Wavelet-Based Open Switch Fault Diagnosis in Cascaded H-Bridge Multilevel Inverter-fed Induction Motor Drive

The Cascaded multilevel inverters are popular in high-power medium-voltage drives because of their modularity and high power handling capacity. An efficient, systematic fault detection scheme is necessary for the reliable operation of the drive. In this paper, a novel open switch fault diagnosis for the three-phase cascaded H-bridge inverter-fed induction motor drive based on the discrete wavelet analysis is proposed. The multi-resolution analysis is performed for the output phase voltages using 'db1' wavelet. The distortion in the voltage waveform during fault reflects in the wavelet coefficients. The mean value of the approximate coefficients of these voltages is identified as the fault feature. The variation in the approximate mean is utilized to locate the faulty switch. The validation of the suggested fault detection approach is done with a three-phase five-level cascaded inverter-fed induction motor drive.