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Wind Power Plant Frequency Control to Support the
Penetration of High Levels of Renewable Sources
Wind Industry Forum, 17 March 2016
[17 March 2016, Antonio Martinez, Kouroush Nayebi, Manoj Gupta, Yi Zhou, Vestas Wind Systems A/S]
Agenda
Overview of Frequency Control and Regulation
Frequency Control Challenges with High Levels of Renewables
Frequency Control Support from Wind Power Plants
Inertia Emulation Control (FUTURE)
Active Power Control
Frequency Control
Fast Power De-rating
Conclusions and Recommendations
2
Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Overview of Frequency Control and Regulation
Frequency Response
•
)
RE
TU
U
F
l(
Balancing supply and demand
tro
on
f: ion C AS
d
C
d ulat
e
an
yF
dt a Em genc pons
/
f
s
d rti tin
e
e
:
e
lr
n
iz
Hz
bil P In co rtia
50 rol
o
)
Sta WP cond or ine
t
l
t
l
n
e
rol
ro
GC
cy
·
6 s nerat
cy: cont ontro AS
en cy co cont CAS ol (A
n
u
e
r
q
n
F n tr
er cy c FC
·
Ge
qu
we cy
fre ue
fre t pow uen ency
er freq e po gen on Co ds
v
·
e
s
q
o
n
z
v
i
g
P
i
i
i
a
e
c
t
an
bil P f t fr ntin
Re WP P act cont nera mm
o
e
e
Sta WP P fas d co onse
P
t
c
·
W inu tic G tch
p
·
WP secon r res
·
5 m toma dispa
o
0
n
·
r
6 ve
·
Au nual
·
Go
·
Ma
·
·
Frequency
(Hz)
50 Hz
fnadia
z:
0H
o 5 trol
t
n
n
tio co
ula wer
g
Re e po S
v
A
cy
en acti n FC
u
q
P
io
e
P
Fr
W ulat
g
·
Re
·
Frequency
Regulation
Control
Secondary Frequency Control
Inertial Response
Primary Frequency Control
0 Typically
secs 5-10 secs
3
Typically
20-60 secs
Time
(Seconds)
Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Typically
5-10 mins
Frequency Control Challenges with High Levels of Renewables
Displacement of
synchronous
generators
Reduced
system inertia
Power forecasting
for Wind and PV
generation
Supply and
demand
balancing
Rapid changes
in frequency
(larger df/dt)
Synchronous
generator
tripping on df/dt
Larger
frequency
deviations
(larger df)
Increased risk
of UFLS
4
Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Frequency Control Support from Wind Power Plants
Benefits
Inertia Emulation
Control (FUTURE)
Potential Benefits
ROCOF and
Frequency Withstand
Capability Benefits
(typ. 1-4 Hz/sec)
Fast Frequency
Control and Fast
Power De-rating
Benefits
Fault Ride Through
Capability Benefits
Increased system
inertia for raise
services
WPP ROCOF
withstand-reduced
tripping (1-4
Hz/sec)
Raise and lower
contingency FCAS
services (6s, 60s)
No WPP tripping-no
added contribution
to frequency
deviation
Slower changes in
frequency (reduces
df/dt)
WPP frequency
withstand-reduced
tripping (47-53Hz
continuous)
Slower changes in
frequency (reduces
df/dt)
Fast post-fault
active power
recovery-contribute
to stabilising
frequency
Reduced
Synchronous
generator tripping
on df/dt
No added
contribution from
WPP to frequency
deviation
Reduced
Synchronous
generator tripping
on df/dt
reduced risk of
UFLS
Frequency
(Hz)
Smaller frequency
deviations (smaller
df)
Active Power Control
Benefits
Raise and lower
contingency FCAS
services (60s,
5mins)
Raise and lower
Regulation FCAS
)
RE
TU
FU
ol (
r
t
n
Co
df: tion CAS
F
la
nd
t a Emu ency onse
d
/
df rtia ting resp
:
e
l
n
ize
Hz
bil P In co rtia
50
Sta WP cond or ine
to trol ol
C)
l
e
rol
ncy y con ontr AS l (AG
·
6 s nerat
cy: cont ontro AS
e
n
ro
r c FC
qu nc
c
C
ue er
·
Ge
fre eque owe ncy Cont
eq pow ency ncy F
r
r
f
p
e
e
s
r
n
·
st
qu ge
ize
cov P f ive ing tio and
bil P fa t fre ntin
Re WP P act cont nera mm
o
e
e
Sta WP P fas d co onse
·
WP inut tic G tch c
p
·
WP secon r res
a
a
m
·
5 tom disp
·
60 verno
·
Au nual
·
Go
·
Ma
·
·
50 Hz
Smaller frequency
deviations (smaller
df)
Frequency Control
Benefits
fnadia
z:
0H
o 5 ol
n t n tr
tio r co
a
l
gu owe
p
Re
cy ctive CAS
en
F
qu PP a tion
e
r
F
W ula
g
·
Re
Secondary Frequency Control
Inertial Response
reduced risk of
OFGS, UFLS
