The Research On Electromagnetic Field Of Stator Winding Turn-to-turn Short Circuit In DFIG

Doubly fed induction generator (DFIG) are mainly used in wind power system where its reliability is important requirement. In DFIG, stator internal turn-to-turn short-circuit is a common fault. Due to the existence of short-circuit current in the fault coils, even the slight turn-turn short circuit will increase time by time, until the serious failure occurred which cause damage to winding and shutdown generator outage. Analysis by Electro-Magnetic Field (EMF) modeling is very promising in detecting stator inter-turn faults in DFIG and analysis on the mechanism and characteristics of failure can provide a valuable theoretical basis for the diagnosis and prevention to fault in DFIG.In this paper, an in-depth investigation is conducted by electromagnetic performance of a DFIG with stator turn-to-turn short-circuit. The finite element method (FEM) is used to model EMF of DFIG under various stator turn-to-turn short-circuit. By the large-scale finite element analysis software ANSOFT, the magnetic field is calculated when the turn-turn short circuit fault occurred in the stator winding under different levels. Based on the EMF calculation results, we observed and analyzed the influence on the generator internal EMF under different levels of the stator turn-turn short circuit, and got the changing discipline of the EMF distribution and air-gap flux density waveform when the fault emerged and increased gradually. In the last step, the spectrum analysis of the air-gap flux density in DFIG under different level of fault is produced by related software application. And the fault characteristics, the variation discipline on harmonic components of the air-gap flux density has been summarized, when turn-to-turn short-circuit fault occur in stator winding of DFIGs. The approach presented in this paper will provide the protection basis for the DFIGs with stator inter-turn short circuit fault.