Comprehensive modeling and control strategies for a three-phase dual-active bridge

The dual-active bridge (DAB) is a dc-dc converter, which offers several advantages especially in high-power applications. Besides bidirectional power flow and small filter size, the converter provides galvanic isolation via a medium-frequency transformer. The converter´s inherent soft-switching capability promises very high efficiency due to the reduction of switching losses. In this paper, different modeling approaches are derived that cover the dynamic behavior of the three-phase dual-active bridge. The first approach utilizes a state-space averaging method in conjunction with state-variable averaging. The second modeling approach applies a first-harmonic approximation. After the comparison of these two different models with a circuit simulation, a control design method is developed based on those models. The control is evaluated for different converter parameters. Finally, the developed control is implemented using a DSP-controlled laboratory prototype of the converter and the results are presented.