A Fault Diagnosis and Fault-Tolerant Control Method for Open-Switch Faults of Converters in DSEM Drive System

This article proposes a fault diagnosis and fault-tolerant control method for open-switch faults of bridge converters in doubly salient electromagnetic motor (DSEM) drive systems. First, the locations of current sensors are reinstalled to detect the dc-link current and its difference with the freewheeling current of diodes in the lower bridge leg, through which the open-switch faults are diagnosed without affecting the control mode of motors. Moreover, a method to process the features of fault current is studied to reduce the calculation load of the diagnosis method. Then, the driving logic of the switches under different fault conditions is developed for fault-tolerant control. Through the analysis of the problem of uncontrolled phase current caused by inheriting the common duty ratio control method of normal operation in fault-tolerant operation, the independent duty ratio control method is further researched to decrease the ripple of phase currents during fault-tolerant operation. Compared with existing methods, the proposed method has superior rapidity and high reliability. In addition, the suppression of current ripple in three-phase DSEM using the converter based on split capacitors is studied to further improve the fault-tolerant control performance. Finally, the experiments on a 12/8 pole DSEM validate the effectiveness of the proposed method.