Analysis and synthesis of a 2 MVA series-stacked power-quality conditioner

[摘要] ENGLISH SUMMARY: This thesis describes the development of a power electronic converter for a 2 MVA series-injectionpower-quality device. The converter is designed to interface directly with superconductingmagnetic 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 MVAconverter is investigated. A new resonant turn-off snubber topology is introduced and a detailedtheoretical study of the converter and snubber switching losses is carried out. An optimalsnubber design procedure is derived. This is followed by a theoretical investigation of theeffects of the different parasitic components on the snubber operation. In the final part of theinvestigation, a turn-on snubber is added to the turn-off snubber topology. An experimentalevaluation 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 inthe 2 MVA series-injection device, is investigated. A detailed theoretical analysis of the DC-busbalancing mechanisms is conducted. This theoretical analysis makes use of fundamental resultsfrom 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 ata 2.4 kV DC-bus voltage, is constructed. The operation of this converter is verified through arange of experiments and the measured results are compared with the theoretical predictions.

[发布机构] Stellenbosch University