KR20110046754A - Apparatus for Synchronized Phasor Measurement Unit Using The Re-sampling Technique - Google Patents

Abstract

PURPOSE: An apparatus for measuring synchronized phasor by applying a re-sampling method is provided to calculate the phase and size of a phasor of a current and a voltage even through a system frequency is out of 60 Hz. CONSTITUTION: A synchronous clock generator(110) outputs a time-synchronized sampling counter signal and a GPS second with regard to a sampling counter signal. An A/D converter(140) receives the sampling counter signal and samples an analog signal. A re-sampling unit(160) down-samples the sampled signal of the A/D converter. A phasor calculator(170) calculates the down-sampled signal with the phasor.

Description

Apparatus for Synchronized Phasor Measurement Unit Using The Re-sampling Technique}

The present invention relates to a time-synchronized phasor measuring device to which the resampling technique is applied. More specifically, the resampling technique is applied to a phasor measuring unit (PMU) so that the voltage and the current can be changed regardless of the system frequency. The present invention relates to a time-synchronized phaser measuring device and a method to which a resampling technique for calculating an accurate phaser value is applied.

Modern electric power system is getting bigger and bigger as the demand of electric power is increasing, and load and equipment elements of sensitive and various characteristics are geographically wide and complicated. Therefore, it is very difficult to closely monitor and operate the power system.

In order to improve the reliability of such a power system, research on real-time global monitoring and stability control is required. With the development of visual synchronization technology, a monitoring control system using a phaser measurement unit is an effective alternative to this requirement. Is being presented.

That is, the Synchronized Phasor Measurement Unit is installed in the power system to measure the magnitude and phase angle of the voltage and current, which are the state variables of the system, and to monitor the system's synchronous disengagement, voltage stability, and microsignal stability. The measured data is used for system operation, system control and system disturbance analysis.

The device for measuring time-synchronized phaser, Cho, Sun-Hoon, Heo Moon-Joon, Chae Myung-Seok, Shin, Shin-Rin, Department of Electrical Engineering, Konkuk University, Gunjang Institute of Technology, Implementation of EMTP Model for Synchronous Phase-Measuring Device using GPS, The Korean Institute of Electrical Engineers 1999. 7 19-21 (p1262-p1266) and US Pat. No. 7,480,580 and the like describe the construction or the operating principle thereof.

The conventional phase measuring apparatus PMU calculates a pager using a Discrete Fourier Transform (DFT) algorithm, and uses data obtained by sampling an analog signal into a digital signal at a fixed time.

The data sampled at a fixed time provides a correct phase and magnitude of the voltage and current in the DFT algorithm in a steady state, but the accuracy is significantly degraded in a transient state.

In particular, when the system frequency is greatly deviated from 60 Hz, the conventional PMU device has a problem in that accuracy of phase and magnitude of voltage and current is further reduced.

Recently, a method of compensating a phase and magnitude in which an error occurs by measuring the grid frequency has been proposed to compensate for this problem. However, since the grid frequency is estimated, the accuracy is not greatly improved.

Alternatively, a complex equation is proposed to compensate for the case where the system frequency is out of 60 Hz, but if the system frequency is significantly out of 60 Hz, ie more than 1 Hz out of 60 Hz, Accuracy is not greatly improved.

Fig. 1 shows the waveforms of the generator terminal voltage 2 and the frequency 1 measured by applying a phase measurement device (PMU) algorithm according to the prior art when the breaker is opened with the output at 200 MW in a 1200 MVA nuclear power generator.

Referring to Figure 1, it can be seen that after the breaker is opened, the generator frequency 1 rises to reach 60.8 Hz. At this time, the measured terminal voltage (2) is normally measured when the system frequency is 60 Hz, and shows that the frequency oscillates as the frequency deviates from 60 Hz, which is a PMU algorithm according to the prior art. It is shown that this phenomenon occurs when the system frequency deviates significantly from 60 Hz. Although only the magnitude of the terminal voltage is shown in FIG. 1, the phase value is also incorrect. In this case, the frequency measurement is a value measured through the frequency / voltage converter (f / V converter) of the frequency of the generator terminal voltage.

The present invention has been proposed to solve the problems of the prior art, and the resampling technique is applied to enable the resampling technique to calculate the correct phaser phase and magnitude of voltage and current even when the system frequency deviates from 60 Hz. It is an object of the present invention to provide a synchronous pager measuring apparatus and method thereof.

In addition, another object of the present invention is an apparatus and method for measuring time-synchronized phaser using a resampling technique to increase power system reliability such as power failure prevention by performing reliable system operation, accurate system control, and disturbance analysis. To provide.

