smart grid communications: requirements and...

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Smart Grid Communications:

Requirements and Challenges

Dr. Salman Mohagheghi

Department of Electrical Engineering and Computer Science

Colorado School of Mines

Golden, CO 80401

[email protected]

2/35Dr. Salman Mohagheghi

Jan. 13, 2015

� The grid has always been smart; however, it is now smarter

� The modern power grid is different from the traditional power

grid in several aspects:

� More data captured from across the grid

� More opportunities for remote control

� Open non-proprietary designs

� Access to more computational power

� Abundance of structured data

� More reliable and efficient communication networks

� To Summarize:

� Smart Grid is more about Creation, Transmission and

Utilization of Smart Data

Smart Grid – The Reality

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Jan. 13, 2015

� Renewable Energy Resources

� Introduce fast dynamics and stochastic variations

� Distributed across the power grid ⇒⇒⇒⇒ more volatility

� Introduce bidirectional flow of power

What Has Changed?


Jan. 13, 2015

� Higher Penetration of Sensors and Actuators

� Intelligent Electronic Devices (IED): provide phasor and

non-phasor measurements

� Advanced Metering Infrastructure: allow for remotely

connecting/disconnecting power, reading usage,

detecting outages, detecting power theft, enabling DR

� Almost all equipment and functions have the potential to

be automated

What Has Changed?

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Jan. 13, 2015

� Demand Responsive Loads

� Active consumers varying their consumption based on

the variable electricity rates

� Controllable loads through Home Energy Management

System (HEMS)

What Has Changed?


Jan. 13, 2015

� Mobile Energy Resources

� Moving vehicles able to charge (G4V) or discharge (V2G)

their batteries while in motion

� Parked vehicles being remotely charged/discharged

What Has Changed?

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Jan. 13, 2015

� More Connectivity

� Traditional utility networks connect control centers,

generators, and major substations

� Traditionally, distribution domain has limited

connectivity

� Enabling automated solutions require higher connectivity

across all domains

� More measurements are needed from across the

network

What Is Needed?


Jan. 13, 2015

� More Granular Load Modeling

� Extract consumption and behavioral patterns for

individual customers

� Forecast demand beyond the service transformer

What Is Needed?

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Jan. 13, 2015

� Dynamic State Estimation

� Traditional state estimators provide the state of the

system under the assumption of quasi-steady-state

operation

� At the modern power grid we need to consider:

� Hybrid solution with GPS-synchronized (PMU) and

non-synchronized measurements

� Frequency dynamics and generator dynamics

� Also, if applicable/necessary:

� Three-phase analysis

� Harmonics

� Distributed state estimation

What Is Needed?


Jan. 13, 2015

� Dynamic Dispatch of Energy Resources

What Is Needed?

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Jan. 13, 2015

� Wide Area Control

� Allows for coordination between FACTS devices and

generators

� Improves transient and dynamic stability

� Helps avoid voltage collapse and cascading failures

What Is Needed?


Jan. 13, 2015

� NIST has divided the smart grid into 7 domains

� Smart grid is a cyberphysical system that is achieved by

overlaying communication infrastructure with the electric grid

Smart Grid Conceptual Model

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Jan. 13, 2015

Communication Requirements and Characteristics

Transmission

Unicast

Multicast

Broadcast

Data Specs

Trans. Rate

Size

Data Priority

Impact if Lost

Quality

Latency

Validity

Accuracy

Integrity

Reliability

Packet Loss

ACK

Retransmission

Sequencing

Scalability

Upgradability

System Growth

Big Data

Low Cost

Deployment

Maintenance

Energy

Bandwidth

Availability

Redundancy

Self-Healing

Fault Tolerance

Security

Authentication

Encryption

Access Control

Confidentiality


Jan. 13, 2015

� Smart Grid consists of a multitude of heterogeneous devices

that try to talk to each other across heterogeneous networks

� Interoperability is critical for seamless integration

� Information model and communication services need to be

understandable by all parties involved

� Solutions should be technology neutral

� Interoperability:

� Encourages competition

� Helps lower cost

� Helps improve design efficiencies

� Future Concept: Interchangeability (or substitutability)

Need for Interoperability

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Jan. 13, 2015

� Network Architecture

� A stack of layers and protocols

� Each layer offers certain services to the higher layers

while shielding them from how these services are

implemented

� Benefits:

