A reduced-order adaptive state observer for DC–DC converters with unknown constant power load

In this paper, main objective is to develop a reduced-order adaptive state observer (RASO) for a large class of DC–DC converters with constant power load (CPL) to estimate their unavailable states and unknown parameter, which facilitates achieving an output feedback control (OFC) scheme of the systems. Its construction contains two main procedures. First, by using a generalized parameter estimation based observer (GPEBO) technique, state reconstruction problem is reformulated as the estimate of parameter after the system reparameterization. A linear regressor equation is then obtained. Second, we apply GPEBO technique for it again and then dynamic regressor extension and mixing (DREM) method are adopted such that a RASO for the converters described by a class of bilinear system is designed, which is called as 2G+D observer. The comparison study among the proposed observer and other existing observers is conducted. An obvious merit of the former is that the observability of the systems is only verified for ensuring exponential convergence without needing any extra excitation condition. Subsequently, the presented observer is applied to boost converter feeding unknown CPL for achieving an OFC. Finally, the simulation and experimental results are provided.