Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Electrical Engineering


Professor Robert T.H. Alden


Professor Raymond D. Findlay

Committee Member

Professor Mohamed A. El-Kady


The value of the time domain simulation technique for power system transient stability analysis can be greatly enhanced if it can indicate the degree of stability by producing a stability index. Often referred to as Energy Margin, the stability index offers additional insight into the transient stability problem being studied, and has the capability of speeding up transient stability limit derivations. Moreover, energy margins also have potential applications in dynamic contingency ranking and screening.

This thesis presents a new method, called the Relevant Fault-on Trajectory (RFT) method, for incorporating energy margin calculations into time domain simulations. The proposed method is based on the determination of the additional energy absorbing capability of the critical generator group, at the instant when the transient kinetic energy injected into this group by the disturbance is fully absorbed. The additional energy absorbing capability is obtained through the simulation of a relevant fault-on trajectory. The RFT method computes energy margins efficiently and reliably for systems exhibiting either plant mode or area mode stability problems.

The practicality of the proposed method has been successfully demonstrated on a 27-generator, an 89-generator, and a 144-generator system. The RFT method has the capability of speeding up transient stability limit derivation by reducing the number of stability runs.

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