Robust Adaptive Sliding Mode-Based Frequency Control for Nonlinear Thermal Power Systems With Boiler Dynamics

This paper proposes a robust load frequency control (LFC) strategy for nonlinear thermal power systems (TPS). Unlike conventional LFC models, the developed system explicitly incorporates governor dead band, generation rate constraint, and boiler dynamics, providing a more realistic representation of practical TPS. To address the limitations of existing approaches that are typically developed for simplified models, an enhanced sliding mode control (SMC) framework is developed in a unified state-space form. First, an integral sliding surface with embedded state-feedback is introduced to enable explicit shaping of the sliding dynamics via eigenvalue assignment. Second, to guarantee the reachability of the sliding manifold while reducing chattering, a modified super-twisting algorithm is employed. Furthermore, an adaptive control law is designed to compensate for nonlinearities and unknown uncertainties without requiring prior knowledge of their bounds. The stability of the proposed method is rigorously established using a Lyapunov-based approach formulated in terms of linear matrix inequalities. Extensive simulation studies are conducted on single-area and dual-area TPS under various load disturbances and nonlinear constraints. The results demonstrate that the proposed method achieves faster frequency recovery, reduced overshoot, improved steady-state accuracy, and lower chattering compared with recent SMC-based control schemes.