Mitigation of voltage sags with phase jump using a dynamic voltage restorer

A Dynamic Voltage Restorer is a series-connected device. The main purpose of this device is to protect sensitive loads from sags/swells and interruptions in the supply side. This is accomplished by rapid series voltage injection to compensate for the drop/rise in the supply voltage. This voltage injection can be accomplished in one of three ways: pre-sag compensation, in-phase compensation, and phase-advance compensation. All three methods are discussed. Different control strategies for a dynamic voltage restorer are examined with an emphasis on the compensation of voltage sags with phase jump. Voltage sags with phase jumps are in some instances more apt to trip loads. A suitable compensating voltage series injection is more difficult to attain. Different control methods to compensate voltage sags accompanied by a phase jump are investigated and compared. Two control methods are analyzed with simulations performed in SIMULINK.