Research Of High-Frequency Isolated Hybrid DC Converterand Hysteresis Control Scheme

Power electronic transformer(PET)as a succedaneum of traditional transformer which owns superior characteristics in voltage and power transfer has been paid more and more attention in recent years.As the pivotal part of PET isolated DC-DC converter has been lucubrated by domestic and foreign scholars.Among all of the research results,LLC resonant converter and DAB converter are gaining more and more attention from academics.Both of the above converters owns soft-switching ability.LLC resonant converter could achieve soft-switching operation under all load condition and owns constant potential regulation ability.But,its power transfer ability is limited by the resonant capacitor’s current capacity.However although DAB converter could achieve high power transfer operation,there is no direct relation between the phase shift and its output voltage.So,in order to keep the stable power transfer and output voltage,a complex control scheme is always been required in practice.No doubt this will increase the complexity of the converter and decrease the reliability of the whole system.This paper proposed a new breed of high-power DC-DC converter based on hybrid LLC resonant and DAB converters.The voltage across the module could be clamped by LLC resonant converter based on its steady voltage characteristic,and let DAB take on the task of high power conversion.Such converter module can solve the problem that the power capability of LLC is limited by its resonant capacitor’s current capability and simplify the control scheme of the whole module.Moreover,this paper designed a simple but effective hysteresis control scheme which could make the converter rapid stable response when the load is suddenly changed.Finally,an experimental prototype of hybrid high-frequency isolated DC-DC converter is designed and tested,the experimental result verified the effectiveness and correctness of the proposed topology and control scheme.