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Sophie Draper

Research Postgraduate – Electrical Power Node

Research Postgraduate – Electrical Power Node in the Department of Engineering


Sophie is an Electrical-Mechanical Engineer and final year PhD Researcher in the Department of Engineering. Sophie's PhD investigates the design, optimisation and comparison generators for multi-MW wind turbines, exploring commercial and unconventional electrical machine and drive-train configurations. The PhD project is funded by the Engineering and Physical Sciences Research Council (EPSRC), UK Research Innovation (UKRI). 

Sophie has undertaken teaching responsibilities in the Department for the Electrical Teaching Lab, including as Senior Demonstrator, and has led the Wind Energy Lab Project for Sutton Trust, STEP and Supported Progression Engineering Summer Schools. Sophie is a member of the Durham Energy Centre for Doctoral Training (Energy CDT) organised by the DEI and participates in interdiscliplinary energy seminars & workshops and collaborative external energy projects & site visits. 

Sophie completed her MSc with distinction in New & Renewable Energy Engineering and has  interests and experience in energy and sustainability relevant areas, formerly working with a global Engineering consultancy as an MEP Engineer. Her passion for energy extends into her STEM outreach, including at the annual Celebrate Science event and the ECO2 Smart Schools initiative with charity OASES. Sophie is a member of the Women Engineering Society (WES) Durham admin team, supporting the planning and organisation of seminars and the annual symposium.

Sophie has been an active member of the Durham University community, contributing as a former member of the Department of Engineering Strategic Advisory Board, and to Postgraduate Wider Student Experience through volunteering in University College (Castle). As a self-taught artist, Sophie has been shortlisted on three occaisions for the Durham Student Art Prize, including for the 'Paradise' theme where her artwork will be displayed in the Palatine Centre from Spring 2024-25.

Presentations and Conferences
  • EAWE (European Academic Wind Energy) 15th PhD Seminar, Nantes 2019
  • Energy Centre for Doctoral Training Seminar 2020 & 2021
  • UKMS (UK Magnetics Society) 2020
  • Durham Castle Sunday Seminar Series, 2021
  • DSE (Durham Student Energy) Public Talk, 2021
  • WESC (Wind Energy Science Conference), Hannover, 2021
  • Power, Privilege and Possible Futures Conference, Durham, 2021
  • DEI Annual Research Symposium 2022: Earth, Wind & Fire (3-Minute Thesis Winner)
  • Durham Castle Special Seminar for International Women & Girls in Science Day, 2023
  • 9th Ustinov Annual Conference: Powering The Future: Global Innovative Approaches in Sustainable Energy and Environment, 2023 (Best Presentation Award Winner)
  • STEM For Britain, Engineering Category, 2024 (Finalist)
Research Project

As wind farms move further offshore to achieve increased capacity factors and energy generation, wind turbines have rocketed in size. The radial-flux permanent-magnet synchronous generator (PMSG) has emerged as a dominant generator for high power offshore wind turbines given features such as its high-power density, brushless rotor and option to operate without a gearbox. Therefore, the PMSG ticks many boxes when assessed as part of a qualitative review. However, research indicates  that there is a propensity for its costly fully-rated converter to fail, impacting down-time. Furthermore, price-volatility, ethical and environmental issues associated with the vast quantities of rare-earth (Neodymium-Iron-Boron) magnets are of significant concern. Therefore, the consideration of generators that have reduced rare-earth magnet content, via the use of ferrite magnets or electrical excitation, by unconventional methods is crucial. Especially given material supply bottlenecks and cost pressures on manufacturers and operators to deliver low-cost wind farms at far offshore in Europe, and in developing markets.

There are limited quantitative generator comparison studies specific to wind turbines. To allow for better-informed and time-efficient comparison of high-power wind turbine generators, an expansive design, optimisation and modelling platform has been developed. This approach objectively provides analytical insights and differences in electrical, magnetic and structural areas. It is also important for informing stakeholders, given that the vast majority of information about the design and operating parameters of commercial generators is restricted by the OEMs and operators.

Generator design is a complex multi-physics problem, so a number of crucial parameters influencing the designs are guided as part of a constrained multi-objective optimisation problem. This has been achieved using a form of multi-objective genetic algorithm (NSGA-II) which is based on Darwin’s Theory of Evolution. Magnetic Equivalent Circuit, Winding Factor Method and Electrical Equivalent Circuit approaches are taken to allow for computationally efficient modelling of many generators, allowing for identification of performance trends across a range of conditions, such as IEC wind class and power rating scaling. Therefore, exhaustive finite element analysis (FEA) software is not required, but is used to automatically construct and scrutinise solutions.

Unconventional generators researched include the flux-concentrating synchronous, brushless doubly-fed induction and multistage axial-flux electrical machines. 

Results confirm that generator mass and performance does not scale linearly with rated power. This ties into a major challenge in the design of wind turbine generators which surpass 15MW where magnetic steel saturation in the teeth can occur as it reaches its magnetic and current loading limits. Inequality constraint violations thus becomes far more prevalent, meaning more designs are infeasible, producing discontinuous pareto fronts.

Supervised by Prof. Christopher Crabtree, Dr. Mahmoud Shahbazi and Dr Nur Sarma. 

The research is funded by EPSRC, UKRI and also aims to address the lack of publicly available wind turbine generator and drive-train information, especially given commercial proprietary technologies. 

Research interests

  • Design and Optimisation of electrical machines
  • Electrical power conversion
  • Offshore wind turbines and farms