Damping Torques of Multi-Machine Power Systems During Transient Behaviors

A Weierstrass-based numerical method for computing damping torque of a 3-machine power system during transient period is proposed and evaluated. Numerical studies were performed to demonstrate mutual impacts of generators on the damping torque, when one of the generators is presented by a detailed model. The relationship between the averaged self-damping torque coefficient of the detailed model and the damping coefficient of the classical model is numerically studied. One interesting observation from our studies is that the damping torque coefficients tend to become zero at the end of transient stability period if all the generators are represented by the detailed model. This observation can be useful to determine the duration of transient stability period. One application of the proposed Weierstrass-based method is to determine appropriate and accurate damping terms for power system dynamic simulation.

I. Introduction

The importance of appropriate damping representation has been recognized in power system transient stability analysis. In detailed generator models, the damping torque is included in the electric torque because an explicit damping torque expression is not available. For multi-machine power systems, the damping torque of a generator depends not only on its own parameters, network topology, load behaviors and excitation system, etc, but also on other generators. It makes the work on determining the damping torque of a generator challenging.