ACROSS&BORDERS&*&HVDC&SYSTEMS&AND&MARKET&INTEGRATION&
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PAPER 263
2.6. Modeling and Dynamic Performance Aspects of
Integrating HVDC into the AC Power System
Analysis of the AC Polish Power System Impact on the
HVDC SwePol Link Operation
M. Przygrodzki, P. Rzepka, M. Szablicki, W. Lubicki
Poland
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HVDC CONNECTION SWEDEN-POLAND
The HVDC SwePol Link connection between Poland and Sweden was
establish in 2000 year. It consists of the following elements:
•  AC 400 kV overhead line with length equal to 0,2 km, between the
Karlshamn substation and Starno converters,
•  HVDC 450 kV cable line which comprises:
–  2-kilometer on-shore cable section on the Swedish side,
–  241-kilometer section of the submarine cable,
–  12-kilometer on-shore cable section on the Polish side
•  MVDC 24 kV return cable line which analogously consists of:
–  2-kilometer on-shore cable section (in fact two cables connected in parallel)
on the Swedish side,
–  241-kilometer off-shore cable section (two cables in parallel),
–  12-kilometer on-shore cable (single cable) on the Polish side,
•  Converter station and the AC 400/110 kV Wierzbięcino Slupsk
station
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COMMUTATION FAILURE
•
•
•
The thyristor is turn on with the firing angle (α) and turns off when the external voltage
enforce zero with its anode current. The process of this switching is known as a
commutation.
The duration of the commutation is determined by the commutation/overlap angle µ.
The angle is proportional to the transmitted current. The effectiveness of reverse
polarity must be maintained for a certain period of time referred to as a voltage-time
area measured by the duration of the extinction angle γ.
Insufficient voltage-time area is resulting in commutation failure. In this case no
blocking thyristor causes that conduct thyristors in the same branch of the bridge - the
effect of short circuit.
commutation
kąt
komutacji angle
obszar czasowo voltage-time
napięciowyarea
α
µ
γ
zapłon
firing
iS
iR
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prądy
zaworu
thyristor
current
3%
THE STATISTIC OF COMMUTATION FAILURE
Commutation failure have occurred 204 times during over than 13 years of HVDC Link
operation (till end of may 2013)
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4%
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THE STATISTIC OF COMMUTATION FAILURE
The monthly number of identified commutation failures estimated from the beginning of
HVDC Link operation to the end of year 2013
57
60
50
40
30
21
23
21
19
20
12
10
7
19
9
8
7
1
0
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5%
THE STATISTIC OF COMMUTATION FAILURE
The yearly correlation coefficient was equal to 0.57 which confirms the strong
dependence between variables (import duration and number of CF).
The monthly number of identified commutation failures accompanying imports of energy
to Poland.
60%
70,0%%
50%
60,0%%
50,0%%
40%
40,0%%
30%
30,0%%
20%
20,0%%
10%
10,0%%
0%
0,0%%
Number%of%CF%
Percentage%of%energy%import%
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6%
The average number of failures in the observed period of time is 0,39 CF/100 h. This
means that a single failure falls on 256 importing hours which is an equivalent of 10.7
days of energy import.
The year 2010 was identified as the worst year in terms of failures frequency per 100
hours of import. Frequency index is 1.3 and it is a result of 31 commutation failures
related with 2 392 importing hours.
