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: 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.

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: This invention concerns a method of controlling a power converter system 26 operating in an overmodulation region. The power converter system 26 comprises more than two current controllers 71, 73, 77, 79 a modulator 76 and a power converter 78, and the modulator 76 is configured to provide at least one modulated drive signal 87 to the power converter 78 based on voltage reference vector signals 82a, 82b, 82c, 82d from the more than two current controllers 71, 73, 77, 79. The method comprises determining the voltage reference vector signals 82a, 82b, 82c, 82d; determining compensated voltage reference vector signals 84a, 84b, 84c, 84d indicative of a fundamental frequency of a respective voltage reference vector signal 82a, 82b, 82c, 82d; and, determining the at least one modulated drive signal 87 based on a combination of the compensated voltage reference vector signals 84a, 84b, 84c, 84d.

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: The invention relates to a method for operating a wind turbine which comprises a power generator, a generator side converter, a grid side converter, a DC link electrically connected to an output of the generator side converter and an input of the grid side converter. The method comprises monitoring a wind turbine signal for detection of an operational condition which requires an increase of an output voltage of the grid side converter, upon detection of the operational condition, initiate an over-modulation mode wherein the grid side converter is operated with a modulation index in an over-modulation range, and upon the detection of the operational condition, initiate a DC-voltage adjustment mode wherein the a DC-voltage of the DC link is increased from a first voltage level towards a second voltage level.

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: This invention concerns a method of controlling a line side converter of a power converter system operating in an over-modulation range. The line side converter comprises a controller comprising a feedback control module configured to output a feedback control signal for modifying a drive signal received by a modulator. The method comprises determining a modulation index within the over-modulation range; and, controlling the feedback control module to adjust the feedback control signal based on the modulation index.

Abstract: This invention relates to a method of controlling at least one wind turbine of a plurality of wind turbines connected to an electrical grid at a predefined point in the electrical grid. The wind turbine comprises a DC link connecting a generator side converter to a line side converter, where the line side converter is controlled according to a modulation index requested by a power converter controller. The method comprises determining a harmonic frequency signal indicative of a harmonic frequency value at the predefined point in the electrical grid; determining a deviation between the harmonic frequency signal and a permissible harmonic frequency value; determining a permissible modulation index based on the deviation; comparing the permissible modulation index to the modulation index requested by the power converter controller; and, altering a DC link voltage set-point based on the comparison between the permissible modulation index and the requested modulation index.

Abstract: The present invention relates to a method of controlling a doubly fed induction generator wind turbine converter system in case of a sub-synchronous resonance event, the method comprising the steps of detecting the sub-synchronous resonance event, and switching from a first control mode to a second control mode in response to detecting the predetermined event, wherein the second control mode comprises the step of setting at least one rotor current controller parameter on the basis of a generator speed of the doubly fed induction generator. The predetermined event may also be a fault ride through event. The present invention further relates to a doubly fed induction generator wind turbine converter system being capable of handling such events.

Abstract: A method for use in controlling a wind turbine generator of a wind power plant based on a condition of a power converter or a component forming part of a power converter in the wind power plant. The method comprises determining the initial condition of the power converter or a component forming part of a power converter and determining the evolution of the condition from the initial condition based on notional power reference values of the wind turbine generator. The method further comprises comparing the evolution of the condition to a predetermined threshold and determining, from the comparison, a time period by which the condition of the power converter or a component forming part of a power converter will substantially equal the predetermined threshold.

Abstract: Aspects of the present invention relate to a method for controlling an amount of reactive current provided from a wind turbine generator to a power grid during an abnormal power grid event, said wind turbine generator comprising a doubly-fed induction generator having a rotor and a stator, and a power converter coupling the rotor to the power grid, the power converter comprising a grid-side inverter, wherein the method comprises the step of balancing the reactive current provided to the power grid between a reactive stator current and a reactive grid-side inverter current, wherein the reactive grid-side inverter current is controlled in accordance with a reactive current capacity of a grid breaker receiving the reactive current provided by the grid-side inverter. Aspects of the present invention also relate to a wind turbine generator being capable of performing the method.

