Next-Generation Charging Systems for Electric Mobility
Future generations of high-power electric vehicles could employ higher battery voltages(>1000V), enabling higher driving and charging efficiency. This project aims to conceptua-lise and realise highly compact and efficient charging systems for such EVs.
The rapid electrification of individual transport is accelerating the need for efficient, high-power charging stations that provide convenient and reliable charging for higher power electric vehicles (EVs) such as trucks or construction vehicles. Currently, most EVs are equipped with 400 V or 800 V battery systems. The transition toward higher battery voltages will significantly improve charging efficiency by reducing current levels, minimising conduction losses and additionally reducing the cable weight. In this project, EVs with 1200 V batteries are investigated.
The higher battery voltage paves the way for next generation megawatt-range charging stations, capable of charging EV batteries from 20% to 80% state of charge in roughly ten minutes, making ultra-fast charging both practical and sustainable. A key goal of this research project is to develop concepts for high-power charging stations connected to the medium-voltage grid, operating at DC output voltages up to 1200 V. In this context, phase-modular and multi-level converter topologies, which also employ wide-bandgap semiconductors are of particular interest. Various system configurations will be analysed and compared, and an optimisation routine will be developed. Scaled-down prototypes will be built to experimentally validate the simulation and optimisation results.
Onboard chargers (OBCs) allow users to charge their EVs from the LV grid at a lower power. Next-generation bidirectional onboard chargers are key enablers for vehicle-to-grid (V2G) ancillary services, which are becoming increasingly important as electrical grids rely more heavily on renewable energy sources.In this project, OBC topologies are investigated. In particular multilevel, non-isolated charger topologies are of interest due to the potential gains in power density and efficiency achieved by eliminating the high-frequency transformer. Multilevel converters also allow to reduce the filter volume compared to conventional two-level converters while also facilitating using GaN HEMTs as switching devices. GaN devices have similarly low conduction and switching losses as SiC devices while offering the potential for substantially lower cost in the near future.