AES Buffalo Gap Wind Farm
Buffalo Gap 2 - 232.5 MW
155 – GE 1.5 sle
Presented August 22, 2008
By
Robert Sims
AES Wind Generation
AES Buffalo Gap
Wind Farm
Three Phases totaling 524.3 MW
Summary:
Located in Taylor and Nolan Counties SW of
Abilene.
Buffalo Gap 1 – 67 Vestas V-80, 1.8 MW turbines
totaling 120.6 MW, COD late/05
Buffalo Gap 2 – 155 GE 1.5 sle, 1.5 MW turbines
totaling 232.5 MW, COD early/07
Buffalo Gap 3 – 74 Siemens 2.3 MW turbines
totaling 170.2 MW, COD mid/08.
Interconnected to AEP Bluff Creek at 138 kV via
project owned 12 mile 138 kV T/L.
AES Buffalo Gap 2
GE 1.5 sle Wind Turbine
Physical characteristics & Rating
Three blades, rotor diameter of 77 M (253 ft.),
swept area 4657 sq meters (50,128 sg. ft.)
80 meter tubular steel tower (262.5 ft.)
Variable speed operation, main rotor =10-20 rpm
Power regulation via adjustable blade pitch
(electric) & electronic generator torque control
 Main gearbox ratio 1:78 for variable generator
speed of 870 to 1600 rpm with nominal power at
1440 rpm.
Rated 1.5 MW and 575 volts 3 phase
Over 5000 installed worldwide
GE 1.5 MW sle Turbine
GE 1.5 sle Turbine
GE 1.5 MW sle Turbine
GE 1.5 sle Turbine
Method of starting
When the wind in the area increases above the cut in speed (3.5 m/s)
the turbine blades are pitched from “feather” to “power” and the wind
begins to turn and accelerate the rotor. Once the rotor achieves
operational speed of 10-11 rpm the turbine is softly connected to the
line with a ramp up of the power electronics.
Method of controlling power output
Output power is regulated through a combination of variable
blade pitch for control of rotor torque, and variable frequency
control of the generator to control drive train speed and torque.
During a wind gust the rotor frequency is increased and the drive
train is allowed to accelerate while reduging torque to “store” the
gust power spike as kinetic energy in the rotor like a flywheel.
Once the gust passes the controller extracts the power in the
rotor and slows it back to the nominal speed.
Method of stopping
For normal shutdown the rotor blades are pitched to feather. For an
emergency shutdown the blades are pitched to feather (battery backup if required) and a disk brake is engaged on the high speed shaft.
GE
1.5
sle
Turbine
Reactive Devices as Part of the Turbine
The GE 1.5SLE 60Hz wind turbine uses a power converter system that
consists of an electronic converter connected to the generator rotor, a
DC intermediate circuit, and a power inverter on the grid side. This
system functions as a pulse-width-modulated variable frequency
converter in 4-quadrant operation.
The converter its self consists of an insulated gate bipolar transistor
(IGBT) power module and the associated electrical equipment. Variable
output frequency of the converter allows a rotational speed-module
operation of the generator within the range of 870 rpm to 1600 rpm.
The Standard GE 1.5SLE 60Hz Wind Turbine is designed with a
selectable power factor. At 1.0 pu voltage (575 V) and full power (1500
kW), a power factor of 0.95 overexcited (reactive power delivered by
the wind turbine) to 0.90 underexcited (reactive power absorbed by the
wind turbine) as measured at the terminals of the trubine. The power
factor is settable at each WTG or controlled remotely and dynamically
by the wind farm SCADA system (more on this later).
Optional Reactive Capability: 0.90 overexcited / 0.90 underexcited at 1.0 pu voltage (575 V) and full power (1500 kW) is
available at an additional cost.
GE 1.5 sle Turbine
Grid Frequency Tolerance
Continuous operation in the frequency range of 57.5-61.5 Hz.
Trips as the frequency drops below 56.5 Hz or exceeds 62.5 Hz.
GE 1.5 sle Turbine
Voltage Tolerance (At the 575 volt terminals of the turbine!)
Voltage limits for the GE 1.5 MW, 60 Hz wind turbine are as follows:
AES Buffalo Gap 2
 Site Selection Criteria
The Buffalo Gap project location was selected based on it’s high
elevation resulting in high average wind speeds, rural location
with compatible land use, and proximity to transmission lines.
 Cabling Connections to collector substation & Electrical
characteristics
The GE turbines have a Padmounted type transformer located at the
base of each turbine to raise the voltage from the 575 volt turbine
terminal voltage to 34.5 kV for the site power collection system. A
combination of underground and overhead power lines based on
standard utility practices carry the power to the central step up
substation. Typically 20-30 MW of generation is connected to
each substation 34.5 kV breaker positions.
 Operational Issues
The only operational issues of moderate significance has been
disturbances resulting from lightning strikes to overhead portions
of the system.
AES BG 2 Control System
 Location of Control Rooms / Facilities
The project has both local supervision & control, along with remote
supervision & control 24/7 from the AES Wind Generation central
control facility in Palm Springs, California.
 SCADA
The project has separate turbine SCADA systems for the 3 types of
turbines associated with the 3 phases of the project (Vestas, GE,
& Siemens) along with a separate SCADA system for the
interconnection substations.
 Turbine Power Control
Turbine power is generally controlled locally by each turbine
individually to maximize energy capture. However, the local
control can be overridden for the fleet by the turbine SCADA
control and capped at lower max power levels.
AES BG 2 Control System
 Reactive Control
Individual turbine reactive power is controlled centrally from the GE
SCADA system. Voltage and power factor are monitored at the
main collector substation. The system can operate on a voltage
set point, or a power factor set point, and remotely adjusts the
power electronic converters in each of the turbines along with
automatically switching the 34.5 kV substation capacitor banks.
 Switch / Breaker Control
Substation control can be local from the substation using
either traditional control devices on the switchboard or a
SCADA terminal in the substation control house, or
remote supervision and control via the substation
SCADA.
 Special Protection Schemes (SPS)
The Buffalo Gap 3 project is being fitted with a short term
SPS to reduce generation in the event of the loss of one
of the 345 kV lines to Bluff Creek during maximum wind
power generation. This SPS will be required for a few
years until area transmission improvements are
Thank
You
robert.sims@aes.com