  This paper addresses the problem of regulating the output voltage of a DC-DC
buck-boost converter feeding a constant power load,which is a problem of
current practical interest. Designing a stabilising controller is theoretically
challenging because its average model 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.Moreover,to design a high performance controller, the
knowledge of the extracted load power, which is difficult to measure in
industrial applications, is required. In this paper, an adaptive
interconnection and damping assignment passivity based control that
incorporates the immersion and invariance parameter estimator for the load
power is proposed to solve the problem. Some detailed simulations are provided
to validate the transient behaviour of the proposed controller and compare it
with the performance of a classical PD scheme.