As a means for solving the above problem, the time-synchronized phaser measuring apparatus to which the resampling technique according to the present invention is applied is a time-synchronized sampling apparatus for synchronizing phaser measuring an analog signal of PT voltage and CT current measured in a system. A synchronous clock generator for outputting a GPS second for a counter signal and the sampling counter signal; An A / D converter receiving the sampling counter signal and sampling the analog signal; A resampling unit for down sampling the signal sampled by the A / D converter; And a pager calculator configured to calculate a down sampled signal by the resampling unit as a pager.

The synchronization clock generation unit may include: a GPS clock time-synchronized with 1PPS and an IRIG-B signal received from a GPS; A local clock for generating the sampling counter signal and outputting the sampling counter signal to the A / D converter; And a GPS second sampling unit configured to receive a sampling signal from the measuring instrument real-time clock and output the GPS seconds to the pager calculator.

The phaser calculator may calculate the downsampled signal as a pager using a Discrete Fourier Transform (DFT) algorithm and time stamp the GPS seconds using the GPS seconds.

In addition, the time-synchronized phaser measuring device, and receives an analog signal of the PT voltage and CT current to filter the harmonics and noise, and to output the filtered analog signal to the A / D converter and a Butterworth filter (Butterworth Filter) The same analog filter may be further included.

The apparatus for measuring time synchronization phaser further includes a frequency / voltage (f / V) converter which receives the signal filtered by the analog filter and converts a system frequency of the analog voltage into a voltage and outputs the voltage to the A / D converter. can do.

The apparatus for measuring time synchronization phaser further removes noise of a signal sampled by the A / D converter, filters a system frequency used as a sampling frequency of the downsampling, and provides a system frequency filter provided to the resampling unit. It may include.

In addition, the resampling unit may down-sample by Lagrange interpolation.

As another means for solving the above-mentioned problems, the time-synchronized phaser measuring method to which the resampling technique according to the present invention is applied, in the method for measuring the synchronous phaser on an analog signal of PT voltage and CT current measured in a system ( a) filtering harmonics and noise of the analog signal (S10); (b) sampling (S20) the signal filtered in the step (a) by a time-synchronized sampling counter signal; (c) down sampling the signal sampled in the step (b) (S30); And (d) calculating the down-sampled signal in step (c) into a pager by a Discrete Fourier Transform (DFT) algorithm (S40).

The apparatus and method for synchronizing time-phased phaser with the resampling technique according to the present invention having the above-described configuration have an effect of accurately calculating phaser values of voltage and current to be measured even when the system frequency varies greatly from 60 Hz to 1 Hz or more. .

In addition, by providing accurate voltage and current pager data in the transient state as well as in the steady state, there is an effect of improving the reliability of the system operation and control system.

In addition, accurate pager data can be calculated to derive accurate numerical parameters of power generation facilities regardless of system frequency fluctuations, thereby preventing power failure and improving system stability.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may appropriately define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention based on the principle that the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and the same reference numerals will be used for components having the same functions and functions when describing the embodiments of the present invention.

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

2 is a block diagram of an apparatus 100 for measuring time synchronization pagers according to an exemplary embodiment of the present invention.

The time-synchronized phaser measuring unit (PMU) 100 according to the present invention is a phaser measuring apparatus which visually synchronizes an analog signal of PT (Petential Transformer) voltage and CT (Current Transformer) current measured in a system. As shown in FIG. 1, a synchronous clock generator 110, an A / D converter 140, a resampling unit 160, and a pager calculating unit 160 are provided.

The synchronous clock generator 110 generates a time-synchronized sampling counter signal and outputs a GPS second corresponding to the sampling counter signal.

In more detail, the synchronous clock generator 110 is a means for performing a function of generating a time-synchronized signal by mounting a GPS receiver for receiving a GPS signal, as shown in FIG. 4. , 111), a real time clock 112, and a GPS second sampling unit 113.

The GPS clock 111 is a time-synchronized device with 1PPS (Pulse Per Second) and IRIG (Inter-Range Instrumentation Group) -B signals received from a GPS receiver, and has an oscillator and a counter.

The instrument real time clock 112 outputs the sampling counter signal to the A / D converter 140, and the A / D converter 140 receives the sampling counter signal to sample an analog signal.

The GPS second sampling unit 113 receives a sampling signal from the measuring instrument real-time clock 112 and outputs a GPS second to the pager calculator. In this case, the GPS second time is used when time stamping the data measured by the pager operator 170.

