Fault Diagnosis Scheme for Open-Circuit Fault in N+2 Converter of Six-Phase SRM Using Midpoint Current Spectrum Analysis

Abstract

In this paper, a six-phase $\text{N}+2$ power converter for switched reluctance motor is studied. An open-circuit fault diagnosis and faulty devices location scheme based on midpoint current spectrum analysis is proposed. In order to realize fault diagnosis, five fault cases are distinguished, including single-phase fault, multiphase fault and midpoint switch fault. Taking the phase current frequency as the fundamental frequency, the DC component, the fundamental frequency component, and the second harmonic component have different change rules in the five fault cases. The third harmonic component is used as the denominator, three spectrum coefficient could be obtained and be used as the fault characteristic. Through this scheme, using a single current sensor to detect the midpoint current can ensure open-circuit faults accurately. After the fault case is confirmed, the amplitude of the harmonic component is used to define a fault location threshold, and the threshold is numerically compared with the midpoint current to realize the faulty bridge arm location. Finally, the complete process of fault diagnosis and location is described, then the effectiveness of the proposed diagnosis method is validated by the simulation and experiment.

Keywords

• Switched reluctance motor (SRM)
• power converter
• fault diagnosis
• spectrum analysis