Dual Active Bridge Converter With Asymmetric Duty Cycle Phase-Shifting Control

Dual-active-bridge converter is widely used in power electronic interface devices of microgrid systems and intermediate stages of power electronic transformers,its traditional control method is single-phase-shifting control,which is simple in control and easy to implement soft-switching.However,due to the load requirements of microgrid systems and power electronic transformers and the fluctuation of power system voltage,when the voltage matching degree deviates from 1,reflow power and current stress of the converter will increase greatly,so new control methods need to be studied.In order to reduce the reflow power and current stress of DAB during power transfer in the phase-shifting control mode,this paper first analyzes operating modes and characteristics of the dual-active-bridge converter under single-phase-shifting control and the one-way full-bridge DC-DC converter under asymmetric duty cycle control,and verified by simulation.Based on this,a bilateral asymmetric duty cycle phase-shifting control method based on dual-active-bridge converter is proposed.In order to further reduce the current stress and the reflow power,after simplification and improvement,a simpler and more flexible unilateral asymmetrical duty cycle phase-shifting control method is proposed.The mode of operation of the converter under two kinds of asymmetric duty cycle phase-shifting control modes were analyzed successively,and a steady state model of reflow power and current stress were established.Then comparative analysis of the reflow power characteristics and current stress characteristics under single-phase-shifting control and two kinds of asymmetric duty cycle phase-shifting control methods were carried out and verified by simulation.In order to further reduce the reflow power and current stress under the unilateral asymmetrical duty cycle phase-shifting control,this paper aims at the condition of the minimum back-flow power,the single-closed-loop minimum reflow power control strategy and the minimum reflow power control strategy based on the soft-switching technology for unilateral asymmetric duty cycle phase-shifting control were studied.Aiming at the minimum current stress realization condition,the minimum current stress control strategy was studied.Finally,the effectiveness of the three control strategies was verified by simulation.