RU2133554C1 - Method for transmitting and receiving signals over three-phase power line - Google Patents

Abstract

FIELD: electrical and communications engineering. SUBSTANCE: communication channels are organized using power lines rated at 0.38, 10, 35, and 110 kV dispensing with high-frequency line traps. Method involves synchronous detection of signals using integration, its beginning and end being determined by characteristic points which are, essentially, moments of transition of total supply voltage at transmission and reception stations. Signal transmission speed of 50 to 100 bouds is attained. EFFECT: improved noise immunity and signal transmission speed. 1 dwg

Description

 The invention relates to the field of electrical engineering and can find application in organizing communication channels using a three-phase electric network (0.38-10-35-110) kV without its processing by high chokes, while the transmission and reception of signals are performed on the side of 0.38 kV.

 A known method of transmitting and receiving signals in a three-phase electric network, which is implemented in the device by AS USSR N 1819025 class 6 08 G 19/12, 1988. The disadvantage of this method is the low noise immunity when receiving signals and low, no more than 10 Baud, the signal transmission rate.

 Closest to the claimed method is a method of transmitting and receiving signals in a three-phase electric network, which is implemented in the patent for the invention N 2061256 class 6 08 G 19/12, 1996 (prototype). This method has the same disadvantages.

 The inventive method solves the problem of increasing the noise immunity of signal reception when a new technical result is achieved - increasing the signal transmission rate to 50 or 100 Baud.

ω₁ = 2πf₁,
φ₀ - начальная фаза в пункте передачи,
Δφ₁(t) - изменение (набег) фазы в пункте приема
(и

в узкой полосе пропускания
ω₂ = 2πf₂, Δφ₂(t) - изменение (набег) фазы в пункте приема),
умножают U₁(t) и U₂(t), выделяют путем фильтрации напряжение разностей частоты

преобразуют питающее напряжение в напряжение гетеродина U_г(t) = U_mгcosω_гt, (ω_г = 2πf_г), умножают U_р(t) и U_г(t), выделяют путем фильтрации напряжение первой суммарной частоты U_Σ1(t) = U_mΣ1cosω_Σ1t

преобразуют питающее напряжение в напряжение U₃(t) = U_m3cosω₃t (ω₃ = 2π•2F), умножают U_г(t) и U_з(t), выделяют путем фильтрации напряжение второй суммарной частоты U_Σ2(t) = U_mΣ2cosω_Σ2t,

умножают U_Σ1(t) и U_Σ2(t), выделяют с помощью фильтрации однополярное напряжение сигнала U_с, интегрируют U_с в интервале времени T, при этом начало и конец интервалов передачи сигнала и интегрирования T соответствует единым моментам времени перехода питающего напряжения через ноль в пунктах передачи и приема.In the claimed method for transmitting and receiving signals in a three-phase electric network, the transmission point converts the supply voltage U (t) of industrial frequency F (supply voltage) into the current of the negative sequence signal at a frequency f ₁ and the current of a direct sequence signal at a frequency f ₂ transmit these currents through a three-phase electric network to the receiving point, the signal currents of the forward and reverse sequences are converted to the voltage of the forward and reverse sequences at frequencies f ₁ and f ₂ (f ₂ - f ₁ = 2F), they convert the voltage of the forward and reverse sequences in voltage

ω ₁ = 2πf ₁ ,
φ ₀ - the initial phase at the point of transfer,
Δφ ₁ (t) - change (incursion) of the phase at the receiving point
(and

narrow bandwidth
ω ₂ = 2πf ₂ , Δφ ₂ (t) is the change (incursion) of the phase at the receiving point),
multiply U ₁ (t) and U ₂ (t), isolate by filtering the voltage of the frequency differences

convert the supply voltage to the local oscillator voltage U _g (t) = U _{mg cosω g} t, (ω _g = 2πf _g ), multiply U _p (t) and U _g (t), filter the voltage of the first total frequency U _Σ1 (t ) = U _{mΣ1 cosω Σ1} t

they convert the supply voltage to voltage U ₃ (t) = U _m3 cosω ₃ t (ω ₃ = 2π • 2F), multiply U _g (t) and U _s (t), filter the voltage of the second total frequency U _Σ2 (t) = U _{mΣ2 cosω Σ2} t,

multiplying U _Σ1 (t) and U _Σ2 (t), recovered by filtration unipolar voltage signal U _s, integrate U _with a T time interval, the beginning and end of transmission timing signal and integrating T corresponds to a single moment of the transition time of the supply voltage via zero at points of transmission and reception.

