Power Electronics

Focus:

• Semiconductor power electronics
• Prototype Development
• Multilevel energy converter
• Modulation techniques
• Reconfigurable battery systems

Summary:

The energy efficiency of the electric powertrain has a significant influence on the range of electric vehicles. One approach frequently discussed in the literature to increase energy efficiency is the use of modular multilevel converters, also known as multilevel energy converters or multilevel inverters.
Multilevel inverters are power electronic systems that output step-like voltages at the output. A lithium-ion cell can be used as the source. The battery cell is equipped with semiconductor switches and this reconfigurable battery cell is connected in series and parallel with others of the same type.

In determining the losses, both the parasitic elements of the cell and the MOSFETs play a decisive role. In order to optimize the losses, an in-depth analysis of the switching process and an optimal design of the circuit are therefore necessary.
 

The analysis on system level regarding the interconnection of the cells as well as the control of all integrated semiconductor elements is a research focus in the research group. In addition to the hardware, the control method of the power switches also has a significant influence on the shape and quality of the output voltage. Ideally, the output variable has a perfect sinusoidal shape in order to maximize the efficiency of the electric motor.
Corresponding control methods, also called modulation methods, are basically divided into methods based on low-frequency and high-frequency modulation, whereby these can also be further subdivided in many ways. Common control methods are, for example, pulse width modulation (PWM) or space vector modulation.

The analysis of such common as well as numerous other methods represents another research area of the ELS research group in the field of power electronics. New semiconductor materials (SiC, GaN) offer additional degrees of freedom (e.g. higher switching frequency). Furthermore, the practical implementation of innovative modulation techniques becomes possible.
The ELS research group therefore develops power electronics for novel multilevel converter topologies using the latest semiconductor technologies and evaluates them with respect to their efficiency.