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WITH FUNDING FROM:PART OF:
” Using Machine Learningfor Detection and Classification of
PQ phenomenon”
byDr. Peter Axelberg 2016
byDr. Peter Axelberg 2016
WITH FUNDING FROM:PART OF:
Power Quality monitoring from past until today
1990 2015
1st generation
• Very basic instruments likevoltmeters etc were used.
• First portable power qualityanalyzers were introduced
2nd generation
• Permanent installed powerquality analyzers wereintroduced.
• Power quality analyzers based onIEC 61000-4-30 class A wereintroduced
3rd generation
• Sophisticated signal processingmethods are ued for automaticand accurate analysis ofmeasurement data
• Integration
2000
WITH FUNDING FROM:PART OF:
3rd generation measurement system - objectivesOnly characteristics
Tell what really happened
Something happen inthe grid
Manual Analysis ofrecorded data
3rd generation
”Classical”
” Preferred”
WITH FUNDING FROM:PART OF:
• In the past: Evaluation of data was made by manual inspection- Time consuming (and tedious)- Quality of the result depends on the knowledge level and skills of the persondoing the analysis
• 3rd generation: Take use of information (data) from previous measurements to automatethe evaluation process
- Automatic detection and classification of power quality phenomenon- Less time consuming evaluation process- Higher quality and more reliable results- Important information contained in the data - hidden for a manual inspection – can
be detected – Trend analysis- Adaptive process – by continuously adding new data from previous measurements
into the machine learning algorithm the PQ system will continuously learn andincrease the precision and accuracy
- Opens up to use the PQ system in new valuable applications like fault detectionand preventive maintenance etc
Power Quality Monitoring – 3rd generation
WITH FUNDING FROM:PART OF:
Machine learning (ML)
q Herbert Simon:”Learning is any process by which asystem (computer,robot etc) improvesperformance from experience”.
q Machine Learning is concerned withcomputer programs that automaticallyimprove their performance throughexperience
WITH FUNDING FROM:PART OF:
Pattern recognition:A machine learning algorithm that is trained to recognizea particular pattern in a large data stream
Pattern recognition
WITH FUNDING FROM:PART OF:
Pattern recognition –a general technique used in many applications
- Text analysis: Search engines- Image analysis: Face recognition- Financial analysis: Stock price forecasts- Power system analysis: Detection and lassification of voltage disturbances
fault detection and classificationspreventive maintenancetrend analysis, forecasting
WITH FUNDING FROM:PART OF:
Many pattern recognition methods are available (differenttechniques with the same goal – to identify a particularpattern in a data stream)
- k Nearest Neighbor (kNN)- Neural Networks- AdaBoost- Support Vector machines
Pattern recognition methods
WITH FUNDING FROM:PART OF:
q Uses large number of pre-classified training data.q Features are extracted from the training data and placed in an n-
dimentional data space.q The classifier decides type of disturbance (class) by using an
optimal separating hyperplane.
A premium method:The Support Vector Machine (SVM)
WITH FUNDING FROM:PART OF:
x1x2
x3Real world
Binary classifierFeature extraction
Trainingdata
Testdata
Class +1y = +1
îíì
-®<+®³
=1class01class0
)( xf
Class -1y = -1
Separating hyperplane f(x)(decision boundary)
Training data vector [x1, x2, x3]
Test data vector x = [x1, x2, x3]
A premium method:The Support Vector Machine (SVM)
WITH FUNDING FROM:PART OF:
w
separating hyperplanef(x) = (w×x)+b
wb
d(w,b) margin(w×x)+b=+1
(w×x)+b= -1
11)( +=³+× ii yforbxw
11)( -=-£+× ii yforbxw
niby ii ,...,11))(( =³+×× xw
bf +×= )()( xwx
The margin
( ) ( )ww
xwwxw
w 2),( 21 =+×
++×
=bb
bd
Maximum margin is achieved for2
