VECTOR CONTROLLER FOR PERMANENT-MAGNET SYNCHRONOUS ELECTRIC MOTOR

• US 20100066283A1
• Filed: 10/19/2006
• Published: 03/18/2010
• Est. Priority Date: 10/19/2006
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Corporation
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Kitanaka, Hidetoshi
• Granted Patent: US 7,969,106 B2
• Time in Patent Office: Days
• US Class Current: 318/400.20
• CPC Class Codes: B60L 15/025 using field orientation; Vector control; Direct Torque Control [DTC]
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 50/51 characterised by AC-motors
• 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 21/06 Rotor flux based control involving the use of rotor position or rotor speed sensors
• CPC Class Codes: H02P 27/04 using variable-frequency supply voltage, e.g. inverter or converter supply voltage
• CPC Class Codes: H02P 4/00 Arrangements specially adapted for regulating or controlling the speed or torque of electric motors that can be connected to two or more different electric power supplies vector control H02P21/00
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A method of controlling a current command by comparing voltage with a set value needs to vary the set value depending on voltage fluctuation, which involves taking a complicated control. A vector controller for a permanent-magnet synchronous electric motor, according to the present invention, can realize with a simplified configuration a field-weakening operation in a one-pulse mode in a high speed range by providing a current command compensator that corrects a current command by a corrected current command calculated based on a modulation index.

Claims

1. A vector controller for a permanent-magnet synchronous electric motor that controls an alternating current from an inverter that drives the permanent-magnet synchronous electric motor so as to come into coincidence with a current command, comprising:

a reference phase-angle calculation unit for generating a reference phase angle of the permanent-magnet synchronous electric motor;

a current command generation unit for generating the current command using a given torque command;

a current control unit for making a control calculation of a current error between the current command and a current through the permanent-magnet synchronous electric motor, to output the calculated current error;

a decoupling voltage calculation unit for calculating a feed-forward voltage using motor parameters of the permanent-magnet synchronous electric motor and the current command;

a modulation index calculation unit for outputting a modulation index for the inverter by receiving a direct-current voltage to the inverter and a voltage command that is the sum of the current error and the feed-forward voltage;

a control phase-angle calculation unit for outputting a control phase angle for the inverter by receiving the voltage command and the reference phase angle;

a pulse-width-modulation signal generation unit for generating pulse-width-modulation signals for the inverter using the modulation index and the control phase angle; and

a current command compensator for correcting the current command using a corrected current command calculated based on the modulation index;

wherein

the current command compensator sets the corrected current command to a value obtained by processing through a time delay element and by multiplying by a predetermined constant the difference between the modulation index and a predetermined modulation index set value.

4. The vector controller for a permanent-magnet synchronous electric motor of claim 1, wherein the current command compensator, before multiplying by the predetermined constant the difference between the modulation index and the predetermined modulation index set value, limits the difference to a range between an upper and a lower deviation-limit set values.

5. The vector controller for a permanent-magnet synchronous electric motor of claim 1, wherein the modulation index is defined as having a value of unity when the inverter outputs square waves whose fundamental wave component of line voltage of the inverter reaches a maximum.

6. The vector controller for a permanent-magnet synchronous electric motor of claim 1, wherein the modulation index set value is set to a modulation index by which the inverter outputs square waves whose fundamental wave component of line voltage of the inverter reaches a maximum.

7. The vector controller for a permanent-magnet synchronous electric motor of claim 4, wherein the upper deviation-limit set value is larger than zero and the lower-deviation-limit set value is equal to or smaller than zero.

8. The vector controller for a permanent-magnet synchronous electric motor of claim 4, wherein the upper deviation-limit set value is set based on a maximum field-weakening current necessary for the permanent-magnet synchronous electric motor to generate the command torque within a range of variation in the direct-current voltage to the inverter.

9. The vector controller for a permanent-magnet synchronous electric motor of claim 1, wherein the pulse-width-modulation signal generation unit switches over pulse modes of the inverter depending on the modulation index.

10. The vector controller for a permanent-magnet synchronous electric motor of claim 1, wherein the pulse-width-modulation signal generation unit can hold a carrier signal at zero depending on the modulation index.

11. The vector controller for a permanent-magnet synchronous electric motor of claim 1, further comprising a parameter-error correction unit for calculating, from the current command and the current through the permanent-magnet synchronous electric motor, a control phase-angle correcting value used for correcting the control phase angle.

12. The vector controller for a permanent-magnet synchronous electric motor of claim 11, wherein the control phase-angle correcting value is calculated, by computing the vector control in a rotating coordinate system having a d-axis and a q-axis orthogonal to each other, based on the sum of squares of a d-axis and a q-axis components of the current command, and on that of squares of a d-axis and a q-axis components of the current through the permanent-magnet synchronous electric motor.

13. The vector controller for a permanent-magnet synchronous electric motor of claim 11, wherein the parameter-error correction unit determines whether to make the calculation based on a predetermined signal.

14. The vector controller for a permanent-magnet synchronous electric motor of claim 13, wherein the predetermined signal is the modulation index.

15. The vector controller for a permanent-magnet synchronous electric motor of claim 1, wherein the current control unit determines whether to make the calculation based on a predetermined signal.

16. The vector controller for a permanent-magnet synchronous electric motor of claim 15, wherein the predetermined signal is the modulation index.

17. The vector controller for a permanent-magnet synchronous electric motor of claim 12, wherein the control phase-angle correcting value is calculated by taking a proportional-integral control of the difference between the sum of squares of a d-axis and a q-axis components of the current command, and the sum of squares of a d-axis and a q-axis components of the current through the permanent-magnet synchronous electric motor.

18. The vector controller for a permanent-magnet synchronous electric motor of claim 14, wherein the pulse-width-modulation signal generation unit switches over pulse modes of the inverter depending on the modulation index, and when the modulation index is higher than that corresponding to a lower limit at which a synchronous three-pulse pulse-width-modulation mode is selected for the inverter, the current control unit does not make its calculation and the parameter-error correction unit makes its calculation instead, and when the modulation index is lower than that corresponding to the lower limit at which the synchronous three-pulse pulse-width-modulation mode is selected for the inverter, the current control unit makes its calculation and the parameter-error correction unit does not make its calculation.

2. (canceled)

3. (canceled)