Transcript Some Results of the Study

Some Results of the Study
„Integration Possibilities of Wind
Energy with the Polish Power Grid”
Carried Out by IPE for PPGC in
2002-2003
INSTITUTE OF POWER ENGINEERING
GDAŃSK DIVISION
[email protected]
 Study has originated from strong interest in wind
energy which has been observed in Poland although
working wind installations are still below 100 MW
 Wind energy developers have made applications for
about 5000 MW total and due to law regulating grid
connection, PPGC and distribution utilities are obliged
to take position to each connection request without
checking financial credibility of the applying customer
 The study has had technical, economical and legal
objectives. Only the technical ones will be included in
this presentation. Economical and legal conditions are
under continuous changes and the results of the study to
some extent have lost their validity.
2
Technical Goals of the Study
 Assessment of maximum wind generation which
could be absorbed by the Polish power system without
substantial grid investments
 Indication of wind investments enabling high wind
penetration
 Investigation of operational problems in the Polish
power system resulting from high wind penetration
 Proposals of technical requirements for wind farms
connected to HV and EHV grids
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Input Data and Evaluation Criteria
 The results of this kind of system study depend on
input data and applied criteria
 Model (location, power, type of WT) was established
based on information obtained from the distribution
utilities. Thanks to weather conditions and siting
availability the north-western Poland along Baltic shore
seems to be area of probable wind energy development
 Other results of data collection: most of wind power
will concentrate in large farms connected to HV and
EHV grids, use of modern WT with DFIG will
dominate
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Input Data and Evaluation Criteria
„Planned” and
„considered” WFs
Distribution of WF
size
60
% of total wind generation
50
40
planned WF
30
considered WF
20
10
0
<10
<10,20>
<20,30>
<30,50>
pow er range MW
<50,100>
>100
Geographical distribution
of wind farms
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Input Data and Evaluation Criteria
 Powerflow data elaborated for 2005 and 2010 for light and
peak load conditions were used. Two models of WG were used
(„R” based on received data and „F” fictitious one where WG
was connected to HV/EHV stations
 The basic criterion for integration capability was occurrence of
overload in the grid
 The n-1 criterion was not applied as a strict rule. This responds
to the situation where wind generation is treated as a „non-firm”
generation which may be reduced or lost in „n-1” conditions at
specific contingencies by applying so called remedial action
schemes (RAS)
 Criteria given in the Polish grid codes were used in other
operational aspects for instance voltages profiles
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Maximum Wind Capacity Due to Thermal
Ratings
Wind generation model F, w ithout grid investment
Wind generation model R, w ithout grid investment
Distribution grid investments
New EHV/HV transformers; model RP
EHV netw ork investment, export or hydro storage of
pow er needed
Large w ind farms in central Poland
New 400kV line connecting northern rail w ith central
Poland
Second circuit of 400kV northern rail
0
1
2
3
4
5
6
7
8
9
GW
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Operational Aspects Associated with High
Wind Penetration
Operational aspects were investigated on the „R” model
of 4000 MW of WG. The following issues were
considered:
 Capacity reserves of regulating power
 Control of line loadings
 Regulation of voltage and reactive power
 System automatics
 Short Circuit power
Dynamic and transient stability
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Operational Reserves of Regulating Power
 It was found that in the Polish power system being a part of
UCTE unexpected wind gradients would not be the main problem
 Due to the specifics of the north-western grid more serious
will result from lost of WG after fault in the EHV grid. Up to
60% of WG can be lost due to fault on some EHV grid locations.
 There is a strong need for appropriate regulations (setting of
undervoltage protections and „ride through fault” capability for
large WFs)
4000
3500
3000
lost MW
2500
2000
1500
1000
500
0
U<0.5
U<0.6
U<0.7
U<0.8
U<0.9
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Control of Line Loads
 At present intact conditions loadings of transmission grid in
the north-western Poland do not exceed 50%. 4000 MW of WG
can increase loading of some elements to 90% and during
contingencies many overloads was observed.
 Wind generation cannot be treated as a firm generation from
economical reasons. Its average productivity is around 25% and
additional transfer capabilities will be exploited in small degree
 HVDC link and pump storage hydro stations located in the
north have some potential for avoiding overloads
 It was observed that connection with Germany tend to be often
overloaded (?)
 RAS can be very efficient way to master the problem
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Regulation of Voltage and Reactive Power
 Usually cos=1 is required from WT. At high wind penetration
this result with MVAr shortage. At low production problem with
too high voltages in transmission grid can be observed (when
local load is balanced by local generation)
 Some range of Q generation/consumption in WG connection
points is then required. 0.975 ind/cap range demanded by E.ON
was used in powerflow calculations and ensured satisfactory
voltage profiles. It is more than a standard DFIG WT can
provide.
