Power Quality Improvement in Distribution Networks Using FACTS Devices

Abstract

Modern distribution networks increasingly supply nonlinear, unbalanced, and electronically controlled loads, making voltage sag, voltage swell, harmonic distortion, poor power factor, and load unbalance important power-quality concerns. This methodology paper develops a comparative framework for improving distribution-system power quality using Flexible AC Transmission System (FACTS)-derived custom-power devices, with emphasis on the Distribution Static Compensator (D-STATCOM), Dynamic Voltage Restorer (DVR), and Unified Power Quality Conditioner (UPQC). A three-phase 11-kV, 50-Hz distribution feeder is modeled with a nonlinear rectifier load and variable reactive demand. Disturbances are introduced through programmed voltage sag/swell events and nonlinear current injection. The D-STATCOM is configured for shunt reactive-current and harmonic compensation, the DVR for series voltage restoration, and the UPQC for coordinated series-shunt compensation through a common dc link. Synchronous-reference-frame transformation, proportional-integral dc-link regulation, and pulse-width modulation are adopted as the common control basis. Performance is assessed using load-voltage magnitude, source-current total harmonic distortion (THD), voltage THD, power factor, dc-link stability, and disturbance-recovery time. Literature available up to 2016 shows that converter-based compensators provide faster and more versatile mitigation than conventional passive compensation, while UPQC offers the broadest simultaneous correction of voltage- and current-related disturbances. The proposed methodology is suitable for MATLAB/Simulink or PSCAD implementation and provides a reproducible basis for comparing device capability, rating, and control complexity in radial distribution networks.