| Bidirectional DC-DC converter is viewed as the key interface equipment for energy transfer and kinetic energy recovery conversion device of the new energy vehicles,which plays a pivotal role in realizing the transformation of the energy structure among the transportation industry.DAB DC-DC converter is equipped with the advantages of bidirectional energy transfer as well as high power density,which is also widely utilized.Nevertheless,the power back-flow phenomenon still exists under the conventional phase shift control and can not be eliminated at all.The back-flow power and soft-switching operating characteristics are bonded together to the voltage matching degree under the extended phase shift control,and both of which contribute to the failure of DAB to perform well.This paper will select DAB converter as the research topology to discuss the optimization strategy of backflow power as well as soft-switching.Initially,the paper conducts an analysis of the working principal of phase shift control of the DAB converter.The working mode of the converter on account of the single phase shift is presented in detail,and the mathematical model of power transfer of DAB is set up.The mathematical model of operation characteristics is established via the analysis of the waveforms control.In allusion to the issue that the single phase shift control with only one phase shift angle can not completely optimize the operating characteristics of DAB converter,the extended phase shift control is drawn forth by means of amplifying the phase shift angle.Afterwards,the operating mode under the extended phase shift control will be analyzed,and the corresponding mathematical model is established,and the relationship diagram among each operating characteristic and the added phase shift angle as well as the voltage matching degree under the extended phase shift is plotted in the meantime.In addition,for the purpose of reducing the back-flow power under extended phase shift control and achieve soft switching of the switching tubes meanwhile,a dual optimization strategy based on extended phase shift control is proposed to reduce the back-flow power of the converter and achieve the maximum range of soft switching under the two-stage optimization of transmission power.The relationship among the soft switching range of the primary and secondary switch tubes as well as the voltage conversion ratio of the converter under extended phase shift control is analyzed,and the soft switching of the primary switch tube is selected as the constraint to optimize the back-flow power in the first section of the transmission power and make the soft switching of the primary full-bridge switch tube come true,and simultaneously,the back-flow power can be theoretically reduced to zero as well.In the second section,the Lagrange multiplier method is adopted to optimize the back-flow power with the transmission power as the constraint,so that the back-flow power value can reach the minimum.Besides,the proposed optimization strategy is coming through the validation of the simulation on the PSIM platform,and the results manifests that the segmental optimization strategy realizes the back-flow power reduction in the full power range and the soft switching of the primary full-bridge tube in the first power section.Eventually,the experimental prototype platform is designed and built for experimental verification.The design of the prototype chiefly consists of the hardware part as well as the software program process design of the control system.Accordingly,experimental results show that the proposed optimization strategy is feasible and effective.Figure [46] Table [5] Reference [61]... |
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