To achieve higher power density, converters and components must be able to handle higher voltage and current ratings at higher percentages of efficiency while also maintaining low cost and a compact footprint. To meet such demands, medium-voltage resonant converters have been favored by researchers for their ability to operate at higher switching frequencies. High frequency (HF) operation enables soft switching which, when achieved, reduces switching losses via either zero voltage switching (ZVS) or zero current switching (ZCS) depending on the converter topology. In addition to lower switching losses, the converter operates with low harmonic waveforms which produce less EMI compared to their hard switching counterparts. Finally, these resonant converters can be more compact because higher switching frequencies imply decreased volume of passive components. The passive component which benefits the most from this increased switching frequency is the transformer. The objective of this work is to design a >400 kHz, 100 kW transformer which will provide galvanic isolation in a Solid-State Transformer (SST) based PEBBs while maintaining high efficiency, high power density, and reduced size. This work aims to present a simplified design process for high frequency transformers, highlighting the trade-offs between co-dependent resonant converter and transformer parameters and how to balance them during the design process. This work will also demonstrate a novel high frequency transformer insulation design to achieve a partial discharge inception voltage (PDIV) of >10 kV. / Master of Science / As the world's population expands and countries progress, the demand for electricity that is high-powered, highly efficient, and dependable has increased exponentially. Further, it is integral to the longevity of global life that this development occurs in a fashion that mitigates environmental consequences. The power and technology sectors have been challenged to address the state of global environmental affairs, specifically regarding climate change, carbon dioxide emissions, and resource depletion. To move away from carbon emitting, non-renewable energy sources and processes, renewable energy sources and electric power systems must be integrated into the power grid. However, the challenge lies in the fact that there is not an easy way to interface between these renewable sources and the existing power grid. Such challenges have undermined the widespread adoption of renewable energy systems that are needed to address environmental issues in a timely manner. Recent developments in power electronics have enabled the practical application of the solid-state transformer (SST). The SST aims to replace the current, widespread form of power transformation: the line frequency transformer (50/60 Hz). This transformer is bulky, expensive, and requires a significant amount of additional circuitry to interface with renewable energy sources and electric power systems. The SST overcomes these drawbacks through high frequency operation (>200 kHz) which enables higher power at a reduced size by capitalizing on the indirect proportionality between the two parameters. The realization of the SST and its implementation has the ability to greatly advance the electrification of the transportation industry which is a top contributor to carbon emissions. This work aims to demonstrate a >400 kHz, 100 kW SST with a novel magnetic design and insulation structure suited for electric ship applications.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/115877 |
| Date | 27 July 2023 |
| Creators | Sharfeldden, Sharifa |
| Contributors | Electrical Engineering, Dimarino, Christina Marie, Cvetkovic, Igor, Boroyevich, Dushan |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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