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Wind Sector Management (WSM) Strategy Creation

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Figure 149:   Create WSM Strategy

 

If one or more turbines has one or more wind speeds for which it has an effective TI value above the IEC curve for its class of turbine, it may be necessary to institute a wind sector management strategy which means curtailing turbine operations for some turbines for a range of wind speeds and directions.

Such a strategy can be derived by hand by looking at the closest turbines with reference to the detailed effective TI report which gives effective TI by wind speed and direction. This is widely practiced but can be very time-consuming depending on the turbine layout. Another strategy which is far less time-consuming and can give reasonable results is to curtail turbines when an operating upwind turbine is less than a certain number of rotor diameters away (this is the automatic sector management option show in Directional Curtailment ). However, this method does not guarantee that the effective TI will be compliant and may lead to turbines being unnecessarily curtailed. For this reason, Openwind offers a third option which involves using a simple heuristic algorithm that draws rectangles around areas of the effective TI report which are significantly above the IEC curve and creates curtailments based on the extents of these rectangles in both wind speed and direction. This method has two flaws: at one extreme it will create a few very general curtailments which result in too much energy being lost; at the other extreme it will create a great many curtailment rules which tend to look silly to a human but may result in less energy being lost, at least as modelled in Openwind. This being a relatively new method, in practice we do not know what the best operating parameters are and suspect that they may be different for different sites. For this reason, Openwind exposes these parameters for the user to experiment with.

The overshoot is the difference between the effective TI surface and the IEC class curve for the turbine. The fraction of the overshoot refers to where we draw the curtailment rectangle on any given peak within the effective TI surface. The figure below gives an example of this in practice. The rectangle can be drawn to take the upper X fraction of the peak or it can work in terms of % effective TI.

 

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Figure 150:  Example of Deriving WSM from Effective TI by Wind Speed and Direction

 

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