A Two-Stage Optimization Framework for Validating Electric Vehicle Charging Infrastructure under Grid Constraints

This paper develops a sequential planning and operational-validation framework to assess post-deployment performance of electric vehicle (EV) charging infrastructure with mixed charger technologies for large fleets under distribution-grid constraints. The first stage constructs three infrastructure configurations: a cost-oriented design, an investment-constrained integrated design reference, and a same-hardware spatial redistribution. In the second stage, each fixed configuration is re-optimized under a common charging-service objective, with selected cases further evaluated through local downward-flexibility redispatch. Results on the CIGRE medium-voltage (MV) network show that infrastructure requirements increase with EV fleet size and battery capacity, while spatial redistribution can degrade charging service and shift nodal voltage and loading patterns despite unchanged hardware and investment. Re-optimizing infrastructure within the first stage investment limit produces only marginal, case-dependent changes in post-planning service. Flexibility validation indicates that realizable flexibility through redispatch depends on deployment design and service-degradation allowance, with larger allowances enabling greater delivery in constrained cases. The framework reveals how infrastructure investment and siting affect post-deployment grid performance, and operational flexibility.