Abstract: A method of operating a wind turbine during disconnection from a utility grid includes a generator, a wind turbine converter, in particular including a grid side converter portion connectable to the utility grid, a DC link, a generator side converter portion, and a UPS, the method including: allowing the UPS to draw, according to an UPS active power reference, active power from the wind turbine converter (104); controlling the wind turbine converter by a converter power reference to meet the UPS active power reference. Controlling the wind turbine converter by the converter power reference includes modulating a frequency of the converter terminal voltage in dependence of the converter power operating point, in particular the converter power reference.

Abstract: A system for supplying electric power to a grid and for supporting the grid is provided. The system includes (a) a power generator including a main converter, (b) an energy buffer including an energy storage and a secondary converter, (c) a grid stability monitor-configured to provide a grid stability, and (d) a controller configured to control the main converter and the secondary converter in dependency on the grid stability indication such that when the stability level is at least equal to a predetermined threshold value, the main converter is controlled to operate as a virtual synchronous machine and the secondary converter is controlled to operate to maintain a predetermined amount of energy in the energy storage, and when the stability level is below the predetermined threshold value, the secondary converter is operated to provide a predetermined response in order to support the grid stability.

Abstract: Provided is a method of controlling an energy storage device arranged to provide frequency support for an AC power system, the method including: setting an amount of energy stored in the energy storage device depending on a power system frequency of the AC power in the AC power system.

Abstract: Provided is a method of controlling at least one converter of at least one wind turbine connectable to a wind park grid of a wind park during black start or island mode of the wind park, the method including: ramping up a converter voltage reference unless a power related condition and/or a wind park grid frequency related condition or a converter current related condition is violated.

Abstract: A converter network bridge controller for a power converter hardware being connectable to an alternating current electricity network is provided. The controller includes an output unit configured for generating a quadrature voltage component reference to a PWM modulator which determines the switching of the power converter hardware, wherein the quadrature voltage component reference includes a first signal and a second signal. The output unit includes a first part and a second part. The first part is configured for generating the first signal based on a current reference for an active current to be generated by the power converter hardware. The second part is configured for providing the second signal to reduce a difference between a converter active current component of measured feedback current and the current reference for active current.

Abstract: A system for supplying electric power to a grid and for supporting the grid is provided. The system includes (a) a power generator including a main converter, (b) an energy buffer including an energy storage and a secondary converter, (c) a grid stability monitor-configured to provide a grid stability, and (d) a controller configured to control the main converter and the secondary converter in dependency on the grid stability indication such that when the stability level is at least equal to a predetermined threshold value, the main converter is controlled to operate as a virtual synchronous machine and the secondary converter is controlled to operate to maintain a predetermined amount of energy in the energy storage, and when the stability level is below the predetermined threshold value, the secondary converter is operated to provide a predetermined response in order to support the grid stability.

Abstract: Provided is a method of controlling a wind turbine or a wind park including at least one wind turbine connected to a utility grid for utility grid support, the method including: receiving a control command from a utility grid manager, and selectively controlling the wind turbine according to the control command.

Abstract: Provided is a method of controlling a converter, in particular of a wind turbine, the converter including a first converter portion connected to a generator, a DC-link, and a second converter portion connected to a utility grid. The method including: controlling the first converter portion and the second converter portion by a first control signal and a second control signal, respectively, both being derived based on a requested power signal, in particular requested active power signal, and a generator rotational speed, wherein the first control signal indicates substantially constant generator torque for rotational speed variations of the generator rotational speed above a frequency threshold.

Abstract: Provided is a method for starting a wind park including plural wind turbines connectable in a collector system connectable to a utility grid, the method including: starting at least one first wind turbine, each being equipped with an utility grid independent energy supply and a grid forming function, to produce electrical energy from wind energy, thereby utilizing the respective grid independent energy supply for starting; performing the grid forming function by the first wind turbine to achieve a reference voltage in the collector system; starting at least one second wind turbine and/or at least one third wind turbine to produce energy by conversion of wind energy, thereby utilizing energy provided in the collector system for starting.

Abstract: A converter network bridge controller for a power converter hardware being connectable to an alternating current electricity network is provided. The controller includes an output unit configured for generating a quadrature voltage component reference to a PWM modulator which determines the switching of the power converter hardware, wherein the quadrature voltage component reference includes a first signal and a second signal. The output unit includes a first part and a second part. The first part configured for generating the first signal based on a current reference for an active current to be generated by the power converter hardware. The second part is configured for providing the second signal to reduce a difference between a converter active current component of measured feedback current and the current reference for active current.

Abstract: Provided is a method for starting a wind park including plural wind turbines connectable in a collector system connectable to a utility grid, the method including: starting at least one first wind turbine, each being equipped with an utility grid independent energy supply and a grid forming function, to produce electrical energy from wind energy, thereby utilizing the respective grid independent energy supply for starting; performing the grid forming function by the first wind turbine to achieve a reference voltage in the collector system; starting at least one second wind turbine and/or at least one third wind turbine to produce energy by conversion of wind energy, thereby utilizing energy provided in the collector system for starting.

Abstract: A method for controlling the operation of a wind turbine which includes a mechanical drive train, an electric generator being mechanically connected to the drive train, and a power converter being electrically connected to the generator is provided. The method comprises (a) determining a frequency of an AC output voltage signal provided by the power converter; (b) recognizing, whether there has been a modification of the determined frequency with respect to a previously determined frequency, which modification is larger than a given threshold; (c) if the modification of the determined frequency is larger than the given threshold, changing a power reference signal for the wind turbine; (d) providing the changed power reference signal to a controller of the wind turbine; and (e) controlling the operation of the wind turbine on the basis of the changed power reference signal.

