The combined use of the instantaneous fault frequency evolution and frequency sliding for advanced rotor fault diagnosis in DFIM under time-varying condition

The paper introduces a new monitoring and diagnostic technique for the detection of rotor electrical faults in Doubly Fed Induction Machine (DFIM) for wind power systems. Operating in aggressive environments, with plans onshore or offshore, the detection of anomalies at an incipient stage is a crucial step to decide about the operating continuity of the machines. Discrete Wavelet Transform (DWT) with High Multiresolution Analysis (HMRA) of stator currents is here proposed in order to detect rotor faults. The instantaneous fault frequency evolution (IFFE) and frequency sliding (FS) are proposed for improving the ability of DWT in extracting the contribution of each left side harmonic dynamically over time. Moreover the mean power at different resolution levels was introduced as a diagnostic index for fault quantification. Simulations and experimental results show the effectiveness of this new method in discriminating healthy from faulty rotor in time-varying operating condition.