Robust control of SSSC to improve torsional damping

In this paper, the H/sub /spl infin// optimal control theory has been used to design a robust controller for regulating DC link voltage of a static synchronous series compensator (SSSC). Subsynchronous resonance (SSR) analysis of the robust SSSC compensated power system is presented. The power system used in this study is the IEEE first benchmark model for SSR analysis. To design the robust controller the nominal transfer function is reduced to such an order that the essential dynamic characteristics of the system are retained in the frequency range of interest. Eigenvalue analysis and nonlinear simulation using PSCAD/EMTDC have shown that the controller can provide satisfactory torsional performance under a wide variation in the operating conditions. A damping controller is also proposed to increase the damping of the torsional modes.