JP4818188B2  Frequency change measuring device, frequency change rate measuring device, and power system control protection device  Google Patents
Frequency change measuring device, frequency change rate measuring device, and power system control protection device Download PDFInfo
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 JP4818188B2 JP4818188B2 JP2007109639A JP2007109639A JP4818188B2 JP 4818188 B2 JP4818188 B2 JP 4818188B2 JP 2007109639 A JP2007109639 A JP 2007109639A JP 2007109639 A JP2007109639 A JP 2007109639A JP 4818188 B2 JP4818188 B2 JP 4818188B2
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The present invention relates to a frequency change measuring device, a frequency change rate measuring device, and a power system control protection device used in a device that requires a change or rate of change in the frequency of the power system in the power system control protection device. .
The power system control and protection device is an important facility for stably operating a power system in which tidal currents change in a complex manner. is there. For example, in a DC control device, FACTS (Flexible AC Transmission System), PSS (Power System Stabilizer), etc., it is necessary to input the amount of frequency change. Further, in the system stabilization device (PSS), the central control device receives the frequency change rate of its own terminal from the load control terminal, and it exceeds a certain activation threshold (this is referred to as “95D”). As an FS (fail safe) condition, a 95D activation method for issuing a shutoff command to a load control terminal is widely adopted.
By the way, as a method of measuring the frequency of the power system, the conventionally used zero cross method detects the time width between two adjacent zero cross points that cross the zero level in the same direction as one period of the basic frequency. However, the zero cross method has a problem that it is easily influenced by harmonic components and noise components.
Therefore, when using the change or rate of change of the frequency of the power system measured by the zero cross method, the instantaneous value that causes 95D activation of the frequency change rate has a very large fluctuation due to the influence of voltage flicker. Startup may occur frequently and improvements are desired.
The present invention has been made in view of the above, and is capable of measuring a highly accurate and stable frequency change and change rate without being affected by a sudden phase change (voltage flicker) that appears in real time in the power system. And it aims at obtaining a change rate measuring device.
In order to achieve the abovedescribed object, the frequency change measuring apparatus according to the present invention is a sampling of instantaneous voltage values of a power system obtained at each sample timing obtained by equally dividing one period of a reference wave by 4N (N is a positive integer). Voltage amplitude calculating means for calculating an amplitude value of a voltage rotation vector represented on a complex plane using data by integration calculation using voltage instantaneous value sampling data in one cycle of the reference wave; and the voltage amplitude calculating means, A chord length which is an interval between the voltage amplitude average value calculation means for averaging the calculated voltage amplitude value by performing a moving average process over a period of one cycle or more of the reference wave, and two adjacent voltage rotation vectors. The chord length calculation means for calculating the chord length calculated by the chord length calculation means by using the integral calculation using the voltage instantaneous value sampling data in one cycle of the reference wave, and the chord length calculated by the chord length calculation means as 1 A chord length average value calculating means for averaging by performing a moving average process over a period of time, a voltage amplitude average value calculated by the voltage amplitude average value calculating means, and a chord length calculated by the chord length average value calculating means Rotation phase angle calculation means for calculating the rotation phase angle of the voltage rotation vector using the average value, and moving average processing over the period of one cycle or more of the reference wave using the rotation phase angle calculated by the rotation phase angle calculation means Rotating phase angle average value calculating means for performing averaging and calculating the static frequency of the power system using the frequency of the reference wave and the rotating phase angle average value calculated by the rotating phase angle average value calculating means A frequency calculating means for calculating a frequency change instantaneous value by obtaining a difference between the two static frequencies at each of two sample timings separated by a fixed period, and obtaining an instantaneous value of the frequency change; and the frequency change The frequency variation instantaneous value instantaneous value calculating means is calculated by performing a moving average process over a predetermined period; and a frequency variation average calculating means for averaging.
