Operation Efficiency Analysis And Optimization Design Of Dual Active Full-bridge DC-DC Converter

The dual active full-bridge DC-DC converter as the core of modern power electronic transformers has the characteristics of high power density,small size,high efficiency and easy in-line connection and replacement.It is used in energy storage power generation,electric vehicles and DC-DC grid.There is a wide range of applications in power transmission and it has a bright future in future industrial applications.This paper mainly studies the influence of the parasitic parameters of the switching on the system output efficiency in the dual active full-bridge DC-DC converter,and on this basis,the optimization experiment of the operating efficiency is carried out.The main research contents of this article are as follows:(1)This article first introduces the working principle and operating characteristics of the dual active full-bridge DC-DC converter,analyzes the power transmission characteristics,reflux power characteristics and soft switching characteristics of the dual active full-bridge DC-DC converter.The problem of efficiency optimization between reflux power characteristics and soft switching behavior is described.(2)Based on the existing soft switching research,the parasitic capacitance parameters of the switch are introduced,and the sufficient conditions for the dual active full bridge DC-DC converter to achieve soft switching are re-established.Adjusting the inter-bridge phase shift and the intra-bridge phase shift of the dual active full-bridge DC-DC converter to ensure that the current stress can be reduced under soft switching conditions,and the conduction loss and switching loss are reduced to improve the output efficiency of the system.(3)Two different control methods,single phase shift control and extended phase shift control,are used to introduce sufficient conditions of soft switching considering parasitic capacitance parameters into the efficiency optimization scheme.For single phase shift control,voltage adjustment and frequency modulation are adopted to achieve efficiency improvement.This is especially effective when the system is lightly loaded;for extended phase shift control,the method of adjusting the internal operating state of the dual active full-bridge DC-DC converter by adjusting the bridge-to-bridge shift compared to the bridge-to-bridge shift is adopted to ensure soft switching.Reduce current stress and achieve improved efficiency.(4)On the basis of the improved efficiency optimization scheme mentioned above,the experiment of the system under light load conditions was first carried out to verify the effectiveness of the scheme,which is helpful to the realistic situations such as light load output and solar output under severe weather conditions.On this basis,the efficiency optimization scheme under extended phase-shift control was tested,and the effectiveness of the method for improving output efficiency was verified.In addition,the closed-loop control experiment under the small signal model is also carried out in this paper,and it is verified that the designed closed-loop control can meet the stable voltage control under different load conditions.