Effect of synchronous machine damper windings and magnetic saturation on low-frequency oscillation damping

Effect of damper windings and magnetic saturation of synchronous machine on LFO(Low-Frequency Oscillation) damping are studied with eigen analysis method.Both the 3rd-order linearized model of the synchronous machine and the 6th-order linearized model including damper windings are established with consideration of the effect of magnetic saturation,which are used in the analysis of LFO damping for single-machine infinite bus system.The computation and analysis indicate that:the 3rd-order model is not appropriate to LFO analysis when the synchronous machine is phase-leading running or under light load,independent of PSS(Power System Stabilizer)and magnetic saturation.However,it will provide precise results when the synchronous machine is running in normal condition.The effect of magnetic saturation is not significant when the 6th-order model is used for a synchronous machine except the machine is phase-leading running with PSS.Effect of damper windings and magnetic saturation should not be neglected in LFO analysis.