Method and apparatus for controlling rotary machines

A wind turbine generator includes at least one rotating member, at least one stationary member, and a clearance gap control system. The stationary member is positioned such that a clearance gap is defined between a portion of the rotating member and a portion of the stationary member. The clearance gap is configured to facilitate transmitting a controllable magnetic flux therethrough. The control system includes at least one clearance gap measurement assembly, at least one power converter, and at least one controller. The controller is coupled in electronic data communication with the assembly and the converter and is configured to modulate a dimension of the gap by modulating the flux.

BACKGROUND OF THE INVENTION

This invention relates generally to rotary machines and more particularly, to methods and apparatus for controlling wind turbine generator air gap dimensions.

Generally, a wind turbine generator includes a rotor having multiple blades. The rotor is sometimes mounted within a housing, or nacelle, that is positioned on top of a base, for example a truss or tubular tower. At least some known utility grade wind turbines (i.e., wind turbines designed to provide electrical power to a utility grid) can have rotors of 30 meters (m) (98 feet (ft)) or more in diameter. The rotor blades transform mechanical wind energy into a mechanical rotational torque that drives one or more generators. The generators are sometimes, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the turbine rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into the utility grid. Gearless direct drive wind turbine generators also exist.

In the generator, rotor components and stator components are separated by a clearance gap, sometimes referred to as an air gap. A uniform air gap facilitates operation of the generator. During operation, a magnetic field generated by a plurality of permanent magnets or wound coil magnets mounted on the rotor or stator passes through a portion of the air gap defined between the rotor and the stator. A plurality of forces that are at least partially proportional to the magnitude and direction of the magnetic field are induced. These induced forces include, but are not limited to, radial and axial forces across the air gap, and torque forces, such that a plurality of forces are acting on the rotor. Transmission of the magnetic field through the air gap may be at least partly dependent on a magnitude of each of the induced magnetomotive forces (MMF) and a predetermined magnitude of an air gap radial dimension, i.e., the radial distance between a rotor surface and a stator surface. However, asymmetric and/or transient loads on the rotor may be introduced via the blades and/or other mechanisms. Such asymmetric and/or transient loads may sometimes deflect the rotor such that the air gap dimension is reduced and/or altered to be non-uniform.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a generator includes at least one rotating member, at least one stationary member, and a clearance gap control system. The stationary member is positioned such that a clearance gap is defined between a portion of the rotating member and a portion of the stationary member. The clearance gap is configured to facilitate transmitting a controllable magnetic flux therethrough. The control system includes at least one clearance gap measurement assembly, at least one power converter, and at least one controller. The controller is coupled in electronic data communication with the assembly and the converter and is configured to modulate a dimension of the gap by modulating the flux.

In another aspect, a method of controlling a clearance gap dimension within a generator is provided. The generator has at least one rotating member and at least one stationary member positioned such that a clearance gap is defined between a portion of the rotating member and a portion of the stationary member. The clearance gap has a measurable dimension. The method includes modulating the clearance gap dimension by modulating a controllable magnetic flux generated within the clearance gap.

In a further aspect, a control system for a rotary machine is provided. The rotary machine includes at least one rotating member and at least one stationary member positioned such that a clearance gap is defined between a portion of the rotating member and a portion of the stationary member. The clearance gap is configured to facilitate transmitting a controllable magnetic flux therethrough. The control system includes at least one clearance gap measurement assembly, at least one power converter, and at least one controller. The controller is coupled in electronic data communication with the assembly and the converter and is configured to modulate the clearance gap measurement by modulating the magnetic flux.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is an exploded schematic view of an exemplary wind turbine generator100. In the exemplary embodiment, wind turbine generator100is a horizontal axis wind turbine. Alternatively, wind turbine100may be a vertical axis wind turbine. Also, alternatively, wind turbine100may be a 1.5 Megawatt (MW)-series or a 2.5 MW-series wind turbine generator commercially available from General Electric Company, Schenectady, N.Y. Further, alternatively, wind turbine100may be any wind turbine generator that the invention described herein may be embedded. Wind turbine100includes a mounting fixture102extending from either a tower or a supporting surface (neither shown inFIG. 1). In the event that a tower is used, a height of the tower is selected based upon factors and conditions known in the art. Wind turbine100also includes a hub assembly104, a shell106, a cover assembly108, and a main frame110. Shell106is fixedly coupled to main frame110and cover assembly108is removably coupled to main frame110. Hub assembly104is removably coupled to shell106. Hub assembly104, shell106, cover assembly108and main frame110cooperate to facilitate load support and load distribution within wind turbine100. Cover assembly108includes an integrated cooling system (not shown inFIG. 1) that facilitates maintaining wind turbine100components within hub104, shell106and cover108within predetermined operational temperature parameters.

Hub104includes a plurality of blade support sleeves112disposed substantially equidistantly circumferentially about hub104. In the exemplary embodiment, wind turbine100has three blade support sleeves112. Alternatively, hub104may have more or less than three blade support sleeves112. Also, in the exemplary embodiment, sleeves112are substantially cylindrical tubes. Alternatively, sleeves112may be of any configuration that facilitates predetermined operational parameters of wind turbine100. Hub104also includes a nose element114that facilitates an aerodynamic efficiency of wind turbine100. Hub104is coupled to shell106via a hub face plate116and a frame mating surface118. A substantially annular interior surface portion117of shell106and plate116at least partially define a cavity120when plate116and surface118are coupled. A main bearing122and a support member123are positioned within cavity120. Bearing122facilitates radial support and alignment of hub104and includes a radially outermost surface121. Member123facilitates support and alignment of bearing122within wind turbine100and includes a radially inner surface119and a radially outer surface125. Surface119is coupled to surface121via a friction fit prior to bearing122and member123positioning within cavity120. Surface125is coupled to surface117via a friction fit upon positioning bearing122and member123within cavity120.

