Diagnosis of Current Sensors Incipient Faults in Three-Phase Three-Level NPC Rectifiers Based on Adaptive Sliding Mode Observer

This article introduces an incipient fault (IF) diagnosis approach for current sensors (CSs) in three-phase three-level neutral-point-clamped (3L-NPC) rectifiers using an adaptive sliding mode observer (SMO) for the first time. The method begins by constructing a model of the 3L-NPC rectifier system incorporating IFs in CSs. Subsequently, through system augmentation and transformation, the IFs within the CSs are reconstituted. Following this, an adaptive SMO is developed with swift convergence and the ability to mitigate high-frequency oscillations, aimed at precisely estimating the system’s reconfiguration status. Moreover, the difference between the real and estimated values of the system’s reconfiguration status is used to generate a detection parameter along with its adjustable thresholds. This approach not only facilitates the detection of the entire evolution process of IFs but also enables the detection of typical faults. Finally, experimental findings are showcased to authenticate the precision and robustness of the diagnostic approach put forth in this study.