What happens if the anemometer fails?
Many people do not realize that wind speed does not participate in the closed-loop control of wind turbine output.
That is to say, how much torque the excitation control system adds to the generator is not determined by the wind speed, but by the impeller speed, an indirect variable.
This is because our current anemometer at the tail of the nacelle cannot measure effective wind speed values. In fact, with the sweeping area of the entire impeller, the wind speed cannot be described by a single number at all.
In most control systems, wind speed measurements can only be used to make logical judgments:
Whether the wind speed is high enough to allow the unit to start running --- that is, the cut-in wind speed;
Is the wind speed out of the acceptable range of the unit - that is, cut out the wind speed;
Whether there is an extreme change in wind speed --- so-called extreme wind detection.
It doesn't look complicated. But what happens if the anemometer fails?
In the first case, if the failure can be self-checked by the anemometer and reflected in the control system, it is generally a failure shutdown, which is the simplest case;
In the second case, the unit is in shutdown state, and the failure of the anemometer generally leads to extremely low wind speed data, so the unit will not cut in;
In the third case, the unit is in grid-connected operation, but the anemometer fails, making the wind speed zero or too small. Because the general unit only judges that the wind speed is too high and cuts out, but if the wind speed is too small, no action will be triggered.
This situation is relatively easy to get out of the situation. Because, if the wind speed is much higher than the cut-out wind speed and the cut-out condition is not triggered, the unit will be overloaded, which is very dangerous, especially in some extreme weather.
Typically, due to icing of the anemometer, the wind speed measurement is less than 2 m/s, but the unit is operating at full capacity. If in this case, the wind speed continues to increase above the cut-out wind speed, but the unit continues to operate due to the failure of wind speed measurement, it may cause potential overload damage to the unit, or directly cause an accident.
