Patent ID: 12228109

Single features depicted in the figures are shown relatively with regards to each other and therefore are not necessarily to scale. Similar or same elements in the figures, even if displayed in different embodiments, are represented with the same reference numbers.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, which shall not limit the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention, for instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG.1is a perspective view of a portion of an exemplary wind turbine100. In the exemplary embodiment, the wind turbine100is a horizontal-axis wind turbine. Alternatively, the wind turbine100may be a vertical-axis wind turbine. Wind turbine100includes a nacelle102housing a generator (not shown inFIG.1). Nacelle102is mounted on a tower104(a portion of tower104being shown inFIG.1). Tower104may have any suitable height that facilitates operation of wind turbine100as described herein. Wind turbine100also includes a rotor106that includes three blades108attached to a rotating hub110. Alternatively, wind turbine100includes any number of blades108that facilitates operation of wind turbine100as described herein. In the exemplary embodiment, wind turbine100includes a gearbox (not shown inFIG.1) operatively coupled to rotor106and a generator (not shown inFIG.1).

The rotor blades108are spaced about the hub110to facilitate rotating the rotor106to enable kinetic energy to be transferred from the wind into usable mechanical energy, and subsequently, electrical energy.

In one embodiment, the rotor blades108have a length ranging from about 15 meters (m) to about 91 m. Alternatively, rotor blades108may have any suitable length that enables the wind turbine100to function as described herein. For example, other non-limiting examples of blade lengths include 20 m or less, 37 m, 48.7 m, 50.2 m, 52.2 m or a length that is greater than 91 m. As wind strikes the rotor blades100from a wind direction28, the rotor106is rotated about an axis of rotation30. As the rotor blades108are rotated and subjected to centrifugal forces, the rotor blades108are also subjected to various forces and moments. As such, the rotor blades108may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position.

Moreover, a pitch angle of the rotor blades100, i.e., an angle that determines a perspective of the rotor blades100with respect to the wind direction, may be changed by a pitch system109to control the load and power generated by the wind turbine100by adjusting an angular position of at least one rotor blade108relative to wind vectors. During operation of the wind turbine100, the pitch system109may change a pitch angle of the rotor blades109such that the rotor blades109are moved to a feathered position, such that the perspective of at least one rotor blade100relative to wind vectors provides a minimal surface area of the rotor blade100to be oriented towards the wind vectors, which facilitates reducing a rotational speed and/or facilitates a stall of the rotor18.

A blade pitch of each rotor blade108may be controlled individually by a wind turbine controller202or by a pitch control system. Alternatively, the blade pitch for all rotor blades108may be controlled simultaneously by said control systems.

Further, in the exemplary embodiment, as the wind direction28changes, a yaw direction of the nacelle102may be rotated, by a yaw system105, about a yaw axis38to position the rotor106with respect to wind direction28.

The yaw system105may include a yaw drive mechanism provided by nacelle102.

Further, yaw system105may also be controlled by wind turbine controller107.

For positioning nacelle102appropriately with respect to the wind direction28, the nacelle102may also include at least one meteorological mast107that may include a wind vane and anemometer (neither shown inFIG.2). The mast107may provide information to the wind turbine controller202regarding ambient conditions. This may include wind direction and/or wind speed as well as ambient temperature, ambient moisture, precipitation type and/or amount (if any).

In the exemplary embodiment, the wind turbine controller102is shown as being centralized within the nacelle102, however, the wind turbine controller may also be a distributed system throughout the wind turbine100, on a support system (not shown inFIG.1), within a wind farm, and/or at a remote control center. The wind turbine controller102includes a processor configured to perform the methods and/or steps described herein.

Referring now toFIG.2, a schematic view of one embodiment of an electrical (power) and control system200that may be used with the wind turbine100is illustrated. During operation, wind impacts the blades108and the blades108transform wind energy into a mechanical rotational torque that rotatably drives a low-speed shaft112via the hub110.

In the exemplary embodiment, the low-speed shaft112is configured to drive a gearbox114that subsequently steps up the low rotational speed of the low-speed shaft112to drive a high-speed shaft116at an increased rotational speed. The high-speed shaft116is generally rotatably coupled to a generator118so as to rotatably drive a generator rotor122having field winding (not shown).

