Abstract: A generator for producing electric power, the generator including a generator unit including a stator) and a rotatably supported rotor, wherein the stator includes a first set of windings and a second set of windings, and the rotor is adapted to induce electrical voltage in the first set of windings and in the second set of windings when the rotor is rotated relative to the stator, the generator further includes a first converter coupled to the first set of windings, the first converter being adapted to convert alternating voltage in the first set of windings into an output DC voltage, a DC output coupled to the first converter to receive the output DC voltage, and a second converter coupled to the second set of windings and to the DC output, the second converter being adapted to generate control voltages and/or control currents in the second set of windings, is provided.

Abstract: A method for determining a limit value of a wind turbine reference operational variable is described The wind turbine being connected to a connection node to which a utility grid is connected. The method includes: obtaining a first input signal indicative of a connection node limit voltage; obtaining a second input signal indicative of a connection node voltage; and determining the limit value of the wind turbine reference operational variable based on the first signal and the second signal. Further a corresponding arrangement is described.

Abstract: The embodiments relate to a method for the computer-aided ascertainment of the impedance of an electrical energy network, wherein the electrical voltage, the active power, and the reactive power are measured at a connection point, by which an electrical energy production installation is connected to the energy network, at respective successive instants. In this case, the impedance value is estimated at respective present instants by a computation code that is independent of the phase of the measured voltage. The estimation is carried out only for relatively large variations in the measured voltage or reactive power. The estimate is also taken into account only if its estimate error is small. The embodiments are based on the insight that accurate estimation of the impedance is possible at particular operating points of the energy network even without knowledge of voltage phase.

Abstract: A generator for producing electric power, the generator including a generator unit including a stator) and a rotatably supported rotor, wherein the stator includes a first set of windings and a second set of windings, and the rotor is adapted to induce electrical voltage in the first set of windings and in the second set of windings when the rotor is rotated relative to the stator, the generator further includes a first converter coupled to the first set of windings, the first converter being adapted to convert alternating voltage in the first set of windings into an output DC voltage, a DC output coupled to the first converter to receive the output DC voltage, and a second converter coupled to the second set of windings and to the DC output, the second converter being adapted to generate control voltages and/or control currents in the second set of windings, is provided.

Abstract: There is provided a power generation park (100) having a power output (108) for providing electrical output power (150) to an electricity network (128). A power generation device (102a, . . . 102n) has a converter device (106) configured for receiving input power (142) from a power generator (104) and providing, in response thereto, the electrical output power (150) to the power output (112). The power generation park (100) also has a controller (122) being configured for receiving an oscillation indicating signal (126) indicative of a power oscillation in the electricity network (108), the controller (122) being further configured for providing a damping control signal (132) in response to the oscillation indicating signal (126); the converter device (106) being configured for modulating the electrical output power (150) in response to the damping control signal (132) so as to damp the power oscillation in the electricity network (128).

Abstract: A disturbance on an electric signal at an electric connection between an electric power generating system and a power grid is decomposed into a first disturbance with a first strength assigned to the electric power generating system and a second disturbance with a second strength assigned to the power grid. A voltage value of a voltage of the electric signal is measured. A current value of a current of the electric signal is measured. A value of an open circuit voltage of an equivalent voltage source is calculated based on the measured voltage value, the measured current value and a characteristic equivalent impedance of the electric power generating system so that the electric power generating system is in a harmonic model. The strength of the first disturbance is determined based on the calculated value of the open circuit voltage of the equivalent voltage source.

Abstract: A power distribution system for distributing electric power generated by a wind farm between an AC power transmission link and a DC power transmission link is provided. Both power transmission links connect the wind farm to a substation of a power grid. The power distribution system includes a central wind farm controller and a distribution device. In response to a control signal from the central wind farm controller, the distribution device distributes the generated electrical power between the two power transmission links. It is further described a power transmission system with the above described power distribution system and a method for distributing electric power between an AC power transmission link and a DC power transmission link.

Abstract: A method of operating a converter of a wind turbine for providing electric energy to a utility grid includes determining a grid voltage. If the grid voltage is between a nominal voltage and a first voltage threshold, i.e. higher than the nominal voltage, a normal procedure for lowering the grid voltage is performed. If the grid voltage is above the first voltage threshold, another procedure for keeping the wind turbine connected is performed, wherein the other procedure is different from the normal procedure. Further a corresponding arrangement is described.

Abstract: A converter device (for power conversion in e.g. a power plant such as a wind turbine is disclosed. An individual controller is provided for each phase of an electrical output power of the converter. If a voltage of one phase is indicated as being out of a predetermined voltage band, an active current of this phase is set to zero and optionally a reactive component of this phase is set to a value that depends on the indicated voltage.

Abstract: A power generation park is provided including a power output for providing electrical output power to an electricity network. A power generation device includes a converter device configured for receiving input power from a power generator and providing, in response hereto, the electrical output power to the power output. The power generation park further includes a controller configured for receiving an oscillation indicating signal indicative of a power oscillation in the electricity network, the controller further configured for providing a damping control signal in response to the oscillation indicating signal, the converter device configured for modulating the electrical output power in response to the damping control signal so as to damp the power oscillation in the electricity network.

