Coupled Electrothermal Analysis with Reduced Order Models for Optimizing GaN HEMTs Performance in Traction Inverters

In electric vehicle power electronics (PE) systems, particularly for traction inverters, it is pivotal to effectively manage electrical, thermal, and mechanical stresses experienced by Gallium Nitride (GaN) High Electron Mobility Transistors (HEMTs), under different operational conditions. Analysis of these stresses through simulations, enables initial assessments and optimizations before construction of physical prototypes and experimental testing. However, conventional simulation techniques like Computational Fluid Dynamics (CFD) demand significant processing resources and time, being disadvantageous in PE system-level simulations. A Linear Time-Invariant (LTI) thermal reduced order model (ROM) of an inverter phase leg module based on embedded GaN HEMT dies is considered in this research, as derived from 3D CFD transient thermal simulations. The ROM is coupled with a PLECS/MATLAB simulation of a full Permanent Magnet Synchronous Motor (PMSM) traction drive, including temperature dependency of GaN HEMT's drain source on-resistance, thus allowing fast coupled electrothermal simulations and accurate estimation of GaN HEMT temperature changes in response to generated power losses during varying torque/speed operations. The mechanical response of the inverter phase leg module in response to a critical thermal loading scenario (i.e., rapid acceleration and deceleration) highlights potential permanent deformation of the topside copper metalization layers and microvia interconnects. The proposed workflow allows a fast coupled electrothermal and thermomechanical simulation framework for optimization and rapid identification of critical conditions of next generation PE systems.