Methods, systems and apparatus for adjusting modulation index to improve linearity of phase voltage commands
First Claim
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1. A method for adjusting voltage command signals from a current regulator in an electric motor drive system that further comprises a multi-phase machine having machine terminals, the method comprising:
- computing a modulation index and a voltage angle based on voltage command signals provided from the current regulator and a DC input voltage, wherein the voltage angle is computed as a function of the voltage command signals;
generating, via a lookup table, an adjusted modulation index using inputs comprising the modulation index and a phase current that is a function of a d-axis current command and a q-axis current command; and
computing adjusted voltage command signals using the adjusted modulation index, the voltage angle and the DC input voltage,wherein the adjusted voltage command signals cause magnitudes of phase voltage command signals to be adjusted to substantially match applied machine terminal voltages VAN, VBN, VCN that are applied at the machine terminals.
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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.
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Citations
18 Claims
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1. A method for adjusting voltage command signals from a current regulator in an electric motor drive system that further comprises a multi-phase machine having machine terminals, the method comprising:
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computing a modulation index and a voltage angle based on voltage command signals provided from the current regulator and a DC input voltage, wherein the voltage angle is computed as a function of the voltage command signals; generating, via a lookup table, an adjusted modulation index using inputs comprising the modulation index and a phase current that is a function of a d-axis current command and a q-axis current command; and computing adjusted voltage command signals using the adjusted modulation index, the voltage angle and the DC input voltage, wherein the adjusted voltage command signals cause magnitudes of phase voltage command signals to be adjusted to substantially match applied machine terminal voltages VAN, VBN, VCN that are applied at the machine terminals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An electric motor drive system, comprising:
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a DC input voltage; a multi-phase machine having machine terminals; a current regulator; and a voltage command adjustment processor comprising a lookup table, wherein the voltage command processor is designed to; receive voltage command signals from the current regulator; compute a modulation index and a voltage angle based on voltage command signals and the DC input voltage, wherein the voltage angle is computed as a function of the voltage command signals; generate, via the lookup table, an adjusted modulation index using inputs comprising the modulation index and a phase current that is a function of a d-axis current command and a q-axis current command; and compute adjusted voltage command signals using inputs comprising the adjusted modulation index, the voltage angle and the DC input voltage, wherein the adjusted voltage command signals cause magnitudes of phase voltage command signals to be adjusted to substantially match applied machine terminal voltages VAN, VBN, VCN that are applied at the machine terminals. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. In a system comprising an electric motor drive system that comprises a current regulator and a multi-phase electric machine having machine terminals, a method for controlling the multi-phase electric machine, the method comprising:
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computing a modulation index and a voltage angle based on voltage command signals provided from the current regulator and a DC input voltage, wherein the voltage angle is computed as a function of the voltage command signals; generating, via a lookup table, an adjusted modulation index using inputs comprising the modulation index and a phase current that is a function of a d-axis current command and a q-axis current command; computing adjusted voltage command signals using inputs comprising the adjusted modulation index, the voltage angle and the DC input voltage, wherein the adjusted voltage command signals cause magnitudes of phase voltage command signals to be adjusted to substantially match applied machine terminal voltages VAN, VBN, VCN that are applied at the machine terminals; 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 the applied machine terminal voltages VAN, VBN, VCN despite non-linearities in the electric motor drive system. - View Dependent Claims (16, 17, 18)
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Specification