Reliability Evaluation of SPWM Multilevel Inverters Based on IEC-TR-62380 Standard

Reliability Evaluation of SPWM Multilevel Inverters Based on IEC-TR-62380 Standard

In this paper an improved method is proposed for the evaluation of the failure rate and mean time between failures (MTBF) in the multilevel inverters. Generally, MIL-HDBK and IEC handbook are the two prominent standards used for calculation of the failure rate. Many papers used MIL-HDBK for failure rate analysis. However, some effective parameters are not considered in the MIL-HDBK standard. Accordingly, theoretical calculations of the failure rate and MTBF based on MIL-HDBK are not accurate. In this paper failure rate and MTBF are calculated based on IEC handbook standard. Since, the IEC handbook standard considers environmental conditions, package type and operation time for each component, the theoretical calculations based on this standard are more accurate than MLL-HDBK one. Power loss is used in the calculations of failure rate, MTBF, junction temperature and technical and economical analysis of a system. Therefore, improved equations are used for calculations of the conduction and switching losses in the SPWM multilevel inverters. Also, precise and estimated ways for calculation of the conduction and switching times are presented. As a result, the precise theoretical calculations of the failure rate, MTBF and junction temperature are obtained by these equations. Finally, the proposed method is evaluated by 5-level NPC simulation in the PLECS software. Theoretical and simulation results of the conduction and switching losses are in a good agreement with each other.