According to the present invention, the amplitude value of the voltage rotation vector is calculated by the integration method, and is averaged. In addition, the chord length between adjacent voltage rotation vector tips is calculated by an integration method and is averaged. Then, the rotational phase angle is obtained from the voltage amplitude average value and the chord length average value, and the moving phase is averaged, and the moving average of the rotational phase angle average value and the frequency of the reference wave are used for static Calculate the frequency. Using the static frequency that is not influenced by the sudden phase change thus obtained, the instantaneous value of the change between the frequencies separated by a certain period is moving averaged. As a result, there is an effect that a highly accurate and stable frequency change can be measured without being affected by a sudden phase change that appears in real time in the power system.
Exemplary embodiments of a frequency change and change rate measuring apparatus according to the present invention will be described below in detail with reference to the drawings.
Here, in order to facilitate understanding of the present invention, an outline of two frequency measurement methods (static frequency measurement method and dynamic frequency measurement method) already proposed by the present inventor will be described. Then, referring to FIG. 10, the frequency change and change are based on the measurement frequency according to the conventional “zero cross method” and the “static frequency measurement method” and “dynamic frequency measurement method” by the present inventor as the fundamental frequency. When the rate measurement device is configured, the rate of change detection performance in the four system phenomena is compared, and on the other hand, what is improved by the “method according to the present invention” configured as described above? explain.
The present inventor has used a technique for expressing an AC voltage as a voltage vector that rotates counterclockwise on a complex plane, and greatly eliminates the influence of system noise in a noisy power system, and system frequency is increased at high speed. A frequency measurement apparatus capable of measuring the above has been filed earlier (Patent Document 1).
An outline will be described. The voltage vector on the complex plane where the voltage value at the preceding measurement point of the two measurement points is the imaginary part of the complex coordinates and the voltage value at the subsequent measurement point is the real part of the complex coordinates is At the same time, it rotates counterclockwise on the complex plane. The chord length, which is the distance between the tips of two adjacent voltage rotation vectors, is calculated, and one period is added. Further, the effective voltage value is obtained from the measured voltage at each measurement point in one cycle. Then, the phase angle of the voltage vector is calculated from both voltage effective values at around one cycle at one measurement point and the added value of the chord length, and the frequency of the power system is obtained.
The abovedescribed measurement method proposed in Patent Document 1 is referred to as a static frequency measurement method. However, the present inventor subsequently uses the same static frequency measurement method to calculate the rotational voltage vector amplitude and chord length formula. A frequency measurement device that has been improved to improve measurement accuracy and expand the measurement frequency range has been filed earlier (Japanese Patent Application No. 2006153649). In addition, the inventor previously applied for a frequency measurement device using a dynamic frequency measurement method that measures the frequency change rate at each measurement point and measures the current dynamic frequency that is stable with high accuracy.
Next, in FIG. 10, as system phenomena, (1) no voltage flicker + no frequency change, (2) no voltage flicker + frequency change, (3) voltage flicker + no frequency change, (4) voltage flicker + Frequency changes are shown.
Here, “no voltage flicker” is a situation in which the voltage waveform has no sudden phase change and becomes a sine waveform. On the other hand, “with voltage flicker” is a situation in which there is a sudden phase change in the voltage waveform, which greatly affects the frequency measurement.
“No frequency change” is a situation in which the system frequency change rate fluctuates within the activation threshold and the frequency change and change rate measurement device should not start 95D. On the other hand, “with frequency change” is a situation in which the system frequency change rate fluctuates beyond the activation threshold, and the frequency change and change rate measurement device should start 95D at high speed.
The circles indicate that there is no problem with the measurement result of the frequency change rate. A cross indicates that there is a malfunction problem depending on the measurement result of the frequency change rate. The malfunction is to be activated due to the influence of voltage flicker despite no frequency change. Δ indicates that there is a possibility of malfunction or malfunction depending on the measurement result of the frequency change rate. Nonoperation means that there is a change in frequency and the activation is not performed or the activation is delayed.
In FIG. 10, when the “zero cross method” is adopted, the evaluation result in the situation of the system phenomenon (1), (2), and (4) is ○ mark, but the system phenomenon is in the situation of (3). The evaluation result of is a cross.
