Method and System for Detecting Transients in Power Grids

• US 20130158903A1
• Filed: 11/15/2012
• Published: 06/20/2013
• Est. Priority Date: 12/19/2011
• Status: Abandoned Application

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Corporation
• Inventors: Sahinoglu, Zafer, Guo, Jianlin, Song, Xiufeng
• Application Number:
  US13/677,752
• Publication Number:
  US 20130158903A1
• Time in Patent Office: Days
• US Class Current: 702/58
• CPC Class Codes: G01R 19/04 Measuring peak values or amplitude or envelope of ac or of pulses
• CPC Class Codes: G01R 19/2506 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 Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: G01R 29/02 Measuring characteristics of individual pulses, e.g. deviation from pulse flatness, rise time or duration
• CPC Class Codes: G01R 31/50 Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections testing of sparking plugs H01T13/58
• CPC Class Codes: G06F 17/18 for evaluating statistical data , e.g. average values, frequency distributions, probability functions, regression analysis forecasting specially adapted for a specific administrative, business or logistic context G06Q10/04
• CPC Class Codes: G06F 17/40 Data acquisition and logging for input to computer G06F3/00
• CPC Class Codes: G16Z 99/00 Subject matter not provided for in other main groups of this subclass

Abstract

Conditions in a power grid are detected by sampling a voltage in the grid. A normal condition hypothesis is modeled as a sinusoid, and a transient condition hypothesis is modeled as a sum of damped sinusoids. The samples are used to construct probability density function. A likelihood ratio based on the pdf and the hypotheses is compared to a threshold to determine whether the condition is normal or transient.

Claims

1. A method for detecting a condition in a power grid, comprising the steps of:

modeling a normal condition hypothesis as a sinusoid, and a transient condition hypothesis as a sum of damped sinusoids;

constructing a probability density function (pdf) from voltage samples in the grid; and

comparing a likelihood ratio based on the pdf and the hypotheses to a threshold to determine the condition, wherein the steps are performed in a processor.

2. The method of claim 1, further comprising:

connecting devices to the grid power according to the condition.

3. The method of claim 1, wherein the voltage is 1-phase or 3-phase.

4. The method of claim 1, further comprising:

analyzing the samples in a stochastic detector to fit the samples to the pdf.

5. The method of claim 1, wherein the samples include normal samples and transient samples, and the normal condition hypothesis is H₀:

y=a₀e, and the transient condition hypothesis is H₁;

y=Ca, where y is a voltage, a is an amplitude, e is a frequency of each normal sample, and C is a full rank Vandermonde matrix of the frequencies, damping factors and sinusoids for the transient samples.

6. The method of claim 5, further comprising:

estimating a₀, a, e, and C using estimation of signal parameters via rotational invariance techniques (ESPRIT).

7. The method of claim 1, wherein the comparing further comprises:

determining a likelihood ratio of the normal pdf and the transient pdf; and

thresholding the likelihood ratio.

8. The method of claim 5, further comprising:

estimating a model order using a maximum description length to obtain the normal condition hypothesis.

9. The method of claim 7, wherein the thresholding is based on a desired probability of false alarm.