Doubly Fed Induction Generator Systems for Wind Turbines: A Viable Alternative to Adjust Speed over a Wide Range at Minimal Cost

THE AIM OF WIND TURBINE SYSTEMS DEVELOPMENT is to continuously increase output power. A few years ago, the rated output power of production-type units reached 200 kW. By 1999, the average output power of new installations climbed to 600 kW. The largest series production units today are specified to deliver 1.5-MW output power (Table 1). It is anticipated that in the near future, power rating of wind turbines will increase further, especially in offshore applications. For example, the prototype of a Nordex N80 with a rated power of 2.5 MW was installed in March 2000 near Aachen.