PSS design for multi-area system based on combined sensitivity concept

Many PSS tuning methods have been addressed to improve the electromechanical mode damping only. In this paper, the tuning criteria are extended to take into account the instabilities due to the reaction between the excitation and PSS, as well as the interaction between multi-PSSs. The analytical tool of sensitivity has been exploited for the PSS tuning and the settings are optimal if the sensitivity coefficient is approaching zero. The design criteria of a single PSS are to maximize the interarea mode whilst keeping a constant gain margin for the PSS-excitation instability. However, in the multi-PSS design, the criteria are slightly modified because of the additional interaction between the PSSs.