Abstract: This invention relates to a method of controlling at least one wind turbine of a plurality of wind turbines connected to an electrical grid at a predefined point in the electrical grid. The wind turbine comprises a DC link connecting a generator side converter to a line side converter, where the line side converter is controlled according to a modulation index requested by a power converter controller. The method comprises determining a harmonic frequency signal indicative of a harmonic frequency value at the predefined point in the electrical grid; determining a deviation between the harmonic frequency signal and a permissible harmonic frequency value; determining a permissible modulation index based on the deviation; comparing the permissible modulation index to the modulation index requested by the power converter controller; and, altering a DC link voltage set-point based on the comparison between the permissible modulation index and the requested modulation index.

Abstract: This invention concerns a method of controlling a power converter system 26 operating in an overmodulation region. The power converter system 26 comprises more than two current controllers 71, 73, 77, 79 a modulator 76 and a power converter 78, and the modulator 76 is configured to provide at least one modulated drive signal 87 to the power converter 78 based on voltage reference vector signals 82a, 82b, 82c, 82d from the more than two current controllers 71, 73, 77, 79. The method comprises determining the voltage reference vector signals 82a, 82b, 82c, 82d; determining compensated voltage reference vector signals 84a, 84b, 84c, 84d indicative of a fundamental frequency of a respective voltage reference vector signal 82a, 82b, 82c, 82d; and, determining the at least one modulated drive signal 87 based on a combination of the compensated voltage reference vector signals 84a, 84b, 84c, 84d.

Abstract: A method for use in controlling a wind turbine generator based on a condition of a power converter or a component forming part of a power converter in the wind turbine generator. The method comprises determining a condition of the power converter or the component forming part of a power converter, then comparing the condition to a predetermined threshold and modifying an operational parameter of the wind turbine generator if the condition substantially equals or exceeds the predetermined threshold. In particular, the invention proposes the wind turbine generator is derated if the condition of the power converter or the component forming part of a power converter substantially equals or exceeds the predetermined threshold.

Abstract: A method of controlling a wind turbine is provided. The method comprises providing a primary power reference signal and a secondary power reference signal. The primary power reference signal is limited according to a primary signal limit. The secondary power reference signal is limited according to a secondary signal limit. The primary power reference signal and the secondary power reference signal are combined to provide a combined power reference signal, which is provided to a power or torque control system of the wind turbine.

Abstract: A method for use in controlling a wind turbine generator of a wind power plant based on a condition of a power converter or a component forming part of a power converter in the wind power plant. The method comprises determining the initial condition of the power converter or a component forming part of a power converter and determining the evolution of the condition from the initial condition based on notional power reference values of the wind turbine generator. The method further comprises comparing the evolution of the condition to a predetermined threshold and determining, from the comparison, a time period by which the condition of the power converter or a component forming part of a power converter will substantially equal the predetermined threshold.

Abstract: Aspects of the present invention relate to a method for controlling an amount of power to be delivered from a wind turbine generator to a power grid during an abnormal power grid event, the method comprising the steps of detecting an abnormal power grid event; controlling an active current delivered to the power grid in response to a measured or determined total active current; and controlling a reactive current delivered to the power grid in response to a measured or determined total reactive current. Aspects of the present invention further relate to a computer program product for carrying out the method as well as a wind turbine generator being capable of carrying out embodiments of the invention.

Abstract: The invention relates to a method for operating a wind turbine which comprises a power generator, a generator side converter, a grid side converter, a DC link electrically connected to an output of the generator side converter and an input of the grid side converter. The method comprises monitoring a wind turbine signal for detection of an operational condition which requires an increase of an output voltage of the grid side converter, upon detection of the operational condition, initiate an over-modulation mode wherein the grid side converter is operated with a modulation index in an over-modulation range, and upon the detection of the operational condition, initiate a DC-voltage adjustment mode wherein the a DC-voltage of the DC link is increased from a first voltage level towards a second voltage level.

Abstract: Controlling a power converters during over voltage condition. A wind turbine signal is monitored for detection of an over voltage of the grid and upon detection of the over voltage, an over-modulation mode is initiated wherein the grid side converter is operated with a modulation index being increased in an over-modulation range at least during a sub-period of the over-modulation mode, and upon the detection of the operational condition, a DC-voltage adjustment mode is initiated wherein the DC voltage of the DC link is decreased from a second voltage level towards a first voltage level at least during a sub-period of the DC-voltage adjustment mode.