Electronic resistor emulators for ferroresonance damping in MV transformers

Abstract

The occurrence of ferroresonances, due to the presence of voltage transformers in isolated-neutral in medium-voltage (MV) distribution grids, results in overvoltages and overcurrents that may damage the connected equipment. To prevent this phenomenon, the protection windings of the MV transformers have to be properly loaded for damping purposes. Mitigation equipment based on resistors, passive/active circuits and static converters have been proposed in the literature. This study proposes a new variety of mitigation equipment based on very simple power electronic converters operated as configurable resistor emulators. The proposed approach is evaluated theoretically and validated experimentally. A resistor emulator proof of concept is designed and applied for damping ferroresonances due to the occurrence of line-to-ground faults in isolated-neutral MV distribution power systems.