Powerline Communications for Enabling Smart Grid Applications

SRC GRC Annual ReviewMarch 8, 2011

Powerline Communicationsfor Enabling Smart Grid Applications

Prof. Brian L. EvansWireless Networking and Communications

GroupThe University of Texas at Austin

Task ID 1836.063

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Task Description:Increase powerline communication (PLC) data rate for better monitoring/control applications for residential and commercial energy uses

Anticipated Results: Adaptive methods and real-time prototypes to increase bit-rates in PLC networks

Primary Investigator:Prof. Brian L. Evans, The University of Texas at Austin

Current Students Current StatusMs. Jing Lin Ph. D (expected graduation in May 2014)Mr. Yousof Mortazavi Ph. D (expected graduation in Dec. 2013)Mr. Marcel Nassar Ph. D (expected graduation in May 2012)

Industrial Liaisons:Dr. Anand Dabak (Texas Instruments), Mr. Leo Dehner (Freescale), Mr. Michael Dow (Freescale) and Mr. Frank Liu (IBM)

Starting Date: August 2010

Task Deliverables

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Data and algorithms for receiver synchronization, channel measurements and modeling, and asynchronous impulsive noise mitigation (12/2010)

Single-transmitter single-receiver (1x1) powerline communication system testbed: software package and documentation (5/2011)

Data and algorithms for multichannel transmission for a three-transmitter single-receiver (3x1) powerline communication system (12/2011)

Three-transmitter single-receiver (3x1) powerline communication system testbed: software package and documentation (5/2012)

Data and algorithms for crosstalk cancellation and low-power medium access control scheduling algorithms (12/2012)

Three-transmitter three-receiver (3x3) powerline communication system testbed: software package and documentation (5/2013)

Executive Summary Accomplishments

Investigated PLC standards Literature survey on powerline channel/noise characterization Built software and hardware framework for the PLC testbed Simulated receiver frame synchronization using chirp signal

Current work Asynchronous impulsive noise mitigation algorithms

Future directions Smart hand-shaking mechanisms between transmitter and receiver on the

best sub-band (with high SNR) for transmission Algorithms for synchronous impulsive noise mitigation Noise and channel modeling and analysis

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Background: Smart Grid Big Picture

Smart car : charge of electrical vehicles while

panels are producing

Long distance communication : access to isolated

houses

Real-Time : Customers profiling

enabling good predictions in

demand = no need to use an additional

power plant

Any disturbance due to a storm : action can be

taken immediately based on real-time

information

Smart building : significant cost

reduction on energy bill through remote

monitoring

Demand-side management :

boilers are activated during the night

when electricity is available

Micro- production:

better knowledge of

energy produced to balance the

network

Security features Fire is detected : relay can be switched

off rapidly

Source: ETSI5

Background: Voltage Levels in Grid

Medium-VoltageLow-

Voltage

High-Voltage

Source: ERDF

6“Last mile” PLC communications on low/medium voltage line

Concentrator

Motivation for “Last Mile” PLC

Source: Powerline Intelligent Metering Evolution (PRIME)

Alliance Draft v1.3E

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Concentrator controls medium to subscriber meters Similar to wireless communications basestation

Applications Automatic meter reading (right) Smart energy management Device-specific billing (plug-in hybrid)

Improving reliability and rate Mitigate impulsive noise Transmit over multiple phases

Standards target ~100 kbps ERDF G3-PLC [Électricité Réseau Dist. France] PoweRline Intelligent Metering Evolution (PRIME) Alliance

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PRIME Standard: Physical Layer Orthogonal Frequency Division Modulation (OFDM)

Divides transmission band into many narrow sub-channels

Transmission Band 42-89 kHzBaseband sampling rate 250kHzSubcarrier spacing 488.28125HzNumber of subcarriers 256FFT size 512 samplesCyclic prefix length 48 samplesNumber of data tones 84 (header) / 96 (payload)Number of pilot tones 13 (header) / 1 (payload)Subchannel constellation Phase-shift keying (2, 4 or 8 levels)Coding convolutional coding (rate ½)Max bit rate (uncoded) 42.9kbps, 85.7kbps, 128.6kbps

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Challenges Powerline Channel Impairments

Multipath and frequency-selective time-variant channel attenuation Background noise, impulsive noise, and narrow-band interference

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Source: Texas Instruments

Challenges (cont.) Performance degradation due to crosstalk

Induced by energy coupling across the phases or wires

Half-duplex operation eliminates ECHO and NEXT Without FEXT cancellation, achievable data rate is significantly degraded

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Presentation Roadmap Framework of PLC Testbed Receiver frame synchronization using a chirp signal Modeling of PLC channel noise

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PLC Testbed Framework of the 1X1 Bidirectional PLC Testbed

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Hardware Software

• National Instruments (NI) embedded computers process streams of data.

• National Instruments ADC/DAC generates/receives analog signals.

• Texas Instruments analog front end enables half-duplex operation.

• Transceiver algorithms implemented as C++ dynamically linked library, running in real-time embedded processors

• Desktop PC running LabVIEW provides GUI for configuring and displaying key system parameters

Receiver Synchronization Using Chirp• PRIME specifies a preamble to begin each burst. Preamble is a linearly frequency modulated chirp over 42-89 kHz

Chirp has constant envelope (in contrast to an OFDM signal) Received signal

Correlated with chirp to find start of burst Used to characterize channel

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SCH (t) Arect(t /T)cos 2 f0t 1/2t 2

f f f0T

,f0 41992 Hzf f 88867 HzT 2048 s

Experimental Results for Synchronization Texas Instrument Development Kit for PLC

Two modems communicate with each other in interleaved manner Gather samples at 250 kS/s

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Rx RxTx Tx

)

One Received Signal Burst

Pre

ambl

e - - - - - - - Payload - - - -

Hea

der 1

Hea

der 2

2.048

- each OFDM symbol is 2.240 ms -

In time domain, a burst has the following structure.

