| The development of a comprehensive approach to the modeling of electric power transmission systems at harmonic frequencies is presented. For harmonic analysis it is not practically possible to model a large transmission system with its neighboring interconnected systems in detail due to computer time and memory limitations. A large number of components of a large system also makes switching studies a recognized problem with respect to the desired accuracy, and required engineering and computer time. Current methods depend on the trial and error approach or the individual analyst's knowledge of the system, which are imprecise and expensive to develop at harmonic frequencies.; The approach to solve this problem involves the development of a formal method for dividing large-scale transmission systems into a main study system and a group of external systems. Then, using an efficient and appropriate method of adjoint network sensitivity analysis, the size of the system model is reduced, keeping the same frequency characteristics as that of the original system. This reduction in model size in turn accommodates larger transmission system size and increases the accuracy and computational efficiency. An efficient and accurate method is also presented that determines the relative importance of external system equivalents on the harmonic impedance of a transmission network. The bilinear theorem provides an economical method of determining the appropriate locations for simplification of external systems. Using this technique, the system model error bounds can be fixed and the high error range of the external system equivalent impedance can be reduced.; For filter designs, the most important issue of computing harmonic impedance boundaries is improved by using an efficient adjoint network sensitivity analysis. Using this sensitivity analysis an order of critical components is developed. The number of outage contingencies to be analyzed is reduced by a large factor which considerably reduces the engineering time and increases dependability.; Two transmission systems have been studied to demonstrate the proposed methods. This work will provide transmission system planners and designers an efficient and economical tool of known accuracy for the analysis of harmonic propagation, switching studies and design of harmonic filters. |