The A / D converter 140 receives the sampling counter signal from the synchronous clock generator 110 and performs sampling of the analog signals of the PT voltage and the CT current.

The resampling unit 160 performs resampling, that is, downsampling, on a signal sampled by the A / D converter 140.

In this case, the resampling unit 160 applies a down-sampling technique using a linear or second or higher Lagrange interpolation method or another interpolation method.

The pager calculator 170 calculates the down-sampled signal from the resampling unit 160 as a pager.

In this case, the pager calculation in the pager operator 170 uses a Discrete Fourier Transform (DFT) algorithm, and the calculated pager is time stamped using the GPS seconds.

As shown in FIG. 2, the time-synchronized phaser measuring apparatus 100 according to the present invention receives an analog signal of the PT voltage and the CT current measured in a system, and removes harmonics and noise of the analog signal, thereby removing the A / A. It may further include an analog filter 120 output to the D converter 140. In this case, the analog filter 120 is preferably used Butterworth analog filter (Butterworth Filter).

In addition, the time-synchronized phaser measuring apparatus 100 may further include a frequency / voltage converter (f / V converter) 130 between the analog filter 120 and the A / D converter 140. In this case, the frequency / voltage converter (f / V converter) 130 receives the signal filtered by the analog filter 120 and converts the system frequency of the analog voltage into a voltage and outputs it to the A / D converter 140. It performs the function.

In addition, the time-synchronized phaser measuring apparatus 100 receives a signal sampled from the A / D converter 140 to remove noise to output a clean signal to the resampling unit 160 and to filter a system frequency. The frequency filter 150 may further include. In this case, the system frequency filtered by the system frequency filter 150 is used as the sampling frequency when down sampling, that is, resampling by the resampling unit 160.

3 is an exemplary diagram to which a resampling technique is applied in the resampling unit 160.

Hereinafter, the principle of resampling, that is, downsampling in the resampling unit 160 will be described in detail with reference to FIG. 3. Here, downsampling is performed using a second-order Lagrange 2 interpolation method.

The frequency sampled by the A / D converter 140 converts an analog signal into digital data at a high frequency of 6.0 kHz or more.

The data period 161 in FIG. 3 is a digital data period performed by the A / D converter 140 and acquired, and the down-sampled period 162 is equal to an inverse of 24 times the system frequency.

That is, the data 163-1 to 163-4 measured by the A / D converter 140 generates down-sampled data 164-1 to 164-4 using the second-order Lagrangian interpolation. .

라고 하고 찾고자 하는 데이터를 T(x,z) 라고 하면 계산식은 아래 수학식 1과 같다.The second-order Lagrangian interpolation used above uses three measured digital data.

Suppose that the data you want to find T (x, z) is as shown in Equation 1 below.

는 측정된 데이터, T(x,z)는 보간하고자 하는 점, x는 보간하고자 하는 시간, y는 보간하고자 하는 계통 전압 또는 전류 값(unknown)을 각각 의미한다.here,

Is the measured data, T (x, z) is the point to be interpolated, x is the time to be interpolated, and y is the grid voltage or current value (unknown) to be interpolated, respectively.

As described above, the signal down-sampled by the resampling unit 160 is calculated by being discarded by the pager calculator 170.

Next, the calculation principle of the pager operation unit 170 that performs pager calculation on the resampled signal using a Discrete Fourier Transform (DFT) algorithm will be described.

The DFT algorithm equation for pager calculation in the pager operator 170 is as shown in Equations 2 to 6 below.

Here, N is the resampled number, Xc is the real part pager value, and Xs is the imaginary part pager value.

In this case, it is assumed that Equation 2 is an analog signal to be measured, and a pager expression for this value is shown in Equation 3 above.

Equation 4 represents digitally sampled data.

The digital data may be applied as a DFT of Equation 5 and expressed as a real part and an imaginary part as a pager as shown in Equation 6 above.

In this case, the pager finally calculated by the pager calculator 170 is time stamped using the GPS seconds output from the synchronous clock generator 110 as described above.

In this case, the time-synchronized phaser measuring apparatus 100 according to the present invention may further include a network 180 for transmitting the pager calculated by the phaser calculator 170 to a higher monitoring system.

4 is an exemplary diagram of an overall system configuration in which the time synchronization and pager measurement device (PMU) 100 according to the present invention is installed.

In the entire system in which the phaser measuring device (PMU) 100 according to the present invention is installed, the phaser measuring device (PMU) 100 is installed at the front end of the generator 210, as shown in FIG. 220) and the PT voltage signal 230 were measured.

