WO2011040663A1

WO2011040663A1 - Electric power quality monitoring system and electric power quality measuring method

Info

Publication number: WO2011040663A1
Application number: PCT/KR2009/006025
Authority: WO
Inventors: 최성훈; 김준일; 박용업
Original assignee: 한국전력공사
Priority date: 2009-09-29
Filing date: 2009-10-19
Publication date: 2011-04-07
Also published as: KR20110035087A; KR101098505B1

Abstract

Disclosed are an electric power quality monitoring system and an electric power quality measuring method. An apparatus for measuring the quality of an electric power system comprises: a pickup unit for acquiring voltage and current waveforms of an electric power system at set time intervals; a sampling unit for sampling and storing the acquired voltage and current waveforms over a set period, for harmonic component analysis; a waveform generator for overlapping and combining voltage and current waveforms sampled over the set sampling period into one cycle, and generating a representative waveform; and a transmitting unit for transmitting the representative waveform via a communication network to a monitoring server.

Description

Power Quality Monitoring System and Power Quality Measurement Method

The present invention relates to power quality measurement of a power system, and more particularly, power that can continuously monitor harmonics corresponding to a power system at a remote location by transmitting sampling data corresponding to the power system to a minimum in a field power quality measuring device. The present invention relates to a quality monitoring system and a power quality measurement method.

Traditionally, power quality was assessed using factors such as voltage, frequency, and power factor. Recently, however, the measurement and management of harmonics generated from non-linear loads has become an important problem with the development of power electronic technology.

The measurement and evaluation of harmonics in the power system is performed by decomposing the voltage and current waveforms of the power system into components of each frequency domain. Real-time transmission to remote sites for analysis was not practical.

The present invention is to provide a power quality monitoring system and power quality measurement method capable of constantly monitoring the harmonics corresponding to the power system.

In addition, the present invention is to provide a power quality monitoring system and a power quality measurement method capable of real-time transmission to a remote monitoring server by reducing the sampling data of voltage and current waveforms measured in the power system.

In addition, the present invention is to provide a power quality monitoring system and a power quality measurement method that can significantly improve the operation speed for harmonic evaluation of the power system due to the reduction of sampling data.

According to one aspect of the invention, there is provided an apparatus for measuring the quality of the power system and a system for monitoring the same.

According to an embodiment of the present invention, an apparatus for measuring the quality of the power system, comprising: a pickup unit for acquiring voltage and current waveforms of the power system at predetermined time intervals; A sampling unit for sampling and storing the acquired voltage and current waveforms at predetermined cycles for harmonic component decomposition; A waveform generator for generating a representative waveform by overlapping and adding the voltage and current waveforms sampled during a specified measurement period in one cycle; And a transmitter for transmitting the representative waveform to a monitoring server through a communication network.

The waveform generator may overlap and sum voltage and current waveforms of the same period among the voltage and current waveforms sampled during the measurement period.

The waveform generator may generate the representative waveform as an average value of waveforms summed in one cycle.

The sampling unit may sample the acquired voltage and current waveforms at a period of 2 ns (where n is a natural number of 7 or more).

The representative waveform is a half period value of the entire period of the superimposed voltage and current waveforms.

According to another embodiment of the present invention, in a power quality monitoring system, a voltage and current waveform of a power system is acquired at predetermined time intervals, sampled and stored at a predetermined period, and the voltage and current waveform sampled during a specified measurement period are stored. A power quality measuring device for generating and transmitting a representative waveform by adding and superimposing one cycle; And a monitoring server receiving the representative waveform from the power quality device and analyzing the received representative waveform according to a predetermined method to monitor occurrence of an event in the power system.

According to another aspect of the invention, there is provided a method for the power quality measuring device to measure the power quality of the power system.

According to an embodiment of the present invention, a method for measuring a power quality of a power system by a power quality measuring apparatus, the method comprising: (a) acquiring voltage and current waveforms of the power system at predetermined time intervals; (b) sampling and storing the obtained voltage and current waveforms at predetermined intervals for high frequency component decomposition; (c) superimposing and summing the voltage and current waveforms sampled during a specified measurement period in one cycle to generate a representative waveform; And (d) transmitting the representative waveform to a monitoring server through a communication network.

