EV charging strategies for office parking lots to relieve local grids

High penetration of electric cars in urban areas may lead to concentrated and uncoordinated heavy EV charging demand in residential areas of the distribution systems. This demand may coincide with the peak demand of the system and consequently poses issues pertaining to reliability, power quality, security, and the difficult operation of stressed distribution systems. Office Parking Lots (OPLs) equipped with adequate EV charging facilities have been seen as one of the tangible solutions to cope with such irresistible situations if found financially viable.

This work proposes two charging strategies, uncoordinated EV charging (UEVC) and coordinated EV charging (CEVC), for OPLs to minimize the impact of EV charging demand on local grids by placing suitable capacity of distributed energy resources (DERs) such as solar photovoltaic (SPVs) and battery energy storage systems (BESS). The proposed CEVC strategy schedules EVs considering mean generation from the grid-connected rooftop SPV system and the state-of-charge of BESS and aligns EV charging demand with SPV generation. Further, the proposed model is tested on an 83-bus real distribution system to investigate the impact of OPL integration on the system’s technical parameters, such as peak demand, total energy losses, peak power loss, and node voltage deviation. Moreover, the techno-economic benefits of both strategies are compared, and EV parking charges are calculated while considering the profit for OPL owners. Simulation results show that the proposed CEVC strategy reduces the OPL’s annual grid energy import, OPL’s annual peak demand, total system energy losses, and parking charge by 85 %, 65 %, 20 %, and 11 %, respectively, when compared with UEVC without DERs. Moreover, despite heavy investment in DERs’ placement at OPL, the proposed charging strategies preserve the benefit of the utility and OPL owners, yet offer more competitive EV parking charges.