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: A method of controlling a wind turbine generator (1) comprising an electrical generator (10) and a power converter (12), the power converter (12) comprising an electrical switch (14a, 14b) that is configured to process electrical power produced by the electrical generator (10), the method comprising: controlling an output from the electrical switch (14a, 14b) using a variable pulse-width modulated control signal, thereby to control characteristics of output power from the power converter (12); acquiring sample data (26) relating to an electronic signal within the wind turbine generator (1), wherein the sample data (26) is used for controlling the wind turbine generator (1); and dynamically adjusting a frequency (30) at which the sample data is acquired to synchronise data acquisition with a carrier frequency (24) of the control signal.

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 is provided of controlling a doubly fed induction generator—(DFIG) wind turbine converter system if a sub-synchronous resonance event acts on the wind turbine. According to the method a sub-synchronous resonance event is detected. Thereupon, a switch from a non-SSR-control mode to a SSR-control mode is performed. At least one of the following activities is performed in the SSR-control mode, namely: (i) freezing rotor AC voltages in magnitude and phase, (ii) altering at least one rotor-current-controller gain (iii) altering at least one rotor-current-controller time constant, to dampen the effect of the SSR-event on the wind turbine.

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 power generation system, wind turbine, and method of pulse width modulation (PWM) for power converters are disclosed. The method generally includes generating a substantially random distribution of timing values, applying a filter to the random distribution to produce a modified random distribution, and delivering PWM timing signals based on the modified random distribution to the power converters.

Abstract: A method, converter arrangement, and controller are disclosed for connecting an output of a converter with an electrical grid to control inrush currents into a grid filter assembly connected with the output of the converter, the electrical grid carrying an alternating current (AC) signal having one or more phases. The method includes determining a voltage of the AC signal and operating, after pre-charging a direct current (DC) link of the converter to a predetermined voltage, the converter using open-loop voltage control to produce an AC output signal that substantially matches the AC signal of the electrical grid. The open-loop voltage control is based on the determined voltage of the AC signal. The method further includes closing, after a predetermined amount of time of operating the converter using the open-loop voltage control, a switching device to thereby connect the output of the converter with the electrical grid.

Abstract: A method is provided of protecting a wind turbine with a doubly-fed induction generator (DFIG) against a sub-synchronous resonance (SSR) event acting on the wind turbine. A plurality of power-output values or current-output values is measured over a given period of time that corresponds to a measurement cycle. It is determined whether power-output values or current-output-values measured in the at-least-one measurement cycle are indicative of an SSR-event critical for further operation of the wind turbine. The wind turbine is shut down if the measured power-output values or current-output values are indeed indicative of an SSR-event critical for operation of the wind turbine.

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.

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 generator (1) comprising an electrical generator (10) and a power converter (12), the power converter (12) comprising an electrical switch (14a, 14b) that is configured to process electrical power produced by the electrical generator (10), the method comprising: controlling an output from the electrical switch (14a, 14b) using a variable pulse-width modulated control signal, thereby to control characteristics of output power from the power converter (12); acquiring sample data (26) relating to an electronic signal within the wind turbine generator (1), wherein the sample data (26) is used for controlling the wind turbine generator (1); and dynamically adjusting a frequency (30) at which the sample data is acquired to synchronise data acquisition with a carrier frequency (24) of the control signal.

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 present invention relates to a method for operating a doubly fed induction generator wind power facility during an OVRT event, said the wind turbine facility being adapted to inject active and/or reactive current into an associated grid, the method comprising the steps of determining the occurrence of an over voltage grid event, and maintaining a grid-side inverter of the doubly fed induction generator wind power facility fully operable during the over voltage ride though event so as to maintain a controllable active and/or reactive current capability during the over voltage grid event.

