Improved Winding Design of a Doubly Fed Induction Generator (DFIG) Wind Turbine using Surrogate Optimisation Algorithm Zheng Tan School of Electrical and Electronic Engineering Newcastle University A thesis submitted for the degree of Doctor of Philosophy October, 2015 To my father, Yueting Tan and my mother, Hong Zheng Abstract Abstract The use of renewable sources of energy is becoming increasingly important role in electricity generation. Wind energy is the fastest growing renewable energy source and is making a significant contribution to meeting the energy demands while still reducing CO2 emissions. In designing generators for installation in wind turbines, characteristics of high efficiency and low cost are among the first to consider. As the number of installed wind turbines increases across the world, questions of turbine component failure and repair are also receiving much attention. This PhD starts with the investigation of modern wind turbine generator design with a focus on electrical generator and its operation. The finite element analysis of an off-the-shelf 55 kW doubly fed induction generator is used as a case study in order to investigate its design and improve the machine performance. The main work of this PhD is on a novel approach by surrogate-based analysis and the optimisation of winding design and rewinding design based upon the doubly fed induction generator for energy efficiency improvement. Surrogate models of the machine are constructed using Latin Hypercube sampling and the Kriging modelling. Having validated the surrogate models, the particle swarm optimisation algorithm is developed and applied to find the optimal solution. Assuming a winding failure occurs mid-life of the wind turbine, three optimisation plans have been studied for the repair and re-design of the stator and rotor winding separately and in combination. To validate the optimisation results, an improved testing standard is developed to test doubly fed induction generator. The original machine is then rewound following the optimised plan and tested to determine the difference in performance. By comparing the two machines, improved performance is achieved both in optimisation simulation and experiments. Finally an annual wind speed profile at a specific location (Albemarle site) is analysed to estimate wind power. The Weibull distribution of the wind speed data is combined with the turbine topologies for estimating the annual wind energy production. The annual power generation from the two machines is compared to validate the proposed technology. i Acknowledgements Acknowledgements First and foremost, I would like to thank my supervisors, Prof. Wenping Cao, Prof. Bashar Zahawi and Dr. Milutin Jovanovic, for their patience and confidence. Particular thanks go to my supervisor Dr. Nick Baker, who imparted a lot of knowledge and critical thinking in the field of electrical machine design. The work would not have been possible without technical support and research idea from Prof. Xueguan Song and Dr. Richard Martin. I would also like to thank Prof. Mingyao Ma, Dr. Bing Ji, Dr. Wenjun Chen, and Dr Min Zhang, who gave me much help and advice. I would like to acknowledge Dr. Chukwuma Junior Ifedi, Dr. Yasser Alamoudi, Haimeng Wu, Zheng Liu, Sana Ullah, and Roziah Aziz for the times we spent together trying to solve problems. Many friends and colleagues made my life in the UG-lab enjoyable and motivated, these friends, to name but a few are Tahani Al-Mhana, Abdrrahman Al-Frhan, Maede Besharati, Xu Deng, Congqi Yin, Chen Wang, Yamen Zbedi, Xiang Lu, Huaxia Zhan, Abdalbaset Mnider, Musbahu Muhammad, Weichi Zhang, Chenming Zhang, and Jiankai Ma. My special thanks goes to my girlfriend, Qian Liu for supporting and encouraging me all the time. Finally, I could never have completed a doctorate without the ongoing support of my parents, Yueting Tan and Hong Zheng, and most especially my mother who is the most understanding, supportive and loving person in my life. Words are not profound enough to express my love and respect to both of them; and they have encouraged me to become a responsible and strong person. ii Contents Contents CHAPTER 1 INTRODUCTION .................................................................................................................... - 1 - 1.1 BACKGROUND........................................................................................................................................ - 1 - 1.2 MOTIVATIONS AND OBJECTIVES ............................................................................................................ - 3 - 1.3 METHODOLOGY ..................................................................................................................................... - 4 - 1.4 THESIS OVERVIEW ................................................................................................................................. - 4 - 1.5 CONTRIBUTION TO KNOWLEDGE ........................................................................................................... - 5 - 1.6 PUBLISHED WORK ................................................................................................................................. - 5 - CHAPTER 2 LITERATURE REVIEW ........................................................................................................ - 7 - 2.1 WIND ENERGY ....................................................................................................................................... - 8 - 2.2 WIND TURBINES PAST AND PRESENT ..................................................................................................... - 9 - 2.3 OVERVIEW AND TOPOLOGIES OF WIND TURBINES ............................................................................... - 10 - 2.3.1 Rotor Axis Orientation .............................................................................................................. - 10 - 2.3.2 Rotor Power Control ................................................................................................................ - 11 - 2.3.3 Rotor Position ........................................................................................................................... - 12 - 2.3.4 Yaw Control .............................................................................................................................. - 13 - 2.3.5 Rotor Speed .............................................................................................................................. - 13 - 2.3.6 Number of Blades ..................................................................................................................... - 14 - 2.3.7 Generator Speed ....................................................................................................................... - 14 - 2.4 MODERN WIND TURBINE DESIGN ........................................................................................................ - 14 - 2.4.1 Rotor ......................................................................................................................................... - 15 - 2.4.2 Drive Train ............................................................................................................................... - 15 - 2.4.3 Nacelle ...................................................................................................................................... - 16 - 2.4.4 Yaw System ............................................................................................................................... - 17 - 2.4.5 Tower ........................................................................................................................................ - 17 - 2.5 SURVEY OF GENERATOR TYPES FOR WIND ENERGY ............................................................................ - 18 - 2.5.1 Direct Current Generator ......................................................................................................... - 18 - 2.5.2 Permanent Magnet Generator .................................................................................................. - 19 - 2.5.3 Switched Reluctance Generator ............................................................................................... - 21 - 2.5.4 Induction Generator ................................................................................................................. - 21 - 2.5.5 Manufactured Wind turbines .................................................................................................... - 27 - 2.6 MACHINE FAILURE TYPES ................................................................................................................... - 29 - 2.7 SUMMARY ............................................................................................................................................ - 31 - CHAPTER 3 DOUBLY FED INDUCTION GENERATOR ANALYSIS ................................................ - 32 - 3.1 BACKGROUND...................................................................................................................................... - 33 - 3.2 MECHANICAL ASPECTS OF INDUCTION MACHINE ................................................................................ - 33 - 3.2.1 Stator Lamination ..................................................................................................................... - 34 - 3.2.2 Rotor Lamination .....................................................................................................................