Practical and Flexible Incorporation of AVR into Extended Equal Area Criterion

Abstract

Automatic voltage regulator (AVR) models, additions to transient salicncy, are incorporated into extended equal area criterion (EEAC) for transient stability assessment of power systems in this paper. This is a further development of a previous paper where the EEAC has been successfully extended to constant Eq' models to consider transient saliency. The present paper further defines two equivalent machines with equivalent AVRs, which arc likely responsible for the possible separation. The transient stability of multimachine systems of any size, where machines may have various AVR parameters or no AVRs, can always be represented by only six first order differential equations. To these, instead of to multimachine state equations of high dimension, implicit integration is applied. With parametrizing AVR's effects on transient stability, renewed parameters of a one—machine infinite—bus system arc applied to the energy function with classical models, which contains only two items, i.e. kinetic and potential energy. Un-like in other literature, angle diffcrcncc between E' and Eq' and that between Vtand Eq' are neither neglected nor treated as constant in this study. Besides, transient saliency of individual machine, being usually excluded in the literature on direct methods with AVRs, is preserved here. Extensive test results on several practical power systems, concerning the accuracy and robustness with respect to various faults, transient saliency and AVR profiles, are reported in this paper. These fully confirm the significance of this extension and validate the feasibility of its practical applications.