Abstract: A method for controlling a renewable energy farm comprising a plurality of wind turbines and at least one central control unit is disclosed. The wind turbines of the renewable energy farm are connected to a power grid. The central control unit receives a request for change in operation of at least one of the wind turbines, where execution of the change in operation causes a change in power output of the wind turbine. The central control unit checks whether or not the change in power output is in conflict with at least one obligation of the renewable energy farm towards the power grid. In the case that the change in power output is in conflict with at least one obligation of the renewable energy farm towards the power grid, execution of the change in operation is deferred.

Abstract: Aspects of the present invention relate to a method for controlling a plurality of renewable energy generators. The method comprises: determining preliminary reactive power set points for the generators based on a reactive power reference value; determining generator-based and voltage-based reactive power limits for the generators; generating dispatch signals for requesting reactive power from the generators based on the preliminary set point and the limits; and dispatching the dispatch signals to the generators. The generator-based reactive power limits correspond to the reactive power capability of the generator. The voltage-based limits are determined by: determining a terminal voltage of the generator; comparing the determined terminal voltage to a voltage limit; and determining the voltage-based reactive power limit based on the comparison.

Abstract: A method for damping oscillations in a power grid is provided. A damping vector (9) targeted at a position of a damping entity (11) and referencing a common reference time frame (4) is generated, based on an identified oscillation in the power grid, the damping vector (9) specifying a frequency, a phase angle and an amplitude. The damping vector (9) is provided to the damping entity (11), and the damping entity (11) reconstructs an oscillation signal corresponding to the oscillation in the power grid, based on the damping vector (9) and applying the common reference time frame (4). The damping entity (11) supplies and/or consumes active and/or reactive power to/from the power grid in accordance with the reconstructed oscillation signal, thus causing damping of the oscillation in the power grid.

Abstract: A method for controlling a power output of a grid forming wind turbine (1) in order to dampen power oscillations between a power grid (13) to which the wind turbine (1) is connected and the wind turbine (1) is disclosed. A damping power reference, PD, depending on a grid frequency of the power grid (13) and/or on a virtual rotor speed is calculated, with the purpose of dampening oscillations in the power output of the grid side converter (11). A power output of the grid side converter (11) is controlled, in accordance with a grid side power reference, Pref, and taking the damping power reference, PD, into account. A feedforward power reference for the machine side converter (10) is generated, the feedforward power reference including the damping power reference, PD, and an inertia power reference, PI, proportional to the time derivative of the grid frequency, and a power output of the machine side converter (10) is controlled at least partly based on the feedforward power reference.

Abstract: Limiting generator loads in a wind turbine having a power converter with a line side inverter configured as a grid forming inverter. A maximum grid current value is determined based on a measured generator load and a limit function. A virtual impedance value and a virtual voltage drop over the virtual impedance value are determined. A virtual synchronous machine angle is determined based on a power reference and the virtual grid power. The voltage reference for controlling the line side inverter is determined based on the virtual synchronous machine angle, the virtual voltage drop and the voltage magnitude reference.

Abstract: A method for damping power oscillation in an electric power grid, comprising: performing a procedure for determination of a phase shift between a filtered voltage signal and a filtered frequency signal; based on the performed procedure, determining which one of the filtered voltage signal and filtered frequency signal is leading or lagging in relation to the other one of the filtered voltage signal and filtered frequency signal; based on the determination of which one of the filtered voltage signal and filtered frequency signal is leading or lagging, setting a gain of a power oscillation damping controller to be positive or negative; applying the power oscillation damping controller with the set gain so as to produce an output signal outputted from the power oscillation damping controller; and based on the produced output signal, controlling an injection of electric power to the grid so as to dampen power oscillation in the grid.

Abstract: The invention relates to wind turbines, particularly to controlling reactive power exchange between a power grid and a wind power plant. The wind power plant has a plurality of wind turbine generators each having a corresponding power converter with a converter controller. Further, the wind power plant has a power plant transformer with an on load tap changer coupled between the wind power plant and the power grid. The power plant controller is regulating the on load tap changer and is generating reactive component setpoints for the wind turbine generators, when determining a need for production of short-term reactive power due to a sudden change in reactive power measured at the point of common coupling.

Abstract: Limiting generator loads in a wind turbine having a power converter with a line side inverter configured as a grid forming inverter. A maximum grid current value is determined based on a measured generator load and a limit function. A virtual impedance value and a virtual voltage drop over the virtual impedance value are determined. A virtual synchronous machine angle is determined based on a power reference and the virtual grid power. The voltage reference for controlling the line side inverter is determined based on the virtual synchronous machine angle, the virtual voltage drop and the voltage magnitude reference.

Abstract: Aspects of the present invention relate to a method for reducing high torque levels and/or high rates of change of torque in a wind turbine generator that comprises a machine-side converter and a line-side converter connected by a DC link, and, wherein the line-side converter is operated according to a virtual synchronous machine control scheme. The method comprises: determining a generator torque; determining a torque surplus indicating the amount that the generator torque exceeds a torque limit; determining an active power surplus corresponding to the torque surplus; controlling the line-side converter according to the virtual synchronous machine control scheme using an input parameter configured to reduce the active power output of the line side converter by the active power surplus.

