IGBT Open-Circuit Fault Diagnosis of Single-Phase Cascade NPC Rectifiers Based on Residual Rate

In order to realize the real-time open-circuit faults diagnosis of insulated gate bipolar transistors (IGBTs) of single-phase cascaded neutral point clamped rectifiers (SPCNPCR), an open-IGBT fault diagnosis method based on residual rate is proposed. First, a hybrid logic dynamic model (MLD) of a single-phase cascaded midpoint clamped rectifiers is established to estimate the input voltage and grid current. Then, compared with measured voltage and current, the changes of voltage residuals are obtained to locate the fault cells, and change rates of current residuals are obtained to analyze residual characteristics of IGBT faults through the theoretical analysis and simulation, respectively. The specific switch signal combination test is used to achieve the detection and location of single IGBT open-circuit faults in different modules. The simulation results have illustrated the proposed diagnostic m ethyl has good diagnostic performance.