Convolution integral for synchronized phasor

Patent metadata

Field	Value
Publication number	US-9488681-B2
Application number	US-201213360124-A
Country	US
Kind code	B2
Filing date	Jan 27, 2012
Priority date	Jan 27, 2012
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

Systems, methods, and apparatus for providing a synchronized phasor in power system based on voltage and current measurements, sampling of the voltage and current measurements and convolving the samples with a function.

First claim

The claimed invention is:

1. A method comprising:
receiving an input signal;
providing the input signal to an analog-to-digital converter;
obtaining samples of the input signal by applying a sampling frequency to the analog-to-digital converter;
providing the generated samples to a frequency estimation circuit for deriving a frequency estimate of the input signal;
providing the frequency estimate to a sampling period circuit for generating the sampling frequency that is applied to the analog-to-digital converter;
using a clock signal to provide a timestamp upon each sample of the input signal; and
convolving the timestamped samples of the input signal with a function using corresponding timestamps to generate a synchronized phasor of the input signal.

2. The method of claim 1 , wherein the input signal is a representation of at least one of (i) a voltage of a power element; (ii) a current of a power element; (iii) a resistance of a power element; (iv) real power of a power element; (v) reactive power of a power element; (vi) power factor of a power element; (vii) frequency of a power element; or (viii) a rate of frequency of a power element.

3. The method of claim 1 , wherein the method further comprises filtering the input signal.

4. The method of claim 1 , wherein the clock signal is at least one of (i) a global positioning satellite (GPS) clock signal; (ii) a National Institute of Standards and Technology (NIST) clock signal; (iii) a Global Navigation Satellite System (GLONASS) clock signal; (iv) a Compass Navigation system clock signal; (v) a Galileo positioning system clock signal; or (vi) a Regional Navigational Satellite System clock signal.

5. The method of claim 1 , further comprising post-filtering of the synchronized phasor of the input signal.

6. The method of claim 1 , wherein convolving the samples comprises:
multiplying the timestamped samples of the input signal with a function that comprises a quadrature waveform to generate an output comprising a sum frequency component; and
providing the output to a low pass filter that removes the sum frequency component and outputs the synchronized phasor of the input signal.

7. A phasor measurement unit comprising:
an input port for receiving an analog input signal;
an analog-to-digital converter for obtaining samples of the analog input signal;
a frequency estimation circuit for determining from the generated samples, an estimated frequency of the analog input signal;
a sampling period circuit for deriving from the estimated frequency of the analog input signal, an estimated sampling frequency, wherein the estimated sampling frequency is applied to the analog-to-digital converter for generating the samples of the analog input signal;
a receiver for receiving a clock signal to timestamp each of the samples generated by the analog-to-digital converter; and
at least one circuit to perform a convolution on the samples of the analog input signal with a function using corresponding timestamps to determine a synchronized phasor of the analog input signal.

8. The phasor measurement unit of claim 7 , wherein the analog input signal is a representation of at least one of (i) a voltage of a power element; (ii) a current of a power element; (iii) a resistance of a power element; (iv) real power of a power element; (v) reactive power of a power element; (vi) power factor of a power element; (vii) frequency of a power element; or (viii) a rate of frequency of a power element.

9. The phasor measurement unit of claim 7 , further comprising an input filter for filtering the analog input signal.

10. The phasor measurement unit of claim 7 , wherein the at least one circuit to perform a convolution comprises a multiplier circuit that generates an output comprising a sum frequency component, and a low pass filter that removes the sum frequency component to output the synchronized phasor of the analog input signal.

11. The phasor measurement unit of claim 7 , further comprising a filter for providing phasor measurements based on a local clock.

12. A power distribution system comprising:
at least one voltage or current sensor for sensing at least one voltage or current signal and providing at least one input signal;
at least one phasor measurement unit, each phasor measurement unit comprising:
an input port for receiving the at least one input signal;
a frequency estimating circuit for deriving a frequency estimate of the at least one input signal by using samples of the at least one input signal;
a sampling period circuit for generating a sampling frequency based on the frequency estimate;
at least one analog-to-digital converter to which the sampling frequency is applied for generating the samples of the at least one input signal that are provided to the frequency estimating circuit;
a receiver for receiving a clock signal to timestamp each of the samples of the at least one input signal; and
at least one circuit to perform a convolution on the samples of the at least one input signal with a function using corresponding timestamps to determine a synchronized phasor of the at least one signal.

13. The power distribution system of claim 12 , further comprising an input filter for filtering the input signal.

14. The power distribution system of claim 12 , wherein the at least one circuit to perform a convolution comprises a multiplier circuit and a low pass filter.

15. The power distribution system of claim 12 , wherein the at least one voltage or current sensor comprises four voltage sensors and four current sensors for measuring eight input signals.

16. The power distribution system of claim 15 , wherein the eight input signals comprise a voltage signal and a current signal from each of a first phase line, a second phase line, a third phase line, and a neutral line.

17. The method of claim 1 , wherein convolving the timestamped samples of the input signal comprises:
providing to one input of a multiplier, the timestamped samples (x i , t i ) of the input signal;
providing to a second input of the multiplier, a quadrature signal (e −jw0tk ) comprising a nominal fundamental frequency (w 0 ); and
providing to a filter, an output of the multiplier, the filter configured to output the synchronized phasor of the input signal.

18. The method of claim 17 , wherein the output of the multiplier comprises a sum frequency component, and wherein the filter removes the sum frequency component to output the synchronized phasor of the input signal.

19. The method of claim 18 , wherein the synchronized phasor is a convolution integral.

20. The method of claim 1 , wherein the sampling frequency is a variable sampling frequency that varies in correspondence to the frequency of the input signal.

Assignees

• Korovin Oleksandr
• Voloh Ilia
• Zhang Zhiying
• Mutnuri Sridevi
• Hamour Ihab
• Gen Electric

Inventors

• Korovin Oleksandr
• Voloh Ilia
• Zhang Zhiying
• Mutnuri Sridevi
• Hamour Ihab

Classifications

• Y04S10/265

  Cross-Sectional Technologies · mapped topic

• G01R19/2513 Primary

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

• Y02E60/728

  Cross-Sectional Technologies · mapped topic

• Y02E40/70

  Smart grids as climate change mitigation technology in the energy generation sector · CPC title

• Y04S10/22

  Flexible AC transmission systems [FACTS] or power factor or reactive power compensating or correcting units · CPC title