The present disclosure relates to a method of operating a wind turbine, a corresponding wind turbine, a method of controlling a wind farm and a corresponding wind farm. The method comprises the steps of: determining a target maximum active power to be fed by the wind turbine into a power grid, in particular into an electricity power grid; monitoring a current active power fed from the wind turbine into the power grid; determining a reference time period corresponding to the determined target maximum active power; deriving an average of the active power fed from the wind turbine into the power grid during the reference time period; comparing the average of the active power with the target maximum active power; and operating the wind turbine at a set operating point permitting active power above the target maximum active power in case the average of the active power is below the target maximum active power.

The application relates to an oscillation active damping control method and system for grid-tied type-4 wind turbine generator. The method comprises: based on an interconnection model of multiple subsystems, constructing a stored energy function and a dissipated energy function of a current inner loop control subsystem, and interaction energy functions between the current inner loop control subsystem and other subsystems are constructed, then establishing an energy feedback model of Type-4 wind turbine generator; when the oscillation occurs, obtaining instantaneous angular frequency of the PLL, and then based on the energy feedback model, adjusting the current reference value of the q-axis current inner loop generated by the reactive power outer loop control subsystem, to make the stored energy function decrease with time, so as to suppress the oscillation.

A method of controlling a wind power plant including an energy storage device, the wind power plant being connected to a power grid and comprising one or more wind turbine generators that produce electrical power for delivery to the power grid, the method comprising: processing input data related to one or more inputs to the wind power plant to determine a probability forecast for each input; and controlling charging and discharging of the energy storage device in accordance with each probability forecast and a prescribed probability of violating one or more grid requirements.

Provided is a lubrication system for a drive train of a wind turbine including a main oil tank including a lubrication liquid, for lubricating the drive train when the wind turbine has connection to a grid and a main reservoir which is separate from the main oil tank and contains lubrication liquid for the drive train when the wind turbine has no connection to the grid. The main reservoir includes a first reservoir containing a first amount of lubrication liquid for at least a first component of the drive train and a second reservoir including a second amount of lubrication liquid for at least a second component of the drive train. The lubrication system is configured to supply the oil from the main reservoir to the drive train when the wind turbine has no grid connection for creating an oil sump in at least the second component of the drive train.

A method (1000-1001) for operating a wind turbine (100) including a rotor (106) having rotor blades (108) and a power conversion system (118, 210, 234) mechanically connected with the rotor (106), configured to convert input motive power into electrical output power, and electrically connected to a network (242) for feeding the electrical output power (P) to the network is provided. The method includes determining (1100) a current frequency (f) of the network (242), and, when the current frequency (f) is equal to or lower than a threshold frequency (f.sub.thresh), operating (1300) the power conversion system (118, 210, 234) at an electrical output power (P) which is increased by an electrical output power increase (PI) in accordance with a monotonic function (PI(f)) of the current frequency (f) limited to a maximum value (PI.sub.max).

A method (2000) for operating a wind turbine (100) including a rotor (106) having rotor blades (108) and a power conversion system (118, 210, 234) mechanically connected with the rotor (106), configured to convert input motive power into electrical output power, and electrically connected to a network (242) for feeding the electrical output power (P) to the network is provided. The method includes initializing (2000), at a first time (t.sub.0), the wind turbine to operate in an overproduction operating mode in which the electrical output power (P(t)) of the power conversion system is increased from an initial electrical output power of the power conversion system by providing kinetic energy stored in the rotor. At a second time (t.sub.2), decreasing (2200) the electrical output power, and integrating a reference power (P.sub.ref, P.sub.0) to determine an energy recovery value (E.sub.rec) are started. An energy response value (E.sub.resp) corresponding to a product of the reference power (P.sub.ref) with a time difference (T.sub.resp) between the second time and the first time is determined (2300). The wind turbine is operated (2400) in a recovery operating mode from a third time (t.sub.3) at which the electrical output power (P) reaches or crosses the reference power (P.sub.ref, P.sub.0) until the energy recovery value becomes at least equal to the energy response value or until the electrical output power reaches or crosses the reference power again from below. In the recovery operating mode, the electrical output power is, limited upwards depending on the reference power and a currently available maximum electrical power output without reducing a speed of the rotor.

A method for controlling a power output of a power generating unit is disclosed. An accumulated power output of the power generating unit during a predefined time interval is forecasted. An actual power output of the power generating unit is measured during the predefined time interval, and an actual accumulated power output is estimated for the predefined time interval on the basis of the measured actual power output of the power generating unit. A difference between the forecasted accumulated power output and the estimated actual accumulated power output is derived. The power output of the power generating unit is boosted, in the case that the estimated actual accumulated power output is below the forecasted accumulated power output, and the difference between the forecasted accumulated power output and the estimated actual accumulated power output is larger than a predefined threshold value.

Provided is a method for feeding electric power into an electricity supply grid via a connection node by way of a converter-controlled infeed unit, in particular by way of a wind power installation or a wind farm. The grid has a grid voltage and a grid frequency and is characterized by a grid nominal voltage and a grid nominal frequency. The grid voltage of the grid is acquired, a delayed differential angle is ascertained on the basis of the acquired grid voltage. The delayed differential angle corresponds to a difference between an acquired phase signal that indicates a temporal profile of a phase angle of the grid voltage and a phase signal that is delayed with respect to the acquired phase signal. A grid impedance effective for the connection node is acquired, and an infeed power is predefined based on the delayed differential angle and based on the impedance.

The invention relates to a method for operating a wind turbine which comprises a power generator, a generator side converter, a grid side converter, a DC link electrically connected to an output of the generator side converter and an input of the grid side converter. The method comprises monitoring a wind turbine signal for detection of an operational condition which requires an increase of an output voltage of the grid side converter, upon detection of the operational condition, initiate an over-modulation mode wherein the grid side converter is operated with a modulation index in an over-modulation range, and upon the detection of the operational condition, initiate a DC-voltage adjustment mode wherein the a DC-voltage of the DC link is increased from a first voltage level towards a second voltage level.

A method of controlling an induction generator is provided connected to a utility grid, the method including: receiving an actual grid frequency; and controlling rotor windings of the generator by a rotor control signal having a rotor winding reference frequency being set in dependence of the actual grid frequency.