IMPROVEMENT OF POWER QUALITY IN DISTRIBUTION SYSTEM BY USING UNIFIED POWER QUALITY CONDITIONER (UPQC): (Case study: EEU, Wolaita Sodo 33kV feeder

Abstract

Good power quality is critically important for our daily use. Power quality problem encountered by a load in a feeder may be differ from other feeders and may require multipurpose conditioning device. The reasons for the disturbance of the supply systems as of Wolaita Sodo nonlinear loads, arc furnaces, welders and faults as some of the major causes. The focus of this thesis is modeling and simulation of pq theory with hysteresis band controller based Unified Power Quality Conditioner (UPQC) which is one of the recent flexible AC transmission system (FACTS) devices that includes both series and shunt active power filter operating simultaneously to mitigate voltage sag, swell and load current total harmonic distortion (THD) of power quality problems. The total load on the Wolaita sodo town 33 kV feeder is about 2.34MW and 1.35MVAR. The analytical MVA size for UPQC is found to be 1.5MVA with Vse =0.54 pu at -15o and Ish = 0.053pu at 60.61o . The UPQC scheme has effectively compensated the voltage sag of 0.8373pu and swell of 1.12pu by keeping voltage magnitude at permissible limit. The THD before integration of UPQC was found as 24.15% for both source and load voltages and 24.93% for source and load currents. After integration of UPQC to the system, the source current and load voltage THD resulted in 0.88% and 0.85% respectively