William Robert Pearson

Integral of accelerating power type PSS. I. Theory, design, and tuning methodology

The basic theory of a PSS control based on integral of accelerating power input signal and the methods of tuning the stabilizer are explained in this paper. Small signal linearized analysis using frequency domain techniques (bode plots and root locus) are used to illustrate the process of tuning the PSS controls. Although much of the technical information has been previously formed, the benefit of this paper is to show clearly the entire process together with an example case study. Also, some aspects of the digital-based excitation controls which facilitate the implementation are explained. The methodology for tuning the PSS is applicable to other designs which have different algorithms and input signals.

Excitation system protective limiters and their effect on volt/VAr control-design, computer modeling, and field testing

The action of excitation system protective limiters and VAr regulation are often not taken into account in planning studies, and actual units may be quite different than simulations. This may lead to incorrect predictions of actual stability limitations, or even voltage collapse phenomena. The design of the excitation system protective limiters such as over excitation limiters (OEL), under excitation limiters (UEL) and volts/hertz (V/Hz) is explained, and models presented. For system events where these controls and limiters may become active, modeling in transient stability studies is important to correctly predict volt/VAr performance. Specific models applicable to the GE EX2000 digital-based control systems are shown for reference, although the general concepts discussed here are applicable to any other excitation equipment. An important aspect of the new digital-based excitation controls is that they allow for more intelligent limiter functions and protective features not convenient with older equipment. Test procedures and results are shown to illustrate the limiter performance.