A frequency-response method for the predetermination of synchronous-machine stability

The paper presents a new concept for the predetermination of synchronous-machine stability. The concept is based on the realization of a basic closed-loop pattern for a synchronous generator, which, when established, can be subjected to the frequency-response procedure of the Nyquist stability criterion. The basic closed-loop pattern emerges from the application of small-displacement theory to Park´s equations for a synchronous generator. The method is applicable to a machine with or without a voltage regulator, but is more useful in the latter case, and this forms the majority of the applications presented in the paper. It is shown that, as a by-product of the analysis, expressions for the damping in a synchronous machine may be derived. Since this is considered to be of some interest, the influence of some of the more important parameters of the machine and regulator on the damping coefficient is demonstrated.