DC/DC Converters for HVDC Grids

The variability of renewable energy sources, often located offshore or in remote regions, requires a grid that can handle large power variations over large distances. If our society is to exploit as much renewable energy as possible, high-voltage direct current (HVDC) grids will be necessary. This grid will have different voltage levels as its various parts are interconnected over time. To control power flows between the voltage levels DC/DC converters will be required. However, at the gigawatt scale, these converters face strict size and cost constraints.

This seminar investigates a DC/DC converter topology based on a modular multilevel converter (MMC) architecture and examines how operating frequency and semiconductor technology influence total losses and converter volume. The analysis combines analytical transformer models, validated through finite-element simulations, with detailed loss calculations for both silicon (Si) insulated-gate bipolar transistors (IGBTs) and silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs), evaluated across multiple die-area variants. The results provide quantitative design guidelines for developing compact and efficient DC/DC converters for future HVDC grids.