ENERCON wind farms integration into power systems - Future ... · PDF fileBrussels, September 24th 2010 ENERCON wind farms integration into power systems - Future of ancillary system

Brussels, September 24th 2010

ENERCON wind farms integration into power systems -Future of ancillary system services Eckard Quitmann, ENERCON GmbH, Department Sales-Technical Support

2Sales - Technical Support, March 12th 2010© ENERCON GmbH 2010

• WFs that shall be legally and commercially independent entities, need individual “Points of Connection” (PoC)even if they share infrastructure, e.g. substation

• Electrical criteria apply to all at PoC

Point of Connection (PoC)Reference point for wind farm controls

PoC WF AMV

MV

MV

400V

400V

400V

WF A

no PoC !MV

MV

MV

400V

400V

400V

WF B

PoC WF B


Point of Connection (PoC)Reference point for wind farm controls

PoC WF AMV

MV

MV

400V

400V

400V

WF A

MV

MV

MV

400V

400V

400V

WF B

PoC WF B

, no matterif WECs are located Onshore or Offshore

• WFs that shall be legally and commercially independent entities, need individual “Points of Connection” (PoC)even if they share infrastructure, e.g. substation

• Electrical criteria apply to all at PoC


ENERCON TechnologyConcept: Gearless drive and variable speed

GENERATION

ControlsStator

Rotor

Generator: Rectifier

Excitation

Yaw DrivesPitch Drives


UPS (optional)

Control cabinet

Inverters

Transformer

MV-Switchgear

LV-Switchgear

CONVERSION

ENERCON TechnologyConcept: Full scale power electronics

Level 2

Level 0

Level 1


ENERCON TechnologyStructure electrical system

Circuit Breaker

=≈

InverterDC-Link

=≈

Rectifier UnitTransformer

Constant grid frequency

Variable speed

==

Excitation Controller

RG

Ring Generator

=≈

UPS Chopper

ControlSystem

Filter


ENERCON TechnologyStructure electrical system

Circuit Breaker

=≈

InverterDC-Link

=≈

Rectifier UnitTransformer

==

Excitation Controller

Ring Generator

=≈

UPS Chopper

ControlSystem

Filter

RG

• Grid performance of the ENERCON WEC is determined by the inverters!• The inverter is essentially a controlled source of current.• The individual WEC controls the power factor (or reactive power) but not the voltage. • Voltage control on Wind Farm level on request (in Belgium mandatory if PWF>25MW)


With UVRT Option:Up to 5 seconds per event

With Undervoltage Ride Through Option: Up to 5 seconds per event

max. 60

sec.

fR

Operation RangesFrequency and voltage

Frequency f [Hz]

fR + 7 Hz

fR - 7 Hz

100%

Voltage U [% UR]

110% 120%90%80%

Normal continuous operation

145%0%


P

t

Flexible active power Limitation

ENERCON Technology Active Power Control

The full scale power electronics allow a fast and flexible continuous control of the active power at each individual ENERCON WEC.

• Performance achieved by piching the WEC blades.• Activated based on an online signal from the system operator.• Little additional investment in WF necessary (for online communication).• Yield relevant => Usually only for emergencies


Future needs of the power system Contribution of WECs during frequency disturbances

For wind energy, requirements about power and frequency shall distinguish between:

• Incidents of overfrequency versus underfrequency

• Permanent requirements (minutes, hours) versus temporary (sec)

• Frequency disturbances during strong wind versus low wind

Basic: All modern WECs operate with variable speed, designed for max. active power generation at any time at all wind speeds.

Consequence: If any dependency Power = f(Frequency) is desired, it has to be implemented “artificially”through the control of the WEC.


ENERCON Technology Power reduction for overfrequency incidents

1. Overfrequency:

- Relatively easy to respond to, WEC must reduce active power

f > fn

• Performance achieved by piching WEC blades.• Activated based on local frequency measurement.• No additional investment in WF necessary.• Yield relevant => Usually only for emergencies with f > 50,x Hz

Pelectric = f(frequency)

P(f) curve is adjustable


ENERCON Technology Inertia Emulation for underfrequency incidents

Optional active power boost, using the inertia of the rotor.

Pboost = 10%Prated

Available as soon as Pactual ≥ 4%Prated

Pboost fully available within 800ms

Boost for max. 10 seconds

Recovery time after boost = 2 x Tboost

2. Underfrequency: Pactual Pref

200

250

300

350

400

450

500

550

600

650

700

750

800

850

900

950kW

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0

s

• Performance achieved by changing excitation, using rotor inertia.• Activated based on local frequency measurement.• Additional investment in WF necessary.• Cost relevant => Economical value for the power system?• Impact to the max. installable wind power?


Q export

Prated

Q import

Q/Prated: 50% 33% 0 33% 50%

International requirements PQ-Range for wind power plants

UK Spain

No minimum range defined, but

economical bonus if 0,95exp < cosϕ > 0,95imp

is possible

Germany France ERDF RTE

400V

400V

400V

400V

400V

400V

400V

400V

400V

400V400V

400V400V

400V

Q export

Prated

Q import

Q/Prated: 50% 33% 0 33% 50%

Q export

Prated

Q import

Q/Prated: 50% 33% 0 33% 50%

shape slightly depending on

PoC voltage level

Conclusions

- PQU range must be well defined by TSO/DSO

- A Q-requirements is different from a cosϕ

- Area near P=0 must be adressed

- Separately to define how PQ- range shall be used during steady state operation

Q export

Prated

Q import

Q/Prated: 50% 33% 0 33% 50%

?


