Control system for wind turbines in cold climates

1. A method for controlling a wind turbine, the method comprising:

determining, with a control system, that an icing event has begun to affect the wind turbine;

based on a determination that the icing event has begun to affect the wind turbine, changing a phase of the wind turbine with the control system to an operational-icing phase, wherein changing the phase of the wind turbine to the operational-icing phase comprises:

determining a modified angle of attack of blades of the wind turbine based on a current wind speed, current power production of the wind turbine, and baseline power production data; and

modifying an angle of attack of the blades of the wind turbine to the modified angle of attack via changing a blade pitch angle, wherein the wind turbine continues to generate electrical power when the wind turbine is in the operational-icing phase; and

based on a determination that electrical power generation of the wind turbine is below a threshold, changing the phase of the wind turbine with the control system to a stopped-icing phase, wherein rotation of the blades of the wind turbine is halted when the wind turbine is in the stopped- icing phase.

2. The method of claim 1 , further comprising:

prior to changing the phase of the wind turbine to the operational-icing phase and based on a determination that the icing event is likely to affect the wind turbine within an upcoming time period, changing the phase of the wind turbine to a pre-icing phase with the control system; and

while the wind turbine is in the pre-icing phase, generating the baseline power production data that associates electrical power production of the wind turbine with wind speed.

3. The method of claim 1 , wherein the rotation of the blades of the wind turbine is halted when the angle of attack of the blades of the wind turbine reaches a stall angle.

4. The method of claim 1 , further comprising based on the wind turbine entering the stopped-icing phase, turning trailing edges of the blades of the wind turbine toward a windward direction.

5. The method of claim 1 , further comprising:

determining that the icing event has ended; and

based on a determination that the icing event has ended, changing the phase of the wind turbine to a post-icing phase, wherein changing the phase of the wind turbine to the post-icing phase comprises changing performing actions to reduce an amount of ice that has accumulated on the blades of the wind turbine.

6. The method of claim 5 , wherein determining that the icing event has ended comprises determining that the icing event has ended based on loading information regarding the blades or tower of the wind turbine.

7. The method of claim 1 , wherein determining that the icing event has begun comprises determining that the icing event has begun based on loading information regarding the blades or tower of the wind turbine.

8. The method of claim 7 , further comprising obtaining the loading information from at least one of:

a torque sensor configured to detect torque produced by the blades of the wind turbine, or

one or more thrust sensors configured to detect forces acting on the blades of the wind turbine, or

one or more blade strain gauges or accelerometers to detect variations in deflection of the blades of the wind turbine, or

one or more tower strain gauges or accelerometers to detect increased imbalance of the wind turbine due to ice accretion.

9. The method of claim 1 , wherein determining that the icing event has begun comprises determining that the icing event has begun based on a weather forecast of temperature, relative humidity, and detection of precipitation.

10. A wind turbine control system comprising:

a communication unit configured to communicate with one or more controllers of a wind turbine; and

one or more processors configured to:

determine that an icing event has begun to affect the wind turbine;

based on a determination that the icing event has begun to affect the wind turbine, change a phase of the wind turbine with the control system to an operational-icing phase, wherein changing the phase of the wind turbine to the operational icing phase comprises:

determining a modified angle of attack of blades of the wind turbine based on a current wind speed, current power production of the wind turbine, and baseline power production data; and

modifying an angle of attack of the blades of the wind turbine to the modified angle of attack via changing blade pitch angles, wherein the wind turbine continues to generate electrical power when the wind turbine is in the operational-icing phase; and

based on a determination that electrical power generation of the wind turbine is below a threshold, change the phase of the wind turbine with the control system to a stopped-icing phase, wherein rotation of the blades of the wind turbine is halted when the wind turbine is in the stopped-icing phase.

11. The wind turbine control system of claim 10 , wherein the one or more processors are further configured to:

prior to changing the phase of the wind turbine to the operational-icing phase and based on a determination that the icing event is likely to affect the wind turbine within an upcoming time period, change the phase of the wind turbine to a pre-icing phase with the control system; and

while the wind turbine is in the pre-icing phase, generate the baseline power production data that associates electrical power production of the wind turbine with wind speed, while the.

12. The wind turbine control system of claim 10 , wherein the rotation of the blades of the wind turbine is halted when the angle of attack of the blades of the wind turbine reaches a stall angle.

13. The wind turbine control system of claim 10 , wherein the one or more processors are configured to, based on the wind turbine entering the stopped-icing phase, cause the wind turbine to turn trailing edges of the blades of the wind turbine toward a windward direction.

14. The wind turbine control system of claim 10 , wherein the one or more processors are configured to:

determine that the icing event has ended; and

based on a determination that the icing event has ended, change the phase of the wind turbine to a post-icing phase, wherein the one or more processors are configured to, as part of changing the phase of the wind turbine to the post-icing phase, cause the wind turbine to perform actions to reduce an amount of ice that has accumulated on the blades of the wind turbine.

15. The wind turbine control system of claim 14 , wherein the one or more processors are configured to, as part of determining that the icing event has ended, determine that the icing event has ended based on loading information regarding the blades or tower of the wind turbine.

16. The wind turbine control system of claim 10 , wherein the one or more processors are configured to, as part of determining that the icing event has begun, determine that the icing event has begun based on loading information regarding the blades or tower of the wind turbine.

17. The wind turbine control system of claim 16 , wherein the one or more processors are further configured to obtain the loading information from at least one of:

a torque sensor configured to detect torque produced by the blades of the wind turbine, or

one or more thrust sensors configured to detect forces acting on a rotor of the wind turbine, or

one or more blade strain gauges or accelerometers to detect variations in deflection of the blades of the wind turbine, or

one or more tower strain gauges or accelerometers to detect increased imbalance of the wind turbine due to ice accretion.

18. The wind turbine control system of claim 10 , wherein the one or more processors are configured to determine that the icing event has begun based on a weather forecast of temperature, relative humidity, and detection of precipitation.

19. A non-transitory computer-readable data storage medium having instructions stored thereon that, when executed, cause one or more processors to:

determine that an icing event has begun to affect a wind turbine;

based on a determination that the icing event has begun to affect the wind turbine, change a phase of the wind turbine with a control system of the wind turbine to an operational-icing phase, wherein changing the phase of the wind turbine to the operational-icing phase comprises:

determining a modified angle of attack of blades of the wind turbine based on a current wind speed, current power production of the wind turbine, and baseline power production data; and

modifying an angle of attack of the blades of the wind turbine to the modified angle of attack via changing a blade pitch angle, wherein the wind turbine continues to generate electrical power when the wind turbine is in the operational-icing phase; and

based on a determination that electrical power generation of the wind turbine is below a threshold, change the phase of the wind turbine with the control system to a stopped-icing phase, wherein rotation of the blades of the wind turbine is halted when the wind turbine is in the stopped- icing phase.

20. The non-transitory computer-readable data storage medium of claim 19 , wherein the instructions, when executed, further cause the one or more processors to:

prior to changing the phase of the wind turbine to the operational-icing phase and based on a determination that the icing event is likely to affect the wind turbine within an upcoming time period, change the phase of the wind turbine to a pre-icing phase with the control system; and

while the wind turbine is in the pre-icing phase, generate the baseline power production data that associates electrical power production of the wind turbine with wind speed.