Date of Award

1989

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Electrical and Computer Engineering

First Advisor

Gill G. Richards

Abstract

Harmonic voltages and currents are created by nonlinear loads in power systems. These harmonics can cause serious problems to the energy suppliers (utility companies) and energy users (consumers). This dissertation presents new techniques for harmonic measurement and the accompanying problem, harmonic reduction. To reduce harmonics, the location and magnitude of harmonic sources must be known a priori. However, to measure and monitor harmonic sources requires specialized instrumentation that is not generally permanently installed at most buses. In this study, a method is developed to use neural networks in conjunction with state estimation for monitoring and estimating harmonic sources with only a few permanent instruments. The method can also identify and monitor a "suspected" harmonic source that has not previously been measured. Once harmonic sources are known, the objective from an energy supplier's point of view is to minimize the combined total harmonic distortion of all buses on a distribution system. A procedure is developed for designing optimum filters on distribution feeders that have distributed and balanced or unbalanced harmonic sources and variable compensating capacitors. The design includes finding optimum filter admittances and the corresponding locations. Symmetrical components are used for the unbalanced harmonic source case. Filter realization with the lowest cost including sensitivity analysis is also discussed. The optimum filters chosen and placed in this manner may produce results superior to the conventional filter design procedures. The problem of harmonic reduction is alternatively approached as an energy user's problem. The user's objective is to eliminate his voltage harmonic distortion problem locally without considering the effects of voltage distortion at neighboring buses. The remedy is insertion of a reactor in series with the local compensating capacitor. A method is presented for finding the optimum fixed LC combination to minimize voltage harmonic distortion at a load bus while holding the displacement factor (fundamental power factor) at a desired value and constraining the total cost of the compensating equipment. Source harmonics and impedances are represented as randomly time-varying quantities.

Pages

113

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