Torque limiter based on current torque value

A controller for controlling a wind turbine;

• the controller comprises:
• a control unit arranged for determining a control signal for controlling the wind turbine;
• a torque limit unit arranged for determining a current torque value of a rotor of the wind turbine and compare the current torque value to an upper torque limit value, if the current torque value is larger than the upper torque limit value, to instruct the control unit to modify the control signal so that a resulting torque value of the rotor is reduced, current torque values are included in a torque signal comprising previous torque values and the current torque value;
• a torque evaluation unit arranged for determining a lower envelope signal comprising previous lower envelope values and a current lower envelope value, wherein the upper torque limit value is based on a lower envelope signal, the lower envelope signal tracks the current torque value if the current torque value is lower than or equal to the previous lower envelope value and is set as a rising signal if the current torque value is higher than the previous lower envelope value, and wherein the upper torque limit is set to be a first amount higher than the lower envelope signal.

A wind turbine, comprising:

• a tower;
• a nacelle mounted rotatably on the tower;
• one or more pitchable wind turbine blades mounted rotatably on the nacelle via a hub;
• and
• a controller, comprising:
• a control unit arranged for determining a control signal for controlling the wind turbine;
• a torque limit unit arranged for determining a current torque value of a rotor of the wind turbine and compare the current torque value to an upper torque limit value, and if the current torque value is larger than the upper torque limit value, to instruct the control unit to modify the control signal so that a resulting torque value of the rotor is reduced, current torque values are included in a torque signal comprising previous torque values and the current torque value;
• and
• a torque evaluation unit arranged for determining a lower envelope signal comprising previous lower envelope values and a current lower envelope value, wherein the upper torque limit value is based on a lower envelope signal, the lower envelope signal tracks the current torque value if the current torque value is lower than or equal to the previous lower envelope value and is set as a rising signal if the current torque value is higher than the previous lower envelope value, and wherein the upper torque limit is set to be a first amount higher than the lower envelope signal.