JPH0621853A - Distribution line carrier reception method and its device - Google Patents

Abstract

PURPOSE:To provide the distribution line carrier reception method being able to detect stably a carrier without resetting of a threshold level against fluctuation of harmonic noise of a commercial frequency in a distribution system. CONSTITUTION:A 1st comparator circuit 11 compares the output of an integration circuit 4 with a 1st reference value to extract its minimum value and a 2nd reference value B2 is generated based on an output and a 2nd comparator circuit 6 compares the output of the integration circuit 4 with the 2nd reference value B2 to detect a carrier, then even when the harmonic level of a commercial frequency is fluctuated, the 2nd reference value B2 is automatically set again in following to the fluctuation, then mis-detection of the carrier is avoided and the carrier is stably detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distribution line carrier receiving method and apparatus used for communication between a master station of a substation and slave stations of various places in a distribution automation system.

[0002]

2. Description of the Related Art A high-speed and highly reliable distribution line carrier communication device is also required for distribution line carrier communication in a distribution automation system. A distribution line carrier receiving device based on the conventional method will be described below with reference to FIG.

In FIG. 4, a digitally modulated signal carried from a child station in each region to a parent station in a substation is a current transformer (hereinafter referred to as CT).
1), and the signal becomes only the signal wave component from which the harmonic component is removed by the bandpass filter (hereinafter referred to as BPF) 2. Next, the output of the BPF 2 is squared by the squaring circuit 3 and further integrated by the integration circuit 4 for a fixed time set by the timer 5 to obtain the sum of squares. Thereafter, the comparison circuit 6 compares the sum of squares with a preset threshold value, and detects the carrier when the sum of squares exceeds the threshold value.

[0004]

As described above, in the distribution line carrier receiving device based on the conventional method, the threshold value to be compared with the sum of squares of signals is fixed to the set value. In a distribution system, there are many fluctuations in noise such as harmonics of commercial frequency, so if the harmonics become larger than when the threshold is set, the harmonics of the commercial frequency will exceed the threshold and false detection of carriers will occur. There is a problem that occurs.

According to the present invention, there is no need to manually reset the threshold value for noise fluctuations such as harmonics of commercial frequency in the distribution system, and when the harmonics of commercial frequency are excessive as compared with the signal. In particular, it is an object of the present invention to provide a distribution line carrier receiving method and device capable of stable carrier detection.

[0006]

According to a first aspect of the present invention, there is provided a distribution line carrier receiving method for detecting a digital modulation signal injected into a distribution line by a current transformer and demodulating the digital modulation signal. A reference level signal is generated based on the minimum value of the integrated values of the signal detected by the current transformer, and then the reference level signal is compared with the integrated value of the time to perform carrier detection. And

A distribution line carrier receiving device according to claim 2 is
A digital modulation signal injected into a distribution line is detected by a current transformer, and in a distribution line carrier receiver that demodulates the digital modulation signal, a square circuit that squares the signal detected by the current transformer, and its output An integration circuit that repeatedly integrates over a specified time, a first comparison circuit that compares the output of the integration circuit with a first reference value to extract a minimum value, and an output that is updated by the output of the first comparison circuit. A memory that outputs a value as the first reference value, and a second comparison circuit that compares the output of the integration circuit and a second reference value based on the output of the memory at each of the specified times to extract a carrier. And is provided.

A distribution line carrier receiving device according to claim 3 is
In the distribution line carrier receiving device for detecting the digital modulation signal injected into the distribution line by the current transformer and demodulating the digital modulation signal, an absolute value circuit for outputting the absolute value of the signal detected by the current transformer, An integrating circuit for repeatedly integrating the output over a specified time, a first comparing circuit for comparing the output of the integrating circuit with a first reference value to extract a minimum value, and an output of the first comparing circuit A memory that is updated by the above and outputs the value as the first reference value, and a carrier is extracted by comparing the output of the integration circuit and a second reference value based on the output of the memory for each specified time. And 2 comparator circuits are provided.

[0009]

According to the structure of the first aspect, the reference level signal is generated based on the minimum value of the integrated values of the input signal from time to time. Therefore, even if the noise level such as a harmonic of the commercial frequency fluctuates, The reference level signal automatically changes according to the change.

