In this paper

the damping torque analysis is applied in a multimachine power system installed with FACTSbased stabilizers and PSSs

which leads to the establishment of a multichannel model describing the pattern of the stabilizers to provide damping to the oscillation modes in the power system. Based on the model

an index is proposed to evaluate the robustness of the stabilizers to the variations of system operating conditions. One application of the index proposed is demonstrated to select the operating condition of the power system

at which the stabilizers are designed to ensure their robustness. This demonstration also reveals the inherent disadvantage of simultaneous tuning techniques for the coordinated design of multiple stabilizers in multi-machine power systems.