Rotor fault diagnosis of wound rotor induction machine for wind energy conversion system under time-varying conditions based on optimized wavelet transform analysis

The aim of this paper is to present a new diagnosis technique for the detection of rotor electrical faults in three-phase wound rotor induction machines (WRIMs). In this application the rotor windings are supplied by a static converter for the control of active and reactive power flows from the generator to the electrical grid. The proposed diagnosis technique is based on the combined use of wavelet analysis and a preprocessing of the analyzed rotor voltages under time-varying conditions. Thus, the time evolution of the fault components can be effectively analyzed. A diagnostic index, periodically calculated, is introduced to estimate the rotor fault degree over time. Experimental results show the validity of the proposed technique, leading to an effective diagnosis procedure for rotor electrical faults in WRIMs.