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Wound rotor induction machine (WRIM) has been extensively used in different applications such as medium-power wind turbines and traction systems. Since these machines work under harsh and difficult conditions, condition monitoring of such systems is crucial. Different electrical and mechanical signatures of machines were used for electrical and mechanical fault detection in electrical machines such as vibration, acoustic emission, stray flux, and stator current signature. In recent years, stator current signature analysis due to simplicity, cost-effectiveness, and availability has been considered for fault detection process in comparison with previous conventional methods such as acoustic and vibration. In this paper, a high-resolution technique based on the chirp-Z transform is used for rotor asymmetry fault (RAF) detection in induction machines through stator current signature analysis. In this regard, the Teager-Kaiser energy operator (TKEO) technique for demodulation fault characteristic frequency is used as a pre-processing stage to avoid leakage of the supply frequency. The method has better accuracy due to better spectral resolution and resolvability. Furthermore, computational complexity in the proposed method will be reduced in comparison to the previous conventional ones which have used the Fast Fourier transform (FFT). The proposed technique is tested through synthetic and experimental stator current of WRIM in healthy and faulty conditions with different rotational speeds and fault severities. The results show the validity of the proposed method in rotor asymmetry fault detection through the stator current signature of WRIM. [ABSTRACT FROM AUTHOR]

Due to the possibility of the occurrence of a fault in converters, performance improvement of a converter under faulty conditions is important. In this paper, for improving the performance of the three‐phase cascaded H‐bridge multilevel converters (CHB‐MLCs) with a single faulty cell, the quarter‐and half‐wave symmetry selective harmonic mitigation (SHM) modulation method as well as reducing the number of switching angles (NSA) has been used. Consequently, it helps to reduce the switching frequency (fs) and the number of sentences of the Fourier series thus simplifies the objective function. In addition, the proposed method enables the switching angles of a faulty cell to be transferred to other normal cells per phase. For this purpose, the switching angles of the cells are optimized so that at least one of the cells does not overlap with the other cells in the same phase. By employing the maximum modulation index under the faulty condition, the maximum capacities of the remaining DC sources are used and consequently, the line voltage drop in the output voltage is prevented. To produce a balanced line voltage, the fundamental phase‐shift Compensation (FPSC) method is employed. Simulation and experimental results are presented to confirm the efficiency of the proposed strategy. [ABSTRACT FROM AUTHOR]