The doubly-fed drivetrain concept uses a wound rotor—an asynchronous generator whose rotor windings are connected to a small converter using slip-rings and brushes. The generator feeds the drivetrain in two ways: two-thirds of the nominal power from the directly connected stator and one-third from the rotor. The converter is used to control the generator’s speed and power factor, allowing a wider speed range for power production and the ability to feed reactive power to support the grid. A small, partial converter (dimensioned to one-third of the nominal power) can be used in this case, because it enables a speed range of approximately +/-30% of the nominal speed, which is sufficient for the wind turbine application.
- Enables variable speed operation for increased kilowatt-hour production
- Uses a small converter, one-third of the nominal power
- Supplies reactive power for grid support
- High total system efficiency
- Is a technical and economical solution for grid code compliance