JEE_V4_N3_RP3 Yash Pal A. Swarup Bhim Singh Journal on Electrical Engineering 2230 – 7176 4 3 23 31 Active Powers Filter (APF), Power-Factor Correction, Load Balancing, UPQC, Voltage and Current Harmonics, Neutral Current Compensation, Star-Hexagon Transformer In this paper, a new topology is proposed for a three-phase four-wire (3P4W) distribution system utilizing a star-hexagon transformer along with three-phase three-wire (3P3W) Unified Power Quality Conditioner (UPQC). In this proposed topology the neutral point of the star connected transformer, used for the connection of series active power filter (APF) of 3P3W UPQC, is utilized as a fourth wire for 3P4W distribution system. The star-hexagon transformer is connected near the load to compensate the neutral current that may flow toward the neutral point of the series transformer of series APF. The series and shunt APF of 3P-3W UPQC are realized by readily available three-leg voltage source inverters (VSIs). For the mitigation of different power quality problems a control technique based on synchronous reference frame (SRF) theory is used for the control of UPQC. In this control scheme of UPQC, the current/voltage control is applied over the fundamental supply currents/voltages instead of fast changing APFs currents/voltages, there by reducing the computational delay. With the connection of star-hexagon transformer, no extra control is required for the neutral current; hence required numbers of current sensors are reduced. The performance of the proposed topology of UPQC is analyzed through simulations results using MATLAB software with its Simulink and Power System Block set toolboxes. January - March 2011 Copyright © 2011 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=1396