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DEVELOPMENT OF HIGH FREQUENCY POWER CONVERSION TECHNOLOGIES FOR GRID INTERACTIVE PV SYSTEMSLi, Quan, q.li@cqu.edu.au January 2002 (has links)
This thesis examines the development of DC-DC converters that are suitable for Module Integrated Converters, (MICs), in grid interactive photovoltaic (PV) systems, and especially concentrates on the study of the half bridge dual converter, which was previously developed from the conventional half bridge converter. Both hard-switched and soft-switched half bridge dual converters are constructed,
which are rated at 88W each and transform a nominal 17.6Vdc input to an output in the range from 340V to 360Vdc. An initial prototype converter operated at 100kHz and is used as a base line device to establish the operational behaviours of the converter. The second hard-switched converter operated at 250kHz and included a coaxial matrix transformer that significantly reduced the power losses related to the transformer leakage inductance. The soft-switched converter operated at 1MHz and is capable of absorbing the parasitic elements into the resonant tank. Extensive theoretical analysis, simulation and experimental results are provided for each converter. All three converters
achieved conversion efficiencies around 90%. The progressive increases in the operation frequency, while maintaining the conversion efficiency, will translate into the reduced converter size and weight. Finally different operation modes for the
soft-switched converter are established and the techniques for predicting the occurrence of those modes are developed. The analysis of the effects of the transformer winding capacitance also shows that soft switching condition applies for both the primary side mosfets and the output rectifier diodes.
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HIGH FREQUENCY TRANSFORMER LINKED CONVERTERS FOR PHOTOVOLTAIC APPLICATIONSLI, QUAN, q.li@cqu.edu.au January 2006 (has links)
This thesis examines converter topologies suitable for Module Integrated Converters
(MICs) in grid interactive photovoltaic (PV) systems, and makes a contribution to
the development of the MIC topologies based on the two-inductor boost converter,
which has received less research interest than other well known converters.
The thesis provides a detailed analysis of the resonant two-inductor boost converter
in the MIC implementations with intermediate constant DC links. Under variable
frequency control, this converter is able to operate with a variable DC gain while
maintaining the resonant condition. A similar study is also provided for the resonant
two-inductor boost converter with the voltage clamp, which aims to increase the
output voltage range while reducing the switch voltage stress. An operating point
with minimized power loss can be also established under the fixed load condition.
Both the hard-switched and the soft-switched current fed two-inductor boost
converters are developed for the MIC implementations with unfolding stages. Nondissipative
snubbers and a resonant transition gate drive circuit are respectively
employed in the two converters to minimize the power loss.
The simulation study of a frequency-changer-based two-inductor boost converter is
also provided. This converter features a small non-polarised capacitor in a second
phase output to provide the power balance in single phase inverter applications.
Four magnetic integration solutions for the two-inductor boost converter have also
been presented and they are promising in reducing the converter size and power loss.
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