� As long as the services are provided as specified, the

implementation of underlying layers can be changed

� New services that build on the existing services can

be introduced at any time



Jan. 13, 2015


Open Systems Interconnection

(OSI) Reference Model

TCP/IP Reference Model

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Jan. 13, 2015

� Power Line Communications

� Idea: High-rate communication over the power lines

(data signal superimposed on the 60Hz component)

Communication Media

Low Voltage

Medium Voltage


Jan. 13, 2015

� Fiber Optics

� Are used for long-haul transmission network backbones,

high-speed LANs, high speed internet such as Fiber to the

Home (FttH)

� Unidirectional

Communication Media

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Jan. 13, 2015

� Cellular Networks

� Wireless coverage for a large number of fixed or mobile

devices over a large geographical area

� Utilities have been using these networks to connect their

assets, for mobile workforce, or for metering

� Third Generation: Digital Voice and Data; CDMA

� Fourth Generation: High BW, connectivity everywhere,

seamless integration with other wired/wireless IP

networks, adaptive resource and spectrum management

Communication Media


Jan. 13, 2015

� WiMAX/IEEE 802.16

� Offer multi Mbps wireless communication; sometimes

referred to as Wireless MAN or Wireless Local Loop

� Uses OFDM to fight delay, MIMO for increased BW

efficiency and adaptive modulation for robustness

� Can operate with NLOS

� Initially, for stationary users (IEEE 802.16d), but now

enhanced to allow mobility at vehicular speeds (IEEE

802.16e)

Communication Media

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Jan. 13, 2015

� Satellite Networks

� Ideal for remote control/monitoring of rural and isolated

sections and for data collection from PMUs

� Can be a safe backup system for the terrestrial network

Communication Media


Jan. 13, 2015

� Wireless LAN (Wi-Fi/IEEE 802.11)

Communication Media

Upper Layers

MAC Sublayer MAC Sublayer MAC Sublayer MAC Sublayer MAC Sublayer

802.11 (legacy)

FHSS and Infrared

“now obsolete”

(Released 1997 –

1999)

802.11a

Up to 54Mbps

5GHz ISM

OFDM

(Released 1999)

802.11b

Up to 11Mbps

2.4GHz ISM

Spread Spectrum

(Released 1999)

802.11g

Up to 54Mbps

2.4GHz ISM

OFDM

Compatible with

11b

(Released 2003)

802.11n

Up to 600Mbps

MIMO OFDM

(Released 2009)

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Jan. 13, 2015

� ZigBee

� Wireless PANs (developed by IEEE 802.15)

� Requires short distance communications (tens of meters

range) and focus on long-lasting battery life and low cost

� The key features of the standard are:

� Uses CSMA/CA

� Built on top of the physical/MAC layers specified in

802.15

Communication Media


Jan. 13, 2015

� Hybrid Solutions

� Need to combine the existing communication networks

with more advanced solutions

� Instead of redundant designs to provide robustness, one

can combine different technologies (wired and wireless)

� Example: SEP 2.0 protocol supports ZigBee and

HomePlug

Networking Solutions

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Jan. 13, 2015

� Wireless Sensor Networks

� Idea: Network of small and cheap nodes that are capable

of sensing, communication and computation

� Provide means for real-time distributed sensing

� Provide real-time information to the utility

� Are a cost-effective low-power solution for remote

monitoring

� Allow the utility to diagnose developing problems early

� Allow the utility to dynamically control the grid and

dispatch the energy resources



Jan. 13, 2015

� Sensor and Actuator Networks (SANETs)

� Used for both monitoring and control

� Enable closed loop control in a centralized or

decentralized manner

� Sensors: current, voltage, power, temperature, vibration,

position, motion/occupancy, etc

� Actuators: breaker, switch/contactor, valve, motor,

dimmer, HEMS display/monitor


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Jan. 13, 2015

� Machine-to-Machine (M2M) Communications

� A network of devices that communicate with one

another without human intervention

� Main Driver:

� A large number of devices performing autonomous

control and monitoring tasks in a usually unattended

field environment

� Required Features:

� Scalability, energy efficiency, autonomous operation,

mobility, remote operation, relatively low data rate

(up to 100s of kbps), hard real-time requirements,

high security (since devices are remote and

unattended)



