An observer for a nonlinear descriptor system

The present study is motivated by previous work which sought input-output linearizing control laws for AC/DC power systems, which are modeled in the nonlinear DAE framework. Simulation studies verified the effectiveness of these control strategies when all the descriptor variables were assumed available for feedback. In the present work, the authors consider measurement limitations and attempt to reconstruct the descriptor variables with a nonlinear observer. Sufficient conditions are derived for the construction of an asymptotic observer and, although these conditions are somewhat restrictive for large-scale systems, they provide some insight toward a design for the particular application considered here (a) single-machine AC/DC power system). Some simulation results are provided along with a discussion of some interesting features of this problem which may warrant further investigation