Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Electrical and Computer Engineering


Traditionally, the Transient Energy Function (TEF) method has used the "classical model" of the generator which assumes constant voltage behind transient reactance. However, increased use of high initial response exciters has made the task of first swing stability study more complex. Fast response exciters interfere in the first swing, making the classical model not adequate for modeling the generator;In the research conducted for this dissertation, an energy function is obtained to incorporate the effect of exciter in the first swing. The Unstable Equilibrium Points (UEPs) are obtained in the space of rotor angles, direct and quadrature axis internal voltages, and the field voltages;The philosophy of approach has been to model the first swing phenomenon, which is an inertial transient, as affected by the exciter, rather than trying to duplicate time solution. It is assumed that the machine flux does not change abruptly after removal of the disturbance and its variation can be approximated by a constant (average value between clearing time and UEP). Based on this assumption, an energy function has been derived which is simple and is similar to that of classical model. UEPs are obtained using a variation of Newton-Raphson technique. Several other approaches to deriving energy function are investigated and the difficulties associated with them are mentioned;This procedure has been simulated on several test power networks for a variety of test conditions. Transient ability is assessed successfully and compares well with time solution results. In situations that exciter alters the mode of instability, obtaining the relevant UEPs and proper assessment becomes difficult and requires further investigation.



Digital Repository @ Iowa State University,

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Khashayar Nodehi



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119 pages