Generating the representative waveform in the step (c) is a step of overlapping and summing voltage and current waveforms of the same period among the voltage and current waveforms sampled during the measurement period.

The generating of the representative waveform in the step (c) is the step of generating the representative waveform with an average value of the waveforms summed in one cycle.

In the step (b), the acquired voltage and current waveforms may be 2 n (where n is a natural number of 7 or more).

By providing a power quality monitoring system and a power quality measuring method according to the present invention, it is possible to constantly monitor the harmonics corresponding to the power system.

In addition, the present invention has the advantage that the real-time transmission to the remote monitoring server by reducing the sampling data of the voltage and current waveform measured in the power system.

In addition, the present invention has the advantage that can significantly improve the operation speed for harmonic evaluation of the power system due to the reduction of the sampling data.

1 is a block diagram illustrating a system for monitoring the quality of a power system in accordance with an embodiment of the present invention.

Figure 2 is a block diagram schematically showing the internal configuration of the power quality measurement apparatus according to an embodiment of the present invention.

3 illustrates a sampling waveform for a conventional voltage and current waveform.

4 illustrates a representative waveform corresponding to a voltage and current waveform in accordance with an embodiment of the invention.

5 is a flowchart illustrating a method of measuring power quality by a power quality measuring apparatus according to an exemplary embodiment of the present invention.

6 is a diagram illustrating a result of DFT of each voltage and current waveform and a result of DFT of a representative waveform according to an embodiment of the present invention.

Pickup: 210

Sampling unit: 220

Generator: 230

Storage: 240

Transmitter: 250

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram illustrating a system for monitoring the quality of a power system according to an embodiment of the present invention.

Referring to FIG. 1, a system for monitoring the quality of a power system according to an embodiment of the present invention includes a power quality measuring apparatus 110, a monitoring server 120, and a database 130.

The power quality measuring apparatus 110 is connected to a power system, acquires a voltage or power waveform at predetermined time intervals, samples the same according to a predetermined method, generates a representative waveform using the same, and transmits the generated waveform to the monitoring server 120. It performs the function.

In addition, although FIG. 1 illustrates that one power quality measuring device 110 is connected to the system, a plurality of power quality measuring devices 110 are connected to each power system to display voltage or power waveforms of each power system. The corresponding waveform may be generated and transmitted to the monitoring server 120, respectively.

Hereinafter, detailed functions of the power quality measuring apparatus 110 will be described with reference to the accompanying drawings.

The monitoring server 120 receives a representative waveform from the power quality measuring apparatus 110 in units of preset measurement cycles and registers the representative waveform in the database 130. Subsequently, the monitoring server 120 analyzes the representative waveform according to a predetermined method, analyzes the voltage and power waveform of the corresponding power system, and performs various analysis and evaluation on the power system by performing decomposition of waveforms according to harmonic orders. . Through this, the monitoring server 120 may check the abnormality of the power system.

The database 130 is connected to the monitoring server 120 and stores each representative waveform received from each power quality measuring device 110.

2 is a block diagram schematically showing the internal configuration of a power quality measurement apparatus according to an embodiment of the present invention, Figure 3 is a diagram illustrating a sampling waveform for a conventional voltage and current waveform, Figure 4 is a present invention Representative waveforms corresponding to voltage and current waveforms according to embodiments of the present disclosure.

2, the power quality measuring apparatus 110 according to the exemplary embodiment of the present invention includes a pickup unit 210, a sampling unit 220, a waveform generator 230, a storage unit 240, and a transmitter 250. It is configured to include).

The pickup unit 210 acquires the voltage and current waveforms of the power system to which the power quality measuring device 110 is connected (or coupled) at predetermined time intervals (for example, 1 second, 3 seconds, etc.). do.

Since the method of acquiring the voltage and current waveforms of the power system is obvious to those skilled in the art, a separate description thereof will be omitted.

The sampling unit 220 samples the voltage and current waveforms acquired through the pickup unit 210 at predetermined periods and converts the waveforms into digital waveforms. Here, the sampling unit 220 may sample the voltage and current waveforms acquired through the pickup unit 210 at intervals (n is a natural number of 7 or more).

