Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Electrical and Computer Engineering


Dr. R.T.H. Alden


Dr. N.K. Sinha


This thesis presents a continuation in the process of rationalizing, unifying and improving existing model reduction techniques. Thus a method of reduction is developed which combines the method of aggregation and partial Pade approximation in such a way as to maintain their separate advantages while simultaneously removing their disadvantages. The important aspects associated with the reduced-order models obtained are: guaranteeing the stability of the reduced-order models saving computation time, retaining the invariance property under state variable feedback conditions and matching some of the original system time moments.

Also, a criterion is proposed for selecting the state variables of the original system to be retained in the reduced-order model. This criterion leads to developing a reduction technique which can be regarded as a combination of the methods of aggregation and singular perturbation. Therefore, the reduced-order model obtained retains the physical significance of the state variables and the dominant eigenvalues of the original system.

Furthermore, a procedure is developed for obtaining dynamic equivalents of multimachine systems. This procedure utilizes the concept of component cost analysis for identifying the coherent groups of generators.

Verification of the methods developed in the thesis is established using a variety of realistic power system models including a single synchronous machine connected to an infinite bus, a three-machine system and a 10-machine system. These applications include simulation, analysis and simple controller design.

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