KR100824515B1 - Apparatus and method for computing digital electricpower system - Google Patents

Abstract

An apparatus and a method for measuring a digital power system are provided to measure exact power fed to external electric devices by reflecting three-phase voltage and three-phase current or neutral line voltage and neutral line current on measurement of voltage, current, and power supplied to the external electric devices. In an apparatus for measuring a digital power system, an input conversion unit(112) detects voltage and current signals supplied to external electric devices(110) and converts and outputs the detected signals into AC(Alternating Current) voltage of analog-digital conversion level. An A/D(Analog To Digital) converter(114) converts the AC voltage of analog-digital conversion level output from the input conversion unit into a digital AC signal and outputs the digital AC signal. An operation unit(116) has a frequency detecting unit(120) directly detecting the frequency of voltage and current supplied to the external electric devices. The operation unit calculates phasor of the digital AC signal by applying the frequency of voltage and current supplied to the external electric devices and detected by the frequency detecting unit, to the digital AC signal output from the A/D converter. An electricity metering unit(118) measures the quantity of electricity supplied to the external electric devices by using the phasor of the digital AC signal computed by the operation unit.

Description

Apparatus and method for computing digital electricpower system}

1 is a block diagram schematically showing a conventional digital power system measuring device.

Figure 2 is a block diagram schematically showing a digital power system measuring apparatus according to an embodiment of the present invention.

3A and 3B are block diagrams schematically illustrating a digital power system measuring apparatus according to another embodiment of the present invention.

4 is a flowchart illustrating a digital power system measuring method according to an exemplary embodiment of the present invention.

<Explanation of symbols for main parts of the drawings>

10, 110: electric device 12, 112: input conversion unit

14, 114: analog-to-digital converter 16, 116: arithmetic unit

18, 118: electric quantity measuring unit 120: frequency detector

122: storage unit

The present invention relates to a digital power system measuring apparatus and method, and more particularly, to a digital power system measuring apparatus and method capable of accurately measuring and protecting power supplied to electrical devices.

With the advent of the digital age, power system measurement devices that measure the voltage, current, and power supplied to electrical devices are also becoming digital.

1 is a block diagram schematically showing a conventional digital power system measurement apparatus.

Referring to FIG. 1, a conventional digital power system measuring device detects signals for three-phase voltage and three-phase current or neutral line voltages PTs and neutral line currents CTs supplied to external electric devices 10. The input converter 12 converts the detected signal into ± 5V AC voltage, which is an analog digital conversion level, and receives the ± 5V AC voltage output from the input converter 12, and converts the signal into a digital AC signal. The analog-to-digital converter 14, the calculator 16 for receiving the digital AC signal output from the analog-to-digital converter 14, and calculating and outputting a pager thereof, and receiving the pager from the calculator 16 and using the same. And an electricity quantity measuring unit 18 measuring voltage, current, and power supplied to the external electrical devices 10.

When the pager is input from the calculator 16, the electric quantity measuring unit 18 considers the input pager as a 60 Hz signal. The electricity meter 18 then measures the voltage, current, and power for the input phaser, which is regarded as a 60 Hz signal.

However, the three-phase voltage and the three-phase current, or the neutral line voltage PTs and the neutral line currents CTs supplied to the external electric devices 10 are signals that vary within a range of a maximum deviation of ± 5 Hz. That is, the three-phase voltage and the three-phase current, or the neutral voltage (PTs) and the neutral current (CTs) supplied to the external electric devices 10 are not always 60 Hz signal, and the input converter 12 outputs. An AC voltage of ± 5 V, which is an analog digital conversion level, a digital AC signal output by the analog-to-digital converter 14, and a pager output by the calculator 16 are not always 60 Hz.

However, the conventional digital power system measuring device regards the pager input to the electric quantity measuring unit 18 as a 60 Hz signal as described above. That is, the conventional digital power system measuring device does not reflect the three-phase voltage and three-phase current, or the neutral line voltage (PTs) and the neutral line current (CTs) fluctuating within the range of the maximum deviation ± 5 Hz to the power measurement.