According to the second aspect of the present invention, the output of the first comparing circuit and the first comparing circuit for comparing the output of the integrating circuit with the first reference value to extract the minimum value are updated and the value is updated. Since the memory for outputting the first reference value is provided,
The comparator circuit compares the output of the integrator circuit with the first reference value, extracts the minimum value, and generates the second reference value based on the output.

According to the third aspect of the invention, since the absolute value circuit is used instead of the square circuit of the second aspect, even if the harmonic of the commercial frequency is larger than the signal, the integrated value of the harmonic of the commercial frequency becomes The second reference value generated based on this does not exceed the integral value of the signal wave frequency.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The distribution line carrier receiving method of the present invention will be described below with reference to specific embodiments. In addition, FIG. 4 showing a conventional example
Those having the same operation as will be described with the same reference numerals.

FIG. 1 shows a distribution line carrying / receiving apparatus adopting the distribution line carrying / receiving method of the present invention. The digital modulation signal detected by CT1 is band-limited to the frequency of the signal wave component by BPF2, squared by square circuit 3, and integrated circuit 4
The integration is performed during the measurement time T of the timer 5, and the output of the integration circuit 4 is input to the changeover switch 7.

The counter 9 reset by the reset circuit 8 counts up the measurement time T of the timer 5, and the count value is an integer N set in the third comparison circuit 10, that is, the time "NT". Until the lapse of time, the changeover switch 7 is switched to the switch output E side, the output of the integrating circuit 4 is input to the first comparing circuit 11, and is compared with the output of the memory 12 whose initial value is set to the maximum positive value. The smaller value is updated in the memory 12. The contents of the memory 12 are multiplied by the contents of the updated memory 12 and a constant by the multiplication circuit 13 and input as the threshold value of the second comparison circuit 6.

Next, the third comparison circuit 10 switches the changeover switch 7 to the switch output F side after the count value of the counter 9 is N, that is, after the lapse of the time "NT", and the output of the integration circuit 4 is changed. Is input to the second comparison circuit 6,
For each time T measured by the timer 5, the threshold value generated by the multiplication circuit 13 is compared, and if the threshold value is exceeded, carrier detection is performed.

Hereinafter, an example of waveforms when each part operates will be described with reference to FIG. In FIG. 2, A shown in (a) is B
The output of PF2, the solid line B ₁ shown in (b) is the output of the memory 12, the broken line B ₂ is the output of the multiplication circuit 13, the C shown in (c) is the output of the integration circuit 4, and the D shown in (d) is This is the output of the second comparison circuit 6.

First, the switch output E is selected by the changeover switch 7 until the count value of the counter 9 is N, that is, before the time "NT" has elapsed, and the timer is stored in the memory 12 as shown by the waveform B _{1 in} (b). During the measurement time T of 5, the minimum value obtained as a result of integration by the integration circuit 4 is stored, and the content of the updated memory 12 is multiplied by the constant by the multiplication circuit 13, and the multiplication result is the second comparison circuit. 6 is input as the threshold value shown by the broken line B ₂ in (b).

Next, when the count value of the counter 9 is N, that is, after the lapse of time "NT", the switch output F is selected by the changeover switch 7, and the output of the integrating circuit 4 as shown by the waveform C in FIG. 2 is input to the comparison circuit 6 and the second comparison circuit 6 starts comparison with the threshold value shown by the broken line B ₂ in (b), and the output of the integration circuit 4 is output at point S shown in (c). The threshold value B ₂ is exceeded, and the carrier detection signal D is output from the second comparison circuit 6 as a waveform D shown in (d).

According to the above configuration, the counter 9 is reset by the reset circuit 8, and until the time NT elapses, a constant multiple of the minimum value of the sum of squares of signals in the section of the measurement time NT from the switch output E of the changeover switch 7. The value is input as the threshold value of the second comparison circuit 6, and after the lapse of time NT, the switch output F of the changeover switch 7 is selected,
Since the comparator circuit 6 compares the sum of squares of the signal at time T with the threshold value and outputs the carrier detection signal D, even if the harmonic of the commercial frequency in the distribution line becomes larger than that when the threshold value is set, the comparison circuit 6 periodically. If the reset circuit 8 is used to reset, the optimum threshold value can be automatically set each time.
The same effect can be obtained by configuring the above circuit using a microprocessor.