In the present specification, for convenience of understanding and description, a period in which the sampling unit 220 samples the voltage and current waveforms will be referred to as a sampling period. In general, a sampling period of at least 128 or 256 cycles is required for the decomposition of harmonic components in the frequency domain. Thus, in the present specification, the sampling period is assumed to be 128 or more cycles, but the description will be mainly performed, but may be less than 128 cycles.

The sampling unit 220 stores the voltage and current waveforms sampled according to a designated sampling period in the storage unit 240.

The waveform generator 230 generates a representative waveform by overlapping and adding the sampled voltage and current waveforms in one cycle for a predetermined measurement period.

In the present embodiment, it is assumed that the measurement cycle is the maximum demand period in order to facilitate the understanding and explanation. For example, if the maximum demand period is 15 minutes, the measurement period may be set to 15 minutes. Of course, the measurement period may be set to another period in addition to the maximum demand period, such as 3 minutes, 10 minutes.

For example, the waveform generator 230 may generate the representative waveform by overlapping and summing the sampled voltage and current waveforms in one cycle during the measurement period, and calculating their average values. In addition, the waveform generator 230 may generate a representative waveform by superimposing / summing voltage and current waveforms having the same sampling period with respect to the voltage and current waveforms sampled during the measurement period.

2 illustrates a waveform sampled by a conventional sampling method. The conventional scheme has a very large amount of data on the sampled voltage and current waveforms, which makes it difficult to transmit it to the remote monitoring server 120.

That is, suppose, for example, that the three-phase voltage and current waveforms are sampled at 256 sampling periods. If 92,160 samples are generated per second and accumulate for 15 minutes (i.e., assume a measurement period of 15 minutes), a total of 82,944,000 sampling data is conventionally formed.

As a result, it was virtually impossible for the power quality measuring apparatus 110 to transmit the sampled voltage and current waveforms accumulated during the measurement period to the remote monitoring server 120, and thus, the power quality measuring apparatus connected to each power system. At 110, a signal processor (for example, an FFT converter) should be mounted for harmonic evaluation and analysis using the sampled voltage and current waveforms, and all function modules for outputting the report should be mounted. There was a problem.

However, in the present embodiment, as illustrated in FIG. 3, the power quality measuring apparatus 110 generates a representative waveform by overlapping each cycle into one cycle for each sampled voltage and current waveform, thereby sampling the sampled data. The amount was significantly reduced.

In general, the voltage and current waveforms in the power system do not change rapidly unless an internal or external event occurs such as a power failure, an instantaneous voltage drop, a lightning strike, or a surge due to the opening or closing of a switch.

With this in mind, in the present embodiment, the power quality measuring apparatus 110 may generate a representative waveform for the voltage and current waveforms sampled during the measurement period and transmit the generated waveform to the remote monitoring server 120.

Accordingly, the monitoring server 120 may evaluate the harmonics by calculating sample data corresponding to the half period of the representative waveform received from the power quality measuring apparatus 110.

The storage unit 240 accumulates and stores voltage and current waveforms sampled through the sampling unit 220 during a measurement period. In addition, the storage unit 240 stores an algorithm required to operate the power quality measuring apparatus 110 according to an embodiment of the present invention.

The transmitter 250 transmits the representative waveform generated by the waveform generator 230 to the remote monitoring server 120.

Accordingly, the monitoring server 120 may receive the representative waveform from the power quality measuring apparatus 110 and register it in the database 130.

In addition, the monitoring server 120 may monitor and evaluate the power quality including the harmonics of the power system by analyzing the representative waveform.

5 is a flowchart illustrating a method of measuring power quality by a power quality measuring apparatus according to an exemplary embodiment of the present invention. Each step performed below is performed by each internal component of the power quality measuring apparatus 110, but will be collectively described as a power quality measuring apparatus for the convenience of understanding and explanation.

In operation 510, the power quality measuring apparatus 110 acquires the voltage and current waveforms of the power system to which the power quality measuring apparatus 110 is connected at predetermined time units.

