This research study presents a comprehensive comparative analysis of two controllers, namely the HHO-PI and PI, for regulating the DC link voltage of a Unified Power Flow Controller.The objective was to assess the action of these controllers in terms of transient response, robustness, power flow control, and power quality. The results show that the HHO-PI controller outperforms the PI controller in terms of transient response, robustness, power flow control, and power quality. The HHO-PI controller's hybrid harmony search optimization algorithm enhances optimization capabilities, leading to improved performance in adapting to changing operating conditions and maintaining a stable DC link voltage. It also achieves smoother tracking of active and reactive power references, resulting in better power flow management and increased system stability. The HHO-PI controller yields significantly lower Total Harmonic Distortion (THD) values, indicating improved power quality. These findings highlight the superiority of the HHO-PI controller for UPFC systems.

UPFC system, HHO-PI, modular multilevel converter, etc.