Abstract: Power quality has become a considerable issue in modern electrical power system. The extensive use of non linear load has increased the power quality problems such as stability of voltage. The voltage sags & swells affect the sensitive loads by nuisance tripping of fast acting relays. In order to overcome this power quality problem, dynamic voltage restorer (DVR) is used. The DVR injects the required amount of voltage that is necessary to maintain the system voltage stability during sags & swells. This paper describes the basic topologies for use of DVR depending up on its location in the power system.

Keywords: Dynamic Voltage Restorer, Voltage Sag, Voltage Injection Methods, Control Strategies.