Abstract: A method for controlling a multirotor wind turbine is disclosed. A first operational state of each of the energy generating units of the wind turbine is obtained. A difference in thrust acting on at least two of the energy generating units is detected. At least one constraint parameter of the set of operational constraints is adjusted in accordance with prevailing operating conditions and in accordance with the detected difference in thrust, and a new operational state for at least one of the energy generating units is derived, based on the at least one adjusted constraint parameter, the new operational state(s) counteracting the detected difference in thrust. Finally, the wind turbine is controlled in accordance with the new operational states for the energy generating units.

Abstract: The invention relates to a method for monitoring performance of a multi-rotor wind turbine. According to the method parameter for each of the wind turbine modules of the multi-rotor wind turbine is obtained. The parameters of each of the wind turbine modules are compared, e.g. by means of a comparison parameter determined from the individual parameters. Dependent on the result of the comparison, a performance action is initiated, e.g. for the purpose of further characterization or verification of a deviating parameter determined via the comparison.

Abstract: The invention relates to a wind turbine system comprising a support structure with a plurality of wind turbine modules mounted to the support structure. A control system is arranged to enter a service mode wherein service can be performed in the wind turbine system by applying a first control command to a first subset of wind turbine modules for terminating power production. A second control command is applied to a second subset of wind turbine modules for bringing the second subset of wind turbine modules into an damping mode where each of the wind turbine modules of the second subset is operated and/or positioned to damp vibrations, actively and/or passively, of at least one wind turbine module of the first subset of wind turbine modules.

Abstract: The invention relates to a wind turbine system (1) with several wind turbine modules (2) mounted to a support structure (3). A control system is configured to determine a lift command (21) for a particular wind turbine module (2?) of the 5 plurality of wind turbines modules (2). The control system is applying the lift command (21) to a corresponding rotor blade pitch adjustment system of the particular wind turbine module (2?) so as to create a lift force (F_up) in the opposite direction of gravity on the particular wind turbine module mounted on the support structure. Providing an upwards lift force on one, or more, particular 10 wind turbine module(s) may reduce, or eliminate, static and/or dynamical loads from the wind turbine module on the support structure.

Abstract: The invention relates to a method for monitoring performance of a multi-rotor wind turbine. According to the method parameter for each of the wind turbine modules of the multi-rotor wind turbine is obtained. The parameters of each of the wind turbine modules are compared, e.g. by means of a comparison parameter determined from the individual parameters. Dependent on the result of the comparison, a performance action is initiated, e.g. for the purpose of further characterization or verification of a deviating parameter determined via the comparison.

Abstract: A method for controlling a multirotor wind turbine is disclosed. A first operational state of each of the energy generating units of the wind turbine is obtained. A difference in thrust acting on at least two of the energy generating units is detected. At least one constraint parameter of the set of operational constraints is adjusted in accordance with prevailing operating conditions and in accordance with the detected difference in thrust, and a new operational state for at least one of the energy generating units is derived, based on the at least one adjusted constraint parameter, the new operational state(s) counteracting the detected difference in thrust. Finally, the wind turbine is controlled in accordance with the new operational states for the energy generating units.

Abstract: There is presented a wind turbine system, wherein the wind turbine system is comprising a support structure, a plurality of wind turbine modules mounted to the support structure wherein each of the plurality of wind turbine modules comprises a rotor, and wherein the wind turbine system further comprises a control system, wherein the control is arranged to execute a wind turbine system transition from a first system operational state of the wind turbine system to a second system operational state of the wind turbine system, and wherein the wind turbine system transition is performed by executing a plurality of wind turbine module transitions from a first module operational state of a wind turbine module to a second module operational state of the wind turbine module wherein the plurality of wind turbine module transitions are distributed in time with respect to each other.

Abstract: The invention relates to a wind turbine system comprising a support structure with a plurality of wind turbine modules mounted to the support structure. A control system is arranged to enter a service mode wherein service can be performed in the wind turbine system by applying a first control command to a first subset of wind turbine modules for terminating power production. A second control command is applied to a second subset of wind turbine modules for bringing the second subset of wind turbine modules into an damping mode where each of the wind turbine modules of the second subset is operated and/or positioned to damp vibrations, actively and/or passively, of at least one wind turbine module of the first subset of wind turbine modules.

Abstract: The present invention relates to control of a wind turbine system comprising a plurality of wind turbine modules mounted to a common support structure, i.e. to control of a multi-rotor wind turbine system. The invention discloses a control system for a multi-rotor wind turbine system which comprises local controllers operable to control the wind turbine modules in accordance with local control objectives and a central controller configured to monitor the operation of the wind turbine system and based thereon calculate the local control objectives. The central controller is implemented as a model predictive controller (MPC).

Abstract: The invention is directed to a wind turbine system comprising a first pair of wind turbines mounted to a support structure by a first support arm arrangement, and a second pair of wind turbines mounted to the support structure by a second support arm arrangement. The first and second support arm arrangements are mounted to the support structure at a respective yaw unit so as to yaw about the major axis of the support structure. Moreover, the wind turbine system further includes a control system that is configured to control the yaw angle of each of the first and second support arm arrangements, wherein the control system is configured to identify the presence of a predetermined shutdown condition and, in response, the control system is operable to control the yaw angles of the first support arm arrangement and the second support arm arrangement to a predetermined safe state.

