RU2071178C1 - Method for transmission and receiving signals in three- phase electric line and device for its implementation - Google Patents

Abstract

FIELD: electronics, communication channels which use electric power supply lines without high-frequency suppression. SUBSTANCE: device has power transformer 1, four symmetric constituent filters 2, 3, 11, 12, four narrow-band filters 4, 5, 13, 14, two multipliers 6, 15, two mixers 7, 17, two low-pass filters 8, 18, inverter 16, two transmitters 10, 19. EFFECT: increased stability to noise when signals are received with signal-to-noise ratio is much lesser than 1. 3 cl, 1 dwg

Description

 The invention relates to electrical engineering and can find application in organizing communication channels using a power line (0.38 10 - 35) kV without processing it with high-frequency chokes.

 A known method of receiving signals in a three-phase power line (ed. St. USSR N 1107750). The disadvantage of this method is the low noise immunity.

 Of the known methods described in the Scientific and Technical Bulletin on Electrification of Agriculture, vol. 2 (54), M. VIESH, 1985. Communication channel at tonal frequencies along the 10 kV line. K. I. Gutin and S. A. Tsagareishvili, a three-phase electric network is used to transfer information from a controlled point to a control center. The signals are tonal frequency pulses. In this channel, a passive-active type transmitter (prototype) is used.

 The objective of the invention is to increase the noise immunity of signal reception in a three-phase power line with the achievement of a technical result - the ability to receive signals with a signal / noise ratio is much less than unity.

The proposed method, in which the three-phase voltage of the industrial frequency F is converted to the local oscillator voltage U _g (t) = U _mg cos2Ωt (Ω = 2πF) on the receiving side, the voltage of the industrial frequency F is converted to the reverse sequence currents at a frequency f ₁ on the transmitting side, and direct sequence currents at a frequency f ₂ , when transmitting the symbol "1", transfer these currents through a three-phase power line to a receiving point, where they are converted to voltage U ₁ (t) = U _m1 cos2Ωt, voltage U ₁ (t) and U are converted _g (t) in a positive video pulse. The following operations are again introduced: on the transmitting side, the three-phase voltage of the industrial frequency F is converted into currents of the signals of the negative sequence at the frequency f ₃ and the direct sequence at the frequency f ₄ , when transmitting the symbol "0", these currents are transmitted via a three-phase power line to the receiving point, where convert them to voltage U ₂ (t) = U _m1 cos2Ωt ,, convert the voltage U ₂ (t) and U _g (t) to a negative video pulse.

 The achievement of the technical result is ensured through the use of the KIM-FM modulation system (A. Manovtsev Introduction to digital radio telemetry. M. Energia, 1967, p. 237).

 In the present invention, the symbols "1" and "0" are distinguished by changing the phase by an angle π. The amplitude of the carrier oscillations during the transmission of these symbols is the same, there are no pauses in the signals, and the signals are processed under conditions when the signal-to-noise ratio is much less than unity.

 The drawing shows a functional diagram of the proposed device.

 The device for receiving signals in a three-phase power line contains a three-phase electric network 1, to which the inputs of the first 2 and second 3 voltage filters of symmetrical components are connected, the outputs of each of which are connected respectively to the inputs of the first 4 and second 5 narrow-band filters, the outputs of each of which are respectively connected to the first and second inputs of the first multiplier 6, the output of which is connected to the first input of the first mixer 7, the output of which is connected to the input of the first low-pass filter 8, hetero 9, the input of which is connected to a three-phase electric network 1, and the output is connected to the second input of the first mixer 7, the first transmitter is a passive-active type 10, the output of which is connected to a three-phase electric network 1, the third 11 and fourth 12 voltage filters of symmetrical components, the inputs of each of which are connected to a three-phase electric network 1, and the outputs are respectively connected to the inputs of the third 13 and fourth 14 narrow-band filters, the outputs of each of which are respectively connected to the first and second inputs of the second multiplier 15, the output of which is connected to the input of the inverter 16, the output of which is connected to the first input of the second mixer 17, the output of which is connected to the input of the second low-pass filter 18, the second input of the second mixer 17 is connected to the output of the local oscillator 9, the outputs of the second passive-active type transmitter 19 are connected to a three-phase electrical network 1.

 A device that implements the proposed method works as follows.

