Thesis

Optimisation of generators for direct drive offshore wind turbines

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Awarding institution
  • University of Strathclyde
Date of award
  • 2024
Thesis identifier
  • T17053
Person Identifier (Local)
  • 201453310
Person Identifier (ORCID)
Qualification Level
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Department, School or Faculty
Abstract
  • A large proportion of offshore wind turbine designs are now based on directly driven permanent magnet synchronous generators using rare earth materials. The objective of this study is to optimise permanent magnet synchronous generators for offshore direct drive wind turbines in order to reduce the cost of energy, reduce the use of rare earth materials and increase the machine efficiency. A 6MW wind turbine design is assumed and parametric electromagnetic and structural generator models are introduced for a surface-mounted magnet generator topology (using magnets with high BHmax) and a flux-concentrating variant (using magnets with both higher and lower BHmax). Finite element method models are used to check key dependent variables calculated by the analytical models. These are optimised using a hybrid Genetic Algorithm and Pattern Search process with four different objective functions. -- Further steps to improve the quality of the model include the effect of generator mass on the design, cost of the turbine tower and foundation and the impact of generator diameter limits have on the choice of optimum independent variables. Further optimizations are carried out for different power ratings (6 MW, 8 MW and 10 MW), choice of magnet grades, BHmax and working temperature. The effect of variable power factor and sensitivity to magnet specific cost, availability, operation and maintenance cost, wind conditions and rest of the turbine cost are also investigated in this study. -- A detailed thermal model is used to estimate the effect of temperature due to power losses, calculate the cooling airflow requirements to bring the magnet operating temperature from 120°C to 80°C and controlling the cooling air flow for variable losses. Allowing the use of cheaper temperature grades of magnets, the additional cooling reduces winding losses and improves the effective BHmax of the magnets. -- Discussions and conclusions highlights the impact of different investigations on the optimal generator design and find out the possible best way to optimise the generator for offshore wind energy application.
Advisor / supervisor
  • Anaya-Lara, Olimpo
  • McDonald, Alasdair
Resource Type
DOI
Date Created
  • 2019

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