DC feeder for connection of a wind farm
The objective of the project was to build a demo-plant applying a new d.c. technology and to test in an onshore location with the purpose to investigate technical and financial possibilities for a d.c. connection to offshore wind farms.
At the Tjæreborg windfarm a d.c. feeder of 8 MVA with VSC (Voltage Source Converters) is to be installed, a concept named HVDC Ligh by ABB. The demonstration installation, which is supplied by ABB, has to be used to investigate the possibility of optimising the utilisation of the wind's energy content in a large wind speed area by operating the Voltage Source Converter at variable frequencies. It will be investigated how a d. c. feeder with a VSC most usefully can be applied to transmit power from a large offshore wind farm to a receiving a.c. grid. Furthermore, a feasibility study will be carried out, comparing a.c. feeders for alternative connection possibilities. For a one-year testing period a measuring program will be carried out in co-operation with the Department of Electric Power Engineering from the Technical University of Denmark, in which program the installation's operating performance is investigated, including the wind turbine's power production, reactive power and network losses. Finally, it will also be investigated how the installation influence on the power quality in the wind farm and the connected a.c. grids, respectively
The demo-plant is using a new d.c. cable technology and a new VAC-technology (Voltage Sourced Converter) with IGBT semiconductor valves: Insulated Gate Bipolar Transistors, converting AC to DC and conversely. The demo-plant was placed in Tjæreborg, connecting four wind turbines with a total installed power of 6.5 MW. The transmission capacity of the demo-plant was 7.2 MW and with a d.c. cable length of 4.2 km. Furthermore, a measuring system (collecting data from wind turbines and the d.c. connection) as well as a PCL-system was established. A part from one exception, the project was carried according to schedule and meets all requirements regarding voltage quality, operation and performance. The wind farm VSC station is constructed for operation with varying frequency, enabling an efficient utilisation of wind. Test of the demo-plant with connected wind turbines was carried out with a frequency between 47 and 52 Hz. Experiences with the d.c. connection are good and the regulation ability is stable and suitable for wind turbine connection with asynchronous generators. The major drawback is the losses which are relatively high by comparison with an a.c. connection
Key figures
Category
Participants
| Partner | Subsidy | Auto financing |
|---|---|---|
| Vestkraft I/S | ||
| Danmarks Tekniske Universitet (DTU) |
Contact
Fjordvejen 1 - 11
DK-7000 Fredericia, Denmark
Søbrink, Kent H. ; Projektleder: Kjærgaard, Jens Peter , 76224000, transmission@eltra.dk
Øvr. Partnere: Vestkraft I/S; Danmarks Tekniske Universitet. Institut for Elteknik