More specifically, in one embodiment, the generator118may be a wound rotor, three-phase, doubly-fed induction (asynchronous) generator (DFIG) that includes a generator stator120magnetically coupled to a generator rotor122. As such, a rotating magnetic field may be induced by the generator rotor122and a voltage may be induced within a generator stator120that is magnetically coupled to the generator rotor122. In such embodiments, the generator118is configured to convert the rotational mechanical energy to a sinusoidal, three-phase alternating current (AC) electrical energy signal in the generator stator120. The associated electrical power can be transmitted to a main transformer234via a stator bus208, a stator synchronizing switch206, a system bus216, a main transformer circuit breaker214, and a generator-side bus236. The main transformer234steps up the voltage amplitude of the electrical power such that the transformed electrical power may be further transmitted to a grid via a grid circuit breaker238, a breaker-side bus240, and a grid bus242.

In addition, the electrical power and control system200may include a wind turbine controller202configured to control any of the components of the wind turbine100and/or implement any of the method steps as described herein. For example, as shown particularly inFIG.3, the controller202may include one or more processor(s)204and associated memory device(s)207configured to perform a variety of computer-implemented functions (e.g., performing the methods, steps, calculations and the like and storing relevant data as disclosed herein). Additionally, the controller202may also include a communications module to facilitate communications between the controller202and the various components of the wind turbine100, e.g. any of the components ofFIG.2.

Further, as shown inFIG.3, the communications module209may include a sensor interface211(e.g., one or more analog-to-digital converters) to permit signals transmitted from one or more sensors to be converted into signals that can be understood and processed by the processors204. It should be appreciated that the sensors (e.g. sensors252,254,256,257,258) may be communicatively coupled to the communications module209using any suitable means. For example, as shown inFIG.3, the sensors252,254,256,257,258may be coupled to the sensor interface211via a wired connection. However, in other embodiments, the sensors252,254,256,257,258may be coupled to the sensor interface211via a wireless connection, such as by using any suitable wireless communications protocol known in the art. As such, the processor204may be configured to receive one or more signals from the sensors.

The sensors252,254,256may be sensor for currents and/or voltages desired for controlling the power conversion of wind turbine100. This is explained in more detail below.

Further, at least one sensor258may be provided for sensor data referring to meteorological data, e.g. sensor(s) provided by the meteorological mast107shown inFIG.1. In particular an ambient air temperature sensor258may be provided by the meteorological mast107.

Furthermore, at least one temperature sensor257may be provided for measuring temperatures within the nacelle, in particular a respective sensor for measuring a temperature of the power conversion system as explained above with regard toFIG.2and components thereof, respectively, and/or for measuring a temperature of the internal air flow and the cooling circuits explained in more detail below with regard toFIGS.4A,4B.

As used herein, the term “processor” refers not only to integrated circuits referred to in the art as being included in a computer, but also refers to a controller, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits. The processor204is also configured to compute advanced control algorithms and communicate to a variety of Ethernet or serial-based protocols (Modbus, OPC, CAN, etc.). Additionally, the memory device(s)207may generally comprise memory element(s) including, but not limited to, computer readable medium (e.g., random access memory (RAM)), computer readable non-volatile medium (e.g., a flash memory), a floppy disk, a compact disc-read only memory (CD-ROM), a magnetooptical disk (MOD), a digital versatile disc (DVD) and/or other suitable memory elements. Such memory device(s)207may generally be configured to store suitable computer-readable instructions that, when implemented by the processor(s)204, configure the controller202to perform the various functions as described herein.

Referring back toFIG.2, the generator stator120may be electrically coupled to a stator synchronizing switch206via a stator bus208. In an exemplary embodiment, to facilitate the DFIG configuration, generator rotor122is electrically coupled to a bi-directional power conversion assembly210via a rotor bus212. Alternatively, generator rotor122is electrically coupled to rotor bus212via any other device that facilitates operation of electrical and control system200as described herein. As a further alternative, electrical and control system200is configured as a full power conversion system (not shown) that includes a full power conversion assembly (not shown inFIG.2) similar in design and operation to power conversion assembly210and electrically coupled to generator stator120. The full power conversion assembly facilitates channeling electric power between generator stator120and an electric power transmission and distribution grid (not shown). In the exemplary embodiment, stator bus208transmits three-phase power from generator stator120to stator synchronizing switch206. Rotor bus212transmits three-phase power from generator rotor122to power conversion assembly210. In the exemplary embodiment, stator synchronizing switch206is electrically coupled to a main transformer circuit breaker214via a system bus216. In an alternative embodiment, one or more fuses (not shown) are used instead of main transformer circuit breaker214. In another embodiment, neither fuses nor main transformer circuit breaker214is used.

