A Nonintrusive IGBT Open-Circuit Fault and Current Sensor Fault Diagnosis Method for Grid-Tied Three-phase Three-Wire Inverter with Two Current Sensors

In some cases, only two current sensors are available in three-phase three-wire (3P3W) inverters. This occurs when one of three sensors is faulty, or the inverter is equipped with only two sensors to save cost. There has been no method addressing the diagnosis of both IGBT open-circuit faults and current sensor faults in the 3P3W inverter with only two current sensors. In order to solve this problem, a nonintrusive method based on average output voltage deviations is proposed. The deviations between the measured and estimated output line and phase voltages are utilized to detect and locate the fault. With average model, this method can diagnose the fault fast with only signals available in the controller. Therefore, no extra sampling or diagnosing circuits are needed. Besides, the error-adaptive thresholds are adopted to ensure the robustness. Finally, experimental results verified the effectiveness.