Concept 1 – fixed speed (Danish Concepts)
In that concepts the configuration denotes the fixed speed controled wind turbine with SCIG (Squirrel Cage Induction Generator) that is directly connected to the grid through a transformer.
Since SCIG always draws reactive power from the grid, this concept uses a capacitor bank for reactive power compensation.
Smoother grid connection occurs by incorporating a soft-starter.
Concepts 2 – variable speed wind turbine with variable rotor resistance
Here in the turbine is used Controlled CRRIG (Rotor Resistance Induction Generator) and pitch control.
The rotor winding of the generator is connected in series with a controlled resistance, whose size defines the range of the variable speed.
Since the losses are proportional to the slip, a limited slip range is used.
As in the Danish wind turbine concepts (consepts 1), the reactive power compensation and a soft starter are required for this concepts.
Concepts 3 – variable speed wind turbine concepts with partial-scale frequency converter (DFIC)
The concepts denotes the variable speed controlled wind turbine with a DFIG (Double Fed Induction Generator) and pitch control.
The stator is directly connected to the grid, while the rotor is connected through a partial-scale frequency converter, typically with a capacity of only 25-30% of a full-scale converter.
Concepts 4 – variable speed concepts with full-scale frequency converter
The concepts corresponds to the full variable speed, pitch controlled wind turbine, with the generator connected to the grid through a full scale frequency converter.
The frequency converter provides the reactive power compensation and a smooth grid connection for the entire speed range.