0.4
1.12
0.3
1.11
1.1
0.1
12MW
0
50MW
-0.1
0
10
20
30
40
50
60
60MW
20MW
-0.2
30MW
-0.3
50MW(1)
Voltage p.u.
tg()
0.2
1.09
KRA4
1.08
DUN4
1.07
ZRC4
1.06
GBL4
1.05
1.04
-0.4
1.03
-0.5
1.02
0
-0.6
MW
5
10
15
20
25
30
35
w ind farm output as % of their rated pow er
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System Automatics
 VAR and voltage control installed in EHV/HV stations
should involve large WFs with Q,U control capabilities, which
are directly connected with the stations. This solution is better
than installing compensating batteries
 Grid operators assisted by automatics should initiate RAS to
avoid overloadings. The automatics can also be installed in
EHV/HV stations.
 Algorithms of out-of-step protection automatics (APKO)
which preserve global dynamic stability of the northern grid must
be revised when large WF will have to be connected
 TSO uses EMS. Evolution of EMS toward on-line calculation
capabilities encompassing various operational aspects of grid
operation is desired. It would allow safer integration of large WG
with the Polish grid.
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System Dynamics
 Experience of countries with large wind penetrations
shows that WG concentrated in MV and HV is not
critical for dynamic transient and small signal stability.
Nevertheless some deterioration of low frequency
oscillation damping was reported
 Main danger for dynamics results from eventually
lost WG during EHV faults
 Other danger is connected with lowering of system
inertia
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1.0100
1.0100
1.0100
1.0060
1.0060
1.0060
1.0020
1.0020
1.0020
0.998
0.998
0.998
0.994
0.994
0.994
0.990
0.990
0.000
1.6000
3.2000
4.8000
6.4000
.. 8.0000
0.990
0.000
DOD4-B78: Speed in p.u.
ZRC-B1234: Speed in p.u.
1.6000
3.2000
4.8000
6.4000
.. 8.0000
0.000
DOD4-B78: Speed in p.u.
ZRC-B1234: Speed in p.u.
1.1000
1.1000
1.0500
1.0400
1.0400
1.0000
0.980
0.980
0.950
0.920
0.920
0.900
0.860
0.860
0.850
0.800
1.6000
3.2000
4.8000
6.4000
.. 8.0000
DOD4-B78: T erminal Voltage in p.u.
ZRC-B1234: Terminal Voltage in p.u.
IEn Gdansk
1.6000
3.2000
6.4000
.. 8.0000
6.4000
.. 8.0000
0.800
0.000
1.6000
3.2000
4.8000
6.4000
.. 8.0000
DOD4-B78: T erminal Voltage in p.u.
ZRC-B1234: Terminal Voltage in p.u.
0.000
1.6000
3.2000
4.8000
DOD4-B78: T erminal Voltage in p.u.
ZRC-B1234: Terminal Voltage in p.u.
Speed and voltage of two system generations connected to the northern rail
fault in central Poland
4.8000
DOD4-B78: Speed in p.u.
ZRC-B1234: Speed in p.u.
1.1000
0.000
DIgSILENT
System Dynamics
left - wind farms; middle - conventional; right - no extra generation
All
Date: 20.05.2003
Annex: /4
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Technical Requirements for Wind Farm
Connection
 Proposals of such requirements taking into account
already issued E.ON and ELTRA regulations and some
other TSOs drafts as well as specifics of the Polish
Power Grid were elaborated
 Compatibility with other regulations
 Due to the specifics of the Polish grid and probable
model of wind energy development limitations can
occur at rather low wind penetration
 Importance of problem of Q,V regulation and staying
grid connected during faults
 Possibility of WFs active power control
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Some Conclusions
 IPE performs many so called „WF connection expertizes”.
Nowadays over 4000 MW of WG is considered in detailed
powerflow calculations. Obtained results are compatible with
results of the presented study
 Level of WG present in government plans (< =2000 MW) can
be reached without major investment in the grid but connected
WFs must have some Q, V and active power regulations
possibility
 We see strong need for publishing WF connection
requirements by the Polish TSO.
 It would be desired to find out the Polish TSO attitude toward
using RAS in case of WFs
 Many planned WFs have valid rights to be connected to the
grid. Low quantity of working wind installations result mainly
from economical reasons (Euro/Zl rate) and other than grid
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connection regulations