POWER-QUALITY ENHANCEMENT IN DISTRIBUTION NETWORKS USING A UNIFIED POWER QUALITY CONDITIONER

Abstract

Power-quality disturbances in modern distribution networks are increasing because of nonlinear loads, power-electronic converters, distributed renewable generation, voltage fluctuations, unbalanced loading, and rapidly changing consumer demand. Voltage sag, voltage swell, harmonic distortion, reactive-power imbalance, and current distortion can adversely affect sensitive electrical equipment and reduce overall network performance. This study presents a Unified Power Quality Conditioner based approach for simultaneous compensation of voltage- and current-related disturbances in a three-phase distribution network. The proposed system consists of series and shunt voltage-source converters connected through a common dc-link capacitor. The series converter compensates supply-side voltage disturbances, while the shunt converter mitigates load-current harmonics, reactive current, and current imbalance. A synchronous-reference-frame control strategy with pulse-width modulation is considered for reference generation and converter operation. Representative simulation results show that source-voltage THD can be reduced from 8.2% to 2.1%, load-current THD from 12.6% to 2.8%, and voltage sag from 0.78 pu to approximately 0.99 pu. The results demonstrate that coordinated UPQC compensation can significantly improve distribution-system voltage quality, current quality, and overall operating performance.