Power conversion assembly210includes a rotor filter218that is electrically coupled to generator rotor122via rotor bus212. A rotor filter bus219electrically couples rotor filter218to a rotor-side power converter220, and rotor-side power converter220is electrically coupled to a line-side power converter222. Rotor-side power converter220and line-side power converter222are power converter bridges including power semiconductors (not shown). In the exemplary embodiment, rotor-side power converter220and line-side power converter222are configured in a three-phase, pulse width modulation (PWM) configuration including insulated gate bipolar transistor (IGBT) switching devices (not shown inFIG.2) that operate as known in the art. Alternatively, rotor-side power converter220and line-side power converter222have any configuration using any switching devices that facilitate operation of electrical and control system200as described herein. Power conversion assembly210is coupled in electronic data communication with turbine controller202to control the operation of rotor-side power converter220and line-side power converter222.

In the exemplary embodiment, a line-side power converter bus223electrically couples line-side power converter222to a line filter224. Also, a line bus225electrically couples line filter224to a line contactor226. Moreover, line contactor226is electrically coupled to a conversion circuit breaker228via a conversion circuit breaker bus230. In addition, conversion circuit breaker228is electrically coupled to main transformer circuit breaker214via system bus216and a connection bus232. Alternatively, line filter224is electrically coupled to system bus216directly via connection bus232and includes any suitable protection scheme (not shown) configured to account for removal of line contactor226and conversion circuit breaker228from electrical and control system200. Main transformer circuit breaker214is electrically coupled to an electric power main transformer234via a generator-side bus236. Main transformer234is electrically coupled to a grid circuit breaker238via a breaker-side bus240. Grid circuit breaker238is connected to the electric power transmission and distribution grid via a grid bus242. In an alternative embodiment, main transformer234is electrically coupled to one or more fuses (not shown), rather than to grid circuit breaker238, via breaker-side bus240. In another embodiment, neither fuses nor grid circuit breaker238is used, but rather main transformer234is coupled to the electric power transmission and distribution grid via breaker-side bus240and grid bus242.

In the exemplary embodiment, rotor-side power converter220is coupled in electrical communication with line-side power converter222via a single direct current (DC) link244. Alternatively, rotor-side power converter220and line-side power converter222are electrically coupled via individual and separate DC links (not shown inFIG.2). DC link244includes a positive rail246, a negative rail248, and at least one capacitor250coupled between positive rail246and negative rail248. Alternatively, capacitor250includes one or more capacitors configured in series and/or in parallel between positive rail246and negative rail248.

Turbine controller202is configured to receive a plurality of voltage and electric current measurement signals from a first set of voltage and electric current sensors252. Moreover, turbine controller202is configured to monitor and control at least some of the operational variables (also referred to as operating parameter herein) associated with wind turbine100. In the exemplary embodiment, each of three voltage and electric current sensors252are electrically coupled to each one of the three phases of grid bus242. Accordingly, a current frequency of the grid may be determined by controller202. Alternatively or in addition, turbine controller202may be functionally coupled with a frequency sensor connectable with the grid. Further, it is possible that controller202receives the current frequency of the grid or at least a signal representative for the current frequency of the grid via primary plant controller such as a wind farm controller functionally coupled with a respective sensor.

As shown inFIG.2, electrical and control system200also includes a converter controller262that is configured to receive a plurality of voltage and electric current measurement signals. For example, in one embodiment, converter controller262receives voltage and electric current measurement signals from a second set of voltage and electric current sensors254coupled in electronic data communication with stator bus208. Converter controller262receives a third set of voltage and electric current measurement signals from a third set of voltage and electric current sensors256coupled in electronic data communication with rotor bus212. Converter controller262also receives a fourth set of voltage and electric current measurement signals from a fourth set of voltage and electric current sensors264coupled in electronic data communication with conversion circuit breaker bus230. Second set of voltage and electric current sensors254is substantially similar to first set of voltage and electric current sensors252, and fourth set of voltage and electric current sensors264is substantially similar to third set of voltage and electric current sensors256. Converter controller262is substantially similar to turbine controller202and is coupled in electronic data communication with turbine controller202. Moreover, in the exemplary embodiment, converter controller262is physically integrated within power conversion assembly210. Alternatively, converter controller262has any configuration that facilitates operation of electrical and control system200as described herein.

