The Research On Fault Diagnosis Of The Stator Inter-turn Short Circuit In Doubly Fed Induction Generators

As a new clean energy, wind energy has attracted much attention in the context of the current resources crisis, and doubly-fed induction generators(DFIG)are the mainstream models in the wind power market. The bad work environment of DFIG can lead to failure which will endanger the safety of power grid, especially the stator or rotor fault which accounts for about 38% of the total failure. Therefore, the motor stator fault study has practical significance to guarantee the safe and stable operation of generators and the whole system.This paper established the mathematical model of DFIG based on the multi-loop theory. And the mathematical model is established by MATLAB software programming to simulate different motor running state, such as generator normal, stator inter-turn short circuit fault, rotor speed change, stator voltage imbalance and so on.In this paper, the motor electromagnetic characteristic was analyzed when stator inter-turn short circuit fault occurs, then the stator inter-turn short circuit current harmonic content was obtained. Meanwhile, the stator current harmonic was analyzed when stator voltage imbalance occurs, and the two harmonic contents were compared.As a traditional time-frequency analysis method, the wavelet transform method does not have obvious advantages in the inter-turn short circuit fault diagnosis. But hilbert-huang transform(HHT) has more obvious effect than wavelet method in the fault diagnosis of the generator. EEMD method is the improvement of the EMD method in HHT. The stator inter-turn short circuit fault was "identified" by using the method in this paper, and some interference factors in the process of diagnosis can be excluded.Rotor speed change experiment and stator voltage imbalance experiment were completed by using the double-fed induction generator in the new energy laboratory, and the experimental results were respectively analyzed by using the EMD and EEMD method. The analysis results are in conformity with the analysis of the simulation results.