An Open Circuit Fault Diagnosis Method of T-Type Three-Level Inverter

In this paper, a fault diagnosis method based on a spatial trajectory diagnosis network model is proposed for T-type three-level inverters. By providing a rigorous theoretical derivation of the phase current distortion under switching constraints and neutral-point voltage shifts, the inherent mapping from time-domain waveform clipping to 3D trajectory deformation is revealed. A classification network model is employed to process these spatial point sets using symmetric functions for robust fault recognition. The proposed method is validated on a dSPACE experimental platform, showing that diagnostic accuracy remains above 92.5% even under 10% white-noise interference. Furthermore, a comparative study with existing methods demonstrates that the proposed approach achieves an optimal balance between hardware cost and diagnostic depth, identifying both single- and multi-switch faults within 16.2 ms without requiring additional voltage sensors.