New Robust Control Design Based on Feedback Compensator for Sssc

In this paper, the modified linearized Phillips-Heffron model is utilized to theoretically analyze a single-machine infinite-bus (SMIB) installed with SSSC. Then, the results of this analysis are used for assessing the potential of an SSSC supplementary controller to improve the dynamic stability of a power system. This is carried out by measuring the electromechanical controllability through singular value decomposition (SVD) analysis. This controller is tuned for simultaneously shifting the undamped electromechanical modes to a prespecifed area in the s-plane. The issue of designing a robustly SSSC- based controller is considered and formulated as an optimization problem according to the eigenvalue-based multi-objective function consisting of the damping ratio of the undamped electromechanical modes and the damping factor. Next, considering its high capability to find the most optimistic results, the Gravitational Search Algorithm (GSA) is used to solve this optimization problem. Wide ranges of operating conditions are considered in design process of the proposed damping controller in order to guarantee its robustness. The effectiveness of the proposed controller is demonstrated through eigenvalue analysis, controllability measure, nonlinear time-domain simulation and some performance indices studies. The results show that the tuned GSA based SSSC controller which is designed by using the proposed multi-objective function has an outstanding capability in damping power system low frequency oscillations, also it significantly improves the power systems dynamic stability.