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March 2013, IE Tech News
The Frontier of Smart Grids:
An Industrial Electronics Perspective
Xinghuo Yu1, Carlo Cecati2, Tharam Dillon3, M. Godoy Simoes4
1Platform
Technologies Research Institute, RMIT University, Melbourne, Australia
2Department
3La
of Electrical and Information Engineerining, University of L’Aquila, L’Aquila, Italy
Trobe Technology, Melbourne, Australia
4Center
for Advanced Control of Energy and Power Systems, Colarado School of Mines, Golden, USA
Table of Contents

Introduction

Power Electronics

Intelligent Systems and Control

IT Infrastructure

Discussions and Conclusions
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Introduction: The Electricity and Electric Grid
The electric grid is a massive
interconnected network used to
deliver electricity from suppliers to
consumers.
Distinct operations of electric grids
include generation, transmission and
distribution.
Presently, the dominating generation
mechanism is by electro-mechanical
generators driven by heat engines
fueled by chemical combustion or
nuclear fission.
Figure 1: The traditional electric grid.
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Introduction: The Need for Smart Grids
Smart Energy refers to making energy use more efficient by utilizing the
integration of advanced technologies such as information and communication
technologies (ICT), electronics and material engineering.
Smart Energy is needed for a number of reasons, e.g.
• Limited availability of non-renewable energy sources such as coal, gas
and oil on Earth.
• Pollution concerns such as carbon dioxide, nitrous oxide and dust air from
burning coal and oil.
Smart Energy is about taking a holistic approach in dealing with efficient
energy supply and demand considering economic, environmental and social
objectives.
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Introduction: The Concept of Smart Grids
The term Smart Grid (SG) refers to
electricity networks that can
intelligently integrate the behavior and
actions of all users connected to it, for
example generators, customers and
those that do both – in order to
efficiently deliver sustainable,
economic and secure electricity
supplies.
SG is an enabler for Smart Energy.
Figure 2: The future electric grid.
The Frontier of Smart Grids: An Industrial Electronics Perspective
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Introduction: The Concept of Smart Grids
The conceptual model of Smart Grid,
defined by the National Institute of
Standards and Technology (NIST),
consists of seven important domains
concerning :
– Bulk generation
– Transmission
– Distribution
– Customers
– service provider
– Operations, and
– Markets
Figure 3: The NIST conceptual model of SG
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Introduction: The Concept of Smart Grids
In SG, the traditional role of central
generation, transmission, and
distribution is transformed by
aggregation of distributed resources
(see Figure 4).
Power from local generation can be
directed to the feeder with non-critical
loads or be sold to the utility if agreed
or allowed by net metering.
A microgrid can be designed for the
requirements of end-users, a stark
difference from the central generation
paradigm.
The Frontier of Smart Grids: An Industrial Electronics Perspective
Figure 4: A microgrid architecture
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Introduction: Key Issues in Smart Grids
Several technical challenges: intermittency of RE generation that affects
electricity quality; large scale networks of small distributed generation
mechanisms, for example photovoltaic (PV) panels, batteries, wind and solar,
plug-in hybrid electric vehicles (PHEV).
An important characteristic of power usage is the big margin between the
peak and average usages; reducing peak demands can help utilize existing
infrastructure to meet increase of energy demands due to economic growth.
Technological advances required include
– Distributed control
– Demand prediction
– Generation prediction
– Demand response.
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Power Electronics:
Introduction
The technology of power electronics is
fundamental in SG because there will
be deeper penetration of renewable
and alternative energy sources which
require power converter systems.
A power converter is an interface
between SG and local power sources.
Moreover, they are required by several
sub-systems involving energy storage
or harmonic compensation
interconnecting areas or separated
grids.
Figure 5: Active and reactive power balance for alternative
energy conversion
Power converters are a key technology
to enable SG to function.
Figure 6: Integration of several sources of energy into the grid
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Power Electronics:
Introduction (Contd.)
A typical distributed generation system
architecture is shown in Figure 7 which
consists of:
a) a typical dc link integration very
commonly used when dc sources (PVs,
fuel cells, batteries) are integrated.
(a)
b) a typical ac link integration, where
turbines and rotating machines are
integrated through the utility line
frequency, and
(b)
c) a high frequency ac link integration,
where fast response and decreased
system size can be achieved.
(c)
Figure 7: Energy Integration with DC, AC or
HFAC Link: (a) dc link integration; (b) ac link
integration; (c) hfac link integration.
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Power Electronics:
Generation from Solar Energy
DC/DC converters may provide the necessary voltage boost and regulation.
Typically MPPT control algorithms are used in extracting the highest power
from the sun.
Usually the dc/dc converter is connected to a PWM inverter with grid
synchronization capabilities, or multilevel converter topologies for high
voltage applications.
The inverter must attain correct synchronous operations, with a good low
pass filter, in order to observe utility interconnection standards.
An energy storage system may be connected in parallel at the inverter input
terminal for balancing the impact of PV energy fluctuations.
The inverter can have several smart functionalities allowing the
communication with utilities, users and local neighborhood.
The Frontier of Smart Grids: An Industrial Electronics Perspective
March 2013, IE Tech News
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Power Electronics:
Generation from Wind Energy
Wind Energy Conversion Systems consists of an ac generator (synchronous
or asynchronous machine) and a power converter, usually consisting of
• a cascade ac/dc rectifier
• dc/dc converter (useful for dc link voltage regulation and control)
• and dc/ac converter.
Dc/ac conversions are similar from those used in PV converters, but usually
designed for higher power levels (up to 10 MVA).
Typically, multilevel converters are promising solutions. But, other topologies
like neutral point clamped or flying capacitor may be employed in both ac/dc
and dc/ac stages. Matrix converters can also be considered for ac/ac
applications.
The MPPT is often designed to optimize the turbine aerodynamics and
