JPH0748683B2 - Power line carrier signal transmission device and signal demodulation circuit thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a power line carrier signal transmission apparatus and a signal demodulation circuit for transmitting transmission data composed of a serial signal by using a zero-phase circuit of a power line such as a distribution line. In particular, the present invention relates to a technique for demodulating transmission data without being disturbed by low-order and high-order frequencies included in a zero-phase voltage.

[Conventional technology]

The basic principle of signal transmission by power line carrier is described in the literature (Hitachi Review VoL.65, No.6 (1983-6) Miyahara / Ikeda et al. "Development of information transmission system using distribution line").

Further, Japanese Patent Laid-Open No. 58-51630 discloses a technique of demodulating without being affected by the residual zero phase voltage.

Further, Japanese Patent Application Laid-Open No. 59-62251 describes a technique for eliminating the influence of low-order frequency and residual zero-phase voltage by differentiating a signal.

[Problems to be Solved by the Invention]

According to the above-mentioned conventional technique, the influence of the residual zero-phase voltage and the low-order frequency can be eliminated, but the influence of the harmonic is not considered, and in the case where the zero-phase voltage or the like contains the harmonic, There is a problem that the reliability of signal transmission may decrease.

The following two points can be considered as factors of harmonics.

The method of changing the zero-phase voltage according to the transmission data is generally performed by synchronizing with the frequency of the reference phase of the power line and turning on / off the impedance of the ground circuit.
Harmonics are likely to occur at the moment of turning on and off.

In the demodulation circuit, generally, the reference phase voltage and the zero phase voltage are multiplied. This multiplication produces a double harmonic of the signal, but it is difficult to completely remove this double harmonic and realize a filter that allows only the fundamental wave of the signal to pass. Wave component remains.

However, if a harmonic component remains, there is a possibility that an erroneous determination will be made in the comparison judgment for detecting the signal component based on the level of the signal, and the reliability of signal transmission will decrease.

An object of the present invention is to provide a power line carrier signal demodulation circuit that demodulates a signal without being affected by harmonic components and improves reliability of data transmission.

Another object of the present invention is to provide a highly reliable power line carrier signal transmission device including such a signal demodulation circuit.

[Means for Solving the Problems]

In order to achieve the above object, the present invention synchronizes with a reference phase voltage set in a three-phase power line, and uses an integer n cycles of the reference phase frequency as 1-bit data, and transmits a zero-phase voltage of the power line as transmission data. And a multiplying circuit for obtaining a product of a reference phase voltage and a zero phase voltage detected from the power line, and a second harmonic generated at the time of multiplying the reference phase voltage and the zero phase voltage by using an output of the multiplication circuit as an input. A power line carrier signal transmission device comprising: a first filter that attenuates a wave; and a receiving unit that includes a waveform shaping circuit that demodulates the transmission data based on the output of the first filter. The receiving means is provided with a second filter of the band-pass type having a filter output of 1 as an input, a center frequency of 1 / 2n of the reference frequency and a frequency selectivity Q of about 0.5. [Operation] According to the above configuration, harmonics included in the output of the first filter, for example, those generated when the impedance of the zero-phase circuit is turned on and off according to the transmission data and included in the transmission data, multiplication of the signal demodulation circuit By removing the second harmonic generated by the circuit when the product of the reference phase voltage and the zero phase voltage is not removed by the first filter by the second filter, the cycle number n of 1-bit data The signal can be demodulated in response to the change without malfunction due to the harmonic component, and the reliability of data transmission can be improved.

〔Example〕

 Hereinafter, the present invention will be described based on examples.

FIG. 1 is a block configuration diagram of a receiving means of a power line carrier signal transmission device to which this embodiment is applied. High voltage distribution line 1
A high voltage coupler 2 for detecting a reference phase voltage and a zero phase voltage is connected to the. A high voltage coupler 2 outputs a reference phase partial voltage 4 and a zero phase partial voltage 5, which are input to a signal demodulation circuit 3. The isolation circuits 6 and 7 are inserted to insulate the demodulation circuit 3 from the ground potential, and when a plurality of demodulation circuits and a high-voltage coupler are arranged in parallel, they are grounded.
This is to prevent the wraparound operation via the circuit. The input filter circuit 8 is a circuit that adjusts the gain and phase shift of the reference phase voltage divider 4 and outputs the reference phase voltage signal 10. The input filter circuit 9 is a circuit that adjusts the gain and phase shift of the zero-phase voltage divider 5 and outputs a zero-phase voltage signal 11. Input filter circuit 8,9
Is multiplied by the multiplier 12, and the product output 13 is input to the first filter circuit 14. First filter circuit
14 is the second frequency that is twice the reference phase frequency (system frequency)
It has the characteristic of removing harmonics. The second filter circuit 16 that receives the output 15 of the first filter circuit 14 has a center frequency f ₀ of approximately 1 / 2n of the reference phase frequency and a frequency selectivity Q.
It is a band pass filter circuit of = 0.5. This second
The output 17 of the filter circuit 16 is input to the waveform shaping circuit 18, where it is shaped into reception data 19 having a waveform corresponding to the transmission data and output.

