Doubly-controlled asynchronous generator

Abstract

An electric power generator system or a motor comprising a doubly-fed asynchronous generator or motor comprising a stator and a rotor; a transformer having a first winding and a second winding, the first winding having a first end and a second end; and wherein the stator and the transformer are connectable in series with an electric power distribution grid.

1 - 11 . (canceled) 
     
     
         12 . A method of generating electrical power, said method comprising:
 generating electrical power using a doubly-fed asynchronous generator comprising a stator and a rotor;   connecting a first winding of a transformer in series between said stator and an electric power distribution grid; and   flowing power between said stator and said electric power distribution grid via said transformer.   
     
     
         13 . A method as in  claim 12 , and further comprising regulating the current of said stator to govern the active and reactive power delivered to the electric distribution grid. 
     
     
         14 . A method according to  claim 12 , and further comprising regulating the electromagnetic torque of said generator and the reactive power delivered by said stator to said electric power distribution grid. 
     
     
         15 . A method according to  claim 12 , and further comprising flowing power between said rotor and said electric power distribution grid via a second winding of said transformer. 
     
     
         16 . A method according to  claim 15  wherein said flowing power between said rotor and said grid further comprises flowing said power through a direct current bus between a first converter and a second converter located between said transformer and said rotor. 
     
     
         17 . A method according to  claim 16  wherein said DC bus includes a first node and a second node, and wherein a capacitor is connected between said first node and said second node, and said method further comprises regulating the voltage applied to said capacitor based on a predetermined reference value (V* dc ) so that power is dynamically transferred from said rotor to said distribution grid. 
     
     
         18 . A method according to  claim 17 , and further comprising flowing power bidirectionally between said first and second converters. 
     
     
         19 . A system for controlling a doubly-fed electrical power generator providing electrical power to an electric distribution grid or a motor connected to said grid, said generator or motor having a stator and a rotor, said system comprising a media readable by a processing unit, said media containing instructions for directing said processing unit to regulate the voltage of said stator independent of the voltage of said electric distribution grid. 
     
     
         20 . A system as in  claim 19  wherein said instructions further comprise instructions for comparing a voltage on a DC bus between said rotor and said grid with a DC bus reference voltage to determine a voltage component in the direction of the current of said stator. 
     
     
         21 . A system as in  claim 19  wherein said instructions further comprise instructions for comparing the voltage on said stator with a stator reference voltage to determine a voltage component in the direction orthogonal to the current of said stator. 
     
     
         22 . A method of controlling a doubly-fed wind turbine generator connected to a grid, said turbine including a generator system having a stator and a rotor, said method comprising:
 generating a voltage; and   injecting said voltage in series between said stator and said grid.   
     
     
         23 . A method as in  claim 22  wherein said voltage has a component oriented in the direction of the stator current, which component injects power from said rotor into said grid. 
     
     
         24 . A method as in  claim 22  wherein said voltage has a component in quadrature with the stator current to control the magnitude of the stator voltage. 
     
     
         25 . A method as in  claim 24  wherein said magnitude is maintained constant. 
     
     
         26 . A method as in  claim 22  wherein said generating comprises comparing the voltage applied to said stator to a reference stator voltage to produce a stator voltage error signal. 
     
     
         27 . A method as in  claim 26  wherein said generating further comprises using said stator voltage error signal to determine the value of said voltage in a direction orthogonal to the stator current. 
     
     
         28 . A method as in  claim 22  wherein said generator system further includes a DC link between said rotor and said grid, and wherein said generating comprises comparing a measured DC voltage of said DC link to a reference DC voltage to provide a DC error signal. 
     
     
         29 . A method as in  claim 28  wherein said generating further comprises using said DC error signal to determine the value of said voltage in the direction of the stator current. 
     
     
         30 . A method of operating an asynchronous doubly-fed power generator or motor connected to a power distribution grid, said generator or motor comprising a rotor and a stator, said method comprising controlling the voltage applied to said stator independent of the voltage of said grid. 
     
     
         31 . A method as in  claim 30  wherein said stator voltage is held constant. 
     
     
         32 . A method as in  claim 30  wherein said controlling the voltage applied to said stator comprises injecting a voltage between said stator and said grid. 
     
     
         33 . A method as in  claim 32  wherein said injecting is performed by applying said voltage via a transformer connected between said stator and said grid. 
     
     
         34 . A method as in  claim 30  wherein said controlling comprises comparing the voltage applied to said stator to a reference stator voltage to produce a stator voltage error signal. 
     
     
         35 . A method as in  claim 34  wherein said controlling further comprises using said stator voltage error signal to determine the value of said voltage in a direction orthogonal to the stator current. 
     
     
         36 . A method as in  claim 30  wherein said generator system further includes a DC link between said rotor and said grid, and wherein said controlling comprises comparing a measured DC voltage of said DC link to a reference DC voltage to provide a DC error signal. 
     
     
         37 . A method as in  claim 36  wherein said controlling further comprises using said DC error signal to determine the value of said voltage in the direction of the stator current.