Renewable‐Based Electric Vehicle Charging and Grid Support Through Bi‐Level Optimization

Abstract

This study proposes a bi‐level optimization framework for coordinated electric vehicle charging and discharging in renewable‐based distribution networks. The upper‐level problem minimizes feeder losses from the Distribution Grid Operator perspective, while the lower‐level problem minimizes charging costs for electric vehicle owners under time‐of‐use electricity tariffs. The model incorporates wind and solar generation, seasonal operating conditions, and bidirectional vehicle‐grid power exchange. The proposed framework is implemented in the General Algebraic Modeling System using the Extended Mathematical Programming approach, in which the lower‐level problem is reformulated through Karush–Kuhn–Tucker conditions. A 28‐bus radial distribution system is used to evaluate three operating modes: the base case, coordinated charging with renewable energy, and coordinated charging with renewable energy and bidirectional grid interaction. The results show that system losses decrease from 6.519 MW in the base case to 5.703 MW in winter and 6.115 MW in summer without bidirectional operation. With bidirectional operation, losses are further reduced to 4.945 MW in winter and 5.413 MW in summer. Charging costs also decrease from 196.35 to 166.59 dollars in winter and from 205.17 to 191.33 dollars in summer. These results confirm the effectiveness of the proposed framework in reducing losses and charging costs.