METHODS, SYSTEMS AND APPARATUS FOR ADJUSTING MODULATION INDEX TO IMPROVE LINEARITY OF PHASE VOLTAGE COMMANDS

• US 20130033206A1
• Filed: 08/03/2011
• Published: 02/07/2013
• Est. Priority Date: 08/03/2011
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations LLC (General Motors Company)
• Inventors: GALLEGOS-LOPEZ, GABRIEL, PERISIC, MILUN, KINOSHITA, MICHAEL H.
• Granted Patent: US 9,595,902 B2
• Time in Patent Office: Days
• US Class Current: 318/400.02
• CPC Class Codes: H02P 21/14 Estimation or adaptation of machine parameters, e.g. flux, current or voltage
• CPC Class Codes: H02P 21/18 Estimation of position or speed

Abstract

Embodiments of the present invention relate to methods, systems and apparatus for controlling operation of a multi-phase machine in a motor drive system. The disclosed embodiments provide a mechanism for adjusting modulation index of voltage commands to improve linearity of the voltage commands.

Claims

1. A method for adjusting voltage command signals from a current regulator in an electric motor drive system, the method comprising:

computing a modulation index based on the voltage command signals;

generating an adjusted modulation index based on the modulation index; and

computing adjusted voltage command signals based on the adjusted modulation index.

2. A method according to claim 1, wherein the step of computing a modulation index based on the voltage command signals, comprises:

computing a modulation index and a voltage angle based on the voltage command signals and a DC input voltage.

3. A method according to claim 2, wherein the step of computing adjusted voltage command signals based on the adjusted modulation index, comprises:

computing adjusted voltage command signals based on the adjusted modulation index, the voltage angle and the DC input voltage.

4. A method according to claim 1, wherein the step of generating an adjusted modulation index based on the modulation index comprises:

generating an adjusted modulation index based on the modulation index and a phase current.

5. A method according to claim 1, wherein the multi-phase machine comprises machine terminals, the method further comprising:

generating stationary reference frame voltage command signals by performing a dq-to-α

β

transformation on the adjusted voltage command signals;

generating phase voltage command signals based on the stationary reference frame voltage command signals;

generating switching vector signals based on the phase voltage command signals;

generating three-phase alternating current voltage signal waveforms based on switching vector signals and a DC input voltage; and

applying the three-phase alternating current voltage signal waveforms to the machine terminals, wherein the adjusted voltage command signals cause magnitudes of the phase voltage command signals to be adjusted to substantially match applied machine terminal voltages V_AN, V_BN, V_CN despite non-linearities in the electric motor drive system.

6. A method according to claim 1, wherein the voltage command signals comprise a synchronous reference frame d-axis voltage command signal and a synchronous reference frame q-axis voltage command signal, and wherein the adjusted voltage command signals comprise an adjusted synchronous reference frame d-axis voltage command signal and an adjusted synchronous reference frame q-axis voltage command signal.

7. A method according to claim 1, wherein the adjusted modulation index is used to adjust the voltage command signals and generate the adjusted voltage command signals so that the applied machine terminal voltages V_AN, V_BN, V_CN substantially match the phase voltage command signals.

8. An electric motor drive system, comprising:

a current regulator; and

a voltage command adjustment processor that is designed to receive voltage command signals from the current regulator, and to generate an adjusted modulation index that is used to compute adjusted voltage command signals.

9. An electric motor drive system according to claim 8, wherein the voltage command adjustment processor comprises:

a modulation index computation module designed to receive voltage command signals from the current regulator, and to compute a modulation index based on the voltage command signals;

a modulation index lookup table designed to generate an adjusted modulation index based on the modulation index; and

a voltage command adjustment module designed to compute adjusted voltage command signals based on the adjusted modulation index.

10. An electric motor drive system according to claim 9, wherein the modulation index computation module is further designed to compute the modulation index and a voltage angle based on the voltage command signals and a DC input voltage.

11. An electric motor drive system according to claim 10, wherein the voltage command adjustment module is further designed to compute the adjusted voltage command signals based on the adjusted modulation index, the voltage angle and the DC input voltage.

12. An electric motor drive system according to claim 9, wherein the modulation index lookup table is designed to generate an adjusted modulation index based on the modulation index and a phase current.

13. An electric motor drive system according to claim 8, further comprising:

a synchronous-to-stationary transformation module that generates stationary reference frame voltage command signals by performing a dq-to-a p transformation on the adjusted voltage command signals;

an α

β

-to-abc transformation module that receives the stationary reference frame voltage command signals, and generates phase voltage command signals;

a pulse width modulation module that generates switching vector signals based on the phase voltage command signals;

an inverter module that generates three-phase alternating current voltage signal waveforms based on switching vector signals and a DC input voltage; and

a multi-phase machine comprising machine terminals, wherein the multi-phase machine is coupled to the inverter module and the three-phase alternating current voltage signal waveforms are applied to the machine terminals,

wherein the adjusted voltage command signals cause magnitudes of the phase voltage command signals to be adjusted to substantially match applied machine terminal voltage V_AN, V_BN, V_CN despite non-linearities in the multi-phase machine and the inverter module.

14. An electric motor drive system according to claim 8, wherein the voltage command signals comprise a synchronous reference frame d-axis voltage command signal and a synchronous reference frame q-axis voltage command signal, and wherein the adjusted voltage command signals comprise an adjusted synchronous reference frame d-axis voltage command signal and an adjusted synchronous reference frame q-axis voltage command signal.

15. An electric motor drive system according to claim 8, wherein the adjusted modulation index is used to adjust the voltage command signals and generate the adjusted voltage command signals so that the applied machine terminal voltages V_AN, V_BN, V_CN substantially match the phase voltage command signals.

16. In a system comprising a multi-phase electric machine having machine terminals and an electric motor drive system, a method for controlling the multi-phase electric machine, the method comprising:

computing a modulation index and a voltage angle based on voltage command signals provided from a current regulator and a DC input voltage;

generating an adjusted modulation index based on the modulation index;

computing adjusted voltage command signals based on the adjusted modulation index, the voltage angle and the DC input voltage;

generating switching vector signals based on adjusted voltage command signals, and then generating three-phase alternating current voltage signal waveforms based on switching vector signals and the DC input voltage; and

applying the three-phase alternating current voltage signal waveforms to the machine terminals, wherein the adjustments applied to the voltage command signals to generate the adjusted voltage command signals cause magnitudes of the phase voltage command signals to be adjusted to substantially match applied machine terminal voltages V_AN, V_BN, V_CN despite non-linearities in the electric motor drive system.

17. A method according to claim 16, wherein the step of generating an adjusted modulation index based on the modulation index comprises:

generating an adjusted modulation index based on the modulation index and a phase current.

18. A method according to claim 16, wherein the voltage command signals comprise a synchronous reference frame d-axis voltage command signal and a synchronous reference frame q-axis voltage command signal, and wherein the adjusted voltage command signals comprise an adjusted synchronous reference frame d-axis voltage command signal and an adjusted synchronous reference frame q-axis voltage command signal.

19. A method according to claim 16, wherein the adjusted modulation index is used to adjust the voltage command signals and generate the adjusted voltage command signals so that applied machine terminal voltages V_AN, V_BN, V_CN substantially match the phase voltage command signals.