Abstract
As electricity demand continues to rise and the transition away from fossil-fuel-based generation accelerates, renewable-energy sources such as photovoltaic panels and fuel cells are being increasingly integrated into modern energy networks. Because these sources inherently provide low output voltage, high step-up DC/DC converters are required to interface them with high-voltage DC buses used in renewable-energy systems, DC microgrids, and electrified transport platforms. In recent converter development, increasing emphasis has been placed on achieving high efficiency, high power density, reduced device stress, and improved practical implementation ability in isolated high-gain conversion stages. However, many existing isolated and non-isolated high step-up converters still rely on extreme duty cycles, large transformer turns ratio, or both, which results in increased semiconductor stress, higher losses, and reduced suitability for practical high-gain operation. This thesis addresses this limitation by proposing and validating a new family of isolated high-gain DC/DC converters: QBFB, CFFB, and CFQFB. The novelty of this work lies in the development of a unified converter family in which a boost-cell stage is integrated on the input side, a voltage-multiplier cell is incorporated on the output side, and an active snubber is employed to clamp switch-voltage spikes and recycle leakage-inductance energy. Through this architecture, very high voltage gain is achieved without extreme duty cycles or large transformer turns ratio, thereby advancing the state of the art toward more practical isolated high-step-up conversion. To validate the analytical findings, comprehensive theoretical, simulation, and experimental investigations were conducted. Closed-form analysis was developed for voltage gain, semiconductor stress, and key operating characteristics, and these results were verified using MATLAB/Simulink and hardware prototypes. Experimental tests were carried out over a range of input voltages, duty cycles, and switching frequencies, including laboratory evaluation at 22 V, 32 V, and 42 V, to characterise efficiency, waveform behaviour, soft-switching performance, and dynamic response.Thesis is embargoed until 31 July 2028.
| Date of Award | Jul 2026 |
|---|---|
| Original language | English |
| Awarding Institution |
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| Sponsors | Royal Embassy of Saudi Arabia Cultural Bureau in London |
| Supervisor | Ahmad Elkhateb (Supervisor) & Robert Best (Supervisor) |
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