In addition, when transmitting the generator 210 output by the transmission line 240 suddenly opened the breaker 250 from the power system 260 to increase the frequency of the generator 210.

The system used was an NI-PXI system with a real-time controller, a sampling rate of 9 kHz, and an internal resampling rate of 24 (24 * fsys) times the system frequency.

The system frequency measurement was performed using the NI SCXI-1126 module to convert frequency to voltage. In this case, the analog filter 120 in FIG. 1 is a Butterworth filter.

5 is a measurement result when the breaker 250 is opened with an output of 170 MW at 800 MVA nuclear power generator by applying the time synchronized phaser measuring device (PMU) according to the present invention.

At this time, the measured frequency 310 rose to 61.1 Hz. It can be seen that the measured frequency 310 has risen higher than in FIG. 1, which shows an experimental example of a conventional pager measuring device (PMU).

However, it can be seen that the voltage vibration observed in FIG. 1, which is an experimental example of a conventional PMU, is not observed in the terminal voltage 320 of FIG. 5, and only other noises appear.

The noise of the terminal voltage in FIG. 5 is a case where an LC filter is used in the analog filter 20 shown in FIGS. 2 and 3 at an input terminal for measuring an analog signal.

In the case of using the time-synchronized phasor measurement device to which the resampling technique according to the present invention has the above-described configuration, the system frequency is removed from 60 Hz to 1 Hz by eliminating the vibration phenomenon generated by the existing algorithm when it greatly deviates from 60 Hz. Even in the case of a large fluctuation, it is possible to accurately calculate the phaser value of the voltage / current to be measured, thereby improving the reliability or stability of the system operation and the system control.

6 is a flowchart illustrating a method of measuring a time synchronization pager to which a resampling technique is applied according to an embodiment of the present invention.

In the following, the description of the parts of the time-synchronized phaser measuring apparatus of the present invention and the description overlapping will be omitted.

According to the present invention, the method for measuring time-synchronized phaser is a method for measuring a synchronized phaser for an analog signal of PT voltage and CT current measured in a system, as shown in FIG. 6, an analog signal filtering step S10, a sampling step S20, A down sampling step S30 and a pager calculation step S40 are included.

That is, the method for measuring time synchronization phaser according to the present invention is as follows.

First, harmonics and noise of the analog signal measured by the system are filtered (removed) (S10).

Next, the filtered signal is sampled by the time-synchronized sampling counter signal (S20).

Next, the sampled signal is resampled, that is, downsampled (S30).

Next, the down-sampled signal is calculated as a pager using a Discrete Fourier Transform (DFT) algorithm (S40). In this case, the phaser calculating step S40 may further include time stamping the calculated phaser by GPS seconds for the sampling counter signal.

FIG. 7 is a flowchart illustrating a method of measuring a time synchronization pager to which a resampling technique is applied according to another embodiment of the present invention.

As shown in FIG. 8, the time synchronization measurement method according to the present invention uses the system frequency of the analog voltage filtered in the analog filtering step S10 between the analog filtering step S10 and the sampling step S20 as a voltage. A frequency / voltage (f / V) converting step S15 is further included.

In addition, between the sampling step S20 and the down sampling step S30, a noise of a signal sampled in the sampling step S20 is removed and a system frequency used as a sampling frequency of down sampling in the down sampling step S30. The method may further include a noise / system frequency filtering step S25 for filtering.

In addition, the method may further include a step S50 of transmitting the pager calculated in the pager calculation step S40 to a higher monitoring system.

Preferred embodiments of the present invention described above are disclosed to solve the technical problem, and those skilled in the art to which the present invention pertains (ie, those skilled in the art) various modifications, changes, and additions within the spirit and scope of the present invention. It should be understood that such modifications and the like fall within the scope of the following claims.

1 is an exemplary view showing a measurement result by a phaser measuring device (PMU) according to the prior art when the frequency fluctuates

2 is a block diagram of an apparatus for measuring a time synchronization phaser according to an embodiment of the present invention.

3 is an example of downsampling by Lagrangian interpolation in a resampling unit

4 is a block diagram of an apparatus for measuring a time synchronization phaser according to another embodiment of the present invention.

5 is an exemplary diagram of an entire system provided with a time synchronization phaser measuring apparatus according to the present invention.

6 is an exemplary view showing a measurement result by the time-synchronized phaser measuring apparatus according to the present invention when the frequency is changed.

7 is a flowchart illustrating a method of measuring a time synchronization phaser according to an embodiment of the present invention.

