Provided is a method for controlling a wind power installation, an associated closed-loop controller, an associated installation and a wind farm. The installation has an aerodynamic rotor which is operated at a variable rotating speed and has rotor blades that have adjustable blade angles. The installation in at least one operating range is closed-loop controlled by a closed-loop rotating speed control in which the rotating speed by adjusting a rotor status variable of the rotor blades is closed-loop controlled to a rotating speed target value, referred to as the target rotating speed. The closed-loop rotating speed control for adjusting the rotor status variable includes the use of a reserve value. In the event that the installation is not yet operating at a target output or a target moment, the reserve is obtained from a comparison of the target output or target moment and a momentary output or a momentary moment.

Embodiments herein describe operating wind turbines in an offshore park to provide auxiliary power to a local AC grid or to an onshore grid during a grid malfunction. In one embodiment, the offshore park is coupled via a HVDC link to an onshore grid. When the HVDC link is down, a substation in the park includes a backup generator for creating a weak grid for powering auxiliary systems in a pilot turbine. The wind turbines in the park can switch to an auxiliary control system help power the auxiliary systems in the substation and in other turbines. In another embodiment, the offshore park is AC coupled to an onshore grid using a transformer in the substation. The wind turbines can participate in a brown or black start following a grid fault by switching to operating using the auxiliary control system.

A system and method are provided for controlling a power generating subsystem connected to a power generating system at a point of interconnection (POI). A subsystem controller receives a feedback first data signal corresponding to an electrical parameter for reactive power or power factor contributed by the power generating subsystem to the POI, the first data signal having a first signal fidelity. The subsystem controller receives a second data signal indicative of the electrical parameter measured at the power generating subsystem and having a second signal fidelity higher than the first signal fidelity. The subsystem controller generates a correlation value between the first and second data signals and applies the correlation value to modify a setpoint value for the electrical parameter at the POI. The subsystem controller uses the modified setpoint value and the second data signal to generate a setpoint command for the power generating subsystem.

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 feeding electrical power into an electrical, three-phase supply network by means of an inverter device, wherein the electrical supply network has a three-phase line voltage with a first, second and third line voltage phase, comprising the steps: feeding the electrical power during normal operation if a fault-free operation has been identified for the electrical supply network, wherein during normal operation a positive sequence voltage and optionally a negative sequence voltage is recorded from the line voltage and a reactive current is specified at least depending on the positive sequence voltage and optionally depending on the negative sequence voltage, and changing to a fault operation if a voltage change in the line voltage meets a predetermined fault criterion, in particular if the voltage change exceeds a predeterminable minimum amount of change or a minimum amount of change gradient, wherein during the fault operation, at least directly after the change, the reactive current is specified depending on a space vector voltage.

A method for controlling an inverter-based resource (IBR) having a power converter connected to an electrical grid includes receiving a first power limit signal for the IBR from an external controller, receiving a second power limit signal for the IBR, and determining a constrained power limit signal based on the first and second power limit signals. The method also includes applying a first frequency droop function to the constrained power limit signal and determining at least one of a power reference signal or a pitch reference signal for the IBR as a function of an output of the first frequency droop function and the constrained power limit signal. Further, the method includes determining one or more control commands for the IBR based on at least one of the power reference signal or the pitch reference signal and controlling the IBR based on the control command(s) so as to support a grid frequency of the electrical grid within power available at the IBR.

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.