IEEE Electrification Magazine - March 2016 - 23

There are various criteria for classifying microgrids such as size, connectivity (off-grid or grid-connected), economics, and social context.
For practical applications, microgrids are categorized
into: 1) off-grid and 2) grid-connected. The off-grid
installations are mainly exploited for electrification in
remote areas. The grid-connected microgrids, which are
primarily the ones discussed in this article, are classified into four groups.
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Campus microgrids are built for enhancing resilience,
reducing energy costs, and mitigating carbon emissions at universities, industrial parks, factories, hospitals, and other large urban energy consumers. Furthermore, they open up great opportunities for academic research projects.
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Military microgrids are deployed with an emphasis on
enhancing physical and cybersecurity for military
facilities, which could guarantee a continuous supply
of power without relying on the main grid supply.
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Community microgrids include a larger segment of the
traditional grid. Their main distinguishing feature is to
supply residential customers. This type of microgrid
provides an alternative for grid operation, attaining a
more sustainable, reliable, and economical energy system while generally yielding long-term backup supply
for critical loads. In recent years, community
microgrids have attracted more attention in various
locations throughout the world.
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Onboard microgrids are associated with electrification
grids on board plug-in electric vehicles (PEVs), trains,
planes, and ships. More recently, this group of
microgrids has attracted the attention of ship owners
and ports as a result of prohibiting ships from using
bunker fuel to run onboard diesel engines by environmental protection agencies. The deployment of the
next generation of PEV microgrids, which includes
plug-in hybrid electric vehicles and electric vehicles
with vehicle-to-grid capability, seems to be a viable
solution to certain environmental and economic concerns in the power industry. PEVs are rapidly developing and penetrating the transportation system. In September 2014, the governor of California set a goal of
placing at least one million zero-emissions vehicles
and near-zero-emissions vehicles on the road in California by 1 January 2023.

A distribution grid can be composed of several microgrids, creating
a multi-microgrid structure, as
shown in Figure 6. The synergy of
multi-microgrids presents a golden
opportunity for improving the resilience of the power grid. In this way,
the potential benefits of microgrids
would be realized to an even larger
extent. In a multi-microgrid environment, individual microgrid deficiencies can often be overcome by other
local microgrids in cooperation with
the utility grid. Likewise, the distribution management system in a multi-microgrid structure
can receive control signals from the master controller of
the individual microgrid, analyze the data, perform optimization, and send associated signals back to the individual microgrids.

a Greater role for Microgrids
Modern societies are often developed based on interdependent infrastructures such as electricity, communication, transportation, natural gas, and water, as depicted in
Figure 7. The interdependency and the potential for cascading outages can lead to numerous supply problems in
such infrastructures. The advent of microgrids, however,
can provide numerous opportunities for the coordination
of interdependent infrastructures, thereby rendering them

Oil and Gas

Electric Grid

Communication

Microgrid categories

A microgrid can
be considered an
energy hub where
different energy
carriers are
installed, converted,
and conditioned.

Transportation

for the future projects. Microgrids will
continue to benefit from technological advancements. However, one
should conduct more studies on
microgrids to tackle the additional
merits of such installations and the
impacts of technological developments that are yet to be discovered.

Water

Figure 7. Basic infrastructures and their interdependence.

IEEE Electrific ation Magazine / March 2 0 1 6

Table of Contents for the Digital Edition of IEEE Electrification Magazine - March 2016