Performance Evaluation of an Embedded – WPT-Based Digital Protection for IPMSM Drives

This paper presents the implementation and performance evaluation of an embedded digital protection for three-phase (3φ) interior permanent-magnet synchronous motor (IPMSM) drives. The presented digital protection is established through extracting the high-frequency subband present in the d-q-axis components of the currents drawn by the protected IPMSM. The desired high-frequency subband is extracted using the wavelet packet transform (WPT) from the d-q-axis current components, which are obtained from the controller of the IPMSM drive. The extracted high-frequency subband contains signature information that allows detecting and classifying transient disturbances into fault and nonfault events. The presented method is insensitive to the variations in the drive parameters, loading levels, nature of electrical faults (open circuit or short circuit), and operation of the drive controller. These features of the d-q WPT-based digital protection simplify its implementation and facilitate its embedding within the controller of the IPMSM drive. The performance of the d-q WPT-based digital protection is experimentally evaluated on a laboratory 5-hp IPMSM drive for various fault and nonfault events. Test results demonstrate fast, accurate, and reliable detection, classification, and response to fault and nonfault events.