Robust sigma-delta generalised proportional integral observer based control of a 'buck' converter with uncertain loads

摘要

This article describes the design of an observer based robust linear output feedback controller for the regulation and output reference trajectory tracking tasks in switched 'buck' converter circuits feeding a completely unknown time-varying load. The state-dependent perturbation effects of the unknown load resistance are on-line estimated by means of a generalised proportional integral (GPI) observer, which represents the dual counterpart of GPI controllers introduced in Fliess, Má rquez, Delaleau and Sira-Ramí rez (Fliess, M., Má rquez, R., Delaleau, E., and Sira-Ramí rez, H. (2002), 'Correcteurs Proportionnels-inté graux Gé neralisé s', ESAIM: Control, Optimisation and Calculus of Variations, 7, 23-41). The reconstructed perturbation complements the controller in a cancellation effort which allows the core of the feedback controller to become a traditional proportional derivative (PD) controller. The designed average feedback controller is then implemented via a sigma-deltamodulator, which effectively translates the designed continuous average feedback control input signal into a discrete valued switched input signal driving the converter's input switch and preserving all relevant features of the average design. The Appendix collects some generalities about GPI observers.