Jan. 13, 2015

� Public vs. Private Networks

� Public networks are more affordable

� Involving multiple public providers can improve fault

tolerance or extend coverage

� Private networks addresses utility concerns regarding

reliability, security, availability and lack of control

� Utilities are also concerned that their devices may not be

able to keep up with the fast rate of technology change in

public networks and may become obsolete


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Jan. 13, 2015

� IP-Based Networking

� Smart Grid networks are expected to be based on IP

� IP is scalable, interoperable and robust

� IPv6 provides means for unique identification of devices

(128-bit vs. 32-bit addressing)

� Internetworking: Multiprotocol Label Switching (MPLS)

allows for integration of multiple heterogeneous

networks

� IPv6 has IP Security (IPSec) authentication which is

complex and resource intensive

� 6LoWPAN: recommendations by Internet Engineering TF

for efficient use of IPv6 for low power, low cost wireless

devices



Jan. 13, 2015

� Compressive Sensing

� Idea: Exploit temporal and spatial correlation of data to

avoid unnecessary data transmission or excessive

measurements

� Helps reduce energy consumption and usage of

computational resources

� Allows to achieve the same performance by deploying

less sensors

� Provides selective data transmission that saves BW and

avoids data bottleneck

� Example: measurements in solar parks and/or wind

farms using the correlation temporal/spatial correlations

in irradiance and/or wind speed


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Jan. 13, 2015

History of Communication Systems

Phase Years Characteristics Architecture Media Standards

Proprietary

Systems

Before

1985

Single vendor

Basic data collection

Hierarchical

Isolated

systems

RS232/485

Dial-up, PLC,

Trunked radio

< 1200bps

Modbus

SEL

WISP

Early

Standards

1985–1995 Multi-vendor

Protocol conversion

Hierarchical

Redundant

links

Leased lines

Packet radio

9.6-19.2kbps

DNP3 serial

IEC 60870

TASE 2

Area

Networks

1995–2000 Substation LAN

Merging protection

and SCADA

Peer-to-peer in

substations

Joining

substations via

WAN

Ethernet

Spread

spectrum radio

Mbps rates

TCP/IP

DNP3

WAN/LAN

UCA 2.0

Telnet

Business

Integration

After 2000 Merging automation

and business

Corporate IT

Asset management

Link WANs to

corporate

networks

Customer

premises

Digital cellular

WLAN

Gbps rates

TCP/IP

IEC 61850

XML

Adopted from E. Hossain, Z. Han and H.V. Poor, Smart Grid Communications and Networking, Cambridge University Press,

2012


Jan. 13, 2015

� Conserving Power and Bandwidth

� Use compressive sensing to avoid unnecessary data transmission

� Use data compression and data aggregation

� Adopt decentralized control rather than centralized control

� Coordinated control between different devices to avoid unwanted

interactions and excessive control effort

� Use low-complexity control algorithms for distributed controllers

� Use low-complexity communication protocols

� Power harvesting

Existing Challenges

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Jan. 13, 2015

� Security

� Every sensor, actuator, controller, component can be potentially

used by intruders to attack the grid

� Attack can be ongoing without the utility noticing it

� Risk = Probability of Threat ×××× Impact

Risk = Pr(Threat) ×××× E[Impact | Vulnerability] ×××× Pr(Vulnerability)

� Risk Management

� Identify vulnerabilities and potential consequences

� Assess risk scenarios quantitatively or qualitatively

� Develop mitigation strategies

� Implement mitigation strategies based on risk priority

� Need to develop accurate cyber-physical models

Existing Challenges


Jan. 13, 2015

� Privacy

� Who is after the consumer’s data?

� Industries – marketing products through extracting

consumption patterns

� Social Networking Websites – selling your data in exchange for

(not necessarily essential) services

� Burglars – spying on the occupants based on energy

consumption or charge/discharge patterns of EVs

� Hackers – identity theft

Existing Challenges

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Jan. 13, 2015

� A.S. Tanenbaum and D.J. Wetheral, Computer Networks, 5th Ed., Prentice

Hall, 2010

� L.T. Berger and K. Iniewski, Smart Grid – Applications, Communications

and Security, John Wiley, 2012

� E. Hossain, Z. Han and H.V. Poor, Smart Grid Communications and

Networking, Cambridge University Press, 2012

References

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