CONTROL SYSTEM FOR MULTIPHASE ROTARY MACHINES

• US 20090160377A1
• Filed: 12/19/2008
• Published: 06/25/2009
• Est. Priority Date: 12/19/2007
• Status: Active Grant

• Current Assignee: DENSO Corporation
• Original Assignee: DENSO Corporation
• Inventors: Yamada, Takahiro
• Granted Patent: US 8,098,032 B2
• Time in Patent Office: Days
• US Class Current: 318/400.20
• CPC Class Codes: H02M 7/53871 with automatic control of output voltage or current
• CPC Class Codes: H02M 7/53876 based on synthesising a desired voltage vector via the selection of appropriate fundamental voltage vectors, and corresponding dwelling times
• CPC Class Codes: H02P 21/00 Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation

Abstract

A control system is designed to use a plurality of voltage vectors expressing a switching mode for a switching circuit to thereby control a difference between a current actually flowing through a multiphase rotary machine and a command current value therefor within an allowable range. The plurality of voltage vectors include a zero vector that allows line-to-line voltages in the multiphase rotary machine to be all zero, and a plurality of non-zero vectors that allow at least one of line-to-line voltage in the multiphase rotary machine to be nonzero. A drive unit is configured to switch only one phase of the switching element for each shift of the switching mode to thereby shift, in accordance with a preset switching pattern, the switching mode from a specified one of the plurality of non-zero vectors to the specified one of the plurality of non-zero vectors via the zero vector.

Claims

1. A control system designed to use a plurality of voltage vectors expressing a switching mode for a switching circuit having a switching element per phase of a multiphase rotary machine to thereby control a difference between a current actually flowing in the multiphase rotary machine and a command current value therefor within an allowable range, the plurality of voltage vectors including a zero vector that allows line-to-line voltages in the multiphase rotary machine to be all zero, and a plurality of non-zero vectors that allow at least one of line-to-line voltage in the multiphase rotary machine to be nonzero, the control system comprising:

a drive unit configured to switch only one phase of the switching element for each shift of the switching mode to thereby shift, in accordance with a preset switching pattern, the switching mode from a specified one of the plurality of non-zero vectors to the specified one of the plurality of non-zero vectors via the zero vector.

2. The control system according to claim 1, wherein the plurality of non-zero vectors define a plurality of separated regions in a space around a center point at which the difference is zero, further comprising:

a calculating unit configured to calculate a direction of change in the difference during the switching mode for the switching circuit being set to the zero vector,

the drive unit further comprising a difference control unit configured to;

receive the difference and the direction of change in the difference; and

control the difference such that the difference is shifted in a direction opposite to the direction of change in the difference.

3. The control system according to claim 2, wherein the difference is obtained by subtracting the current actually flowing in the rotary machine from the command current value, and the difference control unit is configured to:

when a steady-state condition in that one of the non-zero vectors that is the closest to the difference defines one boundary of the one of the plurality of regions and the difference is located out of the allowable range is met, set the one of the non-zero vectors that is the closest to the difference to a first switching vector, the one of the plurality of regions containing a vector of the difference from the center point;

set, to a second switching vector, an alternative one of the plurality of non-zero vectors that defines the other boundary of the one of the plurality of regions containing the vector of the difference; and

control the difference by shifting the switching mode in accordance with the preset switching pattern, the preset switching pattern representing in a shift order of the first switching vector, the second switching vector, and the first switching vector.

4. The control system according to claim 3, wherein the difference control unit is configured to shift the switching mode from the first switching vector to the second switching vector when the difference is shifted from one of the plurality of regions separated by the first and second switching vectors to an outside thereof while being not located in the one of the plurality of regions.

5. The control system according to claim 3, wherein the difference control unit is configured to shift the switching mode from the first switching vector to the second switching vector when the difference is not located in one of the plurality of regions while increasing out of the allowable range, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions.

6. The control system according to claim 3, wherein the difference control unit is configured to shift the switching mode from the second switching vector to the first switching vector when the difference is located in one of the plurality of regions symmetrical about the center point from a region into which the difference has entered at a time when the switching mode is shifted to the second switching vector.

7. The control system according to claim 6, wherein the difference control unit is configured to shift the switching mode from the second switching vector to the first switching vector when the difference is not located in one of the plurality of regions while increasing out of the allowable range, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions.

8. The control system according to claim 3, wherein, after the switching mode being shifted from the second switching vector to the first switching vector, the difference control unit is configured to shift the switching mode to the zero vector when the difference crosses a line, the line extending from the center point in the direction of change in the difference and the opposite direction thereto.

9. The control unit according to claim 3, wherein, after the switching mode being shifted from the second switching vector to the first switching vector, the difference control unit is configured to shift the switching mode to the zero vector when the difference is located in one of the plurality of regions while increasing out of the allowable range, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions.

10. The control unit according to claim 3, wherein, under the switching mode being set to the second switching vector, the difference control unit is configured to shift the switching mode from the second switching vector to the zero vector when the difference is located in one of the plurality of regions while increasing out of the allowable range, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions.

11. The control unit according to claim 3, wherein, under the switching mode being set to the first switching vector at a moment when the steady-state condition is met, the difference control unit is configured to shift the switching mode from the first switching vector to the zero vector when the difference is located in one of the plurality of regions while increasing out of the allowable range, and crosses a line, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions, the line extending from the center point in the direction of change in the difference and the opposite direction thereto.

12. The control unit according to claim 3, wherein, under the switching mode being set to the first switching vector at a moment when the steady-state condition is met, the difference control unit is configured to shift the switching mode from the first switching vector to the zero vector when the difference is located in one of the plurality of regions while increasing out of the allowable range, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions.

