Variable speed wind turbine
DC CAFCFirst Claim
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1. A variable speed wind turbine comprising:
- a turbine rotor including at least one blade mounted to a rotatable shaft;
a multiphase generator having a stator and a rotor coupled to the turbine shaft for rotation therewith;
a power converter including active switches operable for controlling stator electrical quantities for each phase of the generator;
torque command means associated with turbine parameter sensors for defining a torque reference signal; and
generator controller means coupled to the power converter for controlling the active switches including field orientation means responsive to the torque reference signal for defining a desired quadrature axis current in field coordinates, and switch control means for controlling the active switches to produce stator electrical quantities that correspond to the desired quadrature axis current.
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Abstract
A variable speed wind turbine is disclosed comprising a turbine rotor that drives an AC induction generator, a power converter that converts the generator output to fixed-frequency AC power, a generator controller, and an inverter controller. The generator controller uses field orientation to regulate either stator currents or voltages to control the torque reacted by the generator. The inverter controller regulates the output currents to supply multi-phase AC power having leading or lagging currents at an angle specified by a power factor control signal.
427 Citations
138 Claims
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1. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase generator having a stator and a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator electrical quantities for each phase of the generator; torque command means associated with turbine parameter sensors for defining a torque reference signal; and generator controller means coupled to the power converter for controlling the active switches including field orientation means responsive to the torque reference signal for defining a desired quadrature axis current in field coordinates, and switch control means for controlling the active switches to produce stator electrical quantities that correspond to the desired quadrature axis current. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith, wherein the generator includes a stator power tap for each phase; a power converter including a rectifier, inverter, and DC voltage link coupled between the rectifier and inverter, wherein the rectifier includes a pair of active switches for each phase of the generator coupled between the DC voltage link and a stator power tap and operable for switching stator currents therebetween to establish a rotating flux field in the generator rotor, and wherein the inverter includes a pair of active switches for each phase of output power coupled between the DC voltage link and an output tap and operable for switching inverter currents therebetween; generator controller means coupled to the rectifier and responsive to a torque reference signal and a rotor speed signal for controlling the rectifier switches to regulate stator electrical quantities, wherein the generator controller means includes field orientation means for defining the magnitude of the rotor flux field as a function of a desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and for converting the torque reference and rotor speed signals into a desired quadrature axis current in field coordinates oriented normal to a rotor flux vector, and further includes modulation means for controlling the rectifier switches to produce stator electrical quantities that correspond to the desired quadrature and direct axis currents; inverter controller means coupled to the inverter for controlling the inverter switches to regulate the inverter currents; rotor speed sensor means for monitoring the speed of the generator rotor and for defining the rotor speed signal in accordance therewith; and torque command means for defining a torque reference signal and supplying it to the generator controller. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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25. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator electrical quantities for each phase of the generator to establish a rotating flux field in the generator rotor; stator current sensors operable for sensing stator currents; torque monitor means responsive to sensed stator currents for determining a measure of generator torque; pitch sensing means for sensing the pitch of the turbine blade; rotor speed sensor means for sensing the speed of the generator rotor; torque command means responsive to the generator torque, blade pitch, and rotor speed for defining a torque reference signal; and generator controller means coupled to the active switches for controlling stator electrical quantities, wherein the generator controller means includes processor means responsive to the torque reference signal and the rotor speed for defining a flux-producing desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and a torque-producing desired quadrature axis current in field coordinates oriented normal to the rotor flux field, the processor means including means for periodically determining a desired rotor flux angle as a function of the rotor speed and desired quadrature and direct axis currents, the processor means including means for converting the desired direct and quadrature axis currents from field coordinates into stator coordinates using the desired rotor flux angle to define desired stator electrical quantities, and includes modulation means for controlling the active switches to produce stator electrical quantities that correspond to the desired stator electrical quantities.