The detailed configuration of this embodiment will be described below together with the operation.

The reference phase voltage of the high-voltage distribution line 1 is level-exchanged in the high-voltage coupler 2, then passes through the input filter circuit 8, and is input to the multiplier 12 as the reference-phase voltage signal 10 having the waveform shown in FIG. .

On the other hand, although not shown, the transmission means sets the n-cycle length of the reference phase voltage (n is an integer multiple of the reference frequency forming 1-bit data) to 1-bit data, and sets the impedance of the zero-phase circuit according to the content of the transmission data. It is turned on and off as shown in FIG. Note that FIG. 2 shows an example in which n = 1. As a result, the waveform of the zero-phase voltage signal 11 detected through the high voltage coupler 2 and processed by the input filter circuit 9 is obtained as shown in FIG. 2 (c).

These two signals 10 and 11 are multiplied by the multiplier 12 to obtain the product output 13 shown in FIG. The product output 13 is input to the first filter circuit 14, where the second harmonic of the reference phase frequency is removed, and the DC component voltage signal 15 having the waveform shown in FIG. 2 (e) is obtained.

Here, a known circuit shown in FIGS. 3A to 3C can be applied to the first filter circuit 14 for removing the second harmonic. FIG. 1A shows a first-order low-pass filter composed of a resistor R ₁ and a capacitor C ₁ . The same figure (b) shows the resistance R ₁
And R ₂ , a capacitor C ₁ and C ₂ , and an operational amplifier OA. FIG. 3C is a second-order band pass filter including resistors R _{1 to} R ₄ , capacitors C _{1 to} C ₄ , and operational amplifier OA. With such a combination of filters,
It is possible to configure a filter circuit that attenuates the second harmonic and unnecessary harmonics.

DC component voltage signal output from the first filter circuit 14
As can be seen from the comparison of Fig. 2 (e) and (b), 15 is
It is obtained as a signal corresponding to the content of the transmission data. However, when the harmonics and the like accompanying the on / off of the impedance for the zero-phase signal described above are included, the DC component voltage signal 15 becomes that shown by the alternate long and short dash line in FIG. Therefore,
If an attempt is made to directly demodulate this signal with a comparator, a harmonic component may be caught at the threshold level SH, resulting in malfunction. Therefore, the DC component voltage signal 15 is further processed by the second filter circuit 16.

Here, the second filter circuit 16 will be described with reference to FIGS.

First, in order to detect the signal component from the waveform of the DC component voltage signal 15 described above, when the input voltage changes in the positive direction, a positive voltage of a magnitude proportional to the amount of change is output and the input voltage changes in the negative direction. Any circuit that has a characteristic of outputting a negative voltage having a magnitude proportional to the amount of change when it changes to. As such a circuit, a differentiation circuit using a capacitor C and a resistor R shown in FIG. 10 (a) or a resistor shown in FIG. 10 (b)
R ₁ to R _3, variation detecting circuit consisting of a capacitor C ₁ and the operational amplifier OA is known. However, these circuits cannot eliminate the effects of low-order frequencies and harmonics, as described in the problems of the prior art.

Therefore, in this embodiment, a bandpass filter circuit as shown in FIG. 4 is applied. There are a frequency selectivity Q and a center frequency f ₀ as elements expressing the characteristics of the band pass filter circuit. The difference between the input / output characteristics depending on the values of the frequency selectivity Q and the center frequency f ₀ will be described with reference to the waveform diagrams shown in FIGS. 5 and 6.

Figure 5 (a) is shows the input voltage, and the v ₁ becomes positive change and v negative changes made _1. The time T / 2 from each change point shows the time for half a cycle of f ₀ . Note that T = 1 / f ₀ . FIG. 5 (b) is an example in which Q is small, and it is possible to obtain a positive and negative output of v ₂ proportional to a change of v ₁ . However, it takes longer time than T / 2 until the output becomes 0 for one input change. FIG. 5 (c) is an example in which Q is about 0.5, and it is possible to obtain positive and negative outputs of v ₂ proportional to the change of v ₁ , and the time until the output becomes 0 for one input change is It is almost the same as T / 2. FIG. 5 (d) shows an example in which Q is high. For a change of v ₁ , a voltage v ₃ smaller than v ₂ is output, and then v ₃ , v ₄ , v ₅ are attenuated for one change. It becomes the output of vibration.

