Abstract: ： The disordered charging of a large number of electric vehicles will aggravate the peak-to-valley difference of the power grid and affect the quality of power supply and transformer life. This paper considers the optimization strategy of real-time charging and discharging of electric vehicles under the distributed control framework from the perspective of group. According to different charging requirements of accessing electric vehicles， this paper proposes a real-time scheduling method that uses the end-of-charge timing as a grouping feature. A bi-level optimization model is used to solve the optimal charging and discharging power of the whole cluster and individual electric vehicle. The upper level aims at minimizing daily load fluctuations and scheduling penalty， and establishes a real-time optimization scheduling model of large-scale cluster. The lower layer considers the charging and discharging costs of electric vehicle owners and solves the optimal tracking problem of an individual electric vehicle. Taking the load data of a typical regional distribution network as an example， the simulation results show that the real-time charging optimization strategy under distributed control can ensure the reliable operation of the power grid， taking into account the interests of all parties.

Key words: electric vehicle cluster, vehicle-to-grid（V2G）, grouping, bi-level optimization