Research On The Three-Level Boost Converter With Isolated Transformer

This thesis first introduces the research and application background of the three-level (TL) Boost converter with isolated transformer. Then different type TL Boost converters are further discussed. It can be seen that TL Boost converters with isolated transformer have less been researched.Focusing on the single-end isolated Boost converter and the buck type TL converter with isolated transformer, if using the TL technology structing method, series and parallel principle and the duality principle, a new family of TL Boost DC-DC converters and TL Boost AC-AC direct converters with isolated transformer can be obtained,which enriches the theory of TL technology.This paper discusses the single-ended and the improved push-pull double-voltage TL Boost DC-DC converters with isolated transformer in detail, including the operation principle and relevant formulas of the new topologies. The improved push-pull double-voltage TL Boost DC-DC converter is proposed to ensure the similar voltage gain when switch duty cycle is smaller than 0.5 and larger than 0.5. Then a comparison among different Boost DC-DC converters with isolated transformer is made. The simulation results prove the TL Boost DC-DC converter with isolated transformer can work correctly.The thesis makes an analysis of the push-pull double-voltage TL Boost AC-AC direct converter in detail, including the formula deduction, the operation analysis and the design of the interleaved phase shifted dual closed loop strategy. The closed loop simulation results prove the correctness of the new topology and the control method.Different modular designs of control circuit, the selection of drive circuit and elements of power circuit are given respectively. The experimental results indicate that the new push-pull double-voltage TL Boost AC-AC direct converter can work correctly.