Effective thermal simulation of power electronics in hybrid and electric vehicles

Abstract

Thermal management is critical in development of hybrid and electric vehicles since they contain multiple high-density power modules that require compact integration and effective cooling. During operation the power modules generate large amounts of heat leading to significant temperature increases and thermal gradients inside dies and across the packages. Electro-thermal simulation is needed to choose the best operating regime to meet the thermal and electrical requirements. However, this is usually computationally expensive. One effective method is to develop a compact but accurate thermal model to capture the thermal physics that can be used in the system-level electro-thermal model. In this paper an effective Model Order Reduction (MOR) is developed that drastically reduces the number of Degree of Freedoms (DOFs) of the original large-dimension ODE system. Finite Element Analysis (FEA)/ Computational Fluid Dynamics (CFD) simulation is first conducted to find the optimal pin-fin to rear channel ratio and the optimal pin fin shape that gives lowest peak temperature and pressure drop. The convective heat transfer coefficients exacted from FEA/CFD is input to the MOR model. The MOR model is then applied to a converter assembly, and results show that it can reduce the computation time from 2 hours to 1 second with reasonable error compared to the FEA/CFD predictions. The MOR thermal model can be further coupled with electrical circuit models to form a system model to predict the temperature profile and the power modules' electrical transient performance.