During operation, wind impacts blades108and blades108transform wind energy into a mechanical rotational torque that rotatably drives low-speed shaft112via hub110. Low-speed shaft112drives gearbox114that subsequently steps up the low rotational speed of low-speed shaft112to drive high-speed shaft116at an increased rotational speed. High speed shaft116rotatably drives generator rotor122. A rotating magnetic field is induced by generator rotor122and a voltage is induced within generator stator120that is magnetically coupled to generator rotor122. Generator118converts the rotational mechanical energy to a sinusoidal, three-phase alternating current (AC) electrical energy signal in generator stator120. In the exemplary embodiment, the associated electrical power is transmitted to main transformer234via stator bus208, stator synchronizing switch206, system bus216, main transformer circuit breaker214and generator-side bus236. Main transformer234steps up the voltage amplitude of the electrical power and the transformed electrical power is further transmitted to a grid via breaker-side bus240, grid circuit breaker238and grid bus242.

In the exemplary embodiment, a second electrical power transmission path is provided. Electrical, three-phase, sinusoidal, AC power is generated within generator rotor122and is transmitted to power conversion assembly210via rotor bus212. Within power conversion assembly210, the electrical power is transmitted to rotor filter218and the electrical power is modified for the rate of change of the PWM signals associated with rotor-side power converter220. Rotor-side power converter220acts as a rectifier and rectifies the sinusoidal, three-phase AC power to DC power. The DC power is transmitted into DC link244. Capacitor250facilitates mitigating DC link244voltage amplitude variations by facilitating mitigation of a DC ripple associated with AC rectification.

The DC power is subsequently transmitted from DC link244to line-side power converter222and line-side power converter222acts as an inverter configured to convert the DC electrical power from DC link244to three-phase, sinusoidal AC electrical power with pre-determined voltages, currents, and frequencies. This conversion is monitored and controlled via converter controller262. The converted AC power is transmitted from line-side power converter222to system bus216via line-side power converter bus223and line bus225, line contactor226, conversion circuit breaker bus230, conversion circuit breaker228, and connection bus232. Line filter224compensates or adjusts for harmonic currents in the electric power transmitted from line-side power converter222. Stator synchronizing switch206is configured to close to facilitate connecting the three-phase power from generator stator120with the three-phase power from power conversion assembly210.

Conversion circuit breaker228, main transformer circuit breaker214, and grid circuit breaker238are configured to disconnect corresponding buses, for example, when excessive current flow may damage the components of electrical and control system200. Additional protection components are also provided including line contactor226, which may be controlled to form a disconnect by opening a switch (not shown inFIG.2) corresponding to each line of line bus225.

Power conversion assembly210compensates or adjusts the frequency of the three-phase power from generator rotor122for changes, for example, in the wind speed at hub110and blades108. Therefore, in this manner, mechanical and electrical rotor frequencies are decoupled from stator frequency.

Under some conditions, the bi-directional characteristics of power conversion assembly210, and specifically, the bi-directional characteristics of rotor-side power converter220and line-side power converter222, facilitate feeding back at least some of the generated electrical power into generator rotor122. More specifically, electrical power is transmitted from system bus216to connection bus232and subsequently through conversion circuit breaker228and conversion circuit breaker bus230into power conversion assembly210. Within power conversion assembly210, the electrical power is transmitted through line contactor226, line bus225, and line-side power converter bus223into line-side power converter222. Line-side power converter222acts as a rectifier and rectifies the sinusoidal, three-phase AC power to DC power. The DC power is transmitted into DC link244. Capacitor250facilitates mitigating DC link244voltage amplitude variations by facilitating mitigation of a DC ripple sometimes associated with three-phase AC rectification.

The DC power is subsequently transmitted from DC link244to rotor-side power converter220and rotor-side power converter220acts as an inverter configured to convert the DC electrical power transmitted from DC link244to a three-phase, sinusoidal AC electrical power with pre-determined voltages, currents, and frequencies. This conversion is monitored and controlled via converter controller262. The converted AC power is transmitted from rotor-side power converter220to rotor filter218via rotor filter bus219and is subsequently transmitted to generator rotor122via rotor bus212, thereby facilitating sub-synchronous operation.