On the other hand, FIG. 6 (a) shows an example in which the input voltage v negative changes made ₁ to T / 2 hours after after positive changes v becomes _1. FIG. 6 (b) is an example in which Q is small as in FIG. 5 (b), and an output voltage of v ₂ can be obtained for the first change. Changes are entered, so v ₂
You can only get smaller output v ₃ .

FIG. 6 (c) is an example in which Q is about 0.5 as in FIG. 5 (c), and it is possible to obtain positive and negative outputs of v _{2 with} respect to changes of v ₁ .

FIG. 6 (d) is an example in which Q is high as in FIG. 5 (d),
The output of damping vibration is v ₄ , v ₅ , v ₆ , ... for two changes of v ₁ .

In FIG. 5 and FIG. 6, the difference in the case where f ₀ is constant and Q is changed is explained, but one output is obtained for one change, and the same output is obtained for the same change amount. Since it is necessary to obtain the data to reproduce the data, it can be seen that a bandpass filter having a Q of about 0.5 is desirable.

Next, the difference when Q is kept constant and f ₀ is changed will be described.

FIG. 7 (a) shows the input voltage, and
As in the figure, there are positive and negative changes of v ₁ .

FIG. 7 shows a case where the frequency is 1 / 2n times the reference phase frequency, that is, when the maximum frequency f of the signal component is f = 1 / T, and FIG. 7A shows the case where f> f ₀ . Indicates. According to this, it is possible to obtain a positive or negative output of v _{2 with} respect to a change of v ₁ . However, it takes longer time than T / 2 until the output becomes 0 for one input change. In contrast, FIG. 7 (c) is an example of f ≒ f _0, v ₁ become changed to v can be obtained an output of _positive and negative ₂ becomes, until the output for one input change becomes 0 The time is about the same as T / 2. On the other hand, view the. 7 (d) is an example of f <f _0, v ₁ become changed to v can be obtained an output of ₂ becomes negative, the time for the output to one input change becomes 0 Is less than T / 2.

FIG. 8 shows an example in which changes in the negative direction of v becomes ₁ to T / 2 hours after after positive changes similarly input voltage and the sixth figure v becomes _1.

FIG. 8 (b) is an example of f> f ₀ similar to FIG. 7 (b),
The output voltage of v ₂ is obtained for the first change, but it is smaller than v ₂ because the next change is input before the output becomes 0.
You can only get an output voltage of v ₃ . In contrast,
FIG. 8 (c) is an example of f≈f ₀ similar to FIG. 7 (c),
It is possible to obtain a positive or negative output voltage v _{2 for} a positive or negative change of v ₁ . On the other hand, FIG. 8 (d) is an example of f <f ₀ as in FIG. 7 (d), and a positive / negative output voltage v ₂ can be obtained with respect to a positive / negative change v ₁ .

As described above, according to FIGS. 7 and 8, if the band pass filter has the center frequency f ≦ f ₀ , the output according to the change amount of the input can be obtained. However, even when this circuit is applied, it is necessary to consider the response to harmonics, for example, when the zero-phase impedance is turned on, the positive input voltage shown in FIG. A harmonic voltage of v ₀ may be superimposed when the direction changes. FIG. 9 (b) shows the output voltage in the case of f≈f ₀ , which makes it possible to obtain a positive and negative output voltage v ₂ which is not affected by the higher harmonic wave v ₀ . FIG. 9 (c) shows the output voltage in the example of f <f ₀ , and the positive output voltage v ₃ and the negative output voltage v ₂ obtained by adding the harmonics v ₀ and the change v ₁ are added. can get. In this way, if different output voltages are output with respect to the amount of change of v _1, it becomes difficult to set the detection level in the waveform shaping circuit, leading to a decrease in transmission reliability.

From the above, a band pass filter circuit as shown in FIG. 4 is applied as a circuit for obtaining a positive / negative output proportional to the positive / negative change of the input voltage, and its frequency selectivity Q and center frequency f ₀ are applied. It can be seen that the appropriate value should be selected.
For example, for Q, at least the output should be non-oscillating.

Therefore, the second filter circuit 16 shown in FIG.
A bandpass filter with characteristics set to 0.5, f ₀ = 1 / 2n × (reference phase frequency) was applied. As a result, when the DC component voltage signal 15 shown in FIG. 2 (e) is input, the waveform variation output 17 shown in FIG. 2 (f) is obtained. This change output 17
Is guided to the waveform shaping circuit 18, where it is shaped into a signal having the contents matching the transmission data.