Wind turbine generator100further includes a generator124that facilitates converting wind energy as captured by hub assembly104and generating electrical energy for subsequent transmission to an electrical distribution system (not shown inFIG. 1). A rotor (not shown inFIG. 1) is rotatably coupled to hub104and extends to generator124. The rotor is coupled to a rotatable exciter (not shown inFIG. 1) that is disposed within generator124. In the exemplary embodiment, generator124is a direct-drive generator, i.e., hub104drives generator124exciter directly via the rotor. Alternatively, a gearbox (not shown inFIG. 1) is positioned between hub assembly104and generator124and is used to step up a rotational speed generated by hub104to a generator124exciter speed that is substantially synchronous.

In the exemplary embodiment, a hub-to-gearbox/hub-to-direct-drive generator connector126is also disposed within cavity120. Connector126facilitates radial support and alignment of the rotor from hub104to generator124(in the exemplary embodiment) or to a gear box (in an alternative embodiment). Connector126includes a plurality of passages128that facilitate personnel and material transport between hub104and the portions of wind turbine100defined within shell106and cover108. Some alternative embodiments of wind turbine100exclude connector126.

Blade support sleeves112are each configured to receive a blade (not shown inFIG. 1). In the exemplary embodiment, hub104receives three rotor blades. In an alternative embodiment, hub104receives any number of blades that facilitates attaining predetermined operational parameters of wind turbine100. The blades are positioned about hub104to facilitate rotating hub104to transfer kinetic energy from the wind into usable mechanical energy via the rotor, and subsequently, electrical energy within generator124. The blades may have any length that facilitates wind turbine100performing as described herein.

At least one pitch drive mechanism (not shown inFIG. 1) modulates a pitch angle of the blades along a pitch axis (not shown inFIG. 1). As such, the blades may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position and facilitate increasing or decreasing the blades rotational speed by adjusting the surface area of the blades exposed to the wind force vectors, i.e., by adjusting the wind loading on the blades.

Wind turbine100also includes a yaw adjustment mechanism130that may be used to rotate wind turbine100on an axis (not shown inFIG. 1) to control the perspective of wind turbine100with respect to the direction of the wind. Mechanism130is coupled to main frame110and to a yaw bearing132and at least one yaw drive gear (not shown inFIG. 1) wherein bearing132and the drive gear are coupled to mounting fixture102. Bearing132facilitates support and alignment of wind turbine100during yaw adjustment operations.

In some configurations, one or more microcontrollers in a control system (not shown inFIG. 1) are used for overall system monitoring and control including pitch and yaw adjustments, rotor speed regulation, yaw brake application, and fault monitoring. Alternatively, distributed or centralized control architectures are used in alternate embodiments of wind turbine100.

FIG. 2is a block diagram of an exemplary clearance gap control system200that may be used with, but is not limited to being used with, wind turbine generator100(shown inFIG. 1). In the exemplary embodiment, generator124is a round rotor, synchronous, three-phase, permanent magnet generator124that includes a rotor202and a stator204. However, generator124may be any type of generator including, but not limited to, salient pole generators, double-sided stator generators, and/or doubly-fed induction generators. In the exemplary embodiment, rotor202includes a plurality of permanent magnets206that are coupled to rotor202. Alternatively, rotor202may be a wound rotor wherein the associated windings (neither shown inFIG. 2) are separately-excited, for example, but not limited to, a salient-pole rotor. Rotor202and stator204are positioned such that a clearance gap208(sometimes referred to as an air gap208) is defined between stator204and rotor202with a pre-determined clearance gap radial dimension209that is substantially circumferentially similar about rotor202and stator204while rotor202is stationary. Permanent magnets206with pre-determined polarities are positioned to generate a magnetic field (not shown inFIG. 2) around rotor202with a pre-determined number of poles and a pre-determined magnetic strength.

Stator204includes a plurality of stator windings210,212, and214. Gap208facilitates magnetic coupling of rotor202and stator windings210,212, and214to generate a pre-determined voltage within stator windings210,212, and214at a pre-determined frequency that is determined by rotor202rotational speed as rotor202is rotated within stator204. The generated voltages within stator windings210,212, and214subsequently generate a pre-determined electric current within windings210,212, and214. The electric currents generated within windings210,212, and214subsequently generate a plurality of magnetic fields and as the magnetic field generated in rotor202rotates, the magnetic field of rotor202interacts with the magnetic fields of stator windings210,212, and214through gap208. The interaction of the magnetic fields induces magnetomotive axial and radial forces and a torque that act on rotor202. Loads induced within rotor202by asymmetric and/or transient loads introduced via the blades and/or other drive components may shift an axis of rotation of rotor202radially away from a nominal generator centerline axis of rotation216such that a clearance gap radial dimension209is reduced and/or altered to be non-uniform circumferentially within generator124. Axis of rotation216is substantially parallel to a wind turbine100axis of rotation. Radial and axial forces induced on rotor202by the interaction of the magnetic fields are proportional to the strength and position of the magnetic flux component within gap208and is also sometimes substantially uniform about gap208. As the flux component in gap208increases, the radial and axial forces induced on rotor202increase, and the attractive force between rotor202and stator204is increased. Similarly, as the flux component in gap208decreases, the radial and axial forces induced on rotor202decrease, and the attractive force between rotor202and stator204is decreased. Therefore, modulating the flux and the radial and axial forces induced on rotor202may facilitate decreasing a tendency of rotor202axis of rotation to radially shift away from axis of rotation216and to facilitate mitigating radial dimension209reduction and/or alteration to be non-uniform circumferentially. A pre-determined range of radial dimension209tolerances may be provided for.

