Research On Interleaving And Magnatically Integrated Bi-directional CLLC Resonant Converter

The high efficiency natural soft-switching characteristics of bidirectional CLLC resonant converter make it have obvious advantages in the field of new energy power generation and DC transmission and distribution.The principle and characteristics of bidirectional CLLC resonant converter are analyzed,the AC equivalent model and DC characteristics are derived,and the influence of parameters on the performance of the converter is analyzed,and the influence of parameters on resonant current is analyzed in underresonant mode.It provides conditions for the optimal design of parameters.Then,aiming at the problem of magnetic integration in staggered parallel bidirectional CLLC resonant converter,a new type of transformer magnetic integration structure,"[+]" transformer integration structure,is proposed,which is compared with the traditional "EE" transformer integration structure.The magnetic potential difference model is established,and the difference between the magnetic flux density distribution and the magnetic potential difference is analyzed.It is concluded that the magnetic flux density distribution of the "[+]" transformer integrated structure is more uniform and the magnetic potential difference is smaller than that of the "EE" transformer integrated structure.The advantage of low Eddy current loss caused by dispersion Flux.The magnetic circuit model is established,the design method of integrated transformer is given,and the magnetic flux density and flux distribution are simulated and analyzed by using the electromagnetic components in Ansys software.The simulation results show that the flux density distribution of the integrated structure of "EE" transformer is uneven,and the bypass flux and diffusion flux are serious,which verifies the correctness of the theoretical analysis.The prototype of the integrated transformer is made,and it is concluded that the volume of the transformer is reduced by 40%,and the power density of the converter is improved,which shows that the advantages of transformer integration are obvious.Then two ZVS implementation conditions and gain monotonicity requirements of bidirectional CLLC resonant converter are given.for DC / DC converter system,it is pointed out that only increasing excitation inductance has a limited effect on converter efficiency and neglects the influence of frequency range on converter efficiency.The optimized parameter design method is given,that is,under the condition of satisfying the maximum gain of full load,the maximum excitation inductance and the minimum k value are selected to limit the operating frequency range,so that the converter is closer to the full resonance state.At the same time,the ZVS and ZCS characteristics of the resonant converter are guaranteed,and the efficiency of the converter is improved obviously in the whole load range,especially in the case of full load.Finally,the effectiveness of parameter design is proved by Saber simulation,and the experimental system is built and the hardware circuit of the system is designed.The experimental results show that the efficiency of parameter optimization is improved obviously.The "[+]" transformer integrated structure has higher efficiency and power density.The thesis has 58 charts,6 tables and 55 references.