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Design and operation of power systems with large amounts of wind power Final report, IEA WIND Task 25, Phase one 2006–2008


There are already several power systems coping with large amounts of wind
power. High penetration of wind power has impacts that have to be managed
through proper plant interconnection, integration, transmission planning, and
system and market operations. This report is a summary of case studies
addressing concerns about the impact of wind power’s variability and
uncertainty on power system reliability and costs. The case studies summarized
in this report are not easy to compare due to different methodology and data
used, as well as different assumptions on the interconnection capacity available.
Integration costs of wind power need to be compared to something, like the
production costs or market value of wind power, or integration cost of other
production forms. There is also benefit when adding wind power to power
systems: it reduces the total operating costs and emissions as wind replaces
fossil fuels.
Several issues that impact on the amount of wind power that can be integrated
have been identified. Large balancing areas and aggregation benefits of large
areas help in reducing the variability and forecast errors of wind power as well
as help in pooling more cost effective balancing resources. System operation and
working electricity markets at less than day-ahead time scales help reduce
forecast errors of wind power. Transmission is the key to aggregation benefits,
electricity markets and larger balancing areas.
From the investigated studies it follows that at wind penetrations of up to
20 % of gross demand (energy), system operating cost increases arising from
wind variability and uncertainty amounted to about 1–4 €/MWh. This is 10 % or
less of the wholesale value of the wind energy.
With current technology, wind power plants can be designed to meet industry
expectations such as riding through voltage dips, supplying reactive power to the
system, controlling terminal voltage, and participating in system operation with
output and ramp rate control. The cost of grid reinforcements due to wind power
is very dependent on where the wind power plants are located relative to load
and grid infrastructure. The grid reinforcement costs from studies in this report
vary from 0 €/kW to 270 €/kW. The costs are not continuous; there can be single
very high cost reinforcements. There can also be differences in how the costs are
allocated to wind power.
Wind generation will also provide some additional load carrying capability to
meet forecasted increases in system demand. This contribution can be up to
40 % of installed capacity if wind power production at times of high load is
high, and down to 5 % in higher penetrations and if local wind characteristics
correlate negatively with the system load profile. Aggregating larger areas
benefits the capacity credit of wind power.
State-of-the-art best practices in wind integration studies include (i) capturing
the smoothed out variability of wind power production time series for the
geographic diversity assumed and utilising wind forecasting best practice for the
uncertainty of wind power production (ii) examining wind variation in combination
with load variations, coupled with actual historic utility load and load forecasts
(iii) capturing system characteristics and response through operational simulations
and modelling (iv) examining actual costs independent of tariff design structure
and (v) comparing the costs and benefits of wind power.




  • Research Council of Norway (RCN) / 193823




  • Hannele Holttinen
  • Peter Meibom
  • Frans van Hulle
  • Bernhard Lange
  • Mark O'Malley
  • Jan Pierik
  • John Olav Giæver Tande
  • Ana Estanquiero
  • Manuel Matos
  • João Ricardo
  • Emilio Gomez
  • Lennart Söder
  • Goran Strbac
  • J. Charles Smith
  • Michael Milligan
  • Erik Ela


  • Unknown
  • SINTEF Energy Research / Energisystemer







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