System200includes a plurality of clearance gap measurement assemblies218,220, and222associated with stator windings210,212, and214, respectively. Assemblies218,220, and222are positioned on a radially inner portion of stator204. In the exemplary embodiment, assemblies218,220, and222are proximity apparatus that are configured to measure radial dimension209within the vicinity of windings210,212, and214, respectively. Alternatively, assemblies218,220, and222are flux measurement apparatus configured to measure a magnetic flux within the vicinity of windings210,212, and214, respectively. In some embodiments, assemblies218,220, and222are each configured to measure both dimension209and the associated magnetic flux. Although three measurement assemblies are discussed and illustrated hereon, any number of measurement assemblies with any apparatus in any configuration may be used with control system200, whether such number is described and/or illustrated hereon.

Assemblies218,220, and222are coupled in electronic data communication with at least one controller224via a plurality of sensor cables226,228and230, respectively. In the exemplary embodiment, sensor cables226,228and230define a plurality of controller input channels226,228and230. In additional or alternatively, a network of transmitters and receivers operating in the radio frequency (RF) band may be used to define controller input channels226,228and/or230.

Controller224includes at least one processor and a memory, at least one processor input channel, at least one processor output channel, and may include at least one computer (none shown inFIG. 2).

As used herein, the term computer is not limited to just those integrated circuits referred to in the art as a computer, but broadly refers to a processor, a microcontroller, a microcomputer, a programmable logic controller (PLC), an application specific integrated circuit, and other programmable circuits (none shown inFIG. 2), and these terms are used interchangeably herein. In the exemplary embodiment, memory may include, but is not limited to, a computer-readable medium, such as a random access memory (RAM) (none shown inFIG. 2). Alternatively, a floppy disk, a compact disc-read only memory (CD-ROM), a magneto-optical disk (MOD), and/or a digital versatile disc (DVD) (none shown inFIG. 2) may also be used. Also, in the exemplary embodiment, additional input channels (not shown inFIG. 2) may be, but not be limited to, computer peripherals associated with an operator interface such as a mouse and a keyboard (neither shown inFIG. 2). Alternatively, other computer peripherals may also be used that may include, for example, but not be limited to, a scanner (not shown inFIG. 2). Furthermore, in the exemplary embodiment, additional output channels may include, but not be limited to, an operator interface monitor (not shown inFIG. 2).

Processors for controller224process information, including clearance gap dimension209signals and/or clearance gap magnetic flux signals from assemblies218,220, and222via controller input channels226,228and230, respectively. RAM and storage device store and transfer information and instructions to be executed by the processor. RAM and storage devices can also be used to store and provide temporary variables, static (i.e., non-changing) information and instructions, or other intermediate information to the processors during execution of instructions by the processors. Instructions that are executed include, but are not limited to, resident conversion and/or comparator algorithms. The execution of sequences of instructions is not limited to any specific combination of hardware circuitry and software instructions.

Controller224is coupled in electronic data communication with a plurality of generator power converters232,234and236via controller output channels238,240, and242, respectively. In the exemplary embodiment, output channels238,240, and242are cables238,240, and242, respectively. In addition or alternatively, a network of transmitters and receivers operating in a predetermined portion of a radio frequency (RF) band may be used to define output channels238,240, and/or242.

Stator windings210,212, and214are coupled in electric connection with converters232,234, and236, respectively, via electricity conduits244,246, and248, respectively. In the exemplary embodiment, conduits244,246, and248are a plurality of electrical cables244,246, and248that are configured to transmit pre-determined electric power at pre-determined currents, voltages and frequencies that are generated by generator124. In addition or alternatively, conduits244,246, and/or248are any electric power transmission device that includes, but is not limited to, bus bars and cables.

Specifically, in the exemplary embodiment, each of plurality of cables244,246, and248include at least one cable for each of three phases associated with generator124. Alternatively, any number of phases may be associated with generator124that facilitates operation of generator124as described herein. More specifically, cable244includes a cable each for an A-phase, B-phase, and C-phase labeled A, B, and C, respectively. Similarly, cable246includes a cable each for the A-phase, B-phase, and C-phase labeled A′, B′, and C′, respectively. Moreover, similarly, cable248includes a cable each for the A-phase, B-phase, and C-phase labeled A″, B″, and C″, respectively.

Converters232,234, and236convert the alternating current (AC) signals transmitted from stator204into direct current (DC) signals by AC rectification. Moreover, in the exemplary embodiment, converters232,234, and236are coupled in electrical communication with a single direct current (DC) link250. Alternatively, converters232,234, and236are coupled in electrical communication with individual and separate DC links (not shown inFIG. 2). DC link250includes a positive rail252, a negative rail254, and at least one capacitor256coupled therebetween. In the exemplary embodiment, capacitor256facilitates mitigating DC link250voltage variations by facilitating mitigation of a DC ripple sometimes associated with three-phase AC rectification. Alternatively, capacitor256is one or more capacitors configured in series or in parallel between rails252and254.

