Abstract: A method is provided for operating an electric energy production facility during a fault in a utility grid to which energy is to be delivered. The energy production facility includes at least one wind turbine. The method includes disconnecting the utility grid from the wind turbine. The method further includes connecting an external generator via a cable to an auxiliary equipment of the wind turbine, to deliver active power to the auxiliary equipment. The cable is connected to a converter of the wind turbine the converter supporting reactive power. A corresponding arrangement also provided.

Abstract: It is described a method and an arrangement for controlling a wind turbine (811) having a rotor (813) and being connected to a utility grid (831), the method comprising: increasing a rotational speed (205) of the rotor from a typical rotational speed (209, 505) to an increased rotational speed (211, 507).

Abstract: A method is provided for determining a voltage bounding range defining a range of a wind turbine reference voltage for a wind turbine for controlling an output voltage of the wind turbine at a wind turbine output terminal. The method includes obtaining information regarding an electrical characteristic of a transmission line connecting the wind turbine output terminal to a point of common coupling to which plural other wind turbines are connectable. The method further includes defining the voltage bounding range based on the electrical characteristic of the transmission line.

Abstract: It is described a method and an arrangement for controlling a wind turbine (811) having a rotor (813) and being connected to a utility grid (831), the method comprising: increasing a rotational speed (205) of the rotor from a typical rotational speed (209, 505) to an increased rotational speed (211, 507).

Abstract: A method is provided for controlling a wind farm connected to a grid. The wind farm includes a wind farm emergency generator and at least a first wind turbine. The first wind turbine includes a wind turbine transformer, a wind turbine converter and auxiliary equipment. The method includes detecting a lost grid connection, providing active power to the auxiliary equipment via the wind farm emergency generator, providing reactive power via the wind turbine converter.

Abstract: A method is provided for controlling a wind turbine connected to a node connected to a utility grid. The node also has a plurality of other wind turbines connected to it. The method includes measuring a quantity indicative of a slope of a voltage at the node in dependence of active power delivered to the node, determining that the slope is smaller than a negative slope limit, and performing a measure, in order to increase the slope above the slope limit.

Abstract: A wind park control system for controlling reactive power output of wind turbines is described. The wind park delivers active power and reactive power to a utility grid. A total amount of reactive power required by the utility grid and an individual amount of reactive power for each wind turbine are determined. A capability scheme having an order for selecting the wind turbines to deliver reactive power is calculated based on the individual amount of reactive power and the total electrical power loss contributed by each connection of the wind turbines to the utility grid. An actual amount of reactive power provided by the wind turbines is adjusted. The reactive power output of each wind turbine is controlled based on the capability scheme. The wind turbines are selected for delivering reactive power in the order of the capability scheme so that the total amount of reactive power is fulfilled.

Abstract: A method is provided for controlling a wind turbine connected to a node connected to a utility grid. The node also has a plurality of other wind turbines connected to it. The method includes measuring a quantity indicative of a slope of a voltage at the node in dependence of active power delivered to the node, determining that the slope is smaller than a negative slope limit, and performing a measure, in order to increase the slope above the slope limit.

Abstract: A method is provided for controlling a wind farm connected to a grid. The wind farm includes a wind farm emergency generator and at least a first wind turbine. The first wind turbine includes a wind turbine transformer, a wind turbine converter and auxiliary equipment. The method includes detecting a lost grid connection, providing active power to the auxiliary equipment via the wind farm emergency generator, providing reactive power via the wind turbine converter.

Abstract: A method is provided for determining a voltage bounding range defining a range of a wind turbine reference voltage for a wind turbine for controlling an output voltage of the wind turbine at a wind turbine output terminal The method includes obtaining information regarding an electrical characteristic of a transmission line connecting the wind turbine output terminal to a point of common coupling to which plural other wind turbines are connectable. The method further includes defining the voltage bounding range based on the electrical characteristic of the transmission line.

Abstract: A wind farm is described which includes a collector grid and a wind turbine being connected to the collector grid. The wind turbine includes a wind turbine transformer, and a wind turbine transformer bypass switch. Further disclosed is a method for operating a wind farm. The method includes measuring a collector grid voltage, and bypassing a wind turbine transformer if the measured collector grid voltage is below a first predetermined threshold voltage.

Abstract: A method is provided for operating an electric energy production facility during a fault in a utility grid to which energy is to be delivered. The energy production facility includes at least one wind turbine. The method includes disconnecting the utility grid from the wind turbine. The method further includes connecting an external generator via a cable to an auxiliary equipment of the wind turbine, to deliver active power to the auxiliary equipment. The cable is connected to a converter of the wind turbine the converter supporting reactive power. A corresponding arrangement also provided.

Abstract: The present invention relates to a method for controlling a voltage level of a power supply grid operationally connected to a source of electrical power, the method comprising the steps of determining a short circuit impedance of the power supply grid at a point of common coupling, calculating, using the determined short circuit impedance, a gain value of the power supply grid, and controlling the grid voltage level in accordance with the calculated gain value by applying said gain value as a gain parameter in a voltage controller. The method according to the present invention may be implemented as a method for configuring a voltage controller once and for all, or it may be implemented as a method for adaptively adjusting a gain of a voltage controller.

Abstract: The present invention relates to a method for controlling a voltage level of a power supply grid operationally connected to a source of electrical power, the method comprising the steps of determining a short circuit impedance of the power supply grid at a point of common coupling, calculating, using the determined short circuit impedance, a gain value of the power supply grid, and controlling the grid voltage level in accordance with the calculated gain value by applying said gain value as a gain parameter in a voltage controller. The method according to the present invention may be implemented as a method for configuring a voltage controller once and for all, or it may be implemented as a method for adaptively adjusting a gain of a voltage controller.