Real-Time Open-Circuit Fault Diagnosis Method for T-Type Rectifiers Based on Median Current Analysis

T-type rectifiers are widely used in dc fast chargers, super uninterrupted power supplies, renewable energy, and other low- and medium-voltage rectifier applications. These applications often require high equipment reliability and high-quality power but are damaged by the transistor open-circuit fault. This article proposes a novel real-time open-circuit fault diagnosis method for the T-type rectifier based on median current analysis. The method only uses the three-phase currents to obtain the median current and realize the diagnosis. In the rectifier, partial open-circuit faults result in weak fault signals, making the diagnosis challenging. To solve this, the median current obtained by the currents performs fault frequency modulation to enhance the fault signals at first. Then, the ratio of the fundamental frequency to the dc component is used to realize fault detection. The inner/outer fault is identified at the same time. At last, the fault transistor is located by simple change point detection. The change points determine the fault phase and transistor fault. The effectiveness and robustness of the proposed method are verified by the experiment results.