Control system200further includes a plurality of grid power converters258that are coupled in electrical communication with DC link250by a plurality of positive and negative conduits260. In the exemplary embodiment, there are three grid power converters258and three sets of conduits260. However, any number of converters258and conduits260may be used, whether such number is described and/or illustrated hereon. Also, in the exemplary embodiment, conduits260are any electric power transmission device that includes, but is not limited to, bus bars and cables. In the exemplary embodiment, converters258are inverters that convert the DC electricity from DC link250to three-phase AC with pre-determined voltages, currents, and frequencies and are controlled by a controller (not shown inFIG. 3) similar to controller224. Specifically, in the exemplary embodiment, converters258are configured to transmit 60 Hz three-phase AC to an electrical power grid (not shown inFIG. 3) via a plurality of grid conduits262. However, converters258may be configured to transmit AC electrical power at any frequency, whether such frequency is described and/or illustrated hereon. Conduits262may be any electric power transmission device that includes, but is not limited to, bus bars and cables.

FIG. 3is a schematic view of an exemplary generator power converter232that may be used with, but is not limited to being used with, clearance gap control system200(shown inFIG. 2). Converters234and236are substantially identical. Capacitor256is illustrated for perspective. A plurality of switching devices is provided in connection with each of phase cables A, B, and C of stator output cables244(shown inFIG. 2), each cable corresponding to each of the three phases of the electrical output power from stator windings210(shown inFIG. 2). Specifically, a first switching module300, a second switching module302and a third switching module304are provided, each corresponding to a different phase of power output generated by stator windings210. Each of switching modules300,302and304include a pair of switching devices. More specifically, in the exemplary embodiment, first switching module300includes a first switching device306and a second switching device308; second switching module302includes a third switching device310and a fourth switching device312; and third switching module304includes a fifth switching device314and a six switching device316.

Converter232uses pulse width modulation (PWM) methods to control stator windings210output current. In the exemplary embodiment, each of switching devices306-316is an insulated gate bipolar transistor (IGBT) switching device306-316and includes a corresponding diode318,320,322,324,326and328, respectively. Alternatively, switching devices306-316may include, but not be limited to, a plurality of integrated gate commutated thyristors (IGCTs) and a plurality of thyristors (neither shown inFIG. 3). Further, alternatively, any type of switching device that facilitates operation of system200as described herein may be used. Switching devices306-316are configured such that a gate330,332,334,336,338, and340of each of switching devices306-316is coupled in electronic data communication with a control line342,344,346,348,350, and352, respectively, and diodes318-328are connected between a plurality of collectors354,356,358,360,362, and364and a plurality of emitters366,368,370,372,374, and376of switching devices306-316, respectively. Switching, or modulating, of switching devices306-316is controlled by a controller224output signal (not shown inFIG. 3) transmitted to gates330-340of switching devices306-316, respectively. In the exemplary embodiment, the controller output signals are transmitted from controller224(shown inFIG. 2) via controller output cable238(shown inFIG. 2). Specifically, cable238includes lines342-352. Phase cable A is coupled in electrical communication with first switching module300between emitter366of first switching device306and collector356of second switching device308. Phase cables B and C are coupled in electrical communication with second and third switching modules302and304in a substantially similar manner.

Collectors354,358, and360of first, third and fifth switching devices318,322, and326, respectively, are connected to positive rail252of DC link250(shown inFIG. 3). Emitters368,372, and376of second, fourth, and sixth switching devices308,312and316, respectively are connected to negative rail254of DC link250. Rail252is maintained at a positive capacitive voltage and rail254is maintained at a zero capacitive voltage, both capacitive voltages being referenced to negative rail254.

A method of controlling clearance gap dimension209within generator124, generator124having at least one rotating member202and at least one stationary member204positioned such that clearance gap208is defined between a portion of rotating member202and a portion of stationary member204, includes modulating clearance gap dimension209by modulating a controllable magnetic flux generated within clearance gap208.

FIGS. 2 and 3are referenced together for the operational discussion of control system200. During operation, for example, in the event that some wind forces are such that the blades tend to be positioned to a deflected position, torsional loads and subsequent stresses may be induced within the blades. These stresses are transferred from the blades to hub104. The transferred stresses within hub104are transferred to rotor202. In some instances, stresses transferred into rotor202may deflect rotor202such that rotor202radial position may be within the tolerances of bearing118such that dimension209of gap208is altered and predetermined gap dimension209tolerances are approached. Assemblies218,220, and222monitor dimensions209of and/or the magnetic flux of gap208and transmit the associated clearance gap radial dimension signals, or gap dimension signals, and/or clearance gap magnetic flux signals, or flux signals, (neither shown inFIGS. 2 and 3) to controller224by controller input channels226,228, and230, respectively. The gap dimension and/or the flux signals are voltage or electrical current signals converted to dimension measurements and/or magnetic flux measurements by at least one resident conversion algorithm within the at least one processor of controller224.

The processor of controller224generates internal processor clearance gap dimension measurement and/or flux measurement signals and uses at least one resident control algorithm to compare these dimension and/or flux measurements to at least one predetermined clearance gap dimension and/or predetermined flux measurement, or a range thereof (neither shown inFIGS. 2 and 3). If any deviations are determined, the processor generates internal processor clearance gap dimension and/or flux adjustment signals (not shown inFIGS. 2 and 3) that is converted to processor output signals (not shown inFIGS. 2 and 3) by at least one resident clearance gap dimension and/or flux adjustment algorithm. The processor output signals are transmitted as controller output signals via output channels238,240, and242to converters232,234, and236, respectively. Operation of converter232is discussed further below. Converters234and236operate in a substantially similar manner. The controller output signals are transmitted to switching devices306-316and are switched in a PWM manner to control the frequency, the phase angle and the amplitude of the voltage and current (and, therefore, power) signals received from stator windings210and are subsequently converted and transmitted to DC link250.

