Transcript Smart grid measures to reduce losses in distribution feeders and

Frankfurt (Germany), 6-9 June 2011
Smart grid measures to reduce losses in
distribution feeders and increase capacity
to integrate local small hydro generation
Astrid Petterteig, SINTEF Energy Research, Norway – Paper 0840
Presented by Dag Eirik Nordgård, SINTEF Energy Research
1
Frankfurt (Germany), 6-9 June 2011
Common DG situation in Norway
Small hydro power plants (1 - 10 MVA)
in areas with low consumption and weak lines
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Generation much higher than local consumption
Strongly varying generation (river plants without water storage)
Long feeders and high voltage levels when the generation is high
 Generators consume reactive power to reduce line voltage
Frankfurt (Germany), 6-9 June 2011
Measurements
12,0
Active
power
Ps
09-10
Reactive
Qs
09-10 power
8,0
4,0
0,0
1
1281
-4,0
-8,0
-12,0
Jan March May
July
Sept
Nov
Jan March May
July
Sept
Nov
Measured power flow into feeder with several DG units - 2 year
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Frequent changes in power flow
Seasonal variations in power generation:
High generation when consumption is low & Low when consumption is high
Reactive power flow increases with increasing active power generation
Frankfurt (Germany), 6-9 June 2011
Measurements
12,0
Active
power
Ps
09-10
Reactive
Qs
09-10 power
8,0
4,0
0,0
1
1281
-4,0
-8,0
-12,0
Jan March May
July
Sept
Nov
Jan March May
July
Sept
Nov
Measured power flow in three different networks for 2 and 3 years:
Case I DG unit producing 2.1 MW and consuming up to 1.1 MVAr
 Case II
Measured: 7.1 MVAr into with 11.4 MW out of feeder
 Case III Measured: 2.8 MVAr into with 5.7 MW out of feeder
Reactive power flow increases with increasing active power generation
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Frankfurt (Germany), 6-9 June 2011
Reactive power flow strategies analysed:
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Two simplified feeders analysed
In different load conditions:
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
Compare three strategies for reactive power generation:
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Low load & high generation – Production limited by maximum line voltage
High load & low/med. generation – Frequently occurring, no line voltage issues
Qdg = 0 All DG units run with zero reactive power
Qdg < 0 One or more DG unit consumes reactive power
Qs = 0
Coordinated control of reactive power
Focus on feeder losses, Maximum line voltage and flow in sub-station
Is
Qs
U
Frankfurt (Germany), 6-9 June 2011
Coordinated control of reactive power
In networks with several synchronous generators:
 Generator(s) at the end of feeder consumes reactive power
 Generator(s) close to sub-station produces reactive power
Goal:
 Minimize flow of reactive power (Qs) and sub-station current (Is)
 Reduce feeder losses (compared to strategy with Qdg<0)
 Maximize active power generation without violating voltage limits (∆U)
 Can increase active power generation (compared to Qdg=0)
 Utilize existing network (postpone reinforcement)
without increasing losses and reactive power flow
Is
Qs
U
Frankfurt (Germany), 6-9 June 2011
Illustration – High generation & low load:
Line
voltage – 20
(FeAl
120), 2 MW load
Linjespenning
- 2km
MWfeeder
last, 20
km FeAl120
22,88
Qs [kVAr]
22,66
22,44
16MW
Qdg=0
16MW
Qdg=0
13MW Qdg=0
16MW Qdg=1,4 koord.
Coordinated
13MWQdg=-0,6
Qdg=0
16MW
16MW Qdg=-0,6
16MWQdg=0
Qdg=0
13MW
13MW
Qdg=0
22,22

22,00
Stasjon 2
Reactive power
flow into feeder:

4
6
8
10
12

14
16
18

20 km
2.000
1.800
1.600
1.400
1.200
1.000
800
600
400 Qs=0
200
0
16MW Qdg=1,4 koord.
16MW Qdg=-0,6
16MW Qdg=0
7
13MW Qdg=0
Frankfurt (Germany), 6-9 June 2011
Paper conclusion:
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Synchronous generators can easily contribute in voltage control
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Necessary in many networks  Large flow of reactive power
Common strategies for reactive power generation:
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
Qdg=0  High line voltages & Low losses
Qdg<0  Low voltages & High losses & High Qs into feeder
Coordinated reactive power control is suggested
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
when generation is high & consumption is low
in many other frequently occurring operating situations
 Sub-station reactive power and current is reduced compared to Qdg<0
 Active power generation can be increased compared to Qdg=0
with almost the same maximum line voltage as with Qdg<0
Calculated loss reduction up to 20 %
.... More efficient measures as line reinforcement can be postponed!