Harmonic order tracking analysis: A speed-sensorless method for condition monitoring of wound rotor induction generators in wind turbines

This paper introduces a speed-sensorless method for detecting rotor asymmetries in wound rotor induction machine (WRIM) working as generator in wind turbines. The method is based on time-frequency analysis of rotors currents and a new transformation, which make it suitable for every working condition of the machine: steady state, transient regime and non-stationary conditions. Besides, the results are shown in the same sort of plot regardless the working conditions, reducing the number of point to be stored and highlighting the presence or absence of faults in a simple and clear way. Simulation and experimental results show the validity of the method to detect rotor electrical faults in WRIM under any working condition.