Performance Improvement of Power Quality Using Dynamic Voltage Restorer in Distribution Networks

Abstract

Voltage sags, swells, unbalance, and waveform distortion can interrupt sensitive industrial and commercial loads even when the average reliability of a distribution feeder is high. This methodology paper develops a compact Dynamic Voltage Restorer (DVR) framework for improving load-side power quality through fast series-voltage injection. The proposed study uses a three-phase distribution-network model in which a voltage-source inverter, dc-link energy unit, series injection transformer, passive filter, and synchronous-reference-frame control are coordinated to detect disturbances and synthesize the missing voltage. Balanced and unbalanced voltage sags, voltage swell, and harmonic-rich conditions are considered. Performance is evaluated from load RMS voltage recovery, total harmonic distortion (THD), voltage-unbalance factor, response time, and required injected voltage. A representative numerical evaluation shows that a 0.55 p.u. sag can be restored to approximately 0.98–1.00 p.u., while the load-voltage THD and unbalance are reduced to levels suitable for sensitive loads. The methodology therefore provides a reproducible basis for comparing DVR control settings and compensation modes in medium- and low-voltage distribution studies.