Systems, methods and apparatuses for frequency tracking

Patent metadata

Field	Value
Publication number	US-2021109158-A1
Application number	US-201916601261-A
Country	US
Kind code	A1
Filing date	Oct 14, 2019
Priority date	Oct 14, 2019
Publication date	Apr 15, 2021
Grant date	—

Abstract

A frequency tracking system may use shaft speed and electrical frequency to estimate a frequency of a monitored machine. The frequency tracking system may convert shaft speed to a mechanical frequency and blend the electrical frequency and the mechanical frequency together to determine an estimated frequency. The frequency tracking system may blend the frequencies based on an operating state of the monitored machine and the frequency sensors.

First claim

What is claimed is:

1 . A frequency tracking system comprising:
a first sensor to monitor shaft speed of a monitored machine; a second sensor to measure stator voltage frequency of the monitored machine; and processing circuitry to:
convert the shaft speed to a shaft-measured frequency;
determine a current operating state of the monitored machine;
blend the stator voltage frequency and the shaft-measured frequency based on the current operating state to determine a system frequency measurement; and
provide the system frequency measurement as an estimated frequency.

2 . The frequency tracking system of claim 1 , wherein to blend the stator voltage frequency and the shaft-measured frequency the processing circuitry is to:
multiply the stator voltage frequency by a factor to obtain a stator product, multiply the shaft-measured frequency by one minus the factor to obtain a shaft product, and sum the stator product and the shaft product, wherein the factor is determined by the current operating state of the monitored machine.

3 . The frequency tracking system of claim 1 , wherein the current operating state includes a transient condition and a fault condition, and
wherein to blend the stator voltage frequency and the shaft-measured frequency the processing circuitry is to:
reduce an influence of the stator voltage frequency on the system frequency measurement during the transient condition and the fault condition.

4 . The frequency tracking system of claim 1 , wherein the current operating state includes a first sensor fault condition and a second sensor fault condition, and
wherein to blend the stator voltage frequency and the shaft-measured frequency the processing circuitry is to:
use the stator voltage frequency during the first sensor fault condition as the system frequency, and
use the shaft-measured frequency during the second sensor fault condition as the system frequency.

5 . The frequency tracking system of claim 4 , wherein the processing circuitry is further to provide a failure alert during the first sensor fault condition and the second sensor fault condition.

6 . The frequency tracking system of claim 1 , wherein the processing circuitry is further to:
blend one or more additional signals with the stator voltage frequency and the shaft-measured frequency to determine a system frequency measurement.

7 . The frequency tracking system of claim 1 , wherein the processing circuitry is further to determine the operating state based on a difference between the stator voltage frequency and the shaft-measured frequency.

8 . A frequency tracking device comprising:
a first input to receive shaft speed data from a first sensor; a second input to receive electrical frequency data from a second sensor; and processing circuitry to:
convert the shaft speed data to a shaft-measured frequency;
determine a current operating state of a monitored machine;
blend the electrical frequency data and the shaft-measured frequency based on the current operating state to determine a system frequency estimate; and
provide the system frequency estimate as an estimated frequency.

9 . The frequency tracking device of claim 8 , wherein to blend the electrical frequency and the shaft-measured frequency the processing circuitry is to:
multiply the electrical frequency by a factor to obtain an electrical product, multiply the shaft-measured frequency by one minus the factor to obtain a shaft product, and sum the electrical product and the shaft product, wherein the factor is determined by the current operating state of the monitored machine.

10 . The frequency tracking device of claim 8 , wherein the current operating state includes a transient condition and a fault condition, and
wherein to blend the electrical frequency and the shaft-measured frequency the processing circuitry is to:
reduce an influence of the electrical frequency on the system frequency estimate during the transient condition and the fault condition.

11 . The frequency tracking device of claim 8 , wherein the current operating state includes a first sensor fault condition and a second sensor fault condition, and
wherein to blend the stator voltage frequency and the shaft-measured frequency the processing circuitry is to:
use the stator voltage frequency during the first sensor fault condition as the system frequency, and
use the shaft-measured frequency during the second sensor fault condition as the system frequency.

12 . The frequency tracking device of claim 11 , wherein the processing circuitry is further to provide a failure alert during the first sensor fault condition and the second sensor fault condition.

13 . The frequency tracking device of claim 8 , wherein the processing circuitry is further to:
blend one or more additional signals with the stator voltage frequency and the shaft-measured frequency to determine a system frequency measurement.

14 . The frequency tracking device of claim 8 , wherein the processing circuitry is further to determine the operating state based on a difference between the stator voltage frequency and the shaft-measured frequency.

15 . A method to track frequency, the method comprising:
receiving shaft speed from a first sensor; converting the shaft speed to a shaft-measured frequency; receiving stator voltage frequency from a second sensor; determining a current operating state of a monitored machine; blending the stator voltage frequency and the shaft-measured frequency based on the current operating state to determine a blended frequency measurement; and provide an estimated frequency based on the blended frequency measurement.

16 . The method of claim 15 , wherein blending comprises:
multiplying the stator voltage frequency by a factor to obtain a stator product; multiplying the shaft-measured frequency by one minus the factor to obtain a shaft product; and summing the stator product and the shaft product, wherein the factor is determined based on the current operating state of the monitored machine.

17 . The method of claim 15 , wherein the current operating state includes a transient condition and a fault condition, and
wherein blending the stator voltage frequency and the shaft-measured frequency comprises:
reducing an influence of the stator voltage frequency on the blended frequency measurement during the transient condition and the fault condition.

18 . The method of claim 15 , wherein the current operating state includes a first sensor fault condition and a second sensor fault condition, and
wherein blending the stator voltage frequency and the shaft-measured frequency comprises:
using the stator voltage frequency during the first sensor fault condition as the blended frequency, and
using the shaft-measured frequency during the second sensor fault condition as the blended frequency

19 . The method of claim 15 , further comprising:
estimating a frequency slip between the shaft-measured frequency and the stator voltage frequency, and correcting a power angle of the shaft-measured frequency using the frequency slip.

20 . The method of claim 15 , wherein determining the operating state is based on a difference between the stator voltage frequency and the shaft-measured frequency.

Assignees

• Schweitzer Engineering Lab Inc

Inventors

• Manson Scott M
• Blood Ellery A
• Zweigle Gregary C

Classifications

• G01D3/02

  with provision for altering or correcting the law of variation · CPC title

• G01P3/487 Primary

  delivered by rotating magnets · CPC title

• G01P3/4802

  by using electronic circuits in general · CPC title

• G01R31/343 Primary

  in operation · CPC title