SiC-BASED POWER CONVERTERS

The advantages that silicon carbide (SiC) based power electronic devices offer are being realized by using prototype or experimental devices in many different power applications ranging from medium voltage to high voltage or for high temperature or high switching frequency applications. The main advantages of using SiC-based devices are reduced thermal management requirements and smaller passive components which result in higher power density. An overview of the SiC research effort at Oak Ridge National Laboratory (ORNL) and The University of Tennessee (UT) is presented in this paper. INTRODUCTION Silicon carbide power electronic devices are expected to have better characteristics than their silicon counterparts once processing and packaging issues have been solved. SiC devices have higher blocking voltages, lower on-state resistance and switching losses, and higher thermal conductivity and operating temperatures. Use of these devices will impact several application areas including hybrid electric vehicles, electric grid interface with distributed energy sources, and high temperature environments. In pursuit of mass production of hybrid electric vehicles, the automotive research industry has set goals such as reducing the size and weight of the power electronics and cooling systems and increasing their efficiency. The U.S. Department of Energy's research goals for the year 2020 include hybrid electric vehicle inverters that have power densities of more than 14.1 kW/kg and 13.4 kW/L, and efficiencies greater than 98 % at a cost less than $3.3/kW. SiC devices are capable of operating at higher voltages, higher frequencies, and higher junction temperatures than comparable Si devices, which result in significant reduction in weight and size of the power converter and an increase in system efficiency. The objectives of research efforts on SiC based device applications at ORNL and UT are • Assessing the impact of replacing silicon (Si) power devices in transportation applications such as hybrid electric vehicles (HEVs) or plug-in hybrid electric vehicles (PHEVs) with wide-bandgap (WBG) semiconductors, especially silicon carbide (SiC). Researchers have also examined what impact high voltage SiC devices would have in power electronics for electric utility applications. • Developing temperature-dependent device and power converter models for various system simulation studies and analyzing the impact of SiC devices on the system performance. • Building SiC-based prototype converters to validate the performance of SiC devices. • Building high temperature packages and gate drives for SiC power devices to operate at 200°C ambient.