Switched reluctance motor power estimation compensation for variable DC-link voltage

Patent metadata

Field	Value
Publication number	US-9941831-B1
Application number	US-201715618184-A
Country	US
Kind code	B1
Filing date	Jun 9, 2017
Priority date	Jun 9, 2017
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

A control system for a switched reluctance (SR) motor includes a Direct Current (DC) power source, and an inverter. The control system includes a user interface configured to enable an operator to specify a desired torque output. The control system further includes a controller which converts a DC current from the Alternating Current (AC) supplied to the SR motor by the inverter. The controller estimates an actual power output generated by the SR motor based on a DC voltage supplied by the DC power source to the inverter, and the converted DC current. The controller estimates an actual torque output based on the actual power output and a rotational speed of the SR motor. The controller compares the actual torque output and a desired torque output to calculate a torque error. The controller adjusts a torque output limit and the rotational speed of the SR motor.

First claim

What is claimed is:

1. A control system for a switched reluctance (SR) motor, the control system comprising:
a Direct Current (DC) power source;
an inverter coupled to the DC power source towards an input side of the inverter, and coupled to the SR motor towards an output side of the inverter, wherein the inverter is configured to receive DC voltage from the DC power source and supply Alternating Current (AC) to the SR motor;
a user interface configured to enable an operator to specify a desired torque output, and generate signals indicative of the desired torque output;
a controller communicably coupled to the SR motor, DC power source, the inverter, and the user interface, wherein the controller is configured to:
convert a DC current from the AC current supplied to the SR motor by the inverter;
estimate an actual power output generated by the SR motor based at least on the DC voltage and the converted DC current;
determine a rotational speed of the SR motor;
estimate an actual torque output based on the actual power output and the rotational speed of the SR motor;
receive the signals indicative of the desired torque output from the user interface;
compare the actual torque output and the desired torque output to calculate a torque error;
adjust a torque output limit based on the calculated torque error, and
adjust the rotational speed of the SR motor based on the adjusted torque output limit.

2. The control system of claim 1 , wherein the controller estimates the actual power output based on an inverter efficiency, a SR motor efficiency, the DC voltage, and the DC current.

3. The control system of claim 1 , wherein the controller calculates the output torque error by calculating a difference between the actual torque output and the desired torque output.

4. The control system of claim 1 , wherein the controller estimates the actual power output by multiplying the DC voltage and the DC current.

5. The control system of claim 1 , wherein the controller estimates the actual torque output by dividing the actual power output by the rotational speed of the SR motor.

6. The control system of claim 1 , wherein the controller determines the rotational speed of the SR motor through at least one of a speed sensor or a speed estimation module.

7. A switched reluctance drive comprising:
a switched reluctance (SR) motor having a stator, and a rotor configured to rotate inside the stator;
a DC power source;
an inverter coupled to the DC power source towards an input side of the inverter, and coupled to the SR motor towards an output side of the inverter, wherein the inverter is configured to receive DC voltage from the DC power source and supply AC current to the SR motor;
a user interface configured to enable an operator to request a desired torque output, and generate signals indicative of the desired torque output;
a controller communicably coupled to the SR motor, the DC power source, the inverter, and the user interface, wherein the controller is configured to:
reconstruct a DC current from the AC current supplied to the SR motor by the inverter;
estimate an actual power output generated by the SR motor based at least on the DC voltage and the reconstructed DC current;
determine a rotational speed of the SR motor;
estimate an actual torque output based on the actual power output and the rotational speed of the SR motor;
receive the signals indicative of the desired torque output from the user interface;
compare the actual torque output and the desired torque output to calculate a torque error;
adjust a torque output limit based on the calculated torque error; and
adjust the actual torque output of the SR motor based on the adjusted torque output limit.

8. The switched reluctance drive of claim 7 , wherein the controller estimates the actual power output based on an inverter efficiency, a SR motor efficiency, the DC voltage and the DC current.

9. The switched reluctance drive of claim 7 , wherein the controller calculates the output torque error by calculating a difference between the actual torque output and the desired torque output.

10. The switched reluctance drive of claim 7 , wherein the controller estimates the actual power output by multiplying the DC voltage and the DC current.

11. The switched reluctance drive of claim 7 , wherein the controller estimates the actual torque output by dividing the actual power output by the rotational speed of the SR motor.

12. The switched reluctance drive of claim 7 , wherein the controller determines the rotational speed of the SR motor through at least one of a speed sensor or a speed estimation module.

13. A method of controlling a switched reluctance (SR) motor, the method comprising:
converting, by a controller, a Direct Current (DC) from an Alternating Current (AC), wherein the AC current is supplied to the SR motor by an inverter,
estimating, by the controller, an actual power output generated by the SR motor based at least on the converted DC current and a DC voltage, wherein the DC voltage is supplied to the inverter by a DC power source;
determining, by the controller, a rotational speed of the SR motor;
estimating, by the controller, an actual torque output based on the actual power output and the rotational speed of the SR motor;
receiving, by the controller, signals indicative of a desired torque output from a user interface;
comparing, by the controller, the actual torque output and the desired torque output to calculate a torque error;
adjusting, by the controller, a torque output limit based on the calculated torque error;
adjusting, by the controller, the rotational speed of the SR motor based on the adjusted torque output limit; and
the rotational speed of the SR motor being adjusted to minimize the calculated torque error.

14. The method of claim 13 , wherein the controller determines the rotational speed of the SR motor through at least one of a speed sensor or a speed estimation module.

15. The method of claim 13 , wherein the controller estimates the actual power output based on an inverter efficiency, a SR motor efficiency, and with the DC voltage and the DC current.

16. The method of claim 15 , wherein the controller calculates the output torque error by calculating a difference between the actual torque output and the desired torque output.

17. The method of claim 13 , wherein the controller estimates the actual power output by multiplying the DC voltage and the DC current.

18. The method of claim 13 , wherein the controller estimates the actual torque output by dividing the actual power output by the speed of the SR motor.

19. The method of claim 13 , wherein the rotational speed of the SR motor is adjusted to minimize the calculated torque error.

20. The method of claim 13 , wherein the torque output limit is based on characteristic properties of the SR motor.

Assignees

• Caterpillar Inc

Inventors

• Miller Jason L
• Inoa Ernesto
• Gerdes Jesse
• Crosman Iii Alexander C
• Nino-Baron Carlos E
• Sopko Jr Thomas Michael
• Wai Jackson
• Khalil Ahmed

Classifications

• E02F9/207

  of the type electric propulsion units, e.g. electric motors or generators · CPC title

• H02P6/08

  Arrangements for controlling the speed or torque of a single motor (H02P6/10, H02P6/28 take precedence) · CPC title

• H02P25/08 Primary

  Reluctance motors · CPC title

• H02P2203/01

  Motor rotor position determination based on the detected or calculated phase inductance, e.g. for a Switched Reluctance Motor · CPC title