Recently, medium voltage SiC devices have been developed which can be used for grid tie applications at medium voltage. Two such devices -15 kV SiC IGBT and 10 kV SiC MOSFET have opened up the possibility of looking into different converter topologies for medium voltage distribution grid interface. These can be used in medium voltage drives, active filter applications or as the active front end converter for Solid State Transformers (SST). Transformer-less Intelligent Power Substation (TIPS) is one such application for these devices. TIPS is proposed as a 3-phase SST interconnecting 13.8 kV distribution grid with 480 V utility grid. The Front End Converter (FEC) of TIPS is made up of 15 kV SiC IGBTs.This paper focuses on the advantages, design considerations and challenges associated with the operation of converters using these devices keeping TIPS as the topology of reference.

Due to wider band gap of Silicon Carbide (SiC) compared to Silicon (Si), MOSFET made in SiC has considerably lower drift region resistance, which is a significant resistive component in high-voltage power devices. With low on-state resistance and its inherently low switching loss, SiC MOSFETs can offer much improved efficiency and compact size for the converter compared to those using Si devices. In this paper, we report switching performance of a new 1700V, 50A SiC MOSFET designed and developed by Cree, Inc. Hard-switching losses of the SiC MOSFETs with different circuit parameters and operating conditions are measured and compared with the 1700V Si BiMOSFET and 1700 Si IGBTs, using same test setup. Based on switching and conduction losses, the operating boundary of output power and switching frequency of each device are found out in a DC-DC boost converter and compared. The switching / and / of SiC MOSFET are captured and discussed in perspective of converter design. To validate the continuous operation, three DC-DC boost converters using these devices, are designed and tested at 10kW of power with 1kV of output voltage and 10kHz of switching frequency. 1700V SiC Schottky diode is used as the blocking diode in each case. Corresponding converter efficiencies are evaluated and the junction temperature of each device is estimated. To demonstrate high switching frequency operation, the SiC MOSFET is switched upto 150kHz within permissible junction temperature rise. A switch combination of the 1700V SiC MOSFET and 1700V SiC Schottky diode connected in series is also evaluated for zero voltage switching (ZVS) turn-ON behavior and compared with those of bipolar Si devices. Results show substantial power loss saving with the use of SiC MOSFET. Index Terms-1700V SiC MOSFET, 1700V Si IGBT, 1700V Si BiMOSFET, switching characterization, switching losses, converter efficiency, zero voltage switching (ZVS) turn-ON.

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Sialic acids are a ubiquitous family of negatively charged sugar molecules found on the surfaces of mammalian cells, usually at the termini of glycans attached to glycoproteins, glycosphingolipids, and the proteoglycan keratan sulfate (2, 10, 72). Sialic acid is an essential component of cell surface receptors for a variety of microorganisms and microbial toxins (2,34,47). Members of at least eight different virus families-Ortho-

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