Abstract: A method for controlling a wind turbine is provided. The method includes monitoring an electrical quantity at an output terminal of the wind turbine. The electric quantity has an amplitude and periodically varying with a grid frequency. The method further includes detecting an oscillation of the amplitude and decreasing active power output from the wind turbine at the output terminal depending on the detected oscillation.

Abstract: A converter device for power conversion in a power plant, such as a wind turbine, is provided. The converter device is configured for converting an electrical input power to an electrical output power. The converter device may be configured for receiving mechanical input power or, according to another embodiment, may be configured for receiving electrical input power. The converter device includes a voltage input for receiving a voltage signal, which is indicative of a voltage in a electricity network to which the converter device is coupled during operation in order to provide the electrical output power to the electricity network The converter device includes a controller being configured for setting a reactive component of the electrical output power depending on the voltage signal according to a out-of-band reactive current gradient if the voltage indicated by the voltage signal is outside a predetermined voltage band.

Abstract: A disturbance on an electric signal at an electric connection between an electric power generating system and a power grid is decomposed into a first disturbance with a first strength assigned to the electric power generating system and a second disturbance with a second strength assigned to the power grid. A voltage value of a voltage of the electric signal is measured. A current value of a current of the electric signal is measured. A value of an open circuit voltage of an equivalent voltage source is calculated based on the measured voltage value, the measured current value and a characteristic equivalent impedance of the electric power generating system so that the electric power generating system is in a harmonic model. The strength of the first disturbance is determined based on the calculated value of the open circuit voltage of the equivalent voltage source.

Abstract: A method for controlling a wind turbine is provided. The method includes monitoring an electrical quantity at an output terminal of the wind turbine. The electric quantity has an amplitude and periodically varying with a grid frequency. The method further includes detecting an oscillation of the amplitude and decreasing active power output from the wind turbine at the output terminal depending on the detected oscillation.

Abstract: A method of operating a converter of a wind turbine for providing electric energy to a utility grid includes determining a grid voltage. If the grid voltage is between a nominal voltage and a first voltage threshold, i.e. higher than the nominal voltage, a normal procedure for lowering the grid voltage is performed. If the grid voltage is above the first voltage threshold, another procedure for keeping the wind turbine connected is performed, wherein the other procedure is different from the normal procedure. Further a corresponding arrangement is described.

Abstract: An arrangement for generating a control signal for controlling a power output of a power generation system is described. The power output is to be supplied to a utility grid, the arrangement includes an input terminal for receiving an input signal indicative of an actual grid frequency of the utility grid; a control circuit for generating the control signal wherein the control circuit comprises a first circuit for generating a time derivative value of the input signal; and an output terminal to which the control signal is supplied, wherein the control signal depends on the generated time derivative value of the input signal. Further a power generation system is described.

Abstract: An arrangement is provided for controlling a power output of a power generation system by controlling an acceleration of a generator of a power generation system. The arrangement includes an input terminal for receiving an input signal indicative of an actual grid frequency of a utility grid, a control circuit for generating a control signal, and an output terminal to which the control signal is supplied. The control circuit is adapted for receiving the input signal, for determining whether the actual grid frequency is above a predefined threshold, and, if the input signal indicates that the actual grid frequency is above the predefined threshold, for generating the control signal based on the input signal. The control signal is indicative of an acceleration of the generator. The power output of the power generation system is controlled by controlling the acceleration of the generator. Further a power generation system is described.

Abstract: A method for determining a limit value of a wind turbine reference operational variable is described The wind turbine being connected to a connection node to which a utility grid is connected. The method includes: obtaining a first input signal indicative of a connection node limit voltage; obtaining a second input signal indicative of a connection node voltage; and determining the limit value of the wind turbine reference operational variable based on the first signal and the second signal. Further a corresponding arrangement is described.

Abstract: A wind farm capacitance determination device for receiving a wind farm layout information of a wind farm and at least one optimization constraint is provided. An optimization unit optimizes a cost by providing an optimized capacitance related parameter value set, the cost being determined by a cost function which associates to each capacitance related parameter value set a cost value, the cost function being based on the wind farm layout information and the optimization taking the at least one optimization constraint into account. In an embodiment the optimized capacitance related parameter value set includes a location, a number and a size of capacitor banks to be electrically connected to the wind farm.

Abstract: A power distribution system for distributing electric power generated by a wind farm between an AC power transmission link and a DC power transmission link is provided. Both power transmission links connect the wind farm to a substation of a power grid. The power distribution system includes a central wind farm controller and a distribution device. In response to a control signal from the central wind farm controller, the distribution device distributes the generated electrical power between the two power transmission links. It is further described a power transmission system with the above described power distribution system and a method for distributing electric power between an AC power transmission link and a DC power transmission link.