Research On Parameter Optimization And Fault Analysis Of High Speed Permanent Magnet Generator

The centralized power supply system is the main power supply mode in the world.The failure of any position in this power supply mode is very easy to cause large-scale blackout.Therefore,as a representative of distributed energy supply system,high-speed permanent magnet generator(HSPMG)driven by micro gas turbine has been widely concerned.As a kind of portable emergency power generation equipment,HSPMG has become an important part of power supply flexibility and reliability,and widely used in military,medical,mine rescue and other fields.However,the rotor permanent magnet parameters will affect the electromagnetic performance and output performance of HSPMG,and the stator winding fault will affect the operation stability and power supply reliability of HSPMG.Therefore,this paper takes an 117 kW,60000rpm HSPMG with back rounded stator windings as an example,optimizes the parameters of rotor permanent magnet.On this basis,the inter-turn short-circuit fault and open-circuit fault of the back rounded stator windings are studied.For the special back rounded stator windings of HSPMG,a 2-D finite element electromagnetic field analysis model and its equivalent circuit under non fault condition are established.By using the field-circuit coupling method,the variation laws of harmonic content,voltage,voltage regulation rate and loss with the increase of permanent magnet thickness are obtained,the mechanism of nonlinear variation of harmonic content,voltage and loss are revealed,and the permanent magnet thickness with the best generator performance is obtained.In addition,in order to find out the key permanent magnet parameters that affect the generator output performance,the mechanism of nonlinear variation of output voltage with the change of load is revealed when the variation degree of remanence and coercivity is consistent by using the field-circuit coupling method.The sensitivities of no-load electromotive force,output voltage at rated power,voltage regulation,and overload capability to the variations of permanent magnet parameters are studied.Furthermore,the mechanism of permanent magnet parameters affecting generator output performance is revealed,and the basis for selecting permanent magnet parameters is given.In order to study the influence of the pulsating magnetic field produced by the loop current in the back rounded stator windings inter-turn short-circuit fault on the electromagnetic field and loss of HSPMG,an analysis model of the inter-turn short-circuit fault considering the loop current and its equivalent circuit are established.By using the field circuit coupling method,the mechanism of the magnetic field symmetry change is revealed when inter-turn short-circuit fault occurs.By comparing the spatial distribution of the air-gap flux density,the relationship among the spatial distribution of the air-gap flux density,the elliptical rotating magneto-motive force and the current phase angle is determined.The variation of the amplitude of the air-gap flux density space harmonic under different fault degree is studied,and the fault characteristics of inter-turn short-circuit fault are obtained,which provides a reference for inter-turn short-circuit fault diagnosis and fault degree identification.The distribution of the eddy current density is studied,and the fundamental reason for the sharp increase of eddy-current loss after fault is found.The core losses at different positions were obtained by segmenting stator core,and the variation mechanisms of core losses at different positions are revealed.The change of heat source distribution of stator core after fault is determined.The variation of winding copper loss after fault is analysed,and the influence degree of the loop circuit on the fault phase and healthy phase copper loss is determined.In order to study the influence of open-circuit fault on electromagnetic field of HSPMG,the open circuit fault analysis model and its equivalent circuit are established.By using the field-circuit coupling method,the magnetic field changes pre-and post-fault is analysed,and the mechanism of magnetic field spatial distribution changes post-fault is revealed.In addition,the changes in eddy current loss pre-and post-fault are analysed.The influence of the harmonic magnetic field and the rotating magnetic field produced by negative sequence current on eddy current loss is studied,and the dominant factors effecting eddy current loss post-fault are investigated.