Primary Frequency Control
Allows time for
governors to
respond
5
Allows time for
governors to
respond
0 Typically
secs 5-10 secs
Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Typically
20-60 secs
Time
(Seconds)
Typically
5-10 mins
·
Frequency
Regulation
Control
Inertia Emulation Control (FUTURE)
Concept Description
•
•
•
•
•
•
Kinetic energy is extracted from all the WTG rotating masses (blades, rotor, gearbox, etc) to produce
active power
Controlled active power production is possible beyond the available power from the wind
Trigger: ROCOF threshold, ferror threshold or both
∆Pinertia: Requested power change in % of Prated for a predefined duration in seconds.
Allows time for the governors to respond to stabilise
frequency
Further research into the benefits of emulated inertia
control from WPP is required
Delta Power
calculator
DPinertia
+
P actual
Trigger
fmeas
6
Frequency
Monitoring
&
Conditioning
ferror
Rate of change
of frequency
(ROCOF)
Estimator
ROCOF
ferror
Inertial
responce trigger
Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Power output
Inertia Emulation Control (FUTURE)
Conceptual Response
Tdelay: Adjustable initial delay.
Trise: The time it takes to reach the needed boost level. The rate of power change is adjustable.
Tsustain: Adjustable maximum boosting time.
7
Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Active Power and Frequency Control
Power Plant Controller® (PPC) Architecture
Power Setpoint
Signal
Active Power loop
Operation Mode
Conditioning
Power limit
Frequency Controller (I)
FRT Mode
FRT Mode
Measured Frequency
Set-Point Frequency
Curtailed Power
Measured/Calculated Power
Dispatcher
Power Control
Frequency
Available Power
Power reference
Controller
Option 1
Power limit
WTGs power
production
Frequency Controller (II)
Power
Controller
Active
Power
Dispatcher
Measured/Calculated Power
FRT Mode
Measured Frequency
Set-Point Frequency
Frequency
Curtailed Power
Measured/Calculated Power
Controller
Option 2
Power limit
Available Power
Fast run-back
Measured Frequency
Inner Control Loop
High Frequency limit
Measured/Calculated Power
Fast Run-back
Trip commands to
Feeder CBs
FRB set by TSO
Power set point for FRB by TSO
8
Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Outer Control Loop
Options or Modes
Active Power
Reference
WTGs
& or
Pause / Stop
Active Power Controller
Primary, Secondary Frequency Control and Frequency Regulation
The active power controller controls the active power output of the wind power plant (WPP).
The active power reference can be provided by different sources.
• Fixed external/internal level
• Frequency Controllers
• Fast Runback Controller
The controller determines active power set-points for the individual turbines in its dispatcher.
The controller includes the following functions:
• Curtailment by a fix value below available
• Curtailment by % of available below available
• Curtailment Ramp rate limiter
• Power Increase Power Ramp rate limiter
• Pausing and releasing WTGs
• Tripping Feeders for fast power reduction
9
Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Onsite Active Power Control Performance
De-rated operation for raise and lower frequency control services
•
Power Reference is set to 92% of possible power
65
61
Power Production [% of Ppossible]
Pref
Pmeas
Ppossible
63
Power [MW]
59
57
55
53
51
49
47
45
0
10
20
30
40
50
60
96
95
94
93
92
91
90
89
88
0
10
20
Time [s]
40
50
60
Power Reference is set to 4 MW below possible power
75
Pref
Pmeas
Ppossible
73
71
Power [MW]
69
67
65
63
61
59
57
55
0
10
20
30
40
50
60
Power reduction [MW below Ppossible]
•
30
Time [s]
6
5
4
3
2
1
0
0
10
20
30
-1
-2
Time [s]
10 Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Time [s]
40
50
60
Frequency Control Option 1
Primary and Secondary Frequency Control
•
•
•
Support to stabilize frequency and to recover frequency to 50 Hz.
