The borrow damping phenomena of PSS control is clarified according to the mathematic character of eigenvalues, that is the damping which PSS afford to electromechanical mode is transferred from non-electromechanical mode.

• 根据考虑PSS控制的线性化系统模型,利用特征值的数学性质,揭示了PSS控制过程中的借阻尼现象,即:PSS提供给机电振荡模式的阻尼是从非机电模式转移来的。