Power electronic transformer is a new type of intelligent transformer of a multi function,its biggest feature is the small size and light weight , improve power quality and flexible way transmission, power electronic transformer is one of the most important equipment in the construction of green power and digital power grid, there are a growing number of scholars concerned about it. This paper first introduces the development of power electronic transformer and the necessity of research; Secondly, this paper introduces the working principle and topological structure of AC/DC/AC type power electronic transformer; Then, the power electronic transformer controller was designed and simulated analysis, the simulation results show that, the power electronic transformer design has many unique properties of traditional transformer do not possess, and to achieve an ideal effect; Finally, summarize the full text and analysis of the difficulties in the future development of power electronic transformer will be faced.