Abstract: A method for controlling a wind turbine system including an electrical generator, a power converter system, a DC-link, and at least a grid-side breaker arrangement controllable between open and closed states, wherein the method comprises monitoring for the presence of a shutdown event and, in response to identifying the presence of a shutdown event, controlling the wind turbine into a production-ready state, comprising: i) controlling the grid-side breaker arrangement in the closed state; ii) disabling one or more drive signals to the power converter system; and iii) controlling the DC-link of the power converter system in a charged state. Advantageously, this approach reduces the frequency of use of the grid-side breaker arrangement which extends serviceable life considerably, and also allows the wind turbine system to be transitioned rapidly between an operating state and a production-ready state.

Abstract: A method of setting a reference DC-link voltage of a wind-turbine converter system is provided. At least at least one DC voltage demand from at least one generator-side inverter and at least one DC voltage demand are received from at least one grid-side inverter. A generator-side DC voltage demand value on the basis of the at least one DC voltage demand received from the at least one generator-side inverter. Also a grid-side DC voltage demand value is determined on the basis of the at least one DC voltage demand received from the at least one grid-side inverter. The highest DC voltage demand value out of the generator-side and grid-side DC voltage demand values is chosen. This chosen value corresponds to the set reference DC-link voltage.

Abstract: A method is provided of protecting a wind turbine with a doubly-fed induction generator (DFIG) against a sub-synchronous resonance (SSR) event acting on the wind turbine. A plurality of power-output values or current-output values is measured over a given period of time that corresponds to a measurement cycle. It is determined whether power-output values or current-output-values measured in the at-least-one measurement cycle are indicative of an SSR-event critical for further operation of the wind turbine. The wind turbine is shut down if the measured power-output values or current-output values are indeed indicative of an SSR-event critical for operation of the wind turbine.

Abstract: A method is provided of controlling a doubly fed induction generator—(DFIG) wind turbine converter system if a sub-synchronous resonance event acts on the wind turbine. According to the method a sub-synchronous resonance event is detected. Thereupon, a switch from a non-SSR-current/voltage control mode to a SSR-control mode is performed. At least one of the following activities is performed in the SSR-control mode, namely: (i) freezing rotor AC voltages in magnitude and phase, (ii) altering at least one rotor-current-controller gain (iii) altering at least one rotor-current-controller time constant, to dampen the effect of the SSR-event on the wind turbine.

Abstract: A method, converter arrangement, and controller are disclosed for connecting an output of a converter with an electrical grid to control inrush currents into a grid filter assembly connected with the output of the converter, the electrical grid carrying an alternating current (AC) signal having one or more phases. The method includes determining a voltage of the AC signal and operating, after pre-charging a direct current (DC) link of the converter to a predetermined voltage, the converter using open-loop voltage control to produce an AC output signal that substantially matches the AC signal of the electrical grid. The open-loop voltage control is based on the determined voltage of the AC signal. The method further includes closing, after a predetermined amount of time of operating the converter using the open-loop voltage control, a switching device to thereby connect the output of the converter with the electrical grid.

Abstract: The present invention relates to a method for operating a doubly fed induction generator wind power facility during an OVRT event, said the wind turbine facility being adapted to inject active and/or reactive current into an associated grid, the method comprising the steps of determining the occurrence of an over voltage grid event, and maintaining a grid-side inverter of the doubly fed induction generator wind power facility fully operable during the over voltage ride though event so as to maintain a controllable active and/or reactive current capability during the over voltage grid event,?

Abstract: A method of setting a reference DC-link voltage of a wind-turbine converter system is provided. At least at least one DC voltage demand from at least one generator-side inverter and at least one DC voltage demand are received from at least one grid-side inverter. A generator-side DC voltage demand value on the basis of the at least one DC voltage demand received from the at least one generator-side inverter. Also a grid-side DC voltage demand value is determined on the basis of the at least one DC voltage demand received from the at least one grid-side inverter. The highest DC voltage demand value out of the generator-side and grid-side DC voltage demand values is chosen. This chosen value corresponds to the set reference DC-link voltage.