for multiple charging stations and a three level coordinated charging framework for large scale of PEVs. The detailed mathematical formulations for each level operator in the proposed hierarchical control framework, which jointly optimize system load profile and charging costs, are clearly presented. The inter-relationships between various levels of operators in terms of energy transaction and information exchanged are also specified. Finally, case studies are carried out on three cases. The simulations results demonstrate the effectiveness of the hierarchical charging control framework and optimization methods in reducing peak demand and charging costs.