In other words, when the “zero cross method” is employed, a very large fluctuation occurs due to the influence of voltage flicker on the instantaneous value causing the 95D activation of the frequency change rate. This means that erroneous 95D activation occurs frequently. Although measures such as a significant increase in the number of verifications may be taken as a measure, in that case, the actual 95D activation may be delayed and cannot be implemented. For this reason, as described above, there is a frequent erroneous start of 95D at present when there is no appropriate countermeasure, and improvement is desired.
On the other hand, when the previously proposed “static frequency measurement method” is adopted, the evaluation result in the situation of the system phenomenon (1), (2), and (4) is ○ mark, but the system phenomenon is (3) The evaluation result in the situation of is △ mark. On the other hand, when the “dynamic frequency measurement method” is adopted, the evaluation result in the situation of the system phenomenon (1), (2), and (3) is ○ mark, but the system phenomenon is the situation of (4). The evaluation result at is a Δ mark.
That is, when the “dynamic frequency measurement method” is adopted, if there is a sudden phase change (voltage flicker), the detection of the tendency of frequency change becomes slow in principle, and there is a possibility that the 95D startup will be delayed. In this regard, when the “static frequency measurement method” is adopted, if the influence of the sudden phase change can be eliminated, a desired frequency change and change rate measuring apparatus capable of dealing with all the system phenomena (1) to (4) is configured. I understand what I can do. That is, the “method according to the present invention” can cope with any of the four system phenomena (1) to (4) by applying a measure that can eliminate the influence of the sudden phase change to the previously proposed “static frequency measurement method”. It is what I did. Hereinafter, the embodiment will be specifically described.
FIG. 1 is a block diagram showing the configuration of a frequency change and change rate measuring apparatus according to an embodiment of the present invention.
In FIG. 1, a frequency change and change rate measuring apparatus 1 according to this embodiment includes a voltage / current measuring means 2, an A / D conversion means 3, a voltage amplitude and moving average value calculating means 4, a chord length. And its moving average value calculating means 5, rotational phase angle and its moving average value calculating means 6, frequency calculating means 7, frequency change instantaneous value calculating means 8, frequency change average value calculating means 9, frequency A change rate average value calculation means 10, a frequency change and change rate control output means 11, a display means 12, and a storage means 13 are provided.
The voltage / current measuring means 2 measures a system voltage using a PT (instrument transformer) attached to the transmission line of the power system 14 or a CT (not shown) attached to the transmission line of the power system 14. System current is measured using a current transformer and converted to system voltage.
The A / D conversion means 3 samples the system voltage signal from the voltage / current measurement means 2 at each sample timing obtained by equally dividing one period of the reference wave by 4N (N is a positive integer), and timeseries digital data Convert to (Voltage instantaneous value data). Timeseries voltage instantaneous value data converted over a plurality of cycles of the reference wave is stored in the storage means 13.
The voltage amplitude and moving average value calculation means 4 first takes out voltage instantaneous value data for one cycle from the storage means 13, and uses the voltage instantaneous value data to obtain the amplitude value of the voltage rotation vector represented on the complex plane. Then, the integration calculation using the voltage instantaneous value data for one cycle is performed and stored in the storage means 13 one by one. Then, a voltage amplitude calculation result of one cycle or more is taken out from the storage means 13 and a moving average process is performed to average the voltage amplitude values, which are stored in the storage means 13 one by one.
The chord length and its moving average value calculation means 5 first integrates the chord length, which is the distance between the tips of two adjacent voltage rotation vectors, using the voltage instantaneous value data for one period taken out from the storage means 13. Calculations are made by calculation and stored in the storage means 13 one by one. Then, a chord length calculation result of one cycle or more is taken out from the storage means 13 and a moving average process is performed to average the chord lengths, which are stored in the storage means 13 one by one.
The rotation phase angle and moving average value calculation means 6 first takes out the averaged voltage amplitude value and chord length from the storage means 13 to calculate the rotation phase angle, and stores it in the storage means 13 one by one. Then, a rotational phase angle calculation result of one cycle or more is taken out from the storage means 13, a moving average process is performed, the rotational phase angles are averaged, and stored in the storage means 13 one by one.
