Research On Design Of Dual Active Full-Bridge Converter Based On GaN HEMT Device

Bidirectional DC-DC converter is an important part of electric vehicle power conversion.In recent years,the application of dual active full-bridge converter(DAB)and the emergence of new generation semiconductor materials such as GaN have provided a new direction for the performance optimization of bidirectional DC-DC.In this thesis,an experimental platform of dual active full bridge converter based on GaN HEMT device is built,and the overall performance of the platform is analyzed.The main work of this thesis is divided into the following parts.Firstly,after analyzing several common bidirectional DC-DC topologies,the topology and working principle of dual-active full-bridge converter are introduced in detail,and then several common phase-shifting control methods are analyzed,of which advantages and disadvantages are compared in detail.Secondly,the structure of GaN HEMT devices is analyzed,and the characteristics of E-mode and Cascode GaN HEMT switches are analyzed in detail by building a dual-pulse test(DPT)platform,and the driving loss and conduction loss of GaN HEMT are calculated based on the experimental data,which provide theoretical support and data reference for the design of the GaN HEMT-based DAB platform.Then a dual-active full-bridge converter experimental platform based on E-mode GaN HEMT is designed.The hardware design method is introduced in detail,including main circuit parameter selection,driving design requirements and control design.Due to the switching speed of GaN HEMT device is very fast and it is very sensitive to parasitic parameters,this thesis also gives a detailed analysis of the PCB layout considerations of dual active full bridge converter.In the experimental results section,the voltage and current waveforms and overall efficiency of the platform at 200 kHz are given.The switching frequency are further increased,and the waveforms and efficiency at different switching frequencies are compared and analyzed.Then the overall loss distribution is further discussed and analyzed,which provides a basis for the design of high power density DAB converter.