Research On A New Three-port Active Bridge Muti-resonant DC-DC Converter

With the implementation of new energy strategy,electric vehicle has been developing faster and faster in recent years.In electric vehicle internal power system,DC-DC converter is an indispensable part.Three-port DC-DC converter has compact topology,high power density and lower cost.In this thesis,a three-port active bridge multi-element resonant DC-DC converter is proposed,which consists of two active half-bridge ports and one active full-bridge port.Both half-bridge ports contain a switched multiple resonant tank.The switchable multi-element resonant tanks increase the operation mode of the converter,so that the multi-port converter can meet more needs of electric vehicles.The converter has both hardware decoupling and full load range soft switching characteristics.The steady state mathematical model of the converter is established by Fourier analysis method,and the range of Zero Voltage Switching(ZVS)is obtained by time-domain analysis.The gain characteristics between the three ports are analyzed according to the range of ZVS.By analyzing the influence of multi-element resonant tanks on the coupling characteristics between ports,a design method of hardware decoupling under different modes is summarized,so as to realize the independent control of two output ports.The closed-loop simulation model was established according to the decoupled main circuit topology for verification.The dynamic mathematical model after decoupling is established by using reduced order method.Based on the simplified state equation,the small-signal model is derived,and the open-loop transfer function from the control variable to the output variable is derived.According to the mathematical model,the regulators of constant current port and constant voltage port are designed,and the correctness of theoretical analysis and design is verified by simulation.Finally,an experimental prototype with rated power of 848 W was built based on TMS320F28335 DSP,and the working principle,soft switching characteristics and decoupling control strategy of the proposed converter were verified.The experimental results verify the correctness of the theoretical analysis..