With the increasing penetration of electric vehicles(EVs)

the disordered charge and discharge behaviors bring negative impact on normal operation of power grid. Vehicle-to-grid(V2G)is an excellent solution for this problem. V2G mode based on microgrid is used for energy exchange between EVs and power grid

and multi-objective optimization model

in which minimum grid load fluctuation

maximum renewable energy utilization and maximum owners gain are taken as the optimization objectives

is established. In order to solve the optimization model

variable threshold optimization algorithm is proposed firstly

and an improved algorithm named variable charge and discharge rate optimization algorithm is proposed. The optimization results show that the two proposed algorithms could increase utilization of renewable energy

improve the imbalance between power supply and demand in the microgrid and increase benefits of EV owners through reasonable scheduling.