M.Ing. / With the increased use of nonlinear loads such as variable speed motor drives and rectifiers, the voltages and currents on the power system grid are no longer sinusoidal. These non-sinusoidal waveforms cannot be analyzed by conventional power theories and the usual recourse is to decompose the nonlinear waveform into a set of harmonics. Harmonic voltage and current components are detrimental to the power system and may cause additional losses, or premature failure of equipment, and as such they have a definite influence on the quality of supply. This thesis shows the limitations and potential pitfalls of harmonic decomposition and other power theories, and examines various methods used for identifying, quantifying and modelling nonlinear loads. The aim of the thesis is to evaluate methods for attaching a specific disturbance or non-linearity on the voltage waveform to a specific load connected at the point of common coupling. The power theories examined include the total complex power, the IEEE working group definitions of apparent power, true power factor and harmonic adjusted power factor. Some new techniques for estimating the degree to which a load is disturbing the voltage at the point of common coupling is introduced, including the calculation of correlation indices, and the the use of wavelets.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:13376 |
| Date | 02 March 2015 |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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