DYNAMIC VOLTAGE RESTORER FOR VOLTAGE QUALITY IMPROVEMENT

Power quality has become a major area of concern in present era due to the increase in modern sensitive and sophisticated loads connected to the Distribution System. The various power quality problems are voltage sag, swell, transient, disturbances, etc. These power quality related problems can be solved with the help of various custom power devices. Dynamic voltage restorer (DVR) is one of the most effective custom power devices which have been popular for the protection of sensitive loads from voltage sags. It is fast, flexible and efficient solution to voltage sag problem and is power electronic based device that 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. It can restore the load voltage within few milliseconds. They employ a series of voltage boost technology using solid state switches for compensating voltage sags/swells. The DVR applications are mainly for sensitive loads that may be drastically affected by fluctuations in system voltage. The DVRs are used for providing reliable distribution power quality. In this paper, an overview of the dynamic voltage restorer (DVR), its components, functions, compensation and control methods are reviewed along with the device capabilities and limitations.