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26. A method for controlling torque in a wind turbine having a generator coupled to a power converter with active switches, wherein the active switches establish a rotating flux field in the generator rotor, the method comprising of the steps of:
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defining a torque reference signal indicative of a desired generator torque; converting the torque reference signal into a desired quadrature axis current representing torque in rotating field coordinates normal to the rotor flux field; and controlling the active switches of the power converter to produce stator electrical quantities that correspond to the desired quadrature axis current. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34)
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35. A method for controlling torque in a wind turbine having an induction generator coupled to an active rectifier, wherein the active rectifier establishes a rotating flux field in the generator rotor, the method comprising of the steps of:
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defining a torque reference signal indicative of a desired generator torque; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; sensing the rotational speed of the generator rotor; defining a rotor flux angle indicative of the instantaneous position of the rotor flux field; converting the desired quadrature and direct axis currents into desired stator electrical quantities in a stationary stator coordinate system using the rotor flux angle; and supplying pulse width modulation signals to switches of the active rectifier to produce stator electrical quantities that correspond to the desired stator electrical quantities. - View Dependent Claims (36, 37, 38, 39)
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40. A method for controlling torque in a wind turbine having an induction generator coupled to an active rectifier, wherein the active rectifier establishes a rotating flux field in the generator rotor, the method comprising of the steps of:
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sensing stator currents; determining a measure of generator torque by converting the sensed stator currents into a quadrature axis current normal to the rotor flux field; sensing the pitch angle of the turbine blade; sensing the rotational speed of the generator rotor; defining a torque reference signal indicative of a desired generator torque in response to the sensed generator torque, pitch angle, and rotational speed; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; periodically defining a rotor flux angle indicative of the desired instantaneous position of the rotor flux field as a function of the rotor speed and the desired quadrature and direct axis currents; periodically converting the desired quadrature and direct axis currents into desired stator electrical quantities using the rotor flux angle; and periodically supplying pulse width modulation signals to the active rectifier to produce stator electrical quantities that correspond to the desired stator electrical quantities.
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41. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase generator having a stator and a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator currents for each phase of the generator; torque command means associated with turbine parameter sensors for defining a torque reference signal; and generator controller means coupled to the power converter for controlling the active switches including field orientation means responsive to the torque reference signal for defining a desired quadrature axis current in field coordinates, and switch control means for controlling the active switches to produce stator currents that correspond to the desired quadrature axis current. - View Dependent Claims (42, 43, 44)
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45. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith, wherein the generator includes a stator power tap for each phase; a power converter including a rectifier, inverter, and DC voltage link coupled between the rectifier and inverter, wherein the rectifier includes a pair of active switches for each phase of the generator coupled between the DC voltage link and a stator power tap and operable for switching stator currents therebetween to establish a rotating flux field in the generator rotor, and wherein the inverter includes a pair of active switches for each phase of output power coupled between the DC voltage link and an output tap and operable for switching inverter currents therebetween; generator controller means coupled to the rectifier and responsive to a torque reference signal and a rotor speed signal for controlling the rectifier switches to regulate stator currents, wherein the generator controller means includes field orientation means for defining the magnitude of the rotor flux field as a function of a desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and for converting the torque reference and rotor speed signals into a desired quadrature axis current in field coordinates oriented normal to a rotor flux vector, and further includes modulation means for controlling the rectifier switches to produce stator currents that correspond to the desired quadrature and direct axis currents; inverter controller means coupled to the inverter for controlling the inverter switches to regulate the inverter currents; rotor speed sensor means for monitoring the speed of the generator rotor and for defining the rotor speed signal in accordance therewith; and torque command means for defining a torque reference signal and supplying it to the generator controller. - View Dependent Claims (46, 47, 48, 49, 50, 51)
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52. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator currents for each phase of the generator to establish a rotating flux field in the generator rotor; stator current sensors operable for sensing stator currents; torque monitor means responsive to sensed stator currents for determining a measure of generator torque; pitch sensing means for sensing the pitch of the turbine blade; rotor speed sensor means for sensing the speed of the generator rotor; torque command means responsive to the generator torque, blade pitch, and rotor speed for defining a torque reference signal; and generator controller means coupled to the active switches for controlling stator currents, wherein the generator controller means includes processor means responsive to the torque reference signal and the rotor speed for defining a flux-producing desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and a torque-producing desired quadrature axis current in field coordinates oriented normal to the rotor flux field, the processor means including means for periodically determining an instantaneous rotor flux angle and converting the desired direct and quadrature axis currents from field coordinates into stator coordinates to define desired stator currents, and includes modulation means for controlling the active switches to produce stator currents or voltages that correspond to the desired stator currents.
