Nonlinear modal analysis of interaction between torsional modes and SVC controllers

Abstract

This paper deals with the use of Modal Series (MS) method to study the nonlinear interaction between<br><br>the torsional modes of a turbine-generator set and Static VAr Compensator (SVC) in the stressed power<br><br>systems. The observations resulting from nonlinear simulations made incentive for suggesting the need<br><br>for nonlinear analysis of torsional interaction phenomenon in stressed conditions. The obtained results<br><br>from linear modal analysis were not consistent with those of nonlinear simulations and could not quantify<br><br>the problem. While the results of nonlinear analysis MS method reveal that, the nonlinear interactions<br><br>exist between shaft sections and SVC controllers. In the stressed conditions, these nonlinear interactions<br><br>become more pronounced and it may be a warning for severe damage of shaft segments. By using the<br><br>indices correspond to the MS method, the nonlinear interactions of torsional modes are evaluated for<br><br>different conditions. To demonstrate the physical effects of nonlinear interaction of torsional modes<br><br>with SVC controllers, the torsional torques imposed on shaft sections are provided using the nonlinear<br><br>simulations. Finally, based on MS method a supplementary controller is designed for SVC to remedy the<br><br>problem. The proposed approach is implemented on the IEEE 4-machine 11-bus test system.