 The increase of noise immunity when receiving signals in the claimed method is carried out through the use of synchronous detection with the subsequent integration of unipolar voltage, while it is possible to receive signals with a signal / noise ratio of less than one. This is because in the claimed method, signal processing is performed without the use of non-linear elements, i.e. there is no suppression of a weak signal by a stronger signal / interference /. Therefore, the quality of the communication channel is practically independent of the signal / interference / A ratio. P. Manovtsev. Introduction to digital radio telemetry. Energy, M., p. 242./.

 Achieving the technical result - increasing the transmission speed to 50 or 100 Baud is carried out due to the availability of information at the receiving point about the beginning and end of signal transmission, which allows you to correctly select the beginning and end of the integration interval T at characteristic points corresponding to common moments of the transition of the supply voltage through zero at points of transmission and reception.

The device (see drawing) that implements the claimed method, contains in the transfer point a synchronizer of characteristic points 1 / synchronizer /, a passive-active type transmitter 2, a three-phase electrical network 3, a voltage filter of symmetrical components of the reverse frequency sequence f ₁ 4 / FSS /, a filter the voltage of the symmetrical components of the direct sequence of frequency f ₂ 5, narrow-band filter f ₁ 6 / UPF /, narrow-band filter f ₂ 7, multiplier 8, low-pass filter 9 / low-pass filter /, local oscillator 10, multiplier 11, filter of the first total frequency ω _Σ1 -12 not linear element 13, low-pass filter 2F 14 multiplier 15, second total frequency filter ω _Σ2 -16, phase shifter 17, multiplier 18, low-pass filter 19, synchronizer 20, phase shifter 21, integrator 22.

где I_m - амплитудное значение токов на частотах ω₁ и ω₂, ω₁ = (ω₀-Ω) и ω₂ = (ω₀+Ω); ω₀ = 2πf₀; Ω = 2πF; f₁ = f₀ - F; f₂ = f₀ + F;

f₂ - f₁ = 2F.The device operates as follows:
The synchronizer 1 generates pulses at the point of transmission at the moments when the supply voltage passes through zero. Pulses follow with a period of T (100 Baud) = 0.01 sec at a transmission rate of 100 Baud and T (50 Baud) = 0.02 sec at a transmission rate of 50 Baud. The beginning and end of the transmission coincide with the moments when the supply voltage passes through zero. When the transmitter 2 in its phase wires A, B, C form the following signal currents by analogy with the prototype

where I _m is the amplitude value of currents at frequencies ω ₁ and ω ₂ , ω ₁ = (ω ₀ -Ω) and ω ₂ = (ω ₀ + Ω); ω ₀ = 2πf ₀ ; Ω = 2πF; f ₁ = f ₀ - F; f ₂ = f ₀ + F;

f ₂ - f ₁ = 2F.

где U_A, U_B, U_C - фазы напряжения сигнала.These currents form three-phase voltages of the forward and reverse sequences at the receiving point at the inputs of the FSS 4 and FSS 5, the instantaneous values of which are described by expressions (hereinafter, the phase changes in the receiving equipment are not taken into account, since phase shifters are introduced in the receiving and local oscillator paths):

where U _A , U _B , U _C - phase voltage signal.

Эти напряжения получены в широкой полосе ФСС 4 и ФСС 5, их соответственно подают на УПФ 6 и УПФ 7. На выходе УПФ 6 имеет напряжение U₁(t) согласно описанию формулы изобретения:

На выходе УПФ 7 имеют U₂(t)

где φ₀ - начальная фаза для частот ω₁ и ω₂ в пункте передачи, которые равны.From the expression / 2 / it follows that at a frequency ω ₁ they have reverse phase voltages A, C, B, and at a frequency ω _{2 they have} a direct alternation of phases A, B, C. The voltage of the negative sequence signal at a frequency ω ₁ takes FSS 4. The voltage of the direct sequence signal at a frequency of ω _{2 /} take the FSS 5. Expressions of the instantaneous values of the signal voltage at the corresponding outputs of the FSS 4 and FSS 5 has the form

These voltages are obtained in a wide band of FSS 4 and FSS 5, respectively, they are supplied to UPF 6 and UPF 7. At the output, UPF 6 has a voltage of U ₁ (t) according to the description of the claims:

At the output of UPF 7 have U ₂ (t)

where φ ₀ is the initial phase for frequencies ω ₁ and ω ₂ at the transmission point, which are equal.

