A wind turbine has a Lidar device to sense wind conditions upstream of the wind turbine. Signals from the wind turbine are processed to detect an extreme change in wind direction. The detection is performed by differentiating the rate of change of wind direction and filtering for a period of time. On detection of extreme change the system controller takes the necessary evasive action which may include shutting down the turbine, commencing an immediate yawing action, and de-rating the turbine until the yawing action is complete.

Provided is a control device for controlling a wind turbine, the wind turbine including a rotor and at least one blade being rotatable mounted to the rotor. The control device includes a detecting device being configured to detect an amount of a bending moment of the blade; and a change element having an input and an output, wherein the input is configured to receive the detected amount of the bending moment of the blade and the output is configured to output a response to a differential of the detected amount of the bending moment of the blade. The control device is configured to control the wind turbine based on the response.

A wave power generation system includes a wave receiving member, ram cylinder hydraulic pump device, change value sensor, accumulator device, hydraulic motor, power generator, and controller. The member is arranged near a virtual reflection surface that reflects a coming incident wave. The controller sets a torque command used when the generator generates electric power. Based on a differential value of a change value detected by the sensor and changes in accordance with a swing amount of the member, the controller determines whether the member is swinging toward a first or second side in a swing direction. When the controller determines the member is swinging toward the second side by receiving force of a reflected wave reflected by the virtual reflection surface, the controller changes the torque command from the command set when the controller determines the member is swinging toward the first side by receiving force of the incident wave.

A wave power generation system includes a wave receiving member, ram cylinder hydraulic pump device, change value sensor, accumulator device, hydraulic motor, power generator, and controller. The member is arranged near a virtual reflection surface that reflects a coming incident wave. The controller sets a torque command used when the generator generates electric power. Based on a differential value of a change value detected by the sensor and changes in accordance with a swing amount of the member, the controller determines whether the member is swinging toward a first or second side in a swing direction. When the controller determines the member is swinging toward the second side by receiving force of a reflected wave reflected by the virtual reflection surface, the controller changes the torque command from the command set when the controller determines the member is swinging toward the first side by receiving force of the incident wave.

Provided is a control device for controlling a wind turbine, the wind turbine including a rotor and at least one blade being rotatable mounted to the rotor. The control device includes a detecting device being configured to detect an amount of a bending moment of the blade; and a change element having an input and an output, wherein the input is configured to receive the detected amount of the bending moment of the blade and the output is configured to output a response to a differential of the detected amount of the bending moment of the blade. The control device is configured to control the wind turbine based on the response.