Delay-tolerant HHO-tuned fuzzy fractional controller for frequency regulation in renewable-powered microgrids with HFC integration

Integrating renewable energy sources (RESs) into isolated microgrids introduces major load frequency control (LFC) challenges due to reduced system inertia, nonlinear dynamics, stochastic power fluctuations, and communication delays. Conventional PID-based controllers often exhibit limited robustness and poor adaptability under rapidly varying operating conditions. Although fuzzy logic controllers (FLCs) improve disturbance handling and adaptive response, they may suffer from limited tuning precision, while standalone fractional-order controllers (FOCs) usually involve complex parameter adjustment and reduced flexibility under highly dynamic disturbances. To overcome these limitations, this study proposes a novel hybrid LFC framework that combines an FLC with a fractional-order TIλDμ controller, whose parameters are optimally tuned using the Harris hawk’s optimization (HHO). The proposed hybrid structure exploits the adaptive decision-making capability of FLC together with the superior damping characteristics and dynamic flexibility of FOC. In addition, a hydrogen fuel cell (HFC) is integrated as a dynamically controlled energy storage unit to provide fast corrective power support during transient disturbances. The proposed controller adapts in real time to system nonlinearities, fluctuating renewable generation, communication delays, and varying load conditions without relying on highly detailed mathematical models. Its performance was evaluated under seven operating scenarios, including single-step load changes, sequential disturbances, random load variations, cyclic oscillations, solar intermittency, and delayed response conditions. Comparative results demonstrate that the proposed HHO-optimized fuzzy fractional controller consistently outperforms PID, fuzzy-based, and FO-(PD–PI) controllers in terms of overshoot reduction, settling time, steady-state accuracy, and damping performance. Under single-step disturbance conditions, the proposed controller achieved the lowest overshoot of 0.0012 pu and the minimum ITAE value of 0.0043 pu·s, while maintaining stable and well-damped responses under solar intermittency and communication delay scenarios. These results confirm the robustness, adaptability, and effectiveness of the proposed control strategy.