M.Ing. (Electrical Engineering) / This thesis primarily addresses the subject of analysis and compensation of fictitious power instantaneously: Fictitious power is defined as that component of apparent power which does not contribute to the nett transfer of energy from source to load. The dynamic characteristics of contemporary electric loads are of such orders of magnitude that the load current contains severe changes 'within a fundamental frequency cycle. Furthermore, such changes might not be periodic but may only appear for short durations. Likewise, load current unbalance may also reach intolerable levels, only for relatively short durations of time. Power theories based on the classic active current approach has the characteristic that calculated magnitudes are only available after some time has elapsed, which usually is a fundamental frequency period. The original instantaneous power theory calculates active and fictitious current magnitudes instantaneously, but these obtained values do not relate to the classic values. Classic static VAr compensator dynamic operation limits lie at switching twice per fundamental frequency cycle, with the result that intra-eycle changes in the load current cannot be compensated. Distortion compensators' comprise an energy storage element and a high frequency converter with dynamic characteristics to compensate instantaneously for fictitious power components. The revised instantaneous power theory is proposed in this thesis and is a combination of the classic active current theory and the original instantaneous power theory. The revised instantaneous power theory generates the fictitious currents instantanenously. A distortion compensator is combined in parallel with the classic static VAr compensator to obtain the hybrid fictitious power compensator. This compensator has dynamic characteristics to match the revised instantaneous power theory and to compensate for high dynamic load current variations within one fundamental cycle. The revised instantaneous power theory is implemented as primary control of a hybrid fictitious power compensator. The error modulation automatic control technique for the distortion compensator is proposed and implemented with improved results in distortion current compensation and current-fed distortion compensator stability. The secondary control of the hybrid fictitious power compensator concerns the feedback of the generated hybrid fictitious power compensator currents. The control of the hybrid fictitious power compensator is done with a personal computer in parallel with analog circuitry. The computer has an on-board dedicated data acquisition and output card. The hybrid fictitious power compensator is demonstrated on two experimental loads and the revised instantaneous power theory is demonstrated on three experimental loads.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:4303 |
| Date | 12 March 2014 |
| Creators | Marshall, Dirk Adriaan |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
| Rights | University of Johannesburg |
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