Fault Diagnosis and Fault-Tolerant Control Scheme for Open-Circuit Faults in Three-Stepped Bridge Converters

A novel fault diagnosis method and a fault tolerant scheme for open-circuit faults on a traction rectifier are proposed in this paper. When an open-circuit fault occurs in any leg of the rectifier, indication will be generated accurately to identify the faulty leg without utilization of any extra sensors. Furthermore, the faulty rectifier can be reconfigured to maintain its full output rate to prevent traction rectifier breakdown. The fault diagnosis process is neither related to control trigger signal nor the load fluctuation. The involved parameters are the input and output voltage of the rectifier, which are the most common parameters in rectifier control. Working under zero voltage and zero current, five additional switch sets are adopted for the fault-tolerant control process to reconfigure the topological structure between the traction rectifier and the traction transformer, meanwhile the original structure of the rectifier is retained. Analysis, design, and implementing consideration for both normal and abnormal operating situations of the traction rectifier are present in this paper. The experiment is processed to verify the effectiveness of the theoretical analysis.