Centralized control of transformer tap changing for voltage stability enhancement

This paper presents a novel centralized control scheme for load tap-changing transformers. To implement the coordinated tap changing, by taking into account interaction among different transformers, the developed scheme employs successive linearization and variable-structure control techniques. The designed mechanism can be a partial implementation of the full scheme. With appropriate simplification, only the local information, associated with the participating transformers, is needed to perform the control. In preventing the voltage instability, brought about by lack of coordination among tap changers, the developed scheme is superior to conventional decentralized methods.