IEEE Electrification Magazine - March 2014 - 5

that despite the numerous advantages of using microgrids, there are
technical challenges regarding the
control and protection of microgrids.
one of the prominent challenges in
microgrid operation is the design of a
proper protection scheme for microgrids. the integration of distributed energy resources (Ders) and novel
topologies embedded in microgrids
would challenge the characteristics
of protection schemes in microgrids
as compared to those of conventional
distribution systems. the conventional protection strategies in distribution systems rely on the radial
topology of distribution networks
with the supply located at one end.
in this configuration, the fault current is provided by the utility grid
with protective device (PD) settings
adjusted accordingly to localize the
impact of faults. PDs are coordinated
based on unidirectional power flows
from the feeder toward loads
in radial distribution networks, in
which fault currents would be lower
as fault locations get farther from
feeders. however, these unidirectional
characteristics change in microgrids.
the Der units located in microgrids
can increase fault currents, change
fault current flow paths, result in bidirectional power flows, and affect PD
operations. the inclusion of Der units
with power electronic interfaces, such
as converters, would limit fault currents and desensitize PDs to faults especially in island mode. the large
difference between fault currents in
grid-connected and island modes
presents new challenges in microgrid
fault protections. Moreover, the microgrid topology can be looped,
meshed, or mixed networks, which
could result in more complex fault
current paths and affect protection

strategies in microgrids. the authors
business processes and to enable efficonclude the article with several excient functioning of the deregulated
amples of a practical microgrid.
energy market for the benefit of conthe seventh article by Dimeas et al.
sumers and businesses.
discusses the smarthouse project in
Finally, in the "Viewpoint" column,
the european union (eu). the authors
Chiesa and Zirkelbach argue that mipoint out that the infrastructure that
crogrids help utilities more than they
will exist in the future smart houses is
hurt. they point out that microgrids
expected to be highly heterogeneous.
are not coming; they are already here.
however, it seems that, at some level,
From the innovations that created
all devices-either by
Pearl street to the
themselves or via gatetransformations that
Many of the microgrids
ways-will be able to
are driving the grid
in the northeast that
communicate over the
innovations today,
internet protocol and
microgrids are here
continued to operate
participate in bidirecto stay and reprethrough Sandy and
tional collaboration
sent a new business
its aftermath were built
with other devices and
model for both confor cost-saving reasons. sumers and utilities.
enterprise services.
similarly, multiple
the past is littered
concepts for monitorwith old business
ing and controlling the smart houses
models, such as pay phones, and the
and the smart grid will emerge, with
companies that survived the introducdifferent optimization and control
tion of disruptive technologies are the
algorithms. it is therefore imperative
ones that adapted and changed their
not to focus on a single one-size-fits-all
business models appropriately, such as
approach but to prove that an amalgaat&t and Verizon. therefore, utilities
mation of the existing approaches
and customers need to continue to
should be developed. the smarthouse/
work together to find ways to adapt
smartgrid project in the eu can be
the old grid models to the new smarter
seen as the first step to developing
grid realities.
mechanisms for "gluing" different
In the End
monitoring and control approaches as
we believe that it is important to
well as empowering the next-generaunderstand the end game. are
tion enterprise services and applicamicrogrids a silver bullet for the industions. the authors point out that
try, replacing central-station generainnovative technologies and concepts
tion and the grid? no. there are many
will emerge as power systems shift
reasons for a vibrant, cost-effective
toward a more dynamic, service-based,
grid and large-scale generation busimarket-driven infrastructure where
ness. But, over time, microgrids will
energy efficiency and savings can be
become a mature tool in the toolbox of
facilitated by interactive distribution
cost-effective, reliable, resilient, and
networks. a new generation of fully
sustainable electric system design...
interactive information and communiand that is exciting!
cation technologies infrastructure has
to be developed to support the optimal
exploitation of the changing, complex

IEEE Electrific ation Magazine / MARCH 2 0 1 4

Table of Contents for the Digital Edition of IEEE Electrification Magazine - March 2014