Analysis and Study of Subsynchronous Torsional Interactions with FACTS Devices

Abstract In this article, a general approach based on interconnected dynamical system theory and linear analysis techniques is proposed for the analysis and char-acterization of subsynchronous torsional interaction (SSTI) with flexible AC transmis-sion system (FACTS) devices. The method makes use of modal analysis techniques and enables detailed representation of the electrical transmission network dynam-ics and FACTS devices. Analytical and graphical methods of assessing the extent of SSTI with FACTS devices are given and techniques for interpreting modal interaction are discussed. A detailed case study with the IEEE first benchmark model for sub-synchronous resonance studies is used to investigate the potential for SSTI between FACTS controllers and the torsional modes of stability. The influence is discussed of control strategy and mode of operation of FACTS controllers on the damping of torsional modes