This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE TRANSACTIONS ON ELECTRON DEVICES 1 Wide-Bandgap Solid-State Circuit Breakers for DC Power Systems: Device and Circuit Considerations Z. John Shen, Fellow, IEEE , Gourab Sabui, Student Member, IEEE, Zhenyu Miao, Student Member, IEEE, and Zhikang Shuai, Member, IEEE (Invited Paper) Abstract—DC circuit protection applications provide a unique market opportunity for wide-bandgap (WBG) semiconductors, which are outside the conventional focus on power electronic converters. This paper presents an overview of emerging dc power systems, the needs for dc solid-state circuit breakers (SSCBs), and the benefits and advantages of various WBG SSCB concepts. Furthermore, a new class of self-powered SSCBs based on SiC or GaN normally-ON switching devices is pro- posed in this paper. One implementation of the SSCB concept based on a 1200 V SiC JFET experimentally demonstrated turn-off of a fault current of 125 A at a dc voltage of 400 V within 1 μs without requiring any external power supply. The SSCB detects short-circuit faults by sensing its drain–source voltage rise and draws power from the fault condition to turn off the SiC JFET. Various implementations of the SSCB concept for unipolar and bipolar capability using both SiC and GaN are also discussed from both device and circuit perspectives. It is concluded that very low ON-resistance normally-ON WBG switching devices are excellent candidates for the emerging SSCB applications. Index Terms— GaN HEMT, SiC JFET, solid-state circuit breaker (SSCB), wide-bandgap (WBG) semiconductors. I. I NTRODUCTION W IDE-BANDGAP (WBG) semiconductors such as SiC and GaN have recently emerged as ideal materials for switching devices in high-voltage, high-frequency, and high-power applications. Although WBG semiconductors offer significant improvement over silicon in power efficiency, switching frequency, and operating temperature, their prolifer- ation into the mainstream power electronic market is impeded by high device cost and reliability concerns. This is mainly because the WBG technology itself is still evolving toward its maturity. But, in many cases, it is also because WBG devices are being used simply as a drop-in silicon replacement in Manuscript received July 6, 2014; revised September 26, 2014 and October 24, 2014; accepted October 29, 2014. This work was supported by the U.S. National Science Foundation under Grant EECS-1407540. The work of Z. Shuai was supported by the National High Technology Research and Development of China under Project 2014AA052601. The review of this paper was arranged by Editor N. Ohtani. J. Z. Shen, G. Sabui, and Z. Miao are with the Illinois Institute of Technology, Chicago, IL 60616 USA (e-mail: johnshen@ieee.org; gourab.sabui@gmail.com; zmiao3@hawk.iit.edu). Z. Shuai was with Hunan University, Changsha 410082, China. He is now with the Illinois Institute of Technology, Chicago, IL 60616 USA (e-mail: shuaizhikang-001@163.com). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TED.2014.2384204 power converters that have been optimized for silicon devices over decades. WBG devices are often forced to imitate and then compete against lower cost silicon devices instead of fully capitalizing on their own unique characteristics. While efforts will be made to further improve the cost effective- ness of WBG devices for the mainstream power converter applications, it may be useful to investigate other unique potential killer applications where silicon is simply no longer an option. In this regard, dc circuit protection indeed represents a unique market opportunity for WBG power devices that fully leverages what WBG materials can offer. AC won over dc over 100 years ago as the dominant form of electricity due to the fact that simple ac transformers can step up and down voltages to facilitate power transmission over a long distance. However, recent changes in both electric loads and renewable generation sources make electrical engineers reconsider dc as a viable alternative to improve efficiency and reliability of electricity in both distribution and transmission domains for good reasons [1]–[6]. One of the major technical obstacles in adopting dc power is the lack of reliable dc circuit breakers to protect against short-circuit faults [7]–[10]. Conventional mechanical ac circuit breakers are too slow and prone to arcing damage for dc power systems. Several silicon-based solid-state circuit breaker (SSCB) concepts were investigated in the past, but left a large gap in meeting the performance and cost requirements. SSCB concepts based on SiC devices were also proposed recently, showing a great promise. This paper provides an overview of emerging dc power systems, the need for dc SSCBs, and the benefits and advantages of various WBG SSCB concepts. Furthermore, the authors propose a new class of self-powered SSCBs based on SiC or GaN normally- ON switching devices with a very low conduction loss and fast reaction time without using any auxiliary power sources. II. EMERGENCE OF DC POWER SYSTEMS DC power systems can be adopted at both low to medium voltage distribution level (24–30,000 V) and high voltage transmission level (hundreds of kilovolts). A. DC Power Distribution At the distribution level, electric power system resources and their controls are becoming increasingly distributed in nature to accommodate renewable and other distributed gen- eration resources, leading to the concept of microgrids [7]. 0018-9383 © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.