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This article identifies and validates the use of ultrafast silicon carbide (SiC) junction field effect transistor (JFET)-based self-powered solid-state circuit breakers (SSCBs) as the enabling protective device for a 340 Vdc residential dc community microgrid. These SSCBs will be incorporated into a radial distribution system in order to enhance fault discrimination through autonomous operation. Because of the nature and characteristics of short-circuit fault inception in dc microgrids, the time–current trip characteristics of protective devices must be several orders of magnitude faster than conventional circuit breakers. The proposed SSCBs detect short-circuit faults by sensing the sudden voltage rise between its two power terminals and draw power from the fault condition itself to turn off SiC JFETs and then, coordinate with no-load contacts that can isolate the fault. Depending upon the location of the SSCBs in the microgrid, either unidirectional or bidirectional implementations are incorporated. Cascaded SSCBs are tuned using a simple resistor change to enable fault discrimination between upstream high-current feeds and downstream lower current branches. Operation of one of the SSCBs and three in cascaded arrangements are validated both in simulation and with a hardware test platform. Thermal impact on the SSCB is discussed as well. The target application is a residential dc microgrid that will be installed as part of a revitalization effort of an inner city Milwaukee neighborhood. [ABSTRACT FROM AUTHOR]

The availability of fossil fuels in the future and the environmental effects such as the carbon footprint of the existing methodologies to produce electricity is an increasing area of concern. In rural areas of under-developed parts of the world, the problem is lack of access to electrification. DC microgrids have become a proven solution to electrification in these areas with demonstrated exceptional quality of power, high reliability, efficiency, and simplified integration between renewable energy sources (principally solar PV) and energy storage. In the United States, a different problem occurs that can be addressed with the same DC microgrid approach that is finding success internationally. In disinvested, underserved communities of with high unemployment and low wages, households contribute a significant portion of their income toward the fixed cost of their electrical utility connection, which by law must be supplied to every household. This paper analyzes a residential DC microgrid in an urban, underserved area that enables the sharing of renewable and stored energy resources between dwellings. The goal of the residential DC microgrid is to drive down to fixed costs of utility-provided electricity to all participants, such that the percentage of utility cost to total household income comes can be made comparable to that of more advantaged communities. A group of renovated dwellings constitute the community which the DC microgrid would serve. The distributed installation of solar panels and battery storage among dwelling locations are optimized based upon varying consumption patterns. Also, consumption patterns during different seasons of the year are considered. Electrical distribution architectures within the dwellings are based upon conventional AC. Each dwelling has a DC interface to the residential microgrid and progressive insertion of DC loads, with associated household DC distribution, is considered. [ABSTRACT FROM AUTHOR]

Fault current limiters (FCLs) are one of the main solutions to upcoming challenges in the microgrid protection. Regarding the high penetration of distributed generations (DGs) in the future power system, designing cheap and effective FCLs is a necessity. This letter addresses this issue by proposing an embedded FCL operating based on modifying the secondary control of the inverter. As this method is presented for a four-wire system, besides very low implementing cost, it has independency and flexibility to only limit the current of the DG faulted phase. This letter also provides real-time simulation results by real time simulator (OPAL-RT) to compare the proposed method with a virtual-impedance-based FCL to validate its effectiveness. Finally, experimental results are presented to validate the effectiveness of the proposed FCL. [ABSTRACT FROM AUTHOR]

Microgrid, which is one of the main foundations of the future grid, inherits many properties of the smart grid such as, self-healing capability, real-time monitoring, advanced two-way communication systems, low voltage ride through capability of distributed generator (DG) units, and high penetration of DGs. These substantial changes in properties and capabilities of the future grid result in significant protection challenges such as bidirectional fault current, various levels of fault current under different operating conditions, necessity of standards for automation system, cyber security issues, as well as, designing an appropriate grounding system, fast fault detection/location method, the need for an efficient circuit breaker for DC microgrids. Due to these new challenges in microgrid protection, the conventional protection strategies have to be either modified or substituted with new ones. This study aims to provide a comprehensive review of the protection challenges in AC and DC microgrids and available solutions to deal with them. Future trends in microgrid protection are also briefly discussed. [ABSTRACT FROM AUTHOR]