Abstract: The most common and serious power quality problem is voltage sag and causes more economic losses. The definite solution for voltage related power quality problems is DVR. The conventional topologies operate with a dc link which imposes limits on the compensation capability of the DVR. This paper analyzes the characteristics of voltage dips in power systems with special emphasis on symmetrical components analysis and unbalanced dips with an ac-ac converter topology to mitigate voltage sags. These topologies require instantaneous voltages at the point of common coupling. A generalized dip model is built for all unbalanced dips, taking into account the fault types and load connections. Detailed simulations to support the same have been carried out in MATLAB, and the results are presented.

Keywords: Dynamic voltage restorer (DVR), voltage dips, power quality, instantaneous symmetrical components.