Wavelet-based index to discriminate between minor inter-turn short-circuit and resistive asymmetrical faults in stator windings of doubly fed induction generators: a simulation study

This study investigates two common types of stator winding faults in doubly fed induction generators (DFIGs) including inter-turn short-circuit fault (ITSCF) and winding resistive asymmetrical fault (WRAF), and compares them with the operation of DFIGs underpower grid voltage unbalance conditions. A complete magnetic equivalent circuit model has been used to model ITSCF and WRAF in the stator windings of DFIG. The aim of this investigation is to discriminate between these types of faults using the rotor-reference-voltage signals inside the rotor-side-converter control system. A new fault diagnostic index (FDI) is proposed based on normalised energy evaluation of the given signal using the discrete wavelet transform. The accuracy of the proposed FDI has been evaluated by simulation of DFIG performances with Matlab/Simulink software under low number of stator shorted turns conditions, different severities of winding resistive asymmetrical faults, various levels of grid voltage unbalance, various rotor speeds, and various output active powers. Analysis of the simulation results confirms that the proposed FDI can accurately discriminate between ITSCF even with minor shorted turns, WRAF or unbalanced voltages except for the cases with minor asymmetry and healthy conditions of stator winding.