As electric vehicles (EVs) are increasingly integrated into the power grid, their uncoordinated charging behavior poses challenges to grid stability. Simultaneously, their mobile energy storage characteristics offer new avenues for coordinating vehicle-grid interaction. This paper proposes a method for predicting the virtual energy storage state of urban electric vehicles, establishing a comprehensive framework from travel chain modeling to energy storage state assessment. Steady-state and non-steady-state storage energy, as well as external charging/discharging power, are defined to quantitatively analyze the dynamic storage characteristics of electric vehicle clusters. Simulation results show that the proposed model can not only describe EV travel behavior but also reliably predict the spatiotemporal distribution of charging load at various nodes in the network and assess their potential for energy storage dispatch.