Wavelet Packet Transform Based Protection of Disturbances in Three-Phase Interior Permanent Magnet Motor Fed from Sinusoidal PWM Voltage Source Inverter

In this work, a novel wavelet packet transform (WPT) based algorithm is developed for the on-line protection of a three-phase interior permanent magnet (IPM) motor fed from a sinusoidal pulse width modulated voltage source inverter (PWM-VSI). The proposed algorithm is implemented and tested on-line using the ds1102 digital signal processor board for diagnosing and detecting different disturbances occurring in the stator terminals of the motor. The criterion for the WPT-based protection is the comparison of the second level high frequency details (dd²) of different faulted currents using the selected mother wavelet ´db3´ with a threshold determined experimentally during the healthy operating condition of the motor. An experimental setup for the disturbance detection incorporating also the protection circuit is developed in order to accommodate the on-line testings on a laboratory 1-hp IPM motor. In all the tests carried out, the proposed algorithm identified every disturbance promptly and properly, and initiated a trip signal almost at the instant or within one cycle of the fault occurrence based on the 60 Hz systems