Extended Nonlinear Disturbance Observer-aided Robust Controller for Frequency Regulation of a Hybrid Power System

This work presents a resilient frequency controller based on an extended nonlinear disturbance observer (ENDO) for an autonomous hybrid power system (hyPS) with mismatched uncertainties. The proposed ENDO estimates the unknown lumped plant uncertainties, including exogenous plant disturbance and parametric uncertainty. Subsequently, a refined sliding mode control action is formulated by augmenting this estimation for effective damping of frequency oscillations of hyPS. An updated sliding manifold is introduced to accelerate state convergence rate and ensure finite time convergence. The boundedness of disturbance estimation error and closed-loop stability with an ENDO-aided frequency controller has been guaranteed considering the Lyapunov theorem. The efficacy of the developed control system has been shown over other well-known controllers reported in the literature under diverse operating conditions. Analysis of the system performances demonstrates the supremacy of the developed resilient control methodology in terms of fast damping of system oscillations, least chattering in control input, and robustness.