System and method for permanent magnet motor control

Patent metadata

Field	Value
Publication number	US-10075116-B2
Application number	US-201715494595-A
Country	US
Kind code	B2
Filing date	Apr 24, 2017
Priority date	Apr 26, 2012
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

A method of operating an electric motor is disclosed. The method includes: starting the electric motor in an open loop control mode; operating an estimator that estimates operating conditions of the electric motor; and, while the electric motor is in the open loop control mode, evaluating a first parameter of the estimator. The method further includes: in response to the evaluation of the first parameter, determining whether the estimator has converged; and in response to a determination that the estimator has not converged within a predetermined period of time after starting the electric motor, signaling a first fault condition.

First claim

What is claimed is:

1. A method of operating an electric motor, the method comprising:
starting the electric motor in an open loop control mode;
using an estimator module, estimating derivatives with respect to time of total flux linkages of the electric motor based on at least one measured parameter of the electric motor;
while the electric motor is in the open loop control mode, evaluating the derivatives of the total flux linkages estimated by the estimator module;
in response to the evaluation of the derivatives of the total flux linkages, determining whether the estimator module has converged; and
in response to a determination that the estimator module has not converged within a predetermined period of time after starting the electric motor, signaling a first fault condition and at least one of: (i) shutting down the electric motor; and (ii) restarting the electric motor.

2. The method of claim 1 wherein the electric motor is a compressor motor.

3. The method of claim 1 further comprising:
switching to a closed loop control mode;
while the electric motor is in the closed loop control mode, evaluating a parameter of the estimator module; and
in response to the evaluation of the parameter, selectively signaling a second fault condition.

4. The method of claim 3 further comprising signaling both the first fault condition and the second fault condition using a common 1-bit signal.

5. The method of claim 1 wherein the evaluating the derivatives of the total flux linkages includes calculating a variance of the total flux linkage derivatives.

6. The method of claim 3 wherein the parameter includes magnet flux linkages.

7. The method of claim 6 wherein the evaluating the parameter includes calculating a magnitude of the magnet flux linkages.

8. The method of claim 3 wherein the evaluating the parameter includes:
comparing a measure of the parameter with a threshold;
incrementing a counter in response to the measure being greater than the threshold; and
decrementing the counter in response to the measure being less than the threshold.

9. The method of claim 8 further comprising applying an upper limit to the counter, wherein the counter is incremented only up to the upper limit.

10. The method of claim 8 further comprising signaling the second fault condition in response to the counter being decremented to a lower limit.

11. The method of claim 8 further comprising, for a second predetermined period of time beginning at the switch to closed loop mode, suspending incrementing the counter and decrementing the counter.

12. The method of claim 1 wherein the evaluating the derivatives of the total flux linkages includes:
comparing a measure of the derivatives of the total flux linkages to (i) a lower threshold and (ii) an upper threshold that is greater than the lower threshold;
incrementing a counter in response to the measure being less than the lower threshold; and
decrementing the counter in response to the measure being greater than the upper threshold.

13. The method of claim 12 wherein the evaluating the derivatives of the total flux linkages further includes, in response to the measure being between the lower threshold and the upper threshold, decrementing the counter in response to the counter being decremented immediately previously.

14. The method of claim 12 further comprising determining that the estimator module has converged in response to the counter being incremented to an upper limit.

15. The method of claim 12 wherein the evaluating the derivatives of the total flux linkages further includes applying a lower limit to the counter, wherein the counter is decremented only down to the lower limit.

16. The method of claim 3 wherein switching to the closed loop control mode is performed in response to a determination that the estimator module has converged.

17. The method of claim 3 wherein switching to the closed loop control mode is performed when the predetermined period of time has passed after starting the electric motor.

18. A control system for an electric motor, the control system comprising:
an estimator module that estimates derivatives of total flux linkages with respect to time of the electric motor based on at least one measured parameter of the electric motor; and
a rotor check module that:
commands operation of the electric motor in an open loop control mode at startup of the electric motor;
while the electric motor is in the open loop control mode, evaluates the derivatives of total flux linkages estimated by the estimator module;
in response to the evaluation of the derivatives of total flux linkages, determines whether the estimator module has converged; and
in response to a determination that the estimator module has not converged within a predetermined period of time after starting the electric motor, signals a first fault condition and at least one of: (i) shuts down the electric motor; and (ii) restarts the electric motor.

19. The control system of claim 18 wherein the rotor check module further:
commands a transition to operating the electric motor in a closed loop control mode;
while the electric motor is in the closed loop control mode, evaluates a parameter of the estimator module; and
in response to the evaluation of the parameter, selectively signals a second fault condition.

20. The control system of claim 18 wherein:
the evaluation of the derivatives of the total flux linkages includes the rotor check module calculating a variance of the total flux linkage derivatives while the electric motor is in the open loop control mode; and
the determination of whether the estimator module has converged includes the rotor check module determining whether the estimator module has converged based on the variance of the total flux linkage derivatives.

Assignees

• Emerson Climate Technologies

Inventors

• Marcinkiewicz Joseph G
• Green Charles E
• Henderson Michael I

Classifications

• F25B49/025

  Motor control arrangements · CPC title

• H02P29/0241

  the fault being an overvoltage · CPC title

• B60H1/00428

  electric · CPC title

• H02P21/22 Primary

  Current control, e.g. using a current control loop · CPC title

• F25B2500/26

  characterised by the startup of the refrigeration cycle · CPC title