Controller for a wound rotor slip ring induction machine
AssigneesABB Automation Inc., ABB Industry Oy
InventorsKalyan P. Gokhale, Douglas W. Karraker, Samuli J. Heikkilä
Life of this patent
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Abstract
The direct torque control (DTC) principle is used to control the torque of a wound ring rotor slip induction machine, also known as a doubly fed or cascade machine, by utilizing a solid state inverter on the rotor side. In addition, the DTC principle is used to control the power factor at the stator terminals of the doubly fed machine to a desired level and also to perform the task of synchronization of stator voltage to the grid voltage. An integrated controller is used to implement these three functions.
Claims26
An apparatus for controlling the torque and power factor of a doubly fed machine using direct torque control, comprising:
- (a) means for calculating the estimated torque of said machine and a desired rotor flux command Ψr_ref;
- (b) means for calculating the actual rotor flux Ψr and converting said actual rotor flux from the stator reference frame to the rotor reference frame by multiplying Ψr by e−jθm;
- and
- (c) means for determining a torque error from said estimated torque and a reference torque, and a flux error from said desired rotor flux command and said actual rotor flux converted to the rotor reference frame, said determining means selecting an inverter voltage vector from said torque error and said flux error.
An apparatus for synchronizing a doubly fed machine having an induced stator voltage using direct torque control to an electrical grid having a grid voltage by controlling the tangential motion and radial length of a flux vector for the rotor of said machine, comprising:
- (a) means for determining the stator flux vector from said induced stator voltage and the grid flux vector from said grid voltage, said determining means calculating an angular error between said stator flux vector and said grid flux vector;
- (b) means for calculating a desired rotor flux command Ψr_ref;
- (c) means for calculating the actual rotor flux Ψr and for converting said actual rotor flux from the stator reference frame to the rotor reference frame by multiplying Ψr by e−jθm;
- and
- (d) means for comparing said angular error to zero to determine an error signal for controlling said rotor flux vector tangential motion, determining a flux error from said desired rotor flux command and said actual rotor flux converted to the rotor reference frame, said flux error for controlling said rotor flux vector radial length, and selecting an inverter voltage vector from said torque error and said flux error.
An apparatus for synchronizing a doubly fed machine having an induced stator flux vector using direct torque control to an electrical grid having a grid flux vector by controlling the tangential motion and radial length of a rotor flux vector for said machine, comprising:
- (a) means for calculating an angular error between said stator flux vector and said grid flux vector;
- (b) means for calculating a desired rotor flux command Ψr_ref;
- (c) means for calculating the actual rotor flux and converting said actual rotor flux from the stator reference frame to the rotor reference frame by multiplying Ψr by e−jθm;
- and
- (d) means for comparing said angular error to zero to determine an error signal for controlling said rotor flux vector tangential motion, determining a flux error from said desired rotor flux command and said actual rotor flux converted to the rotor reference frame, said flux error for controlling said rotor flux vector radial length, and selecting an inverter voltage vector from said torque error and said flux error.
A controller for controlling the torque and power factor of a doubly fed machine using direct torque control comprising:
- switch means for selecting either a first operating mode of said controller for controlling the torque and power factor of said machine or a second operating mode of said controller for synchronizing said machine to an electrical grid;
- said controller comprising when said first operating mode is selected:
- means for calculating the estimated torque of said machine;
- means for calculating a desired rotor flux command Ψr_ref;
- means for calculating the actual rotor flux Ψr and converting said actual rotor flux from the stator reference frame to the rotor reference frame by multiplying Ψr by e−jθm;
- and
- means for determining a torque error from said estimated torque and a reference torque and a flux error from said desired rotor flux command and said actual rotor flux converted to the rotor reference frame and for selecting an inverter voltage vector from said torque error and said flux error.
Dependencies are inferred from the claim text.