Output-Feedback Saturated Control of DC-DC Converters With Unknown Independent Loads

This article presents a solution to the output-feedback control problem of dc-dc converters with unknown independent output loads. The available measurements are limited to the voltages across the capacitors and the input sources. A general lossless model of the converter is considered, which eliminates the need for knowledge of parasitic elements such as the input side parasitic resistance. However, this poses a challenge for observer-based design due to the lack of detectability. To address this challenge, a dynamic full-information controller is designed, taking into account the control signal saturation of the system. To handle the presence of parametric uncertainty in the output dynamics, a constructive filtered transformation is proposed to convert the dynamics into a proper adaptive observer form. By utilizing the immersion and invariance technique, a reduced-order filter is derived, leading to a reduced-order observer. The parametric convergence is achieved with a weaker condition compared to the usual persistency of excitation requirement for converters with a single unknown load. The dynamic controller is reinforced in conjunction with the observer to overcome the detectability obstacle and uniform global asymptotic stability of the closed-loop system is guaranteed. The computation of filter dynamics is canceled in the control algorithm by redesigning the observer and updating the adaptation law with feedback from the regulation error. The performance of the proposed control algorithms is experimentally evaluated on a dc-dc Buck converter with unknown parasitic and output resistances.