In the exemplary embodiment, control system200is configured to allow controller224to control converters232,234, and236independently. Specifically, in the event that rotor202is deflected such that gap dimension209is smaller at windings210than dimension209at windings212and214, controller224will transmit signals to converter232to decrease the radial air gap flux generated at windings210. A decrease in radial air gap flux generated within a set of windings, for example windings210, facilitates a decrease in radial force induced on rotor202in the vicinity of windings210. Moreover, in this example, controller224will transmit signals to converters234and236to increase the radial air gap flux generated at windings212and214, which thereby facilitates an increase in the radial force induced on rotor202in the vicinity of windings212and214. The overall effect is to alter the attractive forces induced within generator124between rotor202and stator204to reposition rotor202such that gap dimensions measured by assemblies218,220, and222are substantially similar.

Similarly, in the event that rotor202is deflected such that gap dimension209is greater at windings210than dimension209at windings212and214, controller224will transmit signals to converter232to increase the radial air gap flux generated at windings210. An increase in the radial air gap flux generated within a set of windings, for example windings210, facilitates an increase in the radial force induced on rotor202in the vicinity of windings210. Moreover, in this example, controller224will transmit signals to converters234and236to decrease the radial air gap flux generated at windings212and214, which thereby facilitates a decrease in radial force induced on rotor202in the vicinity of windings212and214. The overall effect is to alter the attractive forces induced within generator124between rotor202and stator204to reposition rotor202such that gap dimensions measured by assemblies218,220, and222are substantially similar.

During the transients as described above, assemblies218,220, and222continue to transmit associated gap dimension209and/or flux measurement signals at a pre-determined update rate. As rotor202is repositioned, controller224receives the associated gap dimension209and/or flux measurement signals and the processor of controller224facilitates the modulation of the magnitude and duration of the controller output signals transmitted to converters232,234, and236. Moreover, to attain a pre-determined rate of rotor202repositioning, controller224again facilitates the modulation of the magnitude and duration of the controller output signals transmitted to converters232,234, and236. Upon dimension209of gap208being changed to a predetermined parameter or within a range of predetermined parameters as sensed by assemblies218,220, and222, control system200facilitates maintaining gap dimension209at a predetermined parameter or within a range of predetermined parameters within generator124(shown inFIG. 1).

The gap dimension209and/or magnetic flux signals as sensed and transmitted by assemblies218,220, and222may be used by either control system200or another control system to modulate other wind turbine100operational parameters including, but not being limited to, yaw and blade pitch orientations about the associated axis.

FIG. 4is a schematic view of another exemplary wind turbine generator400into which clearance gap control system200(shown inFIG. 2) may be embedded. Wind turbine generator400is a horizontal axis wind turbine. Alternatively, wind turbine400may be a vertical axis wind turbine. Wind turbine400includes a support frame402that is fixedly coupled to a tower extending from a supporting surface (neither shown inFIG. 4). Wind turbine400also includes a rotatable hub/rotor404and a plurality of rotor blades406coupled to hub/rotor404. In this alternative embodiment, wind turbine400has three rotor blades406(only two shown inFIG. 4) coupled to hub/rotor404. However, wind turbine400may have any number of rotor blades406, whether such number is described and/or illustrated hereon. In the embodiment ofFIG. 4, support frame402is includes a substantially annular cavity408. The height of the tower is selected based upon factors and conditions known in the art.

Blades406are positioned about hub/rotor404to facilitate rotating hub/rotor404to transfer kinetic energy from the wind into usable mechanical energy, and subsequently, electrical energy. Blades406are mated to hub/rotor404by coupling a blade root portion410to hub/rotor404at a plurality of load transfer regions412. Load transfer regions412have a hub/rotor load transfer region and a blade load transfer region (both not shown inFIG. 4). Loads induced in blades406are transferred to hub/rotor404via load transfer regions412.

In the embodiment ofFIG. 4, blades406may each have any suitable length, whether such length is described and/or illustrated hereon. As the wind strikes blades406, hub/rotor404is rotated about rotation axis414. As blades406are rotated and subjected to centrifugal forces, blades406are subjected to various bending moments and other operational stresses. As such, blades406may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position and associated stresses, or loads, may be induced in blades406. Moreover, a pitch angle (not shown inFIG. 4) of blades406, i.e., the angle that determines blades406perspective with respect to the direction of the wind, may be changed by a pitch adjustment mechanism (not shown inFIG. 4) to facilitate increasing or decreasing blade406speed by adjusting the surface area of blades406exposed to the wind force vectors. In this alternative embodiment, the pitches of blades406are controlled individually. Alternatively, blades406pitch may be controlled as a group.

In some configurations, one or more microcontrollers in a control system (not shown inFIG. 4) are used for overall system monitoring and control such as, but not limited to pitch and rotor speed regulation, yaw drive and yaw brake application, and fault monitoring. Alternatively, distributed or centralized control architectures are used in alternate embodiments of wind turbine400.

