Powering Europe - European Wind Energy Association

alancingdemand,conventionalgenerationandwindpower
Wind power’s impacts on power system balancing
can be seen over several time scales, from minutes
to hours, up to the day-ahead time scale. It can be
seen both from experience and from tests carried out
that the variability of wind power from one to six hours
poses the most significant requirements to system
balancing, because of the magnitude of the variability
and limitations in forecast systems. At present, frequency
control (time scale of seconds) and inertial response
are not crucial problems when integrating wind
power into large interconnected power systems. They
can however be a challenge for small systems and
will become more of a challenge for systems with high
penetration in the future.
2.2 Effect of wind power on
scheduling of reserves
The amount of additional reserve capacity and the corresponding
costs when increasing the penetration of
wind power are being explored by power engineers in
many countries. The investigations simulate system
fiGURE 1: tiMEsCalEs foR Utility oPERations [PaRsons, 2003]
68
System Load
0 6 12 18
Time [Hour of the Day]
Cycles
Transient stability
& short-circuit
1 http://www.ieawind.org/AnnexXXV.html
Seconds to minutes
Regulation
Minutes to hours
Load Following
operation and analyse the effect of an increasing
amount of wind power for different types of generation
mix. The increase in short term reserve requirement
is mostly estimated by statistical methods that combine
the variability or forecast errors of wind power to
that of load and investigates the increase in the largest
variations seen by the system. General conclusions on
increasing the balancing requirement will depend on
factors such as the region size, initial load variations
and how concentrated/distributed wind power is sited.
In 2006 an agreement on international cooperation
was set up under the IEA Task 25 1 to compare and analyse
the outcome of different national power system
studies. The 2009 report of this Task 25 [Holttinen,
2009] gives generalised conclusions based on studies
from Denmark, Finland, Norway, Sweden, Germany,
Ireland, Spain, Netherlands, Portugal, the UK and the
USA. This experience is used in this report to illustrate
the issues and solutions surrounding the reserves
question. The value of the combined assessment in
the IEA Task 25 is that it allows the systematic relationship
of the increased demand of system reserves
to be shown as a function of wind energy penetration.
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Days
0 6 12 18 24
Time [Hour of the day]
Daily scheduling/unit commitment
Most results are here
Powering Europe: wind energy and the electricity grid