Abstract: The invention relates to a method for controlling a power generating unit. The method includes determining a virtual impedance value, determining a virtual grid power based on the virtual resistance value and the grid current, determining a virtual synchronous machine rotational speed and/or a synchronous machine angle of a virtual synchronous generator, and determining a voltage reference for controlling a line side converter to generate the desired reactive power based on the virtual synchronous machine rotational speed or angle, a virtual voltage and the voltage magnitude reference.

Abstract: The invention relates to a method for controlling power generation of a VSM wind turbine. The wind turbine comprises a machine side converter, a line side converter, a DC link, and an electric storage device electrically connected to the DC link. The method comprises determining a first power control signal to the machine side converter, determining a second power control signal for controlling a desired output power of the line side converter based on a storage device voltage error, and a power production reference, and determining a charging current reference for controlling charging and discharging of the electric storage device based on a DC-link voltage error.

Abstract: Controlling a current injected to a power grid from a renewable power plant, in response to a voltage event in the power grid. At least a current at a point of common coupling between the renewable power plant and the power grid is determined and provided to a power plant controller (PPC). The PPC derives individual current setpoint corrections for at least some wind turbines, based on the determined current, and dispatches each derived current setpoint correction to wind turbine controllers of the corresponding wind turbines. The wind turbine controllers control a current output of the respective wind turbines, based on measurements of current and/or voltage at a point of connection between the wind turbine and an internal grid of the renewable power plant, and by taking into account the dispatched current setpoint correction.

Abstract: A method for controlling one or more renewable power generators forming a renewable power plant, and a controller configured to perform the method. In one aspect, plant voltage control is carried out on the basis of a more accurate voltage-reactive power relationship value which is determined dynamically based on grid conditions rather than the conventional approach of the voltage-reactive power relationship being a static value that is based on information provided by a transmission system operator during installation or commissioning of the power plant.

Abstract: The invention relates to a method for damping drive train oscillations of a VSM configured wind turbine. The method comprises determining a drive train damping power signal based on speed signal representing a generator speed, determining a power deviation based on a combination of a power reference for a desired power production, the drive train damping power-signal, a grid power supplied by the line side converter to the grid and a damping power, determining a virtual synchronous machine angle based on the power deviation so that the derivative of the virtual synchronous machine rotational speed is indicative of the power deviation, determining a converter reference for controlling the line side converter to generate the desired active power based on the virtual synchronous machine angle and a voltage reference for a voltage amplitude to be generated by the line side converter, and applying the converter reference to the line side converter.

Abstract: The invention relates to a method for controlling a wind turbine as virtual synchronous machine by determining the synchronous machine rotational speed rotational speed and the synchronous machine angle. The virtual synchronous machine rotational speed is determined based on a combination of a feedback of a damping power, a power reference for a desired power output of the wind turbine, a grid power supplied by the wind turbine to a power grid and a chopper power dissipated by the chopper and an inertial integration model, the synchronous machine angle is determined based on an integration of the synchronous machine rotational speed, and the damping power is determined based on the virtual synchronous machine rotational speed.

Abstract: The invention relates to wind turbines, particularly to controlling reactive power exchange between a power grid and a wind power plant. The wind power plant has a plurality of wind turbine generators each having a corresponding power converter with a converter controller. Further, the wind power plant has a power plant transformer with an on load tap changer coupled between the wind power plant and the power grid. The power plant controller is regulating the on load tap changer and is generating reactive component setpoints for the wind turbine generators, when determining a need for production of short-term reactive power due to a sudden change in reactive power measured at the point of common coupling.

Abstract: Aspects of the present invention relate to a method of voltage control for at least one wind turbine generator configured to absorb and supply reactive power on demand, the method comprises: receiving a dispatch signal from a power plant controller indicating a reactive power set point; determining a terminal voltage level of the at least one wind turbine generator; generating a reactive power correction value based on a deviation of the terminal voltage level from a voltage set point; adjusting the reactive power set point by the reactive power correction value; and controlling the at least one wind turbine generator according to the adjusted reactive power set point.

Abstract: The invention relates to a method for controlling a power generating unit. The method includes determining a virtual impedance value, determining a virtual grid power based on the virtual resistance value and the grid current, determining a virtual synchronous machine rotational speed and/or a synchronous machine angle of a virtual synchronous generator, and determining a voltage reference for controlling a line side converter to generate the desired reactive power based on the virtual synchronous machine rotational speed or angle, a virtual voltage and the voltage magnitude reference.

Abstract: Embodiments provide for the control of a power plant including several generators by setting a reference frame for the generators with a first and a second axis; measuring a grid demand voltage at the shared connection point; determining active and reactive currents required at the shared connection point based on the grid demand voltage and grid codes; transforming the active and reactive currents required at the shared connection point to the reference frame where the first axis defines a first current set point and the second axis defines a second current set point; and dispatching the first and second current set points to generator controllers associated with each generator. Current set points may be generated for positive/negative frames, direct quadrature frames, real/imaginary frames and may be set evenly for all generators or adjusted per generator.

Abstract: A grid side inverter system includes a grid side inverter, a phase locked loop controller arranged to determine a phase of a dq-frame dependent on a monitored grid voltage vector in the dq-frame and a reference grid voltage vector in the dq-frame, a current reference decision unit arranged to generate a reduction of at least one of an active and a reactive current reference, wherein a decision to generate the reduction is based on an electrical parameter relating to the phase difference of the monitored grid voltage vector and the PLL vector, a current controller arranged to determine control signals for the grid side inverter for controlling generation of active and reactive power to the grid dependent on the active and reactive current references and monitored active and a reactive grid currents in the dq-frame.