This follows from the principle of operation of a passive-active type 2 transmitter, since it is impossible to start transmitting one frequency, for example, ω ₁ , but not to transmit ω ₂ , and vice versa.

Δφ ₁ (t) is the phase change for the frequency ω ₁ in the transmission path.

Несмотря на то, что f₂ - f₁ = 100 Гц, частоты f₁ и f₂ при приеме не будут перекрываться в полосе пропускания ΔF (50 Бод) и ΔF (100 Бод), т.к. частоту f₁ принимают ФСС 4 обратной последовательности, а f₂ - ФСС 5 прямой последовательности.Δφ ₂ (t) - for frequency ω ₂ .
It is known that the value of the passband of the receive path ΔF depends on the duration of the radio pulse τ. So at a transmission speed of 50 Baud with a duration of τ / 50 Baud / = 0.02 sec, at 100 Baud - τ / 100 Baud / = 0.01 sec. The passband ΔF is determined from the expressions

Despite the fact that f ₂ - f ₁ = 100 Hz, the frequencies f ₁ and f ₂ during reception will not overlap in the passband ΔF (50 Baud) and ΔF (100 Baud), because the frequency f ₁ take FSS 4 in the reverse sequence, and f ₂ - FSS 5 direct sequence.

It should be noted that the passband UPF 6 and 7 for receiving frequencies f ₁ and f ₂ should not be made equal. So, for example, at a transmission speed of 50 Baud, the passband ΔF (f ₁ ) = 100 Hz and ΔF (f ₂ ) ≪ ΔF (f ₁ ), because the multiplier according to the logic of receiving signals is similar to scheme I. Thus, when transmitting signals / symbols "1" and "0" / in channel f ₁ , where the passband ΔF (f ₁ ) = 100 Hz is selected, the output of the channel multiplier f ₁ characters "1" and "0" will repeat the transmission algorithms. In the channel f ₂ , where ΔF (f ₂ ) is deliberately chosen "wrong", ΔF (f ₂ ) ≪ ΔF (f ₁ ), the algorithm for transmitting the characters "1" and "0" will correspond to the transmission of the character "1", i.e. . it is impossible to select the transmission of the symbol "0" / pause / under this condition of choice ΔF (f ₂ ). This is due to the inertia of the process in UPF 7. Despite this, at the output of the multiplier, the symbols "1" and "0" will follow the transmission algorithm, i.e. as in channel f ₁ , where ΔF (f ₁ ) = 100 Hz.

 As an example, consider the transmission of radio pulses / symbols "1" and "0" / of the same duration. With a passive pause.

The same value of the bandwidth in the channels f ₁ and f ₂ ΔF (f ₁ ) = ΔF (f ₂ ) = 100 Hz
The duration of the radio pulse τ = 0.02 sec; K is the transmission coefficient of the multiplier 8.

Let us estimate the amplitude value at the output of the multiplier _Umout when only interference voltage is applied to its input. We set their numerical values U _m (f ₁ ) = 0.1V; U _m (f ₂ ) = 0.1V, then we get U _mout - U _m (f ₁ ) • U _m (f ₂ ) • K = 0.1 • 0.1 • K = 0.01 kV
2. Different values of the bandwidth in the channels f ₁ and f ₂
ΔF (f ₁ ) = 100 Hz;
ΔF (f ₂ ) = 10 Hz
We set the numerical value of the interference voltage U _m (f ₁ ) = 0.1V; U _m (f ₂ ) = 0.01V, then we get U _mout = 0.1 • 0.01 • K = 0.001K
In this case, the noise voltage at the output of the multiplier decreased by 10 times.

3. If there are signal and interference voltages at the outputs of the multiplier, they have the effect of reducing the interference voltage in the receiving channel f ₂ , where ΔF (f ₂ ) ≪ ΔF (f ₁ ) without reducing the signal voltage. Thus, the signal-to-noise ratio at the output of the multiplier will be greater than at its input in the receive channel f ₁ . The value ΔF (f ₁ ) must be set based on the transmission speed. (We assumed above that the multiplier is a linear system).