Accordingly, the conventional digital power system measuring device has a problem that it is not possible to accurately measure the power supplied to the external electrical devices 10, and also cause errors in the setting value of the protective relay element for protection. Can be.

Accordingly, it is an object of the present invention to provide a digital power system measuring device and method thereof capable of accurately measuring voltage, current and power supplied to electrical devices.

In order to achieve the above object, the digital power system measuring device according to an embodiment of the present invention detects the voltage and current signals supplied to the external electrical devices and converts the detected signal into an alternating voltage of analog digital conversion level An input converting unit for outputting; An analog-to-digital converter for converting and outputting an AC voltage, which is the analog-to-digital conversion level, output by the input converter into a digital AC signal; And a frequency detector for directly detecting frequencies of voltages and currents supplied to the external electrical devices, and voltages supplied to the external electrical devices detected by the frequency detector to the digital AC signal output by the analog-to-digital converter. An operation unit configured to calculate and output a pager of the digital AC signal by applying a frequency of a current; And an electricity amount measuring unit configured to measure the amount of electricity supplied to the external electrical devices using the pager of the digital AC signal calculated by the calculating unit.

The frequency detector detects a frequency of a voltage and a current supplied to the external electrical devices with a period.

The digital power system measuring device further includes a storage unit storing a frequency of a voltage and a current supplied to the external electrical devices that the frequency detector periodically detects.

The AC voltage, which is the analog digital conversion level, is a voltage of ± 5V.

Digital power system measurement method according to an embodiment of the present invention comprises the steps of detecting the voltage and current signals supplied to the external electrical devices; Converting the detected voltage and current signals into an alternating voltage which is a digital analog conversion level; Converting an AC voltage which is the digital analog conversion level into a digital AC signal; Detecting a frequency of voltage and current supplied to the external electrical devices; Calculating a pager of the digital AC signal by applying the frequency directly detected from a voltage and a current supplied to the external electrical devices to the digital AC signal; And measuring the amount of electricity supplied to the external electrical devices using the calculated pager of the digital AC signal.

The digital power system measuring method includes: periodically detecting frequencies of voltages and currents supplied to the external electrical devices; Storing the frequency of the voltage and current supplied to the externally detected external devices periodically; And synchronizing in real time a periodic frequency of voltages and currents supplied to the stored external electric devices to the digital AC signal.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 2 to 4.

2 is a block diagram schematically illustrating a digital power system measuring apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the digital power system measuring apparatus according to an exemplary embodiment of the present invention may include a three-phase voltage and a three-phase current or neutral wire voltages PTs and neutral wire currents CTs, etc., supplied to the external electric devices 110. Input converter 112 for converting the detected signal into ± 5V AC voltage, which is an analog digital conversion level, and outputting it, and ± 5V AC voltage, which is an analog digital conversion level output by the input converter 112, An analog-to-digital converter 114 that receives the input and converts it into a digital AC signal, and outputs a digital AC signal that the analog-to-digital converter 114 outputs; Electric quantity measuring unit 118 for receiving the pager of the digital AC signal from the 116 to measure the voltage, current and power supplied to the external electrical devices 110 by using it It is provided. In addition, the digital power system measuring apparatus of the present invention directly detects the three-phase voltage and three-phase current, or the changing frequency of the neutral line voltage (PTs) and the neutral line current (CTs) supplied to the external electrical devices 110. The detector 120 is provided.

The frequency detector 120 is installed in the calculator 116.

When the digital AC signal is input from the analog-to-digital converter 114, the calculation unit 116 supplies three-phase voltages and three-phase voltages to the external electrical devices 110 directly detected by the frequency detector 120. The phaser of the digital AC signal is calculated by applying the current or the frequencies of the neutral line voltages PTs and the neutral line currents CTs.

