Fault diagnosis of power transistors in a power converter of SRM drive based on a state inverse solution

Abstract

Switched reluctance motor drives are a common technology used in traction motor drives. Herein, an online method is proposed for the fault diagnosis of power transistors in the popular asymmetric half-bridge power converter of the SRM drive. Based on the rearrangement of three current sensors, each phase current was first calculated by solving equations associated with their detected values and the drive signals of the transistors. The faults in the transistors were then preliminarily detected by monitoring the error between the calculated sum of currents and the sum of actual phase currents detected by a current sensor. Once a fault was identified, the actual states of all transistors of the power converter were solved for inversely using a mathematical model and the necessary rule for a trade-off. Then, the faulty transistors and the fault types were identified by comparing the actual states with the drive signals. Compared with prevalent methods, the diagnostic range of the proposed scheme was wider, and its control modes and the number of motor phases were not limited. A higher accuracy than currently available methods was its prominent advantage. The effectiveness of the proposed solution was also validated on a three-phase 6/4 SRM drive.