Electro-thermal modelling of multichip power modules for high power converter application

In a compact power electronics systems such as converters, thermal interaction between components is inevitable. Traditional RC lumped modelling method does not take that into account and this would cause inaccuracy in the predicted temperature in the components of the systems. In this work, numerical simulation have been used to obtain detailed temperature distribution in power devices and the parameters for a Foster network behavior thermal model are extracted so that the thermal interaction can be accounted for and the model can be used to predict temperatures at all critical layers of the components. An ad-hoc conventional three-phase voltage source inverter (DC to AC converter) with a rating of 7.8 KW has been studied in this work as an example of the application of the proposed framework. The key component in the converter is a 75A/1200V rated IGBT module. A power electronics circuit simulator is used to predict the power losses in the IGBT module and a Finite Element Analysis software is used to obtain the transient temperature profile in the module and the behaviour thermal model parameters are extracted using curve-fit approach. The resulting combined electro-thermal model is analysed using the circuit simulator again to obtain the temperature for various loading conditions. The results show that the proposed method can significantly improve the accuracy of predicted temperatures in the IGBT modules.