The frequency calculation means 7 takes out the rotational phase angle average value from the storage means 13, calculates the frequency, and stores it in the storage means 13 one by one. Here, when there is an influence such as sudden phase change (voltage flicker), there is a certain error in the static frequency calculated using the rotational phase angle. Thus, the error is reduced by avoiding the influence of a sudden phase change (voltage flicker) or the like.
The frequency change instantaneous value calculation means 8 takes out the frequency at each measurement time from the storage means 13, calculates the difference between the frequency at a certain time and the frequency before a certain time, and calculates the difference between the frequency change at a certain time. The instantaneous value is stored in the storage means 13 one by one.
The frequency change average value calculation means 9 takes out an instantaneous value of frequency change within a predetermined time (mT: m is a specified integer, T is a sampling interval) from the storage means 13, and performs frequency averaging on the frequency change. The average value is stored in the storage means 13 one by one.
The frequency change rate average value calculating means 10 takes out the frequency change average value from the storage means 13 and divides it by a predetermined time nT (n is a specified integer) to calculate the average value of the frequency change rate. Store in the storage means 13 one by one.
When the device is a frequency change measuring device, the frequency change and change rate control output unit 11 uses the frequency change stored in the storage unit 13 as a control output as described above, and the device changes the frequency. If it is a rate measuring device, the frequency change rate stored in the storage means 13 as described above is used as a control output, and other devices such as a central control device are output, and they exceed a predetermined threshold value. When a command is received from another device such as a central control device, a cutoff command is issued to a CB (breaker) interposed in the power transmission line of the power system 14.
The display unit 12 displays the calculation result including the frequency change and the change rate stored in the storage unit 13 as described above on the display device.
The storage means 13 is realized by the CPU, and the voltage amplitude and moving average value calculating means 4, the chord length and moving average value calculating means 5, the rotation phase angle and moving average value calculating means 6 and the frequency calculating means 7 are realized. , A frequency change instantaneous value calculation means 8, a frequency change average value calculation means 9, a frequency change rate calculation means 10, a frequency change and change rate control output means 11, a ROM storing each program of the display means 12, a power It is composed of a RAM for storing the voltage instantaneous value timeseries digital data of the system and the calculation results of each means described above.
FIG. 1 shows a configuration in which the voltage instantaneous value timeseries digital data of the power system is acquired using the voltage / current measuring means 2 and the A / D conversion means 3 and stored in the storage means 13. When the value timeseries digital data can be obtained from another route and stored in the storage unit 13, the voltage / current measurement unit 2 and the A / D conversion unit 3 can be omitted.
Next, the operation of the frequency change and change rate measuring apparatus 1 configured as described above will be described with reference to FIGS. FIG. 2 is a flowchart for explaining the procedure for measuring the frequency change and the change rate. In FIG. 2, the step indicating the processing procedure is denoted as “ST”. FIG. 3 is a time chart illustrating processing operations from the frequency change instantaneous value calculation procedure (ST106) to the frequency change rate average value calculation procedure (ST108) shown in FIG.
In FIG. 2, in ST101, the voltage / current measurement means 2 and the A / D conversion means 3 acquire the voltage instantaneous value timeseries digital data of the power system. The input voltage for frequency measurement includes a phase voltage (A phase voltage, B phase voltage, or C phase voltage), or a line voltage (AB line voltage, BC line voltage, AC line) Any one of the line voltages) can be used. That is, the frequency measurement input voltage used here is a onephase voltage or a single line voltage. The instantaneous voltage v of the AC circuit can be expressed by the following equation (1) according to Fourier transform.
However, in Formula (1), V is fundamental wave voltage amplitude, ω is fundamental wave angular velocity, ψ is fundamental wave voltage initial phase, V _{k} is korder harmonic voltage amplitude, ω _{k} is korder harmonic voltage angular velocity, ψ _{k} is an initial phase of the kth harmonic voltage, and M is a positive integer having an arbitrary magnitude. That is, as shown in Expression (1), the voltage instantaneous value ν is composed of a voltage fundamental wave component and a plurality of voltage harmonic components. In the following formula expansion, voltage harmonic components are omitted for the sake of simplicity. This does not mean that the voltage harmonic component is ignored. In the present invention, the integral calculation method is used, so that the influence of the harmonic can be removed.