The calculation unit 116 may be a three-phase voltage and a three-phase current supplied to the external electric devices 110 directly detected by the frequency detector 120 using a Discrete Fourier Transformation equation, which is partially modified by a conventional Discrete Fourier Transformation equation. The phases of the digital AC signal are calculated by applying the varying frequencies of the neutral line voltages PTs and the neutral line currents CTs to the digital AC signal.

The conventional Discrete Fourier Transformation equation is as follows.

As described above, the phaser of the digital AC signal using the conventional Discrete Fourier Transformation equation without considering the frequency is calculated by considering the frequency of the digital AC signal as 60 Hz.

However, in the digital power system measuring apparatus of the present invention, the three-phase voltage and three-phase current or neutral line voltages PTs and the middle line currents CTs supplied to the external electrical devices 110 detected by the frequency detector 120 are provided. In order to calculate the phaser of the digital AC signal by applying the variable frequency of the digital AC signal, the theoretical fundamental wave frequency (60 Hz) and the frequency detector 120 directly detect the conventional Discrete Fourier Transformation equation as described above. It is modified to take into account the varying frequencies of the three-phase voltage and three-phase current, or the neutral line voltages PTs and the neutral line currents CTs, supplied to one external electrical device 110.

The Discrete Fourier Transformation equation of the present invention, which is a modification of the conventional Discrete Fourier Transformation equation, is as follows.

Where N is the number of samples per cycle

        k is the kth sample

        Fs is the theoretical fundamental frequency (60 Hz)

        Freal is a frequency directly detected by the frequency detector 120

The phaser of the digital AC signal using the modified Discrete Fourier Transformation equation as described above can be obtained by cos (θ) of Real-Phase and sin (Imag-Phase) when the frequency detected by the frequency detector 120 is 55Hz. As the value of θ increases, the value of the phaser of the digital AC signal to be calculated becomes smaller as the value of θ increases, and when the frequency (Freal) detected directly by the frequency detector 120 is 65 Hz, cos (θ of Real-Phase) is obtained. ) And the smaller the value of θ in the sin (θ) of Imag-Phase, the shorter the period, the larger the phaser value of the digital AC signal to be calculated.

As such, the phase of the digital AC signal calculated by the calculating unit 116 of the digital power system measuring apparatus of the present invention is supplied to the external electrical devices 110 detected through the frequency detector 120 and the three-phase voltage. When the fluctuating frequency of the current, or the neutral line voltage PTs and the center line current CTs, is smaller than 60 Hz, the voltage becomes smaller, and the three-phase voltage is supplied to the external electric devices 110 detected through the frequency detector 120. And when the fluctuating frequency of the three-phase current, or the neutral line voltage PTs and the middle line current CTs, is greater than 60 Hz.

When the pager of the digital AC signal is input from the calculator 116, the electricity quantity measuring unit 118 measures the voltage, current, and power supplied to the external electric devices 110 using the pager of the digital AC signal. Therefore, the digital power system measuring apparatus according to the embodiment of the present invention measures the fluctuating frequency of three-phase voltage and three-phase current, or neutral voltage (PTs) and neutral current (CTs), which fluctuate within a range of maximum deviation ± 5 Hz. By reflecting the voltage, current, and power supplied to the external electrical devices 110 in the measurement, it is possible to accurately measure the voltage, current, and power supplied to the external electrical devices 110.

In addition, the digital power system measuring device according to an embodiment of the present invention, the protection relay element for the protection of the digital power system measuring device, for example, overcurrent, overvoltage, ground overcurrent, ground overvoltage and undervoltage to the external electrical devices 110 It is possible to better protect the digital power system measuring device by not causing errors in the detected value of.