8 is a flowchart illustrating a method of measuring a time synchronization phaser according to another embodiment of the present invention.

[Description of Code for Major Parts of Drawing]

100: PMU 110: synchronous clock generator

111: GPS Clock 112: Instrument Real Time Clock

113: GPS second sampling unit 120: analog filter

130: frequency / voltage (f / V) converter 140: A / D converter

150: system frequency filter 160: resampling unit

161 data cycle 162 down cycle

163-1 to 163-4: Data measured by A / D converter

164-1 to 164-4: down-sampled data

170: pager calculator 180: network

210: generator 220: CT current signal

230: PT voltage signal 240: transmission line

250: breaker 260: power system

310: measured frequency 320: terminal voltage wire

S10: analog signal filtering step S15: frequency / voltage conversion step

S20: Sampling Step

S25: Noise reduction and system frequency filtering

S30: Down Sampling Step S40: Phaser Calculation Step

S50: step of transmitting to the upper monitoring system

Claims (15)

In the synchronous phaser measuring device for the analog signal of PT voltage and CT current measured in the system, A synchronous clock generator for outputting a time-synchronized sampling counter signal and GPS seconds for the sampling counter signal; An A / D converter receiving the sampling counter signal and sampling the analog signal; A resampling unit for down sampling the signal sampled by the A / D converter; And A pager calculator configured to calculate a down sampled signal by the resampling unit as a pager; Apparatus for visually synchronized pager measurement, comprising a resampling technique comprising a. The method of claim 1, wherein the synchronous clock generator, A GPS clock time-synchronized with the 1PPS and IRIG-B signals received from the GPS; A local clock for generating the sampling counter signal and outputting the sampling counter signal to the A / D converter; And A GPS second sampling unit configured to receive a sampling signal from the measuring instrument real-time clock and output the GPS seconds to the pager calculator; Apparatus for visually synchronized pager measurement, comprising a resampling technique, characterized in that it comprises a. The method of claim 1, wherein the pager calculator, The down-sampled signal is calculated using a Discrete Fourier Transform (DFT) algorithm as a pager, and time stamped using the GPS seconds. Device. The apparatus of claim 1, wherein the time synchronization phaser measuring device comprises: A phaser measuring device to which the resampling technique is applied further comprises an analog filter for receiving the analog signals of the PT voltage and the CT current, filtering harmonics and noise, and outputting the filtered analog signal to the A / D converter. . The method of claim 4, wherein And the analog filter is a Butterworth filter. The apparatus of claim 4, wherein the time synchronization phaser measuring device comprises: Resampling technique is applied to the analog filter further comprises a frequency / voltage (f / V) converter for receiving the filtered signal from the analog filter to convert the system frequency of the analog voltage to the voltage and output to the A / D converter Time Synchronized Phaser Measurer. The apparatus of claim 6, wherein the time synchronization phaser measuring device comprises: The resampling technique may further include a system frequency filter which removes noise of a signal sampled by the A / D converter and filters a system frequency used as a sampling frequency of the down sampling to provide the resampling unit. Applied time-synchronized phaser measuring device. The method of claim 1, wherein the resampling unit, A time-synchronized phasor measurement device to which resampling is applied, characterized by downsampling by Lagrange interpolation. The method of claim 1, wherein the down sampling period is And a reciprocal of 24 times the system frequency sampled by the A / D converter. The method of claim 1, The time synchronization phaser measuring device, And a network for transmitting the pager calculated by the pager calculator to an upper monitoring system. In the synchronous phaser measurement method for the analog signal of the PT voltage and CT current measured in the system, (a) filtering harmonics and noise of the analog signal (S10); (b) sampling (S20) the signal filtered in the step (a) by a time-synchronized sampling counter signal; (c) down sampling the signal sampled in the step (b) (S30); And (d) calculating the down-sampled signal in step (c) into a pager by a Discrete Fourier Transform (DFT) algorithm (S40); Visual synchronization pager measurement method to which the resampling technique comprising a. The method of claim 11, wherein step (d) And time stamping the pager calculated in step (d) by GPS seconds for the sampling counter signal. The method of claim 11, wherein between (a) and (b), And (S50) converting the system frequency of the analog voltage filtered in step (a) into a voltage (S50). The method of claim 11, wherein between (b) and (c), The resampling technique may be further included by removing noise of the signal sampled in the step (b) and filtering the system frequency used as the sampling frequency of the down sampling in the step (c). How to measure the time synchronization phaser. The method of claim 11, The time synchronization pager measuring method, And transmitting (S70) the pager calculated in step (d) to a higher-level monitoring system.

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