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El apoyo de parques eólicos a sistemaseléctricos débiles – servicios auxiliares

Wind farms support to weak electrical systems – auxiliary services

E. QuitmannENERCON GmbH

Power Expo Zaragoza September 2008 Eckard Quitmann, Sales - Technical Support, © ENERCON GmbH 2008

Slide 2

Technical criteria for integration of wind power into power systems

Technical criteria for large scale integration of wind powerin the European mainland grid (UCTE)

Electrical issues are in general similar, just the timing when being relevant is different

in small electrical systems (Islands)

What is relevant:• Dispatching P• Dispatching Q• Voltage control• Fault-Ride-Through• Power-frequency control• …


Slide 3

Wind Energy Converters and their integration into power systems

Brief Introduction to ENERCON and itstechnology for wind energy converters

Electrical criteria for power system integration - Dispatching P and Q- Voltage control- Fault-Ride-Through- Power-frequency control

Conclusions


Slide 4

ENERCON TechnologyVariable speed - gearless drive - full scale power electronics

The gearless ENERCON concept is technically and economically far superior to all conventional turbine concepts.

Characteristics:► Gearless direct drive► Slow machine rotation► Variable speed► Yield-optimised blade design

and WEC control► Full scale power electronics

for power plant capabilities► FACTS Capabilities meet the

most advanced grid codes and connection requirements

* FACTS = Flexible AC Transmission Systems


Slide 5

Introduction to ENERCONENERCON Product Line

PR = 2.300kW

E-70

PR = 330kW

E-33

PR = 800kW(900kW

for E-44)

E-44/E-48/E-53

PR = 2.000kW

E-82

PR = 100kW

E-20


Slide 6

Introduction to ENERCONENERCON Product Line: E-126 6MW

E-126PR = 6.000 kW

13 machines installed(10 as E-112)

135 m hub heightIEC Class I a

Most powerful wind turbine worldwide


Slide 7

ENERCON TechnologyCharacteristic of the WEC for the power system

Filter Trans-former

Circuit Breaker Seen from the

grid the performance

is defined by the inverters

DC-Link

Ring Generator

==

Excitation Controller

=

Rectifier

≈≈ =

Inverter

≈≈

ControlSystem

Power flow

• Seen from the grid the ENERCON WEC is mainly a source of current.

• As long as frequency and voltage at the WEC terminals are within the 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.


Slide 8




Conclusions

practiced in Spain


Slide 9

Wind farms with Voltage Control System (VCS) and the benefits for the integration of wind power into power systems

Qwind farm

Pwind farm

UPoC

ENERCON Grid Data

Acquisition

ENERCON SCADA PC

Point of Connection (PoC)

Automatic, dynamic Voltage Control System:

- Can improve quality of power supply

- Impact on voltage depends on a) Q-range from WFb) stiffness of PoCc) dynamics

- Needs to be studied project specifically


Slide 10

Example from actual grid code requirementsSpain: P.O. 12.3.

Typical voltage-time-limiting curve

Minimum reactive current requirement while voltage is depressed during a fault.Reference: “Total current”Consequence: minimum tanϕ for current injection during a fault.

ENERCON WEC with UVRT Option:- Passes voltage dips, even with U=0- For up to 5 seconds- Fault Ride Through capability is adjustable

to optimize benefit for the power system- Can provide reactive current up to I rated


Slide 11

Future aspects of Fault-Ride-ThroughTo be discussed with system operators

Effects of voltage dips to be addressed more in detail when going to really high wind power penetration or weak power systems:

- Transients during beginning and clearance of fault- Transformer inrush (reference point for P- and Q-limit

is usually the HV side)- Reasonable contribution of reactive current:

+ during unbalanced faults+ in radial distributed systems (risk of islanding)+ considering PoC specific dynamics of the

power system (voltage recovery)

Future: PoC specific contribution of reactive current during faults


Slide 12

ENERCON technology capability to ride through frequency disturbances

- Example: Measurement in Corsica

- High frequency gradients observed

- Could occur similar on Canarias

- Remember November 4th 2006 !

ENERCON WECs pass frequency disturbances up to 4 Hz/second

Reasonable future requirement: WECs to stay connected during frequency disturbances

Generation unit trips

Wind power plant active power

Wind power plantvoltage

Wind power plant current

Frequency


Slide 13

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- Incidents during strong wind versus slow wind- Permanent requirements (minutes, hours) versus temporary (sec)

The power system operator shall define: - requirements independent of the WEC technology- economical value for power-frequency system services

WEC manufacturers then shall develop the optimum technical- and economical solution that meets the requirements

Basic: All modern WECs operate with variable speed.

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


Slide 14

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

Pelectric = f(frequency)


Slide 15

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 f low, wind farm increases active power

• Economical disadvantage for WF acceptable, if it is limited to a few hours per year

Technology is available,but exact dynamic requirements

need to be specified !

fhigh fmaxfrated

Pavailible

normalfrequ.range

flow

Plimited

Active power reserve

frequency

Active power2. Underfrequency:

Prated – x%Preserve as percentage of Pactual


Slide 16




Conclusions


Slide 17

Conclusions ENERCON Technology and power system integration

ENERCON WECs:

► Generating unit and FACTS device merged in one single device

► Wide range of available options and parameters to optimize wind farm benefit for power system

General:

► Future issues to be discussed between wind farm promoters, manufacturers and power system operators:

• Reactive power provision & voltage control

• Refined Fault-Ride-through requirements

• WEC to withstand high frequency gradients

• WEC contributions to power-frequency control


Slide 18

Thank you for your kind attention!

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