JP2000252887A - Broadband harmonic eliminating filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broadband harmonic eliminating filter, that can enhance both the eliminating characteristic of harmonics of a power wave required for a power line carrier system and a broadband signal transmission characteristic for high transmission rate data transmission. SOLUTION: This broadband harmonic elimination filter eliminates the harmonics of a power wave when receiving a carrier signal superimposed on the power wave of a power line, in which a differential filter processing means 2 that subtracts a received signal f one preceding period with respect to a power frequency from a received signal at a present time in synchronism with the frequency of the power wave and an integration means 3, that outputs an output of the differential filter processing means 2 as is without integration, when a carrier arrival discrimination circuit 4 detects arrival of no carrier signal and outputs the output of the circuit 2 with integration from one preceding period with respect to the power frequency, when detecting the arrival of the carrier signal are connected in cascade.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a power line such as a high-voltage / low-voltage distribution line for supplying commercial power as a transmission line of a data signal, and superimposes a modulated carrier signal on a power wave to perform various types of monitoring. The present invention relates to an improvement of a broadband harmonic elimination filter suitable for a power line carrier signal receiving device in a power line carrier method for transmitting control / measurement data.

[0002]

2. Description of the Related Art In a power line carrier system, generally, harmonics caused by distortion of a commercial frequency exist in a distribution line, so that harmonics existing in the distribution line are removed and a wide band transmission for high-speed data transmission is performed. Compatibility of characteristics is important.

[0003] Conventionally, as a known method for removing a harmonic of a commercial frequency, which is a noise from a data signal, a differential filter for subtracting a carrier signal one cycle before the commercial frequency from a carrier signal in synchronization with the commercial frequency is known. Is used.

[0004]

With the recent remarkable progress of automatic control of the power distribution system, the amount of data signals to be transmitted has been increasing dramatically, and a demand for further increasing the data transmission speed has been increasing. ing. Here, when harmonics are removed using a differential filter, since there is a zero point of the gain for each harmonic order of the commercial frequency in the transmission band, a modulation / demodulation method based on the existence of this zero point must be used. In other words, it is necessary to limit the transmission band to be used to a narrow band between each harmonic of the commercial frequency so that the zero point of the differential filter is not included in the signal transmission band, and the modulation speed is about 25 to 30 baud. Limited to low speeds.

[0005] In addition, a modulation scheme in which a modulation section synchronized with the commercial frequency is arranged and modulation is performed using information encoded based on information one cycle before the commercial frequency is also conceivable. Since information using one cycle before the commercial frequency is used,
As a result of the influence from the noise being twice at the current time and one cycle before, the influence from the noise is large. (Object of the Invention) The object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a broadband harmonic elimination filter which can achieve both the elimination of harmonics of a power wave required for a power line carrier system and the wideband signal transmission characteristic for high-speed data transmission.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a broadband filter for removing a harmonic of a power wave in a wide band when receiving a carrier signal superimposed on the power wave of the power line. A difference filter processing means for subtracting a received signal one cycle before the power wave frequency from a received signal at the present time in synchronization with a frequency of the power wave; and an output of the difference filter processing means. Is output without integration when the arrival of the carrier signal is not detected,
When detecting the arrival of the carrier signal, there is provided an integrating means for integrating and outputting from one cycle before the power wave frequency.

[0007]

FIG. 1 is a block diagram of a broadband harmonic elimination filter for receiving a power line carrier signal according to an embodiment of the present invention.

The broadband harmonic elimination filter 1 subtracts the received signal one cycle (one cycle) before the commercial frequency from the received signal (carrier signal + harmonic noise) in synchronization with the frequency of the power wave, for example, the commercial frequency. Filter 2 having delay element D and inverting element (inverter) I
And an integrator 3 having the same delay element D and switch SW as the differential filter 2 are connected in cascade, and a carrier arrival decision circuit 4 is connected to an output point of the differential filter 2. Carrier arrival judgment circuit 4
The switch SW of the integrator 3 is turned on by the ON output of
The operation of the forced return timed circuit 5 is started, and after a fixed time period, the switch SW of the integrator 3 is turned off by the forced return timed circuit 5 and at the same time, the carrier arrival determination circuit 4 is activated.
It is configured to stop the ON output of. By detecting the disappearance of the carrier signal at the output side of the integrator 3,
The switch SW of the integrator 3 may be turned off, and the on-output of the carrier arrival determination circuit 4 may be stopped.

