Loss Modeling And Optimization Of Dual Active Bridge DC-DC Converter Based On DPS Modulation

With the continuous development of new energy power generation technology and DC distribution network technology,how to stably store and transmit electrical energy has become a hot spot in the field of power system.Dual-Active-Bridge（DAB）DC-DC converters have gradually become important electrical energy conversion devices between different levels of DC buses and between a DC bus and an energy storage device with its high stability,high power density and flexible control,etc.In order to reduce the loss and improve the working efficiency of the DAB converter,loss model research and efficiency analysis are needed.In this paper,a dual phase shift modulation is taken as an example to specifically analyze the loss model,output power and efficiency of the DAB converter.Firstly,the topology and working principle of DAB converter are introduced.The working characteristics of the three phase-shift modulation methods are analyzed.For dual phase shift modulation method,the working conditions of switching devices in different modes and the change trend of voltage and current are analyzed in detail.Based on the derived voltage and current formula,the output characteristics current stress characteristics and reflow power characteristics of the converter with dual phase-shift modulation are analyzed.Secondly,the losses generated during the operation of the DAB converter are classified,and the losses are modeled by combining the advantages of existing loss models.For the mutual constraint relationship between the conducting voltage drop and the inductor current variable in the switching device,the loss model of the switching device based on the ideal inductor current and the switching device loss optimization model considering the influence of the conducting voltage drop on the inductor current were further established.The comparison between theoretical derivation and simulation results confirms that the optimization model has higher accuracy.Then the effect of loss on output power and efficiency is studied.Further analysis of the output power characteristics of the DAB converter under dual-phase-shift modulation with loss consideration.It was found that the coordinates of the modulation parameter corresponding to the maximum output power point shifted,and the degree of shift was related to the device parameters.The effect of the loss on the actual efficiency value is analyzed,and the peak of the efficiency change is located near D₂=0.2～0.3.Therefore,for each modulation point on the ideal output power curve,the modulation points of D₂<0.5 has more advantages in efficiency and real output power.Finally,the design and construction process of the experimental platform is introduced.The accuracy of the loss model and the maximum output power point offset trend and efficiency distribution trend are verified using the experimental platform.