Provided is a method for operating wind energy converters, in particular of a wind farm. The power limitation mode in this case comprises the steps of turning off at least one of the wind energy converters and operating at least one wind energy converter different to the turned-off wind energy converter, activating a generator heating of the turned-off wind energy converter, turning off the working wind energy converter at or after occurrence of a predefined event, in particular after a predefined time period has elapsed or when a predefined instant is reached, and activating the generator heating of the wind energy converter turned off at or after the occurrence of the predefined event. Provided is a wind farm and to a wind energy converter for carrying out such a method.

A wind turbine includes a tower, an aerodynamic rotor operable at a variable rotor speed and having a plurality of rotor blades each having an adjustable rotor blade setting angle and a generator for generating an electrical output power. An operating characteristic curve is prespecified for operating the wind turbine. The operating characteristic curve indicates a relationship between the rotor speed and the output power. A controller is provided, which sets the output power in accordance with the operating characteristic curve depending on the rotor speed. The the operating characteristic curve has a starting rotation speed to which the rotor speed increases as soon as the wind turbine starts when a sufficient wind speed is reached. The starting rotation speed is defined depending on a tower natural frequency of the wind turbine and/or depending on a detected turbulence measure of the prevailing wind.

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.

A method of controlling a power system that includes an electrical machine, e.g., wind turbine generator, a power converter, a DC circuit and a dynamic braking system (DBS) having a braking circuit having a braking resistor and being connected in series to the DC circuit, is provided. The method includes operating the DBS and controlling operation of the electrical machine based on a prevailing temperature of the braking circuit, stopping the electrical machine and controlling the electrical machine to be restarted at its rated output power once the prevailing temperature of the braking resistor reaches or falls below a lower temperature threshold. The electrical machine may be restarted at a lower output power and after restarting, its output power can be increased based on a power starting profile as the braking resistor cools.

A wind turbine comprises a permanent magnet synchronous generator, a main converter, a main converter controller, a wind turbine master controller and an electrical power supply stage comprising an electrical energy storing device. A startup of the wind turbine can be performed using electrical energy from the electrical energy storing device independent from a power supplying grid and/or a combustion engine. After startup, the wind turbine can be operated in an island mode by controlling an intermediate voltage of the main converter by the main converter controller and retrieving power from the synchronous generator independent from the electrical energy storing device.

Methods for black-starting an electrical grid (2) are described herein. For example, a method comprises disconnecting the wind farm (1) from the grid at a first location, said first location being located between the electrical grid (2) and the energy storage (16) with the associated converter (17), energizing the AC export cable (12) using said energy storage (16) and the associated converter (17), energizing at least one part of the wind farm electrical infrastructure via said export cable (12) using said energy storage (16) and the associated converter (17), re-establishing energy supply to said wind farm electrical infrastructure by said wind turbine generators (3, 4), and reconnecting the wind farm (1) to said electrical grid (2) at said first location.

A system for generating its own air currents to run electric turbines. The system includes: a vertical tower or support provided with a rotating disk at its upper end, up to four laterally extending arms connected to the disk, each arm carrying a wind turbine generator with rotating blades/rotors attached at its outer end, a planetary gear system having a central sun gear and motor associated with the rotating disk and a main controller system connected to the vertical tower base, wherein the main control system controlling the startup input source from a state power supply system and a solar system supply operating the central motor.

A bearing protection arrangement of a journal bearing arranged between a housing and a rotary component of a wind turbine is provided. The bearing protection arrangement includes a wind speed monitor arranged to monitor wind speed in the vicinity of the wind turbine and to generate a wake-up signal when the wind speed exceeds a pre-defined minimum; a mode switch module of a backup battery arranged to provide restart power to an auxiliary of the wind turbine, which mode switch module is adapted to switch the backup battery from a normal-power mode into a low-power mode to conserve sufficient restart power after low wind-speed conditions, and to switch the backup battery from the low-power mode into a normal-power mode in response to the wake-up signal. A wind turbine and a method of protecting a journal bearing of a wind turbine during standstill is also provided.

A system and method for operating a wind farm connected to a power grid, the wind farm having one or more wind turbines includes implementing a shutdown mode for the one or more wind turbines of the wind farm in response to receiving a shutdown command. The shutdown mode includes disconnecting the one or more wind turbines of the wind farm from the power grid via one or more respective individual turbine controllers and reducing, via the individual turbine controllers, a rotor speed of the one or more wind turbines to a cut-in speed. After the shutdown command is cleared, the method further includes reconnecting the one or more wind turbines to the power grid.

A wind turbine arrangement including a first rotatable blade arrangement and a second rotatable blade arrangement. The first blade arrangement forms part of a first wind turbine, and the second blade arrangement forms part of a second wind turbine. The second wind turbine can produce a rotative force to the first wind turbine. At wind speeds below that required to operate the first turbine, the second turbine may be operable and provide power to rotate the first turbine.