Optimizing three-phase DC-DC converters for MVDC grids; 1. Auflage

RWTH Publications (RWTH Aachen)

Abstract

The transition towards a sustainable energy system requires both renewable expansion and grid development. DC technology offers advantages over AC, including lower losses and reduced material demand. While HVDC is established, LVDC systems are increasingly used in decentralized grids and are expected to be connected to MVDC systems. However, suitable MVDC voltage levels are not yet defined. In MVDC distribution grids, converter efficiency and material usage are more relevant than transmission losses. Modular, galvanically isolated converters provide flexibility, especially in MFT design. This work develops a holistic modeling framework linking MVDC voltage, efficiency, and material requirements. Analytical MFT models are extended by including insulation constraints, enabling evaluation of interactions between switching frequency, transformer and semiconductor losses, and system voltage. The goal is to determine optimal MVDC voltage levels. An analytical modeling approach for MFTs in three-phase DAB converters is developed, enabling combined evaluation of efficiency and material usage. A key contribution is the integration of insulation, thermal constraints, and stray inductance. Designs are experimentally validated, and scalable material models are derived. DAB converters in ISOP configuration are analyzed, identifying Pareto-optimal designs across power and voltage ranges, considering semiconductor technologies. Finally, cost models and system-level AC comparisons enable identification of optimal designs and economic operating conditions.

Authors 1

1. Katharina Sophie Hetzenecker corresponding Aachen

   RWTH Aachen University

   Affiliation as printed

   RWTH Aachen