All wind turbines are equipped with a certain power control feature in case the speed of the wind is too high or too low and to have a frequency coherent with the grid. Find out more about Pitch Systems in Wind Turbines: http://bit.ly/dSRis3

1. Pitch Systems in Wind Turbines - Reducing Load and Enhancing Turbine Safety
All wind turbines are equipped with a certain power control feature in case the speed of the
wind is too high or too low and to have a frequency coherent with the grid. The traditional
and the simplest and least expensive method in this respect is a system of natural limitation
known as "stall". The blades are mounted directly on the hub at a fixed angle. When the
wind speed is higher than the operational speed, the blades begin to stall.
This system regulates the power by stalling the blades when a rated power is attained. It is
simple and relatively reliable, but it misses precision because it depends on the air density
and of the roughness of the blades.
The second method modern wind turbines use to control power is the pitch-controlled
system, which is very precise; it can control and adjust the angle of the blades several
times per second if necessary. Blade pitch control is, therefore, the system which, by
regulating the blade pitch angle, turns (pitches) the blades so they can take maximum
advantage of the wind and, at the same time, in case of very high wind speed it functions
as a brake, adjust the angle blade so that the wind goes through. Also, the increased
interest in pitch system is given by the increase of the rotor size.
As mentioned above, these pitch systems continuously control the speed, when it is too
high they lower the blade speed rotation and in case of low wind speed they increase the
rotation speed. Therefore, pitch systems are extremely useful; they “improve the efficiency
of wind energy conversion and power generation stability”1. Pitch systems are usually
equipped with an electrical motor, a gearbox and an electro-mechanic actuator. There are
two types of pitch systems: hydraulic and electromechanical.
Want to read more about the two types of pitch systems?
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1
Tong, W. Wind Power Generation and Wind Turbine Design, Southampton: WIT Press, 2010: 25
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