Research On SEPIC Three-Level Intelligent Transformer

Intelligent Transformer was first put forward by Koosuke Harada et al. in 1996, later developed into Power Electronic Transformer which maks use of high-frequency power electronic converter technology. It is successful to be used in power system. It not only realizes voltage converting and energy transfering, but also the flexible control for the voltage amplitude and phase of the first and seconde side of the high-frequency transformer, and has the function of power factor correction. To be used in power system, it can help to make power quality and system stability better. Today, as the rapid development of power industry, it is more necessary for us to study its new topology structure and control strategy. If it realizes higher-frequency converting, its volume and weight should be more small. Therefore, its study is more useful and valuable to build green and intelligent gird.First, paper introduces the current research of PET and analyzes the advantage and shortcoming of some PET which are existed. Then, paper researches the topology structure of SEPIC Three-Level Intelligent Transformer in detail. The multi-level technology is applied to the topology, which can obviously reduce the voltage stress of switchs and the volume of filter. Secondly, paper analyzes its working principle and switching mode, and designs transient voltage feedback control strategy with same capacitor voltage. Its simulation model is set up in Saber 2007. The feasibility of new topology and correctness of control strategy are verificated by simulation, and simulation results under different load and disturbance input are proposed. At last, paper introduces the design process of main parameters of SEPIC Three-Level Intelligent Transformer and controller component in detail. In the end, a single phase principle prototype is made to verificate the feasibility of new topology and correctness of control strategy. By experiment, results show excellent performance of prototype, and fully reflect the superiority of SEPIC Three-Level Intelligent Transformer.