A System-Level Framework for IGBT Open-Circuit Fault Diagnosis in the Grid-Tied System

Existing inverter fault diagnosis mainly focuses on individual components, such as IGBT open-circuit faults or current sensor faults. However, the grid-tied inverter is an integral part of the PV system, and the output currents are not only affected by the operation state of the inverter (opencircuit faults, degradation, etc.), but also by the operation modes for the whole system (steady-state, low-voltage ride through) and the operation state of the other subsystems, e.g., voltage and current sensor faults, etc. Thus, a system-level IGBT open-circuit fault diagnosis framework is proposed in this paper. First, the effects of the different operating modes and various subsystems of the system on the three-phase currents and the IGBT opencircuit fault diagnosis model are analyzed. Then, a two-stage multi-model system-level fault diagnosis method is proposed, including the system operation mode identification and specific model invocation to further ensure the reliability of the diagnostic model.