Flexible energisation of EV fleet charging load using dynamic operating envelopes

The electrification of medium and heavy-duty (MDHD) electric vehicles (EVs) holds significant potential for transportation electrification, with over one-third of annual energy in the US potentially used for EV charging. However, the concentrated charging loads of MDHD EV fleets can strain utility assets. This study explores managing MDHD EV fleet charging using Dynamic Operating Envelopes (DOEs), which set operational limits to enable more EVs to charge within existing system capacities. DOEs define upper and lower operating limits for distributed energy resources (DERs) over time. An advanced charging method using a charging priority factor (CPF) is proposed to manage EV fleet demand within these limits. The CPF assigns charging rates based on factors like connection duration and battery state of charge. A case study with three EV fleets on a generic distribution feeder shows that traditional fixed capacity limits would allow only 11 EVs to charge at a maximum rate of 19.2kW. In contrast, DOEs and flexible charging enable 50 or more EVs to charge under the same conditions. Factors affecting energy delivery include DOE time-step resolution, charging allocation methods, and capacity distribution across fleets.