Thesis

Wireless high power conversion system for hybrid wind turbines

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Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T18221
Person Identifier (Local)
  • 202153582
Qualification Level
Qualification Name
Department, School or Faculty
Abstract
  • The X-ROTOR offshore wind-turbine concept places two secondary generator units on the rotating primary structure, requiring their electrical output to cross the continuously rotating rotor-to-tower boundary before connection to the stationary powertrain. Conventional slip rings can provide this function but retain sliding contact wear, contamination, inspection and brush-replacement requirements. This thesis investigates a contactless alternative based on a rotary transformer (RT) integrated with a dual active bridge (DAB) converter. The electrical architecture of the X-ROTOR powertrain is first defined, including independent conversion of the two secondary generator outputs and their coordination through controlled DC interfaces. Inductive power transfer using an RT is selected for the rotating interface after comparison with conductive, capacitive and radiative alternatives. An integrated RT-DAB design method is then developed to relate winding voltage and current, core area, winding window, magnetic airgap, winding separation, fill factor, turns ratio, leakage and magnetising inductances, switching frequency and DAB phase shift. Five RT geometries are considered: the original radial structure, the application-driven NEW1 and NEW2 geometries, and two L-type alternatives. The design is evaluated at three distinct investigation levels. A reduced-scale RT-AB platform operates from a common 42 V DC source at 20 kHz with a nominal 1 mm assembled core-to-core airgap. The measured terminal voltages and fundamental power factor trends are reproduced by the prototype-matched model, although the simulated current magnitude remains lower than the measured value. An intermediate RT designed for 600 V RMS/100 kW at 2 kHz is used to compare two- and three dimensional electromagnetic representations. Their calculated output powers are 98.832 kW and 98.787 kW, while larger differences occur in local flux density and core loss. The analysis is subsequently extended to a three-phase MW-class linked field-circuit model. Controlled studies separate the effects of RT geometry, primary-to-secondary winding separation and fixed-window winding fill factor. Increasing winding separation reduces coupling, current and transferred power, whereas reducing fill factor decreases the effective copper area and increases the represented winding loss. Under the retained reference conditions, NEW2 produces 991.3189 kW of output power with represented winding and core losses of 1.7865 kW and 8.7362 kW, respectively. The combined RT loss components correspond to approximately 1.06% of the output power. For the investigated 1:1 and 1:2 winding arrangements, the simulated secondary-to-primary RMS voltage ratios are 0.981 and 1.959. The results support the RT-DAB as an electrical and electromagnetic solution for contactless power transfer across the X-ROTOR rotor-to-tower interface within the investigated conditions. The thesis contributes an application-specific RT-DAB architecture, the NEW1 and NEW2 rotary transformer geometries, and an integrated analytical, electromagnetic and linked field-circuit design and assessment method. Full-scale implementation requires further mechanical, thermal, insulation, environmental and lifetime qualification.
Advisor / supervisor
  • Anaya-Lara, Olimpo
  • Campos-Gaona, David
Resource Type
DOI

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file details PDF of thesis T18221 2026-10-27 Public Download