Control device for electric motor and control method for electric motor

• US 9,203,335 B2
• Filed: 04/16/2012
• Issued: 12/01/2015
• Est. Priority Date: 04/21/2011
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Nakamura, Hideo, Shoji, Mitsuhiro
• Primary Examiner(s): Ro, Bentsu
• Assistant Examiner(s): TRUNEH, ZEMENAY T
• Application Number:
  US14/112,749
• Publication Number:
  US 20140042938A1
• Time in Patent Office: 1,324 Days
• Field of Search: 318/400.01, 318/400.02, 307/151, 363 1- 12
• US Class Current: 1/1
• CPC Class Codes: H02P 21/0085 specially adapted for high speeds, e.g. above nominal speed
• CPC Class Codes: H02P 21/0089 using field weakening
• CPC Class Codes: H02P 21/05 specially adapted for damping motor oscillations, e.g. for reducing hunting
• CPC Class Codes: H02P 21/06 Rotor flux based control involving the use of rotor position or rotor speed sensors
• CPC Class Codes: H02P 21/14 Estimation or adaptation of machine parameters, e.g. flux, current or voltage
• CPC Class Codes: H02P 21/16 Estimation of constants, e.g. the rotor time constant
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop

Abstract

A control device 1 for an electric motor of the present invention includes: a current control unit 4 configured to calculate voltage command values v_d*, v_q* used to drive an electric motor 100, on the basis of a state quantity for voltage command value calculation and q and d-axis current detection values i_d, i_q, the state quantity calculated from a torque command value T*; and an over-modulation processing unit 16 configured to determine whether the electric motor 100 is stable or unstable in an over-modulation state, on the basis of the voltage command values v_d*, v_q*, current control constants, and electric motor constants, and to drive the electric motor 100 in the over-modulation state when determining that the electric motor 100 is stable.

Claims

1. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity for voltage being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, wherein the at least one state quantity for control includes an inductance value of the current control unit and an inductance value of the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit includes;

an over-modulation characteristic determination unit configured to determine which type of over-modulation stability the electric motor is in while in the over-modulation state, from at least two types of over-modulation stability, on the basis of the inductance value of the current control unit and the inductance value of the electric motor; and

a phase region determination unit configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, according to the type of over-modulation stability the electric motor is in, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not.

2. The control device for an electric motor according to claim 1, wherein the over-modulation processing unit is configured to drive the electric motor in the over-modulation state upon determining that the electric motor is stable in the over-modulation state.

3. The control device for an electric motor according to claim 1, wherein the over-modulation processing unit further includes a voltage phase limiting unit configured to change a current command value in such a way that the phase of the voltage command value is in the stable phase region, the current command value being the state quantity for voltage command value calculation.

4. The control device for an electric motor according to claim 3, wherein the current command value is a current in the magnetic pole direction.

5. The control device for an electric motor according to claim 1, wherein the over-modulation processing unit is configured such that, when determining whether the electric motor is stable or unstable in the over-modulation state, the over-modulation processing unit determines that a state of the electric motor changes to a stable or unstable state every time the phase of the voltage command value moves to a different quadrant on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction.

6. The control device for an electric motor according to claim 5, wherein the inductance value of the current control unit and the inductance value of the electric motor are preset in such a way that the type of over-modulation stability that the electric motor is in while in the over-modulation state is constant.

7. The control device for an electric motor according to claim 6, wherein:

a current command value, which is the state quantity for voltage command value calculation, is calculated based on a preset current-voltage conversion map, and

the current-voltage conversion map is preset to enable calculation of a current command value such that the phase of the voltage command value does not move to a different quadrant.

8. The control device for an electric motor according to claim 1, wherein:

the over-modulation processing unit further includes an over-modulation suppressing unit configured to reduce a modulation ratio when the electric motor is determined to be unstable in the over-modulation state, and

the over-modulation suppressing unit is configured such that the over-modulation suppressing unit does not reduce the modulation ratio when the modulation ratio of the electric motor is within a preset threshold.

9. The control device for an electric motor according to claim 1, wherein the over-modulation processing unit stores an inductance value of the current control unit for each of the at least two types of over-modulation stability, and selects one of the inductance values of the current control unit according to the phase of the voltage command value.

