Open Circuit Fault Diagnosis Method of Three-Level Inverter Based on Generalized S-Transform

In fault diagnosis methods for neutral point clamped (NPC) three-level inverters based on signal analysis, the frequency domain analysis method lacks local time-frequency analysis capabilities, and the extracted fault features cannot locate the time of fault occurrence. Additionally, traditional time-frequency analysis methods have issues with window function selection and lack of window width adaptability. A method combining generalized S-transform with singular value decomposition (SVD) is proposed for fault feature extraction. Based on this, SVD is further applied to reduce data dimension, enabling feature extraction for open-circuit faults in three-level inverters. The extracted fault feature vectors are input into a limit learning machine for fault classification. Finally, the proposed algorithm is validated on a simulation platform. Simulation results demonstrate that fault features can be effectively extracted from the transient nonlinear current signals of a neutral-point-clamped inverter during an open-circuit condition, enabling diagnosis of single-tube and dual-tube open-circuit faults.