Closed-loop real-time simulation of the thermal and electromagnetic behavior in electric drive trains: Optimizing model accuracy for virtual prototyping

This paper presents a coupled electromagnetic and thermal simulation of Permanently Excited Synchronous Machines (PMSM) in the context of virtual prototyping in a real-time Hardware-in-the-Loop (HiL) environment. Particularly in real-time simulations, thermal influences are often neglected due to the increased complexity of a coupled simulation. This results in inaccurate simulations and incomplete design optimizations. The objective of this contribution is to enable a precise and realistic real-time simulation that represents the electromagnetic as well as the thermal behavior. The electromagnetic simulation is executed used a Field-Programmable Gate Array (FPGA) and parameterized by Finite Element Analysis (FEA) results. The thermal model is based on a Lumped-Parameter-Thermal-Network (LPTN), which is based on physical laws, geometry parameters and material specifications. The simulation results are validated with testbench measurements to ensure the accuracy of the overall model. By combining electromagnetic and thermal models, design changes and thermal management can be evaluated simultaneously in real time. Compared to simulations that consider the thermal behavior separately, this coupled analysis enables more accurate evaluation and optimization. Embedding real-time thermal simulation into the virtual prototyping process not only allows frontloading of the electric machine development process, but also enables a direct interaction between machine design and controller development. This approach leads to improved predictions of temperature distributions and thermal losses under transient operating conditions, helping to identify and correct potential design errors at an early stage.