С учетом /7/ выражение /8/ примет вид

Из выражения /9/ следует важный вывод, что первый член не зависит от φ₀ и Δφ(t) и содержит полную информацию о сигнале /амплитуда, частота, фаза/, поэтому дальнейшую обработку сигналов производят на разностной частоте ω_p = ω₂-ω₁. Из /9/ также следует, что производить обработку на суммарной частоте ω_Σ = (ω₂+ω₁) нельзя, т.к. возникает неопределенность в определении фазы и получить синхронный прием невозможно.In the general case, Δφ ₁ (t) and Δφ ₂ (t) are functions of many variables: the nature of the load reactivity, distance, temperature, etc. Due to the fact that f ₂ - f ₁ = 2F, and 2F << f ₁ and f ₂ can be accepted for technical calculations, the condition:
Δφ ₁ (t) ≈ Δφ ₂ (t) = Δφ (t) (7)
In the multiplier 8, the voltages U ₁ (t) and U ₂ (t) are multiplied, as a result, the voltages of the difference and total frequencies

Given / 7 / expression / 8 / takes the form

An important conclusion follows from the expression / 9 / that the first term does not depend on φ ₀ and Δφ (t) and contains complete information about the signal / amplitude, frequency, phase /, therefore, further processing of the signals is performed at the difference frequency ω _p = ω ₂ - ω ₁ . From / 9 / it also follows that it is impossible to process at the total frequency ω _Σ = (ω ₂ + ω ₁ ), because uncertainty arises in determining the phase and it is impossible to obtain synchronous reception.

На выходе гетеродина 10 формируют напряжение
U₁₀(t) = U_г(t) = U_mгcosω_гt (11)
где ω_г = 2πf_г. Значение частоты гетеродина f_г выбирают из условия

где T - интервал интегрирования.The low-pass filter 9 isolates the voltage of the differential frequency. According to the description of the claims,

The output of the local oscillator 10 form a voltage
U ₁₀ (t) = U _g (t) = U _{mg cosω g} t (11)
where ω _g = 2πf _g . The value of the local oscillator frequency f _{g is} selected from the condition

where T is the integration interval.

In some previous solutions, the authors used as a description of the local oscillator voltage harmonics of the frequency of the supply voltage of 50 Hz (F). As shown by linear tests in real three-phase electrical networks, this solution has a drawback due to the instability of the frequency F, because F ≠ const and is a function of time. Therefore, you can work only with low harmonic numbers. It is known that in order to obtain an effective integration result, it is necessary to fulfill condition / 12 /, where for the frequency f _{g we} mean the frequency of the harmonic component F. For example, let us take the 40th harmonic of frequency F as the local oscillator frequency, then the moment of time F = 49.6 Hz, the 40th harmonic will not be 2000 Hz (F = 50 Hz), but 1984 Hz / F = 49.6 Hz /. When filtering, the 40th harmonic leaves the filter band / ΔF ≤ 50 Hz /, which distinguishes it. Therefore, the use of quartz local oscillator 10 allows you to select higher frequencies, which gives significantly better results in increasing the signal-to-noise ratio at the output of the integrator compared to its input.

где U_m - амплитудное значение выпрямленного напряжения. Разложение /15/ в ряд Фурье имеет вид

ФНЧ 14 выделяет напряжение U₃(t) с частотой 2F
U₁₄(t) = U₃(t) = U_m3cosω₃t (17)
где ω₃ = 2π•2F = ω_p
В умножителе 15 умножают U_г(t) и U_з(t). Выделяют с помощью фильтра 16 напряжение второй суммарной частоты ω_Σ2
U₁₆(t) = U_Σ2(t) = U_mΣ2cos_Σ2t (18)
U_Σ2 = 2π•2F+2π•f_г = 2π(2F+2f_г) (19)
Сравнивая /14/ и /19/ заключаем, что
ω_Σ1 = ω_Σ2 (20)
Напряжение U_Σ2 (t) подают на фазовращатель 17, который задает фазу в напряжении U_Σ2 (t) [канал гетеродина], которая равна фазе в напряжении U_Σ1 (t) [канал приема]. Умножают два напряжения с одинаковыми частотами и фазами U_Σ1 (t) и U_Σ2 (t) в умножителе 18 (И.С.Гоноровский. Радиотехнические цепи и сигналы. Из-во "Сов. радио" 1967 г., с. 146 (синхронный прием сигналов с одинаковыми фазами и частотами)).In the multiplier 11 multiply U _p (t) and U _g (t), the filter 12 allocate the voltage of the first total frequency
U ₁₂ (t) = U _Σ1 (t) = U _{m (Σ1)} cosω _Σ1 t (13)
Where
ω _Σ1 = ω _p + ω _g = 2π • 2F + 2πf _g = 2π (2F + f _g ) (14)
(Filter 12 could also distinguish the difference frequency ω _p1 = ω _g -ω _p , but taking into account the expression / 12 / it is advantageous to work at higher frequencies). Nonlinear element 13 can be made, for example, in the form of a step-down transformer, the load of which is a diode bridge. The voltage at its output is