Referring to the overcurrent of the protective relay elements for the protection of the digital power system measurement device in relation to the protection of the digital power system measurement device, the digital power system measurement device supplies a current of 1.5 A or more to the external electric devices 110. If it is determined as an overcurrent to cut off the current supplied to the external electrical devices (110). However, the conventional digital power system measuring device regards the frequency of the digital AC signal as 60 Hz regardless of the actual frequency of the current supplied to the external electric devices 110 and calculates the phaser of the digital AC signal to exceed the external power of 1.5A. Shut off the current supplied to the electrical devices 110. However, in the digital power system measuring apparatus of the present invention, the three-phase voltage and three-phase current or neutral wire voltages PTs and neutral wire currents CT, etc., which are supplied to the external electric devices 100 detected by the frequency detector 120, may be used. It is possible to better protect the digital power system measuring device by not causing an error in the overcurrent value for the protection of the digital power system measuring device by reflecting the frequency of the signal to the detection of the overcurrent.

Digital power system measuring apparatus according to an embodiment of the present invention is a three-phase voltage and three-phase current, or the three-phase current supplied to the external electrical devices 110 in real time to accurately measure the amount of electricity supplied to the external electrical devices 110, or It is necessary to detect varying frequencies of the neutral line voltages PTs and the neutral line currents CTs. However, the frequency detecting unit 120 detects in real time the changing frequency of the three-phase voltage and three-phase current or neutral wire voltage PTs and neutral wire currents CTs supplied to the external electrical devices 110. Requires skill Accordingly, the frequency detector 120 detects a variable frequency of the three-phase voltage and the three-phase current or the neutral line voltages PTs and the neutral line currents CTs supplied to the external electrical devices 110 with a period. The shorter the frequency detection unit 120 detects a variable frequency of the three-phase voltage and three-phase current supplied to the external electrical devices 110 or the neutral voltage (PTs) and the neutral current (CTs) in real time. Although it is preferable, the frequency detector 120 detects a period in which the frequency of the variable phase of the three-phase voltage and three-phase current or neutral wire voltages PTs and neutral wire currents CTs supplied to the external electrical devices 110 is determined. Shortening requires a high level of skill. Accordingly, the frequency detector 120 may provide a three-phase voltage and a three-phase current or neutral voltage (PTs) supplied to the external electric devices 110 at any one time period within a half cycle to one cycle time based on the fundamental wave. ) And detect the varying frequencies of neutral currents (CTs). In addition, the digital power system measuring device according to an embodiment of the present invention is a three-phase voltage and three-phase current, or the neutral line voltage (PTs) and the neutral line current (CTs) supplied to the external electric devices 110 measured periodically By using the frequency, as shown in FIG. 3A, the storage unit 122a stores the frequency detected by the frequency detector 120 inside the frequency detector 120, or the frequency detector 120 is located inside the calculator 1160. The storage unit 122b stores the frequency detected by the frequency detector 120. The calculation unit 116 of the digital power system measuring apparatus of the present invention directly detects the frequency detected by the frequency detector 120 and stores the frequency 122 in the storage units 122a and 122b. The phaser of the digital AC signal is calculated by applying the frequency of three-phase voltage and three-phase current or neutral voltage (PTs) and neutral current (CTs) supplied to the stored external electrical devices 110 to the digital AC signal. And the present invention The electric power measuring unit 118 of the digital power system measuring device measures the voltage, current, and power supplied to the external electric devices 110 by using the pager of the digital AC signal. The voltage, current, and power supplied to the external electrical devices 110 may be accurately measured.

Hereinafter, a digital power system measuring method according to an embodiment of the present invention using the digital power system measuring apparatus of the present invention will be described with reference to FIG. 4.

Referring to FIG. 4, the digital power system measuring method according to an embodiment of the present invention detects a signal about a three-phase voltage and a three-phase current or a neutral voltage and a neutral current supplied to external electrical devices (S110). A signal is converted into an AC voltage of ± 5V, which is an analog digital conversion level (S120). Subsequently, the ± 5V AC voltage which is an analog digital conversion level is converted into a digital AC signal (S130). Then, the periodic frequency of the three-phase voltage and three-phase current or the neutral voltage and the neutral current supplied to the external electric devices are synchronized in real time and applied to the digital AC signal (S140) to calculate a pager for the digital AC signal. (S150). Then, the voltage, current, and power supplied to the external electric devices are measured using the pager of the digital AC signal (S160).

