Abstract: A utility grid is provided, the utility grid including a centralized controller; an intermittent renewable energy source for generating electrical power; at least one further power generation system; and a local controller for controlling the total power output of the intermittent renewable energy source and the at least one further power generation system, wherein the centralized controller is connected with the local controller and adapted to request a desired total power output from the local controller.

Abstract: The invention relates to a method for inputting power into a multiphase alternating current grid by means of a transformer (18) which is electrically interconnected between the alternating current grid and a number of input phases (91, 92, (p3) corresponding to the number of grid phases (O1, 02, 03) of the grid, wherein at least one voltage characteristic (Ueffl, Uef˜2, Ueff3) of one of the grid phases (O1, 02, 03) is determined, and an input of reactive currents occurs as a function of a previously determined deviation (AU1, AU2, AU3) of the voltage characteristic (Ueffl, Ueff2, Ueff3) of the at least one grid phase (O1, 02, 03) relative to a corresponding target voltage characteristic (Usoll).

Abstract: The invention relates to a method for inputting power into a multiphase alternating current grid by means of a transformer which is electrically interconnected between the alternating current grid and a number of input phases corresponding to the number of grid phases of the grid, wherein at least one voltage characteristic of one of the grid phases is determined, and an input of reactive currents occurs as a function of a previously determined deviation of the voltage characteristic of the at least one grid phase relative to a corresponding target voltage characteristic. It is provided that the deviation of each one of the voltage characteristics is determined, and the input of the reactive currents in case of deviations that are asymmetrical with respect to the symmetry of the target voltage characteristics is an asymmetrical input of the reactive current with respect to the respective input at the input phases.

Abstract: The invention relates to Method of operating a wind turbine, wherein rotor windings of an induction generator, which comprises stator coils coupled to a voltage grid, fed with rotor currents by a feed-in unit are driven by a rotor of the wind turbine; wherein the frequencies of the fed-in rotor currents are controlled depending on the rotor rotation frequency and the feed-in unit is electrically decoupled from the rotor windings in the case predetermined variations of the grid voltage amplitude and the rotor current feed-in is resumed after the decoupling caused by the variation of the grid voltage amplitude, when the currents generated in the rotor windings by the variation have declined to a predetermined value.

Abstract: A utility grid is provided, the utility grid comprising a centralized control means, an intermittent renewable energy source for generating electrical power: at least one further power generation system; and at least one local controller for controlling the total power output of said intermittent renewable energy source and said as least one further power generation system, wherein the centralized control means is connected with the at least one local controller and adapted to request a desired total power output from the local controller.

Abstract: The invention relates to Method of operating a wind turbine, wherein rotor windings of an induction generator, which comprises stator coils coupled to a voltage grid, fed with rotor currents by a feed-in unit are driven by a rotor of the wind turbine; wherein the frequencies of the fed-in rotor currents are controlled depending on the rotor rotation frequency and the feed-in unit is electrically decoupled from the rotor windings in the case predetermined variations of the grid voltage amplitude and the rotor current feed-in is resumed after the decoupling caused by the variation of the grid voltage amplitude, when the currents generated in the rotor windings by the variation have declined to a predetermined value.

Abstract: A method of operating a wind turbine, wherein the wind turbine may include rotor windings of an induction generator, which includes stator coils coupled to a voltage grid, fed with rotor currents by a feed-in unit are driven by a rotor of the wind turbine; wherein the frequencies of the fed-in rotor currents are controlled depending on the rotor rotation frequency and the feed-in unit is electrically decoupled from the rotor windings in the case predetermined variations of the grid voltage amplitude and the rotor current feed-in is resumed after the decoupling caused by the variation of the grid voltage amplitude, when the currents generated in the motor windings by the variation have declined to a predetermined value.

Abstract: The invention relates to Method of operating a wind turbine, wherein rotor windings of an induction generator, which comprises stator coils coupled to a voltage grid, fed with rotor currents by a feed-in unit are driven by a rotor of the wind turbine; wherein the frequencies of the fed-in rotor currents are controlled depending on the rotor rotation frequency and the feed-in unit is electrically decoupled from the rotor windings in the case predetermined variations of the grid voltage amplitude and the rotor current feed-in is resumed after the decoupling caused by the variation of the grid voltage amplitude, when the currents generated in the rotor windings by the variation have declined to a predetermined value.