Intelligent frequency regulation in islanded microgrids using a crayfish-tuned FO–(PD–PI) controller with energy storage coordination

Frequency stability has become a serious challenge in the case of standalone microgrids where renewable energy sources (RESs) are predominant, due to their variability and the system’s low inertia. The innovation presented in this paper is to control load frequency in an islanded hybrid microgrid including a diesel generator, PV unit, and dynamically controlled redox flow battery (RFB) using a new cascaded fractional-order (FO) (PD-PI) controller that has been optimized using the Crayfish Optimization Algorithm (CrOA). What sets this proposed controller apart from traditional controllers is its dual-loop structure, allowing for a combination of fast dynamic response and precise steady-state regulation while ensuring optimal parameter tuning through the CrOA. The system was evaluated through an extensive series of disturbance scenarios, including step changes, random and cyclic load disturbances, fluctuations in the PV output, and RFB faults. Simulation results showed that the FO-(PD-PI) + CrOA controller outperformed classical PID and other fractional controllers in terms of reducing overshoot, response time, and Integral Time Absolute Error (ITAE), while maximizing energy storage utilization. These results demonstrate the potential of intelligent bioinspired control strategies for microgrid operation with resilience and efficiency.