A Dual UPQC to Mitigate Sag/Swell, Interruption, and Harmonics on Three Phase Low Voltage Distribution System

Abstract

The Unified Power Quality Conditioner (UPQC) is a combination of a series active filter (SeAF) and a shunt active filter (ShAF) connected in parallel by a DC link capacitor. This device can mitigate power quality (PQ) problems i.e. sag/swell, harmonics, and unbalance on the source and load bus of threephase three-wire (3P3W) on low voltage distribution systems simultaneously. The disadvantage of UPQC is that it is unable to overcome the voltage interruption so that the source can not deliver power to the load. This paper proposes a dual UPQC model to overcome the voltage interruption on the source bus so that the load bus continues to get power supply. There are six disturbance cases i.e. sinusoidal supply-sag-non-linear load (SSag-NL-L), sinusoidal supply-swell-NL-L (S-Swell-NL-L), sinusoidal-interruption-NL-L (S-Inter-NL-L), distorted supplysag-NL-L load (D-Sag-NL-L), distorted supply-swell-NL-L (DSwell-NL-L), and distorted supply-interruption-NL-LL (DInter-NL-L). The proportional Integral (PI) method is used to control the SeAF and the ShAF in the dual UPQC circuit model. The simulation results show that in the D-Inter-NL-LL case, a Dual UPQC model can maintain a load voltage magnitude of 266.60 V (voltage drop only of 14%), higher compared to a Single UPQC model of 173.97 V (voltage drop of 43.88%). In the same case, a dual UPQC model is capable of resulting in an average total harmonics distortion (THD) of load voltage of 10.10%, lower compared to a single UPQC model of 26.70%.