As described above, the voltage rotation vector has the preceding voltage instantaneous value as the imaginary part of the complex coordinate among the voltage instantaneous values obtained at the two adjacent sample points, and the subsequent voltage instantaneous value as the real part of the complex coordinate. Is a voltage vector on the complex plane expressed as, and rotates counterclockwise on the complex plane with the passage of time of the sample points. The real part vre and the imaginary part im of this voltage rotation vector can be expressed by the following equation (2). Note that the voltage instantaneous value v used in the following equations indicates the real part vre of this voltage rotation vector.
In ST102, the voltage amplitude and its moving average value calculation means 4 calculates the voltage amplitude value of the voltage rotation vector and its moving average value. First, the voltage amplitude value V (t) of the theoretical voltage rotation vector is obtained by dividing each period T0 of the reference wave into 4N (N is a positive integer) equal to the following equation (3) using an integration method. It can be obtained by applying each voltage instantaneous value v (t) measured at a point. Note that one cycle T0 is, for example, T0 = 1/60 = 0.0166667sec in a power system with a reference frequency of 60 Hz.
However, in this embodiment, in order to improve the calculation accuracy at the system frequency that may deviate from the reference frequency, the frequency fluctuation is affected by the following expression (4) using an integration method instead of the expression (3). The voltage amplitude value V (t) not to be calculated is calculated.
Next, the voltage amplitude value V (t) obtained by the equation (4) is averaged using the following equation (5) by the moving average method. Equation (5) represents a moving average of one cycle, but the fluctuation also decreases as the number of cycles for moving average increases.
In ST103, the chord length and its moving average value calculation means 5 calculates the chord length V2 (t) between adjacent voltage rotation vector tips and its moving average value V2ave. The chord length V2 (t) between adjacent voltage rotation vector tips is theoretically obtained by calculating the following equation (6) using an integration method.
However, in this embodiment, in order to improve the calculation accuracy at the system frequency that may deviate from the reference frequency, the frequency fluctuation is affected by the following equation (7) using an integration method instead of the equation (6). The chord length V2 (t) not calculated is calculated.
Next, the chord length V2 (t) obtained by the equation (7) is averaged using the following equation (8) by the moving average method. Equation (8) represents a moving average of one cycle, but as the number of cycles taking the moving average increases, the fluctuation also decreases.
In ST104, the rotational phase angle and its moving average value calculation means 6 calculate the rotational phase angle δ (t), which is an electrical angle at which the voltage rotation vector rotates in one cycle of the reference wave, and its moving average value δave (t). calculate. The rotational phase angle δ (t) is obtained by the following equation (9), and the moving average value δave (t) is obtained by the following equation (10). In addition, although Formula (10) shows the moving average of 1 period, a fluctuation  variation also becomes small as the number of periods which take a moving average increases.
In ST105, the frequency calculation means 7 calculates the system frequency f (t). The voltage rotation vector of the system rotates by a phase angle Ψ (t) == 4N × δ (t) in the counterclockwise direction on the complex plane during one period of the reference wave, that is, t = 0 to t = T0. . Therefore, the system frequency f (t) is expressed as f (t) = (Ψ (t) / 2π) × f0 = 4N × δ (t) from the proportional relationship between the phase angle Ψ (t) and the reference frequency f0. I can express. The frequency obtained in this way is the “static frequency” that the inventor says, but in this embodiment, in order to avoid the influence of a sudden phase change (voltage flicker) and the like and reduce the error, Instead of the phase angle δ (t) shown in (9), the frequency f (t) is obtained by the following equation (11) using the rotational phase angle average value δave (t) shown in the equation (10). Yes.
