An overview of various control techniques of DVR

Power quality is the major concern in today´s electrical power system. Especially, power quality problems are continuously observed in distributed electrical power system. Mainly the voltage quality is the major aspect in distributed electrical power system. Voltage sags and voltage swells are the main parameters on which the improvement is needed. Voltage quality can be sufficiently improved in distributed electrical power systems by using some custom power devices such as dynamic voltage restorer. The Dynamic Voltage Restorer (DVR) is fast, flexible and efficient solution to voltage sag and voltage swell problems. The DVR is a power electronic based device that provides three-phase controllable voltage output, whose voltage vector-magnitude and angle-adds to the supply voltage during sag event, to restore the load voltage to pre-sag conditions. And when voltage swell occurs DVR injects 180° out of phase voltage into the line. 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.