Rotor position estimation apparatus and methods

• US 9,774,284 B2
• Filed: 02/19/2015
• Issued: 09/26/2017
• Est. Priority Date: 02/19/2015
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Rockwell Automation, Inc.)
• Inventors: Liu, Jingbo, Nondahl, Thomas, Schmidt, Peter B., Matsuo, Takayoshi, Rowan, Timothy M.
• Primary Examiner(s): Dhakal, Bickey
• Application Number:
  US14/625,860
• Publication Number:
  US 20160248354A1
• Time in Patent Office: 950 Days
• Field of Search: 318599
• CPC Class Codes: H02P 21/18 Estimation of position or speed
• CPC Class Codes: H02P 27/08 with pulse width modulation
• CPC Class Codes: H02P 6/18 without separate position detecting elements

Abstract

Motor drives, methods and estimation systems are presented for estimating a rotor position of a motor load in which four sets of inverter output current samples obtained at four different sample times in a given inverter PWM cycle are converted into a corresponding stationary reference frame current value pairs, and the rotor position estimate is computed according to the stationary reference frame current values.

Claims

1. An estimation system for estimating a rotor position of a motor load driven by an inverter, wherein the estimation system:

converts each of four sets of multiphase inverter output current samples obtained at four different sample times in a given inverter pulse width modulation cycle into a corresponding pair of stationary reference frame current values, the given inverter pulse width modulation cycle having a duration equal to a complete cycle of a carrier waveform used in generating pulse width modulated switching signals to control an output of the inverter, and

computes an estimated rotor position for the given inverter pulse width modulation cycle according to the stationary reference frame current values for the given inverter pulse width modulation cycle;

wherein the four sets of multiphase inverter output current samples are sampled by the estimation system approximately at peaks, valleys and mid-points of one of a plurality of phase shifted carriers used to operate the inverter in the given inverter pulse width modulation cycle wherein a control circuit implements closed loop control of the inverter to control operation of the motor load at least partially according to the estimated rotor position.

2. The estimation system of claim 1, wherein the four sets of multiphase inverter output current samples are sampled approximately at 90°

intervals in the given inverter pulse width modulation cycle.

3. The estimation system of claim 1, wherein the estimation system:

computes the estimated rotor position θ

for the given inverter pulse width modulation cycle according to α

-β

stationary reference frame current value pairs i<sub>α

i</sub> and i<sub>β

i</sub> for the four sample times (t₁, t₂, t₃ and t₄) according to the following equation;

4. The estimation system of claim 3, wherein the four sets of multiphase inverter output current samples are sampled approximately at 90°

intervals in the given inverter pulse width modulation cycle.

5. A motor drive, comprising:

a multiphase inverter comprising a plurality of inverter switching devices individually coupled between an inverter DC input and a multiphase inverter AC output;

a controller providing pulse width modulated switching control signals to the inverter switching devices of each inverter output phase according to a corresponding one of a plurality of X carriers in each of a plurality of inverter pulse width modulation cycles to convert DC power into multiphase AC output power to drive an associated motor load, each carrier being phase shifted by a non-zero angle 360°

/X relative to one another, X being an integer number of inverter output phases of the multiphase inverter; and

at least one processor operative to;

convert each of four sets of multiphase inverter output current samples obtained at four different sample times in a given inverter pulse width modulation cycle into a corresponding pair of stationary reference frame current values, the given inverter pulse width modulation cycle having a duration equal to a complete cycle of a carrier waveform used in generating pulse width modulated switching signals to control an output of the inverter, and

compute an estimated rotor position associated with the motor load for the given inverter pulse width modulation cycle according to the stationary reference frame current values for the given inverter pulse width modulation cycle;

wherein the four sets of multiphase inverter output current samples are sampled by the at least one processor approximately at peaks, valleys and mid-points of one of a plurality of one of the carriers in the given inverter pulse width modulation cycle wherein the at least one processor is operative to implement closed loop control of the inverter to control operation of the motor load at least partially according to the estimated rotor position.

6. The motor drive of claim 5, wherein the four sets of multiphase inverter output current samples are sampled approximately at 90°

intervals in the given inverter pulse width modulation cycle.

7. The motor drive of claim 5, wherein the at least one processor is operative to:

compute the estimated rotor position θ

for the given inverter pulse width modulation cycle according to α

-β

stationary reference frame current value pairs i<sub>α

i</sub> and i<sub>β

i</sub> for the four sample times (t₁, t₂, t₃ and t₄) according to the following equation;

8. A method for estimating a rotor position of a motor load driven by an inverter, the method comprising:

sampling four sets of multiphase inverter output current samples at four different sample times in a given inverter pulse width modulation cycle approximately at peaks, valleys and mid-points of one of a plurality of phase shifted carriers used to operate the inverter in the given inverter pulse width modulation cycle, the given inverter pulse width modulation cycle having a duration equal to a complete cycle of a carrier waveform used in generating pulse width modulated switching signals to control an output of the inverter;

using at least one processor, converting each of the four sets of multiphase inverter output current samples into a corresponding pair of stationary reference frame current values; and

using the at least one processor, computing an estimated rotor position for the given inverter pulse width modulation cycle according to the stationary reference frame current values for the given inverter pulse width modulation cycle and implementing closed loop control of the inverter to control operation of the motor load at least partially according to the estimated rotor position.

9. The method of claim 8, comprising sampling the four sets of multiphase inverter output current samples approximately at 90°

intervals in the given inverter pulse width modulation cycle.

10. The method of claim 8, comprising:

computing the estimated rotor position θ

for the given inverter pulse width modulation cycle according to α

-β

stationary reference frame current value pairs i<sub>α

i</sub> and i<sub>β

i</sub> for the four sample times (t₁, t₂, t₃ and t₄) according to the following equation;

11. The method of claim 10, comprising sampling the four sets of multiphase inverter output current samples approximately at 90°

intervals in the given inverter pulse width modulation cycle.

12. A non-transitory computer readable medium with computer executable instructions for estimating a rotor position of a motor load driven by an inverter, comprising computer executable instructions for:

sampling four sets of multiphase inverter output current samples at four different sample times in a given inverter pulse width modulation cycle approximately at peaks, valleys and mid-points of one of a plurality of phase shifted carriers used to operate the inverter in the given inverter pulse width modulation cycle, the given inverter pulse width modulation cycle having a duration equal to a complete cycle of a carrier waveform used in generating pulse width modulated switching signals to control an output of the inverter;

converting each of the four sets of multiphase inverter output current samples into a corresponding pair of stationary reference frame current values; and

computing an estimated rotor position for the given inverter pulse width modulation cycle according to the stationary reference frame current values for the given inverter pulse width modulation cycle and implementing closed loop control of the inverter to control operation of the motor load at least partially according to the estimated rotor position.