Design and Assembly of a Low-Parasitic-Capacitance Medium-Frequency Medium-Voltage Transformer

With the development of renewable energy, direct current (DC) solutions show cost-benefit advantages over alternating current solutions. Within DC systems, the isolated DCDC converters play a key role in connecting different voltage-level DC buses. To construct more compact and efficient DC-DC converters, higher switching frequency and switching speed are enabled by wide-bandgap devices. However, as the system voltage level increase, the higher voltage leads to more electrical field energy being stored in parasitic capacitors instead of parasitic inductors. This introduces challenges related to parasitic capacitance in transformers. This paper provides design and assembly considerations for a low-parasitic-capacitance medium-frequency medium-voltage transformer specifically tailored for a 6 kV / 600 V DC-DC converter. The measurement results align closely with the finite element analysis, revealing that the primary-side capacitor measures 13.1 pF, while the primary-to-secondary capacitor is 34.1 pF. Furthermore, a 6 kV - 600 V high-voltage-gain resonant DC-DC converter is constructed, demonstrating robust performance of the transformer.