JPH06284584A - Automatic synchronous apparatus - Google Patents

Abstract

PURPOSE:To indicate synchronization accurately without introduction of a large scale and expensive arithmetic apparatus. CONSTITUTION:The synchronization of a point with a a reference phase is indicated by detecting the amplitude of AC voltage, the phase difference and frequency. An effective value vector is determined using a high speed Fourier's transformer (FFT) 1, and high precision synchronous inspection can be realized by obtaining a phase difference between the reference phase and the point with a phase difference arithmetic unit 3 and obtaining each frequency with an adder 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for automatically performing synchronous input between two points in a three-phase power system such as a power plant and a substation.

[0002]

2. Description of the Related Art Generally, the difference voltage between two AC instantaneous value waveforms (sin ω1t, sin ω2t) as shown in FIG.
As shown in the following expression (1), the beat waveform includes two types of frequency components and is as shown in FIG. If this is shown using a mathematical expression, the following expression (1) is obtained. sin ω1t−sin ω2t = 2sin {(ω1−ω2) t / 2} · cos {(ω1 + ω2) t / 2} (1)

Therefore, in the conventional analog automatic synchronizer, a point satisfying the phase coincidence point shown in FIG. 4 is detected to establish synchronization. Further, in performing the synchronization test, it is necessary to measure and adjust the frequencies of the AC waveforms at two points, and the frequency-voltage (F
/ V) A plurality of converters are used.

[0004]

By the way, when the synchronization detection or the verification is performed by a discrete amount of digital operation, the accuracy of the beat waveform largely depends on the discrete time. FIG. 5 shows the same beat waveform as in FIG. 4 in discrete amounts, but if this discrete amount is further increased, the waveform as in FIG. 6 is obtained. As described above, in order to perform the synchronization test by the digital operation using the discrete quantity, the step size of the discrete time is made small to ensure the accuracy of the beat waveform.

However, in this case, there is a problem that the number of calculations is increased and a load is placed on the digital calculation device, which makes it difficult to achieve multi-functionality. In addition, there is a problem in that the entire apparatus becomes large in size because a plurality of F / V converters are required for frequency detection. Therefore, it is an object of the present invention to reduce the load on the digital arithmetic unit to achieve multi-functionality and high accuracy.

[0006]

In order to solve such a problem, according to the first aspect of the invention, the magnitude, phase difference and frequency of a multi-system AC voltage including a reference phase are detected, and another point with respect to the reference phase is detected. In the automatic synchronizer that performs the synchronization input by the synchronization test of, the fast Fourier transform is performed for the magnitude of the AC voltage of the two systems consisting of the reference phase and the comparison target, and the effective value is obtained, and the zero crossing point of the reference phase is determined. It is characterized in that only the fundamental wave is detected by performing a vector operation with the phase reference. In the first aspect of the invention, instead of using the zero cross point of the reference phase as a phase reference, the AC voltage instantaneous value of the reference phase is pulsed, the pulsed signal is used as an external synchronization signal, and its rising edge is used as a phase reference. Can be used as (second invention).

According to a third aspect of the present invention, in an automatic synchronizer for detecting the magnitude, phase difference and frequency of a multi-system AC voltage including a reference phase, and performing synchronization by a synchronization test of another point with respect to the reference phase, For the two systems of AC voltage consisting of and the comparison target, the fast Fourier transform is performed to obtain the effective value, and the vector operation with the zero cross point of the reference phase as the phase reference is performed to detect only the fundamental wave. Is compared to obtain the phase difference between the AC voltages of the two systems. Also in this third invention, instead of using the zero crossing point of the reference phase as the phase reference, the AC voltage instantaneous value of the reference phase is pulsed, and this pulsed signal is used as the external synchronization signal, and its rising edge is the phase reference. Can be used as (4th invention).

According to a fifth aspect of the present invention, in the automatic synchronizer for detecting the magnitude, phase difference, and frequency of the multi-system AC voltage including the reference phase, and performing the synchronization input by the synchronization verification of the other point with respect to the reference phase, the reference is provided. It is characterized in that the frequency of the AC voltage to be compared is obtained from the frequency calculation result of the phase and the changing direction and the changing amount of the absolute value of the phase with respect to the reference phase.

[0009]

By calculating the effective value vector of a plurality of AC instantaneous value waveforms having different frequencies and obtaining the phase difference between them, it is possible to carry out a synchronization test of a plurality of AC waveforms. That is, if a plurality of AC instantaneous value waveforms are subjected to effective value vector calculation with the phase of the reference AC waveform as a reference and the phase difference between the two is measured, a long cycle (compared with the reference waveform as shown in FIG. Since a trend due to the phase difference of (the period that depends on the frequency deviation of the target waveform) can be obtained, even when detecting the phase coincidence point, it is not detected with a continuous amount as in the past, but with a discrete amount with a long sampling period. It becomes possible to secure sufficient accuracy. In addition, the frequency of the reference AC waveform is measured in the process of calculating the effective value vector, and the slope of the phase difference (frequency deviation) between the reference waveform and the comparison target waveform, the direction of rotation of the vector (the frequency of the comparison target waveform with respect to the reference waveform) (Upper and lower sides of), an accurate frequency deviation and both frequencies can be obtained.

