Current sensor error compensation method

Patent metadata

Field	Value
Publication number	US-10539596-B2
Application number	US-201715850988-A
Country	US
Kind code	B2
Filing date	Dec 21, 2017
Priority date	Dec 21, 2017
Publication date	Jan 21, 2020
Grant date	Jan 21, 2020

Abstract

A system and method are provided to perform current sensor error compensation. The system and method involve obtaining a current measurement of a current on a circuit from a current sensor; obtaining a voltage measurement of a voltage associated with the current from a voltage sensor; determining a fundamental frequency of the voltage from the voltage measurement; and performing error compensation on the current measurement based on the determined fundamental frequency to produce a corrected current measurement. The current sensor error compensation may be performed to correct current measurements in a motor system, such as in a motor overload relay, at a low cost by using functionality already available in the system.

First claim

The invention claimed is:

1. A computer-implemented method of performing current sensor error compensation, the method comprising:
obtaining a current measurement of a current on a circuit from a current sensor;
obtaining a voltage measurement of a voltage associated with the current from a voltage sensor;
determining a fundamental frequency of the voltage from the voltage measurement; and
performing error compensation on the current measurement, comprising: determining a compensation factor based on the determined fundamental frequency, and applying the compensation factor to the current measurement to produce a corrected current measurement.

2. The computer-implemented method of claim 1 , wherein the determining operation comprises:
determining a time period for a voltage waveform associated with the voltage measurement; and
determining the fundamental frequency based on the time period.

3. The computer-implemented method of claim 2 , wherein the circuit is supplied by a poly-phase power supply, the method further comprising:
generating the voltage waveform based on the voltage measurement of only two voltage phases from a plurality of voltage phases.

4. The computer-implemented method of claim 1 , wherein the voltage sensor comprises a capacitor plate to measure the voltage on the circuit using capacitive coupling.

5. The computer-implemented method of claim 1 , further comprising:
digitally integrating an output from the current sensor with a digital integrator to produce the current measurement.

6. The computer-implemented method of claim 1 , further comprising:
controlling circuit protection for the circuit according to the corrected current measurement.

7. The computer-implemented method of claim 1 , wherein the circuit is a motor circuit to supply power to a motor.

8. The computer-implemented method of claim 1 , wherein the corrected current measurement is produced by summing the current measurement and the compensation factor.

9. The computer-implemented method of claim 1 , wherein the determining a compensation factor operation determines the compensation factor by using a look-up table of compensation factors corresponding to a plurality of frequencies or an equation reflecting error compensation as a function of frequency.

10. A system for performing current sensor error compensation comprising:
a memory; and
a processor configured:
to obtain a current measurement of a current on a circuit from a current sensor,
to obtain a voltage measurement of a voltage associated with the current from a voltage sensor,
to determine a fundamental frequency of the voltage from the voltage measurement, and
to perform error compensation on the current measurement, by determining a compensation factor based on the determined fundamental frequency, and applying the compensation factor to the current measurement to produce a corrected current measurement.

11. The system of claim 10 , wherein, to determine a fundamental frequency, the processor is configured:
to determine a time period for a voltage waveform associated with the voltage measurement; and
to determine the fundamental frequency based on the time period.

12. The system of claim 11 , wherein the circuit is supplied by a poly-phase power supply, the processor is further configured:
to generate the voltage waveform based on the voltage measurement of only two voltage phases from a plurality of voltage phases.

13. The system of claim 10 , wherein the voltage sensor comprises a capacitor plate to measure the voltage on the circuit using capacitive coupling.

14. The system of claim 10 , wherein the processor is further configured to digitally integrate an output from the current sensor to produce the current measurement.

15. The system of claim 10 , wherein the processor is further configured to control circuit protection for the circuit according to the corrected current measurement.

16. The system of claim 10 , wherein the circuit is a motor circuit to supply power to a motor.

17. The system of claim 10 , wherein the corrected current measurement is produced by summing the current measurement and the compensation factor.

18. The system of claim 10 , wherein the processor is configured to determine the compensation factor by using a look-up table of compensation factors for a plurality of frequencies or an equation reflecting error compensation as a function of frequency.

19. A tangible memory medium storing computer executable code, which when executed by a processor, implements a method of performing current sensor error compensation, the method comprising:
obtaining a current measurement of a current on a circuit from a current sensor;
obtaining a voltage measurement of a voltage associated with the current from a voltage sensor;
determining a fundamental frequency of the voltage from the voltage measurement; and
performing error compensation on the current measurement, comprising: determining a compensation factor based on the determined fundamental frequency, and applying the compensation factor to the current measurement to produce a corrected current measurement.

Assignees

• Schneider Electric Usa Inc

Inventors

• Jefferies Kevin M
• Edwards Benjamin W
• White Matthew L
• Freeman Alan E

Classifications

• G01R15/18

  using inductive devices, e.g. transformers · CPC title

• G01R19/2513

  Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging · CPC title

• G01R23/02

  Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage · CPC title

• G01R19/2506 Primary

  Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values (G01R19/003 takes precedence); Details concerning sampling, digitizing or waveform capturing (displaying waveforms G01R13/00; analog sampling G01R19/0053) · CPC title