A tri-level optimization model for the integrated energy system with orderly charging/discharging of electric vehicles

Given the rapid growth of electric vehicles (EVs) ownership and the accelerated construction of novel energy systems, it is urgent to promote the integration of EVs and integrated energy systems (IESs). This study proposes a tri-level optimization model to optimize the operation and capacity of the IES with the orderly charging/discharging (OCD) of EVs considering individual EV behavior. In which, the trip schedule and state of charge (SOC) demand of EVs is predicted by a spatiotemporal-SOC characterization model. Moreover, through the charging and discharging quote based on the trend of time-of-use tariffs to guide the OCD of each EV, the decoupling of the OCD decision-making and IES scheduling is achieved based on an interaction level and a pre-calculation method. Finally, this study optimizes the operation and capacity of the IES with the minimum operating cost and total cost, respectively. Following a simulation case study, the results show that the IES with OCD of EVs can reduce the operating cost by 12.1 % at the expense of 0.9 % increase in equipment cost, which is significantly better than that with the electrical energy storage devices (EESs) which reduces the operating cost by 6.9 % at the expense of 7.9 % increase in equipment cost. Moreover, integrating the OCD of EVs with the EESs can reduce the operating cost by 17.9 % and the final total cost by 7.4 %. At the same time, EV owners in general not only achieve free charging but also receive an overall daily revenue of 613.3 CNY to supplement the additional battery degradation loss of EVs. This study also conducted uncertainty analyses on the number of EVs, battery capacity and charging/discharging power, and energy prices. Generally, this study investigates the economic and technical feasibility of integrating EVs with IES.