In the broadband harmonic elimination filter 1 in which the difference filter 2 and the integrator 3 are connected in cascade, the difference filter 2 constituting the preceding stage has a gain zero point for each harmonic. Therefore, it has a characteristic of completely removing stationary harmonics, that is, harmonics whose level and phase do not change. However, the actual harmonic component changes momentarily due to opening and closing of various loads connected to the power system. Such an unsteady harmonic passes through the differential filter 2 at the preceding stage and passes through the differential filter 2 at the subsequent stage. Since the signal is accumulated in the integrator 3, the signal becomes continuous noise, which greatly affects the reliability of the power line carrier system.

Therefore, as a measure against this problem,
The switch SW provided in the integrator 3 at the subsequent stage is always turned off, the arrival of the carrier is determined at the output point of the differential filter 2 at the preceding stage, and control is performed so that the integrator 3 performs the integration operation only during the arrival of the carrier. Therefore, in a normal state before the arrival of the carrier, even if there is a change in the harmonic, the change does not pass through the integrator 3 as it is and is not accumulated.

In order to use a system in which the differential filter 2 and the integrator 3 are connected in cascade, the arrival of a carrier wave is determined based on the output of the differential filter 2. A non-modulated carrier having a frequency between them and a certain length or more is added to the head of the modulated carrier signal. After the detection of the arrival of the carrier, the integrator 3 performs the integration operation.
Since a flat transfer characteristic is always obtained, there is no particular restriction on the modulation method of the carrier signal.

FIG. 2 is a diagram for explaining the operation of the broadband harmonic elimination filter 1 of FIG. As shown in FIG. 2A, in order to operate the broadband harmonic elimination filter 1, the frequency f _A between the gain zero point of the difference filter 2 and the frequency f _A at the head of the data signal modulated on the transmission side is fixed. A non-modulated preceding carrier A having a length or more is added. Therefore, FIG.
As shown in (b), the received signal arriving on the distribution line is an unmodulated preceding carrier A and a subsequent data signal S
, And a harmonic H of the commercial frequency is added.

The differential filter 2 based on such a received signal
2C is as shown in FIG. 2C in the case of stationary harmonics whose level and phase do not change. Therefore, the output of the carrier arrival determination circuit 4 connected to the output point of the differential filter 2 is constant. By detecting the unmodulated preceding carrier A having a length greater than or equal to the length, the arrival of the carrier is determined, and an on output is sent from the carrier arrival determining circuit 4 to the switch SW of the integrator 3 to turn on the switch SW of the integrator 3. For example, since the integrator 3 starts the integration operation, the output of the integrator 3 is as shown in FIG.
As shown in (d), the gain changes from 2 to 1, and the characteristic becomes a flat characteristic. The output of the carrier arrival determination circuit 4 is as shown in FIG.

FIG. 3 is a diagram showing the configuration and transfer characteristics of the differential filter 2, FIG. 3 (a) is a block diagram showing the configuration of the differential filter, and FIG. 3 (b) is a diagram showing the same frequency-gain characteristics. It is. Here, the characteristics of the difference filter 2 will be described using a z-transform useful for describing the characteristics of the signal conversion system.