In the above embodiment, the signal was input to the integrating circuit 4 via the squaring circuit 3, but this outputs the absolute value of the signal detected by CT1 instead of the squaring circuit 3 as shown in FIG. By using the absolute value circuit 14, in addition to the effect of the above-described embodiment, the second value generated based on the integral value of the harmonic of the commercial frequency even when the harmonic of the commercial frequency becomes excessive compared to the signal. Since the threshold value as the reference value does not exceed the integral value of the signal frequency, the effective effect of stable carrier detection can be obtained.

[0021]

According to the distribution line carrier receiving method of the present invention, a reference level signal is generated on the basis of the minimum value of the integrated values of the input signal, and then the reference level signal and the sometimes integrated value are generated. Since carrier detection is performed by comparing with the integrated value of, the fluctuation of noise such as harmonics of the commercial frequency is large, and the harmonics of the commercial frequency on the distribution line are larger than when the reference level signal was set and exceeded the reference level signal. Even in such a case, the reference level signal is automatically reset to a high level by following the integrated value of the harmonic of the commercial frequency. Therefore, it is possible to eliminate the erroneous detection of carriers as in the conventional case, and as a result, it is possible to perform stable carrier detection.

According to the distribution line carrier receiving device of claim 2,
A first comparator circuit for comparing the output of the integrator circuit and the first reference value to extract the minimum value and a memory updated by the output of the first comparator circuit for outputting the value as the first reference value. The first comparator circuit is provided to compare the output of the integrator circuit with the first reference value to extract the minimum value, and the second value is output based on the output.
Since the reference value is generated, even if the harmonics of the commercial frequency in the distribution line become larger than when the second reference value is set, if the reset circuit is reset periodically, the optimum second reference value will be obtained each time. The automatic setting can be performed, false detection of carrier can be eliminated, and stable carrier detection can be performed as a result.

According to the third aspect of the present invention, since the absolute value circuit is used instead of the square circuit of the first aspect, even if the harmonic of the commercial frequency is larger than the signal, the integrated value of the harmonic of the commercial frequency is obtained. Since the second reference value generated based on does not exceed the integral value of the signal wave frequency, more stable carrier detection can be performed.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a distribution line carrying / receiving apparatus adopting a distribution line carrying / receiving method of the present invention.

FIG. 2 is a waveform diagram of a main part of FIG.

FIG. 3 is a configuration diagram of another embodiment.

FIG. 4 is a configuration diagram of a conventional distribution line carrier communication device.

[Explanation of symbols]

 1 Current Transformer (CT) 2 Band Pass Filter (BPF) 3 Square Circuit 4 Integration Circuit 5 Timer 6 Second Comparison Circuit 7 Changeover Switch 8 Reset Circuit 9 Counter 10 Third Comparison Circuit 11 First Comparison Circuit 12 Memory 13 Multiplier circuit

Claims (3)

[Claims] 1. A minimum value of the integrated values of the signal detected by the current transformer at the time of detecting the digital modulation signal injected into the distribution line by a current transformer and demodulating the digital modulation signal. A distribution line carrier receiving method in which a reference level signal is generated based on the above, and then the carrier is detected by comparing the reference level signal with the occasionally integrated value. 2. In a distribution line carrier receiver for detecting a digital modulation signal injected into a distribution line by a current transformer and demodulating the digital modulation signal, a squaring circuit for squaring the signal detected by the current transformer. An integrating circuit that repeatedly integrates the output over a specified time; a first comparing circuit that compares the output of the integrating circuit with a first reference value to extract a minimum value; and a first comparing circuit of the first comparing circuit. A carrier is extracted by comparing a memory that is updated with an output and outputs the value as the first reference value with a second reference value based on the output of the memory and the output of the integration circuit at each specified time. Second
The distribution line carrier receiving device provided with the comparison circuit of. 3. A distribution line carrier receiver for detecting a digital modulation signal injected into a distribution line by a current transformer and demodulating the digital modulation signal, and outputting the absolute value of the signal detected by the current transformer. An absolute value circuit, an integration circuit that repeatedly integrates its output over a specified time, a first comparison circuit that compares the output of the integration circuit with a first reference value and extracts a minimum value, and a first comparison circuit thereof. Comparing the output of the integrator circuit and the second reference value based on the output of the memory, which is updated by the output of the comparator circuit and outputs the value as the first reference value. A distribution line carrier receiving device provided with a second comparison circuit for extracting a carrier.