Simplified Estimation of Junction Temperature Fluctuation at the Fundamental Frequency for IGBT Modules Considering Mission Profile

The junction temperature at the fundamental frequency cannot be ignored in a lifetime evaluation of insulated-gate bipolar transistors (IGBTs) with a long-term mission profile. Therefore, it is very important in terms of calculation speed and accuracy to simplify the loss curve when calculating the thermal fluctuation at the fundamental frequency. This paper proposes a mathematical analysis method for the junction temperature fluctuation at the fundamental frequency based on an equivalent sinusoidal half-wave loss. The dynamic and static parameters of the devices are tested by an experimental platform, and accurate device loss models are established through a case study of a 1.5 MW direct-drive wind turbine grid-connected model. The accuracy of the proposed calculation model is compared with that of a time-domain simulation and the two-step loss pulse method. Considering different output frequencies, the accuracy of the proposed method is further discussed. Based on actual wind speed data, the proposed method is used to calculate the junction temperature of an IGBT module in a grid-side converter. The results show that the proposed method can improve the accuracy of the reliability evaluation of wind power converters.