In FIG. 3A, the input signal is X
(Z), the output signal is Y (z), the delay element of k unit time is z- ^k , and the inversion element is -1. Y (z) = X (z) -z- ^k X (z) (k : Integer), the transfer characteristic H _C (z) of X (z) → Y (z)
_{Is, H C (z) = Y} (z) / X (z) = 1-z -k next, z = exp (j2πf / F ): a (F sampling frequency) by substituting H _C (z) Frequency-gain characteristics | H _C
(F) | is calculated as: | H _C (f) | = 2 | sin ｛(2πf / F) · (k /
2)｝ |, and | H _C (f) | is f as shown in FIG.
= F / k and a characteristic having a zero point at a frequency that is an integral multiple thereof. In the case of the differential filter 2 used in the power line carrier system, F / k = ω ₀ / 2π (ω ₀ : commercial angular velocity), and the zero point of the gain is ω ₀ and its integral multiple.

FIG. 4 is a diagram showing a configuration and a transfer characteristic of the integrator. FIG. 4A is a block diagram showing a configuration of an integrator having no switch SW, and FIG. It is a figure showing a characteristic. Similar to the case of the difference filter 2, the characteristics of the integrator will be described using the z-transform.

In FIG. 4A, the input signal is X (z) and the output signal is Y
(Z), ^assuming that a delay element of k unit time is z ^−k , Y (z) = X (z) + z ^−k Y (z) (k: integer), so that X (z) → Y (z ) Transfer characteristic H _I (z)
The frequency of the _{H I (z) = Y (} z) / X (z) = 1 / (1-z -k) next, z = exp similarly by substituting _{(j2πf / F) H I (} z) - gain characteristic | H _I (f) | If _{seek, | H I (f) |} = 1/2 | sin {(2πf / F) ·
(K / 2)｝ |, and as shown in FIG. 4B, | H _I (f) | has a characteristic of diverging to infinity at a frequency of f = F / k and an integral multiple thereof, that is, , And has the inverse characteristic of the difference filter 2.

As shown in FIG. 4C, in the case of the integrator 3 in which the switch SW is added to the circuit including the delay element D, when the switch SW is off, Y (z)
= X (z), and the transfer characteristic H _I (z) of the integrator 3 is always 1.

When a transmission system in which the above-described differential filter 2 and integrator 3 are connected in cascade is constructed, the differential filter 2 and the integrator 3 having the same delay element D have mutually opposite transfer characteristics. The transfer characteristic when these are connected in cascade is H _CI (z) = (1−z− ^k ) / (1−z− ^k ) = 1, and the difference filter 2 and the integrator 3 are connected. By connecting in cascade, a flat transmission characteristic can always be realized in a wide band.

Therefore, the output of the integrator 3 shown in FIG. 2D depends on the transfer characteristic of the differential filter 2 since the integrator 3 does not perform the integration operation before the detection of the arrival of the unmodulated preceding carrier A. Although an output with a gain of 2 has been obtained,
The carrier arrival determination circuit 4 determines the arrival of the carrier by detecting the unmodulated preceding carrier A having a certain length or more, and sends an ON output from the carrier arrival determination circuit 4 to the switch SW of the integrator 3 so that the integrator 3 Starts the integration operation, thereafter, the output of the cascade connection system of the difference filter 2 and the integrator 3 has a flat characteristic of gain 1.

As shown in FIGS. 2D and 2E, when a stationary harmonic, that is, a harmonic whose level and phase do not change, is added to the received signal, the differential filter 2 in the preceding stage Since harmonics are completely removed,
The integral value of the output of the difference filter 2 for the carrier signal converges to zero as the carrier signal disappears. However, the actual harmonic component is constantly changing due to the opening and closing of various loads connected to the power system, and the level or phase of the harmonic changes at a certain point in time and does not return to the original state. In the case of a change in a long cycle, the change is output through the differential filter 2 and further accumulated in the integrator 3 at the subsequent stage until the level or phase of the original harmonic returns to the original level. Are continuously output, resulting in continuous noise on the carrier signal.

That is, after the switch SW of the integrator 3 shown in FIG. 2D is turned on and the integrator 3 starts the integrating operation, if a non-stationary change occurs in the harmonic before the disappearance of the carrier signal. As shown in FIG. 2 (f), the gain of the integrator 3 becomes 2 again, making it impossible to detect the disappearance of the carrier wave, so that the forced return function is required.