[0010]

1 is a block diagram showing an embodiment of the present invention. In FIG. 1, 1 is a fast Fourier transform device (FFT), 2 is a frequency calculator, 3 is a phase difference calculator, 4
Is a frequency deviation calculator, 5 is an adder, and 6 is a phase coincidence point detector. That is, the reference instantaneous value waveform vs and the comparison target instantaneous value waveform vc are input to the FFT 1 where they are converted into effective value vector amounts. Since this effective value vector amount is sampled following the frequency of the reference waveform (with reference to the zero cross point of the reference waveform), the phase position is not synchronized and the vector direction is arbitrary, but the reference waveform vs The phase difference from the comparison target waveform vc can be accurately calculated by the phase difference calculator 3.

The frequency calculator 2 calculates the frequency of the reference waveform, and the frequency deviation calculator 4 uses the frequency of the reference waveform, the absolute value of the phase difference given from the phase difference calculator 3 and its change rate (slope). The frequency deviation of the comparison target waveform with respect to the reference waveform is calculated, and the adder 5 adds the frequency of the reference waveform to this frequency deviation to obtain the frequency of the comparison target waveform. The phase coincidence point detector 6 detects whether or not the frequency deviation and the phase difference between the reference waveform and the comparison target waveform are within a certain range, and if they are within a certain range, performs a synchronization test and outputs a synchronization command.

FIG. 2 is a block diagram showing another embodiment of the present invention. As is apparent from the figure, this embodiment is constructed by adding a pulse forming circuit 7 to the one shown in FIG. That is, in FIG. 1, sampling is performed with reference to the zero-cross point of the reference waveform, whereas here, the pulsed circuit 7 pulses the AC instantaneous value waveform vs of the reference phase, and the pulsed signal is used as the reference. The sampling is performed as. As a result, the phase position is always synchronized with the reference waveform, and the vector amount of the effective value is also synchronized with the reference waveform. Since the other points are the same as those in FIG. 1, description thereof will be omitted.

[0013]

According to the present invention, since the effective value is obtained by using the fast Fourier transform, it is possible to detect only the AC fundamental wave component, and to perform a highly accurate operation without harmonic components. Can be obtained. In addition, by measuring the frequency of the reference AC waveform and detecting the slope of the phase difference (frequency deviation) between the reference waveform and the comparison target waveform, and the vector rotation direction (up and down the frequency of the comparison target waveform with respect to the reference waveform). It is possible to obtain an accurate frequency deviation,
It is possible to obtain the frequencies of both.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram showing another embodiment of the present invention.

FIG. 3 is a waveform diagram showing two AC instantaneous value waveform examples.

FIG. 4 is a waveform diagram showing the beat waveform example of FIG. 3 in an analog amount.

FIG. 5 is a waveform diagram showing the beat waveform example of FIG. 3 using discrete amounts.

6 is a waveform diagram showing an example in which the discrete amount in FIG. 5 is increased.

FIG. 7 is an explanatory diagram of an example of AC phase difference calculation by effective value vector calculation.

[Explanation of symbols]

1 ... Fast Fourier Transform (FFT), 2 ... Frequency calculator, 3 ... Phase difference calculator, 4 ... Frequency deviation calculator, 5 ... Adder, 6 ... Phase matching point detector, 7 ... Pulsing circuit.

Claims (5)

[Claims] 1. An automatic synchronizer that detects the magnitudes, phase differences, and frequencies of alternating-current voltages of multiple systems including a reference phase, and performs synchronization input by performing a synchronization test at another point with respect to the reference phase, comparing the reference phase with a comparison target. Comparing the magnitude of the AC voltage of the two systems consisting of, the fast Fourier transform is performed to obtain the effective value, and the vector operation with the zero cross point of the reference phase as the phase reference is performed to detect only the fundamental wave. And an automatic synchronization device. 2. Instead of using the zero-cross point of the reference phase as a phase reference, the instantaneous AC voltage value of the reference phase is pulsed, the pulsed signal is used as an external synchronizing signal, and its rising edge is used as a phase reference. Claim 1 characterized by the above-mentioned.
The automatic synchronization device described in. 3. An automatic synchronizer that detects the magnitude, phase difference, and frequency of a multi-system AC voltage including a reference phase, and performs a synchronization input by a synchronization test at another point with respect to the reference phase, comparing the reference phase with a comparison target. For the two systems of AC voltage, the fast Fourier transform is performed to find the effective value, and the vector operation with the zero cross point of the reference phase as the phase reference is performed to detect only the fundamental wave and the two are compared. An automatic synchronizer characterized by obtaining a phase difference between two systems of AC voltage. 4. Instead of using the zero cross point of the reference phase as a phase reference, the AC voltage instantaneous value of the reference phase is pulsed, the pulsed signal is used as an external synchronizing signal, and its rising edge is used as a phase reference. 4. The method according to claim 3,
The automatic synchronization device described in. 5. An automatic synchronizer for detecting the magnitude, phase difference, and frequency of a multi-system AC voltage including a reference phase and performing synchronization by performing a synchronization test at another point with respect to the reference phase, wherein the frequency of the reference phase is calculated. An automatic synchronizer characterized in that a frequency of an alternating voltage to be compared is obtained from a result, a changing direction and a changing amount of an absolute value of a phase with respect to a reference phase.