Enhanced load frequency control using a novel fractional-order integral-integral-derivative controller optimized by cuckoo catfish optimizer.

Maintaining frequency stability in interconnected power systems (IPSs) is a critical challenge, particularly under sudden load changes and nonlinear constraints. Conventional PID and fractional-order controllers (FOPID, TID, FOID, and cascaded FO-PID structures) either lack adaptability or introduce excessive complexity. To overcome these limitations, this study introduces a novel fractional-order integral-integral-derivative (FOIID) controller that replaces the proportional term with a second-order fractional integrator. This dual-integral design yields 27 possible configurations, enhances the low-frequency gain, and eliminates the steady-state ramp error, thereby improving the transient and steady-state performance. The recently developed cuckoo catfish optimizer (CCO) is employed for parameter tuning. Unlike conventional metaheuristics (PSO, GA, and GWO), CCO integrates cooperative space compression, chaotic predation, and adaptive regeneration strategies, which avoid premature convergence and achieve a robust global search. The proposed CCO-FOIID framework was validated on a two-area non-reheat benchmark system and further tested on a three-area thermal-thermal-hydro system with generation rate constraints under 1% and 2% step load disturbances. A comparative analysis against five state-of-the-art controllers (ISFS-PID, DSA-FOPID, WHO-PI(1 + FOPID), and CGO-FOPID-FOPI) demonstrates that CCO-FOIID consistently achieves faster settling times, reduced overshoot, and the lowest ITAE value (74.26), outperforming the best competitor (CGO-FOPID-FOPI, 82.67). These results confirm that the combination of FOIID's universal structure and CCO's robust optimization provides a simple yet powerful solution for modern LFC applications in both simple and complex IPS networks.