Therefore, when the forced-recovery timed circuit 5 is notified by the carrier arrival decision circuit 4 that the unmodulated preceding carrier A has been detected, the forced recovery timed circuit 5 starts counting time. When a certain time period slightly exceeding the continuation time has elapsed, the switch SW of the integrator 3 is turned off and the on-output of the carrier arrival determination circuit 4 is stopped, as shown in FIGS. 2 (f) and 2 (g). , The switch SW of the integrator 3 and the carrier arrival determination circuit 4 are forcibly returned to the original state.

FIG. 5 is a block diagram showing an example of a power line carrier signal receiving circuit constituted by using a broadband harmonic elimination filter 1 comprising a difference filter 2, an integrator 3, a carrier arrival judging circuit 4 and a forced recovery time limiting circuit 5. Here, a modulation scheme employing a quadrature phase shift modulation / demodulation scheme is shown.

In FIG. 5, a carrier signal transmitted via a distribution line L is received, and a band-pass filter 6 allows only a reception signal in a required frequency band to pass therethrough. The connection removes the broadband harmonics and detects the carrier signal with a stable gain, performs multiplication detection with the in-phase detector 7 and the quadrature-phase detector 8, respectively, and passes the low-pass filters 10 and 9 to remove high-frequency components. In the quadrant multiplier 11 and the phase correction data storage circuit 12, an operation for correcting the orthogonal axis is performed. The in-phase component and the quadrature component of the signal thus obtained are subjected to sign judgment by the sign judgment circuits 13 and 14 to be converted into corresponding data signals, and output from the data output terminal RD. Reference numeral 17 denotes a carrier wave disappearance determination circuit for detecting the disappearance of the carrier wave using the outputs of the low-pass filters 9 and 10, 18 a commercial frequency multiplier, and 19 a π / 2.
A phase shift circuit, 20 is an OR gate, and CD is a carrier detection terminal.

The power line carrier signal receiving circuit shown in FIG. 5 includes a bandpass filter 6 and a commercial frequency multiplier 18.
Can be configured by software (computer) except for. FIG. 6 is a flowchart showing the operation of the power line carrier signal receiving circuit constituted by software. Each time the output of the band pass filter 6 is sampled, the operation shown in FIG. Step 1
Performs A / D conversion processing in step 2, performs difference filter processing in step 2, determines whether or not a flag for detecting a carrier wave is set in step 3, and if not set,
Proceeding to step 4, a carrier arrival determination process is performed. As a result, when the arrival of the carrier wave is determined, the process proceeds to step 6 via step 5, sets the output of the carrier wave detection terminal CD to a high level, and sets a flag for detecting the carrier wave. The setting of this flag corresponds to turning on the switch SW of the integrator 3. At the same time, in step 8, the timer corresponding to the forced return timed circuit 5 is reset, and the timer starts counting. If the flag for detecting the carrier is not set, the process proceeds from step 9 to step 11 to set the register A to 0. If the flag for detecting the carrier is set, the process proceeds from step 9 to step 10 and the register A The output of the integrator 3 one cycle before the frequency is stored. Then, in step 12, the output of the difference filter 2 and the value of the register A are added and output as the output of the integrator 3. This output is subjected to band-pass filter processing in step 13 and
Performs synchronous detection processing (corresponding to processing in the detectors 7 and 8), performs low-pass filter processing (corresponds to processing in the low-pass filters 9 and 10) in step 15, and performs phase correction processing (4 in step 16). The processing by the quadrant multiplier 11 and the storage circuit 12) is performed, and in step 17, an in-phase data signal and a quadrature-phase data signal are output from the data output terminal RD. After increasing the timer for forced return in step 19 after step 18, a carrier wave disappearance determination process is performed in step 20. As a result, when it is determined in step 21 that the carrier wave has disappeared, the output of the carrier wave detection terminal CD is returned to low level in step 23, the flag for detecting the carrier wave is cleared in step 24, and this interrupt processing ends. Even if it is not determined in step 21 that the carrier wave disappears, if the timer for forced return is timed out in step 22, the output of the carrier detection terminal CD is returned to low level in step 23, Clear the set.

