Control strategies for dynamic voltage restorer compensating voltage sags with phase jump

Voltage sags are an important power quality problem and the dynamic voltage restorer is known as an effective device to mitigate voltage sags. In this paper, different control strategies for a dynamic voltage restorer are analyzed with emphasis put on the compensation of voltage sags with phase jump. Voltage sags accompanied by a phase jump are in some cases more likely to trip loads and a satisfactory voltage compensation are more difficult to achieve. Different control methods to compensate voltage sags with phase jump are proposed and compared. Two promising control methods are tested with simulations carried out in Saber and finally tested on a 10 kVA rated dynamic voltage restorer in the laboratory. Both methods can be used to reduce load voltage disturbances caused by voltage sags with phase jump. One method completely compensates the phase jump, which is the best solution for very sensitive loads. The second method does only partly compensate the phase jump, but it is expected to have a better performance in compensating a broader range of voltage sags.