Motor phase current reconstruction
A system controller for a motor drive system comprising a phase current reconstructor configured to perform operations. The operations comprise receiving a stator current angle and a plurality of phase current sense signals from a plurality of respective devices that in operation drive the motor drive system, selecting, based on the received stator current angle, a reference table from among a plurality of reference tables that store reconstruction scaling factors for respective phase currents, obtaining, from the selected reference table, respective reconstruction scaling factors for the respective phase currents, generating, from the obtained reconstruction scaling factors, respective reconstructed phase current magnitude values for the plurality of devices, and outputting the reconstructed phase current magnitude values.
1. A system controller for a motor drive system with a plurality of devices that are operable to drive a motor, the system controller comprising:
a phase current reconstructor configured to perform operations comprising:
receiving a plurality of phase current sense signals including a respective phase current sense signal from each device of the plurality of devices,
selecting, based on a stator current angle, a reference table from among a plurality of reference tables that store reconstruction scaling factors,
obtaining, from the selected reference table, a respective reconstruction scaling factor for one of the phase currents,
generating, based on the respective reconstruction scaling factor for one of the phase currents, respective reconstructed phase current magnitude values for the plurality of devices, and
outputting the reconstructed phase current magnitude values;
a reference frame translator configured to receive the output reconstructed phase current magnitude values and to generate an alpha-component and a beta-component of a reference frame of the stator;
a stator current angle estimator configured to compute an estimate of the stator current angle in response to the alpha-component and the beta-component, and to provide the estimate of the stator current angle back to the phase current reconstructor; and
a control signal generator configured to generate a set of control signals for the plurality of devices based on the reconstructed phase current magnitude values.
2. The system controller of claim 1 , wherein the phase current reconstructor determines a sector and a sector angle in response to the stator current angle.
3. The system controller of claim 2 , wherein the phase current reconstructor determines an index for the plurality of reference tables, wherein the index is substantially the difference between the stator current angle and the sector angle.
4. The system controller of claim 3 , wherein the plurality of reference tables includes a first reference table, a second reference table, and a third reference table, and wherein the reconstruction scaling factors stored in the first reference table, the second reference table, and the third reference table are responsive to the index.
5. The system controller of claim 4 , wherein the reconstruction scaling factors stored in the first reference table are substantially the sine of the sum of the index and one hundred twenty degrees divided by the sine of the index.
6. The system controller of claim 4 , wherein the reconstruction scaling factors stored in the second reference table are substantially the sine of the difference of the index and one hundred twenty degrees divided by the sine of the index.
7. The system controller of claim 4 , wherein the reconstruction scaling factors stored in the third reference table are substantially the sine of the index divided by the sine of the difference between the index and one hundred twenty degrees.
8. The system controller of claim 3 , wherein the plurality of reference tables includes a first reference table and a second reference table, and wherein the reconstruction scaling factors stored in the first reference table and the second reference table are responsive to the index.
9. The system controller of claim 8 , wherein the reconstruction scaling factors stored in the first reference table are substantially the sine of the sum of the index and sixty degrees divided by the sine of the difference between sixty degrees and the index.
10. The system controller of claim 8 , wherein the reconstruction scaling factors stored in the second reference table are substantially the sine of the index divided by the sine of the sum of the index and sixty degrees.
11. The system controller of claim 1 , wherein the stator current angle estimator comprises a phase-locked loop.
12. The system controller of claim 11 , wherein the stator current angle estimator further comprises:
a first multiplier configured to receive the beta-component and a cosine of the stator current angle and further configured to multiply the beta-component and the cosine of the stator current angle;
a second multiplier configured to receive the alpha-component and a sine of the stator current angle and further configured to multiply the alpha-component and the sine of the stator current angle;
a first arithmetic operator, configured to subtract an output of the second multiplier from an output of the first multiplier;
a first amplifier configured to amplify an output of the first arithmetic operator with a gain Kp;
a second amplifier configured to amplify the output of the first arithmetic operator with a gain Ki;
a first integrator configured to integrate an output of the second amplifier;
a second arithmetic operator configured to receive an output of the first amplifier and an output of the first integrator, wherein the second arithmetic operator adds the output of the first amplifier and the output of the first integrator; and
a second integrator configured to form the estimate of the stator current angle by integrating an output of the second arithmetic operator.
