Robust sliding mode observer design for interconnected systems

In this paper, a class of nonlinear interconnected systems is considered in the presence of structured and unstructured uncertainties. The bounds on the uncertainties are nonlinear and are employed in the observer design to reject the effect of the uncertainties. Under the condition that the structure matrices of the uncertainties are known, a robust sliding mode observer is designed and a set of sufficient conditions is developed such that the error dynamics are asymptotically stable. If the structure of the uncertainties is unknown, an ultimately bounded observer is developed using sliding mode techniques. The obtained results are applied to a multimachine power system to demonstrate the effectiveness of the developed methods.