Fault Diagnoses for Industrial Grid-Connected Converters in the Power Distribution Systems

The reliability of power electronics converter systems (PECSs) is of paramount importance in industrial, commercial, aerospace, and military applications. Therefore, the knowledge about the fault-mode behavior of a converter system is extremely important from the perspective of improved system design, protection, and fault-tolerant control. Faults of power switches in PECSs are classified as short circuit (S-C) faults, open circuit (O-C) faults, and degradation faults. S-C faults in most cases cause an overcurrent condition that is readily detected and acted upon by standard protection systems such as overcurrent, undervoltage, or overvoltage protection. However, the degradation faults and O-C faults often do not trigger fault protection but rather cause system malfunction or performance degradation. Since the standard protection system may not detect these fault types, their diagnoses become critical for PECSs. This paper presents new methods for fault detection, localization, and diagnosis for grid-connected power converters and the identification of the unbalance input voltage to the converter. The proposed fault diagnostic algorithms are verified in both the simulation and the experimental environments in order to evaluate their robustness and effectiveness. The power converter under the study consists of three main subsystems: the three-phase uncontrolled rectifier, the boost chopper, and the single-phase inverter circuits.