Numerical Investigation on the Damping Property in Power System Transient Behavior

Power system damping in the transient condition generally depends on system parameters and modeling hypotheses. The dependence can be very nonlinear. In this paper, a polynomial approximation method is proposed to obtain a representation of the damping torque and damping torque coefficient of the original detailed stability model. Investigation on the single-machine-infinite-bus system reveals that the damping torque coefficient is not a constant in transient condition. The generator parameters relative to transient loss have significant impact on transient damping. In addition, the impact from excitation system, load, transmission line and modeling hypotheses are also investigated. It is found that the influences of torque-speed characteristics and network transients on transient damping are very small. This work provides insight in identifying the main factors that affect power system transient behavior. These factors are useful to build appropriate models for transient stability analysis.