wind farms with power plant capabilities tokyo, october...
TRANSCRIPT
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 1
ENERCONWind Farms with Power Plant Capabilities
Tokyo, October 27th 2009Werner Bohlen / Eckard Quitmann
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 2
Subjects:
1. ENERCON technical concept
2. Operational ranges (U, f)
3. Steady state reactive power capability and how to use it
4. Power frequency control
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 3
ENERCON TechnologyENERCON Gearless drive and variable speed
Advantages:• Direct Drive Concept
No Gearbox• Variable speed operation• Low wear due to slow
machine rotation• Low machine stress due to
high level of speed variability• Yield-optimised control• High hub heights for
increased steady yield• High level of grid
compatibility and compliance with advanced grid codes
• FACTS Capabilities
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 4
ENERCON TechnologyConcept: Gearless drive and variable Speed
GENERATION
Stator
Rotor
Generator: RectifierExcitation
control
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 5
UPS (optional)
Control cabinet
Inverters
Transformer
MV-Switchgear
LV Switchgear
CONVERSION
ENERCON TechnologyConcept: Full scale power electronics
Level 2
Level 0
Level 1
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 6
ENERCON TechnologyStructure electrical system
Filter Trans-former
Circuit Breaker
DC-Link
Ring Generator
==
Excitation Controller
=
Rectifier
≈≈ =
Inverter
≈≈
ControlSystem
Seen from the grid the perfor-
mance is defined by
the inverters
• Seen from the grid the ENERCON WEC is mainly a symmetrical source of current.
• As long as frequency and voltage at the WEC terminals are withinthe specified ranges, the WEC injects the maximum possible current.
• The individual WEC controls the power factor (or reactive power) but not the voltage. The entire wind farm can be equipped with voltage control, if required.
project specifically:ENERCON serial product :
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 7
Operation RangesFrequency and voltage
fR
Frequency f [Hz]
fR + 7 Hz
fR - 7 Hz
100%
Voltage U [% UR]
110% 120%90%80%
Only with UVRT Option:
Max. 5 seconds per event
Only with UVRT Option
Max. 5 seconds per event
Normal continuous operation
max. 60
sec.
145%
Older ENERCON WECs have slightly smaller operation ranges: continously: UR±10%, max. 60s: UR±20%
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 8
P• ENERCON WEC has no need for reactive power.
• Each ENERCON WEC has capability to provide or to absorb reactive power.
• Continously operation, very fast dynamics. PQ range is basis for the ENERCON Voltage Control System (VCS) on wind farm level
• Optional: ENERCON WEC operation as a STATCOM
FACTS Capabilities of Wind Energy Converters Reactive power capability
Qimport
Import from the grid to the WEC
(‘lead’, underexcited, lowering the
voltage)
Export from the WEC to the grid
(‘lag’, overexcited, raising the voltage)
Qexport
≈ 1 p.u.
Import from the grid to the WEC
(‘lead’, underexcited, lowering the
voltage)
Export from the WEC to the grid
(‘lag’, overexcited, raising the voltage)
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 9
400V
Example: required range0.95 exp ... cosφ ... 0.95 imp
PQ range of wind farmTo be undoubtedly defined by the system operator
To be defined:• Reference point for that PQ-range• The minimum PQ-range required (incl. tolerances)• Operational voltage range in which the PQ-range
shall be available• How PQ-range shall be used (steady state operation)
At the 400V terminals
of the WEC
20kV
20kV
20kV
400V
400V
QImportQExport
Active power
Result at PoC
Qoffset due to WF-cabling
PoC?PoC?PoC?PoC (example)
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 10
ENERCON Voltage Control System (VCS)Example: Wind farm in Corsica
UCTE networkExample:
• Aja Wind Farm in Corse
• 6 MW installed capacity: 10 x E-40 600 kW
• Weak electric system, resulting challenges: voltage control, ride through system faults
• Reference point: Point of connection 2,5km far from wind farm
Qwind farm
Pwind farm
UPoint of Reference
VCS onVCS off VCS on
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 11
Voltage profile within wind power plantTo be planned carefully
Voltage profile within the wind power plant must be carefully planned, as injection of P and Q will influence voltage on each WEC, as well as on the PoC.
ZL
Z C
ZL
Z C
ZL
ZLZ C
ZL
Z C
Un
U3
U2
U1
U1 = U2 = … = Un = UPoC
UPoC
Boundary conditions for steady state operation: 400V -10%
+20%
400V -10%+20% UPoC -Y%
+X%
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 12
Future needs of the power system Contribution of WECs during frequency disturbances
For wind energy the requirements about power and frequency must distinguish between:
• Incidents of overfrequency versus underfrequency
• Frequency disturbances during strong wind versus low wind
• Permanent requirements (minutes, hours) versus temporary (sec)
Basic: All modern WECs operate with variable speed, designed for max. active power at any time.
Consequence: If any dependency Power = f(Frequency) isdesired, it has to be implemented “artificially”through the control of the WEC.
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 13
ENERCON Technology Power reduction for overfrequency incidents
1. Overfrequency:
- Relatively easy to respond to
- WEC must reduce active power
- Detailed dynamic parameters to be determined
- Economical consequences negligible
Pelectric = f(frequency)
P(f) curve is adjustablef > fn
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 14
ENERCON Technology Power reserve for underfrequency incidents
wind speed
Prated
• If system tends to become critical, signal can be sent to wind farms: “reduce active power!” (temporarily for precaution)
• If system frequency really falls below flow, wind farm increases active power
• Economical disadvantage for WF only acceptable, if it is limited to a few h/a
• Response time is typical for primary control
Technology is available,but economical aspect
must be adressed!
fhigh fmaxfrated
Pavailible
normalfrequ.range
flow
Plimited
Active power reserve
f
Active power2. Underfrequency:
Prated – x%Preserve as percentage of Pactual
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 15
Thank youThank you
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 16
Why Fault-Ride-Through?Possible consequences of simple grid faults
Spain has a relatively weak
electrical connection to rest of Europe
Today:Pload_min≈ 40 GW
Pwind ≈ 14 GW
Expected:Pwind ≈ 40 GW
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 17
Several 1000 MWwind power is abruptly discon-nected and off for several minutes
Why Fault-Ride-Through?Possible consequences of simple grid faults
Collapse down to 320 kV = 80% UN
Spain has weak electricalconnection to rest of Europe(UCTE power system)
Example: Grid fault in the north of Spain
• Voltage collapses around the failure location funnel-shaped
• According to the old require-ments of the grid operator all WEC in this zone disconnect
• The active power generation of the disconnected generators is suddenly missing after the fault
=> Risk of total blackout(generation ≠ load)
JWPA meeting 27.10.2009© ENERCON GmbH 2009
Slide 18
ENERCON Fault Ride Through CapabilityResumed
Measurement example of an ENERCON E-70 E4 running at 2MW / 3-phase fault
Voltage U [V] Current [kA]
• Ride through for up to 5s per event
• Active power coming from the generator may not be fully fed into the grid dissipated in choppers
• Capability to ride through sym-metrical and asymmetrical faults
• Different FRT-modes for optimumperformance, adressing differentpower system characteristics(physical needs)
• Ability to ride through faults down to zero volts at WEC terminals
Fault Ride Through capability may increase the capacity of a power
system to integrate more wind power