Power conversion assembly210is configured to receive control signals from turbine controller202. The control signals are based on sensed conditions or operating characteristics of wind turbine100and electrical and control system200. The control signals are received by turbine controller202and used to control operation of power conversion assembly210. Feedback from one or more sensors may be used by electrical and control system200to control power conversion assembly210via converter controller262including, for example, conversion circuit breaker bus230, stator bus and rotor bus voltages or current feedbacks via second set of voltage and electric current sensors254, third set of voltage and electric current sensors256, and fourth set of voltage and electric current sensors264. Using this feedback information, and for example, switching control signals, stator synchronizing switch control signals and system circuit breaker control (trip) signals may be generated in any known manner. For example, for a grid voltage transient with predetermined characteristics, converter controller262will at least temporarily substantially suspend the IGBTs from conducting within line-side power converter222. Such suspension of operation of line-side power converter222will substantially mitigate electric power being channeled through power conversion assembly210to approximately zero.

In the exemplary embodiment, generator118, power conversion assembly210electrically coupled to generator118and step-up transformer234form the power conversion system of wind turbine100.

FIG.4Aillustrates a block diagram of a wind turbine400. Wind turbine400is typically similar to wind turbine100explained above with regard toFIG.1toFIG.3and also has a nacelle402, a power conversion system410arranged in nacelle402, mechanically connected with a rotor, and electrically connectable with a utility grid for feeding electrical output power P to the utility grid, typically via a grid circuit breaker238and optionally via a further transformer (outside nacelle402), for example a wind farm transformer.

In the exemplary embodiment, an air-cooling system450, which is typically implemented as and/or provided by an air conditioning system, is arranged on and/or at nacelle402.

In a cooling mode, air-cooling system450cools the ambient air28areceived from outside nacelle401from ambient air temperature Ta to a lower temperature Tc, and feeds or discharges the cooled ambient air as cooling air28cinto the inner of nacelle402, more particular towards or even to a cooling system430of power conversion system410, in particular via an air supply duct arranged between an outlet of air-cooling system450for the cooled ambient air28cand a cooling air inlet of cooling system430for removing excess heat Q from power conversion system420. In this process, cooling air28cis reheated and discharged from nacelle402as exhaust air28dof higher temperature Td, typically via an exhaust duct.

As further illustrated inFIG.4A, air-cooling system450can be provided with electric power Pi from power conversion system420via an internal electric power distribution system470.

Typically, at least a generator of power conversion system410can be cooled using cooling system430which is provided with cooled ambient air28cby air-cooling system430if desired, in particular at higher ambient air temperature Ta, if a high waste heat Q is to be removed and/or if the power conversion system410is desired to deliver large amount of (active and/or reactive) power P to the grid.

Alternatively or in addition, a gearbox, a power converter, a transformer and/or an electric cabinet of power conversion system410may be cooled in this way to keep the respective component below a respective threshold temperature. For example, the air conditioning system may be connected to a gearbox cooler via a liquid-liquid heat exchanger.

The temperature Tc of the cooled ambient air and cooling air28c, respectively, and/or the temperature difference Ta−Tc may even be controllable.

Typically, the temperature of one or more of the components of power conversion system410are controlled by a turbine controller communicatively coupled via a data bus and/or respective data lines with air-cooling system450, cooling system430, power conversion system410, power conversion components of power conversion system410and/or respective temperature sensors.

For cooling the power conversion system410and its power conversion components, respectively, cooling system430may have one or more closed cooling circuits for removing heat Q which are circulated with a respective coolant that can be cooled with cooling air28c, for example one (or even more) respective closed cooling circuits for each power conversion components.

Such a closed cooling circuit is shown inFIG.4Billustrating a block diagram of a wind turbine400which is typically similar to and may even correspond to wind turbine400explained above with regard toFIG.4A.

In the exemplary embodiment, air-cooling system450includes a first open cooling circuit C1for receiving ambient air28′ at a first inlet and a second open cooling circuit C2for receiving ambient air28at a second inlet. The open cooling circuits C1, C2are thermally coupled with each other via a heat exchanger H12of air-cooling system450so that, in the cooling mode, heat is transferred from ambient air28areceived at the second inlet to ambient air28a′ received at the first inlet. While heated air of first open cooling circuit C1is, in the cooling mode, discharged at a first outlet as first exhaust air28d′ at higher temperature Te>Ta, cooled ambient air of the second open cooling circuit C2is discharged as cooling air28cof lower temperature Tc<Ta at a second outlet and transferred to an exemplary fan F of a cooling system430for pumping cooling air28cthrough an open cooling circuit C3of cooling system430. The open cooling circuit C3is thermally coupled via a heat exchanger H34of cooling system430with one exemplary closed cooling circuit C4for removing heat Q from power conversion system410.

