A Unified Open-Circuit Fault Diagnosis and Condition Monitoring Method for Three-Level T-Type Inverter

Traditional fault diagnosis (FD) and condition monitoring (CM) methods for three-level T-type (3L-T) inverters are studied separately, which is not conducive to guaranteeing the reliability of the 3L-T inverter in an all-around way. This article presents a unified open-circuit FD and CM method for the 3L-T inverter based on the proposed on-state voltage measurement circuit (OVMC). The designed OVMC comprises a voltage limiter, an absolute value circuit, and a minimum value circuit, separating all the OVs and actual switching state information with a few devices and terminals. The corresponding sampling method is designed under the space vector pulsewidth modulation mode, and the sampling frequency is only twice the switching frequency. Three exceptional cases are considered during the implementation to achieve accurate OV sampling. The proposed method for fault locating requires only a straightforward lookup table without complicated feature extraction and threshold setting steps. Meanwhile, the FD results would help to correct the OV distribution. Experimental results demonstrate that the proposed unified FD and CM method merits high measurement accuracy, fast response speed, and short FD time.