Research On Control Strategy Of Interleaving Parallel Magnetically Integrated Bidirectional LLC Resonant Converter

The interleaving parallel technology can effectively expand the power capacity of LLC resonant converter and improve the full load operation efficiency of the converter,but it also brings the problems of low light load efficiency and current sharing;When the load varies widely,the frequency range of LLC resonant converter is very large,which is not conducive to the design of magnetic components.Therefore,this dissertation takes interleaving parallel magnetically integrated bidirectional LLC resonant converter as the research object,aiming to improve the operation efficiency of the converter,shorten the working frequency range of the converter,and makes research from two aspects of control strategy and the application of new power device Ga N.Firstly,the main circuit structure of interleaved parallel magnetically integrated bidirectional LLC resonant converter is proposed,the principle of automatic current sharing of magnetically integrated coupled inductors and the working characteristics of the converter are analyzed,the main circuit parameters of the converter are designed.The small signal model of LLC resonant converter is established by using the extended function method,the dynamic characteristics of the converter are analyzed,and the PI closed-loop control strategy of the converter is designed,next,the hybrid control method of phase shift + frequency conversion+phase shielding is proposed,the rationality of the hybrid control method is analyzed,and the implementation scheme and software control flow chart based on DSP digital controller are given.In order to further improve the operation efficiency of the converter,the application of Ga N device in LLC resonant converter is studied.The working characteristics of Ga N device are introduced,the influence of stray inductance and Miller capacitance on high frequency drive circuit are analyzed in detail,based on this,the design criterion of Ga N drive circuit is given,and the design of Ga N drive circuit module is completed.Finally,the system controller of the converter is designed,and the experimental prototype is built,the rationality and effectiveness of the proposed hybrid control method are verified by experiments,the advantages of Ga N devices in operation efficiency are verified by comparative experiments.The paper has 65 figures,2 tables and 49 references.