New hysteresis control band of an unified power quality conditioner

Power quality problems have received a great attention nowadays because of their economical impacts on both utilities and customers. The current harmonics is the most common problem of power quality, while voltage sags is the most severe. This paper deals with an Unified Power Quality Conditioner for current and voltage perturbations compensation in a power distribution network. The topology is based on two 3-phase voltage source inverters acting respectively as a parallel active power filter and a series active power filter which share two DC link capacitors. The power flow, in the Unified Power Quality Conditioner system is analysed. A novel hysteresis current and voltage control methods of Unified Power Quality Conditioner are studied with the aim to have robust control of the output voltage of series part and the output current of the parallel part. The DC voltage controller optimizes the energy storage of the DC capacitor where a fuzzy logic controller is developed. Simulation results are presented and discussed to verify the dynamical behaviour of the Unified Power Quality Conditioner and to show the effectiveness of the used perturbation identification methods and hysteresis band adaptive controllers. (C) 2011 Elsevier B.V. All rights reserved.