energy into the grid, a rectifier and an inverter stage were needed. The inverter has to
be designed for the full system capacity
The 1990s had seen wind turbines with doubly fed induction machines introduced on a
The rotor-side inverter, which only has to be designed for 25% to 30% of
the nominal plant output, made an adaptation of different rotor speeds to the grid
frequency possible. In these and earlier systems, additional motors where used to
adjust the pitch, i.e. the angleof the rotor blades to thewind
Examples of wind turbine
Particularly the occurring load cycles are of great importance for the IGBTs used inwind
turbines. This is illustrated by the example of a wind turbine with a doubly fed induction
A doubly fed inductionmachine consists of a slip-ring inductionmachinewith a rotor-side inverter. This is used
to control the speed and the reactivepower of themachine.
Recent developments are shifting the power of wind turbines to even higher levels. Using increased DC-link
voltages suitable for 3.3kV and4.5kV IGBTmodules in three-level topology.