Analysis of DC Current and Voltage Ripples of Electrical Drivetrains for HV Electrical System Emulation

State-of-the-art testing of traction inverters is conducted using PHIL-based testbeds. These systems, which include a battery emulator and an E-Motor Emulator (EME), offer significant advantages over dynamometer testbeds in terms of test duration, reproducibility, parameterization and protection of the unit under test. In these advanced systems, the physical modeling of the AC side (e-motor) is highly detailed, accounting for factors such as iron saturation effects, current harmonics, and loss models. However, the DC side models are limited to a constant voltage and an internal resistance model, neglecting other components like additional traction inverters or DC/DC converters connected to the HV electrical system and their impact on voltage and current ripples – high-frequency oscillations in the current that can arise from power electronic systems. This research project aims to address this gap by developing an HV electrical system emulator that considers these influences. This contribution explores the modeling of electric powertrains, focusing on the ripple currents impressed by traction inverters and their propagation within the HV electrical system. Initially, the fundamental components of HV electrical systems are outlined. Various models of batteries, traction inverters and motors (PMSM and IM) are then discussed. Special attention is given to the modeling of ripple currents. Experimental studies based on simulations are presented to illustrate the ripple currents, the impressed frequency components, and their propagation within the HV electrical system. The presentation also discusses strategies for mitigating ripple currents to protect electrical components. Finally, future trends in electric powertrains are examined, along with the next steps and upcoming work related to the emulation of the HV electrical system. The challenges that need to be addressed are also discussed.