A highly efficient DC-DC-converter for medium-voltage applications

In the electrical energy distribution network of the future, power electronics will become more and more important. Especially the expansion of renewable energies such as photovoltaic and wind requires a rising number of converters between generator and consumer of electrical energy. With the use of silicon carbide (SiC) high voltage power semiconductor devices it will be possible to build highly efficient converters, which can feed directly into the medium voltage grid. An increase of the voltage level will reduce the current and thereby the copper cross sections but also the coupling with a 50/60-Hz transformer can be omitted. The potential of these devices is shown in this paper by the presentation of a 28 kW DC-DC-Converter with 10 kV / 10 A SiC MOSFETs. With an input voltage of 3.5 kV and an output voltage of 8.5 kV the converter reaches an efficiency of 98.5 % with a switching frequency of 8 kHz.