Un-terminated frequency response measurements and model order reduction for black-box terminal characterization models

Black-box terminal characterization models are constructed from "un-terminated" frequency response functions (FRF) measured at the converter terminals without requiring explicit knowledge of any of the converter parameters; however to some extent, these measurements are always coupled with the source and load dynamics which reduces the fidelity of the final models obtained. This paper analyzes this problem and proposes a methodology to obtain un-terminated FRFs for dc-dc converters in the presence of source and load coupled FRF measurements. Furthermore, it presents a model order reduction technique to enable the simulation of dc distributed power systems with a large number of converters, applied to the calculated un-terminated FRFs that constitute the black-box models in question. Experimental results are presented to verify the theoretical analysis and the high accuracy obtained with the black-box models built.