Abstract: A method for controlling the operation of a wind turbine is provided. The method includes (a) receiving an active power reference signal) and an active power feedback signal; (b) determining, based on the active power reference signal and the active power feedback signal, a first voltage control signal and a power controller frequency signal; (c) determining, based on the power controller frequency signal, a second voltage control signal; (d) determining, based on the frequency reference signal, a frequency controller frequency signal; (e) determining, based on the power controller frequency signal and the frequency controller frequency signal, an actual angle signal being indicative for an actual angle of a rotating dq reference frame; and (f) controlling the operation of a power converter of the wind turbine based on the first voltage control signal, the second voltage control signal, and the actual angle signal.

Abstract: A self-commutated converter is connected to further self-commutated converters by its AC voltage connection via an inductive component using a coupling point, which is common to all the converters, in an AC voltage network. An active power P and a frequency fN are determined from a network voltage at the coupling point and a converter current flowing via the inductive component. An active power difference value ?P is supplied to an orthogonal controller and to a parallel controller. The output value from the parallel controller is used to minimize the reactive power exchanged between converter and coupling point. The frequency difference value ?f is supplied to a frequency controller and the output value from the frequency controller is logically combined with the output value from the orthogonal controller and the output value from the parallel controller, the frequency difference value ?f being simultaneously minimized.

Abstract: A method is provided for controlling the operation of a wind turbine includes (a) receiving an active power reference signal; (b) determining, based on the active power reference signal and an active power feedback signal, a first voltage control signal and a power controller frequency signal; (c) receiving a power reference signal; (d) determining, based on the power reference signal and the power feedback signal, a power offset frequency signal; (e) determining, based on the power controller frequency signal, a second voltage control signal; (f) determining, based on the power offset frequency signal, an angle signal indicative for an actual angle of a rotating dq reference frame; and (g) controlling the operation of a power converter based on the first voltage control signal, the second voltage control signal, and the angle signal.

Abstract: A method for controlling the operation of a wind turbine is provided. The method includes receiving, by means of a power controller, an active power reference signal and an active power feedback signal; determining, by means of the power controller and based on the active power reference signal and the active power feedback signal, a first voltage control signal and a power controller frequency signal; determining, by means of a frequency droop gain unit and based on the power controller frequency signal, a second voltage control signal; determining, by means of a theta integrator unit and based on the power controller frequency signal, an actual angle signal being indicative for an actual angle between a rotating dq reference frame and a stationary abc reference frame; and controlling operation of a network bridge based on the first voltage control signal, the second voltage control signal, and the actual angle signal.

Abstract: A power supply arrangement adapted to provide auxiliary power to a wind farm that feeds into a HVDC transmission link is provided. The power supply arrangement has an auxiliary power supply to deliver auxiliary power (Paux) to the wind farm; a backfeed control for initiating provision of a backfeed voltage on the HVDC link during a wind farm downtime; a backfeed switch to close a DC current path between the HVDC link and the auxiliary power supply; and a power converter for converting the backfeed voltage into auxiliary power (Paux). A wind farm arranged to feed into a HVDC transmission link is also provided, having such a power supply arrangement for providing auxiliary power (Paux) to the wind farm during a wind farm downtime. A method of providing auxiliary power (Pbackfeed) to a wind farm during a wind farm downtime is also provided.

Abstract: A method is provided for controlling the operation of a wind turbine includes (a) receiving an active power reference signal; (b) determining, based on the active power reference signal and an active power feedback signal, a first voltage control signal and a power controller frequency signal; (c) receiving a power reference signal; (d) determining, based on the power reference signal and the power feedback signal, a power offset frequency signal; (e) determining, based on the power controller frequency signal, a second voltage control signal; (f) determining, based on the power offset frequency signal, an angle signal indicative for an actual angle of a rotating dq reference frame; and (g) controlling the operation of a power converter based on the first voltage control signal, the second voltage control signal, and the angle signal.

Abstract: A method for controlling the operation of a wind turbine is provided. The method includes (a) receiving an active power reference signal) and an active power feedback signal; (b) determining, based on the active power reference signal and the active power feedback signal, a first voltage control signal and a power controller frequency signal; (c) determining, based on the power controller frequency signal, a second voltage control signal; (d) determining, based on the frequency reference signal, a frequency controller frequency signal; (e) determining, based on the power controller frequency signal and the frequency controller frequency signal, an actual angle signal being indicative for an actual angle of a rotating dq reference frame; and (f) controlling the operation of a power converter of the wind turbine based on the first voltage control signal, the second voltage control signal, and the actual angle signal.

Abstract: A method for controlling the operation of a wind turbine is provided. The method includes receiving, by means of a power controller, an active power reference signal and an active power feedback signal; determining, by means of the power controller and based on the active power reference signal and the active power feedback signal, a first voltage control signal and a power controller frequency signal; determining, by means of a frequency droop gain unit and based on the power controller frequency signal, a second voltage control signal; determining, by means of a theta integrator unit and based on the power controller frequency signal, an actual angle signal being indicative for an actual angle between a rotating dq reference frame and a stationary abc reference frame; and controlling operation of a network bridge based on the first voltage control signal, the second voltage control signal, and the actual angle signal.