Robust fractional hybrid controller for frequency regulation in nonlinear multi-area power systems amid communication delay and cyber-attack

The digitalization of modern power systems (PSs) has transformed conventional grids into cyber-physical systems, increasing their vulnerability to communication delays and signal disturbances. This paper proposes a Flow Direction Algorithm (FDA)-optimized one-plus-tilt derivative cascaded with a fractional-order integral-derivative ((1+TD)-I^λD^μ) controller for robust load frequency control of nonlinear renewable-integrated PSs. The cascaded fractional-order structure enhances tuning flexibility and robustness against communication delays and signal perturbations. Rather than detecting cyber-attacks (CAs), the proposed controller is evaluated under false data injection (FDI), denial-of-service (DoS) attacks, random communication delays, and hybrid CAs using multiple benchmark PS models. A unified controller tuning strategy is employed across all operating scenarios, including the IEEE 39-bus and Kundur 11-bus test systems. Stability is verified through the Lyapunov-Krasovskii functional (LKF)-linear matrix inequality (LMI) framework, while controller-in-the-loop (CIL) experiments confirm the controller's practical feasibility and real-time applicability.