Realise flexibility potential of EV fleets through grid-serving charging strategies

Making flexibility of electric vehicles usable for distribution system operators is crucial to further integrate large portions of renewable energy sources into the energy system as well as high power loads. This paper provides a better understanding of a fleet's flexibility potential with a nightly dwell time and its deployment using indirect control schemes related to grid charges. Three grid-serving charging strategies were modelled (time-variable grid charges (TV), flexible time window (FL), and schedule (SC)) and compared for local setup configurations using a photovoltaic (PV) system, stationary battery, and vehicle-to-grid (V2G) in varying grid situations. In comparison to simple balanced charging, all grid-serving strategies can achieve a higher utilisation of energy from periods with generation surplus and reduce residual load peaks. TV has substantially higher precision in increasing energy withdrawal during curtailment, while FL performs comparable in utilising generation surplus. Both can be extended by additional flexibility through battery and V2G; an additional PV system, however, decreases the volume of shiftable load. In most variations, gridserving charging results in savings for the DSO which are not fully reflected by the consumer grid charges. The results indicate how feed-in from flexible components has to be remunerated to render it more attractive for both DSO and customer.