13. The control unit according to claim 3, further comprising:

a transient control unit configured to, under the switching mode being set to one of the second switching vector following the first switching vector and the zero vector, set the switching mode to one of the plurality of non-zero vectors that is the closest to the difference when a preset positional transient condition between the difference and the direction of change in the difference is met in the space.

14. The control system according to claim 13, wherein, under the switching mode being set to the second switching vector, the transient control unit is configured to set the switching mode to the one of the plurality of non-zero vectors that is the closest to the difference when, as the preset positional transient condition, the difference is not located in one of the plurality of regions while increasing out of the allowable range, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions.

15. The control system according to claim 13, wherein, under the switching mode being set to the zero vector, the transient control unit is configured to set the switching mode to the one of the plurality of non-zero vectors that is the closest to the difference when, as the preset positional transient condition, the difference does not define one boundary of the one of the plurality of regions that contains the vector of the difference from the center point while increasing out of the allowable range.

16. The control system according to claim 13, wherein the transient control unit is configured to update the switching mode to the one of the plurality of non-zero vectors that is the closest to an actual value of the difference when:

the one of the plurality of non-zero vectors that is the closest to the difference does not define one boundary of the one of the plurality of regions that contains the vector of the difference from the center point;

the difference is not located in the one of the plurality of regions, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions; and

the difference increases out of the allowable range.

17. The control system according to claim 13, wherein the drive unit is configured to, under the switching mode being controlled by the transient control unit, shift the switching mode to the zero vector when the difference crosses a line, the line extending from the center point in the direction of change in the difference and the opposite direction thereto.

18. The control system according to claim 13, wherein the drive unit is configured to, under the switching mode being controlled by the transient control unit, shift the switching mode to the zero vector when the difference is located in the one of the plurality of regions and increases out of the allowable range, the direction opposite to the direction of change in the difference passing through the one of the plurality of regions.

19. The control system according to claim 3, wherein the difference control unit comprises an identifying unit configured to:

calculate a first inner product of the vector of the difference and a first non-zero vector included in the plurality of non-zero vectors;

calculate a second inner product of the vector of the difference and a second non-zero vector included in the plurality of non-zero vectors;

the first and second non-zero vectors separating the one of the plurality of regions containing the vector of the difference; and

compare the first inner product with the second inner product to thereby identify, as the first switching vector, any one of the first and second non-zero vectors based on a result of the comparison.

20. The control system according to claim 3, further comprising:

a determination unit configured to;

calculate a first inner product of the vector of the difference and a first non-zero vector included in the plurality of non-zero vectors;

calculate a second inner product of the vector of the difference and a second non-zero vector included in the plurality of non-zero vectors;

the first and second non-zero vectors separating a set of adjacent two regions included in the plurality of regions and containing the vector of the difference; and

compare the first inner product with the second inner product to thereby identify one of the adjacent two regions that contains the vector of the difference based on a result of the comparison.

21. The control system according to claim 3, further comprising:

a determination unit configured to;

calculate a first inner product of a vector of the direction of change in the difference and a first non-zero vector included in the plurality of non-zero vectors;

calculate a second inner product of the vector of the direction of change in the difference and a second non-zero vector included in the plurality of non-zero vectors;

the first and second non-zero vectors separating a set of adjacent two regions included in the plurality of regions and containing the vector of the difference; and

compare the first inner product with the second inner product to thereby identify one of the adjacent two regions that contains the vector of the direction of change in the difference based on a result of the comparison.

22. The control system according to claim 3, further comprising:

an identifying unit configured to;

calculate a first inner product of the vector of the difference and a first non-zero vector included in the plurality of non-zero vectors;

calculate a second inner product of the vector of the difference and a second non-zero vector included in the plurality of non-zero vectors;

the first and second non-zero vectors separating the one of the plurality of regions containing the vector of the difference; and

compare the first inner product with the second inner product to thereby identify, as the first switching vector, any one of the first and second non-zero vectors based on a result of the comparison and signs of components of the vector of the difference;

a first determining unit configured to;

calculate a third inner product of the vector of the difference and a third non-zero vector included in the plurality of non-zero vectors;

calculate a fourth inner product of the vector of the difference and a fourth non-zero vector included in the plurality of non-zero vectors, the third and fourth non-zero vectors separating a set of adjacent two regions included in the plurality of regions and containing the vector of the difference; and

compare the third inner product with the fourth inner product to thereby identify one of the adjacent two regions that contains the vector of the difference based on a result of the comparison and sign of components of the vector of the difference; and

a second determining unit configured to;

calculate a fifth inner product of a vector of the direction of change in the difference and a fifth non-zero vector included in the plurality of non-zero vectors;

calculate a sixth inner product of the vector of the direction of change in the difference and a sixth non-zero vector included in the plurality of non-zero vectors, the fifth and sixth non-zero vectors separating a set of adjacent two regions included in the plurality of regions and containing the vector of the difference; and

compare the fifth inner product with the sixth inner product to thereby identify one of the adjacent two regions that contains the vector of the direction of change in the difference based on a result of the comparison and signs of components of the vector of the direction of change in the difference,

wherein each of the identifying unit, the first determining unit, and the second determining unit comprises a common logic function, and is configured to individually pass, as arguments, a corresponding vector to be used as the inner product, a corresponding vector to be used as the signs of the components, and corresponding output parameters to the common logic function.

23. The control system according to claim 2, wherein the calculating unit comprises:

a measuring unit configured to measure a value indicative of the direction of change in the difference during the switching mode being set to the zero vector every time the switching mode is set to the zero vector; and

a predicting unit configured to predict, based on the measured value, the direction of change in the difference after next time the switching mode is set to the zero vector.