In wind turbine, pitch angle control is essential. Can pitch angle be negative value (Less than zero degree) in wind turbine pitch angle control?
yes, rotation will be changed but for easy calculation, we newer do it. In physically it is possible but there is no mean in mathematical calculation
I struggle to understand why you would want to reverse the pitch? As Navdeep has indicated that would have an effect of reversing the direction of rotation of the alternator/generator, aditionally turbine blades are optimised to rotate in one direction and I would expect the gearbox would be manufactured to rotate in one direction. I think it could be a rather bad idea!
Maybe even
http://www.iaus.com/images/windmill-fire-edited-to-fit-optimised-.jpg
As far as I know, in some wind turbines it is possible to bring the pitch angle of the blades to negative values without suffering any damages. However, the wind turbine must have been designed for such purpose. Therefore, not every wind turbine would perform adequately under these conditions, it depends mainly on the shape and aerodynamic design of the blades. As with positive pitch angle values, a negative angle would affect the wind power capture of the wind turbine, normally decreasing the energy capture, but once more, that would depend on the blade contour.
From Raúl answer I got another question that can this lead to a possibility to run the turbine when the winds are very very high and its unsafe under traditional design?
If wind is high then it is directly operate in cutoff region. and no need to control for it
I was thinking for the scenario when in traditional world it is not possible to run even in cut off because wind is so high that one needs to shut it down. Like in very very high wind condition no amount of pitch angle is able to limit power to the rated power value and hence shuts it.
Yes, it can be. In fact, I was analysing some SCADA data now and the turbine starts operating at a cut-in wind speed of 3m/s with a negative pitch angle (-1.05deg). This pitch angle remains nearly the same until the wind turbine reaches rated power, then the pitch angle increases in order to keep a constant angular wind speed and power.
So yes, you can have negative pitch angle, but it totally depends on the blade profile and your energy capture strategy.
Dear Edgar,
would you share your experimental data. what is the rated power of this wind turbine?
Does anyone have graphs for cp over pitch angle? I can't find anything like that.
When I was undergoing my internship in a wind farm with V90-3.0MW WTGs, I saw that the pitch angle of some wind turbines operating between cut-in and rated region were around -2deg. I was thinking how and why. In academy, when wind turbine operates it is the best option to make the pitch angle at 0deg except for situations above rated wind speed conditions. I thought to myself maybe the angle of attack is around 2 degrees and this angle was set in a negative way from the reference (blade chord line) and thus the reason I saw around -2deg in SCADA was that it was showing the angle of attack. Please someone discuss about this.
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