Damping property in power system transient behaviors

Power system transient behavior is subject to impact of several types of damping. Based on the Weierstrass approximation theorem, a numerical method is proposed to calculate the damping torque and damping coefficient of power system described by detailed model, no matter that the post-fault system is stable or not. Investigation on the single-machine-infinite-bus system discloses the transient damping with different generator parameters relative to transient losses, load condition and modeling hypotheses. The result indicates that, for the studied system, neglecting armature resistance, or neglecting the rate of change of flux terms and rotor speed deviation in armature voltage calculation may cause the average damping coefficient approaching zero. The torque-speed characteristics and network transients have very small influence on average transient damping. The work helps to identify the main factor that affects transient behaviors and provide evidence for reasonable modeling hypothesis and model selection in transient stability assessment.