DC-DC Buck-Boost Converters With Unknown CPL: An Adaptive PBC

We develop in this paper an adaptive passivity based controller for output voltage regulation of DC-DC buck boost converter with unknown constant power load. This control problem is theoretically challenging since the average model of the converter is a bilinear second order system that, due to the presence of the constant power load, is non-minimum phase with respect to both states. A solution to the problem was recently reported in [9], however, the resulting control law is extremely complicated to be of practical interest. The aim of the paper is to design a novel, significantly simpler, controller that can be easily implemented in applications. The key modifications introduced in the new design are the use of a change of coordinates and a partial linearization that transform this system into a cascade form, to which an adaptive energy-shaping controller is applied. Another merit of the designed control law, besides its simplicity, lies in that it is amenable for the addition of an outer-loop PI that improves its transient and disturbance rejection performances. Simulations and experimental results are provided to assess the improved performance of the proposed controller.