Determination of excitation parameter limits for generator dynamic stability

Abstract

The voltage regulator and the excitation system are known to affect strongly the dynamic stability of a synchronous generator. This effect is often detrimental, sometimes leading even to dynamic instability. This paper concentrates on determining the excitation system parameter values for which the generator's dynamic stability becomes marginal. This defines a stable and an unstable region in the space of the dominant excitation system parameters, namely the transient or the steady state gain and the dominant time constant of the excitor-voltage regulator system. In the case of a first order excitation system model, the stability limits can be determined analytically in the form of an inequality constraint. A fourth order excitation system is also examined but this time the stability limits are computed using the concept of the gain margin. The determination of the stable region in the parameter space is an extremely useful tool for the proper selection of excitation system parameter settings.