Doctoral Degrees (Electrical and Electronic Engineering)

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Browsing Doctoral Degrees (Electrical and Electronic Engineering) by browse.metadata.advisor "Akagi, H."

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    Analysis and synthesis of a 2 MVA series-stacked power-quality conditioner
    (Stellenbosch : Stellenbosch University, 1999-12) Mouton, Hendrik Du Toit; Enslin, J. H. R.; Akagi, H.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical & Electronic Engineering.
    ENGLISH SUMMARY: This thesis describes the development of a power electronic converter for a 2 MVA series-injection power-quality device. The converter is designed to interface directly with superconducting magnetic energy storage devices and operates at a nominal DC-bus voltage of 2.4 kV. In the first part of the thesis the viability of soft-switching for application to the 2 MVA converter is investigated. A new resonant turn-off snubber topology is introduced and a detailed theoretical study of the converter and snubber switching losses is carried out. An optimal snubber design procedure is derived. This is followed by a theoretical investigation of the effects of the different parasitic components on the snubber operation. In the final part of the investigation, a turn-on snubber is added to the turn-off snubber topology. An experimental evaluation of both the turn-off and combined turn-on and turn-off snubbers is carried out. In order to obtain a DC-bus voltage of 2.4 kV, a series-stacked converter topology, for use in the 2 MVA series-injection device, is investigated. A detailed theoretical analysis of the DC-bus balancing mechanisms is conducted. This theoretical analysis makes use of fundamental results from the theory of systems of linear differential equations; in particular of Floquet theory. In the final part of the thesis an experimental 700 kVA series-stacked phase-arm, operating at a 2.4 kV DC-bus voltage, is constructed. The operation of this converter is verified through a range of experiments and the measured results are compared with the theoretical predictions.