Buffered-HLL – Grid friendly, cost-efficient high-power charging system for medium sized, commercial public transport in suburban areas
Daniel Müller, Michael Wißbach, Hendrik Schaede-Bodenschatz, Julian Brendel, Martin Wißmüller
In 2021, battery electric vehicles from various bus manufacturers were deployed in numerous large cities, supported by adapted charging infrastructure. Two main concepts had become established: depot charging, in which buses with larger batteries were mainly charged at night in the depot, and route charging, in which vehicles with smaller batteries were recharged at selected stops. The project expanded on these approaches and investigated the application of inductive charging technologies for passenger cars at a test site, as well as the use of battery-electric buses in regular public transport operations. As part of the project, technologies and processes for an innovative, grid-oriented high-performance charging infrastructure for privately operated public transport companies in suburban and rural areas were developed, tested, and analyzed.
The aim was to assess the potential for electrifying bus fleets. The investigations showed that medium-sized bus companies in rural areas in particular faced special challenges, including longer distances, tighter turnaround times, and less well-developed power grids.During the project period, a charging infrastructure with depot and route charging was developed and tested over a period of 18 months in various operating phases (city traffic, interurban traffic, combination). The specification and integration of the charging infrastructure proved successful; components such as storage, HV box, DC energy meter, network module, enclosure, and pantograph station were efficiently dimensioned and integrated. The flywheel energy storage system developed for HPC charging stations was put into operation. An AC depot charging system and a DC high-current HV box were also successfully installed and used. A modular DC energy meter was developed and connected to a cloud, which facilitated data analysis. The practicality of the charging infrastructure was confirmed in regular operation, with employees trained and the infrastructure successfully implemented. Finally, an optimal electrification strategy was formulated and the potential of innovative charging systems was evaluated.
The results underscore the importance of customized charging infrastructure for the electrification of bus fleets in rural and suburban areas and provide valuable recommendations for future projects.