Digital power system measuring method according to an embodiment of the present invention by applying a frequency directly detected from the three-phase voltage and three-phase current, or the neutral line voltage and the neutral line current supplied to the external electrical devices in step S150 to the digital AC signal In operation S152, frequencies of the three-phase voltage and the three-phase current, or the neutral line voltage and the neutral line current, supplied to the external electrical devices are detected in order to operate on the pager of the digital AC signal. Then, the three-phase voltage and three-phase current supplied to the periodically detected external electrical devices, or the frequency of the neutral voltage and the neutral current (S154) and stores the three-phase voltage and three supplied to the stored external electrical devices Synchronizes the phase current, or the periodic frequency of the neutral voltage and the neutral current in real time, and applies it to the digital AC signal.

As described above, the digital power system measuring apparatus and method according to an embodiment of the present invention is the frequency of three-phase voltage and three-phase current, or neutral voltage (PTs) and neutral current (CTs) supplied to external electrical devices It is provided with a frequency detector for directly detecting. The frequency detection unit directly applies the frequency detected by the frequency detection unit to calculate the phase of the digital AC signal, and measures the power supplied to the external electric devices by using the calculated phaser of the digital AC signal. Accordingly, the digital power system measuring apparatus and method thereof of the present invention measure voltage, current, and power supplied with external electric devices by varying three-phase voltage and three-phase current, or neutral line voltage (PTs) and neutral line currents (CTs). By reflecting this, the power supplied to external electrical devices can be accurately measured. In addition, it is possible to better protect the digital power system measuring device by not generating an error in a setting value of a protective relay element for protecting the digital power system measuring device.

Claims (7)

An input converter configured to detect voltage and current signals supplied to external electric devices and convert the detected signals into an AC voltage which is an analog digital conversion level; An analog-to-digital converter for converting and outputting an AC voltage, which is the analog-to-digital conversion level, output by the input converter into a digital AC signal; And a frequency detector for directly detecting frequencies of voltages and currents supplied to the external electrical devices, and voltages supplied to the external electrical devices detected by the frequency detector to the digital AC signal output by the analog-to-digital converter. An operation unit configured to calculate and output a pager of the digital AC signal by applying a frequency of a current; And an electricity quantity measuring unit configured to measure the quantity of electricity supplied to the external electrical apparatuses by using the pager of the digital AC signal calculated by the computing unit. The method according to claim 1, And the frequency detector detects a frequency of a voltage and a current supplied to the external electrical devices with a period. The method according to claim 2, And a storage unit for storing frequencies of voltages and currents supplied to the external electrical devices that the frequency detector periodically detects. The method according to claim 1, The AC voltage which is the analog-to-digital conversion level is a ± 5V voltage. Detecting voltage and current signals supplied to external electrical devices; Converting the detected voltage and current signals into an alternating voltage which is a digital analog conversion level; Converting an AC voltage which is the digital analog conversion level into a digital AC signal; Detecting a frequency of voltage and current supplied to the external electrical devices; Calculating a pager of the digital AC signal by applying the frequency directly detected from a voltage and a current supplied to the external electrical devices to the digital AC signal; And measuring the amount of electricity supplied to the external electrical devices using the calculated pager of the digital AC signal. The method according to claim 5, Periodically detecting frequencies of voltage and current supplied to the external electrical devices; Storing the frequency of the voltage and current supplied to the external electrical devices periodically detected; And synchronizing in real time a periodic frequency of voltages and currents supplied to the stored external electric devices to the digital AC signal. The method according to claim 5, AC voltage which is the analog-to-digital conversion level is a ± 5V voltage.

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