Abstract
This paper proposes a novel load frequency control (LFC) scheme for multi-area thermal-hydro power systems (MATHPS) subject to multiple communication delays. The scheme integrates an integral sliding mode controller (ISMC) with a Kalman filter (KF) to enhance system robustness and dynamic performance. By formulating a novel state-space model for MATHPS that explicitly accounts for multiple time delays in thermal and hydro units, the approach ensures greater system fidelity and control accuracy. A KF is developed to handle delayed measurements and disturbances while effectively reducing network resource utilization from sensors to the controller, thereby enhancing system efficiency. By providing delay-resilient state estimation, the filter enables timely and reliable control actions, improving overall system stability under uncertain operating conditions. Leveraging these estimated states, a ISMC law is developed to drive the system trajectory toward a predefined sliding surface, thereby effectively reducing steady-state error and mitigating control chattering. Furthermore, a Lyapunov-based stability criterion with linear matrix inequality formulation is employed to ensure asymptotic stability of the closed-loop system, even in the presence of time delays. Simulation studies on the LFC models show that the proposed method achieves faster frequency recovery, reduced overshoot, and improved stability compared to existing techniques, particularly under severe disturbances and time-delay conditions.