PhD presentations in November and December 2021: Weihan Li, Philipp Dechent, Jakob Teichrib and Tjark Thien

Wednesday 17.11, Friday 19.11, Friday 26.11 and Friday 10.12.2021

Via video stream. Dial-in data are available by e-mail. Please register at


Wednesday, November 17, 2021
11:00 a.m. [Time zone Berlin] Weihan Li, M. Sc
“Battery digital twin with physics-based modeling, battery data and machine learning“

Lithium-ion batteries undergo performance degradation with time during usage and storage, which increases the need for evaluation of the longevity and reliability of the cell under operation. This work aims to overcome the obstacles of the traditional battery management systems in computational power and data storage capability with the Internet of Things and cloud computing. Battery data are measured and transmitted to the cloud seamlessly to build up the battery digital twin, where intelligent algorithms evaluate the data, extend the battery life and improve the battery reliability. To monitor, predict and optimize the battery use over the whole life cycle, comprehensive battery digital twin functionalities are developed by integrating physics-based and machine learning models and investigating the role of battery data from laboratory and field operation in safe and reliable battery use.


presentation video


Friday, November 19, 2021
10:00 a.m. [Time zone Berlin] Philipp Dechent, M. Sc.
“Simulation and Real-Life assessment of cell-to-cell variation of ageing lithium-ion

Unfortunately, as an essential component of an electric vehicle, the battery has also proven to be the most expensive component, limiting the vehicle's performance, e.g range or power, for a given cost target. If higher spreads and more inferior cell quality can be coped within the system, costs can be lowered by decreasing the number of cells rejected in production. Previous analysis on the impact of variations in commercial lithium-ion battery systems on ageing showed the vital role of spreads in cell parameters of the batteries. The research aims to optimise system topologies for individual applications to find suitable cells, avoid oversizing battery systems and give forecasts of a lifetime and quantifiably failure rates for battery packs while decreasing cost. A simulation toolchain was developed to incorporate variability, and ageing rate spreads in the system design process.


Friday, November 26, 2021
4:00 p.m. [Time zone Berlin] Jakob Teichrib, M. Sc..
„A Hybrid Semiconductor Device for Medium-Voltage DC-DC Converters – The Combination of Thyristor and Transistor Technologies”

The goal of this thesis is to investigate a new hybrid concept that combines the integrated gate-commutated thyristor (IGCT) and the insulated-gate bipolar transistor (IGBT) to reduce both switching and conduction losses, thereby improving efficiency of MVDC converters. First, the concept regarding its structure and operation is presented, followed by a description of the design and construction process of a laboratory prototype. The resulting measurements of the hybrid device are shown and evaluated. In addition, a device and a system simulation are presented. The former reveals the potential of the concept for the case where a theoretical user-defined device is used, and the latter shows system-related efficiency gains of both the real and the theoretical device in a dual-active bridge. In conclusion, the prototype does not deliver clear benefits regarding system efficiency. However, the simulations show that the total losses can be drastically reduced if IGBTs that have lower switching losses than those that were available and installed, are used.


Friday, December 10, 2021
10:00 a.m. [Time zone Berlin] Dipl.-Ing. Tjark Thien
„Optimaler Betrieb von stationären Hybrid-Batteriespeichern am Beispiel des Projekts M5BAT“

Stationäre Groß-Batteriespeicher sind ein wichtiger Baustein für die Energiewende, da sie Erzeugungs- und Lastschwankungen schnell und effizient ausgleichen können. Durch die Kombination mehrerer Batterie-Technologien in einem Hybrid-Batteriespeicher können Wirtschaftlichkeit und Wettbewerbsfähigkeit gegenüber anderen Flexibilitätsoptionen verbessert werden. Ein entsprechendes hybrides Speichersystem wurde im Rahmen des Forschungsprojekts „M5BAT“ errichtet und erprobt drei verschiedene Lithium-Ionen-Batterie-Typen und zwei unterschiedliche Blei-Batterie-Typen. Die Arbeit stellt verschiedene Energie-Management-Algorithmen vor, welche anhand von Simulationen des M5BAT-Batteriespeichers analysiert und verglichen werden. Darüber hinaus werden Simulationen mit abgewandelten Speichersystemen präsentiert um den Einfluss der Hybridisierung aufzuzeigen.