A Simplified Approach for Estimating Junction Temperature of IGBT Modules Considering Variable Thermal RCs

Over the past decades, power electronic circuits have been widely used in various equipment and industry sectors. Due to this widespread use, there is a lot of interest in understanding how to improve the lifespan of these circuits. Therefore, power modules have been evaluated as the most failure-prone component in these converters, and what is the most important in these components is the thermal management. In this paper, a simple method for determining the junction temperature of an IGBT module, taking into account the effects of operating temperature on the physical characteristics and behavior of the materials used within the module, is proposed. A resistance-capacitance (RC) thermal model is usually used to estimate the temperature, but the main drawback of the conventional model is that the values of the RC parameters are considered constant. In fact, thermal conductivity and specific heat capacity will change with temperature fluctuations. The proposed approach was implemented in the MATLAB environment by using a recursive loop, which modifies the RC values according to the prior temperature. The results showed that in the case study, the estimated junction temperature with variable RCs is 11.25% higher than the model with the fixed RC values.