| As a critical component in power electronic transformers,high-power high-frequency transformers have a broad application prospect in locomotive traction,grid-connected renewable energy and smart grids.High-frequency transformers play a role in achieving energy transmission,voltage conversion,and electrical isolation,and the loss and parasitic parameters of the high-frequency transformer will affect the transmission characteristics of the entire system.Also,with the increasing demand for a higher power density of the entire system,a comprehensive and reliable integrated structure considering all magnetic components is urgently proposed.This paper conducts the related research from three aspects,as shown below.Firstly,the magnetic integration technology combines the high-frequency transformer and inductor in one structure,which decreases the passive volume and increases the overall power density.By Taking the integration of high-frequency transformer and inductor as an example,this paper gives a systematical introduction and comparison of the existing magnetic integrated structure.The magnetic integrated structure introduced in this paper can be mainly divided into two categories: using the leakage inductance characteristics of HFT and restructuring the core or winding.The former one can be divided into three categories: large leakage inductance integrated structure,leakage inductance integrated structure by providing a low reluctance path and leakage inductance integrated structure by increasing the permeability of the main insulation.The latter one can be divided into two categories: magnetic integrated structure with coupling between magnetic parts and decoupling integrated structure.By means of finite element simulation,this paper gives a comparison and analysis of the realization principle of each integrated structure.Secondly,the decoupling principle and the loss characteristics of a low loss orthogonal decoupling magnetic integrated structure(ODMIS)are analyzed in this paper,and the optimal decoupling condition to minimize the core loss is also derived.A 400V/6k W/20 k Hz DAB converter prototype is built to validate the effectiveness of the ODMIS.The measured full-load overall efficiency of the DAB test platform is 97.55%,and the power density of the magnetic integrated components is 10.08 k W/L.Finally,the prototype comparisons between the proposed ODMIS and two existing magnetic integrated structures and discrete magnetic component method are conducted,and the advanced feature of the ODMIS is illustrated.Finally,for a new winding structure—flexible printed circuit boards(FPC),analytical models for its winding loss,leakage inductance and stray capacitance are established in this paper.The winding loss’ s analytical model is calculated using the equivalent of a single-layer foil.And the analytical model of the leakage inductance is calculated by the magnetic field energy method based on the one-dimensional electromagnetic field distribution.The singlecapacitor lumped parameter model of the stray capacitance is deduced based on the parallel plate capacitor model.Finally,the three analytical algorithms are verified by experiments.This paper provides a general analytical modeling method for the winding loss and parasitic parameters of FPC winding. |
