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Fault RideThrough Strategies for VSCConnected Wind Parks
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will be situated far from load ... Power electronic control is required (chopper) Power electronic switches will constitute a high price for this solution ... – PowerPoint PPT presentation
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Title: Fault RideThrough Strategies for VSCConnected Wind Parks
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Fault Ride-Through Strategies for VSC-Connected
Wind Parks
Ralph L. Hendriks, Ronald Völzke, Wil L. Kling
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Contents
- Introduction
- Technical requirements for grid connection
- VSC transmission system outline
- Influence of converter (de-)rating
- Energy dissipation
- Fast power reduction
- Direct communication
- Voltage reduction
- Frequency droop
- Design optimization
- Conclusions
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Introduction
- Future wind parks
- will be situated far from load centres, long
transmission distances - will have high power ratings (hundreds of
megawatt) - Application of HVAC transmission is limited by
charging current of cables - HVDC transmission can overcome these limitations.
Two types - Current-source converter
- Voltage-source converter
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Grid connection of wind power
Technical requirements
- Transmission system operators require well
defined technical behaviour from wind power
plants - During faults in the power system, wind power
plants are usually required to - remain connected during and after the fault
(fault ride through) - support system restoration by supplying reactive
current - Wind turbine generators have been further
developed to comply to these requirements
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Grid connection of wind power
Technical requirements
- Technical capabilities are required at the point
of connection - For VSC-connected wind power plants, the
behaviour during faults is completely determined
by the properties of the VSC transmission system - Different types of wind turbines!
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VSC transmission system overview
- Two-terminal link connecting wind park to active
network - WPVSC functions as a slack node, absorbs all
power - GSVSC controls direct voltage
- Converter type does not impact general
applicability of presented strategies
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Converter (de-)rating
- Power electronic switches have hardly over-load
capability - Current limit must be maintained at all times
- De-rating could improve FRT performance
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Energy dissipation
- Control of the direct voltage during faults using
a dissipative device - Power electronic control is required (chopper)
- Power electronic switches will constitute a high
price for this solution - Thermal aspects need to be considered
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Fast power reduction
Communication
- Wind-park side VSC signals power reduction order
to turbines through a communication link - Only applicable for turbines with controllable
converters - Typical time delay 10100 ms
- Reliability is an issue
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Fast power reduction
Voltage reduction
- Wind-park side VSC sinks the AC voltage to reduce
the incoming power - Inherent reaction from directly coupled induction
generators - The success for wind turbines with power
electronic converters depends on the ratings and
controls of the converters - Standard FRT methods need to be disabled
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Fast power reduction
Frequency droop
- The frequency in the wind park network is
increased to signal power reduction - Inherent response from directly-coupled induction
generators - Additional droop characteristic in turbine
control necessary - Speed of frequency measurement is an issue, PLLs
tend to be slow
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Design optimization
- Converter de-rating and dissipation load to
higher investment costs - Strategies can (parly) be combined to realize
reliable FRT solutions - System can be optimized by formulating boundary
conditions and optimization methods, such as
linear programming
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Conclusions
- The FRT behaviour of VSC-connected wind parks is
greatly determined by the design and control of
the VSC-system - Grid-code compliance with respect to FRT could be
achieved by de-rating, dissipation of excess
energy and fast reduction of incoming wind power - Fast power reduction methods yield lowest
additional costs - Optimized design could combine several FRT
strategies
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