NUI Galway – UL Alliance First Annual ENGINEERING AND - ARAN ...

Future Smart Grid Synchronization Challenges
Jonathan Shannon, Hugh Melvin, Ronan O hOgartaigh
Performance Engineering Lab (PEL), College of Engineering and Informatics, NUI Galway,
shannon.jonathan@gmail.com, hugh.melvin@nuigalway.ie
Abstract
The success of the evolving smart grid project will
depend hugely on ICT (Information and
Communication Technologies) to revolutionise the
traditional power grid and will place various demands
on current synchronisation techniques. Utilisation of
wireless communication systems within the smart grid
infrastructure seems inevitable, thus, if the smart grid
project is to reach its full potential then some of the
shortfalls of current synchronisation techniques over
wireless must be remedied.
1. Introduction
The current electricity grid is a real-time system
whereby generation must always match demand. In any
real-time system, time is a critical factor and when the
system is distributed, synchronisation of its various
elements is essential. Current grid infrastructures
employ synchronisation techniques to permit such
functions as fault detection, protection testing, load
balancing, scheduling and analysis. While the reliance
on synchronisation techniques is quite significant, the
future smart grid will be much more demanding in terms
of synchronization requirements.
The smart grid project aims to revolutionise the
current grid infrastructure in order to reduce inefficient
energy consumption, to facilitate the move towards
renewable energy, and to better utilise the grid’s
capacity so as to accommodate growing electricity
demand. Smart grid will by definition significantly
increase the complexity of the current grid’s static
design by transforming it into a much more dynamic
network where the distinction between producer and
consumer will often be blurred. The composite elements
of this complex system will place significant demands
on current synchronisation technologies in order to meet
its full potential.
2. Research
A key driver for the smart grid project will be
through integration of ICT into the electricity grid, from
generators through transmission right down to
consumers. As such, a smart grid system will utilse
synchronisation techniques currently employed by ICT
systems. Within the wired domain of current ICT
infrastructures, synchronization protocols such as the
Network Time Protocol (NTP) and IEEE 1588 (PTP)
allow a host to discipline its clock to within a
millisecond and a microsecond of UTC time
respectively. These protocols are limited in that in their
basic state they assume symmetric message delays to
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and from a host. Although this assumption may often
hold for wired networks, it is rarely true of the wireless
domain. The asymmetric communication latencies
observed over wireless networks, particularly those with
many hosts and high traffic loads, significantly affect
the performance of these protocols. This can be
attributed to the medium access rules imposed by
common wireless protocols, which dictate that hosts
access the shared medium in a fair manner, thus,
resulting in contention and, hence, varying medium
access delays.
3. Solution
One method of overcoming this issue is to provide
these protocols with information related to medium
access delays. This necessitates a method of
determining the wireless medium access delays
associated with a message and delivering this
information in a suitable manner such that these
protocols can use it to mitigate synchronisation errors.
Another possible solution that will be explored is the
possibility of improving synchronisation protocols by
analysing past data. Analysis of past data could help to
identify network trends and make predictions about the
future state of the network.
Regardless of the approach taken, the ultimate
contribution will be a module that can be linked to some
synchronisation protocol and used to mitigate the effects
of wireless contention.
Acknowledgements
Our research is being undertaken at NUI Galway
within the Performance Engineering Lab (PEL)
research group and is funded by IRCSET. We also
wish to acknowledge the assistance and contributions
from ESB Networks.
8. References
[1] Kenneth E. Martin, “Precise Timing in Electric Power
Systems,” IEEE International Frequency Control Symposium
(IEEE), p. 15-22, 1993.
[2] Network Time Protocol (NTP).
http://www.faqs.org/rfcs/rfc1305.html
[3] IEEE-1588 - Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems.