Method and system for controlling an angualr speed of an induction motor

Patent metadata

Field	Value
Publication number	US-9780711-B2
Application number	US-201514612429-A
Country	US
Kind code	B2
Filing date	Feb 3, 2015
Priority date	Feb 3, 2015
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

A system and method controls a rotor angular speed of an induction motor by first sensing an operation condition of the induction motor to produce measured signals, which are transformed by applying a state transformation to an induction motor model to produce a transformed induction motor model. Transformed state estimates of the transformed induction motor model are produced based on the measured signals. An inverse of the state transformation is applied to the transformed state estimates to produce state estimates of the induction motor model, which are then used to determine control input voltages for the induction motor, based on the state estimates, to control the rotor angular speed of the induction motor.

First claim

I claim:

1. A method for controlling a rotor angular speed of an induction motor, comprising steps of:
sensing an operation condition of the induction motor to produce measured signals;
transforming the measured signal by applying a state transformation to an induction motor model to produce a transformed induction motor model;
producing transformed state estimates of the transformed induction motor model based on the measured signals, wherein the transformed state estimates of the transformed induction motor model are produced by a set of estimators of a set of subsystems of the transformed induction motor model, wherein the set of the subsystems are determined by applying the state transformation to the induction motor model to obtain the transformed induction motor model; decomposing the transformed induction motor model into the set of the subsystems; and designing a state estimator of each subsystem by treating states of previous subsystems as known;
applying an inverse of the state transformation to the transformed state estimates to produce state estimates of the induction motor model;
determining control input voltages to the induction motor based on the state estimates; and
applying the control input voltages to the induction motor to control the rotor angular speed.

2. The method of claim 1 , wherein the measured signals are stator voltages and currents of the induction motor.

3. The method of claim 1 , wherein states of the set of the subsystems are estimated sequentially so the states for a previous subsystems are known for subsequent subsystems.

4. The method of claim 1 , wherein a particular state transformation is,
where i_ds,i_qs,φ_dr,φ_qr,ω denote a stator current in a d-axis, a state current in q-axis, a rotor flux in the d-axis, a rotor flux in a q-axis, and the rotor angular speed, respectively, and α is predetermined constant.

5. The method of claim 4 , wherein the set of the subsystems comprises a subsystem with states (i_ds,αφ_dr+ωφ_qr), a subsystem with states (i_qs,αφ_qr-ωφ_dr), and a subsystem with states ω.

6. The method of claim 4 , where the set of the subsystems comprises a subsystem with states (i_ds,αφ_dr+ωφ_qr,i_qs,αφ_qr-ωφ_dr), and a subsystem with states ω.

7. The method of claim 4 , wherein a particular state transformation is
z =[i _ ds,i _ qs,βφ _ dr+i _ ds,βφ _ qr+i _ qs,ω],

where z denotes new coordinates, and β is a predetermined constant.

8. The method of claim 4 , where the set of the subsystems comprise a subsystem with states (i_ds,i_qs,βφ_dr+i_ds,βφ_qr+i_qs), and a subsystem with states ω.

9. The method of claim 1 , wherein a high gain observer is used for each subsystem.

10. The method of claim 1 , wherein a finite time convergent observer is used for each subsystem.

11. A system for controlling a rotor angular speed of an induction motor, comprising:
a sensor configured to sense an operation condition of the induction motor to produce measured signals;
a transformation block configured to transform the measured signal by applying a state transformation to an induction motor model to produce a transformed induction motor model;
means for producing transformed state estimates of the transformed induction motor model based on the measured signals, and applying an inverse of the state transformation to the transformed state estimates to produce state estimates of the induction motor model, wherein the transformed state estimates of the transformed induction motor model are produced by a set of estimators of a set of subsystems of the transformed induction motor model, wherein the set of the subsystems are determined by applying the state transformation to the induction motor model to obtain the transformed induction motor model; decomposing the transformed induction motor model into the set of the subsystems; and designing a state estimator of each subsystem by treating states of previous subsystems as known;
means for determining control input voltages to the induction motor based on the state estimates, and applying the control input voltages to the induction motor to control the rotor angular speed.

Assignees

• Mitsubishi Electric Res Laboratories Inc

Inventors

• Wang Yebin

Classifications

• H02P21/24

  Vector control not involving the use of rotor position or rotor speed sensors · CPC title

• H02P21/0017 Primary

  Model reference adaptation, e.g. MRAS or MRAC, useful for control or parameter estimation · CPC title

• H02P21/13

  Observer control, e.g. using Luenberger observers or Kalman filters · CPC title