wind farms with power plant capabilities tokyo, october...

JWPA meeting 27.10.2009© ENERCON GmbH 2009

Slide 1

ENERCONWind Farms with Power Plant Capabilities

Tokyo, October 27th 2009Werner Bohlen / Eckard Quitmann


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


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


Slide 4

ENERCON TechnologyConcept: Gearless drive and variable Speed

GENERATION

Stator

Rotor

Generator: RectifierExcitation

control


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


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 :


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%


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)


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)


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


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%


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.


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


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


Slide 15

Thank youThank you


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


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)


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

wind farms with power plant capabilities tokyo, october...

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