We congratulate Per Widek, Lund University and Volvo Powertrain Technology, on a successful PhD defense!
Title: Modelling of electric power systems in electric vehicles
Abstract
The rapid electrification of heavy-duty vehicles has introduced traction voltage systems (TVS) with electrical scale and complexity not previously seen in on-road applications. Multiple power electronic subsystems interact through long cables and frequency-dependent impedances, making conducted electromagnetic interference (EMI) a system-level phenomenon. Differential-mode (DM) and common-mode (CM) disturbances generated by converter switching propagate through intentional and parasitic impedances up to approximately 200 kHz for DM behaviour and 3 MHz for CM behaviour.
This thesis combines measurements on commercial battery-electric vehicles with physically based modelling and system-level simulation. A dedicated 96-channel, 60 MS/s measurement system is developed to capture CM and DM quantities across the distributed TVS with ability to record up to one hour of full resolution data. The
results show that CM behaviour is governed by the ratio between symmetric CM capacitances and asymmetric parasitic capacitances, referred to as the X-factor. Both the CMDC voltage and the resulting CM current paths depend on capacitance placement, cable and junction-box impedances and non-ideal semiconductor behaviour.
A library of validated subsystem models is developed and calibrated with measurements, including converters, batteries, cables, filters and interconnection components. State-space reduction and eigenvalue analysis preserve the required bandwidth while enabling computationally feasible vehicle-level simulations. The simulations reproduce the measured CM and DM behaviour, quantify the influence of distributed impedances and measurement artefacts such as Break-Out Boxes and demonstrate how phase-shifted switching suppresses CM disturbances. The combined results provide system-level guidelines for EMI-aware design, including CM capacitance placement, use of damped DM filters and strategies that reduce sensitivity to subsystem interaction.
The thesis establishes a system-level framework for analysing, modelling and mitigating conducted EMI in commercial battery-electric vehicles and demonstrates how measurement, modelling and simulation must be integrated to understand and control behaviour in electrically large traction voltage systems.