IBSMFO-Optimized UPQC-DG Control for Harmonic Mitigation in Hybrid Renewable Microgrids

Distributed generation (DG) systems are increasingly integrated into modern power networks through power-electronic interfaces. However, the presence of nonlinear loads and power-electronic converters introduces harmonic distortion, which can significantly degrade power quality, particularly in three-wire systems. This study investigates harmonic mitigation in a hybrid renewable DG system incorporating solar, wind, fuel-cell-based generation, and grid-connected operation using a Unified Power Quality Conditioner (UPQC). An Improved Bat Search–Moth Flame Optimization (IBSMFO) based control strategy is proposed for optimizing the proportional-integral (PI) controller parameters of the UPQC. The IBSMFO algorithm combines the search characteristics of the Improved Bat Search Algorithm (IBSA) with the Moth Flame Optimization Algorithm (MFOA) to minimize the selected error-based objective function and enhance the dynamic performance of the compensation system. The proposed UPQC is evaluated under ideal and non-ideal source-voltage conditions with nonlinear loads. Simulation results demonstrate effective mitigation of voltage and current harmonics and improved power quality. In particular, the source-current THD is reduced to 4.03% under the operating conditions considered, while a minimum THD of 1.01% is achieved under the corresponding compensation condition. The results confirm that the proposed IBSMFO-optimized UPQC provides effective harmonic compensation and improved power quality performance in hybrid renewable DG systems.