The large-scale integration of electric vehicles (EVs) into power grids presents both opportunities and challenges for the construction of new power systems. Effectively guiding orderly EV charging and discharging to enhance user-side regulation capabilities in new power systems and support the low-carbon transformation of energy consumption has become a pressing issue. However, due to the complexity of demand-side user decision-making psychology and supply-side transportation systems, the mechanism by which charging/discharging prices influence user behavior remains unclear. To address this, this paper first analyzes the decision-making psychology of demand-side EV users, analyzing how charging and discharging decisions are influenced by different psychological accounts. Based on reference dependence theory, value measurement functions for charging and discharging are established. Then, on the supply-side, this paper considers a transportation system composed of both hybrid vehicles and EVs, and the spatiotemporal distribution mechanisms of EVs are revealed through a dynamic activity-travel assignment model that traces the root causes of travel behavior. Finally, case studies explore the spatiotemporal patterns of EV charging/discharging demands and analyze the impact mechanisms of pricing strategies and user decision-making psychology on charging/discharging behaviors. The research findings provide valuable references for the planning and deployment of vehicle-to-grid (V2G) charging infrastructure, the optimization of pricing mechanisms, and the construction and deployment of microgrids.