A CrOA-tuned cascaded (2DOF-PDf)-(LTI) controller for coordinated LFC-AVR regulation in interconnected power systems

Interconnected power systems are frequently exposed to load disturbances, parameter uncertainties, nonlinear effects, and dynamic coupling between frequency and voltage regulation loops, which make it difficult to maintain stable and well-coordinated operation. Conventional control strategies may suffer from slow damping, large oscillations, and reduced robustness when applied to such highly coupled environments. To address this problem, this paper proposes a novel cascaded controller for the coordinated regulation of Load Frequency Control (LFC) and Automatic Voltage Regulation (AVR) in a two-area interconnected power system. The proposed controller combines a two-degree-of-freedom proportional-derivative controller with filtered derivative action (2DOF-PDf) and an inner leaky tilt-integral (LTI) stage to improve transient shaping, damping, and robustness while reducing sensitivity to disturbances and parameter variations. The controller parameters are optimally tuned using the Crayfish Optimization Algorithm (CrOA) based on the Integral of Time-weighted Squared Error (ITSE) criterion. The effectiveness of CrOA is first verified through comparison with several well-known optimization methods, including the Chimp Optimization Algorithm (ChOA), Dingo Optimization Algorithm (DOA), Sine Cosine Algorithm (SCA), Gorilla Troops Optimizer (GTO), and Gradient-Based Optimizer (GBO). The proposed control scheme is then assessed under various operating scenarios, including step load disturbances, stochastic load variations, practical nonlinearities such as Generation Rate Constraint (GRC) and Governor Dead Band (GDB), time-varying voltage reference tracking, and parametric uncertainty of up to ± 40%. MATLAB/Simulink results demonstrate that the proposed CrOA-tuned cascaded (2DOF-PDf)-(LTI) controller provides faster damping, smaller frequency and tie-line power deviations, and more accurate terminal-voltage regulation than several benchmark controllers, including Proportional-Integral-Derivative (PID), Tilted Integral Derivative (TID), Fractional-Order Proportional-Integral-Derivative (FOPID), and Fractional-Order Proportional-Integral with Proportional-Integral-Double Derivative Squared (FOPI-PIDD²) controllers. Overall, the proposed controller offers a robust and effective solution for coordinated frequency and voltage regulation in interconnected power systems.