Open-Circuit Switch Fault Diagnosis and Fault- Tolerant Control for Output-Series Interleaved Boost DC-DC Converter

This article proposes a fault-tolerant control method for an input-parallel-output-series (IPOS) converter under open-circuit switch failure, which mainly focuses on two parts: fault diagnosis (fault detection and fault identification) and remedial action. The fault diagnosis is realized based on immersion and invariant observer (IIO), which has strong robustness to parameter uncertainty and external disturbances, and therefore, it can be designed using only the crude converter model with nominal parameters. Moreover, the sampling frequency required by the fault diagnosis is the same as the frequency required by the system controller. Thus, the fault diagnosis module can be easily embedded in the well-designed power system without extra sensors. Based on the method, the open-circuit fault in power switches can be detected and identified within two switching periods. As for remedial action, two redundant switches are needed for postfault reconfiguration. Also, the remedial action can be immediately triggered after the switch failure is detected. To reduce the complexity of remedial action, the same postfault reconfiguration will be carried out for the open-circuit failure in different switches. Besides, system controllers are also carefully designed to guarantee the performance of the postfault converter. Both simulations and experiments are conducted for the validations, and the results have shown the effectiveness, robustness, and rapidity of the proposed method.