power seminar

8/18/2019 Power Seminar

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Data Exchange Design and A Textured

State Estimation Algorithm ForDistributed Multi-Utility Operations In

Electric o!er Mar"et

Jiansheng Lei

Advisor: Dr. Garng M. Huang

Department of Electrical Engineering

Texas AM !niversit"



2

Topics Today

• Topic1: An expert system is proposed to search for mostbeneficial and efficient data exchange schemes while avoidharmful data exchange at the same time. In addition, the impactof data exchange on new measurement design and the issues

on price of exchanged data are also discussed.• Topic: !ased on the data exchange design, a concurrent non"

recursive textured algorithm for distributed multi"utility stateestimation is formulated to avoid the disadvantages of both #ne$tate %stimator &#$%' and existing distributed state estimation

&($%' algorithms. The newly proposed algorithm is especiallyuseful for large"scale power systems with multiple independentexisting distributed estimators, such as )ega *egionalTransmission #rgani+ations &)ega"*T#s'.



3

#ac"ground $%&

• $tate estimation &$%' is essential for

monitoring, control and optimi+ation of

a power system.• *egardless of the different estimation

algorithms, the locations and types of

measurements are always decisivefactors for successful state estimation.



4

#ac"ground $'&

• In the regulated environment, the whole power system is owned

by a limited number of locally monopolistic organi+ations. There

is almost no need to exchange data with other organi+ations,

ote: -(ata mainly refers to both raw instrumentation data and

estimation results.

• In a deregulated environment, there are multiple member

companies who must cooperate to run the system and to

achieve their own economic goals. /ower companies are

Company A

RTO BCompany B

RTO A

Whole System

ISO A for

Company A&B

releasing their transmission grids toform I$#s0*T#s while their own local

state estimators are already in use.



5

#ac"ground $(&

• A recent trend for these I$#s0*T#s is to further cooperate and

to run the power maret on even a bigger grid as a )ega"*T#

for a better maret efficiency. The grid of an I$#0*T# could be

large. The si+e of )ega"*T# is even bigger, as concludedrecently by 2ederal %nergy *egulatory 3ommission &2*%3' 45

that only four )ega"*T#s should cover the entire nation beside

Texas.

RTO A

RTO DRTO C

RTO B Mega-RTO

Whole System



6

Topic% Data Exchange

• Ho# to exchange instrumentation or estimateddata #ith neigh$oring entities%

ew issues under power maret environment

$elected data exchange improves the 6uality of estimators inindividual entities, on both estimation reliability and accuracy.

Traditional measurement placement methodology need to bemodified to fully utili+e the benefit of data exchange.

ot necessarily all data exchanges are beneficial.

3ritical to the newly proposed textured distributed stateestimation algorithm in Topic.



#us )redibility Index BCI(b,S)

• Estimation &elia$ilit": $ad data detection and identification

capa$ilit" and pro$a$ilit" to maintain o$serva$ilit" under

measurement loss

•'() is a pro$a$ilit" measure that *uantifies the estimationrelia$ilit" on $us b #ith respect to a specified s"stem S .

• A more accurate criterion compared #ith local or glo$al

$us redundanc" level

• data exchanges modif" the original s"stem + to +,- and theincremental difference of '() from (b,S) to (b,S’) stands for

the $enefit of such a data exchange on $us b.



*no!ledge #ase

• &a# facts The configuration- parameters and o#nership of current

po#er s"stem net#or and measurement s"stem/

The failure pro$a$ilit" and accurac" of measurements/

The cost of instrumentation and estimated data exchange/

• BCI(b, S)

• 0ariance of +tate Estimation Errors Accurac" on $us b #ith respect to a specific s"stem S



A +easoning Machine $%&

• The distri$uted state estimation algorithm isdiscussed in Topic1. Here the design of dataexchange scheme is the focus.

• An )EEE234 'us s"stem isused to illustrate ho# thereasoning machine #ors

• 5ote that the algorithm and

rules are applica$le to an"s"stem.

RTO B

Two RTOs merge n!o one "ega#RTO

RTO A


http://slidepdf.com/reader/full/power-seminar 10/34$%

A +easoning Machine $'&

• +tep3: Determine maximum possi$le$enefit on +E relia$ilit" performance

*emar: #nly boundary buses are concerned because in most

cases !3I of internal buses also improves with a much smallerrate when !3I of boundary buses improve.