10. The control device for an electric motor according to claim 1, wherein:

the electric motor is connected to a transmission, and

the over-modulation processing unit is configured such that, when the electric motor is unstable in the over-modulation state, the over-modulation processing unit moves the phase of the voltage command value to a phase region in which the electric motor is stable in the over-modulation state, by causing the transmission to perform a gear-shift.

11. The control device for an electric motor according to claim 1, wherein:

the electric motor is connected to a drive force transmission mechanism capable of switching a transmission direction of a drive force, and

the over-modulation processing unit is configured such that, when the electric motor is unstable in the over-modulation state, the over-modulation processing unit moves the phase of the voltage command value to a phase region in which the electric motor is stable in the over-modulation state, by switching the transmission direction of the drive force.

12. The control device for an electric motor according to claim 1, wherein:

the electric motor is a power generator, and

the over-modulation processing unit is configured such that, when the power generator is unstable in the over-modulation state, the over-modulation processing unit moves the phase of the voltage command value to a phase region in which the electric motor is stable in the over-modulation state, by moving an operation point of the electric motor, representing a power generation amount and a number of revolutions of the power generator, along an even output line of a graphical representation of a relationship between a power generation amount and the number of revolutions of the power generator, the even output line being a line on the graphical representation at which an output of the electric motor is constant.

13. The control device for an electric motor according to claim 1, wherein

the state quantity for control includes a set of current control constants used by the current control unit to control the electric motor, and

the over-modulation processing unit is configured to store the current control constants, select a current control constant at which the electric motor is stable in the over-modulation state, on the basis of the phase of the voltage command value, and output the selected current control constant to the current control unit.

14. The control device for an electric motor according to claim 13, wherein the over-modulation processing unit is configured to store the current control constant for each of the at least two types of over-modulation stability, determine that the electric motor is in the over-modulation state when a modulation ratio of the electric motor is equal to or larger than a predetermined value, and select the current control constant of the type of over-modulation stability, among the at least two types of over-modulation stability, at which the electric motor is stable, on the basis of the phase of the voltage command value.

15. The control device for an electric motor according to claim 14, wherein the over-modulation processing unit is configured to store the current control constant corresponding to a position at a boundary between the at least two types of over-modulation stability, and select the current control constant corresponding to the position at the boundary when the modulation ratio of the electric motor is smaller than the predetermined value.

16. The control device for an electric motor according to claim 13, wherein the over-modulation processing unit is configured to continuously change the current control constants, according to the phase of the voltage command value.

17. The control device for an electric motor according to claim 13, wherein the over-modulation processing unit is configured to reduce a modulation ratio of the electric motor at a position where the phase of the voltage command value is near a boundary of quadrants.

18. The control device for an electric motor according to claim 13, wherein the current control constants are the inductance values of the current control unit.

19. A control method for controlling an electric motor by vector control, the method comprising:

calculating a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity for voltage being calculated from a torque command value used to drive the electric motor; and

determining whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, wherein the at least one state quantity for control includes an inductance value of a current control unit and an inductance value of the electric motor; and

driving the electric motor on the basis of a result of the determination,

wherein the step of determining whether the electric motor is stable or unstable in the over-modulation state, on the basis of the phase of the voltage command value and the at least one state quantity for control which is used to control the electric motor includes;

determining which type of over-modulation stability the electric motor is in while in the over-modulation state, from at least two types of over-modulation stability, on the basis of the inductance value of the current control unit and the inductance value of the electric motor;

identifying a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, according to the type of over-modulation stability the electric motor is in, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction;

determining whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not.

20. A control device configured to control an electric motor by vector control, the control device comprising:

current control means for calculating a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity for voltage being calculated from a torque command value used to drive the electric motor; and

over-modulation processing means for (i) determining whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, wherein the at least one state quantity for control includes an inductance value of the current control means and an inductance value of the electric motor, and (ii) driving the electric motor on the basis of a result of the determination,

wherein the over-modulation processing means includes;

over-modulation characteristic determination means for determining which type of over-modulation stability the electric motor is in while in the over-modulation state, from at least two types of over-modulation stability, on the basis of the inductance value of the current control means and the inductance value of the electric motor; and

phase region determination means for (i) identifying a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, according to the type of over-modulation stability the electric motor is in on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determining whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not.

21. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit is configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not, and

wherein the over-modulation processing unit is configured such that, when determining whether the electric motor is stable or unstable in the over-modulation state, the over-modulation processing unit determines that a state of the electric motor changes to a stable or unstable state every time the phase of the voltage command value moves to a different quadrant on the coordinate system defined in the magnetic pole direction and the direction orthogonal to the magnetic pole direction.

22. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit is configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not,

wherein the over-modulation processing unit further includes an over-modulation suppressing unit configured to reduce a modulation ratio when the electric motor is determined to be unstable in the over-modulation state, and

wherein the over-modulation suppressing unit is configured such that the over-modulation suppressing unit does not reduce the modulation ratio when the modulation ratio of the electric motor is within a preset threshold.

23. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit is configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not, and

wherein the over-modulation processing unit stores an inductance value of the current control unit for each of at least two types of over-modulation stability, and selects one of the inductance values of the current control unit according to the phase of the voltage command value.

24. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit is configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not,

wherein the electric motor is connected to a transmission, and

wherein the over-modulation processing unit is configured such that, when the electric motor is unstable in the over-modulation state, the over-modulation processing unit moves the phase of the voltage command value to a phase region in which the electric motor is stable in the over-modulation state, by causing the transmission to perform a gear-shift.

25. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit is configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not,

wherein the electric motor is connected to a drive force transmission mechanism capable of switching a transmission direction of a drive force, and

wherein the over-modulation processing unit is configured such that, when the electric motor is unstable in the over-modulation state, the over-modulation processing unit moves the phase of the voltage command value to a phase region in which the electric motor is stable in the over-modulation state, by switching the transmission direction of the drive force.

26. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit is configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not,

wherein the electric motor is a power generator, and

wherein the over-modulation processing unit is configured such that, when the power generator is unstable in the over-modulation state, the over-modulation processing unit moves the phase of the voltage command value to a phase region in which the electric motor is stable in the over-modulation state, by moving an operation point of the electric motor, representing a power generation amount and a number of revolutions of the power generator, along an even output line of a graphical representation of a relationship between a power generation amount and the number of revolutions of the power generator, the even output line being a line on the graphical representation at which an output of the electric motor is constant.

27. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit is configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not,

wherein the state quantity for control includes a set of current control constants used by the current control unit to control the electric motor,

wherein the over-modulation processing unit is configured to store the current control constants, select a current control constant at which the electric motor is stable in the over-modulation state, on the basis of the phase of the voltage command value, and output the selected current control constant to the current control unit,

wherein the over-modulation processing unit is configured to store the current control constant for each of at least two types of over-modulation stability, determine that the electric motor is in the over-modulation state when a modulation ratio of the electric motor is equal to or larger than a predetermined value, and select the current control constant of the type of over-modulation stability, among the at least two types of over-modulation stability, at which the electric motor is stable, on the basis of the phase of the voltage command value, and

wherein the over-modulation processing unit is configured to store the current control constant corresponding to a position at a boundary between the at least two types of over-modulation stability, and select the current control constant corresponding to the position at the boundary when the modulation ratio of the electric motor is smaller than the predetermined value.

28. A control device configured to control an electric motor by vector control, the control device comprising:

a current control unit configured to calculate a voltage command value used to drive the electric motor, on the basis of a state quantity for voltage command value calculation and a current detection value detected from the electric motor, the state quantity being calculated from a torque command value used to drive the electric motor; and

an over-modulation processing unit configured to (i) determine whether the electric motor is stable or unstable in an over-modulation state, on the basis of a phase of the voltage command value and at least one state quantity for control which is used to control the electric motor, and (ii) drive the electric motor on the basis of a result of the determination,

wherein the over-modulation processing unit is configured to (i) identify a stable phase region of the voltage command value in which the electric motor is stable in the over-modulation state, on the basis of quadrants on a coordinate system defined in a magnetic pole direction and a direction orthogonal to the magnetic pole direction, and (ii) determine whether the electric motor is stable or unstable in the over-modulation state, on the basis of whether the phase of the voltage command value is in the stable phase region or not,

wherein the state quantity for control includes a set of current control constants used by the current control unit to control the electric motor,

wherein the over-modulation processing unit is configured to store the current control constants, select a current control constant at which the electric motor is stable in the over-modulation state, on the basis of the phase of the voltage command value, and output the selected current control constant to the current control unit, and

wherein the over-modulation processing unit is configured to continuously change the current control constants, according to the phase of the voltage command value.