Abstract: A power conversion system for a wind turbine generator, comprising a machine-side converter having an AC voltage input from a generator and a DC voltage output to a DC link, wherein the machine-side converter is a modular multi-level converter comprising one or more converter legs corresponding to a respective one or more electrical phases of the generator, each of the converter legs comprising a plurality of converter cells, the system further comprising: a converter control module which provides the machine-side converter with a gate signal, and an electrical frequency estimation module configured to estimate the mean electrical frequency of the generator; wherein the gate signal has at least one mean switching frequency corresponding to at least one electrical phase of the generator; wherein the converter control module is configured to modulate the mean switching frequency of the gate signal in dependence on the mean electrical frequency of the generator.

Abstract: The present invention relates to a method for shutting down a wind power facility, said wind power facility comprising a power generator, a power converter comprising generator side and grid side converters being separated by an intermediate DC circuit, and power dissipation or power storage means being operatively connected to the intermediate DC circuit, the method comprising the steps of determining that the wind power facility needs to be shut down, and operating the generator side converter in accordance with a load time curve during shutdown of the wind power facility in order to avoid overloading of selected generator side converter components and the power dissipation or power storage means. Moreover, the present invention relates to a wind power facility for performing this method.

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 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 full-scale converter system in which both the grid-side inverter unit and the generator-side inverter unit have a series-connection of parallel inverters and form a generator-side and grid-side voltage-center-point at a voltage level between the inverters connected in series. The voltage-center-points are electrically connected by a center-line conductor. Conversion operation with a de-rated maximum active power-output is performed in response to at least one of (i) the grid-side inverter and (ii) the generator-side inverter of the first converter-string being disabled, by disabling active power production of at least one of (i) the grid-side inverter and (ii) the generator-side inverter of the second converter-string, or correspondingly reducing active power production of the second converter-string, thereby preventing a compensation current along the center-line conductor.

Abstract: A wind turbine converter system with a rectifier and an inverter and a converter controller has at least first and second converter strings. The converter system is controlled by a master-converter controller and a slave-converter controller. The master-converter controller controls the first converter string and the slave-converter controller controls the second converter string. The master-converter controller receives commands from a superordinate wind turbine controller, provides the slave-converter controller with string-control commands on the basis of the superordinate control commands, and controls the conversion operation of the first converter string on the basis of the superordinate control command. The slave-converter controller receives the string-control commands from the master-converter controller and controls the conversion operation of the second converter string on the basis of the string-control commands received.

Abstract: Techniques are described for operating a wind power facility in order to provide reactive power support to a power grid. The wind power facility may be a wind turbine or a wind power plant. An exemplary method includes increasing an amount of reactive power injected into the power grid, decreasing an amount of active power injected into the power grid by a certain amount, and dissipating and/or storing substantially the certain amount of active power.

Abstract: A method of monitoring a split wind-turbine-converter system with at least one generator-side converter and at least one grid-side converter arranged at distant locations, and a DC-link in the form of an elongated conductor arrangement with at least one positive and at least one negative conductor. The impedance of the DC-link conductor arrangement is determined by means of DC-voltage sensors. The voltages between the positive and the negative conductors are determined at the generator-side converter and at the grid-side converter, and the difference between the voltages is determined. The impedance of the DC-link conductor arrangement is determined by putting the determined voltage difference in relation to the DC current flowing through the DC-link conductor arrangement. If the impedance exceeds a given impedance threshold a fault state is recognized.

Abstract: In a full-scale converter system both the grid-side inverter unit and the generator-side inverter unit have a series convection of parallel inverters and form a generator-side and grid-side voltage-center-point at a voltage level between those of the inverters connected in series. The voltage-center-points are electrically connected by a center-line conductor that has a cross-section between 30% and 70% of that of a positive or negative potential conductor. The converter system continues conversion operation in the event of a fault in an inverter of a first converter-string, with non-faulty inverters of the converter system, as the center-line conductor is dimensioned by said cross-section to carry a compensation current resulting from an unbalanced active power-output.

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 of controlling a full-scale converter system in which both the grid-side inverter unit and the generator-side inverter unit have a series-connection of parallel inverters and form a generator-side and grid-side voltage-center-point at a voltage level between the inverters connected in series. The voltage-center-points are electrically connected by a center-line conductor. Conversion operation with a de-rated maximum active power-output is performed in response to at least one of (i) the grid-side inverter and (ii) the generator-side inverter of the first converter-string being disabled, by disabling active power production of at least one of (i) the grid-side inverter and (ii) the generator-side inverter of the second converter-string, or correspondingly reducing active power production of the second converter-string, thereby preventing a compensation current along the center-line conductor.

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: In a full-scale converter system both the grid-side inverter unit and the generator-side inverter unit have a series convection of parallel inverters and form a generator-side and grid-side voltage-center-point at a voltage level between those of the inverters connected in series. The voltage-center-points are electrically connected by a center-line conductor that has a cross-section between 30% and 70% of that of a positive or negative potential conductor. The converter system continues conversion operation in the event of a fault in an inverter of a first converter-string, with non-faulty inverters of the converter system, as the center-line conductor is dimensioned by said cross-section to carry a compensation current resulting from an unbalanced active power-output.

Abstract: A method of monitoring a split wind-turbine-converter system with at least one generator-side converter and at least one grid-side converter arranged at distant locations, and a DC-link in the form of an elongated conductor arrangement with at least one positive and at least one negative conductor. The impedance of the DC-link conductor arrangement is determined by means of DC-voltage sensors. The voltages between the positive and the negative conductors are determined at the generator-side converter and at the grid-side converter, and the difference between the voltages is determined. The impedance of the DC-link conductor arrangement is determined by putting the determined voltage difference in relation to the DC current flowing through the DC-link conductor arrangement. If the impedance exceeds a given impedance threshold a fault state is recognized.

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 wind turbine converter system with a rectifier and an inverter and a converter controller has at least first and second converter strings. The converter system is controlled by a master-converter controller and a slave-converter controller. The master-converter controller controls the first converter string and the slave-converter controller controls the second converter string. The master-converter controller receives commands from a superordinate wind turbine controller, provides the slave-converter controller with string-control commands on the basis of the superordinate control commands, and controls the conversion operation of the first converter string on the basis of the superordinate control command. The slave-converter controller receives the string-control commands from the master-converter controller and controls the conversion operation of the second converter string on the basis of the string-control commands received.

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 ing signals based on the modified random distribution to the power converters.

Abstract: The present invention relates to a method for operating a wind power facility in order to provide reactive power support to a power grid, the method comprising the step of increasing an amount of reactive power injected into the power grid, decreasing an amount of active power injected into the power grid by a certain amount, and dissipating and/or storing essentially said certain amount of active power in power dissipation and/or power storage means. The wind power facility may comprise a wind turbine or a wind power plant.

Abstract: The present invention relates to a method for shutting down a wind power facility, said wind power facility comprising a power generator, a power converter comprising generator side and grid side converters being separated by an intermediate DC circuit, and power dissipation or power storage means being operatively connected to the intermediate DC circuit, the method comprising the steps of determining that the wind power facility needs to be shut down, and operating the generator side converter in accordance with a load time curve during shutdown of the wind power facility in order to avoid overloading of selected generator side converter components and the power dissipation or power storage means. Moreover, the present invention relates to a wind power facility for performing this method.