Abstract: A method is provided for braking a rotor of a wind turbine. The rotor comprises rotor blades. The wind turbine comprises a pitch adjustment system for adjusting a pitch of the rotor blades. The method comprises detecting a system failure of the pitch adjustment system, estimating a current wind speed, estimating an available brake torque and estimating a required brake torque, based on the estimated current wind speed. The method further comprises determining a suitable point in time for activating a rotor brake, based on the estimated available brake torque and the estimated required brake torque. The rotor brake is then activated at the determined suitable point in time.

Abstract: A method is provided for braking a rotor of a wind turbine. The rotor comprises rotor blades. The wind turbine comprises a pitch adjustment system for adjusting a pitch of the rotor blades. The method comprises detecting a system failure of the pitch adjustment system, estimating a current wind speed, estimating an available brake torque and estimating a required brake torque, based on the estimated current wind speed. The method further comprises determining a suitable point in time for activating a rotor brake based on the estimated available brake torque and the estimated required brake torque. The rotor brake is then activated at the determined suitable point in time.

Abstract: A wind turbine system is described comprising a plurality of wind turbine modules, each including a rotor, mounted to a support structure including a tower. In use, each rotor has an associated rotating unbalance that defines an unbalance vector. The wind turbine system includes control means configured to coordinate the rotational speeds of the plurality of rotors to attenuate oscillations of the support structure caused by the rotating unbalance of the rotors. Also described is a method of controlling such a wind turbine system. The method comprises coordinating the rotational speeds of the plurality of rotors to attenuate oscillations of the support structure caused by the rotating unbalance of the rotors.

Abstract: A wind turbine system is described comprising a plurality of wind turbine modules, each including a rotor, mounted to a support structure including a tower. In use, each rotor has an associated rotating unbalance that defines an unbalance vector. The wind turbine system includes control means configured to coordinate the rotational speeds of the plurality of rotors to attenuate oscillations of the support structure caused by the rotating unbalance of the rotors. Also described is a method of controlling such a wind turbine system. The method comprises coordinating the rotational speeds of the plurality of rotors to attenuate oscillations of the support structure caused by the rotating unbalance of the rotors.