Incipient fault detection in Wind Turbine Induction Generators based on Low Frequency Current Injection

A method based on low frequency current injection is proposed for early detection of electrical and mechanical faults on a Wind Turbine Induction Generator driven by Indirect Field Oriented Control. Bearing, broken rotor bar and stator faults are detected by processing the effect of a low frequency stator current injection on the output signal of the speed regulator. If a ripple is found, the rotor time constant is estimated, and the symmetry of the stator voltages is evaluated. Based on the observed trend of the rotor time constant variation and the symmetry of the stator voltages, it is possible to identity which type of fault is occurring. This method is simple and effective, does not need other transducers than those already present on a standard system, does not affect normal operation, and features good precision and robustness.