13. The system controller of claim 1 , further comprising a rotor position estimator configured to output a rotor angle representative of an angular position of a rotor flux vector in response to the alpha-component and the beta-component.
14. The system controller of claim 1 , wherein the reference frame translator is configured to further translate the alpha-component and the beta-component to a quadrature-component and a direct-component, and wherein the quadrature-component and the direct-component correspond to a stationary-to-rotating frame transformation of the alpha-component and the beta-component.
15. The system controller of claim 14 , further comprising:
a proportional-integrator control block configured to receive the quadrature-component, the direct-component, and an input representative of a property of the motor, wherein the proportional-integrator control block is configured to output a first control signal to regulate the quadrature-component and a second control signal to regulate the direct-component in response to the property of the motor; and
a second reference frame translator configured to receive the first control signal and the second control signal and output a plurality of control signals, wherein the plurality of control signals corresponds to a transformation of the first control signal and the second control signal from a rotating reference frame to a reference frame associated with the plurality of devices; and
wherein the control signal generator is further configured to regulate the phase current magnitudes through outputting the set of control signals for the plurality of devices in response to the plurality of control signals from the second reference frame translator.
16. The system controller of claim 13 , further comprising:
a proportional-integrator control block configured to receive the rotor angle and an input representative of a property of the motor, wherein the proportional-integrator control block is configured to output a first control signal to regulate a quadrature-component and a second control signal to regulate a direct-component in response to the property of the motor and the rotor angle, wherein the quadrature-component and the direct-component correspond to a stationary-to-rotating frame transformation of the alpha-component and the beta-component; and
a second reference frame translator configured to receive the first control signal and the second control signal and output a plurality of control signals, wherein the plurality of control signals corresponds to a transformation of the first control signal and the second control signal from a rotating reference frame to a reference frame associated with the plurality of devices; and
wherein the control signal generator is further configured to regulate the phase current magnitudes through outputting the set of control signals for the plurality of devices in response to the plurality of control signals from the second reference frame translator.
17. A method for reconstructing a plurality of phase currents of a motor, the method comprising:
receiving a plurality of phase current sense signals including a respective phase current sense signal from each device of a plurality of devices that are operable to drive the motor;
determining a stator current angle, wherein determining the stator current angle comprises estimating the stator current angle from an alpha-component and a beta-component of a stator current vector, the alpha-component and the beta-component being based on reconstructed phase current magnitude values that were generated using one or more reconstruction scaling factors from a plurality of reference tables;
selecting, based on the stator current angle, one or more tables from among the plurality of reference tables;
obtaining a scaling factor from each table of the one or more tables, wherein each obtained scaling factor is a respective reconstruction scaling factor for one of the phase currents;
generating, based on each obtained scaling factor, respective reconstructed phase current magnitude values for the plurality of devices; and
outputting the respective reconstructed phase current magnitude values that were generated for the plurality of devices.
18. The method of claim 17 , wherein selecting, based on the stator current angle, the one or more tables from among the plurality of reference tables comprises:
determining which one of the plurality of phase current sense signals is available; and
selecting the one or more tables based on the stator current angle and the one of the plurality of phase current sense signals that is available.
19. The method of claim 18 , wherein determining which one of the plurality of phase current sense signals is available comprises:
comparing each phase current sense signal of the plurality of phase current sense signals with a respective threshold; and
determining that a phase current sense signal is available if the phase current sense signal is greater than its respective threshold.
20. The method of claim 17 , wherein obtaining a scaling factor from each table of the one or more tables comprises:
determining, based on the stator current angle, a sector from a plurality of sectors of degrees;
determining a sector angle from the determined sector;
determining an index in response to a difference between the stator current angle and the sector angle; and
utilizing the index to obtain the scaling factor from each table of the one or more tables.
21. The method of claim 17 , wherein generating respective reconstructed phase current magnitude values for the plurality of devices comprises:
determining which one of the plurality of phase current sense signals is available; and
multiplying an obtained scaling factor with the determined available phase current sense signal to produce a respective reconstructed phase current magnitude value for one of the plurality of devices.