Construction of a multi-frequency compact electro-thermal model for IGBT-based power inverters

This paper presents an approach for constructing a multi-frequency compact electro-thermal model of IGBT-devices as inverters. Frequencies and time-scales of heat oscillations of transistors and diodes of IGBT devices were revealed as a function of operating parameters of inverters. It was shown that heat could oscillate according to different frequency domains, one referring to the load amplitude modulation in the range 0.1 Hz-50 Hz and the other associated with the switching frequency of the IGBT in the range 1 kHz-20 kHz. A methodology was established for designing lumped RC thermal networks achieving good precision and low computational time for temperature calculation with respect to different components of heat oscillations. It was found that temperature varies according to different time-windows ranging from nanosecond to second. The model reduction strategy has been implemented on a unidirectional heat flow through a layered structure corresponding to the cross-plane of the IGBT device. The approach is based on analysis of heat diffusion rates and thermal penetration depths with regards to device topologies, materials, and frequencies. Results are presented and discussed.