Revolutionary Solid State Circuit Breaker Based on 15kV SiC Power Device

Achievement date: 
2014
Outcome/accomplishment: 

The Future Renewable Electric Energy Delivery and Management Systems Center (FREEDM) – a National Science Foundation (NSF) Engineering Research Center (ERC) based at NC State University – and its industry member, Cree Inc., introduced a new solid-state circuit breaker (Gen-II FID).  A single, silicon carbide emitter turn-off thyristor (SiC ETO) achieves high voltage and high current handling capability in the new design. It is therefore much smaller (by 20%) and has much lower losses (50% lower) when compared to the Gen-I FID.

Impact/benefits: 

For a FREEDM system and future smart grid, the speed of fault isolation is as important as fault detection itself. The voltage profile can remain deteriorated for prolonged periods of time due to limited fault currents in the system. Without a fast fault isolation device, there is potential for low power quality or system failure. The newly developed Gen-II FID is able to interrupt the fault current in less than 100 microseconds, as compared to 100 milliseconds in conventional breakers. This can significantly reduce the time over which the voltage is distorted, thus increasing the power quality and reducing equipment stress.

Explanation/Background: 

The newly developed FID demonstrates the close collaboration between power electronics research, solid-state research, and power system research groups in the ERC, as well as with its member company, Cree, Inc.

In a power system like FREEDM’s with high penetration of distributed generation (DG) units, power quality plays a very important rule in operation of the system. A disturbance in the system can cause the distributed-generation units to interact with each other in a resonant way, eventually causing them to fail. In this manner, if not isolated promptly, a very distant fault can cause catastrophic system failure.

Using this novel FID technology, which takes advantage of high-speed solid-state switches, any disturbance in the system can be isolated with unprecedented speed. The high voltage handling capability of the new technology is achieved through the application of SiC material, which makes it possible to reach the breakdown voltages of up to 15kV while keeping the conduction loss at a low level.