21min w
w
niby ii ,...,11))(( =³+×× xwQuadratic Optimization problem (QP-problem)
Calculating the separating hyperplane
x1
x2
WITH FUNDING FROM:PART OF:
2
21min w
w
niby ii ,...,11))(( =³+×× xw
Introduce the Lagrangian functional and re-formulate the QP-problem:
( )[ ] åå åå== ==
+-×××-=-+××-=n
ii
n
i
n
iiiiii
n
iiii ybybybL
11 1
2
1
2 )(211)(
21),,( aaaaa xwwxwww
Optimal solution is given by the saddle point of the Lagrangian functional
÷øöç
èæ ),,(minmax
,a
abL
bw
w
åå==
=Þ=-=n
iii
n
iii yy
dbbdL
11
00),,( aaaw
åå==
=Þ=-=n
iiii
n
iiii yy
dbdL
110),,( xwxw
ww
aaa
å
å å
=
= =
=³=
÷÷ø
öççè
æ×-=
n
iiii
jij
n
i
n
jiijii
niandy
yybL
1
1 1,
,,100
sconstraintthetosubject
)(21max),,(max
Kaa
aaaaaa
xxw
Calculating the separating hyperplane
WITH FUNDING FROM:PART OF:
w
wb
margin (w×x)+b=+1
(w×x)+b= -1
For the binary classifier
( ) ÷ø
öçè
æ+×=+×= å
=
n
iiii bysignbfsignf
1)()()( xxxwx a
Karush-Kuhn-Tucker conditions states
( )( ) niforby iii ,...,101)( ==-+× xwa
Only those training samples corresponding to non-zero Lagrangemultipliers are needed!These are placed on the margins and called Support Vectors
÷÷ø
öççè
æ+×= å
SViii bysignf )()( xxx a
Support Vectors
÷÷ø
öççè
æ+×= å
SViii bysignf )()( xxx a
x1
x2
Support Vector Machine
WITH FUNDING FROM:PART OF:
x
x1
x2
xN
(x1×x)
(x2×x)
(xN×x)
+
Test data
Classification
Bias b
a1y1
a2y2
aNyN
÷ø
öçè
æ+×= å
Î
bysignfSVi
iii )()( xxx a
Support Vectors
Blockdiagram of the Support Vector Machine
WITH FUNDING FROM:PART OF:
Conducted experiments
WITH FUNDING FROM:PART OF:
Type Fault types # of disturbancesoriginated from Powernetwork A
# of disturbancesOriginated from Powernetwork B
# of disturbances originatedfrom synthetic generateddata
D1 Single phase-to-ground fault
141 475 225
D2 Phase-to-phase fault 181 125 225
D3 Three-phase fault 251 196 223
D4 Double phase faultwith one phase more
affected127 67 250
D5 Transformerenergizing
214 0 250
Types of voltage disturbances
WITH FUNDING FROM:PART OF:
Power network A Power network B Synthetic data
Experiment #1
D1 D2 D3 D4 D5 NC Detectionrate
Single phase-to-groundfault (D1)
63 0 1 3 0 4 88.7 %
Phase-to-phase fault(D2)
0 84 4 0 0 3 92.3 %
Three-Phase Fault (D3) 5 3 113 0 0 5 89.7 %
Double phase fault withone phase more affected(D4)
0 0 0 63 1 0 98.4 %
Transformer energizing(D5)
0 0 0 0 103 4 96.3 %
Overall detection rate: 93.1 %
SVMTraining data
Test data
WITH FUNDING FROM:PART OF:
Power network A Power network B Synthetic data
Experiment #2
SVMTraining data
Test data
D1 D2 D3 D4 D5 NC Detectionrate
Single phase-to-ground fault(D1)
137 0 2 1 0 1 97.2 %
Phase-to-phase fault (D2) 0 154 16 0 0 11 85.1 %
Three-Phase Fault (D3) 10 1 232 0 0 8 92.4 %
Double phase fault with onephase more affected (D4)
4 1 1 121 1 0 95.2 %
Overall detection rate: 92.5 %
WITH FUNDING FROM:PART OF:
Power network A Power network B Synthetic data
Experiment #3
SVMTraining data
Test data
D1 D2 D3 NC Detection rate (%)
Single phase-to-ground fault(D1)
393 0 2 23 94.0%
Phase-to-phase fault (D2) 3 80 0 9 87.0%
Three-Phase Fault (D3) 2 0 126 14 88.7%
Overall detection rate: 91.9%
WITH FUNDING FROM:PART OF:
System Integration
WITH FUNDING FROM:PART OF:
System Integration – situation until today
DISTRIBUTION GRID
DMS
SCADA AMR PQMS
Isolated system
WITH FUNDING FROM:PART OF:
Integration – situation tomorrow
DISTRIBUTION GRID
DMS
SCADA AMR PQMS
IPQMS
IPQMS = Integrated Power Quality Monitoring System
Open system
WITH FUNDING FROM:PART OF:
Conclusions
q The 3rd generation system will be based on powerful pattern recognitiontechniques to perform traditional PQ analysis in a more efficient way- from manual toward automatic analysis of PQ data- trend analysis used for preventive maintenance- automatic detection and classification of faults- forecasting
q The 3rd generation system will be an open system ready to interchangedata with other systems