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Design and Optimization of a Flux Reversal Permanent Magnet Generator for Power Density Improvement in Direct Drive wind Turbine Application

Ghasemian, Majid | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52786 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Tahami, Farzad; Nasiri Gheidari, Zahra
  7. Abstract:
  8. Nowadays, due to gearbox drawbacks, the direct-drive wind turbines have received much more attention. Permanent magnet synchronous machines are commonly used for this purpose. The flux reversal machine with a magnetic gearbox and high power density could be an appropriate alternative. Due to placement of permanent magnets on the stator, the machine has a simple and robust structure and provides more reliability. There is limited study on optimization of the flux reversal machine and the existing papers are not complete and many parameters like PM dimension, working temperature, and winding reactance are not considered in the optimization process.Considering the flux reversal machine advantages, in this thesis, a 1,5 MW direct-drive wind turbine generator is designed and optimized with the aim of increasing power density. For this purpose, the equivalent circuit and thermal model of the flux reversal machine are obtained and used in the optimization process. The extracted models are validated with the finite element method and experimental results. The distributed winding is introduced in replace of the conventional concentrated winding of the flux reversal machines and its advantages are investigated. A design procedure is presented for FR generators and an objective function is introduced for design optimization. The optimization is aimed to minimize power density, active materials cost and rare earth permanent magnet mass, with a maximum operating temperature and minimum winding reactance as restrictions. During optimization, the winding reactance is calculated as an important parameter. As the increase of the machine reactance leads to a higher required DC bus voltage for the connected converter and consequently higher cost, the total cost of the generator and the convertor is considered for the optimization. The optimum flux reversal generator is compared with a convention permanent magnet generator with the same performance. The results show that the flux reversal generator can improve the power density and reduce the total cost of the machine and converter while provides more robust structure. Finally, the optimized generator is evaluated by the finite element method
  9. Keywords:
  10. Wind Turbine ; Permanent Magnet Generator ; Power Density ; Optimization ; Reactance ; Temperature ; Permanent Magnet Synchronous Machine ; Flux Reversal Generator ; Distributed Winding

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