The present invention relates to blade monitoring of a wind turbine by actively promoting blade vibrations by imposing a pitch actuation signal. A method of operating a wind turbine is disclosed where for each blade of a wind turbine, vibrations of the blade are actively promoted by imposing a pitch actuation signal to the pitch actuator, and at least one parameter relating to the blade vibration is determined.

A method of generating power. An airborne power generating craft is connected to a floating structure using an aloft portion of a tether line. The floating structure is connected to an anchor using an underwater portion of the tether line. The anchor is secured to an underwater floor. Power is generated based on movement of the airborne power generating craft in response to a wind force. The floating structure is connected to an electrical transmission system through at least part of the tether line. The generated power is transmitted to the electrical transmission system.

A method of maintaining an offshore power plant. A plurality of airborne power generating craft are landed on or near a floating vessel. Each of the plurality of airborne power generating craft forms part of the offshore power plant.

A wind power generation system has a windmill, a lift improvement device, a power generator, a storage, and a controller. The windmill rotates when receiving an airflow. The lift improvement device has a capability of operating and halting, the lift improvement device increases a lift force to a blade of the windmill when operating. The power generator generates power by rotation of the windmill and a torque is generated in a direction suppressing rotation of the windmill. The storage stores a plurality of characteristic maps indicating characteristics of the torques of the power generator in relation to rotation speeds of the power generator. The controller controls a power generation amount of the power generator by switching and using the plurality of characteristic maps of the storage in correspondence with a state of operating or halting of the lift improvement device.

A method of de-icing a wind turbine blade (5) comprises the steps of: generating heated air using heating means (10) provided in the root portion of the blade; and continuously circulating the heated air around the interior of the blade through at least a portion of two more longitudinal blade cavities (24, 26, 28) defined within the blade. The circulating step includes: channeling the heated air from an outlet (32a) of the heating means at least part way through a first longitudinal blade cavity (26), towards the tip end (18) of the blade; at a position along the length of the blade, diverting the heated air from the first longitudinal blade cavity (26) into a second longitudinal blade cavity (24); and channeling the diverted air at least part way through the second longitudinal blade cavity (24) back to an inlet (34) of the heating means (10). The heated air is circulated through at least a central cavity (24) and a leading edge cavity (26) defined between longitudinal webs (22) within the blade.

System and methods for optimizing operation of a wind turbine are disclosed. In one aspect, the method also includes determining, via a converter controller of a power converter, a tap position of a tap changer configured between the power grid and a primary winding of a transformer. Another step includes calculating, via the converter controller, a primary voltage of the primary winding as a function of the tap position. The method also includes implementing, via the converter controller, a control action if the primary voltage or a measured secondary voltage of a secondary winding of the transformer is outside of a predetermined voltage range.

A method for controlling an inclination of a floating wind turbine platform to optimize power production, or to reduce loads on the turbine, tower, and platform, or both, includes receiving data associated with the inclination of the floating wind turbine platform and wind speed and direction data. An angle of difference between the turbine blade plane and the wind direction is determined, where the angle of difference has a vertical component. A platform ballast system is then caused to distribute ballast to reduce the vertical component to a target angle chosen to optimize power production, or reduce turbine, tower, and platform loads, or both.

A proactive method prevents vibrations in one or more rotor blades of a wind turbine when the wind turbine is in a standstill idling state with a rotor hub free to rotate. The method determines a minimum revolution rate of the rotor blades that prevents vibrations of the rotor blades and that the actual revolution rate of the rotor blades is below the minimum revolution rate. A wind parameter is detected and determined to be above a threshold limit. The method also detects if grid power is available for pitching the rotor blades. Based on the wind parameter, a controller determines a pitch angle for one or more of the rotor blades to increase rotation of the blades to at least the minimum revolution rate. The controller initiates pitching the rotor blades to increase the revolution rate of the rotor blades prior to vibrations being induced in the rotor blades.

A wind turbine has a Lidar device to sense wind conditions upstream of the wind turbine. Wind speed signals from the wind turbine are processed to detect an extreme operating gust. The detection is performed by differentiating the axial wind velocity and filtering for a period of time. On detection of extreme operating gust the system controller takes necessary evasive action which may include shutting down the turbine or varying the blade pitch angle.

A wind turbine converter system with a rectifier and an inverter and a converter controller has at least first and second converter strings. The converter system is controlled by a master-converter controller and a slave-converter controller. The master-converter controller controls the first converter string and the slave-converter controller controls the second converter string. The master-converter controller receives commands from a superordinate wind turbine controller, provides the slave-converter controller with string-control commands on the basis of the superordinate control commands, and controls the conversion operation of the first converter string on the basis of the superordinate control command. The slave-converter controller receives the string-control commands from the master-converter controller and controls the conversion operation of the second converter string on the basis of the string-control commands received. The first and the second converter strings can be arranged in a bipolar configuration giving access to a neutral point. Fault detection can be performed based on current through the neutral. The system is capable of fault ride-through. Also, in case of failure of the master-converter controller, a redundant unit takes its place.