Voltage Quality Improvement by using Facts Devices

This paper presents the analysis and control of a dynamic voltage restorer (DVR) and a unified power flow controller (UPFC) for the compensation of voltage sag/swell. A Unified Power Flow Controller (UPFC) is an electrical device for providing fast-acting reactive power compensation on voltage electricity networks. Dynamic Voltage Restorer (DVR) is a custom power device used in power distribution networks to protect consumers from sudden sags and swells in grid voltage. Voltage sag/swell is one of the most important power quality problems challenging the utility industry. The DVR provides three-phase controllable voltage source, whose voltage vector (magnitude and angle) adds to the source voltage during sag event, to restore the load voltage to pre-sag conditions. The DVR is designed for protecting the whole plant with loads in the range of some MVA. The DVR can restore the load voltage within few milliseconds. A new topology based on Z-source inverter is presented in order to enhance the voltage restoration property of dynamic voltage restorer. The modeling of Z-source based dynamic voltage restorer and UPFC is carried out component wise and their performances are analyzed using MATLAB software.