Research On Modulation Strategy Of Dual Active Bridge DC-DC Converter

Renewable energy has the advantages of being clean and reusable,but the power generation of renewable energy has the characteristics of instability and intermittence.Therefore,the renewable energy generation system can be coordinated with the energy storage equipment and the power grid composed of AC and DC microgrid system.Dual active bridge DC-DC converter is widely used between energy storage equipment and power grid.In this paper,the basic working principle and modeling of various phase shift control are introduced,and the back-flow power and transient bias of DAB converter are optimized based on TPS.This paper first analyzes the basic working principle of single phase shift,extended phase shift and double phase shift,compares the transmission power characteristics and current stress characteristics of three kinds of phase shift,and concludes that compared with single phase shift,extended phase shift and double phase shift can expand the transmission power range and reduce the current stress.Based on triple phase shift control,this paper takes backflow power and soft switch as dual optimization objectives.Firstly,the triple phase shift modes are classified,and the transmitted power and back-flow power expressions are discussed.Taking the backflow power as the objective function,the transmitted power as the equality constraint,the soft switching condition and the mode constraint as the inequality constraint,the shift comparison combination with the minimum backflow power was solved,and the middle power section was constructed to minimize the backflow power.The existence of transient DC bias will increase the current stress of the switch tube and endanger the normal operation of the converter.In this paper,the working mode is reclassified according to the initial current value based on triple phase shift,and an essential method to suppress transient bias is proposed,that is,the inductor current value is adjusted by adjusting the driving signal during the transition process.The transient transition quantity is discussed for each mode mutation,and the purpose of reducing the current impact and transition process time is finally achieved.Finally,the platform construction process of DAB converter is introduced,including the selection of switch tube,the design of high frequency isolation transformer,and the design of auxiliary circuit and software design.The proposed back-flow power optimization strategy and transient bias optimization strategy are carried out on the experimental platform,and the experimental results verify the effectiveness of the optimization strategy.