Siemens Wind Plant Inertial Response
Modeling in PSSE WECC library
Hongtao Ma, Siemens Wind
Robert Nelson, Siemens Wind
Restricted © Siemens AG 2016
Background
•
Wind power penetration increased
•
Frequency stability is a major concern for utility/ISO
•
ISO/Utility required wind plant to provide inertia response (IR)
•
ISO/Utility required inertia response model of wind plant to do interconnection study
•
Some ISO e.g. IESO only accept WECC library model
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Inertial Response of Two Main Scenarios
Scenario 1.
a. Grid frequency drops below threshold to trigger wind plant inertia response
b. Wind plant ramps up to IR predefined boosted power,
c.
Wind plant holds boosted power for the required time, e.g. 10s & grid frequency is not
restored
d. Wind plant ramps down output power and restore the normal operation
Scenario 2.
a. IR is triggered
b. Grid frequency is restored before grid/ISO IR required time is reached
c. IR is stopped and wind plant power restore the normal operation
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Wind Plant Inertial Response Performance
Scenario 1. Frequency
not recovered, IR operated till
the required time
a) Frequency drops below the threshold to trigger inertial
response
b) Wind plant ramps up the power to the required boosted
power level (could be 110% of pre-contingency power -or
pre-contingency power + 10% of park rated power)
c) Wind plant holds the boosted power for the required time
d) IR stopped
e) Wind plant ramps down(ramp rate adjustable) the power
f) Wind plant power recovery
g) During recovery, the active power can not drop to less than a
limit (define of Y% of pre-contingency power by ISO/Utility)
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Wind Plant Inertial Response Performance
Scenario 2 IR stopped after frequency recovered
a) f drops below the threshold to trigger IR
b) Wind plant ramps up the power to the required boosted power
level
c) IR stopped after f recovers above threshold
d) Wind plant active power is droop controlled to ramp down
e) Wind plant power recovery
f) During recovery, the active power can not drop to less than a
predefined limit (defined by ISO/Utility)
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Wind Plant Inertia Response Requirement Main Point
Main point
Dead band
Hydro Quebec
0.1hz
IESO
0.3hz
Brazil
0.2hz
Power threshold for IR
0.25 pu
0.25 pu
0.25 pu
Boosted IR power
6%*(rated power)
IR hold time
9s
10s
5s
IR power rampup time
1.5s
1s
0.5s
Recovery power dip
allowed
less than 20% of precontingency power
no limit
no limit
The second IR available
time after previous IR
recovered
2 minutes
IR available once at
least in 30 min
30 sec
Can IR stop if f restored ?
Yes-f limit not
specified
Yes-59.96hz
Yes-f limit not
specified
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10%*(pre-event P0) 10%*max power
Siemens Inertial Response Control
Assumption for present model:
a.
Wind speed is constant
b.
Wind turbine is not curtailed operation
c.
Pitch control is not triggered
Siemens control strategy:
1. IR is controlled by wind plant not wind turbine directly
2. Adjustable control parameters on slide 6 table
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Siemens Inertial Response Recovery Control
a. Recovery after ramp-down following IR activation
b. Output is ramp down controlled till the original power level
c. Turbine output power set point is from predefined rpm vs.
power look-up table
d. During inertial response the kinetic energy is extracted
from the rotor which reduces the gen rpm, this lead a step
drop in active power.
e. There is an adjustable minimum power limit (default 80%)
during power drop
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Future Work
1.
Wind speed drop or increase during IR
2.
Turbine curtailed operation
3.
Initial operation point difference among turbines in the plant
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