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53. A method for controlling torque in a wind turbine having a generator coupled to a power converter with active switches, wherein the active switches establish a rotating flux field in the generator rotor, the method comprising of the steps of:
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defining a torque reference signal indicative of a desired generator torque; converting the torque reference signal into a desired quadrature axis current representing torque in rotating field coordinates normal to the rotor flux field; and controlling the active switches of the power converter to produce stator currents that correspond to the desired quadrature axis current. - View Dependent Claims (54, 55)
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56. A method for controlling torque in a wind turbine having an induction generator coupled to an active rectifier, wherein the active rectifier establishes a rotating flux field in the generator rotor, the method comprising of the steps of:
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defining a torque reference signal indicative of a desired generator torque; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; sensing the rotational speed of the generator rotor; defining a rotor flux angle indicative of the instantaneous position of the rotor flux field; converting the desired quadrature and direct axis currents into desired stator currents in a stationary stator coordinate system using the rotor flux angle; and supplying pulse width modulation signals to the switches of the active rectifier to produce stator currents that correspond to the desired stator currents. - View Dependent Claims (57, 58, 59, 60, 61)
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62. A method for controlling torque in a wind turbine having an induction generator coupled to an active rectifier, wherein the active rectifier establishes a rotating flux field in the generator rotor, the method comprising of the steps of:
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sensing stator currents; determining a measure of generator torque by converting the sensed stator currents into a quadrature axis current normal to the rotor flux field; sensing the pitch angle of the turbine blade; sensing the rotational speed of the generator rotor; defining a torque reference signal indicative of a desired generator torque in response to the sensed generator torque, pitch angle, and rotational speed; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; periodically defining a rotor flux angle indicative of the instantaneous position of the rotor flux field; periodically converting the desired quadrature and direct axis currents into desired stator currents; and periodically supplying pulse width modulation signals to the active rectifier to produce stator currents that correspond to the desired stator currents.
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63. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase generator having a stator and a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator voltage for each phase of the generator; torque command means associated with turbine parameter sensors for defining a torque reference signal; and generator controller means coupled to the power converter for controlling the active switches including field orientation means responsive to the torque reference signal for defining a desired quadrature axis current in field coordinates, and switch control means for controlling the active switches to produce stator voltages that correspond to the desired quadrature axis current. - View Dependent Claims (64, 65, 66)
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67. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith, wherein the generator includes a stator power tap for each phase; a power converter including a rectifier, inverter, and DC voltage link coupled between the rectifier and inverter, wherein the rectifier includes a pair of active switches for each phase of the generator coupled between the DC voltage link and a stator power tap and operable for switching stator currents therebetween to establish a rotating flux field in the generator rotor, and wherein the inverter includes a pair of active switches for each phase of output power coupled between the DC voltage link and an output tap and operable for switching inverter currents therebetween; generator controller means coupled to the rectifier and responsive to a torque reference signal and a rotor speed signal for controlling the rectifier switches to regulate stator voltages, wherein the generator controller means includes field orientation means for defining the magnitude of the rotor flux field as a function of a desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and for converting the torque reference and rotor speed signals into a desired quadrature axis current in field coordinates oriented normal to a rotor flux vector, and further includes modulation means for controlling the rectifier switches to produce stator voltages that correspond to the desired quadrature and direct axis currents; inverter controller means coupled to the inverter for controlling the inverter switches to regulate the inverter currents; rotor speed sensor means for monitoring the speed of the generator rotor and for defining the rotor speed signal in accordance therewith; and torque command means for defining a torque reference signal and supplying it to the generator controller. - View Dependent Claims (68, 69, 70)
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71. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator voltages for each phase of the generator to establish a rotating flux field in the generator rotor; stator current sensors operable for sensing stator currents; torque monitor mean responsive to sensed stator currents for determining a measure of generator torque; pitch sensing means for sensing the pitch of the turbine blade; rotor speed sensor means for sensing the speed of the generator rotor; torque command means responsive to the generator torque, blade pitch, and rotor speed for defining a torque reference signal; and generator controller means coupled to the active switches for controlling stator voltages, wherein the generator controller means includes processor means responsive to the torque reference signal and the rotor speed for defining a flux-producing desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and a torque-producing desired quadrature axis current in field coordinates oriented normal to the rotor flux field, the processor means including means for periodically determining an instantaneous rotor flux angle and converting the desired direct and quadrature axis currents from field coordinates into stator coordinates to define desired stator voltages, and includes modulation means for controlling the active switches to produce stator voltages that correspond to the desired stator voltages.
