Approaches for continuous-time dynamic modeling of the asymmetric dual-active half-bridge converter

This paper describes two continuous-time approaches for modeling the dual-active half-bridge converter, operated with 3D control i.e control involving variation of the duty-ratios of the two half-bridge legs along with the phase-shift. The first full-order model, based on generalized averaging, results in a model capable of approximately predicting both the fast inductor current dynamics and the slow capacitor voltage dynamics of the converter and is applicable to any generic case of 3D control. The second approach, based on simple averaging, results in a reduced-order model capable of predicting the slow voltage dynamics with greater accuracy. The demerit of this approach is the difficulty in extending it to other modes of operation, which limits its usability for 3D control. This problem is circumvented by focussing the analysis on the optimum high-frequency operating modes, which yield the best converter efficiency. Relevant transfer functions using both approaches are plotted and verified by comparing them with results obtained from PLECS simulation studies.