• +tep1: )gnore the $oundar" $us #hosemaximum possi$le $enefit is small

&'(&'( Ab BCI Wholeb BCI A A

−

&'(&'( Bb BCI Wholeb BCI B B −


http://slidepdf.com/reader/full/power-seminar 11/34$$

A +easoning Machine $(&

• +tep6.3: &ules to search for $eneficial

)nstrumentation data exchange: 2or boundary bus b A in A, instrumentation data exchange

should extend to boundary bus bB in ! under the condition:

2or example, it is reasonable for b and b7 in ! to extends to

include b1 and b8 in A. !ut it does not follow the rule that b9 in

! extends to include b1 or b17 in A.

Avoid forming a radial structure; instead, a loop is preferred.

2or example, b9 in ! extend only to b1 in A will form a new

radial branch b9"b1, which violates this principle.

&'(&'( Ab BCI Wholeb BCI A B >


http://slidepdf.com/reader/full/power-seminar 12/34$2

A +easoning Machine $,&

• +tep6.1: &ule to search for $eneficial

estimation data exchange:

If BCI(b,A)>BCI(b,B)

where bus b is in the common part of A and !

Then estimation result exchange from A to ! on this

bus will improve BCI(b,B) to the magnitude of BCI(b,A)

.



A +easoning Machine $&

• +tep4.3 +"stem A or ' are modified accordingl"

$ased on the data exchange ne#l" found.

!3I, estimation accuracy and the economic cost are

evaluated on the -new system $ to verify the benefit.

If !3I&b,$' are already close to !3I&b,<hole', then

there is no need to search for new data exchange for

bus b.• +tep4.1 +earching process is iterated on all

$oundar" $uses.



Economic Factor $%&

• Hard#are7soft#are cost on data exchange

implementation should $e minimi8ed given

the condition that performance is satisfied. %ven if scheme (1 is slightly better than scheme ( in

performance, but it is still possible for industry to select (1

when (1 is much more economical than (.

The benefit of different data exchange schemes may differ

greatly. The benefit may saturate after some data exchange,

which implies no ma=or benefit can be obtained for further data

exchange.



Economic Factor $'&

• 9rice tag reflects not onl" installation

cost $ut also maret value.

It is possible for system A to attach a rather high price tag to ameasurement that is especially useful to system !.

• The proposed expert s"stem is critical

for the companies to determine themaret price $ased on the $enefit of

data exchange.



Economic Factor $(&

• 5e# measurements can $e sold to other

companies

•Data exchange #ill have some impact onmeasurement placement decision.

• 9roposed expert s"stem is useful for the

ne# measurement placement decision



)ase%./arm0ul Data Exchange $%&

•ot following our principles

•$% reliability decreases•$% accuracy decreases

•<asted investmentB af!er )armf*+ ,a!a e-.)ange

Da!a

/-.)ange

B 0efore ,a!a e-.)ange

#riginal ! )odified ! <hole $ystem

%19647 %19643 %19662

Average BCI on the buses of B

Average Estimation Error on the buses of B

#riginal ! )odified ! <hole $ystem

7173$4e#%%7 81$738e#%%7 216326e#%%7



)ase%./arm0ul Data Exchange $'&

Assumption:•9 and 9-7 are $ad data- #here the sign of measurements are reversed.•5o $ad data on the exchanged data.

acts:•'efore data exchange these t#o $ad data are identified correctl".•After harmful data exchange these $ad data cannot $e detected at all.•Estimation result on local estimator area is harmed.

Iteration

No.

B before data exchange B after harmful data exchange

Meas. Max. Residue Meas. Max. Residue

1st 9 16.!" 9-4 #$.1"nd 9-7 1%#.%& 7-4 &6.!#

'rd No bad data detected 4 '.6#th N/A No bad data detected

1ormali2ed +esidues For 3ocal Estimator B



)ase'. E00iciency o0 #ene0icialData Exchange

•'() is as good as the #hole s"stem

•Estimation Accurac" is almost asgood as the #hole s"stem

•ollo#ing our rules lead to high

efficient data exchange

#riginal ! )odified ! <hole

%19647 %19662 %19662

Average BCI on the buses of B

Average Estimation Error on the buses of B#riginal ! )odified ! <hole

7173$4e#%%7 21647$e#%%7 216326e#%%7

o.a+ es!ma!ors af!er 0enef.a+ ,a!a

e-.)ange

/s!ma!or A

/s!ma!or

B

Oer+appng

Areas



2%

)ase(. Impact on 1e!Measurement lacement $%&

•+uppose the pro$a$ilit" of accidents in the +(ADA

on station of $3 is extremel" high

•+"stem $ecomes uno$serva$le and traditionall" at

least one ne# measurement has to $e installed.

