Wind Farm Performance on the Grid:
Perception and Reality
WindVAR and LVRT
Data and Graphs provided by Nicholas W. Miller
GE Energy, Energy Consulting
1
GE Energy
August 2004
Wind Energy Grid Performance:
A Perception of Disruption
Transmission owners and operators have legitimate concerns
about potential adverse impacts of wind generation on the grid.
Global requirements for “WindVAR” and LVRT technology vary
by region and by project, making a global solution challenging.
This presentation provides examples of common Customer
concerns and how GE technology can help.
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GE Energy
August 2004
Recently
Advanced
Basic
Performance Requirements
Grid Requirements Evolution
Enhanced Voltage
Control
(WindVAR)
O/U Voltage
Overcurrent
O/U Frequency
Protection
Voltage control
(old DVAR)
LVRT – no trip
(e.g. Taiban, E-ON)
Curtailment
PF control
None
None
Volt/VAR
Control
LVRT
Active Power
Control
Application Characteristics
Single WTGs
Low Penetration
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GE Energy
August 2004
Large Farms
Multiple Farms
High Penetration
Grid Requirements Evolution
Advanced
Features
Features
Fancy Voltage
Control
(WindVAR)
Features
Basic
Performance Requirements
Near Future
O/U Voltage
Overcurrent
O/U Frequency
Protection
Features
Features
Features
Features
Voltage control
(old DVAR)
LVRT – no trip
(e.g. Taiban, E-ON)
Curtailment
PF control
None
None
Volt/VAR
Control
LVRT
Active Power
Control
Application Characteristics
Single WTGs
Low Penetration
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GE Energy
August 2004
Large Farms
Multiple Farms
High Penetration
Grid Disturbances
Grid Event
Wind fluctuation
affecting MW
output of wind
turbines
Grid disturbance
affecting all
generation on the
grid
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GE Energy
August 2004
Effect
Grid dynamics,
especially voltage,
are adversely
affected by wind’s
inability to provide
adequate VAR
control
Grid stability is
adversely affected
by a loss of power
generation if the
Wind Farm trips off
GE Solution
GE WindVAR
“Do not harm the grid”
GE LVRT
“Do our share to help the grid”
Reactive Power
The Sources and Sinks of Reactive Power:
Lightly Loaded
Overhead Lines
Controllable
Elements
Courtesy of National Grid Co, UK
Load System Voltage
Cable Circuits
Generators
Controllable
Elements
Capacitive
Compensators
Flow from
Other Areas
Generators
Consumer Loads
The Reactive
Power Tank
Transformers
Inductive Compensation
Heavily Loaded Overhead Lines
Flow to Other Areas
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GE Energy
August 2004
Courtesy of National Grid Co, UK
WindVAR Architecture
Voltage
Measurement
High Voltage
Transmission Line
Station
Trans former
Current
Measurement
Substation
Three Phase
System
Transducer Utility grade
relay
Windfarm
Controller
Co
3
m
SCADA Park
PC
Co
3
m
Turbi n e
Controller and
SCADA Plant PC
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GE Energy
August 2004
WindVAR & LVRT
Perception v. Reality
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GE Energy
August 2004
Perception #1
“Wind generation causes voltage flicker.”
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GE Energy
August 2004
Reality
Wind farms with GE supervisory controls provide tight voltage
regulation, effectively eliminating concerns about flicker.
Utility Voltage (%)
110
1.10
Utility Transmission Bus Voltage (pu) 200
200
1.06
160
1.02
120
Total Wind Farm Power (MW)
Total Wind Farm Power (MW)
Red with WindVAR
Black without WindVAR
0.98
80
Graph Assumptions:
0.94
Very Clean voltage on
the host utility grid bus
900.90
- Utility Voltage: point of common
coupling is 75km from the wind farm
40
0.00
0.0
300
0.0
Time (seconds)
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GE Energy
August 2004
300
Perception #2
“Wind generation does not support the system
voltage.”
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GE Energy
August 2004
Reality
GE Wind farms with can provide similar voltage regulation to that of
conventional synchronous generators.
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GE Energy
August 2004
WindVAR vs. Competitive Solutions
GEWE WindVar SYSTEM
Competitors SYSTEM
Extra VAR
Compensating
Equipment
VAR Controller
SVC
Solution #1: Static Fixed Capacitors
Each WTG Acts as VAR Source
• Incremental VAR Capability with each WTG
• Converter based fast, smooth response
• Variable speed generator smoothes both real & reactive power
• Coordinated management of substation volt/var devices by
WindVAR
•
•
•
Switched capacitors react slowly to power and voltage surges
Fixed speed turbine - gusts cause rapid real/reactive power swings
Poor stability and light flicker issues for weak grid locales
Solution #2 Static VAR Compensators (or equivalent)
•
•
Expensive but faster acting, not integrated with WTG
Mixed SVC & capacitor solution can stabilize utility grid voltages
Extra Equipment $$ and Maintenance $$ Required
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GE Energy
August 2004
Perception #3
“Wind generation cannot be relied upon, since it
trips from the grid during disturbances.”
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GE Energy
August 2004
Reality
Low Voltage Ride-Thru (LVRT) keeps wind farms on-line through
system disturbances.
Zero Voltage
on the Utility
Bus
Terminal Voltage
Factory tests
Power
recovers
quickly
WTG Power
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GE Energy
August 2004
Without
LVRT,
unit will trip
Perception #4
“Wind generation is less stable than conventional
thermal generation”.
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GE Energy
August 2004
Reality
GE Wind farms are more stable that conventional synchronous
generators.
Voltage recovery of the
wind farm is better
Transmission Bus Voltage (pu)
0.9
1.2
1.0
0.8
0.6
0.4
Synchronous Generator
swings dramatically???
0.2
0.0
Total Plant Power (MW)
250
200
150
100
50
0
15
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GE Energy
August 2004
20
Time (seconds)
25
Reality
In fact, GE wind farms will survive some disturbances that trip
conventional synchronous generators.
Transmission Bus Voltage (pu)
0.9
1.2
Power
(MW)
Voltage
(%)
100
1.0
0.8
0
0.6
Wind farm
recovers
0.4
0.2
0.0
Total Plant Power (MW)
200
0
Gas turbine trips
on loss-ofsynchronism
200
100
-2000
-100
Long fault typical of remote locations
-200
0.0
1.0
15
Figure 2
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GE Energy
August 2004
16
Time (seconds)
2.0
17
3.0
18
Conclusions
Transmission owners and operators have legitimate concerns about
potential adverse impacts of wind generation on the grid.
Many of those concerns are well addressed by the latest GE WindVAR
and LVRT technologies.
As wind succeeds, technology must continue to evolve to meet an
expanding spectrum of power system needs. GE Energy is leading this
innovation.
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GE Energy
August 2004