A Novel Diagnostic Technique for Open-Circuited Faults of Inverters Based on Output Line-to-Line Voltage Model

An output line-to-line voltage model-based fault diagnostic technique is presented in this paper. From the theoretical analysis of the output voltage under normal and faulty conditions, a preprocessing method is developed to extract fault features from diagnosis eigenvalue. A voltage envelope line is generated by the proposed voltage envelope function. By comparing the preprocessed diagnosis eigenvalue and the voltage envelope, single-switch open-circuit faults can be located precisely. Because the proposed method does not rely on the accurate amplitude of the output line-to-line voltage, the influence of the load changing is minimized and simple hardware is adopted, which has advantages of low cost, high reliability, and short diagnosis time. Moreover, as long as the inverter output voltages have the feature of periodic nonpositive and nonnegative, this method is valid no matter what control strategy is adopted by the inverter and no control signal is required for the diagnosis process. The prototype system is tested to validate the adaptability of the proposed method under different conditions, such as the diverse loads, various control strategies, and fault-occurrence time.