where U _m is the amplitude value of the rectified voltage. The expansion of / 15 / in a Fourier series has the form

Low-pass filter 14 emits a voltage U ₃ (t) with a frequency of 2F
U ₁₄ (t) = U ₃ (t) = U _m3 cosω ₃ t (17)
where ω ₃ = 2π • 2F = ω _p
In the multiplier 15, U _g (t) and U _s (t) are multiplied. Using the filter 16, the voltage of the second total frequency ω _Σ2
U ₁₆ (t) = U _Σ2 (t) = U _mΣ2 cos _Σ2 t (18)
U _Σ2 = 2π • 2F + 2π • f _g = 2π (2F + 2f _g ) (19)
Comparing / 14 / and / 19 / we conclude that
ω _Σ1 = ω _Σ2 (20)
The voltage U _Σ2 (t) is supplied to the phase shifter 17, which sets the phase in the voltage U _Σ2 (t) [local oscillator channel], which is equal to the phase in the voltage U _Σ1 (t) [receive channel]. Multiply two voltages with the same frequencies and phases U _Σ1 (t) and U _Σ2 (t) in the multiplier 18 (I. Gonorovsky. Radio engineering circuits and signals. Because of Sov. Radio 1967, p. 146 ( synchronous reception of signals with the same phases and frequencies)).

The low-pass filter 19 extracts a constant voltage of the signal U _s , which is fed to the first input of the integrator 22, the second input of which is fed to the pulses of the synchronizer 20 through the phase shifter 21, with which the start and end moments of the signal transmission and the integration interval T are combined. The output of the integrator 22 is informational.

 The increase of noise immunity when receiving signals is provided as follows.

1. The voltage of the signals U _with on the integration interval T is unipolar. U _s grows from zero to T.

2. The interference voltage U _p (t) on the integration interval T has a variable / fluctuating near zero / component with the mathematical expectation M [U _p (t)] = 0.

где T - интервал интегрирования.3. Fulfill the condition

where T is the integration interval.

 The claimed method allows for the reception of signals with a signal / noise ratio of << 1, which proves the achievement of the goal is to increase the noise immunity of signal reception.

 A new technical result was obtained - the signal transmission rate was increased to 50 or 100 Baud.

Claims (1)

A method of transmitting and receiving signals in a three-phase electric network, according to which the transfer point converts the supply voltage U (t) of industrial frequency F to the signal current of the negative sequence at frequency f ₁ and the signal current of the direct sequence at frequency f ₂ , where f ₂ - f ₁ = 2F, the currents of the direct and negative sequence signal are converted to voltages U ₁ (t) and U ₂ (t) of the same frequency and phase shift φ _o + Δφ ₁ (t) and φ _o + Δφ ₂ (t), respectively , where φ _o is the initial phase at the point of transfer, and Δφ ₁ (t) and Δφ ₂ (t) is the phase shift at the point of reception, multiply U ₁ ( t) and U ₂ (t), isolate the voltage of the differential frequency U _p (t) by filtering, form a voltage U _g (t) with a frequency f _g >> F, multiply U _p (t) and U _g (t), isolate by filtering the voltage

the first total frequency 2F + f _g , convert the supply voltage to voltage U ₃ (t) with a frequency of 2F, multiply the voltage U _g (t) and U ₃ (t), isolate the voltage U _Σ2 (t) of the second total frequency 2F + by filtering f _g , U _Σ1 (t) and U _Σ2 (t) are multiplied, the constant component U _s is isolated from the obtained voltage by filtration, the constant component is integrated in the interval T, where

the beginning and end of the transmission intervals of the integration signal correspond to the moments of the transition of the supply voltage U (t) through zero at the points of transmission and reception.