sometimes improve efficiency in induction generators with optimized
excitation flux.
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Power Electronics:
FACTS Systems & Power Quality Issues
Flexible Alternating Current Transmission Systems (FACTS) increase grid
efficiency and stability through the use of power converters providing to:
• Voltage regulation
• Reactive Power balance (fundamental in large WECS located in rural
area)
• Power Factor Control
• Power Quality enhancements
 Typical power converters are: Static VAR Compensators, Power Factor
Controllers. They often have different topologies, including the recent
multilevel converters. In this area, converters for High Voltage Direct Current
are also important.
The Frontier of Smart Grids: An Industrial Electronics Perspective
March 2013, IE Tech News
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Intelligent Systems and Control:
Introduction
SGs are highly complex, nonlinear dynamical networks by nature that present
many theoretical and practical challenges.
Monitoring and control are key issues that need to be addressed to make SG
more intelligent and equipped with self-healing, self-organizing, and selfconfiguring capabilities.
Another important issue is the Big Data environment that SG is in, which pose
the questions that
– How to automate the acquisition of useful operation information in order to
make informed operation decision in a timely fashion?
– How to present the information to users in a most compelling and informed
way to help users make high-level operation decision without bogging
down into unnecessary waste of time in understanding rather raw data?
The Frontier of Smart Grids: An Industrial Electronics Perspective
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Intelligent Systems and Control:
Dealing with Network Complexity
With increasing complexity compounded
by distributed nature of RE, real-time
performance is a bottleneck in deriving
just-enough and just-in-time information
for.
One promising methodology is the
Complex Networks (CN) theory
originated from the graph theory which
can be used in combination with existing
methods and tools to simplify the
analysis and design so that timely
response is possible.
Figure 8: Typical types of complex networks
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Intelligent Systems and Control:
Intelligent Systems
Future SG requires not only automation
of operations at the lower operational
levels, but also high-level decisions to
take consideration of macro economic
and social requirements.
Decision-support is a key in making SG
more responsive to user demands.
A typical decision support framework is
shown in Figure 9, which is a knowledgebased meta-fuzzy system incorporating
expert systems and extended fuzzy
systems including a new meta-fuzzy
logic mechanism and a discourse
semantics as an explanatory
mechanism.
Figure 9: An industrial decision support framework
The Frontier of Smart Grids: An Industrial Electronics Perspective
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Intelligent Systems and Control:
Intelligent Systems (contd.)
Multi-agent systems are another
approach that enable distributed decision
making and automation in SG.
An agent is a software entity that can
represent and control a hardware
component.
Agents can communicate and interact
with each other and their environment.
This allows them to cooperate or
compete towards local and/or global
goals.
Figure 10: A multi-agent system
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Intelligent Systems and Control:
Control Systems
SG systems exhibit the following features:
– a) a large scale network structure;
– b) many of the controls are embedded in the system; future control
designs which must make use of these existing controls;
– c) the overall control scheme has a hierarchical structure;
– d) the available control actions are already largely physically determined
and have diverse timing, cost and priority for action;
– e) the control goals are multi-objective with local and global requirements
which vary with system operating states;
– f) there is a need for a high level of distributed global control mechanism
which can provide a meta-view to coordinate local controllers.
There is a need to rethink about how SG should be controlled in such a
complex environment. Complex networks and multi-agent systems provide an
alternative approach in dealing with complexity.
The Frontier of Smart Grids: An Industrial Electronics Perspective
March 2013, IE Tech News
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IT Infrastructure:
Introduction
IT Infrastructure is the backbone
enabler for SG to be aware of what is
going on, deciding best strategies for
monitoring and control and
responding to demand side responses
while keeping the grids to operate
efficiently, cost less and neutralize the
negative impact on environments.
A platform for information exchange is
needed that enables smart appliances
and smart meters to exchange the
information between them as shown
in Figure 10.
Figure 11: Smart link between the utility grid and smart gateway
The Frontier of Smart Grids: An Industrial Electronics Perspective
March 2013, IE Tech News
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IT Infrastructure:
Cyber-Physical Systems
The Cyber-Physical Systems (CPS)
can offer such a platform that allows for
both the digital information as well as
traditional energy (for example
electricity) to flow through a two-way
smart infrastructure.
CPS was defined by the National
Science Foundation (NSF) as physical
and engineered systems whose
operations are monitored, coordinated,
controlled and integrated by a
computing and communication core.
Figure 12: Reference architecture of CPS
CPS involves computation, human
activities, and automated decision
making enabled by ICT.
The Frontier of Smart Grids: An Industrial Electronics Perspective
March 2013, IE Tech News
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IT Infrastructure:
Realization of WoT Bsed CPS Architecture
CPS can be achieved by using the Internet of Things or Web of Things (WoT)
computing paradigm as a dynamic global network infrastructure with self
configuring capabilities based on standard and interoperable communication
protocols.
WoT framework for CPS has five layers, namely, device, kernel, overlay,
context and API. The challenges are
– IP addressable things and smart gateways
– Flexibility in wireless communication
– Common embedded platform for information exchange
– Representation of events
– Abstraction of suitable events
The Frontier of Smart Grids: An Industrial Electronics Perspective
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Discussions and Conclusions
We have presented some future research and development challenges and
opportunities in SG in three related but distinct focal areas as pertinent to
IEEE IES. Future developments in these three focal areas need to be
integrated.
We hope this paper serves the purpose of inspiring researchers and
practitioners to get further involved in this exciting frontier of SG.
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