Due to significantly higher and more constant wind speeds and the shortage of suitable sites for wind turbines on the land, offshore wind farms are becoming very attractive. The connection of the large offshore wind farms is possible with HVAC, classical HVDC and Voltage Source Converter (VSC based) HVDC technology. In this paper their main features will be given. From the economical and technical viewpoint, the type of connection depends on the size of the wind farm and on the distance to the connection point of the system.
As very promising technology, especially from the technical viewpoint, the focus of this paper will be put on the VSC-based HVDC technology. Its main technical features as well as its model will be detailed. At the end, obtained simulation results for different faults and disturbances for one offshore wind farm connected with VSC-based HVDC technology will be presented.
- Offshore wind farm connection
Fig. 1. Principal scheme of VCS-based HVDC connection
EXPECTED SIMULATION RESULTS:
Fig. 2. Active and reactive power at the connection point during reactive power control
Fig. 3. Active and reactive power at the wind farm side during reactive power control
Fig. 4. Active power, reactive power and voltage at system and wind farm side in case of single phase short circuit near to the connection point – 100ms
Fig. 5. Active power, reactive power and voltage at system and wind farm side in case of single phase short circuit at the wind farm side – 100ms
The connection of an offshore wind farm depends primarily on the amount of power that has to be transmitted and the distance to the connection point.
Primarily due to comparatively small size and short distance to the connection point as well as due to its lower costs and experience, all actual offshore wind farms and those planned to be installed are still using/plan to use HVAC connection.
The advantages of using a HVDC solution are more significant with increase of the distance and power.
The VSC-based HVDC technology is due to its technical advantages like: active and, especially, reactive power control (voltage control), isolated operation, no need for an active commutation voltage etc. very good solution for an offshore wind farm connection. Performed simulation and their results of simulated faults and disturbances show that the technical requirements can be fulfilled.
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 J.G. Slootweg and W.L. Kling, “Is the Answer Blowing in the Wind?”, IEEE Power and Energy Magazine, vol. 1, pp. 26-33, Nov./Dec. 2003.
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