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72. A method for controlling torque in a wind turbine having a generator coupled to a power converter with active switches, wherein the active switches establish a rotating flux field in the generator rotor, the method comprising of the steps of:
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defining a torque reference signal indicative of a desired generator torque; converting the torque reference signal into a desired quadrature axis current representing torque in rotating field coordinates normal to the rotor flux field; and controlling the active switches of the power converter to produce stator voltages that correspond to the desired quadrature axis current. - View Dependent Claims (73)
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74. A method for controlling torque in a wind turbine having an induction generator coupled to an active rectifier, wherein the active rectifier establishes a rotating flux field in the generator rotor, the method comprising of the steps of:
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defining a torque reference signal indicative of a desired generator torque; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; sensing the rotational speed of the generator rotor; defining a rotor flux angle indicative of the instantaneous position of the rotor flux field; converting the desired quadrature and direct axis currents into desired stator voltages in a stationary stator coordinate system using the rotor flux angle; and supplying pulse width modulation signals to the switches of the active rectifier to produce stator voltages that correspond to the desired stator voltages. - View Dependent Claims (75, 76)
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77. A method for controlling torque in a wind turbine having an induction generator coupled to an active rectifier, wherein the active rectifier establishes a rotating flux field in the generator rotor, the method comprising of the steps of:
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sensing stator currents; sensing the generator torque by converting the sensed stator currents into a quadrature axis current normal to the rotor flux field; sensing the pitch angle of the turbine blade; sensing the rotational speed of the generator rotor; defining a torque reference signal indicative of a desired generator torque in response to the sensed generator torque, pitch angle, and rotational speed; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; instantaneous position of the rotor flux field; periodically converting the desired quadrature and direct axis currents into desired stator voltages; and periodically supplying pulse width modulation signals to the active rectifier to produce stator currents that correspond to the desired stator voltages.
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78. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase generator having a stator and a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator currents for each phase of the generator; torque command means associated with turbine parameter sensors for defining a torque reference signal; and generator controller means coupled to the power converter for controlling the active switches to regulate stator currents, wherein the generator controller includes means for regulating the generator torque by controlling the stator currents at a low speed of rotation of the generator and by controlling the stator voltages at a higher speed of rotation of the generator. - View Dependent Claims (79, 80, 81, 82, 83)
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84. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith, wherein the generator includes a stator power tap for each phase; rotor sensor means for sensing the rotational speed of the generator rotor; a power converter including active switches operable for controlling stator currents for each phase of the generator and for establishing a rotating flux field in the generator rotor; torque command means associated with turbine parameter sensors for defining a torque reference signal; and generator controller means coupled to the power converter for controlling the magnitude and frequency of stator electrical quantities, wherein the generator controller includes means responsive to the rotor speed for regulating the generator torque by controlling the stator currents at a low speed of rotation of the generator and by controlling the stator voltages at a higher speed of rotation of the generator, the generator controller means further includes field orientation means for defining the magnitude of the rotor flux field as a function of a desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and for converting the torque reference signal and rotor speed into a desired quadrature axis current in field coordinates oriented normal to a rotor flux vector, and further includes modulation means for controlling the active switches to produce stator electrical quantities that correspond to the desired quadrature and direct axis currents. - View Dependent Claims (85, 86, 87, 88)
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89. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator electrical quantities for each phase of the generator to establish a rotating flux field in the generator rotor; stator current sensors operable for sensing stator currents; torque monitor means responsive to sensed stator currents for determining a measure of generator torque; pitch sensing means for sensing the pitch of the turbine blade; rotor speed sensor means for sensing the speed of the generator rotor; torque command means responsive to the generator torque, blade pitch, and rotor speed for defining a torque reference signal; and generator controller means coupled to the active switches for controlling stator currents when the generator is operating at low rotational speeds and controlling stator voltages when the generator is operating at higher rotational speeds, wherein the generator controller means includes processor means responsive to the torque reference signal and the rotor speed for defining a flux-producing desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and a torque-producing desired quadrature axis current in field coordinates oriented normal to the rotor flux field, the processor means including means for periodically determining an instantaneous rotor flux angle and converting the desired direct and quadrature axis currents from field coordinates into stator coordinates to define desired stator currents or voltages, and includes modulation means for controlling the active switches to produce stator currents or voltages that correspond to the desired stator currents or voltages.