Next, referring to FIG. 3, processing operations from the frequency change instantaneous value calculation procedure (ST106) to the frequency change rate calculation procedure (ST108) will be described. In FIG. 3, T is one sampling interval. For example, in an electric power system with a reference frequency of 60 Hz, if an electrical angle of 30 degrees is defined as one sampling interval T, the one sampling interval T is T = 1/60/12 = 0.13838889 seconds. Each of n and m is a positive integer, and a section nT shown in FIG. 3 is a section for taking a time difference of the instantaneous frequency value calculation, for example, three periods of the reference wave. Also, the section mT shown in FIG. 3 is a time section for calculating the frequency variation average value, and is, for example, three periods of the reference wave.
In FIG. 3, the frequency f {t− (n + m) T} at the time point before n + m samples out of the system frequency f (t) at each sample time point calculated by the frequency calculating means 7 at ST105, and n + 1. A frequency f {t− (n + 1) T} at a time point before the sample, a frequency f {t−nT} at a time point n samples before, a frequency f {t−mT} at a time point m samples before, A frequency f {t−T} at a time point one sample before and a frequency f (t) at the present time are shown.
In FIG. 3, as the frequency change instantaneous value calculated by the frequency change instantaneous value calculating means 8 in ST106, the frequency change instantaneous value Δf (t) calculated at the present time and the frequency calculated at the time one sample before A change instantaneous value Δf (t−T) and a frequency change instantaneous value Δf (t−mT) calculated at a time point m samples before are shown.
Also, in FIG. 3, the frequency change average value Δfave (t) calculated at the present time is shown as the frequency change average value calculated by the frequency change average value calculating means 9 in ST107, and the frequency change rate average value in ST108. As the frequency change rate average value calculated by the calculation means 10, the frequency change rate average value f′ave (t) calculated at the present time is shown.
In ST106, the frequency change instantaneous value calculating means 8 calculates the frequency change instantaneous value Δf (t−mT) before m samples as the frequency f (t−mT) before m samples and the frequency f before n + m samples. The difference (Δf (t−mT) = f (t−mT) −f (t− (n + m) T) with respect to (t− (n + m)) is obtained as an instantaneous value Δf (t− T) is the difference (Δf (t−T) = f (t−T) −f () between the frequency f (t−T) before one sample and the frequency f (t− (n + 1) T) before n + 1 samples. t− (n + 1) T), and the instantaneous value Δf (t) of the current frequency change is obtained by calculating the difference (Δf (t)) between the current frequency f (t) and the frequency f (t−nT) n samples before. t) = f (t) −f (t−nT).
The frequency change rate instantaneous value f′in (t) is obtained by dividing the frequency change instantaneous value Δf (t) by the time interval nT. That is, it can be calculated by f′in (t) = Δf (t) / nT.
Further, in ST107, the frequency change average value calculating means 9 obtains the current frequency change average value Δfave (t) by calculating the following equation (12).
In ST108, the frequency change rate calculating means 10 calculates the average value f'ave (t) of the current frequency change rate by calculating the following equation (13).
Returning to FIG. 2, in ST109, it is determined whether or not to end the above processes from ST101 to ST108. Until it is determined to end (ST109: Yes) (ST109: No), the process returns to ST101. The processing from ST101 to ST108 is repeated. Note that the timing for ending the processes from ST101 to ST108 is appropriately determined in consideration of the time interval nT and the time interval mT shown in FIG.
Next, with respect to the “frequency”, “frequency change amount”, and “frequency change rate average value” calculated and measured as described above, the system phenomenon (3) “with sudden phase change (voltage flicker) + no frequency change” shown in FIG. As a result of the simulation of the system phenomenon (4) “with sudden phase change (voltage flicker) + with frequency change”, the results shown in FIGS. 4 to 9 were obtained. 4 to 6 show the case of the system phenomenon (3), and FIGS. 7 to 9 show the case of the system phenomenon (4).
System phenomenon (3) In the case of “with sudden phase change (voltage flicker) + no frequency change”, the theoretical value of the voltage waveform input frequency is 60 Hz, and 0.5 degrees (0.008726665 radians) at 0.16805566 seconds When the phase of the voltage waveform was suddenly changed, a large fluctuation occurred in the frequency measurement result as shown in FIG. The measurement result of the frequency change fluctuated as shown in FIG. 5 due to the influence of the sudden phase change of the voltage waveform, and the measurement result of the frequency change rate average value fluctuated as shown in FIG.
