An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 2) WAVELET PACKET ANALYSIS <s> Power converter plays a very important role in switched reluctance motor (SRM) systems, and it is also the easiest one to experience failures. Power converter faults will cause the motor to run in non equilibrium states, and a long time fault operation will lead to motor and other modules damaged, and make the system completely lose working stability. This paper uses an asymmetric bridge converter as the research object with three-phase SRM, employs the wavelet packet decomposition for the phase currents. It analyzes and studies the short circuit fault condition of IGBT, uses an energy discrete degree of the wavelet packet nodes as the fault characteristic, and conducts the corresponding experimental and simulation analysis to verify the effectiveness and practicality of the proposed method. <s> BIB001 </s> An Overview of Fault-Diagnosis and Fault-Tolerance Techniques for Switched Reluctance Machine Systems <s> 2) WAVELET PACKET ANALYSIS <s> Power converters are a key, but vulnerable component in switched reluctance motor (SRM) drives. In this paper, a new fault diagnosis scheme for SRM converters is proposed based on the wavelet packet decomposition (WPD) with a dc-link current sensor. Open- and short-circuit faults of the power switches in an asymmetrical half-bridge converter are analyzed in details. In order to obtain the fault signature from the phase currents, two pulse-width modulation signals with phase shift are injected into the lower-switches of the converter to extract the excitation current, and the WPD algorithm is then applied to the detected currents for fault diagnosis. Moreover, a discrete degree of the wavelet packet node energy is chosen as the fault coefficient. The converter faults can be diagnosed and located directly by determining the changes in the discrete degree from the detected currents. The proposed scheme requires only one current sensor in the dc link, while conventional methods need one sensor for each phase or additional detection circuits. The experimental results on a 750-W three-phase SRM are presented to confirm the effectiveness of the proposed fault diagnosis scheme. <s> BIB002
To detect open-and short-circuit faults, wavelet packet decomposition (WPD) with current reconstruction is proposed by authors BIB002 , BIB001 . In the decomposition algorithm, the wavelet packet coefficients are obtained by where d j,n l , d j+1,2n l ,and d j+1,2n+1 l are wavelet packet coefficients, and h 0(2l−k) and h 1(2l−k) are the low-pass and highpass filter coefficients for decomposition, respectively. The wavelet packet coefficients in reconstruction algorithm are acquired by where g 0(l−2k) and g 0(l−2k) represent the low-pass and highpass filter coefficients for reconstruction, respectively. After decomposition and reconstruction algorithms, the average of the nodes energy is calculated to obtain the discrete degree of the nodes energy. The first eight nodes energy are calculated for fault feature extraction under fivelevel decomposition. This method is accurate and easy to implement for fault detection under different working states, including the variable speed and load conditions.