IEEE Network - March / April 2017 - page 16

IEEE Network • March/April 2017
0890-8044/17/$25.00 © 2017 IEEE
In this article, we investigate the plug-in elec-
tric vehicle (PEV) integrated smart grid for effi-
cient system operation. Due to the stochastic
characteristics of PEVs, the intermittent nature of
renewable energy sources, and the heterogeneity
of the devices, it is a great challenge to achieve
system flexibility, reliability, and interoperability.
To address these issues, we propose a two-tier
SDN-based framework for the PEV integrated
smart grid. The upper tier targets the primary
feeder level to have a general view of the system,
while the lower tier focuses on the secondary
feeder level to achieve granular control of data
and power operation. The framework is presented
hierarchically, followed by a detailed explanation
of the system operation in each tier. In particular,
the integration of PEVs, which includes both PEV
charging and V2G, is well illustrated in the SDN-
based framework. Finally, we provide a case study
to validate the emerging need for SDN deploy-
ment in the smart grid.
In the past decade, plug-in electric vehicles (PEVs)
have received worldwide attention owing to their
environmental and technical advantages when
compared with the conventional petroleum-con-
suming vehicles. From the environmental per-
spective, PEVs have more electricity generation
options (e.g. hydro, wind, and solar) rather than
fossil fuels. The various electricity generation
options help reduce the reliance on fossil fuels
in the transportation sector. From the technical
perspective, PEVs can achieve a high propulsion
conversion efficiency of 90 percent, while con-
ventional petroleum-consuming vehicles have
an efficiency of only 45 percent [1]. With both
environmental and technical advantages that
PEVs bring to the transportation sector, govern-
ments have launched a large number of laws and
research projects worldwide to accelerate the
commercialization of PEVs [2].
As the PEV penetration rate increases in the
next decades, the frequent interactions between
the smart grid and PEVs require a thorough study
to improve the reliability, sustainability, and effi-
ciency of the system [3]. Compared with the
traditional power grid, the PEV integrated smart
grid has four main features. First, the integration
of PEVs remarkably increases the system energy
storage capacity through vehicle-to-grid (V2G)
technology. Second, the smart grid incorporates a
high percentage of renewable energy source-dis-
tributed generations (RES-DGs) to enhance sys-
tem sustainability. Third, the Internet of Things
(IoT) technique is adopted to guarantee system
connectivity and automation. Finally, the smart
grid enables bidirectional power and data com-
munication to improve the reliability and efficien-
cy of the system.
However, by integrating PEVs and RES-DGs
into the power grid, the smart grid faces many
challenges from both power and communication
perspectives. In terms of the power challenges,
the stochastic properties of PEVs can severely
jeopardize the system reliability [4]. When a large
number of PEVs are in charging mode, the simul-
taneous charging of PEVs in the residential area
may severely damage the system components
(e.g. transformers) [5]. On the other hand, the
random driving patterns of PEVs may cause fail-
ures to accomplish V2G service timely, which can
decrease the system reliability or even result in
blackouts. In addition, the intermittent nature of
RES-DGs can cause load imbalance in extreme
weather conditions, jeopardizing the system reli-
ability. In terms of communication challenges, as
the PEV penetration rate rises, the number of IoT
devices is rapidly increasing in the smart grid, which
has a significant influence on the system scalability
[6, 7]. Moreover, heterogeneous connected devices
(e.g. PEVs, RES-DGs, etc.) require significant manual
effort for device configuration and maintenance,
which is a huge economic cost [6].
To address the above challenges, many coordi-
nation schemes have been proposed in previous
studies. For example, the authors in [8] implement
an advanced version of the ISO 15118 commu-
nication protocol to enable the flexible integra-
tion of PEVs into the home energy system. The
authors in [9] define an information model based
on IEC 61850-7-420 to guarantee the control of
PEV integration into the smart grid. A similar net-
work implementation is reported in [10] based
on IEEE 802.16 for V2G technology. However,
the above works have only implemented network
functions based on a specific communication pro-
tocol, which is not flexible and scalable for the
heterogeneous scenarios in the smart grid.
As a promising paradigm, software-defined net-
works (SDNs) have the potential to improve the
flexibility, scalability, and interoperability of the
smart grid. SDN refers to a network architecture
that separates the control logic from the underly-
ing data forwarding devices [6, 7]. By deploying
SDN into the smart grid, the decoupling of the
control plane and the data plane not only increas-
es the flexibility, interoperability, and reliability of
the system, but also decreases system upgrade
costs by simplifying the hardware operation.
In this article, we propose a two-tier SDN based
framework for the PEV integrated smart grid to
SDN-Based Framework for the PEV Integrated Smart Grid
Nan Chen, Miao Wang, Ning Zhang, Xuemin (Sherman) Shen, and Dongmei Zhao
Nan Chen and Xuemin
(Sherman) Shen are with the
University of Waterloo
Miao Wang and Dongmei
Zhao are with McMaster
Ning Zhang is with the
University of Toronto.
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