Hybrid Voltage Sag/Swell Compensators: A Review of Hybrid AC/AC Converters

The parameters of electrical energy, such as supply voltage amplitude, are very important, especially from the viewpoint of the final consumer with respect to sensitive loads connected to the grid. Dynamic states in the power grid-voltage sags and swells-might cause faults and defects to develop in sensitive loads. To mitigate unwanted effects, many topologies of ac/ac converters are implemented as voltage compensators. This article presents a review of hybrid ac/ac converters designed to compensate voltage sags and swells with the aim of protecting sensitive loads against sudden and severe changes in supply voltage amplitude. In this article, only solutions without galvanic separation between source and load are described. To assess the properties and to compare different topologies of voltage compensators, some common parameters, such as range of voltage sag and swell compensation, reliability, quantity of switches and transformers, and required power ratings of power electronic units in relation to power of load, are introduced. In addition, we discuss possibilities for compensation of voltage interruption, time of compensation, the efficiency, and the effect on the supply network of the described circuits. The results of the analysis have been collected and compared in tabular form and represented in graphical form. Furthermore, we show potential areas of application for particular solutions of ac voltage compensators.