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90. A method for controlling torque in a wind turbine having a generator coupled to an active rectifier, wherein the generator includes a stator and a rotor, the method comprising of the steps of:
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during low speed operation of the generator, controlling the orientation of a rotor flux field with respect to the rotor by switching the active rectifier to regulate currents in the stator; determining when the generator commences operation at a higher speed above the low speed; during the higher speed operation of the generator, controlling the orientation of the rotor flux field with respect to the rotor by switching the active rectifier to regulate voltages in the stator. - View Dependent Claims (91, 92, 93)
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94. A method for controlling torque in a wind turbine having an induction generator coupled to an active rectifier, wherein the generator includes a stator and a rotor, the method comprising of the steps of:
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defining a torque reference signal indicative of a desired generator torque; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; sensing the rotational speed of the generator rotor; defining a rotor flux angle indicative of the instantaneous position of the rotor flux field; during low speed operation of the generator, converting the desired quadrature and direct axis currents into desired stator currents and controlling the active rectifier to produce stator currents that correspond to the desired stator currents; determining when the generator commences operation at a higher speed above the low speed as a function of rotor speed; and during the higher speed operation of the generator, converting the desired quadrature and direct axis currents into desired stator voltages and controlling the active rectifier to produce stator voltages that correspond to the desired stator voltages. - View Dependent Claims (95, 96, 97)
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98. A method for controlling torque in a wind turbine having an induction generator coupled to an active rectifier, wherein the active rectifier establishes a rotating flux field in the generator rotor, the method comprising of the steps of:
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sensing stator currents; sensing the generator torque by converting the sensed stator currents into a quadrature axis current normal to the rotor flux field; sensing the pitch angle of the turbine blade; sensing the rotational speed of the generator rotor; defining a torque reference signal indicative of a desired generator torque in response to the sensed generator torque, pitch angle, and rotational speed; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; periodically defining a rotor flux angle indicative of the instantaneous position of the rotor flux field; periodically converting the desired quadrature and direct axis currents into desired stator currents when the generator is operating at low rotational speeds and into desired stator voltages when the generator is operating at higher rotational speeds; and periodically supplying pulse width modulation signals to the active rectifier to produce stator currents that correspond to the desired stator currents at the low rotational speeds and to produce stator voltages that correspond to the desired stator voltages at the higher rotational speeds.
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99. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a stator and a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator currents for each phase of the generator; torque command means associated with turbine parameter sensors for defining a torque reference signal; means coupled to the power converter for sensing stator currents; and generator controller means coupled to the power converter for controlling the stator currents, including means for defining desired stator currents, means for periodically determining a distortion index indicative of errors between desired and actual stator currents, and means for controlling the active switches to produce stator currents that minimize the distortion index. - View Dependent Claims (100, 101, 102, 103)
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104. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a stator and a rotor coupled to the turbine shaft for rotation therewith; power converter means coupled to the generator for converting the power generated by the generator to DC and then to a fixed frequency AC output, wherein the power converter means includes a bridge inverter having active switches and operable for controlling output currents; means for sensing output currents; and inverter controller means coupled to the bridge inverter for controlling the output currents, including means for defining desired output currents, means for periodically determining a distortion index indicative of errors between desired and actual output currents, and means for controlling the active switches to produce output currents that minimize the distortion index. - View Dependent Claims (105, 106, 107, 108)
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109. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a stator and a rotor coupled to the turbine shaft for rotation therewith; a power converter including active switches operable for controlling stator currents for each phase of the generator and for establishing a rotating flux field in the generator rotor; rotor speed sensor means for monitoring the speed of the generator rotor and for defining a rotor speed signal in accordance therewith; torque command means associated with turbine parameter sensors for defining a torque reference signal; means coupled to the power converter for sensing stator currents; and generator controller means coupled to the power converter for controlling the stator currents, including means for defining desired stator currents, means for periodically determining a distortion index indicative of errors between desired and actual stator currents, and means for controlling the active switches to produce stator currents that minimize the distortion index; and wherein the means for defining desired stator currents includes field orientation means for defining the magnitude of the rotor flux field as a function of a desired direct axis current in rotating field coordinates aligned with the direction of the rotor flux field and for converting the torque reference and rotor speed signals into a desired quadrature axis current in field coordinates oriented normal to a rotor flux vector, and including means for periodically determining an instantaneous rotor flux angle and converting the desired direct and quadrature axis currents from the field coordinates into stator coordinates to define the desired stator currents.
