Charging Station Planning to Maximize Extra Load Hosting Capacity in Unbalanced Distribution System

The distribution system operation and planning are facing a great challenge from the increasing penetration of electric vehicles, especially in case of large amount of aggregated simultaneously charging load at public charging stations. This paper proposes a comprehensive planning method for allocating charging stations with a minimum impact on distribution system hosting capacity while satisfying public charging demand with reasonable travel distance and investment cost. A new concept of extra load hosting capacity (ELHC) is proposed to evaluate the maximum extra load that the system can absorb without operational violations. The EV charging demand is estimated using a transportation simulation tool with real-world data. The distribution system is modeled with a linear three-phase branch flow model that captures the multi-phase and unbalance of a distribution system. The planning problem is formulated as a mixed-integer linear programming (MILP) problem and is validated on the IEEE 123 node test feeder together with real-world Illinois transportation network data.