The output of the local oscillator 9 have a local oscillator voltage
U _g (t) = U _mg cos2Ωt,
where U _{mg the} amplitude value of the voltage of the local oscillator;
Ω2πF circular frequency;
F frequency of industrial voltage.

 1. We accept the symbol "1".

,
где I_m максимальное значение тока передатчика 10.From the output of the first passive-active type transmitter 10, negative sequence currents f ₁ and direct sequence currents at frequency f ₂ are introduced into a three-phase electric network 1, the analytical value of which is described by the expressions (K. Gutin. Increasing the efficiency of information transfer in rural electric networks with a voltage of 10 kV Abstract for the degree of Ph.D. MIISP, M. 1987, p. 7):

,
where I _{m is the} maximum current value of the transmitter 10.

From these relationships it follows that currents at a frequency have a reverse phase sequence (A, C and B), i.e., the current in phase C is 120 ^o behind the current in phase A, and the current in phase B is 120 ^o behind the current in phase C. At a frequency of ω ₂ have a direct alternation of phases (A, B and C).

These currents form in a three-phase electric network 1 the voltage of the negative sequence signal U ₂ (f ₁ ) at a frequency f ₁ and the voltage of the direct sequence U ₁ (f ₂ ) at a frequency f ₂ , and (f ₁ f ₂ ) 2F. The first filter of the symmetric components of the reverse sequence 2 is tuned to the frequency f ₁ , the second filter of the symmetric components of the direct sequence 3 is tuned to the frequency f ₂ . From the outputs of the first and second filters of symmetrical components 2 and 3, the voltages are applied to the inputs of the first and second narrow-band filters 4 and 5. The bandwidths of these filters ΔF are selected from the condition ΔF≅F Hz. This is necessary so that no more than one harmonic component of the industrial frequency falls into the filter passband, which is an obstacle for signal reception. From the outputs of the first and second narrow-band filters 4 and 5, voltage frequencies f ₁ and f ₂ are fed to the inputs of the first multiplier 6.

Let the output voltage of the first narrow-band filter 4 have the signal voltage
U ₄ (t) = U _m4 cos (ω ₁ t + Φ ₁ ) (1)
From the output of the second narrow-band filter 5 we have a signal voltage
U ₅ (t) = U _m5 cos (ω ₂ t + Φ ₂ ) (2)
where Φ ₁ = Φ ₂ (3)
This follows from the principle of operation of a passive-active type transmitter.

At t≅0. The transmitter 10 at the transmission point does not work. At the reception point there are no voltage signals U ₄ (t) and U ₅ (t) described by expressions (1) and (2).

For t> 0. The transmitter 10 at the transmission point begins to work. At the receiving point, voltages U ₄ (t) and U ₅ (t) appear.

где U_m4, U_m5 амплитудные значения напряжений сигнала на входах первого умножителя 6;
К_д коэффициент передачи амплитудного детектора.The signal voltage U ₄ (t) and U ₅ (t) are supplied to the first and second inputs of the first multiplier 6, from the output of which the signal voltage U ₆ (t) is supplied to the first input of the mixer 7, and

where U _m4 , U _{m5 are the} amplitude values of the signal voltages at the inputs of the first multiplier 6;
K _{d the} gain of the amplitude detector.

Напряжение U₆(t) соответствует напряжению U₁(t) в описании формулы изобретения.Φ ₆ = (ω ₁ -ω ₂ ) t + Φ ₁ -Φ ₂ (5)
where ω ₁ = 2πf ₁ ; ω ₂ = 2πf ₂ (6)
Moreover, the condition
f ₁ f ₂ -2F
Taking into account expressions (3) and (6), expression (5) takes the form
Φ ₆ = 2π (f ₁ -f ₂ ) t + Φ ₁ -Φ ₂ = -2Ωt (8)
In view of (7), expression (4) takes the form
U ₆ (t) = A ₆ cos2Ωt (9)
Where

The voltage U ₆ (t) corresponds to the voltage U ₁ (t) in the description of the claims.

The signal voltage U ₆ (t) is supplied to the first input of the first mixer 7.

The local oscillator voltage 9 U _g (t) = U _mg cos2Ωt is supplied to the second input of the first mixer 7. Thus, two voltages with equal frequencies and phases are supplied to the first and second inputs of the first mixer 7.