In the embodiment ofFIG. 4, various components of wind turbine400are housed within support frame cavity408. Hub/rotor404is rotatably coupled to an electric generator416. Also, in the embodiment ofFIG. 4, generator416is a V-shaped, synchronous, three-phase, permanent magnet generator416that includes a rotor418and a stator420. Alternatively, generator416is any type of generator including, but not limited to, salient pole generators, double-sided stator generators, and/or doubly-fed induction generators. In the embodiment ofFIG. 4, rotor418is an extension of hub/rotor404. Alternatively, rotor404may be a separate component rotatingly coupled to hub/rotor404using methods known in the art. In this alternative embodiment, rotor418includes a plurality of permanent magnets422that are coupled to rotor418. Alternatively, rotor418may be a wound rotor wherein the associated windings (neither shown inFIG. 4) are separately-excited, for example, but not limited to, a salient-pole rotor. Rotor418and stator420are positioned such that a clearance gap424(sometimes referred to as an air gap424) is defined between stator420and rotor418with a pre-determined clearance gap radial dimension (not shown inFIG. 4) that is substantially circumferentially similar about rotor418and stator420while rotor418is stationary. Permanent magnets422with pre-determined polarities are positioned to generate a magnetic field (not shown inFIG. 4) around a periphery of rotor418with a pre-determined number of poles and a pre-determined magnetic strength.

In the exemplary embodiment, stator420includes a plurality of three-phase forward stator windings423and a plurality of three-phase aft stator windings425. Windings423and425are substantially similar and are substantially electrically isolated from each other. Moreover, windings424and425are each electrically coupled to converters232,234and236(all three shown inFIG. 2) such that each of windings423and425may be controlled independently. Alternatively, windings423and425are manufactured as a single set of three-phase windings as is known in the art. The “v-shaped” configuration of generator416facilitates operation of wind turbine generator400as discussed further below.

Gap424facilitates magnetic coupling of permanent magnets422and windings423and425to generate pre-determined voltages within windings423and425at a pre-determined frequency that is determined by rotor418rotational speed as rotor418is rotated within stator420. The generated voltages within windings423and425subsequently generate pre-determined electric currents within windings423and425. The electric currents generated within windings423and425subsequently generate a plurality of stator magnetic fields (not shown). As the magnetic field (not shown) generated via rotor418rotates, the magnetic field of rotor418interacts with the magnetic fields of windings423and425through gap424. The interaction of the magnetic fields induces a torque on rotor418. Loads induced within rotor418by asymmetric and/or transient loads introduced via blades406or other drive components may shift an axis of rotation of rotor418radially away from nominal wind turbine centerline axis of rotation414such that the clearance gap424dimension is reduced and/or altered to be non-uniform circumferentially within generator416. The radial and axial forces induced on rotor418by the interaction of the magnetic fields are proportional to the strength and position of the magnetic flux components within gap424. Such radial and axial forces may be substantially uniform about gap424, or alternatively, may be non-symmetrical with respect to windings423and425. As the flux at any point within gap424increases, the associated radial and axial forces induced on rotor418in the vicinity of such point within gap424increases, and the attractive force between rotor418and stator420is increased in the vicinity of such point. Similarly, as the flux at any point in gap424decreases, the radial and axial forces induced on rotor418in the vicinity of such point within gap424decreases, and the attractive force between rotor418and stator420is decreased in the vicinity of such point. Therefore, modulating the flux and the radial and axial forces induced on rotor418via the interaction of the stator and rotor magnetic fields may facilitate decreasing a tendency of rotor418axis of rotation to radially shift away from axis of rotation414and to facilitate mitigating gap424dimension reduction and/or alteration to be non-uniform circumferentially. A pre-determined range of gap424dimension tolerances are provided for. Moreover, the interaction of the magnetic fields of windings423and rotor418separately from the interaction of magnetic fields of winding425and rotor418facilitates separately modulating the flux and the radial and axial forces induced on rotor418via a forward portion of gap424and an aft portion of gap424. Separately controlling the forward and aft flux and radial and axial forces in this manner further facilitates decreasing a tendency of rotor418axis of rotation to radially shift away from axis of rotation414as well as facilitates mitigating axial thrust induced on rotor418.

Wind turbine400also includes a support bearing426that provides radial support of hub/rotor404, generator rotor418, and blades406. In the embodiment ofFIG. 4, bearing426is, but is not limited to, either a roller ball bearing and/or a journal bearing. Bearing426may also be configured to provided axial, or thrust, support. Wind turbine400further includes a clearance gap control system (not shown inFIG. 4) that is substantially similar to system200(shown inFIG. 2) with the exception of the positioning of a plurality of clearance gap measurement assemblies428. Assemblies428are positioned on an axially forward-most and aft-most surface of stator420. In the embodiment ofFIG. 4, assemblies428are substantially similar to assemblies218,220, and222(shown inFIG. 2).

During operation, rotation of hub/rotor404rotatably drives generator rotor418and rotor418rotation facilitates generator416production of electrical power. For example, in the event that some wind forces are such that blades406tend to be positioned to a deflected position, torsional loads and subsequent stresses may be induced within blades406. These stresses are transferred from blades406to hub/rotor404via load transfer regions412. The transferred stresses within hub/rotor404are transferred to rotor418and bearing426. In some instances, stresses transferred into hub/rotor404may deflect hub/rotor404and rotor418such that hub/rotor404and rotor418radial positions may be within the tolerances of bearing426such that gap424dimension is altered and predetermined radial and axial gap424dimension tolerances are approached. Assemblies428monitor gap424dimensions of and/or the magnetic flux of gap424and transmit the associated clearance gap radial dimension signals, or gap dimension signals, and/or clearance gap magnetic flux signals, or flux signals, (neither shown inFIG. 4) to the control system (not shown inFIG. 4).

