Integrating Ultra-Fast Charging Stations within the Power Grids of Smart Cities: A Review

Plug-In Electric Vehicles (PEV) have become a key factor driving towards smart cities, which allow for higher energy efficiency and lower environmental impact across urban sectors. Industry vision for future PEV includes the ability to recharge a vehicle at a speed comparable to traditional gas refueling, i.e., less than $3$ minutes per vehicle. Such a technology, referred to as Ultra-Fast Charging (UFC), has drawn much interest from research and industry. The large power density, impulsive, and stochastic loading characteristics of UFC, however, pose unprecedented challenges to existing electricity supply infrastructure. Planning the locations and electric capacities of these UFC stations is critical to preventing detrimental impacts, including grid asset depreciation, grid instabilities, and deteriorated power quality. In this paper, we first review planning methods for conventional charging stations and then discuss outlooks for UFC planning solutions by drawing an analogy with renewable energy source planning, which presents similar power density and stochastic characteristics as UFC. While this paper mainly focuses on UFC planning from the power grid perspective, other urban aspects, including traffic flow and end-user behavior, are examined for feasible UFC integration within smart cities.