Analysis And Diagnosis Of Static Eccentricity Fault Of Large Permanent Magnet Wind Turbine Generator

At present,wind power technology developed rapidly.Because of the direct-drive permanent magnet synchronous wind turbine unit has a unique advantage,the capacity in the wind farm installed gradually increased.As the core components of the unit,permanent magnet wind turbine's operating performance affect the wind turbine,wind farm and even the safe and stable operation of the power grid.It is helpful to study the performance of permanent magnet wind turbine under fault,and it will provide the reference for the fault diagnosis of permanent magnet wind turbine and ensure the stable operation of wind power system and even promote the development of wind power industry.The operating conditions of the generator is relatively harsh,prone to a series of failures.According to the fault location,it can be divided into stator failure,rotor failure,air gap eccentric fault and bearing failure.Among them,the air gap eccentric fault is more common,accounting for more than 10% of generator failure.Therefore,it is very important to study the eccentric fault of large permanent magnet wind generator and the early diagnosis of this fault.Based on the analysis of the structure of the permanent magnet generator,the internal magnetic field distribution and the related theory,the mathematical model of the permanent magnet generator under the eccentric fault condition is constructed.The analytical method is used to analyze the air gap magnetic density and unbalanced magnetic tension.And the analytic formula of the air gap flux,unbalanced magnetic tension,induced potential and loss of the permanent magnet generator in the event of eccentricity fault is obtained.Based on the finite element theory,two-dimensional eccentric model of permanent magnet wind turbine was established by Ansoft Maxwell software.The influence of stator,rotor and power generation quality of wind turbine under eccentric fault is analyzed by parametric simulation.The variation law of air gap flux,magnetic tension,induced potential and loss of generator under different eccentricity degree is obtained.Based on the eccentric fault characteristics,the main fault diagnosis method of generator fault and its own characteristics,this paper chooses to use the fault characterization characteristic to design the early fault diagnosis scheme.Based on the analysis of the stator current signal under the eccentric fault and the MATLAB toolbox,the stator current under different eccentricity is decomposed by fast Fourier decomposition,and the eccentric fault diagnosis is obtained by comparing the amplitude of the power spectrum.To achieve the classification of eccentric fault and the degree of eccentricity to determine the completion of large-scale permanent magnet wind turbine static eccentric fault early diagnosis to ensure the stable operation of wind turbine.