The control system operates in a PWM manner to control the frequency, the phase angle and the amplitude of the voltage and current (and, therefore, power) signals generated in, and transmitted from, windings423and425. Specifically, in the event that rotor418is deflected such that gap424dimension is not uniform within generator416, the associated radial air gap flux in gap424is adjusted. The overall effect is to adjust the attractive forces induced within generator416between rotor418and windings423and425to reposition rotor418such that gap424dimensions measured by assemblies428are substantially similar. In this manner, generator416in conjunction with the associated clearance gap control system, cooperates with bearing426to provide radial support and axial positioning of rotor418and hub/rotor404.

FIG. 5is a schematic view of another exemplary wind turbine generator500into which clearance gap control system200(shown inFIG. 2) may be embedded. Wind turbine generator500is a horizontal axis wind turbine. Alternatively, wind turbine500may be a vertical axis wind turbine. Wind turbine500includes a support frame502that is fixedly coupled to a tower501extending from a supporting surface (not shown inFIG. 5) via a yaw bearing503. Wind turbine500also includes a rotatable hub/rotor504and a plurality of rotor blades506coupled to hub/rotor504. In this alternative embodiment, wind turbine500has three rotor blades506(only two shown inFIG. 5) coupled to hub/rotor504. However, wind turbine500may have any number of rotor blades506, whether such number is described and/or illustrated hereon. In the embodiment ofFIG. 5, support frame502includes a substantially annular cavity508. The height of the tower is selected based upon factors and conditions known in the art.

Blades506are positioned about hub/rotor504to facilitate rotating hub/rotor504to transfer kinetic energy from the wind into usable mechanical energy, and subsequently, electrical energy. Blades506are mated to hub/rotor504by coupling a blade root portion510to hub/rotor504at a plurality of load transfer regions512. Load transfer regions512have a hub/rotor load transfer region and a blade load transfer region (both not shown inFIG. 5). Loads induced in blades506are transferred to hub/rotor504via load transfer regions512.

In the embodiment ofFIG. 5, blades506may each have any suitable length, whether such length is described and/or illustrated hereon. As the wind strikes blades506, hub/rotor504is rotated about rotation axis514. As blades506are rotated and subjected to centrifugal forces, blades506are subjected to various bending moments and other operational stresses. As such, blades506may deflect and/or rotate from a neutral, or non-deflected, position to a deflected position and associated stresses, or loads, may be induced in blades506. Moreover, a pitch angle (not shown inFIG. 5) of blades506, i.e., the angle that determines blades506perspective with respect to the direction of the wind, may be changed by a pitch adjustment mechanism (not shown inFIG. 5) to facilitate increasing or decreasing blade506speed by adjusting the surface area of blades506exposed to the wind force vectors. In the embodiment ofFIG. 5, the pitches of blades506are controlled individually. Alternatively, blades506pitch may be controlled as a group.

In some configurations, one or more microcontrollers in a control system (not shown inFIG. 5) are used for overall system monitoring and control such as, but not limited to pitch and rotor speed regulation, yaw drive and yaw brake application, and fault monitoring. Alternatively, distributed or centralized control architectures are used in alternate embodiments of wind turbine500.

In this alternative embodiment, various components of wind turbine500are housed within support frame cavity508. Hub/rotor504is rotatably coupled to an electric generator516. Also, in this alternative embodiment, generator516is a V-shaped, synchronous, three-phase, permanent magnet generator516that includes a rotor518and a stator520. Alternatively, generator516is any type of generator including, but not limited to, salient pole generators, double-sided stator generators, and/or doubly-fed induction generators. In the embodiment ofFIG. 5, rotor518is an extension of hub/rotor504. Alternatively, rotor504may be a separate component rotatingly coupled to hub/rotor504using methods known in the art. In the embodiment ofFIG. 5, rotor518includes a plurality of permanent magnets522that are coupled to rotor518. Alternatively, rotor518may be a wound rotor wherein the associated windings (neither shown inFIG. 5) are separately-excited. Rotor518and stator520are positioned such that a clearance gap524(sometimes referred to as an air gap524) is defined between stator520and rotor518with a pre-determined clearance gap radial dimension (not shown inFIG. 5) that is substantially circumferentially similar about rotor518and stator520while rotor518is stationary. Permanent magnets522with pre-determined polarities are positioned to generate a magnetic field (not shown inFIG. 5) around an inner periphery of rotor518with a pre-determined number of poles and a pre-determined magnetic strength.

In the exemplary embodiment, stator520includes a plurality of three-phase forward stator windings523and a plurality of three-phase aft stator windings525. Windings523and525are substantially similar and are substantially electrically isolated from each other. Moreover, windings524and525are each electrically coupled to converters232,234and236(all three shown inFIG. 2) such that each of windings523and525may be controlled independently. Alternatively, windings523and525are manufactured as a single set of three-phase windings as is known in the art. The “v-shaped” configuration of generator516facilitates operation of wind turbine generator500as discussed further below.

