Flexibility of Electric Vehicle Charging With Demand Response and Vehicle-to-Grid for Power System Benefit

As charging load from electric vehicles (EVs) increases, its temporal demand may challenge existing power systems. However, as EVs could also supply power to the grid, they could provide benefits for the power systems. Moreover, by controlling the charging, they could reduce their charging costs. Thus, in this study the flexibility of EV charging load within charging events was modeled, considering available charging power, ambient temperature, and unidirectional and bidirectional controlled charging. Then, the charging flexibility was first analyzed by minimizing the charging costs for individual EVs. The results showed that with high electricity market prices, with high fluctuation, the EVs could reduce their charging costs up to 27% and 35%, with unidirectional and bidirectional controlled charging respectively, compared to uncontrolled charging. Secondly, the EV charging flexibility was analyzed for the benefit of the power system by an aggregator, assuming a fully electrified car sector. The benefit was measured by the required additional power source capacity and generation. During the analyzed period, 2018-2023 which peak load was 14.7 GW, the required power source capacity increased significantly with uncontrolled charging, by 2-2.8 GW (40-54%), whereas with controlled unidirectional charging the increase was 0.3-0.8 GW (7-15%), and with bidirectional charging the capacity was the same as without EVs, or slightly less (−11-1%). However, the yearly differences were notable, and during 2020, with bidirectional charging, this capacity increased. Moreover, the required power source generation was greatly affected by the assumed power generation capacities, and was lower with controlled charging, compared to uncontrolled charging.