Transcript CIGRE Presentation

ISSUES AND PRACTICAL EXPERIENCES
WITH CONNECTION OF WIND FARMS TO
WEAK AC NETWORKS
June 2013
PRESENTED BY BABAK BADRZADEH
SLIDE 1
BACKGROUND
• At present installed capacity of wind generation in the
Australian national electricity market (NEM) is around
2.7 GW.
• An additional 8-9 GW of wind is anticipated by 2020.
• Fault levels are often lower relative to the Europe and
North America.
• Displacement of synchronous generators by wind and
other forms of variable generation technology causes
network fault levels to reduce.
• Large scale penetration of variable generation—and
consequent displacement of synchronous generators—
may give rise to network-wide issues, as well as local
issues.
SLIDE 2
RELEVANCE
At present only a limited number of wind farms are connected to weak
connection points, but concerns will grow in the future in particular
for:
South Australia:
•
Connected to the NEM power system through ac and dc links, but:
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High wind penetration rate
More wind farms are being connected
Retirement or semi-retirement of some of the large conventional power plants
Network faults levels are becoming lower and lower so as the system inertia
Tasmania:
•
Connected to the NEM power system through dc links only with future concerns
on:
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•
Minimum fault level and inertia
Maximum rate of change of frequency during fault conditions
Sympathetic response of wind farms to remote faults
SLIDE 3
RELATED ISSUES
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Model requirements
Steady-state stability
Transient stability
Minimum inertia
Fault level and protection coordination
Harmonic resonance
Temporary overvoltage
Sub-synchronous interaction (one committed project and
one proposal with series compensated ac lines)
SLIDE 4
NEM EXPEREINCE (1)
• Positive sequence models may be used for conditions
for which their accuracy has not been validated.
• The use of positive sequence models could give rise to
optimistic results compared with the EMT models.
• A carefully designed overall voltage control strategy
coordinating the response of wind turbine and all
reactive support plant is essential.
• Contribution of the wind farm to active power and
frequency control can be crucial in maintaining system
stability, and hence mandatory.
SLIDE 5
NEM EXPEREINCE (2)
• Giving priority to reactive power during fault recovery
could give rise to excessive energy deficit, and
potentially high temporary overvoltages.
• Turbine control may need to be modified to give priority
to active power recovery.
• Understanding the precise behaviour of the fault ridethrough function is essential.
• This many need to be demonstrated through on-site fault
ride-through test.
SLIDE 6
RECOMMENDATIONS
• Identify the criteria and conditions where the use of
electromagnetic transient (EMT) type models may be
required.
• Investigate and identify the minimum short circuit ratio (and
other) requirements for secure and reliable power system
operation with respect to wind generation.
• Study the implications of using type 3 and 4 wind turbines in
weaker parts of the network, in terms of active power
recovery and energy deficit upon fault clearance.
• Investigate scenarios resulting in high temporary overvoltages. Should the results identify high TOVs (in the range
of 1.3 pu), identify whether system-wide controls might be
required.
• Investigate the effects of reactive current injection limits of
around 1 pu in weak and isolated parts of the power system.
SLIDE 7