[0027]

As described above, according to the present invention,
It is possible to provide a broadband harmonic elimination filter capable of achieving both the elimination of harmonics of a power wave required for a power line carrier system and the wideband signal transmission characteristic for high-speed data transmission.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a broadband harmonic rejection filter for receiving a power line carrier signal according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating the operation of the broadband harmonic elimination filter shown in FIG.

FIG. 3 is a diagram illustrating a configuration and a transfer characteristic of a differential filter.

FIG. 4 is a diagram illustrating a configuration and a transfer characteristic of an integrator.

FIG. 5 is a block diagram showing an example of a power line carrier signal receiving circuit constituted by using a broadband harmonic elimination filter according to the present invention.

6 is a flowchart illustrating an example of an operation when the power line carrier signal receiving circuit in FIG. 5 is configured by software.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Broadband harmonic elimination filter 2 Difference filter 3 Integrator 4 Carrier arrival decision circuit 5 Time limit circuit for forced return 6 Bandpass filter 7 Detector 8 Detector 9 Low pass filter 10 Low pass filter 11 4 Quadrant multiplier 12 Storage circuit 13 Sign judgment Circuit 14 Sign judgment circuit 17 Carrier extinction judgment circuit 18 Commercial frequency multiplication circuit 19 Phase shift circuit A Unmodulated preceding carrier D Delay element F Sampling frequency H Harmonic H _C (z) Difference filter transfer characteristics H _I (z) Integration Transfer characteristics H _CI (z) Transfer characteristics when differential filter and integrator are cascaded I Inverting circuit k Integer (unit time) L Distribution line RD Data output terminal S Data signal SW Switch X (z) Input signal Y (Z) Output signal

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Manabu Sekizawa 3-7-1, Ichibancho, Aoba-ku, Sendai, Miyagi Prefecture Tohoku Electric Power Co., Inc. (72) Inventor Yoshiaki Hashiura Ichibancho, Aoba-ku, Sendai, Miyagi Prefecture 3-7-1, Tohoku Electric Power Co., Inc. (72) Inventor Satoshi Komazawa 2-7-1, Higashi-Gotanda, Shinagawa-ku, Tokyo (72) Inside Osaki Electric Industry Co., Ltd. (72) Inventor Takashi Emori, Higashi-Gotanda, Shinagawa-ku, Tokyo 2-7-2 Osaki Electric Industry Co., Ltd. (72) Inventor Tsuyoshi Hamagumi 2-2-7 Higashi Gotanda, Shinagawa-ku, Tokyo F-term within Osaki Electric Industry Co., Ltd. 5K046 AA03 BA00 BB05 PS01 PS05 PS11 PS51

Claims (4)

[Claims] 1. A broadband harmonic elimination filter for removing a harmonic of the power wave in a wide band when receiving a carrier signal superimposed on the power wave of the power line, wherein the filter synchronizes with a frequency of the power wave. A difference filter processing means for subtracting the received signal one cycle before the power wave frequency from the received signal at the present time; and an output of the difference filter processing means without integrating when the arrival of the carrier signal is not detected. Output,
And an integrating means for integrating and outputting one cycle before the power wave frequency when the arrival of the carrier signal is detected. 2. The broadband harmonic elimination filter according to claim 1, wherein the arrival of the carrier signal is detected using an output of the difference filter processing means. 3. The wideband harmonic rejection filter according to claim 1, wherein the integration means is returned to a state in which the input is not integrated but output as it is after a fixed time period from when the arrival of the carrier signal is detected. . 4. The wide band according to claim 1, wherein, after detecting the arrival of the carrier signal, when the disappearance of the carrier signal is detected, the integration means is returned to a state where the input is output without integrating the input. Harmonic rejection filter.