Influence of DFIG rotor fault severity on stator current and power spectral content

Condition monitoring of doubly-fed induction generators (DFIGs) is growing in importance for modem wind turbines. This paper investigates the potential of the DFIG stator current and total instantaneous power signals to be used for condition monitoring of rotor faults, such as brush-gear faults or electrical unbalance, of differing severity. A purpose built DFIG laboratory test rig is used for experimental research and a number of fault-induced changes are identified in the measured steady-state stator current and power signal spectra. An experimental study of fault severity influence on determined fault spectral indicators was performed to examine the relationship between fault levels and magnitude of fault-induced frequencies. The results demonstrate a clear link between fault severity and fault frequency magnitude and suggest that different levels of fault could be distinguished and identified based on monitoring the fault frequency magnitude.