Open-Circuit Fault Diagnosis for Three-Level T-Type Inverters Based on Voltage Vector Trajectory Centroid Deviation Characteristics

Abstract

The safety and reliability of inverters are crucial for the stable operation of the entire system, making accurate and effective OC (open-circuit) fault diagnosis methods particularly essential. This paper proposes an OC fault diagnosis strategy for three-level T-type inverters based on voltage vector trajectory centroid deviation characteristics. By analyzing the spatial distribution characteristics of the output voltage vector trajectory after an OC fault, it is found that the trajectory centroid undergoes varying degrees of displacement when a single-switch OC fault occurs. The magnitude and phase characteristics of the vector from the origin to the displaced centroid can be utilized to identify different single-switch OC faults. For double-switch combined faults, the centroid deviation vector can be equivalently characterized by the linear superposition of single-switch fault vectors. The centroid deviation vector features enable the identification of fault types where the vector is non-zero. Furthermore, the centroid vector characteristics of the first-quadrant trajectory can distinguish double-switch faults where the centroid vector is ac zero vector. The proposed method can diagnose single-switch faults and arbitrary double-switch combined faults in any phase. The diagnostic algorithm features low computational complexity and fast diagnosis speed, effectively addressing the issue of load sensitivity in conventional diagnosis methods.