•;ith data exchange- such a ne# measurement is

not necessaril" needed.

<hen we follow the data exchange scheme suggested in 3ase ,state estimation in A can be run normally because the estimation

result on b1 and b8 is exchanged from ! to A &! is still observable

even under such an accident'.



2$

)ase,. Impact on 1e!Measurement lacement $'&

•+uppose A #ants to improve the estimation

accurac" on $<.

•rom a traditional measurement placement

vie#point- there are $asicall" t#o alternatives:improve the accurac" on measurement <23 or <2=.

•;ith data exchange- it is $etter for A to invest on

measurement <23 instead of on measurement <2=.If the accuracy of 8"1 improves, the accuracy of ! also

improves with data exchange in 3ase.

It maes sense for ! to share part of the cost with A.



22

)onclusions on Topic% $%&

•+elected data exchange improves the estimator *ualit" of

individual entities on $oth estimation relia$ilit" and accurac".

•'enefit of different data exchange can $e *uite different:/roperly selected data exchanges will enable the local

distributed estimator perform as well as the one estimator for the

whole system in both $% reliability and accuracy.

/oorly designed data exchanges, which does not follow ourdesign principles, may be harmful to local estimators.

•Data exchange has an impact on ne# measurement design



23

)onclusions on Topic% $'&

•9roposed expert s"stem is useful in:(esign of the data exchange scheme

ew measurement placement decision(etermination of the maret price for date

exchangeewly proposed distributed $% algorithm



24

Topic' State estimation on Mega-+TO

• >ow to avoid the disadvantages of #ne $tate %stimator&#$%' in )ega"*T#?

>uge investment and maintenance cost

/oor performance because of the si+e of system

<aste of existing local state estimators

• >ow to avoid the disadvantages of existing distributedstate estimation &($%' algorithm?

@ow bad data detection ability

@ow estimation accuracy on

boundary buses

!ottlenec issues on central

controlling node

RTO A

RTO DRTO C

RTO B

Mega-RTO

Whole System



25

)oncurrent Textured DSE Algorithm

• $tep1. $elect a set of real time instrumentation data to be exchangedbetween neighboring entities.

• $tep. $elect a set of estimated data to be exchanged betweenneighboring entities.

• $tep. Taing the exchanged instrumentation data into account,multiple local estimators distributed in different entities are executedsimultaneously and asynchronously until they converge individually tothe desired tolerance.

• $tep7. In view of the exchanged estimated data, modify the

estimation result of local estimators accordingly and re"run bad dataanalysis.

• $tep8. !ased on the modified results of local estimators, finallydetermine the state of whole system according to the differentaccuracy and reliability of estimators.



26

Ad4antages O0 1e! Algorithm

• >igher bad data detection ability

• >igher estimation accuracy on boundary buses

• Avoid central controlling node

• 2aster speed after removal of recursive process fromoriginal textured algorithm

• )ore flexible and economic where current existingestimators can be fully utili+ed

• The performance of individual existing estimatorsimproves as well. Accordingly, they are more willing toshare the information for their own benefits evenwithout the estimation on whole system.



27

Textured DecompositionFor Step% and Step '

• Two main rules in Topic1 are proposed to search for

the estimated data0instrumentation exchange.

• /oorly designed data exchanges, which did not follow

our design principles, may be harmful to localestimators.

• /roperly selected data exchanges will enable the local

distributed estimator performance almost as good asone estimator on the whole system in both estimation

reliability and estimation accuracy.