Droop control focuses on changing (Raise or Lower) the active power (dP) proportional to the grid
frequency deviation (df).
The frequency deviation (df) is the difference between the grid and reference frequency.
Under Frequency
Support
Over Frequency
Support
11 Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Onsite Frequency Control Option 1 Performance
Simulated Open-loop frequency offset by 0.01 pu
Tested with curtailed WPP at 80 MW in FSM mode
1,012
82
1,01
80
1,008
78
Power [MW]
Frequency [p.u.]
•
•
1,006
1,004
76
74
1,002
72
1
70
0,998
Pref
Pmeas
Fmeas
68
0
10
20
30
40
0
50
10
20
Time [s]
•
•
30
40
50
Time [s]
Simulated open-loop frequency step from 1.0083 pu to 1.003 pu
Tested with curtailed WPP at 80 MW in FSM mode
1,009
80
79
78
Fmeas
1,007
77
Power [MW]
Frequency [p.u.]
1,008
1,006
1,005
1,004
76
75
74
73
Pref
Pmeas
72
1,003
71
1,002
0
5
10
15
20
25
30
35
70
0
5
10
Time [s]
12 Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
15
20
Time [s]
25
30
35
Frequency Control Option 2
Primary and Secondary Frequency Control
•
•
This type of frequency control follows available power in the wind at all times by an offset in MW of in % of
available to allow for raise services.
Controller uses the available power at time of frequency error observation to lower or raise the power
during frequency contingency.
Under
Frequency
Support
Over
Frequency
Support
13 Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Onsite Frequency Control Option 2 Performance
Primary and Secondary Frequency Control
•
•
Simulated Open-loop frequency
Comparing the measured power and the measured control settings
14 Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Fast Power De-rating
Primary Over Frequency Control
•
Fast Runback Controller
Fast Power reduction to a predefined
level by TSO.
Pref
Pref_FRB
Psetpoint_WTG
FRB_Flag
DP
FRB
Reference
Calculation
FRB power command
FRB flag
Measured Active Power
•
P Dispatcher
Psetpoint_PPC
Fast Power reduction by monitoring
frequency
WTG
power
TRIP
Selector
TRIP_Feeder
Feeder
WTG list
Fast Frequency Controller
Measured Active Power
Pow er [% of nominal]
frequency/Power Curve
Measured Frequency
120
100
80
60
40
20
0
Psetpoint_PPC
46
48
50
52
P Dispatcher
Psetpoint_WTG
54
Frequency [Hz]
DP
WTG
power
15 Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
TRIP
Selector
Feeder
WTG list
TRIP_Feeder
Conclusions and Recommendations
Conclusions:
• WPP can provide important contingency and regulation FCAS services to manage the system frequency.
• Today WPPs can provide primary frequency control, secondary frequency control and frequency regulation,
in a similar way (or better) to synchronous generators.
• In the future WPPs may have emulated inertia control capability, however, the benefits are yet to be
understood for various types of grids and operational issues
Recommendations for the future:
• Consider market side solutions to manage the system frequency with high levels of renewables. For
example:
•
•
•
•
•
•
•
Introduce incentives for WPP to enter the FCAS markets
Network upgrades (e.g. new lines or interconnectors)
Review of the system frequency operating standards
Procuring more FCAS during low inertia operation or other high risk operational scenario (high risk of large supply and
demand imbalance)
Improve the power forecasting and the dispatching of WPP
Reduce/eliminate non-scheduled generation
Further research into the benefits of emulated inertia control from WPP is required
16 Wind Power Plant Frequency Control to Support the Penetration of High Levels of Renewable Sources
Thank you for your attention
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