Brian Parsons

National Wind Technology Center

National Renewable Energy Laboratory

Golden, Colorado USA

European Wind Energy Conference 

Athens, Greece

February 27 – March 2, 2006

COMPARING SINGLE AND MULTIP

REPRESENTATIONS IN A WIN

SIMULATION

NREL/PR-500-39507
Disclaimer and Government License

This work has been authored by Midwest Research Institute (MRI) under Contract No. DE-AC36Department of Energy (the “DOE”). The United States Government (the “Government”) retains athe work for publication, acknowledges that the Government retains a non-exclusive, paid-up, irrepublish or reproduce the published form of this work, or allow others to do so, for Government puNeither MRI, the DOE, the Government, nor any other agency thereof, nor any of their employeeor implied, or assumes any liability or responsibility for the accuracy, completeness, or usefulnesproduct, or process disclosed, or represents that its use would not infringe any privately owned ri

specific commercial product, process, or service by trade name, trademark, manufacturer, or othimply its endorsement, recommendation, or favoring by the Government or any agency thereof. authors and/or presenters expressed herein do not necessarily state or reflect those of MRI, the agency thereof. 
• Investigate different characteristics of 

wind turbines operating under normal and transient events. 

• Understand the signature of each 

unique characteristic of the turbines.

• Represent the wind farm as a 

collection of unique groups of wind turbines.

OBJECTIVES APPR

• Simulate a singl

attributes (line represented. 

• Compare the sig

attribute of each differences in d

• Represent a mu

power system nturbines with un
Wind Farm P&Q

Time (sec)

10 11 12 13 14 15 16 17 18 19 20

P (MW) at PCC

0

102030405060 Real Power

WF1G

Wind Fa

10 11 12 

P at PCC

0

102030405060 Real Powe

single turbine m

Power 

Voltage

DYNAMIC – NORMAL OPERATION

Tower Shadow Effect

Vph at Infinite Bus and at PCC (in p.u.)

Time (sec)

0 100 200 300 400 500 600

Per phase voltage (in p.u.)

.90.95

1.001.051.10 Per phase voltage at PCC

WF1G

Vph at 

0 100 

Per phase voltage (in p.u.)

.90.95

1.001.051.10 Per ph
DYNAMIC – FAULT TRANSIENT

Various Wind Speeds

Rotor speed (p.u.)

Pitch angles (deg).

Reactive Power (p.u.)

Power

Wind speed

8.5 m/s

13 m/s 16.3m/s
DYNAMIC – FAULT TRANSIENT

Weak Grid vs Stiff Grid

Rotor speed.

Pitc

Real Power 

Reactive Power

Bus voltage
Single line diagram of a wind farm with 

5 groups of turbines (20 MW/group).

DYNAMIC – FAULT TRANSIENT

Multiple Turbine Represen

Voltage at the 
CONCLUSIONS

• Diversities characterizing wind turbines such as line imdifferences, turbine types, relay protection settings, creactive power compensation etc. may affect the LVRT o• Wind turbines are electrically connected but mechanicrespect to each other. Mechanical-electrical interaction is in a large wind farm than in a single large conventional sy• In the event of a fault:

- single turbine representation leads to the worst-cfault event may disconnect the entire wind farm). - multiple groups of wind turbines better represent a 

a best-case scenario (a single fault event may dturbines within the wind farm).