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110. A method for controlling stator currents in a wind turbine generator rotating at variable speeds to obtain torque control of the generator, wherein the stator currents are switched by an active rectifier, the method comprising the steps of:
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determining desired stator currents; sensing the actual stator currents; and switching the active rectifier to produce stator currents that minimize a distortion index indicating the magnitude of current errors between the actual and desired stator currents. - View Dependent Claims (111, 112, 113, 114)
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115. A method for controlling output currents generated by a wind turbine generator rotating at variable speeds, wherein the output currents are switched by a bridge inverter coupled to a DC voltage source powered by the generator, the method comprising the steps of:
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determining desired output currents; sensing the actual output currents; and switching the bridge inverter to produce output currents that minimize a distortion index indicating the magnitude of current errors between the actual and desired output currents. - View Dependent Claims (116, 117, 118, 119)
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120. A method for controlling stator currents in a wind turbine generator rotating at variable speeds to obtain torque control of the generator, wherein the stator currents are switched by an active rectifier that establishes a rotating flux field in the generator rotor, the method comprising the steps of:
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defining a torque reference signal indicative of a desired generator torque; determining a desired direct axis current representing rotor flux in a direction aligned with the rotor flux field in a rotating field coordinate system; converting the torque reference signal into a desired quadrature axis current representing rotor torque, wherein the quadrature axis current is normal to the rotor flux field in the field coordinate system; sensing the rotational speed of the generator rotor; sensing the actual stator currents; defining a rotor flux angle indicative of the instantaneous position of the rotor flux field; converting the desired quadrature and direct axis currents into desired stator currents in a stationary stator coordinate system using the rotor flux angle; determining a distortion index indicative of the magnitude of current errors between the actual and desired stator currents; and supplying pulse width modulation signals to the switches of the active rectifier to produce stator currents that minimize the distortion index
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121. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith; a power converter for converting variable frequency electricity generated by the generator into fixed frequency electricity, the power converter including an inverter for supplying output electricity, wherein the inverter has active switches; and inverter controller means coupled to the inverter and responsive to a power factor control signal for controlling the active switches to supply electricity at a desired angle between voltage and current. - View Dependent Claims (122, 123, 124, 125, 126, 127, 128, 129)
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130. A variable speed wind turbine comprising:
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a turbine rotor including at least one blade mounted to a rotatable shaft; a multiphase induction generator having a rotor coupled to the turbine shaft for rotation therewith; a power converter for converting variable frequency electricity generated by the generator into fixed frequency electricity, the power converter including a rectifier, inverter, and DC voltage link coupled between the rectifier and inverter, wherein the rectifier includes a pair of active switches for each phase of the generator coupled between the DC voltage link and a stator power tap and operable for switching stator current therebetween, and wherein the inverter includes a pair of active switches for each phase of output power coupled between the DC voltage link and an output tap and operable for switching inverter current therebetween; output current sensors operable for sensing output currents; and an inverter controller coupled to the inverter and responsive to a power factor control signal for controlling the inverter switches to supply output electricity at a desired angle between voltage and current, wherein the inverter controller includes means for creating a sinusoidal reference waveform synchronized with the output electricity, means responsive to the power factor control signal for defining a template waveform that is offset from the reference waveform by a desired phase angle, means responsive to the voltage of the DC voltage link for multiplying the template waveform by a control variable indicative of the inverter input voltage, means for converting the multiplied template waveform into the desired output currents, and means for controlling the active switches of the inverter to produce output currents that correspond to the desired output currents.
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131. A method for converting electricity generated by a variable speed wind turbine into fixed frequency output electricity, wherein the wind turbine includes a generator and means for supplying generated electricity to power converter that includes a switched inverter supplying the output electricity, the method comprising the steps of:
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forming a reference waveform; rotating the reference waveform by a selected power factor angle to yield a template waveform; using the template waveform to define desired output currents; and controlling the switched inverter to produce output currents corresponding to the desired output currents. - View Dependent Claims (132, 133, 134, 135, 136, 137)
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138. A method for converting electricity generated by a variable speed wind turbine into fixed frequency output electricity, wherein the wind turbine includes a generator and means for supplying generated electricity to power converter that includes a switched inverter supplying the output electricity, the method comprising the steps of:
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forming a sinusoidal reference waveform synchronized with the output electricity; rotating the reference waveform by a selected power factor angle to yield a template waveform; sensing the input voltage to the inverter and defining a current control signal in response thereto; multiplying the template waveform by the current control signal to define desired output currents; sensing the output currents; and controlling the switched inverter to produce output currents corresponding to the desired output currents by minimizing a distortion index indicative of the magnitude of current errors between the sensed and desired output currents.
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Specification