Design And Analysis Of Brushless Doubly-Fed Machine With Segmented Squirrel-Cage Rotor For Wind Power Conversion

Developed the economy at the expense of the environment in the past,the energy industry of China will take a low-carbon and green road.Compared with the other new energy conversion,wind power generation is one of the most mature technologies.At present,there are four kinds of generators in wind power conversion area,namely Caged Induction Machine(CIM),Permanent Magnet Synchronous Machine(PMSM),Doubly-Fed Induction Machine(DFIM)and Brushless Doubly-Fed Machine(BDFM).In recent years,BDFM has become a research hotspot due to its more stable and reliable structure without brushless.Furthermore,the wind power system with BDFM is more economical than any other power generation systems.BDFMs realize the energy transfer between two sets of winding on stator by the magnetic field modulation function of the rotor.Therefore,the magnetic field modulation ability of the rotor directly affects the efficiency and power density of the kind of machines.The existing BDFMs usually possess the disadvanteges such as poor rotor modulation ability and low end space utilization,which leads to the low power density of the machine.Focusing on the above mentioned problems,this thesis proposes a novel BDFM with Segmented Squirrel-Cage Rotor(SSC-BDFM),based on which the rotor structure,the operating modes,the structure parameter design,and the performance analysis are investigated and analyzed.The main contents of this article are as follows:1.Firstly,the prospect of wind power generation,the classification of wind powergenerator,and the main wind power generators in industry are overviewed.Then,the application prospect and disadvantages of BDFMs in the present stage are discussed,based on which a novel SSC-BDFM is proposed.2.Secondly,the structure,the polar number selection and the winding type of stator windings of SSC-BDFM are introduced.Based on the wind power generation application and the characteriscs of existing types BDFMs,the typical operating modes of this kind of machine are described in detail.3.Thirdly,the design method and process of SSC-BDFM are described in detail. The initial parameters of the machine are determined according to the basic demands at the first step.Then the dimension parameters of stator core,rotor bars spacing angle and rotor bars couples are optimally designed so as to achieve a high rotor coupling ability combining with the aim of high efficiency.4.Modelling of SSC-BDFM using finite element software,the electromagneticperformances,such as magnetic field distribution,flux linkage,and no-load EMF are calculated and analyzed.The comparison of modulation capabilities among the cage rotors with different connections verifies that the proposed rotor structure guarantees a high coupling capability while the end space utilization is higher.5.Finally,the losses of proposed SSC-BDFM under different working conditions are calculated and analyzed,so that the output power and efficiency of SSC-BDFM at different speeds are obtained.