Analytical and Optimisation-Based Strategies for Load Frequency Control in Renewable-Rich Power Systems

The growing integration of renewable energy sources (RES) has fundamentally altered power system dynamics, reduced system inertia and challenged conventional Load Frequency Control (LFC) mechanisms. This study presents a comprehensive review of analytical and optimisation-based approaches for frequency regulation in low-inertia, renewable-rich power systems. It highlights the evolution from classical proportional–integral (PI/PID) controllers to advanced model-based, robust, adaptive, and intelligent control schemes, emphasising their relative strengths in handling uncertainty, variability, and multi-area coordination. Additionally, the paper examines Frequency-Constrained Unit Commitment (FCUC) frameworks that explicitly incorporate frequency stability metrics, such as Rate of Change of Frequency (RoCoF), frequency nadir, and inertia adequacy, into scheduling and dispatch. Through comparative analysis, the study identifies key performance trends, computational challenges, and practical trade-offs between analytical and optimisation paradigms. The paper concludes by outlining open research directions, including decentralised FCUC, multi-agent coordination, and AI-assisted control, aimed at achieving scalable and resilient frequency regulation. Overall, this review bridges the gap between control theory and operational optimisation, offering a unified perspective to guide the development of next-generation frequency control frameworks in modern power grids.