A 10 kV SiC MOSFET based Three-Phase Single-Stage Isolated MVAC/LVDC Converter for Solid State Transformer Applications

Due to the recent strides in developing medium voltage 10 kV Silicon Carbide (SiC) based MOSFETs, it has become possible to design MV systems without complicated multilevel converter topologies. Using these devices opens up a lot of potential to reduce the system size and complexity while preserving high efficiency. Solid-state transformer (SST) applications have recently gained a lot of traction due to the rise of artificial intelligence which fuels the demand for data centers. The realization of these SSTs using a direct single-stage AC/DC power conversion architecture is lucrative due to its low cost and component count. In this paper, a single-stage, isolated AC/DC converter using 10 kV SiC MOSFETs, connected to a 4.16 kV grid, is introduced. The topology combines the power factor correction (PFC) stage and the DC/DC stage which enables the conversion using only a single 10 kV half-bridge module. Further, the MV inductors operate in discontinuous conduction mode (DCM) which results in a simple open loop control for the switches. This single-stage converter uses a single medium voltage transformer which streamlines the complexity and reduces the system cost. An experimental hardware is built and tested up to 5 kV DC link voltage and a maximum power of 20 kW. A peak efficiency of 98.4% is observed for the laboratory prototype.