Research On Stator Current Diagnosis Method For Planetary Gearbox Fault Of Wind Turbine

Planetary gearbox is an important component of wind turbine transmission system and one of the components with the highest fault rate.It is of great significance to study the fault diagnosis of planetary gearbox to the reliable and stable operation of wind turbine.At present,the vibration diagnosis method is widely used in the field of fault diagnosis,but at the same time,it also has some disadvantages such as inconvenient installation and easy to be affected by the environment.The stator current analysis method can obtain fault information by using the electrical signals of the generator,which can effectively reduce the detection and maintenance costs.It is especially suitable for fault monitoring and diagnosis of wind turbine with large quantity and bad operating environment.In this paper,the fault signal model of each gear component in planetary gearbox is established,and the formula of the influence of gear fault on stator current is deduced.The basic principle of Empirical Wavelet Transform is analyzed.The advantages of empirical wavelet transform in signal decomposition are verified by comparing empirical wavelet transform with Empirical Mode Decomposition.Secondly,according to the dynamic equation of asynchronous motor,the driving model of double motor in gear fault is established.Based on this model,the simulation models of planetary gearbox transmission system and doubly-fed wind turbine system are built in Matlab/Simscape and Matlab/Simulink environment respectively.The simulation data collected under normal and fault conditions are decomposed by EWT,then the effective components are reconstructed and the envelope spectrum is obtained to extract the simulated fault frequency components.Finally,the fault simulation test bench of wind turbine planetary gearbox is built.The generator stator current signal and the planetary gearbox vibration signal are collected under the normal and fault conditions of the planetary gear,respectively.The EWT algorithm and envelope spectrum analysis are used to process and compare the collected signals.The simulation and experimental results show that the local fault of the planetary gearbox will cause the change of the motor current.Combined with the signal processing method of EWT and envelope spectrum analysis,the fault characteristic frequency component of planetary gear can be effectively extracted from stator current.There are some excitation harmonic components with higher amplitude in stator current signal.These frequency components are related to the excitation size of frequency converter.Avoiding the overlap of harmonic component and fault characteristic band can improve the accuracy of fault identification and achieve better diagnosis effect.