Mixed MOSFET-IGBT Bridge for High-Efficient Medium-Frequency Dual-Active-Bridge Converter in Solid State Transformers

High power DC-DC conversion is a key element within the Solid-State-Transformer concept. In order to reduce the switching losses of the Medium-Voltage side semiconductors, a Triangular-Current-Mode modulation scheme presents an attractive option. This modulation scheme, however introduces considerable challenges in the design of the low-voltage side power electronic bridges, which need to deal with high conducted and high switched currents. In order to increase the converter's efficiency, a combination of IGBTs and MOSFETs in a full-bridge configuration is considered. Practical hardware realizations are utilized in order to quantify the improvements introduced by the combination of these switches. Furthermore, the MOSFET's current conduction phase is supported by parallel connected IGBTs, which are used in order to further increase the full-bridge's efficiency, as shown by the provided experimental verification.