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 comprising a plurality of wind turbines mounted to a common support structure, wherein each of the plurality of wind turbines includes a rotor and a power generation system driven by the rotor, wherein the wind turbine system further comprises: localised control means including a plurality of local control modules, wherein each of the local control modules is operable to monitor the operation of a respective one of the plurality of wind turbines, and to issue local control commands thereto to achieve a set of local control objectives; and centralised control means configured to monitor the operation of the wind turbine system and provide centralised control commands to the plurality of wind turbines in order to achieve a set of supervisory control objectives associated with at least two of the plurality of wind turbines.

Abstract: A method for erecting a multirotor wind turbine (10) is disclosed. A carrier structure (1, 1a, 1b) is arranged circumferentially with respect to a tower structure (2) and hoisted to an upper part of the tower structure (2), using a hoisting arrangement, such as a wire winch arrangement (3, 4, 8). Furthermore, energy generating units (5) may be hoisted to the carrier structure (1, 1a, 1b) using the hoisting arrangement (3, 4, 8). A similar method for dismantling a multirotor wind turbine (10) is also disclosed. The multirotor wind turbine (10) can be erected or dismantled without the need for an external crane.

Abstract: The invention relates to a method of controlling a wind turbine, the wind turbine comprising wind turbine blades attached to a rotor hub and a control system for pitching the blades relative to the rotor hub. The method comprises determining a wind speed and providing a normal pitch mode of operation to control the output power of the wind turbine, where the pitch mode of operation comprises pitch reference values in dependence of the wind speed. The output power of the turbine is controlled according to the normal pitch mode of operation as a function of the wind speed if the wind speed is lower than a first upper level wind speed threshold, and according to a modified mode of operation if the wind speed exceeds the first upper level threshold wind speed, wherein the modified mode of operation comprises decreasing the output power according to a de-rating function which is a function of time.

Abstract: A wind turbine system comprising a plurality of wind turbines mounted to a support structure including a tower, wherein each of the plurality of wind turbines includes a rotor and a power generation system driven by the rotor, and at least one of a rotor blade pitch adjustment means and a generator power control means. The system further includes control means that receives vibration data associated with the support structure and which is configured to determine a damping control command for a respective one of the plurality of wind turbines, wherein the or each of the wind turbines includes a damping controller that receives a damping control command and which is operable to apply a damping control input to one or both of the blade pitch adjustment means and the generator power control means so as to counteract the measured vibration of the support structure.

Abstract: The invention relates to a wind turbine system (1) with several wind turbine modules (2) mounted to a support structure (3). A control system is configured to determine a lift command (21) for a particular wind turbine module (2?) of the 5 plurality of wind turbines modules (2). The control system is applying the lift command (21) to a corresponding rotor blade pitch adjustment system of the particular wind turbine module (2?) so as to create a lift force (F_up) in the opposite direction of gravity on the particular wind turbine module mounted on the support structure. Providing an upwards lift force on one, or more, particular 10 wind turbine module(s) may reduce, or eliminate, static and/or dynamical loads from the wind turbine module on the support structure.

Abstract: There is presented a wind turbine system, wherein the wind turbine system is comprising a support structure, a plurality of wind turbine modules mounted to the support structure wherein each of the plurality of wind turbine modules comprises a rotor, and wherein the wind turbine system further comprises a control system, wherein the control is arranged to execute a wind turbine system transition from a first system operational state of the wind turbine system to a second system operational state of the wind turbine system, and wherein the wind turbine system transition is performed by executing a plurality of wind turbine module transitions from a first module operational state of a wind turbine module to a second module operational state of the wind turbine module wherein the plurality of wind turbine module transitions are distributed in time with respect to each other.

Abstract: To identify abnormal behavior in a turbine blade, a failure detection system generates a “fingerprint” for each blade on a turbine. The fingerprint may be a grouping a dynamic, physical characteristics of the blade such as its mass, strain ratio, damping ratio, and the like. While the turbine is operating, the failure detection system receives updated sensor information that is used to determine the current characteristics of the blade. If the current characteristics deviate from the characteristics in the blade's fingerprint, the failure detection system may compare the characteristics of the blade that deviates from the fingerprint to characteristics of another blade on the turbine. If the current characteristics of the blade are different from the characteristics of the other blade, the failure detection system may change the operational mode of the turbine such as disconnecting the turbine from the utility grid or stopping the rotor.

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 comprising a plurality of wind turbines mounted to a common support structure, wherein each of the plurality of wind turbines includes a rotor and a power generation system driven by the rotor, wherein the wind turbine system further comprises: localised control means including a plurality of local control modules, wherein each of the local control modules is operable to monitor the operation of a respective one of the plurality of wind turbines, and to issue local control commands thereto to achieve a set of local control objectives; and centralised control means configured to monitor the operation of the wind turbine system and provide centralised control commands to the plurality of wind turbines in order to achieve a set of supervisory control objectives associated with at least two of the plurality of wind turbines.