System Level Black-Box Models for DC-DC Converters
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ABSTRACT The aim of this work is to develop a two-port black-box dc-dc converter modeling methodology for system level simulation and analysis. The models do not require any information about the components, structure, or control parameters of the converter. Instead, all the information needed to build the models is collected from unterminated experimental frequency response function (FRF) measurements performed at the converter power terminals. These transfer funtions are known as audiosuceptibility, back current gain, output impedance, and input admittance. The measurements are called unterminated because they do not contain any information about the source and/or the load dynamics. This work provides insights into how the source and the load affect FRF measurements and how to decouple those effects from the measurements. The actual linear time invariant model is obtained from the experimental FRFs via system identification. Because the the two-port model obtained from a set of FRFs is linear, it will be valid in a specific operating region defined by the converter operating conditions. Therefore, to satisfy the need for models valid in a wide operating region, a model structure that combines a family of linear two-port models is proposed. One structure, known as the Wiener structure, is especially useful when the converter nonlinearities are reflected mainly in the steady state currents and voltage values. The other structure is known as a polytopic structure, and it is able to capture nonlinearities that affect the transient and steady state converter behavior. The models are used for prediction of steady state and transient behavior of voltages and currents at the converter terminals. In addition, the models are useful for subsystem interaction and small signal stability assesment of interconnected dc distribution systems comprising commericially available converters. This work presents for first time simulation and stability analysis results of a system that combines dc-dc converters from two different manufucturers. All simulation results are compared against experimental results to verify the usefulness of the approach.
- Doctoral Dissertations