Transcript Renewable Wind Turbine Fault Ride

2008 能源與科技論壇暨研討會
Wind Turbine Generators Fault Ride-Through Capability
- A Comparison Study of SCIG and DFIG
Lin, Yu-Jen
Department of Electrical Engineering, I-Shout University, Kaohsiung County, Taiwan, ROC
Doubly Fed IG
Squirrel Cage IG
Motivation
SCIG (Squirrel Cage Induction
Generator) and DFIG (Doubly
Fed Induction Generator) are
two commonly employed
generators in wind turbine
power systems. This
poster investigates these wind
turbine generators’ fault ridethrough capability.
The stator of an SCIG directly connects
to the grid, while the rotor circuit is
short-circuited. Therefore, the only
control measure is pitch angle control
whose original objective is to limit wind
power and then prevent from turbine
damage.
SCIG
Turbine
Case Study
ωr
Wind
Ps Qs
Tr
Stator
Rotor
Figure below shows a
P
Stator
Power system consisting of a
Three-Phase Grid
wind farm including
Pitch Angle Control
Control
Three 575V, 3 MW
wind turbines. Each wind
turbine is equipped with a capacitor
set providing 600 kVar reactive power. The wind farm delivers
8.7 MW electricity to 120 kV grid through a 25 km, 25 kV
distribution feeder. Consider a double-line grounded fault which
may cause from, say, stormy lightening, occurred at the spot
marked in the figure.
m
Results
In a DFIG, the stator directly
connects to the grid but the rotor is
fed from a back-to-back AC/DC/AC
converter set via slip rings and
brushes. The rotor side converter,
RSC, controls the wind turbine
output power and the voltage
measured at the grid side. The grid
side converter, GSC, regulates the
DC bus voltage and interchange
reactive power with the grid. It also
has pitch angle control. All in all,
DFIG owns more degrees of
freedom in control than SCIG.
Below illustrates a DFIG’s schematic
diagram.
DFIG
Turbine
ωr
Wind
Tr
Case
Study
WT 1
575V
3 MW
1 km
25kV/575V
600 kvar
T1
575V
Wind
Turbine
Using
SCIG
WT 2
1 km
120kV / 25kV
25kV/575V
600 kvar
575V
WT 3
1 km
3 MW
25kV/575V
600 kvar
GSC Pgc
Qgc
Grid Side
Converter
Vgc
Stator
3 MW
25 km
DC
Rotor Side
Converter
Vr
Pm
Pitch Angle Control
25kV
RSC
Stator
Rotor
Through comprehensive computer simulations, it has been
shown that, using SCIG, all three wind turbines WT1, 2 and 3, are
tripped due to under-voltage protection. However, if we are using
DFIG, the system can ride through the fault without tripping any
wind turbine , as indicated in the figure.
120kV
Ps Qs
Pr
Qr
Wind
Turbine
Using
DFIG
Three-Phase Grid
Control