Enhanced Threshold Point Calculation Algorithm for Switch Fault Diagnosis in Grid Connected 3-Phase AC–DC PWM Converters

Abstract

The resilience of systems with alternating current (AC)−direct current (DC) converters has been investigated with the aim of improving switch fault diagnosis. To satisfy this aim, this paper proposes a switch fault diagnosis algorithm for three-phase AC−DC converters. The proposed algorithm operates using the phase current instead of the average current to reduce the calculation time required for fault switch detection. Moreover, a threshold point calculation method is derived using a theoretical analysis, which was lacking in previous research. Using the calculated threshold point, a switch fault diagnosis algorithm is obtained to detect faults independent of the load condition. Using the proposed algorithm, switch faults can be detected within 4 ms, which is the recommended value for uninterruptible power supply (UPS). The theoretical analysis, the operating principle, and the experimental results on a 3-kW grid-tied AC−DC converter test-bed are presented herein, which verify the performance of the proposed algorithm.

Keywords

• AC–DC power conversion
• fault diagnosis
• counting method
• threshold point