•
1,40
1,20
1,00
0,80
0,60
0,40
0,20
0,00
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
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7%
THE AC NETWORK ENVIRONMENT
0
6
P303
E
19
B
P4
1
P47
7
P4
N4
01
N40
A
6
P4
6003
P30
P3
D
04
3A
9
Kiełpino
N0
6B
Olsztyn
Mątki
Swarożyn
Zajączkowo
C
Kobylnica
Szczecinek
A1
Dunowo
T2
T1
P632
Jeżyce
218
XSD
Morzyczyn
P633
FW Darłowo
A1
A2
Żydowo
Piła
Krzewina
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Jasiniec
Grudziądz
8%
03
Bystra
P303F
03
P3
Gdańsk
Błonia
11
Dębnica
Kaszubska
T2
T1
4
P4
Gałęźnia
Mała
B
T2
N002
XYZ
P010
8
P304
A2
17
P30
4C
9
P00
Białogard
2
P6
P316
Bytów
Obłęże
Żydowo
Dygowo
P3
Miastko
P017
Karścino
P310
P320
P304E
3
P6
P6
3
P313
Tychowo
Słupsk
Szczecińska
P315
P314
6601
P601
Tymień
Sianów
Koszalin
Południe
P608
P629
Ostrowite
T1
Żarnowiec
2
Koszalin
Przemysłowa
P611
B
05
Koszalin
Strefa
Koszalin
Północ
Słupsk
Hubalczyków
07
6001
5A
Koszalin
Morska
P617
P3
Słupsk
Poznańska
P304A
0
P6
07
Sławno
A1
A3
Gdańsk 1
P303
P616
P6
P6
Dunowo
Ustronie
Morskie
09
Słupsk
Grunwaldzka
P301
P612
P6
2A
2B
Kanin
P409
P311
Słupsk
08
P0
Rumia
Darżyno
P302
0
P3
01
N0
Chylonia
44
P4
1
4A
Reda
P4
3
2
P0
Darłowo
A1
Słupsk
P3
1
Boże
Pole
0
N4
K
2
P31
IN
-L
4B
07
P307B
DC
2
P0
Pieńkowo
P0
Lębork
Krzywoustego
Ustka
Władysławowo
P
Wejherowo 463
7
SZWECJA
10
1
P4
Lębork
Nowy
Świat
Gnieżdzewo
Łebcz
Gnieżdzewo
P4
Żarnowiec
P319
N004
7
Opalino
Wojciechowo
Wicko
9
P419A
P46
P022B
C
P022
41
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•
5
P30
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THE STATISTIC OF COMMUTATION FAILURE
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THE CASE STUDY
It is has become important to discover mechanism of causes and sequence of
events implying commutation failures. Transmission and distribution grid
structure changes, HVDC Link parameters changes as well as connection of
new wind farms should be included when defining a set of analyzed events.
Accordingly, in process of selection events the following criteria were included:
•  phenomenon occurrence on the Polish side of the HVDC SwePol Link
(registered by the recorders),
•  events should occur during inverter operation mode of the HVDC SwePol
Link (power import from Sweden),
•  excluded events are these one resulting from functional disruption of HVDC
Link internal structure (switch failures, control system failures, etc.),
•  commutation failures and associated possible outages should results from
random events (within grid) and should not be the result of control system
failures (eg. transmission direction change, LLD – Last Line Disconnect),
•  in the area of interest are commutation failures associated with transmission
network disturbances (automatic reclosing cycle operation, low level of short
circuit power, voltage reduction).
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THE EVENT 26 JULY 2012, HOUR 13:52:28
The HVDC Swe-Pol Link worked in the import mode with the load of 600 MW.
The reason for the existing problems of commutation was close to ground fault
located at the L1 phase 400 kV line Dunowo - Morzyczyn. As a result, it
occurred on both sides off the line in the automatic reclosing cycle.