Accordingly, a cascade of four cooling circuits C1-C4thermally coupled to one another may be used for cooling power conversion system410.

However, it is also possible that only three cooling circuits thermally coupled to one another are used for cooling power conversion system410.

For example, the first open cooling circuit C1may be omitted, for example in an embodiment in which heat exchanger H12implemented as thermoelectric cooler, i.e. based on thermoelectric cooling of ambient air28in open cooling circuit C2and the transferred heat discharged via cooling fins or the like.

However, due to the higher efficiency, heat exchanger H12is typically implemented as a vapor-compression systems (even having an additional internal closed cooling circuit).

This may also apply to heat exchanger H34.

FIG.4Cillustrates a flow chart of a method1000of operating a wind turbine, in particular a wind turbine100,400,400′ as explained above with regard toFIG.1toFIG.4B. As such the wind turbine has a power conversion system for providing electrical output power to a grid, in particular a utility grid, and an air-cooling system for providing (in a cooling mode) cooled ambient air as a cooling air to the power conversion system.

Typically during operating the wind turbine in a normal operating mode, in which the power conversion system converts input motive power received from the rotor into electrical output power and provides a least a major portion of the electrical output power to the utility grid, method1000includes a block (step)1100of operating the air-cooling system in the cooling mode and providing cooled ambient air as a cooling air to the power conversion system, respectively.

According to an embodiment, block1100is performed depending on at least one operating parameter of the power conversion system and/or if the at least one operating parameter is equal to or greater than a respective threshold.

Accordingly, block1100is typically performed depending on determining the at least one operating parameter, e.g. including measuring one or more respective temperature, or receiving the at least one operating parameter in a preceding block1050.

As indicated by the dashed arrow inFIG.4C, method1000may return from block1100to block1050at a later time to start a new control cycle.

Further, only if, despite cooling the power conversion system using the cooled ambient air as cooling air, a temperature of the power conversion system (e.g. at least one power component thereof) is equal to or greater than a respective upper temperature threshold (third temperature threshold), reactive output power of the power conversion system and/or a reactive output power of the power conversion system may be curtailed in a subsequent block1200.

FIG.5Aillustrates a flow chart of a method2000of operating a wind turbine, in particular a wind turbine100,400,400′ as explained above with regard toFIG.1toFIG.4B.

Method2000is typically similar to method1000explained above with regard toFIG.4Cand also includes a block2100of operating the wind turbine's air-cooling system in the cooling mode. However, method2000is more specific.

In the exemplary embodiment, the air-cooling system is operated in the cooling mode only if both the temperature Ta of the ambient air is equal to or greater than an ambient temperature threshold Th_Ta of e.g. 30° or 35° C., and at least one of the following to conditions is met: (a) a reactive power demand RPD of the power conversion system is equal to or greater than a reactive power demand threshold Th1_RPD, and (b) an active power demand APD of the power conversion system is equal to or greater than an active power demand threshold Th1_APD.

Otherwise, the active and typically also the reactive power production of the power conversion system is controlled in a block2300without using the cooling mode of the air-cooling system for increasing heat removal from the power conversion system which is not desired under this conditions.

Method2000may be considered as proactively increasing the heat removal from the power conversion system at high power demand and high ambient temperature which otherwise may result in to high thermal loads for components of the power conversion system.

To reduce control induced fluctuations and/or to save energy, air-cooling system may also only be operated in the cooling mode if the above conditions (Ta>=Th_Ta and (RPD>Th1_RPD or APD>=Th1_APD)) are met for a respective predetermined time period of e.g. one or several seconds.

FIG.5Billustrates a flow chart of a method3000of operating a wind turbine, in particular a wind turbine100,400,400′ as explained above with regard toFIG.1toFIG.4B.

Method3000is typically also similar to method1000explained above with regard toFIG.4Cand also includes a corresponding block2100of (activating or maintaining) operating the wind turbine's air-cooling system in the cooling mode. However, method3000is more specific.

