Voltage sag correction by dynamic voltage restorer with minimum power injection

Abstract

A dynamic voltage restorer is a power quality device used to correct the voltage disturbances by injecting voltage as well as power into the system. A method of determining the exact amount of voltage injection required to systematically correct a specific voltage drop with minimum active power injection is described in this letter. Analytical expressions for both the magnitude and angle of the injected voltage are also derived. It has been found that a voltage drop of less than (1-pf)pu can easily be corrected without injecting any active power. For higher voltage drop, injection of active power is essential but its value can be minimized by drawing power from the supply at unity power factor.