Flexibility Region Quantification and Optimal Scheduling of Fast Charging Stations Considering EV User Discharge Willingness

The high penetration of intermittent renewable energy requires a more flexible power grid. Electric vehicles (EVs), capable of rapid grid response, serve as efficient and economical flexible resources. However, EV users often prefer fast charging and are reluctant to participate in vehicle-to-grid, while overstay occupancy (OC) at fast charging stations (FCSs) results in penalties for them. Thus, leveraging the bidirectional flexibility of EVs is essential for efficient grid operation at FCS. This paper proposes a method to quantify the flexibility region of FCS operation considering OC and EV user discharge willingness (EUDW). First, a flexibility region model and evaluation indices are developed for FCS integrated with photovoltaic and energy storage systems, enabling precise quantification of EV flexibility in different states and determining the adjustable boundaries of the flexibility region. To address the randomness of EUDW, an incentive model is proposed, considering OC duration, net discharge compensation, and discharge margin to incentivize users’ participation. Additionally, a dual-layer decision framework, incorporating behavioral economics and affine fuzzy logic control, is developed to enhance decision-making under EUDW uncertainty. Finally, a collaborative optimization scheduling model for the flexibility resources of FCS is proposed to maximize benefits for both operators and users. Case studies verify that the proposed model and methods effectively improve the operational flexibility of FCS by coordinating flexible resources, enhancing station revenue, balancing flexibility supply and demand, and reducing users’ expenses.