Power Quality Improvement For Critical/Unbalanced Loads Using UPQC

Abstract

This paper presents control strategy of three phase four wire UPQC (unified power quality conditioner) to improve power quality. A case study at the hospital is taken for the study of power quality issues. To improve upon certain problems observed, one of the customer power devices called UPQC is mentioned. UPQC consist of combine series active filter and shunt active filter. The former compensates voltage harmonics and the latter will compensate harmonic currents of non-linear load. The proposed UPQC system can improve the power quality at the point of common coupling on distribution system under unbalanced load conditions. The 3P4W UPQC systems control strategy to balance the unbalanced load currents is presented in this paper. The neutral current that may flow towards transformer neutral point is compensated by using a four-leg voltage source inverter topology for shunt part. Hence, the series transformer neutral will be at virtual zero potential. A simulation study of the proposed topology has been carried out using MATLAB/ SIMULINK and the results are presented.