Hybrid FPA-SSO-optimized fuzzy-FOPID controller with virtual inertia control for robust frequency regulation in low-inertia microgrids
Abstract
The rapid integration of renewable energy sources (RES), such as wind and solar power, into microgrids reduces system inertia and may intensify frequency instability. This issue threatens reliable operation, particularly in microgrids with high RES penetration. To address the instability caused by reduced inertia, this study proposes virtual inertia control (VIC) combined with a fuzzy-logic-based fractional-order proportional-integral-derivative (FOPID) controller. A combination of flower pollination algorithm (FPA) and salp swarm optimization (SSO) is used to optimize the FOPID controller parameters. The proposed control system aims to enhance load frequency control (LFC) in microgrids by adapting to transient and steady-state operating conditions and effectively regulating the system power balance. The results demonstrate that the combination of VIC and the fuzzy-FOPID controller, optimized using the hybrid FPA-SSO algorithm, yields significant performance improvements across various inertia levels and RES penetration rates. The fuzzy-FOPID controller outperforms conventional proportional-integral-derivative (PID) and FOPID controllers, achieving a settling time of 8.45 ± 0.76 s and an overshoot of 9.87 ± 1.23%. Furthermore, the integral of time-weighted absolute error (ITAE) decreases to 28.76 ± 3.45, while the integral of time-weighted squared error (ITSE) decreases to 8.76 ± 1.02, indicating improved transient and steady-state performance. These findings demonstrate the improved dynamic performance and disturbance-rejection capability of the controller under low-inertia conditions. The robustness and stability of the proposed approach are assessed through stability analysis using a modified form of Matignon’s theorem. The findings suggest that the proposed control strategy is a promising solution for achieving reliable frequency regulation in future microgrids, particularly those with high penetration of renewable energy sources.