High-Fidelity Voltage-Behind-Reactance Model of Electrically Excited Synchronous Machines Using Flux Maps

Electrically excited synchronous machines (EESMs) have historically been used as efficient and reliable synchronous generators. However, the actual need for cost-effective, sustainable motors without rare-earth magnets has notably increased the interest in EESMs, which are considered a valid replacement for permanent magnet synchronous machines (PMSMs) in electrified powertrains. As the electrical machines employed in automotive applications exhibit deep magnetic saturation, the EESM introduces significant challenges in properly modeling the magnetic behavior, especially considering the cross-coupling effects between stator and rotor. EESM-based electrical drive development requires accurate circuital models to predict EESM behavior. Therefore, this article proposes a novel voltage-behind-reactance (VBR) model based on flux maps provided by finite element analysis (FEA) or experimental identification procedures. The proposed VBR model has been validated in simulation and experimentally on a commercial 100 kW EESM currently used on the Renault Zoe EV R135, demonstrating its potential for accurately modeling EESMs designed for traction applications.