A detailed configuration of the waveform shaping circuit 18 is shown in FIG. The level setting circuit 20 detects the absolute value of the positive / negative peak value v ₂ of the variation output 17 and outputs the detection level 22 which is a voltage of 1/2 of this. The comparator 23 changes the positive voltage of the change output 17 and the detection level 22.
When the change output 17 exceeds the detection level 22, the set signal 25 shown in FIG. 2 (g) is output. Comparator 24
Compares the variation output 17 inverted by the inverter 21 with the detection level 22, and when the variation output 17 becomes smaller than the detection level 22 ', the reset signal 26 as shown in FIG. Is output. The flip-flop 27 is the set signal
When 25 is input, "1" is output, and when the reset signal 26 is input, "0" is output. Therefore, when the set signal 25 and the reset signal 26 are output as shown in FIGS. 2 (g) and 2 (h), the demodulated data 19 becomes as shown in FIG. 2 (i). As a result,
From FIGS. 2B and 2I, it can be seen that the demodulation circuit 3 correctly demodulates the transmission data.

As described above, according to the present embodiment, the second filter circuit 16 is constituted by the bandpass filter having the characteristics of Q = 0.5, f ₀ = 1 / 2n × (reference phase frequency). It has a great effect.

Since the DC component is removed, it is not affected by the DC offset due to the residual zero-phase voltage. This makes it possible to eliminate the subtraction circuit for offset removal.

Since low-order frequencies are also attenuated, demodulation can be performed without being affected by this.

Higher-order frequencies are also attenuated, so demodulation can be performed without being affected by this.

As a result, the signal can be demodulated without being affected by the harmonic components generated when the impedance of the zero-phase circuit is turned on and off according to the transmission data, and the high frequency components such as the thyristor load of the system. Is improved.

Moreover, since the second filter circuit is not affected by the offset of the first filter circuit, the offset adjustment is not necessary, and an inexpensive and stable demodulation circuit can be realized.

〔The invention's effect〕

According to the present invention, by providing the second filter which is a band-pass type whose center frequency connected to the output of the first filter is 1 / 2n of the reference frequency and whose frequency selectivity Q is approximately 0.5,
It is possible to obtain the effect of improving the reliability of data transmission by demodulating the signal without malfunction due to the harmonic component in response to the change in the cycle number n of the reference frequency that constitutes the transmitted 1-bit data.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a power line carrier signal transmission apparatus of an embodiment to which the present invention is applied, FIG. 2 is a waveform diagram of each part for explaining the operation of the embodiment of FIG. 1, and FIG. FIG. 1 is a diagram showing a specific example of the first filter circuit of the embodiment, FIG. 4 is a detailed configuration diagram of the second filter circuit of the embodiment of FIG. 1, and FIGS. 5 to 9 are second filter circuits. FIG. 10 is a waveform diagram for explaining the operating characteristics of FIG. 10, FIG. 10 is a diagram showing an example of a known differentiating circuit and a variation detecting circuit, and FIG. 11 is a detailed configuration diagram of the waveform shaping circuit of the embodiment of FIG. 3 ... Demodulation circuit, 12 ... Multiplier, 14 ... First filter circuit, 16 ... Second filter circuit, 18 ... Waveform shaping circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Nishijima 1-1-1 Kokubuncho, Hitachi City, Ibaraki Pref., Kokubun Plant, Hitachi, Ltd. (56) Reference JP-A-58-51630 (JP, A) Kai 50-99062 (JP, A)

Claims (2)

[Claims] 1. A transmission means for synchronizing a reference phase voltage set on a three-phase power line and changing the zero-phase voltage of the power line according to the transmission data, with integer n cycles of the reference phase frequency as 1-bit data. A multiplying circuit for obtaining a product of a reference phase voltage and a zero phase voltage detected from the power line; and a first harmonic which receives an output of the multiplying circuit and attenuates a second harmonic generated when the reference phase voltage and the zero phase voltage are multiplied And a receiving means having a waveform shaping circuit that demodulates the transmission data based on the output of the first filter. Power line carrier signal transmission, characterized in that the receiving means is provided with a bandpass type second filter having an input center frequency of 1 / 2n of the reference frequency and a frequency selectivity Q of about 0.5. apparatus. 2. The reference phase voltage detected from the three-phase power line and the reference phase voltage set in the three-phase power line are synchronized with the reference phase voltage, and the integer n cycles of the frequency of the reference phase voltage are transmitted as 1-bit data according to the transmission data. And a multiplication circuit for obtaining a product of zero-phase voltage detected from the preceding three-phase power line, and a first filter that receives the output of the multiplication circuit as an input and attenuates the second harmonic generated when the reference-phase voltage and the zero-phase voltage are multiplied And a waveform shaping circuit that demodulates the transmission data based on the output of the first filter, in a power line carrier signal demodulation circuit, wherein the first filter output is input and the center frequency is 1 of the reference frequency. A power line carrier signal demodulation circuit comprising a bandpass type second filter having a frequency selectivity Q of approximately 0.5 at / 2n.