Switchgear breakdown in TR1 bus
of 400 kV Żarnowiec substation
11:16 12:29
12:34 13:30
60 MW HVDC SwePol Link
import decrease
Commutation failure
in HVDC SwePol Link
13:52
14:21 20:55
Dunowo-Morzyczyn 400 kV line
disconnection in open-close-open
cycle of automatic reclosing
Disturbance in CHP
Bydgoszcz
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10%
Voltages and currents measured on the DC-LINK Slupsk substation
4
400
L1
L2
L3
300
100
1
i![kA]
2
0
0
-1
-100
-2
-200
-3
-300
-400
L1
L2
L3
3
200
-4
13:52:28.598
+0,5 s
+1 s
13:52:28.598
+0,5 s
+1 s
t![s]
t![s]
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11%
Uh/U1hL3$[%]
Uh/U1hL2$[%]
Uh/U1hL1$[%]
THE EVENT 26 JULY 2012, HOUR 13:52:28
2.5
0.5
13:00
2.5
Ih/I1hL1$[%]
13:20
13:40
14:00
14:20
13:20
13:40
14:00
14:20
13:20
13:40
14:00
14:20
13:20
13:40
14:00
14:20
13:20
13:40
14:00
14:20
13:40
14:00
14:20
1.5
The content of voltage (U) and current
(I) harmonic (10-minutes) registered at
the DC-LINK Slupsk substation
0.5
13:00
2.5
1.5
0.5
3.5
2.5
1.5
0.5
13:00
4.5
Ih/I1hL2$[%]
zdarzenia
1.5
13:00
4.5
3.5
2.5
1.5
0.5
13:00
4.5
Ih/I1hL3![%]
u![kV]
ACROSS&BORDERS&*&HVDC&SYSTEMS&AND&MARKET&INTEGRATION&
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THE EVENT 26 JULY 2012, HOUR 13:52:28
3.5
2.5
1.5
0.5
13:00
13:20
t![h]
3h
5h
7h
9h
11h
13h
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12%
THE EVENT 26 JULY 2012, HOUR 13:52:28
DL
DN
0
U![kV]
-100
-200
-300
-400
-500
13:52:28.598
+0,5 s
+1 s
t![s]
8
DL
DNC
I![kA]
6
4
2
13:52:28.598
+0,5 s
+1 s
t![s]
160
α
γ
µ
120
80
40
0
13:52:28.598
+0,5 s
t![s]
ACROSS&BORDERS&*&HVDC&SYSTEMS&AND&MARKET&INTEGRATION&
Time duration curves of selected
HVDC Link parameters during
commutation failure:
•  voltage (UDL) and current (IDL)
of the main cable,
•  voltage (UDN) and current
(IDNC) of return cable,
•  thyristor firing angle (α),
extinction angle (γ) and
commutation/overlap angle (µ)
0
α ,!γ,!µ![o]
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100
+1 s
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13%
SUMMARY
•
•
The Slupsk station was built as a line-commutated converter. Thus, the
direct cause of commutation failures (including elimination of incorrect
control system behavior) is an voltage distortion at the output side of the
inventor, resulting in a reduction of voltage-time area of commutation
process. The primary cause of voltage distortion and thus commutation
problems are switching operations – in particular – short circuit faults and
automatic reclosing operations. This thesis is confirmed by the results of the
retrospective analysis. HVDC SwePol Link malfunction was caused mainly
by asymmetrical transient (eliminated in automatic reclosing cycle) or solid
short-circuit faults located in transmission or 110 kV network.
For cases of single-phase voltage reduction in Slupsk substation it occured
problems at HVDC connection work. It was a multiple commutation failures.
The occurrence of multiple commutation failures much more negative
impact on the stability of the whole network system than the individual
commutation failure.
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SUMMARY
•
•
On the basis of the results of tests carried out for the analysis of single and
multiparameter network system with a HVDC Swe-Pol Link it has been
found that the occurrence of commutation failures dynamic switching
accompanied by large changes in the electrical parameters in both the AC
part of the Swe-Pol Link or in DC part. The results determine that the
stability of working conditions through during switching operations, faults
and reclosing cycles is determined by, among others, short-circuit power
level, the value of voltage and phase angle in the inverter station, the level
of power transmission and the control of the rectifier and inverter link. A
special aspect for the stability of HVDC SwePol Link is voltage on the
substation (including its amplitude and angle).
The converter station location on the Polish side does not guarantee a
stable network parameters during - even distant – disturbances in the
transmission and 110 kV network. In particular this applies to the northwestern part of Polish Power System. Therefore there is a need for research
to indicate a network investments (including the optimal development
process) which could reduce the likelihood of short circuit faults.
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