On the damping of local-mode oscillations in power systems by time-scale decomposition

The present paper demonstrates that the local-mode oscillations of a turbin e-generator system are due to the influence of the electrical dynamics on m echanical dynamics and can therefore be attenuated by an efficient decoupli ng of these two dynamics. This assertion is supported by an analysis based on the time-scale decomposition principle and nonlinear simulation results. Furthermore, the dynamics decoupling can only be realized by stabilizing t he electrical dynamics more quickly. Since the dominant pole of the electri cal dynamics is related to the field excitation circuit, it is shown that t he appropriate tuning of the automatic voltage regulator permits creation o f a significant strip between the electrical and mechanical dynamics. Moreo ver, it is shown that if the strip is further increased by the use of a pol e-placement-based state feedback controller, then the local-mode oscillatio ns are dramatically attenuated.