Quantification of downward flexibility of an EV fleet participating to local flexibility tenders organized by distribution system operators

Electrical mobility is considered an important flexibility source that could be used to provide local flexibility for the distribution network in the coming years, allowing to avoid local congestions while satisfying charging needs of individual drivers. The goal of this study is to quantify the downward flexibility potential (i.e., reduction of consumption/increase of injection) that an Electrical Vehicle (EV) fleet can provide to participate in local flexibility tenders organized by a Distribution System Operator (DSO). This quantification is performed by solving two deterministic optimization problems successively. The first optimization problem aims at establishing the nominal aggregate consumption profile of a given EV fleet, while the second one aims at maximizing the power reduction as compared to the nominal profile during a given time interval, referred to as the activation period in the paper. Both problems encode the fact that individual charging needs of vehicle should be met. This methodology is applied to an open dataset of residential EV charging sessions in the United Kingdom and allows to quantify the maximal downward power flexibility which may be sustained during a given time interval. A sensitivity analysis is performed to assess the impact of different parameters of the optimization problems such as parameters of the activation period (date, time, duration), as well as the notification delay by the DSO and the possibility to discharge EVs.