Powering the future with smarter megawatt chargers
Kaveh Pouresmaeil defended his PhD thesis at the Department of Electrical Engineering on June 30th.
Transport is one of the largest contributors to CO₂ emissions in Europe, and heavy-duty vehicles play an outsized role in this. Although they represent only 2% of all vehicles on the road, they are responsible for over 25% of road transport emissions. To meet climate targets, transitioning these vehicles—such as diesel trucks—to electric alternatives is essential. This research of Kaveh Pouresmaeil contributes to that transition by enabling the development of more compact, efficient, and reliable megawatt charging systems through the integration of a modular multilevel converter with a medium-frequency transformer.
Electrifying heavy-duty vehicles requires megawatt charging systems (MCS). These powerful chargers must deliver extremely high currents and voltages in a short time, which demands direct connection to the medium-voltage grid. For widespread adoption, these systems must not only be powerful, but also cost-effective, efficient, and reliable.
Transforming charger design
Within his research Kaveh Pouresmaeil focuses on improving the design of megawatt chargers. Traditional systems rely on bulky low-frequency transformers, with a significant share of the cost coming from the copper used in the windings. Copper is becoming more expensive and harder to source. To address this, a key innovation in this work is the use of a medium-frequency transformer in combination with a modular multilevel converter (MMC). This architecture reduces transformer size and lowers material cost by operating at higher frequencies.
Innovative control and modulation strategies
To enable efficient operation at higher frequencies, the research introduces several new control methods and modulation strategies. One major contribution is a soft-switching technique that reduces power losses and allows for the use of more affordable semiconductor components. Other techniques improve waveform quality, balancing the trade-offs between harmonic distortion and efficiency—critical for high-performance charging.
Enhancing system reliability
Beyond performance and cost, reliability is vital. This work proposes a low-cost and effective method to detect and eliminate DC bias in the transformer. DC bias can lead to core saturation and eventual system failure, making its mitigation essential for long-term stability and safety of the charger.
Validated through simulation and prototyping
All proposed solutions were validated through detailed simulations and confirmed using laboratory prototypes. The results show that it is feasible to build megawatt charging systems that are smaller, more efficient, and less dependent on scarce materials such as copper.
A step toward scalable electric transport
This research contributes to the development of next-generation megawatt chargers that are compact, cost-effective, and reliable. These innovations are not only crucial for electric trucks but also support broader applications, including electric ferries and other large-scale transport systems. By solving key technical challenges, this work lays the foundation for the accelerated rollout of sustainable high-power charging infrastructure for the future of electric mobility.
The research is part of the NEON research project. For more information: . Funding by NWO.
Title of PhD thesis: . Supervisors: Prof. George Papafotiou, Dr. Maurice Roes, and Dr. Nico Baars.