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UBC Theses and Dissertations

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UBC Theses and Dissertations

Estimation of dynamic equivalents of external electric power systems Sharkawi, Mohamed Ali Ahmed Ali El


The growing size and complexity of modern electric power systems necessitate the need to develop dynamic equivalents of the external system for local system dynamic studies. An estimation technique is developed in this thesis to identify the dynamic equivalents of external systems. An introduction is given in Chapter 1. A Basic multi-machine model for dynamic studies is developed in Chapter 2. The dynamic equivalent is estimated from information measured locally due to an intentional disturbance. To reduce computational requirements, a weighted least-squares algorithm with adaptive step size scheme is used, and a proper model for the external equivalent is chosen in Chapter 3. Applying the developed techniques, equivalent parameters are estimated for three test systems, and the results are included in Chapter 4. In Chapter 5, the dynamic equivalents are first verified by comparing the dynamic interacting effect of the external system on the study system for both original and equivalent systems. The equivalents are further verified by three-phase short-circuits on machine buses of the study system. The dynamic responses of the original systems and the equivalent systems are compared. Conclusions are drawn in Chapter 6 that the dynamic equivalent derived by the technique developed in this thesis is unique that the estimated equivalent is a good representation of the original external system, and that it can be developed for on-line identification.

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