Power Quality Enhancement under Unbalanced Load Conditions Using a Dynamic Voltage Restorer and Fuzzy Logic-Controlled Shunt Active Power Filter

Author

Neelam Verma, Kavita Choudhary


Abstract

 Sensitive industrial and commercial loads are increasingly affected by voltage sag, swell and harmonic distortion caused by unbalanced faults and non-linear loads on the distribution network. This paper presents a combined power quality enhancement scheme that uses a Dynamic Voltage Restorer (DVR) for series voltage compensation under unbalanced load and fault conditions, together with a Fuzzy Logic-Controlled Shunt Active Power Filter (SAPF) for harmonic mitigation. The DVR, controlled through a PI-regulated injection scheme, restores the load-side voltage following double-line-to-ground faults, while the shunt APF, driven by a two-input two-output Mamdani-type fuzzy logic controller, regulates the DC-link voltage and injects a compensating current to cancel load current harmonics. Both devices were modeled and simulated in MATLAB/Simulink under a three-phase 400 V, 50 Hz test system with an unbalanced parallel load and a non-linear industrial drive. The DVR restored the load voltage to its pre-fault value within milliseconds of a double-line-to-ground fault, and the fuzzy-controlled SAPF reduced the Total Harmonic Distortion (THD) of the source current from 2.32% (uncompensated) to 1.07%, outperforming a conventional PI-controlled filter (1.85% THD) and a reported hysteresis-controlled filter (1.250% THD) evaluated under comparable unbalanced-load conditions. The results confirm that combining a DVR with a fuzzy-controlled SAPF provides an effective, IEEE 519-compliant solution for power quality enhancement in distribution networks subject to unbalanced loading and harmonic-rich non-linear drives.



Keywords

Dynamic Voltage Restorer (DVR); Shunt Active Power Filter (SAPF); Fuzzy Logic Controller; Power Quality; Unbalanced Load; Total Harmonic Distortion (THD); Voltage Sag and Swell.



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References


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