Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Electrical and Computer Engineering


This dissertation attempts to apply the transient energy function (TEF) method of direct stability analysis to stressed large-scale power systems;In a stressed system, the post-disturbance network is often characterized by the weak synchronizing forces caused by large transmission impedances. When the instability occurs following a disturbance, a large group of generators may separate from the system. This is known as the inter-area mode of system separation. The analysis of stressed systems by the TEF method requires overcoming a number of analytical and numerical issues. The major issues identified and dealt with are the following: (i) identifying the group of machines which are most seriously affected in the post-disturbance system, known as the mode of disturbance (MOD) determination and (ii) obtaining and verifying the unstable equilibrium point (UEP) solution;The determination of MOD involves the inspection of several candidate modes of disturbance provided by the analyst. The MOD has to be determined in order to identify the UEP relevant to the disturbance under investigation, and to calculate the portion of kinetic energy responsible for system separation. In large systems where the inter-area mode is encountered, the selection of candidate modes can be very complex. A scheme to automatically generate the right MOD has been developed and implemented;The critical energy calculation involves the major step of accurately solving for the relevant UEP. The stressed systems cause a severe numerical ill-conditioning to be dealt with. A robust technique, the Corrected Gauss-Newton (CGN) method in nonlinear least-squares minimization has been implemented. A scheme has also been developed to verify the UEP solution for inter-area mode cases;The new developments were tested on realistic power networks of the Ontario Hydro system. The operating conditions selected for the studies represent highly stressed power systems. The results of the tests compared well with those obtained by time-solution in (i) predicting the correct dynamic behavior (e.g., inter-area mode swing) and (ii) obtaining a reasonably accurate transient stability assessment (e.g., power limit).



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Sankaran Rajagopal



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123 pages