In operation 515, the power quality measuring apparatus 110 samples the acquired voltage and current waveforms at a predetermined sampling period, and stores them. Since this is the same as described above, overlapping description thereof will be omitted.

In operation 520, the power quality measurement apparatus 110 generates a representative waveform by overlapping and summing the sampled voltage and current waveforms in one cycle during the measurement period. For example, the power quality measurement apparatus 110 may overlap and sum the sampled voltage and current waveforms in one cycle, calculate an average thereof, and generate a representative waveform using the same.

In operation 525, the power quality measuring apparatus 110 transmits the generated representative waveform to the remote monitoring server 120.

FIG. 6A is a diagram illustrating discrete Fourier transform (DFT) results for each unit voltage and current waveform, and (B) is a diagram illustrating DFT results for a representative waveform.

As shown in FIG. 6, it can be seen that the DFT conversion of the representative waveforms and the unit waveforms (ie, voltage and current waveforms) during the measurement period are substantially the same. That is, when the sum of the DFT conversion values of the periods for the unit voltage and current waveforms of FIG.

As such, the two results do not match perfectly because the frequency of the power system is not fixed at 60 Hz, and the fluctuations are minute. As a result, the zero crossing of each cycle is not always constant, resulting in minute errors of the two results, but this is a negligible error in the harmonic evaluation of the power system.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art to which the present invention pertains without departing from the spirit and scope of the present invention as set forth in the claims below It will be appreciated that modifications and variations can be made.

It can be used in the power generation industry to monitor power systems and improve their quality.

Claims

In the device for measuring the quality of the power system,

A pickup unit for acquiring voltage and current waveforms of the power system at predetermined time intervals;

A sampling unit sampling and storing the acquired voltage and current waveforms at a predetermined sampling period for harmonic component decomposition;

A waveform generator for generating a representative waveform by overlapping and summing the sampled voltage and current waveforms in one cycle during a specified measurement period; And

And a transmitter for transmitting the representative waveform to a monitoring server through a communication network.
According to claim 1,

And the waveform generating unit overlaps and sums the sampled voltage and current waveforms having the same sampling period.
According to claim 1,

And the waveform generator generates the representative waveform as an average value of waveforms summed in one cycle.
According to claim 1,

The sampling unit
Wherein n is a natural number of 7 or more. The power quality measuring device according to claim 1, wherein the acquired voltage and current waveforms are sampled.
According to claim 1,

The representative waveform is a power quality measuring device, characterized in that the half-period value of the entire period of the superimposed voltage and current waveform.
In the power quality measuring apparatus for measuring the power quality of the power system,

(a) acquiring voltage and current waveforms of the power system at predetermined time intervals;

(b) sampling and storing the obtained voltage and current waveforms at predetermined intervals for high frequency component decomposition;

(c) superimposing and summing the voltage and current waveforms sampled during a specified measurement period in one cycle to generate a representative waveform; And

(d) transmitting the representative waveform to a monitoring server through a communication network.
The method of claim 6,

Generating the representative waveform in the step (c),

Superimposing and summing voltage and current waveforms of the same period among the voltage and current waveforms sampled during the measurement period.
The method of claim 6,

Generating the representative waveform in the step (c),

And generating the representative waveform as an average value of waveforms summed in one cycle.
In step (b),

The obtained voltage and current waveform is
Wherein n is a natural number of 7 or more.
According to claim 1,

The representative waveform is a power quality measurement method, characterized in that the half-cycle value of the entire period of the superimposed voltage and current waveform.
In the power quality monitoring system,

Power quality that acquires the voltage and current waveforms of the power system at predetermined time intervals, samples and stores them at predetermined intervals, and generates and transmits a representative waveform by adding and superimposing the voltage and current waveforms sampled during a specified measurement period in one cycle. Measuring device; And

And a monitoring server receiving the representative waveform from the power quality device, DEF converting the representative waveform, calculating a harmonic evaluation value, and monitoring an occurrence of an event in the power system.
The method of claim 11, wherein

And the power quality measuring device superimposes and sums voltage and current waveforms of the same period among the voltage and current waveforms sampled during the measurement period.
The method of claim 11, wherein

The power quality measuring device generates the representative waveform as the average value of the waveform summed in one cycle.