Belgian requirement “RTF”PQ-Range

Typical PQ-range of a thermal power plant

Pminimum due to thermal process

+0,45 … - 0,1Prated

Conventional power plants:

- have a technical minimum of activepower generation, usually 20…50%Prated

- below that they are not obliged to be ableto deliver or absorb reactive power in therange +0,45 … - 0,1PratedEspecially not at P≈0!

Q export Q import

_PratedP


Belgian requirement “RTF”PQ-Range for wind power plants

Q export Q import

Prated

+0,45 … - 0,1Prated

Wind power plants:

-Technical minimum is P≈0

- Obligation to range Q=+0,45 … - 0,1Pratedfrom P=0…Prated would mean:

a) STATCOM (100t€/Mvar !) or

b) Fix C and L devices. Their on/off switching is negativefor the grid voltage stability.

400V

400V

400V

Reasonable PQ-requirement for power plants

Pminimum and exact shapeto be defined


Q

PThe ENERCON WEC itself has no need for reactive power, can operate at unity power factor.

Depending on type and configuration, each WEC has a capability to provide or to absorb reactive power.

Full reactive power capability between20% and 100% Prated

STATCOM Option: Full reactive power output between 0% to 100% active power => Reactive power output is independent from windspeed

Supports the system stability like a STATCOM without an additional FACTS device => potential cost savings

Reactive power resp. voltage control may be paid in some markets as an ancillary service

FACTS Capabilities of Wind Energy Converters ENERCON PQ range and STATCOM Option

1 p.u.+/- 0,5 p.u.


Future Belgian requirement “RTF”PQ-Range for wind power plants

Q export Q import

Prated

+0,45 … - 0,1Prated

Reasonable PQ-requirement for power plants

Pminimum and exact shapeto be defined

• Present ELIA transmission grid requirements cause high additional investment in WF• Minimum reactive power requirements are already in discussion at ELIA• Capbank/Reactor, SVCs and STATCOM have different technical value for the power system• Reasonable requirements for low wind speed conditions?• Q-Capabilities beyond the minimum should be remunerated additionally (range and quality) !

Example, not final !


Present Fault-Ride-Through requirements in Belgium

• Present Belgium transmission + distribution grid requirements for FRT are very moderate• Distrib. grid: Even „only“ 200ms voltage dip down to 0,7pu requires full FRT capability of a WEC• Transmission grid: FRT capability is mandatory. But what performance is best during the fault ?

Measurement example of an ENERCON E-70 E4 running at 2MW / 3-phase fault

Active Power P [MW] Reactive Power Q [Mvar]


Example from actual grid code requirementsGermany

Requirement: The wind farm has to provide a reactive current during faults to support the system voltage.

The amount is dynamically depending on the actual voltage level!

Gradient dQ/dUadjustable

Extract from

Verordnung zu Systemdienstleistungen durch Windenergieanlagen

(Systemdienstleistungsverordnung – SDLWindV) of 27.05.2009


ENERCON UVRT Reactive current according to voltage dip (QUM)

Voltage dip down to 72% Urated

Half of max. reactive current: 50% Irated

Voltage [V] Reactive current [kA]

Voltage dip down to 50% Urated

Maximum reactive current: Irated

Voltage [V] Reactive current [kA]


relatively “lo

w” technical require

ments

Technical suggestions how to define techncial minimum requirements for to optimize grid integration

Voltage level at point of connectionUnominal < 70kV 70kV ≤ Unominal < 220kV Unominal ≥ 220kV

Scc/PWF > X= strong point of

connection

Scc/PWF < X= weak point of

connection

Criteria FRT:

Criteria PQ:

Criteria FRT:

Criteria PQ:

relatively high te

chnical require

ments

Reasonable technical re

quirements also in

“middle” fie

lds

to be defined by th

e system operator


Technical suggestions how to define techncial minimum requirements for to optimize grid integration

Conclusions:

1. The power system shall have the maximum technical benefit from new wind farms, no matter if located onshore or offshore

2. General technical criteria and what is the minimum requirement must be defined

3. Investment into to wind power plants depends on the technical minimum requirement

4. Reasonable technical minimum requirements may depend on the point of connectionand need to be determined by the system operator

5. Exceeding technical minimum requirements should have economical benefit for the wind farm owner – as it also has for the power system

relatively “

low” technical require

ments

Voltage level at point of connectionUnominal < 69kV 69kV ≤ Unominal ≤ 138kV Unominal > 138kV


connection


connection

Criteria FRT:

Criteria PQ:

Criteria FRT:

Criteria PQ:

relatively high te

chnical require

ments


quirements in

“middle” fields

to be defined by th

e system operator

relatively “


ments

relatively “


ments

Voltage level at point of connectionUnominal < 69kV 69kV ≤ Unominal ≤ 138kV Unominal > 138kV


connection


connection

Criteria FRT:

Criteria PQ:

Criteria FRT:

Criteria PQ:

relatively high te

chnical require

ments


quirements in

“middle” fields

to be defined by th

e system operator


Thank you !

Questions?

Documents

ENERCON wind farms integration into power systems - Future ... · PDF fileBrussels, September 24th 2010 ENERCON wind farms integration into power systems - Future of ancillary system