Stator controlled induction generators with short-circuited rotor

Abstract

A generator is connectable to a turbine for generating electric power or a motor. An electric power generator system or a motor comprises an asynchronous short-circuited rotor generator or motor comprising a stator, a rotor, and a transformer having a first winding and a second winding, the first winding having a first end and a second end. The stator and the transformer are connectable in series with an electric power distribution grid.

1 . An asynchronous short-circuited rotor generator for generating electric power wherein a stator is connected in series to a first end of a first winding of a transformer, and an electric power distribution grid is connected to the second end of the first winding of the transformer. 
   
   
       2 . An electric power generator system or motor comprising:
 a short-circuited rotor induction generator or motor comprising a stator and a rotor;   a transformer having a first winding and a second winding, said first winding having a first end and a second end; and   wherein said stator and said transformer are connectable in series with an electric power distribution grid.   
   
   
       3 - 12 . (canceled) 
   
   
       13 . A method of generating electrical power, said method comprising:
 generating electrical power using a short-circuited rotor induction 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.   
   
   
       14 . A method as in  claim 13 , and further comprising:
 connecting a first converter, a direct current link, and a second converter in series between said stator and a second winding of said transformer; and   regulating one of the current between said first converter and said stator, and the sum of the reactive power of said stator and the reactive power of said converter.   
   
   
       15 - 19 . (canceled) 
   
   
       20 . A system for controlling: a short-circuited rotor induction 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 one or more of the voltage of said stator independent of the voltage of said electric distribution grid, and the reactive power applied to said grid by said generator or motor. 
   
   
       21 . A system as in  claim 20  wherein said instructions further comprise instructions for comparing a voltage on a DC bus between said stator and said grid with a DC bus reference voltage to regulate the transfer of active power to said grid via said DC bus. 
   
   
       22 . A system as in  claim 20  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 aligned with the current of said grid. 
   
   
       23 . A system as in  claim 20  wherein said instructions further comprise instructions for comparing the total reactive power delivered to said grid with a total reactive power reference to determine a voltage component in the direction orthogonal with the current of said grid. 
   
   
       24 . A method of controlling a wind turbine generator connected to a grid, said turbine including a short-circuited rotor induction 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.   
   
   
       25 . A method as in  claim 24  wherein said voltage has a component oriented in the direction of the grid current, which component injects active power into said grid. 
   
   
       26 . A method as in clam  24  wherein said voltage has a component in quadrature with the grid current, which component injects reactive power into said grid. 
   
   
       27 . A method as in  claim 24  wherein said generating comprises comparing the total reactive power applied to said grid to a reference reactive power to produce a reactive power error signal, and using said reactive power error signal to determine a value of said injected voltage orthogonal to the current of said grid. 
   
   
       28 . A method as in  claim 24  wherein said generating comprises comparing the voltage applied to said stator to a reference stator voltage to produce a stator voltage error signal. 
   
   
       29 . A method as in  claim 28  wherein said generating further comprises using said stator voltage error signal to determine the value of said injected voltage in a direction aligned with the grid current. 
   
   
       30 . A method as in  claim 24  wherein said generator system further includes a first converter, a DC link, and a second converter connected between said stator 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. 
   
   
       31 . A method as in  claim 29  wherein said generating further comprises using said DC error signal to determine a component of the current between said first converter and said stator in a direction aligned with the stator voltage. 
   
   
       32 . A method of operating a short-circuited rotor induction 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. 
   
   
       33 . A method as in  claim 32  wherein said stator voltage is held constant. 
   
   
       34 . A method as in  claim 32  wherein said controlling the voltage applied to said stator comprises injecting a voltage between said stator and said grid. 
   
   
       35 . A method as in  claim 34  wherein said injecting is performed by applying said voltage via a transformer connected between said stator and said grid. 
   
   
       36 . A method as in  claim 34  wherein said controlling comprises comparing the voltage applied to said stator to a reference stator voltage to produce a stator voltage error signal. 
   
   
       37 . A method as in  claim 36  wherein said generating further comprises using said stator voltage error signal to determine the value of said injected voltage in a direction aligned with the grid current. 
   
   
       38 . A method as in  claim 34  wherein said generating further comprises comparing the total reactive power applied to said grid to a reference reactive power to produce a reactive power error signal. 
   
   
       39 . A method as in  claim 38  wherein said generating further comprises using said reactive power error signal to determine a value of said injected voltage orthogonal to the current of said grid.