Research On High-efficiency Dual-active Bridge Converter With Optimal Modulation Paramaters

Renewable energy technologies attracte more and more attention because of thelack of fossil fuels. All of these technologys can not keep apart with power electrictechnology, especially the bidirectional DC-DC converter which acts an importane rolein electrical devices as a power source.Dual-active bridge converter which can reduce the number of active devices andincrease the power density of converter is researched in this paper, especially for theefficiency. Firstly, the operation characteristic in different modules is analyzed.Secondly, the key factor (RMS value of current in high frequency transformer) whichinfluences the efficiency is found through the analysis and calculation. Thirdly, themodules which can reduce RMS value of current are found by comparing all modulesand then the optimum module parameters (D1, D2and) which can get the least RMSvalue are calculated. Besides, simulations for phase shift modulation, triangular currentmode modulation and optimum parameters modulation in whole power levels arederived to prove the calculation of optimum parameters. At last, simulations andexperiments of phase shift modulation, triangular current mode modulation andoptimum parameters modulation are accomplished in appropriate operation condition,the efficiency in different modulations is measured to certify the correctness andfeasibility of the calculation method.Compared to previous studies in terms of efficiency of dual-active bridge converter,this article does not increase efficiency by using soft-switching transformer but bychanging the current waveform to reduce its RMS value to increase efficiency.Optimum parameters calculation methods in whole power levels are derived in thispaper for the reason that the optimum methods are different in different power levels.Another difference in this paper is the use of space-state method based on discrete timeto derive control to output transfer function in dual active bridge converter. There arethree UCC3895(two pieces are controlled by the last one) in the control circuit whichperforms well in practice experiments to control the three parameters. The results of thisarticle certifies that the efficiency of dual-active bridge converter can be improved byreducing the RMS value of high frequency transformer current without soft switchingtechnology.