Transient junction temperature prediction of IEGT in modular multilevel converter sub-module based on FEM

Abstract

Compared with plastic module IGBTs, press-pack IEGTs (PPI) can carry higher current due to the special package design with double-side cooling and the elimination of bonding wire, and are perfect devices for VSC-HVDC converter. The reliability of VSC-HVDC is closely related to the junction temperature of PPI devices, so it is extremely important to accurately predict the junction temperature of PPI. The traditional junction temperature prediction method, basing on RC-lumped network, is employed widely to estimate the average junction temperature. However, it’s difficult to demonstrate the details of each chip when considering the thermal coupling of IEGT chip. Therefore, a prediction method of junction temperature considering thermal coupling is proposed to calculate the transient junction temperature of PPI in the modular multilevel converter (MMC). By calculating the current of the MMC sub-module, the PPI loss model is established in ANSYS/TwinBuilder. Besides, the thermal network of PPI with the heatsink is established by CFD. Furthermore, the transient junction temperature of PPIs is calculated with the 1500MW MMC system. The results show that the proposed prediction method can not only predict the transient junction temperature of PPI modules in MMC sub-module, but also obtain the details of thermal distribution.