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Medium-Voltage AC to 400 V DC Rectifier For Data Center

Circuit schematics
Fig. 1. Proposed medium voltage to 400 VDC PCSB for DC data center.
Due to increasing use of cloud computing and big data, datacenter power consumption is expected to reach 10 percent of the global electrical power consumption by 2020. In conventional ac datacenter power architectures, a line-frequency transformer is employed to step down a medium-voltage ac to 480 V ac, which leads to a bulky and costly transmission bus and large conduction losses. This line-frequency transformer is cascaded by a 480 V uninterruptible power supply and rectified into 400 V dc. In this work, a SiC- and GaN-based rectifier with high-frequency, medium-voltage solid-state transformer is proposed to directly step down medium-voltage ac to 400 V dc. The dc-dc stage is the key point for this work because of its medium-voltage insulation capability. A CLLC Resonant converter is utilized with SiC and GaN devices to achieve high efficiency, high power density and bidirection operation. The high-frequency transformer in the CLLC converter is well-designed for 30 kV insulation capability for a 4.8 kV input voltage, in reference to IEEE standards. A shielding layer is implemented to reduce the electric field stress in the air. In addition, magnetizing inductance and two resonant inductances are integrated with the transformer in order to subtract volume.
CLLC Converter Hardware
Fig. 2. 500 kHz 15 kW CLLC resonant converter prototype hardware.