Transformerless single-phase UPQC for large scale LED lighting networks

Abstract

The paper presents a comprehensive Power Quality (PQ) solution to improve grid current harmonics and light intensity flickers in large scale LED lighting networks. Low cost and low power LED lamps exhibit current harmonic contents due to their nonlinear characteristics. A large scale lighting network requires tens to hundreds LED lamps installation, the resultant harmonic currents pollute the grid seriously. Furthermore, Light intensity fluctuations are becoming a concern nowadays to many users, as safety and health problems. This phenomenon is mainly caused by heavy loads as they lead to voltage fluctuations and deteriorating in PQ and hence visual flickering in LED lamps. This paper proposes a single phase transformerless half-bridge unified power quality conditioner (UPQC) topology with its controls to mitigate most of PQ problems in a network. An active power filter injects harmonic currents and reactive current to provide unity power factor and a dynamic voltage restorer quickly supports the load voltage for any voltage dip, swell or flickering in the network. The performance of the proposed UPQC has been verified by simulations, and small signal models have been determined. A 500VA/120V prototype has been built to verify the models. Experimental results, steady-state characteristics and stability study are given in the paper. The experimental results have a good agreement with the theoretical findings.