Solid-state transformers (SSTs) are promising in the flexible dc transmission and dc microgrid. However, the core equipment of SST, dual active bridge (DAB) converter, is only modeled by dc and 1st harmonic components, which is not precise enough for control design and stability estimation. Generalized averaging model considering the second harmonic component (SHC-GAM) for the DAB converter is proposed in the paper. The 2nd harmonic component is considered to improve the switching dynamics of the DAB converter, and the small-signal model and control-to-output gain are studied. The magnitudes for the control-to-output transfer function of SHC-GAM and the detailed switching model are compared. The results are in good agreement. The SHC-GAM of the DAB converter for SST is accurate enough and promising for practical needs.

Dual active bridge;generalized averaging model;harmonic component