Gap524facilitates magnetic coupling of permanent magnets522and windings523and525to generate pre-determined voltages within windings523and525at a pre-determined frequency that is determined by rotor518rotational speed as rotor518is rotated about stator520. The generated voltages within windings523and525subsequently generate pre-determined electric currents within windings523and525. The electric currents generated within windings523and525subsequently generate a plurality of stator magnetic fields (not shown). As the magnetic field (not shown) generated via rotor518rotates, the magnetic field of rotor518interacts with the magnetic fields of windings523and525through gap524. The interaction of the magnetic fields induces a torque on rotor518. Loads induced within rotor518by asymmetric and/or transient loads introduced via blades506or other drive components may shift an axis of rotation of rotor518radially away from nominal wind turbine centerline axis of rotation514such that the clearance gap524dimension is reduced and/or altered to be non-uniform circumferentially within generator516. The radial and axial forces induced on rotor518by the interaction of the magnetic fields are proportional to the strength and position of the magnetic flux components within gap524. Such radial and axial forces may be substantially uniform about gap524, or alternatively, may be non-symmetrical with respect to windings523and525. As the flux at any point within gap524increases, the associated radial and axial forces induced on rotor518in the vicinity of such point within gap524increases, and the attractive force between rotor518and stator520is increased in the vicinity of such point. Similarly, as the flux at any point in gap524decreases, the radial and axial forces induced on rotor518in the vicinity of such point within gap524decreases, and the attractive force between rotor518and stator520is decreased in the vicinity of such point. Therefore, modulating the flux and the radial and axial forces induced on rotor518via the interaction of the stator and rotor magnetic fields may facilitate decreasing a tendency of rotor518axis of rotation to radially shift away from axis of rotation514and to facilitate mitigating gap524dimension reduction and/or alteration to be non-uniform circumferentially. A pre-determined range of gap524dimension tolerances are provided for. Moreover, the interaction of the magnetic fields of windings523and rotor518separately from the interaction of magnetic fields of winding525and rotor518facilitates separately modulating the flux and the radial and axial forces induced on rotor518via a forward portion of gap524and an aft portion of gap524. Separately controlling the forward and aft flux and radial and axial forces in this manner further facilitates decreasing a tendency of rotor518axis of rotation to radially shift away from axis of rotation514as well as facilitates mitigating axial thrust induced on rotor518.

Wind turbine500also includes a support bearing526that is coupled to a support frame extension527via methods that include, but are not limited to, friction fit. Bearing526extends toward and is coupled to hub/rotor504via methods that include, but are not limited to, friction fit. Bearing526provides radial support of hub/rotor505, generator rotor518, and blades506. In the embodiment ofFIG. 5, bearing526is, but is not limited to, either a roller ball bearing and/or a journal bearing. Bearing526may also be configured to provide axial, or thrust, support. Wind turbine500further includes a clearance gap control system (not shown inFIG. 5) that is substantially similar to system200(shown inFIG. 2) with the exception of the positioning of a plurality of clearance gap measurement assemblies528. Assemblies528are positioned on an axially forward-most and aft-most surface of rotor518. In this alternative embodiment, assemblies528are substantially similar to assemblies218,220, and222(shown inFIG. 2). Wind turbine500at least partially differs from wind turbine400in that bearing426(both shown inFIG. 4) may be configured to support greater load than bearing526. This is due to bearing526being configured as a “start-up” bearing that supports rotor518, hub/rotor504and blades506during periods that generator516is not in service. In the embodiment ofFIG. 5, generator516, in conjunction with an associated clearance gap control system, cooperates with bearing526to provide radial support of rotor518and hub/rotor504.

During periods of operation wherein generator516is not in service, bearing526provides support of rotor518, hub/rotor504and blades506. During periods of operation wherein generator516is in service, rotation of hub/rotor504rotatably drives generator rotor518and rotor518rotation facilitates generator516production of electrical power. As the electrical load on generator516is increased, the load carrying capabilities of generator516are increased and the relative proportion of load on bearing526is decreased. In the event that some wind forces are such that blades506tend to be positioned to a deflected position, torsional loads and subsequent stresses may be induced within blades506. These stresses are transferred from blades506to hub/rotor504via load transfer regions512. The transferred stresses within hub/rotor504are transferred to rotor518and bearing526. In some instances, stresses transferred into hub/rotor504may deflect hub/rotor504and rotor518such that hub/rotor504and rotor518radial positions may be within the tolerances of bearing526such that gap524dimension is altered and predetermined gap524dimension tolerances are approached. Assemblies528monitor gap524dimensions of and/or the magnetic flux of gap524and transmit the associated clearance gap radial dimension signals, or gap dimension signals, and/or clearance gap magnetic flux signals, or flux signals, (neither shown inFIG. 5) to the control system (not shown inFIG. 5).

The control system operates in a PWM manner to control the frequency, the phase angle and the amplitude of the voltage and current (and, therefore, power) signals generated in, and transmitted from, windings523and525. Specifically, in the event that rotor518is deflected such that gap524dimension is not uniform within generator516, the associated radial air gap flux in gap524is adjusted. The overall effect is to adjust the attractive forces induced within generator516between rotor518and windings523and525to reposition rotor518such that gap524dimensions measured by assemblies528are substantially similar. In this manner, generator516in conjunction with the associated clearance gap control system, cooperates with bearing526to provide radial support and axial positioning of rotor518and hub/rotor504.

The methods and apparatus for a wind turbine generator control system described herein facilitate operation of a wind turbine generator. More specifically, the wind turbine generator clearance gap control system as described above facilitates an efficient and effective electrical generation and mechanical load transfer scheme. Also, the robust, clearance gap control system facilitates generator efficiency. Such control system also facilitates wind turbine generator reliability, and reduced maintenance costs and wind turbine generator outages.

Exemplary embodiments of wind turbine control systems as associated with wind turbine generators are described above in detail. The methods, apparatus and systems are not limited to the specific embodiments described herein nor to the specific illustrated wind turbine generators.