Reserch On Phase Shift Control Of A Double-active Full-bridge DC-DC Converter

With the increasing impact of energy crisis and environmental pollution,new energy and distributed power supply are becoming increasingly important for its advantage of high reliability of power supply,small transmission loss,local absorption,high flexibility and so on.Power electronics converters are used to connect all kinds of distributed power supply and energy storage to distributed energy sources,thus enabling effective energy scheduling.The converter with isolation transformer can transfer energy between high and low voltage distribution buses well.Meanwhile,due to the advantages of symmetrical structure,low voltage stress,easy to control the size of power,transmission direction,electrical isolation and soft switching characteristics,dual-active full-bridge DC-DC(DAB)converters is widely utilized in power electronic converters.Based on the research of phase-shift control of a DAB converter,this paper mainly focuses on the aspect of theory and characteristic optimization of DAB converter.The main contribution of this paper are as follow:1)This paper analyzed the general phase-shift control mode for DAB converters.Besides,the distribution of power and current is deduced and the range of range of power transmission under different phase shift control mode is obtained under the same power condition.2)Based on mathematical model of phase shift control,the symmetry conclusion of transmission power and current is proposed according to the range of power transmission,which is been proved that it’s also applicable to the symmetry analysis in condition of power forward transmission and power reverse transmissionhave the same optimization objective.Furthermore,the calculation of bi-directional power transmission characteristics of DAB converters is simplified and the feasibility of symmetry through simulation is also been verified.3)For the power circulating flow problem in DAB converters,this paper studies the use of triple phase shift control with the highest degree of freedom in the condition of soft switching and power forward transmission.The power circulating flow of both DC sources in the full power range are optimized to reduce the influence of the power circulating flow on the converter and to improve the power transmission performance of the converter.The simulations in this paper have proved the practicability.4)On the DAB convertor experimental prototype,experimental results on the DAB convertor have validated the symmetry theory,the effective of the optimal control strategy for two-side power circulating flow in reducing the two-side power flow,and the advantages of improving the power transmission performance of the converter.