This paper presents a 3D model to determine the junction temperature of power semiconductors based on the input mission profiles. For this purpose, a grid-connected wind energy conversion system, including a three-level diode-clamped converter is selected as the case study. This model will be extracted by simulating the whole system, then calculating the power losses using the lookup tables, and predicting the junction temperature using a thermal modeling method. By adopting this procedure for different input ambient temperatures and wind speeds, a 3D model can be created. Thus, for the long-term thermal analysis with enormous number of input data points, we will use this obtained model instead of running the whole simulation cycle over and over again. This will easily generate the junction temperatures for hundreds of thousands of mission profile data in a few seconds.