DC Wind Turbine Circuit with Series‐Resonant DC/DC Converter
Author
Zaja, Mario
Term
4. term
Education
Publication year
2015
Submitted on
2015-06-03
Pages
80
Abstract
Havvindmølleparker sender ofte strøm i land via højspændings-jævnstrøm (HVDC), hvor spændingskildeomformere (VSC) i begge ender omformer mellem vekselstrøm (AC) og jævnstrøm (DC). I dag samles effekten fra hver mølle som AC på mellemspænding, hvilket betyder, at hver mølle skal have en AC-DC-AC-omformer. Et lovende alternativ er at lade hver mølle levere DC på mellemspænding, som kan samles og transformeres op til HVDC på en platform til havs. I denne løsning erstattes møllens DC-AC-trin af en serieresonant DC-DC-omformer med en mellemfrekvent transformator til at hæve spændingen. Drift ved højere frekvens gør effektelektronikken mindre og lettere. Til gengæld er driftsområdet relativt snævert, og komponenterne udsættes for høje spændings- og strømbelastninger. Afhandlingen præsenterer en teoretisk analyse af kredsløbet, valg af nøglekomponenter, design af styringssystem samt validering gennem simuleringer og en nedskaleret hardwareopstilling.
Offshore wind farms often transmit power to shore via high-voltage direct current (HVDC) links, using voltage-source converters (VSCs) at both ends to convert between alternating current (AC) and direct current (DC). Today, each turbine’s output is collected as medium-voltage AC, so every turbine needs an AC-DC-AC converter. A promising alternative is to let each turbine deliver medium-voltage DC, which can then be collected and stepped up to HVDC on an offshore platform. In this approach, the turbine’s DC-AC stage is replaced by a series-resonant DC-DC converter with a medium-frequency transformer to raise the voltage. Operating at higher frequency makes the power conversion equipment smaller and lighter. However, the converter has a relatively narrow operating range, and its components experience high voltage and current stress. This thesis presents a theoretical analysis of the circuit, selection of key components, control system design, and validation through simulations and a scaled-down hardware setup.
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