However, as shown in FIG. 5, the fluctuation range of the frequency change average value 20 is smaller than the fluctuation range of the frequency change instantaneous value 21. As shown in FIG. 6, when the positive frequency change rate activation threshold 22a is +0.5 Hz / s and the negative frequency change rate activation threshold 22b is −0.5 Hz / s, The fluctuation range of the frequency change rate average value 23 is small enough to be within the range of the frequency change rate starting threshold values 22a and 22b. This indicates that there is no erroneous start. The frequency change rate instantaneous value 24 shown in FIG. 6 is calculated for comparison, but fluctuates greatly exceeding the frequency change rate starting threshold values 22a and 22b. This indicates that there is a false start.
Next, in the case of system phenomenon (4) “with sudden phase change (voltage flicker) + with frequency change”, the theoretical value of the voltage waveform input frequency is 60 Hz, and the frequency is 1.5 Hz / s at 0.14027778 seconds. Further, when the phase of the voltage waveform of 0.5 degree (0.00872665 radians) is suddenly changed at the time of 0.168055556 seconds, as shown in FIG. Affected by flicker). Then, the measurement result of the frequency change fluctuated as shown in FIG. 8, and the measurement result of the frequency change rate average value fluctuated as shown in FIG.
However, as shown in FIG. 8, the fluctuation of the frequency change average value 26 is more relaxed than the fluctuation of the frequency change instantaneous value 27. Further, as shown in FIG. 9, when the frequency change rate activation threshold value 28 is set to +0.5 Hz / s, the frequency change rate average value 29 fluctuates when the frequency change rate activation threshold value 28 is exceeded, It does not become smaller than the frequency change rate activation threshold 28. This indicates that the data can be output at high speed + collation time (for example, 4 cycles).
The frequency change rate instantaneous value 30 shown in FIG. 9 is calculated for comparison. The frequency change rate instantaneous value 30 fluctuates far beyond the frequency change rate activation threshold 28, and from the frequency change rate activation threshold 28. Then, the frequency fluctuates again exceeding the frequency change rate activation threshold 28. This indicates that although it can be started at a high speed, since the dead zone (a period during which the frequency change rate activation threshold 28 is smaller) is entered during the verification time, the output time is delayed.
As described above, according to this embodiment, a highly accurate and stable frequency change and change rate can be measured without being affected by a sudden phase change (voltage flicker) that appears in real time in the power system. Therefore, if the power system control protection device is equipped with a device that requires a change in frequency and a change rate of the power system, the performance of the power system control protection device can be improved.
As described above, the frequency change measuring device according to the present invention is useful for measuring a highly accurate and stable frequency change without being affected by a sudden phase change (voltage flicker) appearing in real time in the power system. In particular, it is suitable for improving the performance of the power system control protection device by installing it in a device that requires a frequency change in the power system control protection device.
The change rate measuring apparatus according to the present invention is useful for measuring a highly accurate and stable frequency change rate without being affected by a sudden phase change (voltage flicker) appearing in real time in the power system. It is suitable for improving the performance of a power system control protection device by installing it in a device that requires a frequency change rate among the control protection devices.
