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Scope
This guide contains instructions for modeling synchronous machines in direct- and quadrature-axis equivalent circuits, along with the basic transient and subtransient reactance/time-constants model in view of stability studies. It discusses assumptions made in using various models and presents the fundamental equations and concepts involved in generator/system interfacing. The manner in which generator saturation is treated in network studies, both in the initialization process as well as during large or small disturbance stability analysis procedures is addressed. Approaches for improving the accuracy of field and excitation system quantities are identified and conversion factors are given for transferring field parameters from one base to another for correct generator/excitation system interface modeling. Parameter determination and translation from equivalent-circuits to operational impedances or vice-versa is covered. Data analysis methods for obtaining these parameters using measurements from field tests or finite-element computations are explained and illustrated with a wide range of generator and test data. However, this guide refers to applicable standards (such as IEEE Std 115) or contract specification for scheduling such tests. Also, this guide does not attempt to recommend specific procedures for machine representation in non-standard or atypical cases such as generator tripping and overspeed operation or models for harmonics or unbalanced operation.
Purpose
The modeling of synchronous machines for stability studies and analyses is subject to continuing review and possible improvements. The guide addresses both parameter identification for static and dynamic stability analyses while accounting for generator saturation. Emphasis is placed on discussing various aspects of synchronous generator/power system interactions in steady and dynamic operation modes
Abstract
Revision Standard - Active.Categorized in this guide are three direct-axis and four quadrature-axis models, along with the basic transient reactance model. Also discussed are some of the assumptions made in using various models. The fundamental equations and concepts involved in generator/system interfacing are presented. Covered, generally, are the various attributes of power system stability, recognizing two basic approaches. The first is categorized under large disturbance nonlinear analysis; the second approach considers small disturbances, where the corresponding dynamic equations are linearized. Applications of a range of generator models are discussed and treated. The manner in which generator saturation is treated in stability studies, both in the initialization process as well as during large or small disturbance stability analysis procedures is addressed. Saturation functions that are derived, whether from test data or by the methods, of finite elements are developed. Different saturation algorithms for calculating values of excitation and internal power angle depending upon generator terminal conditions are compared. The question of parameter determination or verification is covered. Two approaches in accounting for generator field and excitation system base quantities are identified. Conversion factors are given for transferring field parameters from one base to another for correct generator/excitation system interface modeling, Suggestions for modeling of negative field currents and other field circuit discontinuities are included.
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