Smart Grid is the newest direction of electric power development, and is regarded as the significant technology innovation and development trend of the electric power system in 21st century. It is also regarded as the inevitable result of the development of economic and technology. It has flexible, clean, safe, economical, and friendly functions. Smart grid is a new "second generation" network, which is built on an integrated basis of two-way high-speed communication networks, through the application of advanced sensing and measurement techniques, equipment technology, control technology and decision support system technology in order to achieve reliable, safe, high-quality, economical, efficient, environmentally friendly and safe using target. Smart Grid’s background, significance key technologies, technical difficulties and prospects are introduced in this paper.

V2G technology is an important part of the smart grid,which realizes the power inter-transformation between Power Grid and electric vehicles [1]. V2G technology is introduced and the structure of charging and discharging system in V2G technology is analyzed [2]. Under synchronous rotating frame, the combination current-controlled and Voltage space vector control method is adopted, which carries out the power inter-transformation between Power Grid and electric vehicles [3].