• *efer to Topic1 for details



28

Sparse Techni5ue In Step,

• $parse Techni6ue

• Application

where the dimension of R new

is much lower than that of G

and are nown already

• $tep 7 is no longer time"consuming

$$&( −−=+ A MaN A

T $$$$$(

−−−−−+− A N M A N a M A

T T

⇒

+

=

newnewnew e

e

xh

xh

z

z

&(

&(

( ) ( $$$$newnew

T new

T newnew

T newi z R H z R H H R H G x ∆+∆+=∆ −−−−

( $ z R H

T ∆− $−G



29

Determination o0 State O4erThe 6hole 7rid in Step

• (etermine the angle difference of reference buses between any

two local estimators:

• $elect a reference bus of one estimator as global reference bus• (etermine the angle difference between this global reference

bus and reference bus of any local estimator:

• %stimated angle of local estimator 3 is subtracted with• 2or overlapping bus i belonging to multiple local estimators:

((( $'

$'

$'

$''' ∑∑

∈

−−−−

∈

++−=∆ I i

Bi Ai Bi Ai Bi

I i

Ai AB ccccθ θ θ

BC AB AC θ θ θ ∆+∆=∆

∑∑=

−

=

−=m

i K i

m

j K i K ii j j j

cc x x$

$'

$

$'' (

AC θ ∆



3%

Estimation Accuracy and#oundary Discrepancy

/s!ma!or A

Da!a /-.)ange Area

/s!ma!or B

•(erivation .1 p.u. on meas. 8"

•%stimation accuracy increases

compared with existing ($% while

boundary discrepancy decreasesfrom .7 in existing ($% to

. in textured ($%

A+gor!)mOS/ /-s!ng

DS/

Te-!*re,

DS/

,era!on%1%%3 %1%%7 %1%%4

Ta0+e $1 /s!ma!on Res*+! Dera!on

2θ

g1$ o.a+ es!ma!ors

af!er raw ,a!a e-.)ange



3$

#ad Data Detection Ability

• +tep3. A in ig.3 is executed and 3 and < are identified incorrectl" as $ad data.

• +tep1. +imultaneousl"- ' in ig.3 is executed and 32< and <23 are $othidentified as $ad data successfull" one $" one.

• +tep6. The corrected values on 32< and <23 are exchanged from ' to A- Andthese values are treated in A as pseudo measurements #ith particular highaccurac" and relia$ilit".

• +tep4. Taing the ne# pseudo measurements into account- A modifies its o#nestimation result and re2run $ad data anal"sis. This time 32< and <23 are $othidentified successfull" as $ad data.

Ta0+e 21 orma+e, Res,*es or o.a+ /s!ma!or A an, B>r2

de2

r

A in ig.3 B in ig.3 A in ig.3 after estimated

data exchange

Meas. Max.

&esidue

Meas Max.

&esidue

Meas. Max. &esidue

3 1 =?.@< 5-1 ? 5-1 ?4

15 <@.4 1-5 ?4 1-5 @4



32

)onclusion on Topic'

• The determination of state over )ega"*T# becomes verychallenging due to its si+e. Instead of starting a totally new estimatorover the whole grid, a distributed concurrent textured algorithm isproposed, where the currently existing state estimators distributed in

different companies0I$#s0*T#s are fully utili+ed.

• The new algorithm is based on some extra communication for someinstrumentation and estimated data exchange, and such an algorithmis non"recursive, asynchronous and avoids central controlling node.Therefore, it is fast, flexible and practical.

• /erformance of each estimator improves greatly via data exchangewhen some principles are applied carefully. And the state of wholesystem can be determined directly based on the result of currentdistributed estimators almost without any loss of accuracy andreliability compared with integrated $%.



33

+e0erences

B3C Garng M. Huang and +.2(. Hsieh- ast Textured Algorithms for >ptimal

9o#er Deliver" 9ro$lems in Deregulated Environments- IEEE Trans. on

Power Systems, 0ol. 36- 5o. 1- pp. 4@62<FF- Ma" 3@@?.

B1C Garng M. Huang and Jiansheng Lei- Measurement Design and +tate

Estimation for Distri$uted Multi2!tilit" >peration- 5orth American 9o#er

+"mposium 1FF3- pp. <F42<F@- >cto$er 1FF3.

B6C Garng M. Huang and Jiansheng Lei- Measurement Design of Data Exchange

for Distri$uted Multi2!tilit" >peration- IEEE PES W!""! - Januar" 1FF1.

B4C Garng M. Huang and Jiansheng Lei- A no#ledge 'ased Data Exchange

Design for Distri$uted Mega2&T> >perations- Probab#$#st#% et&o's

A$#e' to Power Systems !""! - +eptem$er 1FF1.B<C Garng M. Huang and Jiansheng Lei- A (oncurrent 5on2&ecursive Textured

Algorithm for Distri$uted Multi2!tilit" +tate Estimation- IEEE PES S!""! -

Jul" 1FF1.



34

Than"s8

An" comments are highl" appreciated.

3ontact %mail: leiBtamu.edu

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