A Fast Electro-Thermal Model of Traction Inverters for Electrified Vehicles

In this paper, a fast electro-thermal model of traction inverters for electrified vehicles is proposed. First, a thermal model considering the thermal coupling is presented and experimentally verified. The impact of the thermal spreading effect, heat convection, and temperature-dependent material thermal properties on the accuracy of the linear assumption is investigated by ANSYS-Fluent simulation. In order to reduce the influence of the temperature-dependent thermal conductivity on the accuracy of the thermal model, the average temperature is applied to determine the thermal conductivity of the power module package. Second, an accurate temperature-dependent switching power loss model is represented as the lookup table through experimental measurements. In order to simplify the lookup table, the switching power loss is considered proportional to the dc-link voltage and, therefore, the inputs of the lookup table are current and temperature. Finally, a scheme to speed up the online junction temperature estimation is proposed by considering both the thermal network properties and the required accuracy. With the proposed calculation rate determination method, the total computational time for the junction temperature estimation is reduced significantly.