A hydraulic pitch drive system for controlling a blade pitch angle of a wind turbine rotor has a hydraulic cylinder, for actuating blade pitch rotation, with a piston-side and rod-side. A first hydraulic proportional valve controls hydraulic fluid flow from a pressure port to the cylinder in response to a primary control signal. In an cylinder extending mode, the pressure port via the first hydraulic proportional valve is connected to the piston-side. The rod-side is connected to the pressure port via a non-return valve. A first control module provides the primary control signal in response to a pitch angle positioning request. A second hydraulic proportional valve controls hydraulic fluid flow from the rod-side to tank port independent of the first hydraulic valve, in response to a secondary control signal. A second control module provides the secondary control signal for controlling the second proportional valve in a hydraulic cylinder extending mode.

A method for detecting and reducing edgewise vibrations in a rotor blade of a wind turbine includes, for a given wind speed, determining a frequency or frequency band at which edgewise vibrations are producible in the rotor blade. The method determines an electrical characteristic of the pitch actuator that correlates to an increased torque required to hold a pitch angle of the rotor blade constant at the frequency or frequency band. During an operational power-production mode of the wind turbine, the electrical characteristic of the pitch actuator is monitored. Upon the electrical characteristic reaching a predefined limit value indicative of edgewise vibrations in the rotor blade, corrective action is initiated by the wind turbine controller to reduce or prevent the edgewise vibrations.

A hydraulic circuit for a wind turbine is provided. The hydraulic circuit includes: a fixed displacement pump including a suction input and a delivery output, a pump motor for driving the fixed displacement pump, a pressure line hydraulically connected to the delivery output of the fixed displacement pump for delivering an output flow and/or an output pressure generated by the fixed displacement pump towards at least a consumer circuit, a bypass valve including a valve input hydraulically connected to the delivery output of the fixed displacement pump, wherein the bypass valve includes a variable opening for controlling the output flow or the output pressure delivered by the fixed displacement pump towards the consumer circuit(s).

Wind turbine pitch actuator mounting structure A mounting structure is described for attaching a pitch actuator to a hub of a wind turbine. The mounting structure has one or more legs each having a proximal end and a distal end, and a flexible intermediate portion between the proximal and distal ends. The mounting structure further comprises an actuator attachment portion for attaching to a wind turbine blade pitch actuator. The actuator attachment portion is arranged at the distal end(s) of the one or more legs. The proximal end(s) of the one or more legs are configured for attachment to a wind turbine hub. The flexible intermediate portion(s) of the one or more legs are configured to flex in use to absorb loads acting on the pitch actuator. The mounting structure therefore allows the pitch actuator to pivot in a first plane by virtue of the flexible legs. The pitch actuator may be attached to the mounting structure via pivot bearings arranged to allow the pitch actuator to pivot in a second plane, substantially perpendicular to the first plane.

Embodiments herein describe a hydraulic pitch system where a velocity (e.g., the velocity of a hydraulic cylinder or the piston rod in the cylinder) is fed forward and combined with a setting outputted by a pitch controller. The velocity of the hydraulic cylinder is derived from the reference pitch angle or a continuous pitch signal (e.g., a cyclic pitch or ramp rate) in the control system. In either case, the velocity can be determined by monitoring the change in the reference pitch angle or the continuous pitch signal. Using a gain control, the velocity is converted into a position setting of the hydraulic pitch system (e.g., a spool setting in a valve) which is combined with another position setting generated by the pitch controller.

A rotor blade for a wind turbine is provided. The rotor blade includes an aerodynamic device for influencing the airflow flowing from the leading-edge section of the rotor blade to the trailing edge section of the rotor blade. The aerodynamic device is mounted at a surface of the rotor blade and includes a pneumatic or hydraulic actuator, such as a hose a cavity, of which the volume depends on the pressure of a fluid being present inside the pneumatic or hydraulic actuator. The rotor blade further includes a control unit for controlling the pressure of the fluid in the hose or the cavity of the aerodynamic device.

Provided is a method of controlling a pitch angle of at least one blade of a wind turbine by use of a hydraulic system, the hydraulic system including at least one reservoir configured to store a hydraulic fluid, and at least one pump configured to supply the hydraulic fluid from the reservoir to at least one accumulator, if a hydraulic fluid pressure in the accumulator falls below a lower threshold value and till the hydraulic fluid pressure in the accumulator exceeds an upper threshold value. The accumulator is configured to store the pressurized hydraulic fluid supplied by the pump and to supply the pressurized hydraulic fluid to at least one pitch control cylinder of the hydraulic system via at least one output valve of the hydraulic system. The pressurized hydraulic fluid in the pitch control cylinder drives at least one piston to change the pitch angle of the blade.

This invention regards a hydraulic turbine (1) to operate in pressure circuits, where there is a flow of a fluid, to control the flow and pressure downstream the installation point. Even so, said turbine (1) can generate power for itself based on the difference of pressure and flow, as the remaining power can be used in public power networks or isolated. Its application field comprises sanitation companies, beverage industries, paper and cellulose industries, petrochemical companies or any places, where it is needed to control the flow and pressure in supply networks.

A movable-blade operation system for a hydraulic machine according to an embodiment includes an oil hydraulic cylinder installed within a rotational shaft, a bidirectional pump, a pump drive motor, a control unit, and an oil head installed in the hydraulic machine. The bidirectional pump selectively feeds pressurized hydraulic oil to one of a first cylinder chamber and a second cylinder chamber. The oil head couples the rotational shaft rotatably, and the hydraulic oil fed from the bidirectional pump to the first cylinder chamber and the second cylinder chamber flows through the oil head. The bidirectional pump, the pump drive motor, and the control unit are installed outside the hydraulic machine.

A rotor turning device for balancing a rotor secured atop a tower of a wind turbine during installation and/or repair of one or more rotor blades of the wind turbine includes a hydraulic drive mechanism for operably engaging with a brake disc of the wind turbine. The brake disc is positioned adjacent to a gearbox of the wind turbine. The rotor turning device also includes a mounting device for securing the rotor turning device adjacent to the brake disc of the wind turbine. Thus, when the hydraulic drive mechanism engages the brake disc, the rotor is rotated to a desired position so as to position one or more rotor blades of the wind turbine in a balanced configuration.