где m постоянный коэффициент, зависящий от амплитуды гетеродина;
S_o крутизна характеристики нелинейного элемента первого смесителя 7;
А_o амплитудное значение,

Анализ выражения (10) показывает, что первый и второй члены являются напряжениями, имеющими частоты 2Ω и 4Ω. Последний член является положительным постоянным напряжением.The voltage at the output of the first mixer 7 is determined from the expression

where m is a constant coefficient depending on the amplitude of the local oscillator;
S _{o the} steepness of the characteristics of the nonlinear element of the first mixer 7;
And _{o the} amplitude value,

An analysis of expression (10) shows that the first and second terms are voltages having frequencies of 2Ω and 4Ω. The last term is a positive constant voltage.

The voltage U _o corresponds to a positive video pulse in the description of the claims.

The voltage U _o acts for a time t, where
0≅t≅τ ₁
τ _{1 the} duration of the transmission of the character "1".

Для выделения положительного постоянного напряжения, которое характеризует прием символа "1", напряжение с выхода первого смесителя 7 согласно (10) подают на вход первого фильтра нижних частот 8, с выхода которого имеют положительное постоянное напряжение согласно (11).

To highlight the positive DC voltage, which characterizes the reception of the symbol "1", the voltage from the output of the first mixer 7 according to (10) is fed to the input of the first low-pass filter 8, the output of which has a positive DC voltage according to (11).

 2. Reception of the character "0".

From the output of the second passive-active type transmitter 19, negative sequence currents at a frequency f ₃ and a direct sequence at a frequency f ₄ are introduced into a three-phase electric network 1. These currents form in the three-phase electric network 1 the voltage of the negative sequence signal U ₂ (f ₃ ) at a frequency f ₃ and the direct sequence U ₁ (f ₄ ) at a frequency f ₄ . The third filter of symmetrical components of the negative sequence 11 is tuned to the frequency f ₃ , the fourth filter of symmetric components of the direct sequence 12 is tuned to the frequency f ₄ . From the outputs of the third and fourth filters of symmetrical components 11 and 12, the voltages are supplied to the inputs of the third and fourth narrow-band filters 13 and 14. From the outputs of the third and fourth narrow-band filters 13 and 14, voltage frequencies f ₃ and f ₄ are applied to the inputs of the second multiplier 15.

Сравнивая выражения (9) и (14), делаем вывод, что они идентичны. Для того, чтобы отличить символ "0" от символа "1", напряжение с выхода второго умножителя подают на вход инвертора 16. Напряжение с его выхода будет равно
U₁₆(t) = -A₁₅cos2Ωt (15)
Следует отметить, что изменение фазового сдвига 180^o в выражениях (1) и (2), которые можно получить на передающей стороне, не изменяют знака в выходном напряжении умножителя, так как согласно (5) прибавление одинаковых углов к Φ₁+π и Φ₂+π даст угол Φ по выражению (8). В данном случае напряжение гетеродина 9 и напряжение сигнала на выходе инвертора 16 сдвинуты на 180^o.Let the output voltage of the third narrow-band filter 13 have the signal voltage
U ₁₃ (t) = U _m13 cos (ω ₃ t + Φ ₃ ) (12)
From the output of the fourth narrow-band filter 14 we have a signal voltage
U ₁₄ (t) = U _m14 cos (ω ₄ t + Φ ₄ ) (13)
where Φ ₃ = Φ ₄
By analogy with the reception of the symbol "1", the voltage at the output of the second multiplier 15 will be equal to
U ₁₅ (t) = A ₁₅ cos2Ωt (14)
Where

Comparing expressions (9) and (14), we conclude that they are identical. In order to distinguish the symbol "0" from the symbol "1", the voltage from the output of the second multiplier is supplied to the input of the inverter 16. The voltage from its output will be equal to
U ₁₆ (t) = -A ₁₅ cos2Ωt (15)
It should be noted that the change in the phase shift of 180 ^o in expressions (1) and (2), which can be obtained on the transmitting side, does not change the sign in the output voltage of the multiplier, since according to (5) the addition of the same angles to Φ ₁ + π and Φ ₂ + π gives the angle Φ by expression (8). In this case, the voltage of the local oscillator 9 and the signal voltage at the output of the inverter 16 are shifted by 180 ^o .

The voltage U ₁₆ (t) corresponds to the voltage U ₂ (t) in the description of the claims.

 This voltage is supplied to the first input of the second mixer 17, to the second input of which voltage is supplied from the local oscillator 9.

