Powering Europe - European Wind Energy Association

connectingwindpowertothegrid
2.1 Problems with grid code
requirements for wind power
In the past, with vertically-integrated utilities, the
same organisation was responsible for the planning
and operation of networks and giving access to generators,
and therefore the technical requirements did
not have to be particularly clearly defined or equitable.
Now, with legal and increased ownership separation
due to new EU legislation, most prominently
the third liberalisation package between generators
and network owners/operators, the technical requirements
governing the relationship between generators
and system operators must be more clearly defined
11 . The introduction of renewable generation has
often complicated this process significantly, as these
generators have characteristics which are different
from the directly connected synchronous generators
used in large conventional power plants. In some
countries, this problem has introduced significant delays
in the formation of grid code requirements for
wind generation.
A specific problem today is the diversity of national
codes and requirements. Another concern for the industry
is the fact that requirements are not formulated
precisely enough, leaving room for varying interpretations
and lengthy discussions between concerned
parties.
In some countries, a grid code has been produced
specifically for wind power plants. In others, the aim
has been to define the requirements as far as possible
in a way which is independent of the generator
technology. There are benefits in producing requirements
which are as general as possible, and ones
which treat all projects equally. However this can result
in small projects facing the same requirements
as the largest projects, which may not be technically
justified or economically optimal. The European Wind
Energy Association (EWEA) advocates a Europe-wide
harmonisation of requirements, with a code specifically
formulated for wind power.
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Some diversity may be justified because different systems
may have different technical requirements due
to differences in power mix, interconnection to neighbouring
countries and size. However, each country
across the globe uses the same constant voltage and
constant synchronous frequency system – it is only
the physical parameters which are different. Grid code
documents from the different EU countries are not at
all homogeneous. Additionally, documents are often
not available in English making them inaccessible 12 .
These issues create unnecessary extra costs and require
additional efforts from wind turbine designers,
manufacturers, developers and operators.
Requirements for the dimensioning, capabilities and
behaviour of wind power plants are often not clear,
and are not always technically justified or economically
sound from the point of view of the system and the
consumer.
Historically, requirements have usually been written by
the system operator at national level, while the energy
regulatory body or government has an overview.
However, in the interests of fairness and efficiency, the
process for modifying requirements should be transparent,
and should include consultations with generators,
system users, equipment suppliers and other
concerned parties. The process should also leave sufficient
time for implementing modifications. The regulatory
process initiated at European level to develop
the first European network code on grid connection by
ENTSO-E creates an opportunity for the wind power industry
to get thoroughly involved.
The wind turbines that are currently available do not
yet make full use of all possible control capabilities,
for reasons of cost and also because grid codes do
not yet take advantage of the full capabilities they
could provide. As wind penetration increases, and as
network operators gain experience with the new behaviour
of their systems, grid codes may become more
demanding. However, new technical requirements
should be based on an assessment of need, and on
the best way to meet that need.
11 Directive 2009/72 concerning common rules for the internal market in electricity and repealing Directive 2003/54/Ec.
12 There is no one stop shop that provides grid codes from different countries. A fairly complete list of national codes can be obtained
here: http://www.gl-group.com/pdf/IGcc_list.pdf
Powering Europe: wind energy and the electricity grid