DESCRIPTION OF SYMBOLS 1 Frequency change and change rate measuring device 2 Voltage / current measuring means 3 A / D conversion means 4 Voltage amplitude and moving average value calculating means 5 String length and moving average value calculating means 6 Rotating phase angle and moving average value thereof Calculation means 7 Frequency calculation means 8 Frequency change instantaneous value calculation means 9 Frequency change average value calculation means 10 Frequency change rate average value calculation means 11 Frequency change and change rate control output means 12 Display means 13 Storage means
Claims (3)
 The amplitude value of the voltage rotation vector expressed on the complex plane using the instantaneous voltage value sampling data of the power system obtained at each sample timing obtained by equally dividing one period of the reference wave by 4N (N is a positive integer) Voltage amplitude calculating means for calculating by integral calculation using voltage instantaneous value sampling data in one cycle of the wave;
Voltage amplitude average value calculating means for averaging the voltage amplitude value calculated by the voltage amplitude calculating means by performing a moving average process over a period of one cycle or more of the reference wave;
Chord length calculation means for calculating a chord length, which is an interval between the tips of two adjacent voltage rotation vectors, by an integration operation using voltage instantaneous value sampling data in one cycle of the reference wave;
A chord length average value calculating means for averaging the chord length calculated by the chord length calculating means by performing a moving average process over a period of one cycle or more of the reference wave;
A rotation phase angle calculation unit that calculates a rotation phase angle of a voltage rotation vector using the voltage amplitude average value calculated by the voltage amplitude average value calculation unit and the chord length average value calculated by the string length average value calculation unit;
A rotation phase angle average value calculation means for averaging the rotation phase angle calculated by the rotation phase angle calculation means by performing a moving average process over a period of one cycle or more of the reference wave;
Frequency calculation means for calculating a static frequency of the power system using the frequency of the reference wave and the rotation phase angle average value calculated by the rotation phase angle average value calculation means;
A frequency change instantaneous value calculating means for obtaining an instantaneous value of a frequency change by taking a difference between the two static frequencies at each of two sample timings separated by a fixed period;
A frequency change average value calculating means for averaging the frequency change instantaneous value calculated by the frequency change instantaneous value calculating means by performing a moving average process over a fixed period;
A frequency variation measuring device comprising:  The amplitude value of the voltage rotation vector expressed on the complex plane using the instantaneous voltage value sampling data of the power system obtained at each sample timing obtained by equally dividing one period of the reference wave by 4N (N is a positive integer) Voltage amplitude calculating means for calculating by integral calculation using voltage instantaneous value sampling data in one cycle of the wave;
Voltage amplitude average value calculating means for averaging the voltage amplitude value calculated by the voltage amplitude calculating means by performing a moving average process over a period of one cycle or more of the reference wave;
Chord length calculation means for calculating a chord length, which is an interval between the tips of two adjacent voltage rotation vectors, by an integration operation using voltage instantaneous value sampling data in one cycle of the reference wave;
A chord length average value calculating means for averaging the chord length calculated by the chord length calculating means by performing a moving average process over a period of one cycle or more of the reference wave;
A rotation phase angle calculation unit that calculates a rotation phase angle of a voltage rotation vector using the voltage amplitude average value calculated by the voltage amplitude average value calculation unit and the chord length average value calculated by the string length average value calculation unit;
A rotation phase angle average value calculation means for averaging the rotation phase angle calculated by the rotation phase angle calculation means by performing a moving average process over a period of one cycle or more of the reference wave;
Frequency calculating means for calculating a static frequency of the system using the frequency of the reference wave and the rotating phase angle average value calculated by the rotating phase angle average value calculating means;
A frequency change instantaneous value calculating means for obtaining an instantaneous value of a frequency change by taking a difference between the two static frequencies at each of two sample timings separated by a fixed period;
A frequency change average value calculating means for averaging the frequency change instantaneous value calculated by the frequency change instantaneous value calculating means by performing a moving average process over a fixed period;
Frequency change rate average value calculating means for dividing the frequency change average value calculated by the frequency change average value calculating means by a predetermined period to obtain a frequency change rate average value;
A frequency change rate measuring apparatus comprising:  A power system control protection device comprising either the frequency change measurement device according to claim 1 or the frequency change rate measurement device according to claim 2.
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CN102033161B (en) *  20101217  20130410  南京邮电大学  Frequency measuring method of alternating current signal 
CN106802367B (en) *  20170117  20190924  基康仪器股份有限公司  Vibrating string type sensor signal period measurement method and device based on overlapping grouping 
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CN103809020B (en) *  20140117  20160427  浙江大学  The defining method of interconnected network lowfrequency oscillation frequency and damping estimated value simultaneous confidence intervals 
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