Date: Jun 11, 2012 Source: United Silicon Carbide (
click here to go to the source)
United Silicon Carbide Inc. based in Monmouth Junction, NJ, USA has been awarded a Department of Energy grant for the development of the industry's first commercial SiC 6.5KV JFET in order to revolutionize traditional storage grid tied 2 level inverter systems commonly found in energy storage applications.
USCi will fabricate half-bridge switch modules that are rated at 6.5 kV, thus enabling DC-Link voltages up to ~5 kV, and adopting a unipolar normally off SiC-JFET approach allows the device to switch in the medium voltage range while maintaining low switching losses and switching speeds of 20-30KHz.
Traditional DC link and 2 level inverter systems for grid tied storage use 1.2 kV Si-IGBT switch modules operating at 6.5 kHz. These low voltage, low performance silicon switches require that the system runs with high current levels and relatively low frequencies (< 10 kHz) thus requiring thick cables, heavy transformers, costly magnetics and elaborate cooling schemes to keep the IGBTs in a safe temperature range. In an attempt to address this issue, Si-IGBT's can achieve higher voltages, up to 6.5 kV, but at the expense of switching speed which must be reduced to sub kHz levels. System designers choose the best operating range for a particular system but are limited by the selection of silicon based devices.
"All large area silicon based switches like Insulated Gate Bipolar Transistors (IGBT), Gate-Turn-Off (GTO) Thyristors and Gate-Commutated-Thyristors (GCT's) function but show significant disadvantages and limitations in use like restricting switching frequencies to sub KHz or demanding implementation of costly turn off snubbering. United Silicon Carbide will solve these problems using its expertise in SiC based Junction Field Effect Transistors (JFETs) to develop a switch module product that can readily improve the needs of current state-of-the art energy storage systems and create a switch platform for next generation systems as well. A 6.5 kV, 60 A switch module operating at 20-30 kHz will provide significant system level performance benefits that enable simpler adoption and faster penetration of wind and solar generation seamlessly into distributed storage based power systems operating in the 100 kW to 1 MW range".
