Damping Torque Analysis Based on Extended C1 ~ C15 Model with Consideration of Under Excitation Limiter and Damping Windings

摘要

Under-excited limiter (UEL) is one of the important auxiliary functions in generator excitation system. It has significant influence on the small signal stability of power system. However, the conventional analysis method based on Heffron-Phillips model does not consider the dynamic action of damping windings effectively. Based on the one machine infinite bus C₁ ~ C₁₂ model including the damping windings, the extended C₁ ~ C₁₅ model with consideration of UEL is derived. The mechanism of the system damping weaken by superimposed type of UEL is proposed based on the principle of superposition and electromagnetic torque analysis method. The results show that the electromagnetic torque provided by UEL through the main excitation channel weakens the system damping and the electromagnetic torque generated by UEL through q-axis damper winding enhances system damping. The damping torque provided by UEL reduces as the boundary line slope of UEL increases until the positive to negative. The total damping torque of the system is greatly reduced as the UEL boundary line slope increases.