Frame Synchronization by Correlation

[Bumille & rLampe]

Linear scale Log scale

Chirp in Freq. Domain for Channel Est.

FFT length is 512

Ex. Decoding Second Header Symbol

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Looking at positive subcarriers only

BPSK modulated subcarriers (Information in phase)

PLC Channel Noise The powerline channel suffers from non AWGN noise Noise as superposition of five noise types [Zimmermann 2000]

19 Source: Broadband Powerline Communications: Network Design


20

Colored Background Noise:• PSD decreases with frequency• Superposition of numerous noise sources

with lower intensity• Time varying (order of minutes and hours)

Source: Broadband Powerline Communications: Network Design


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Narrowband Noise:• Sinusoidal with modulated amplitudes• Affects several subbands• Caused by medium and shortwave

broadcast channels



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Periodic Impulsive Noise Asynchronous to Main:• 50-200kHz• Caused by switching power supplies• Approximated by narrowbands



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Periodic Impulsive Noise Synchronous to Main:• 50-100Hz, Short duration impulses• PSD decreases with frequency • Caused by power convertors



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Asynchronous Impulsive Noise:• Caused by switching transients• Arbitrary interarrivals with micro-

millisecond durations• 50dB above background noise




Can be lumped together as Generalized Background Noise

Generalized Background Noise


Power spectral density of generalized background noise

Impulsive Noise Asynchronous noise dominates this class of noise


Need to statistically model two aspects: Impulse amplitude distribution Inter-arrival time between impulses

Asynchronous Impulsive Noise Modeling Amplitude statistics

Class-A Middleton [Umehara]

Weibull Distribution [Umehara]

Empirical Fits [Zimmermann]

Interarrival statistics Exponential distribution [Zimmermann]

Empirical Fits [Zimmermann]

Partitioned Markov chains [Zimmermann]

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Source: Zimmermann

Source: Zimmermann

Preliminary Noise Measurement

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0 10 20 30 40 50 60 70 80 90-125

-120

-115

-110

-105

-100

-95

-90

-85

-80

-75

Frequency (kHz)

Pow

er/fr

eque

ncy

(dB

/Hz)

Power Spectral Density Estimate


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0 10 20 30 40 50 60 70 80 90-125

-120

-115

-110

-105

-100

-95

-90

-85

-80

-75

Frequency (kHz)

Pow

er/fr

eque

ncy

(dB

/Hz)


Colored Background Noise


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0 10 20 30 40 50 60 70 80 90-125

-120

-115

-110

-105

-100

-95

-90

-85

-80

-75

Frequency (kHz)

Pow

er/fr

eque

ncy

(dB

/Hz)



Narrowband Noise


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0 10 20 30 40 50 60 70 80 90-125

-120

-115

-110

-105

-100

-95

-90

-85

-80

-75

Frequency (kHz)

Pow

er/fr

eque

ncy

(dB

/Hz)



Narrowband Noise

Periodic and Asynchronous Noise

List of Acronyms/AbbreviationsAcronym/Abbreviation MeaningCyc. Pref. Cyclic PrefixFEC Forward Error CorrectionFEXT Far-end crosstalkLV/MV Low-voltage / medium-voltageMAC Medium Access ControlMIMO Multi-Input Multi-OutputNEXT Near-end crosstalkOFDM Orthogonal Frequency Division

MultiplexingPAPR Peak to average power ratioPHY Physical layerPSD Power Spectral DensitySFSK Spread Frequency Shift Keying

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ReferencesBumiller and Lampe, “Fast Burst Synchronization for PLC Systems,”

Proc. IEEE Int. Sym. Power Line Comm. and its Applications, 2007, pp. 65 - 70

H. Hrasnica, A. Haidine, and R. Lehnert, Broadband Powerline Communications: Network Design, Wiley 2004.

A. G. Olson, A. Chopra, Y. Mortazavi, I. C. Wong, and B. L. Evans, “Real-Time MIMO Discrete Multitone Transceiver Testbed”, Proc. Asilomar Conf. on Signals, Systems, and Computers, Nov. 4-7, 2007, Pacific Grove, CA.

D. Umehara, S. Hirata, S. Denno, and Y. Morihiro, “Modeling of impulse noise for indoor broadband power line communications”, Proc. IEEE Int. Sym. on Information Theory and Its Applications, Oct. 29-Nov. 1, 2006, pp. 195-200.

M. Zimmermann and K. Dostert, "Analysis and modeling of impulsive noise in broad-band powerline communications,” IEEE Trans. on Electromagnetic Compatibility, vol.44, no.1, pp.249-258, Feb 2002.

Freescale solutions for smart metering and smart grid enablement, http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=02430Z6A10

Texas Instruments Powerline Communications solutions http://www.ti.com/ww/en/apps/power_line_communications/index.html?DCMP=plc&HQS=Other+OT+plc34

http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=02430Z6A10

http://www.freescale.com/webapp/sps/site/overview.jsp?nodeId=02430Z6A10

http://www.ti.com/ww/en/apps/power_line_communications/index.html?DCMP=plc&HQS=Other+OT+plc

http://www.ti.com/ww/en/apps/power_line_communications/index.html?DCMP=plc&HQS=Other+OT+plc

Documents

Powerline Communications for Enabling Smart Grid Applications