METHODS AND SYSTEMS FOR DIAGNOSING STATOR WINDINGS IN AN ELECTRIC MOTOR

• US 20100320953A1
• Filed: 06/18/2009
• Published: 12/23/2010
• Est. Priority Date: 06/18/2009
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: ANWAR, MOHAMMAD N., SCHULZ, STEVEN E., YEH, CHIA-CHOU
• Granted Patent: US 8,354,817 B2
• Time in Patent Office: Days
• US Class Current: 318/490
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: H02P 21/06 Rotor flux based control involving the use of rotor position or rotor speed sensors
• CPC Class Codes: H02P 29/02 Providing protection against overload without automatic interruption of supply protection against faults of stepper motors H02P8/36
• CPC Class Codes: H02P 29/0243 the fault being a broken phase

Abstract

Systems and methods are provided for diagnosing stator windings in an electric motor operating under control of a current-regulating control loop. The current-regulating control loop is configured to provide a command voltage to the electric motor. The command voltage comprises a current-regulated voltage based on a difference between a commanded current and a measured current through the stator windings. The method comprises determining a negative sequence component of the command voltage, and identifying a fault condition when a characteristic of the negative sequence component is greater than a threshold value.

Claims

1. An electrical system for use in a vehicle, the electrical system comprising:

an electric motor having stator windings;

an energy source;

an inverter module coupled between the energy source and the stator windings, the inverter module being configured to provide a commanded voltage from the energy source to the stator windings of the electric motor;

a plurality of current sensors coupled between the inverter module and the stator windings, the plurality of current sensors being configured to measure current through the stator windings, resulting in measured current; and

a control module coupled to the inverter module and the plurality of current sensors, the control module being configured to;

obtain a current command corresponding to a commanded current for the stator windings of the electric motor;

generate a voltage command corresponding to the commanded voltage based on a difference between the measured current and the commanded current;

determine a negative sequence voltage for the stator windings based on the voltage command; and

identify a fault condition in the stator windings based on the negative sequence voltage component.

2. The electrical system of claim 1, wherein the control module is configured to identify the fault condition in the stator windings by:

determining a DC component of the negative sequence voltage; and

identifying the fault condition when a magnitude of the DC component of the negative sequence voltage exceeds a threshold value.

3. The electrical system of claim 1, wherein the control module is configured to identify the fault condition in the stator windings by:

determining a DC component of the negative sequence voltage; and

identifying the fault condition when a rate of change of the DC component of the negative sequence voltage exceeds a threshold value.

4. The electrical system of claim 1, wherein the control module includes a current regulator configured to generate the voltage command based on the difference between the measured current and the commanded current such that the measured current is regulated to the commanded current.

5. The electrical system of claim 4, the current regulator comprising a synchronous frame current regulator configured to generate the voltage command in a counterclockwise synchronous reference frame, resulting in a synchronous frame voltage command.

6. The electrical system of claim 5, wherein the control module is configured to determine the negative sequence voltage by:

obtaining a transformation angle; and

transforming the synchronous frame voltage command to a clockwise synchronous reference frame based on the transformation angle.

7. The electrical system of claim 6, wherein the control module is configured to determine the transformation angle based on a relationship between the measured current and the voltage command.

8. The electrical system of claim 6, further comprising a resolver system coupled between the electric motor and the control module, the resolver system being configured to obtain a position of a rotor of the electric motor, wherein the control module is configured to determine the transformation angle based on the position of the rotor.

9. A method for diagnosing stator windings in an electric motor in a vehicle, the method comprising:

generating a voltage command for the stator windings, the voltage command being configured to regulate current through the stator windings to a commanded value;

determining a negative sequence voltage based on the voltage command; and

identifying a fault condition based on the negative sequence voltage.

10. The method of claim 9, wherein identifying the fault condition comprises:

determining a DC component of the negative sequence voltage; and

identifying the fault condition based on a characteristic of the DC component of the negative sequence voltage.

11. The method of claim 10, wherein identifying the fault condition based on the characteristic of the DC component of the negative sequence voltage comprises identifying the fault condition when a magnitude of the DC component of the negative sequence voltage exceeds a threshold value.

12. The method of claim 10, wherein identifying the fault condition based on the characteristic of the DC component of the negative sequence voltage comprises identifying the fault condition when a rate of change of the DC component of the negative sequence voltage exceeds a threshold value.

13. The method of claim 10, further comprising:

obtaining a current command for the electric motor, the current command corresponding to the commanded value; and

measuring currents through the stator windings, resulting in a measured motor currents, wherein generating the voltage command for the stator windings comprises generating the voltage command based on a difference between the current command and the measured motor currents such that the measured motor currents are regulated to the commanded value.

14. The method of claim 10, further comprising

obtaining a synchronous frame current command for the electric motor;

and

obtaining a synchronous frame motor current through the stator windings, wherein generating the voltage command for the stator windings comprises generating a synchronous frame voltage command based on a difference between the synchronous frame current command and the synchronous frame motor current such that the synchronous frame motor current is regulated to the synchronous frame current command.

15. The method of claim 14, wherein determining the negative sequence voltage comprises:

transforming the synchronous frame voltage command to a negative synchronous reference frame, resulting in a negative synchronous frame voltage;

filtering the negative synchronous frame voltage, resulting in a filtered negative synchronous frame voltage; and

determining a magnitude of the filtered negative synchronous frame voltage.

16. A method for diagnosing stator windings in an electric motor operating under control of a current-regulating control loop, the current-regulating control loop being configured to provide a command voltage to the electric motor, the command voltage comprising a current-regulated voltage based on a difference between a commanded current and a measured current through the stator windings, the method comprising:

determining a negative sequence component of the command voltage; and

identifying a fault condition when a characteristic of the negative sequence component is greater than a threshold value.

17. The method of claim 16, the command voltage being expressed in a synchronous reference frame, wherein determining the negative sequence component of the command voltage comprises:

transforming the command voltage from the synchronous reference frame to a negative synchronous reference frame, resulting in a negative synchronous reference frame voltage; and

determining a magnitude of a DC component of the negative synchronous reference frame voltage.

18. The method of claim 17, wherein identifying the fault condition based on the characteristic of the negative sequence component comprises identifying the fault condition when a magnitude of the DC component of the negative synchronous reference frame voltage exceeds a threshold magnitude.

19. The method of claim 17, wherein identifying the fault condition based on the characteristic of the negative sequence component comprises identifying the fault condition when a rate of change of the DC component of the negative synchronous reference frame voltage exceeds a threshold rate of change.

20. The method of claim 17, further comprising low-pass filtering the negative synchronous reference frame voltage, resulting in the DC component of the negative synchronous reference frame voltage.