Scheduling the Charge of Electric Vehicles Including Reactive Power Support: Application to a Medium-Voltage Grid

The simultaneous charging process of multiple electric vehicles (EVs) may cause violations of power distribution grids' operational constraints, such as voltage levels outside statutory limits, line currents above lines' ampacities, and congestion at the substation transformer. This paper investigates the impact on a medium voltage distribution grid of i) uncoordinated charging, ii) coordinated grid-aware charging, and iii) coordinated grid-aware charging of EVs with reactive power support for voltage regulation. In all these cases, the EVs' charging policy is determined with an optimal power flow (OPF) problem, where suitable sets of constraints are modeled to reproduce each specific case. Results are investigated for the 14-bus CIGRE MV benchmark network. The proposed methods are useful for grid operators to identify suitable control strategies for EV charging.