A 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.