Это напряжение подают на второй фильтр нижних частот 18, где выделяют отрицательное постоянное напряжение, которое характеризует прием символа "0". На выходе второго фильтра нижних частот 18 имеют напряжение

Напряжение U_o соответствует отрицательному видеоимпульсу в описании формулы изобретения.The voltage at the output of the second mixer 17 U ₁₇ (t), by analogy with c (10), is determined from the expression

This voltage is supplied to the second low-pass filter 18, where a negative DC voltage is emitted, which characterizes the reception of the symbol "0". The output of the second low-pass filter 18 has a voltage

The voltage U _o corresponds to a negative video pulse in the description of the claims.

The voltage U _o acts for a time t, where
0≅t≅τ _o
τ _{o the} duration of the transmission of the character "0".

 Thus, it is proved that the proposed device implements the proposed method for transmitting and receiving signals in a three-phase electric network.

Claims (3)

1. A method of transmitting and receiving signals in a three-phase electric network, in which the symbol "1" is transmitted, for which the voltage of the industrial frequency F is converted to the reverse sequence current at a frequency f ₁ and the direct sequence current at a frequency f ₂ on the transmitting side, these currents are transmitted through a three-phase electric network to the receiving point, and "0" is transmitted in a passive pause, and signals "1" and "0" are isolated on the receiving side, characterized in that the industrial frequency voltage F is converted to the local oscillator voltage on the receiving side
U _g (t) = U _mg cos2Ωt (Ω = 2πF),
where U _{m g the} amplitude value of the voltage of the local oscillator,
currents at frequencies f ₁ and f _{2 are} converted to voltage U ₁ (t) = U _m1 cos2Ωt, and voltage U _g (t) and U ₁ (f) are converted into a video pulse corresponding to signal “1”. 2. A method of transmitting and receiving signals in a three-phase electric network, in which the symbol "1" is transmitted, for which the voltage of the industrial frequency F is converted to the reverse sequence current at a frequency f ₁ and the direct sequence current at a frequency f ₂ on the transmitting side, these currents are transmitted via a three-phase electric network to the receiving point, and “0” is transmitted in a passive pause, and “1” and “0” signals are isolated on the receiving side, characterized in that the industrial frequency voltage F is converted to the local oscillator voltage U _g (t ) = U _mg cos2Ωt (Ω = 2πF), currents at frequencies f ₁ and f _{2 are} converted to voltage U ₁ (t) = U _m1 cos2Ωt, and voltages U _g (t) and U ₁ (t) are converted into a video pulse corresponding to signal "1", and when the formation of the video pulse corresponding to the signal "0", which is transmitted in an active pause, on the transmitting side, the three-phase voltage of the industrial frequency F is converted into the reverse sequence current at a frequency of f ₃ and the direct sequence current at a frequency of f ₄ , these currents are transmitted through a three-phase electric network to reception, where currents at frequencies f ₃ and f _{4 are} converted to voltage U ₂ (t) = U _m2 cos2Ωt, the industrial frequency voltage F is converted to the local oscillator voltage U _g (t) = U _mg cos2Ωt (Ω = 2πF), and the voltages U _g (t) and U ₂ (t) are converted into a video pulse corresponding to the signal "0".  3. A device for transmitting and receiving signals in a three-phase electric network, comprising on the transmitting side a first passive-active type transmitter, the output of which is connected to a three-phase electric network, to which a receiver input is connected, characterized in that a second passive-active type transmitter is introduced, and the receiver contains a local oscillator, the first fourth voltage filters of symmetrical components, the inputs of each of which are connected to a three-phase electrical network, to which the output of the second passive-active transmitter is connected type, the first fourth narrow-band filters, the first and second multipliers, the first and second mixers, the first and second low-pass filters, an inverter, while the outputs of the first and second voltage filters of symmetrical components, respectively, through the first and second narrow-band filters are connected to the first and second inputs the first multiplier, respectively, whose output is connected to the first input of the first mixer, the output of which is connected to the input of the first low-pass filter, and the output of the local oscillator is connected to the second inputs of of the second and second mixers, and the outputs of the third and fourth voltage filters of symmetrical components, respectively, through the third and fourth narrow-band filters are connected to the first and second outputs of the second multiplier, the output of which through an inverter is connected to the first input of the second mixer, the output of which is connected to the input of the second low-pass filter .