Figure 16 Medium voltage power converter, courtesy of Ingeteam.
Function
The power take-off receives electrical energy from the generator and adjusts voltage and frequency for onward transfer to the wind farm distribution system.
What it costs*
The power take-off costs vary significantly for different nacelle layouts.
Who supplies them
Power converters: ABB, AVK SEG, GE Power Conversion, Ingeteam and The Switch.
Transformers: ABB, CG (Pauwels), GE Power Conversion, Schneider Group, SGB and Siemens Power Transmission and Distribution.
Switchgear: CG (Pauwels), GE Grid Solutions, S&C and Siemens Power Transmission and Distribution.
Cabling: Draka (Prysmian), Nexans and Prysmian.
Key facts
Most wind turbines have variable speed generators connected to the grid via AC-DC-AC power converters. There is a range of different generator/converter architectures used. With high power density, today’s insulated-gate bipolar transistor (IGBT)-based power converters frequently are water-cooled.
Critical to consider in the design of power converters are requirements imposed by grid operators for wind turbines to support and stabilise the grid during grid faults and to provide or consume reactive power on demand. Some convertors may be split between nacelle and lower tower section to reduce tower head mass.
Where the turbine voltage rating does not match that of the wind farm array, transformers are often placed in the nacelle [T.1], or sometimes at the base of the tower [T.3]. Typically, they transform from low-kV (0.69kV to 3.3 kV) to 33kV, 66kV or 132kV for distribution around the wind farm array and are of dry (cast resin) design, meeting detailed corrosion, environmental and combustion requirements. Typically, they are forced-air cooled.
Switchgear is designed specifically for wind turbine applications, for example gas-insulated for compactness and safety at up to wind farm distribution voltage.
Down-tower cabling is routed to enable the cables to twist, allowing the nacelle two complete revolutions of movement by the yaw system [T.1.8] before an untwisting operation is required.
What’s in it
- Power converter
- Transformer
- Switchgear
- Cables