Electromagnetic Design And Rotor Structure Analysis Of 10MW Brushless Doubly Fed Generator For Offshore Wind Turbine

In recent years,offshore wind power generation with large scale and high reliability has been becoming the development trend of wind power generation in the world,and the MW class wind power generators,even more than 10 MW,have been the focus of research and development in the countries which have the best wind power technologies in the world.Because of the special operation environment in the sea,the higher requirement of wind power generators has been put forward,such as reliability,economy and so on,compared with the common wind power generators: brush doubly fed generators and permanent magnet synchronous generators,Brushless Doubly Fed Generators(BDFG)have many outstanding advantages,such as brushless,higher reliability,smaller capacity of the required converter,low cost and others,therefore,BDFG has a more broad prospect in the offshore wind power generation.In this paper,a 10 MW BDFG for offshore wind turbine is seen as the research object,its electromagnetic design,rotor design,characteristic simulation,and stress analysis of rotor are researched.The main contents of this paper are listed as follows:Firstly,the structure of stator and rotor,and operation principle are introduced.For the special design requirements of BDFG,the electromagnetic design of a 10 MW BDFG for offshore wind turbine is researched,the pole number,stator slot number,air-gap width,inner and outer diameter,stator slot size and winding distribution and other diameters are determined.And the rated design principles are provided.Secondly,for the coupling capacity of magnetic barrier rotor,through analyzing the useful harmonic content,the pole-arc coefficient of magnetic barrier rotor is determined.The mutual inductance between power and control winding and the ratio of useful harmonic and basic harmonic are seen as optimization goal,the Taguchi method is used to analyze the effect of salient pole height,magnetic layer numbers,and the ratio of magnetic layer and non-magnetic layer on coupling capacity of magnetic barrier rotor in depth,the importance of different structure parameters on the coupling capacity of magnetic barrier rotor is determined.The structure parameters of magnetic barrier rotor with strong coupling capacity are obtained,and its coupling capacity is verified through finite element method.Then,in order to verify the feasibility of the designed generator,2-D electromagnetic field simulation model of a 10 MW BDFG for offshore wind turbine is established through finite element analysis software,its no-load characteristic,electromagnetic field distribution,air gap flux,no-load EMF of no-load operation and electromagnetic field distribution,terminal voltage,load current,copper loss,core loss,and efficiency of load operation are simulated and analyzed,the related results are obtained,and the feasibility of the designed generator are verified.Finally,in order to make the weight of rotor as small as possible,and meet the requirements of its strength,the idle state and rated operation condition of three rotors with different rotor brackets are analyzed through finite element analysis,the related analysis cloud maps of stress and deformation are obtained,a rotor structure is selected through comparing the simulation results.The super-synchronous and sub-synchronous operation conditions of the selected rotor are also analyzed,and the reliability is verified.