ABSTRACT
A number of different wind power systems are described in this chapter. Wind turbine design objectives are optimized-driven within the operating regime and market environment. In addition to wind turbines becoming larger, wind turbine design concepts have changed from fixed speed, stall-controlled and drive trains with gearboxes to variable speed, pitch-controlled with or without gearboxes. Wind turbines can be classified according to their speed control and power control ability. The speed control criterion divides the wind turbines into two significant classes as fixed speed wind turbines; variable speed wind turbines while the power control divides the wind turbine concepts in three classes as stall control; pitch control; active stall control. The frequency of large power systems is usually very stable, and therefore the individual or small clusters of wind turbines do not typically influence the frequency.
