Automatic pitch and yaw angle optimization tested succesfully.

by J. Schuurmans

DotX has succesfully developed, implemented and tested the optimization of the fine-pitch angles, and yaw angle.

The pitch angles of a wind turbine are initially set by a mechanic using a screwdriver, or a button to fix the angle at which the blade is supposed to be at when at 0 degrees (the fine pitch angle). The mechanic aligns the markers on the blade and in the nose-cone of the turbine to do so. With our automatic control procedure, the wind turbine computer first adjusts the relative pitch angles to minimise rotor unbalance. After that, the computer adjusts all blade angles in unison to find the optimal fine pitch angle that maximises power output of the turbine.

A similar procedure has been developed for the yaw angle: the yaw angle is varied in cycles, each lasting a fixed amount of time, until the optised yaw angle has been found, such that power output is maximised. The graph below shows how the optimal yaw offset converges to its final value, within approximately 100 cycles (that correspond to 30 ‘effective’ hours, i.e. hours where the turbine operates in the right conditions). In this graph, the wind vane had been calibrated first with the aid of a LIDAR, to allow us checking the optimsed yaw angle. The LIDAR based yaw misalignment, shown as a black line, confirms the result.

Tests show that oscillations can be reduced by more than 80%, while yield can be improved 3-6% per year. The optimization procedures uses standard on-board sensors only. After optimization, a PV curve difference of ‘before’ and ‘after’ is generated that cane be used to calculate the exact yield improvement. This procedure has been verified by a certification institute and has been applied to over 20 wind turbines in the field.