Research On Axial Flux Permanent Magnet Generator For Vertical Axis Wind Power Generation

Developing clean and renewable energy is an important strategy for China to adjust the energy structure and alleviate the contradiction between energy and the environment.Low speed direct drive permanent magnet wind power generation is one of the most important fields of commercialization and industrialization in all kinds of renewable energy,which can provide a distributed power for the pastoral area,fishing boat,town,road and so on.Axial flux permanent magnet generator is flat,compact and high power density,especially the air-cored stator structure,which can effectively eliminate cogging torque and stator iron loss,and it is high efficiency and low starting torque.The outer rotor of the generator can be directly fixed with the fan,which reduces the transmission structure,and it is convenient for installation and maintenance,especially for low wind speed and direct drive vertical axis wind power generation.The main magnetic field of axial flux permanent magnet generator is a three dimensional structure.The most accurate design and analysis method is three-dimensional finite element method.However,it is complex,time-consuming and the calculation of electromagnetic performance is difficult.Besides,the optimization design of coreless axial flux permanent magnet generator is a complex,nonlinear,multi-objective,multivariable and multi peak value problem,and different variables may have contradictions for the same optimization goal.In this paper,the main parameters of the axial flux permanent magnet generator are preliminarily determined on the basis of the electromagnetic calculation of the cylindrical generator.The Taguchi and Response Surface Method are applied to multi-objective optimization of the initial parameters of the coreless axial flux permanent magnet generator,and the effectiveness of multi-objective optimization is verified by the finite element method.In this paper,the complex three-dimensional model of the stepped magnetic steel is simplified as a two-dimensional model.A layered model is used to superimpose the magnetic field.The air gap magnetic field,induction electromotive force,electromagnetic torque and efficiency are calculated and the effectiveness of the analytical method is verified by the finite element method.Combined with the structural characteristics of axial flux permanent magnet generator,according to the principle of heat transfer,the loss and heat source density of each part of generator are calculated,and the three-dimensional finite element model of electromagnetic field and temperature field of generator is established.Through the simulation analysis,the temperature rise of each part of the generator is obtained when the generator runs in a stable state with rated load.The results show that the temperature rise of the generator designed in this paper can meet the needs of the actual engineering.Finally,an external rotor axial flux permanent magnet generator with coreless is made,and an experimental platform is set up.The experiments of no-load and load are carried out on the prototype respectively.The results show that the total harmonic distortion(THD)of output voltage is low,the efficiency is high,and the output of the prototype is stable,which meets the design performance index.