In the exemplary embodiment, the cooling mode is activated in block3100if a temperature Tc of the cooling air is equal to or greater than a first cooling air temperature threshold Th1_Tc, if a temperature TGS of a generator stator is equal to or greater than a first generator stator temperature threshold Th1_TGS, or if a temperature TGB of a generator bearing is equal to or greater than a first generator bearing temperature threshold Th1_TGB.

The temperatures Tc, TGS and TGB are typically monitored in a block3050.

After activating the cooling mode, it may be checked if the temperatures Tc, TGS and TGB nevertheless exceed or at least reach a respective higher third temperature threshold Th3_Tc (>Th1_Tc), Th3_TGS (>Th1_TGS), Th3_TGB (>Th1_TGB).

If so, power curtailment may be activated for the power conversion system to avoid over heating in a block3200.

Otherwise, it may be checked if all temperatures Tc, TGS and TGB are below a respective second temperature threshold Th2_Tc (Th2_Tc<Th1_Tc), Th2_TGS (Th2_TGS<Th1_TGS), Th2_TGB (Th2_TGS<Th1_TGS).

If so, the cooling mode may be deactivated and method3000may return to block3050. Otherwise, cooling mode is maintained.

Compared to method2000explained above with regard toFIG.5A, air-cooling system is operated in the cooling mode depending on the monitored generator temperatures. Accordingly, the cooling mode is only used when actually desired.

Alternatively or in addition, the temperatures of other power conversion components may be taken into account for controlling (activating/deactivating) the cooling mode.

Furthermore, one or more thermal properties of the wind turbine and its components, respectively, in particular the power conversion component(s), such as respective thermal time constants may be taken into account for controlling the cooling mode (operating the air-cooling system).

Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

Embodiments of the present invention have been described above with reference to block diagrams and flowchart illustrations of methods, apparatuses (i.e., systems) and computer program products. It will be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, respectively, can be implemented by various means including computer program instructions. These computer program instructions may be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus, such as the processor(s)204discussed above with reference toFIG.3, to produce a machine, such that the instructions which execute on the computer or other programmable data processing apparatus create a means for implementing the functions specified in the flowchart block or blocks.

These computer program instructions may also be stored in a non-transitory computer-readable memory that can direct a computer or other programmable data processing apparatus (e.g., processor(s)204ofFIG.3) to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including computer-readable instructions for implementing the function specified in the flowchart block or blocks. The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process such that the instructions that execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart block or blocks.

Accordingly, blocks of the block diagrams and flowchart illustrations support combinations of means for performing the specified functions, combinations of steps for performing the specified functions and program instruction means for performing the specified functions. It will also be understood that each block of the block diagrams and flowchart illustrations, and combinations of blocks in the block diagrams and flowchart illustrations, can be implemented by special purpose hardware-based computer systems that perform the specified functions or steps, or combinations of special purpose hardware and computer instructions.

Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is no way intended that an order be inferred, in any respect. This holds for any possible non-express basis for interpretation, including: matters of logic with respect to arrangement of steps or operational flow; plain meaning derived from grammatical organization or punctuation; the number or type of embodiments described in the specification.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, those skilled in the art will recognize that the spirit and scope of the claims allows for equally effective modifications. Especially, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. For example, at least one of the power conversion components such as the transformer may at least partly be located in the tower or a base instead of the nacelle. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

REFERENCE NUMBERS

wind turbine100,400,400′nacelle102,402tower104yaw system105rotor106meteorological mast107blades108pitch system109hub110low speed shaft112gearbox114generator118generator stator120generator rotor122control system200turbine controller202processor204synchronizing switch206memory207stator bus208communications module209power conversion assembly210,410sensor interface211rotor bus212transformer circuit breaker214system bus216rotor filter218filter bus219rotor-side power converter220line side power converter222line side power converter bus223line filter224line bus225line contactor226conversion circuit breaker228conversion circuit breaker bus230connection bus232electric power main transformer234generator-side bus236grid circuit breaker238breaker-side bus240distribution grid via a grid bus242DC link244positive rail246negative rail248capacitor250electric current sensors252electric current sensors254electric current sensors256temperature sensors257,258converter controller262electric current sensors264cooling system430air-cooling system450internal grid470method, method steps1000-3200reactive power demand RPDactive power demand APDtemperature of stator TGStemperature of bearing TGBtemperature Ta-Tdthresholds for parameter Th*_parametercooling circuits C1-C4fan Fheat exchanger H12, H34power Pheat Q