RU2169432C2 - Method of transmission and reception of signals in three- phase power network - Google Patents

Abstract

FIELD: electrical engineering, organization of communication channels with use of power lines without signal processing with high- frequency wavetraps. SUBSTANCE: technical objective of invention lies in increased noise immunity and signal transmission speed up to 50 or 100 baud. Proposed method utilizes synchronous detection of signals with the aid of integration whose start and finish are determined by characteristic points which are time moments of transition of common supply voltage through zero in one of phases of network in centers of transmission and reception. EFFECT: increased noise immunity and 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-frequency chokes, while the transmission and reception of signals are carried out on the side of 0.38 kV.

 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 invention N 2061256, 1996 (prototype). This method has inherent disadvantages.

 The claimed method solves the problem of increasing the noise immunity of signal reception and achieving a new technical result - increasing the signal transmission rate to 50 or 100 Baud.

на частоте f₁ и прямой последовательности

на частоте f₂, преобразуют в пункте приема

и U₁(f₂) соответственно в напряжения U₁(t) = U_m1cosW₁t и U₂(t)=U_m2cosW₂t, перемножают U₁(t) и U₂(t), выделяют путем фильтрации напряжение U₀(t) = U_m0cosW₀t, W₀ = 2П(f₁+f₂); f₂-f₁ = 2F; f₁ = nF; f₂ = (n+2)F; n≥10 - натуральное число, преобразуют в пункте приема U(t) в напряжение гетеродина U_г(t) = U_шгcosW_гt, W_г = W₀, перемножают U₀(t) и U_г(t), выделяют путем фильтрации постоянную составляющую U_n, интегрируют U_n в интервале времени 0 ≅ t ≅ T, T = 0,02 с при скорости передачи сигналов 50 Бод и T = 0,01 с при скорости передачи сигналов 100 Бод, при этом, начало и конец, соответственно операций передачи сигналов и интегрирования, соответствуют единым моментам времени перехода питающего напряжения U(t) через ноль одной из фаз сети в пунктах передачи и приема, при этом выполняют условие: T >> 1/f₁+f₂.In the claimed method, at the transfer point, the supply voltage U (t) of industrial frequency F is converted into three-phase currents of the reverse sequence I ₂ (f ₁ ) at a frequency f ₁ and a direct sequence I ₁ (f ₂ ) at a frequency f ₂ , these currents are transmitted via network to the receiving point, where they are converted respectively into three-phase voltage of the negative sequence

at a frequency f ₁ and direct sequence

at a frequency f ₂ , convert to a receiving point

and U ₁ (f ₂ ) respectively in the voltage U ₁ (t) = U _m1 cosW ₁ t and U ₂ (t) = U _m2 cosW ₂ t, multiply U ₁ (t) and U ₂ (t), isolated by filtration voltage U ₀ (t) = U _m0 cosW ₀ t, W ₀ = 2P (f ₁ + f ₂ ); f ₂ -f ₁ = 2F; f ₁ = nF; f ₂ = (n + 2) F; n≥10 - natural number, is converted into a reception point U (t) in the oscillator voltage U _r (t) = U _{r wr} cosW t, W _r = W _0, multiplied U ₀ (t) and U _r (t), recovered by filtering the constant component U _n , integrate U _n in the time interval 0 ≅ t ≅ T, T = 0.02 s at a signal transmission rate of 50 Baud and T = 0.01 s at a signal transmission rate of 100 Baud, while the end, respectively, of the signal transmission and integration operations, correspond to the single moments of the transition time of the supply voltage U (t) through zero of one of the phases of the network at the points of transmission and reception, while yayut condition: T >> 1 / f ₁ + f _2.

 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 unity. This is because in the claimed method 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-to-noise ratio (A. P. Manovtsev. Introduction to digital radio telemetry. Energy, Moscow, 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 station about the beginning and end of signal transmission, which allows you to correctly select the beginning and end of the integration interval 0 ≅ t ≅ T at characteristic points corresponding to common points in transition time supply voltage of one of the phases through zero at the points of transmission and reception.

 A system (drawing) that implements the claimed method, contains a synchronizer 1, a passive-active type transmitter 2, a three-phase power supply network 3, a reverse sequence symmetric component filter (FSS) 4, a direct sequence FSS 5, a multiplier 6, a broadband filter (FFS) at the transmission point ) 7, converter 8, narrow-band filter (UPF) 9, phase shifter (PV) 10, multiplier 11, low-pass filter (LPF) 12, integrator 13, synchronizer 14, PV 15.

The system works as follows:
The synchronizer 1 generates pulses at the transmission point at the moments of the transition of the supply voltage U (t) of one of the phases of the network, for a special case, phase A is ground through zero. Pulses follow with a period of T = 0.02 s at a signal transmission rate of 50 Baud and T = 0.01 s at a signal transmission rate of 100 Baud.

и

или другой форме записи:
i_A(t) = I_mcosW₁t-cos(W₂t+180)
i_B(t) = I_mcos(W₁t+120)-cos(W₂t+60)
i_C(t) = I_m(cosW₁t+240)-cos(W₂t-60),
где I_m - амплитудное значение тока. W₁ = (W_c-Л); W₂ = (W_c + Л); W_c = 2Пf_c; Л = 2ПF; f₁ = f_c-F; f₂ = f_c+F; f_c = f₁+f₂/2; П = π = 3,14, W_с - частота запуска передатчика 2.The beginning and end of signal transmission coincides with the moments when the supply voltage U (t) passes through zero. When the passive-active type 2 transmitter is operating, the following three-phase signal currents are formed in its phase wires A, B, C:

and

or other form of notation:
i _A (t) = I _m cosW ₁ t-cos (W ₂ t + 180)
i _B (t) = I _m cos (W ₁ t + 120) -cos (W ₂ t + 60)
i _C (t) = I _m (cosW ₁ t + 240) -cos (W ₂ t-60),
where I _m is the amplitude value of the current. W ₁ = (W _c -L); W ₂ = (W _c + L); W _c = 2Pf _c ; L = 2PF; f ₁ = f _c -F; f ₂ = f _c + F; f _c = f ₁ + f _2/2; P = π = 3,14, W _with - start frequency of the transmitter 2.

или в другой форме записи:
U_A(t) = U_mcosW₁t-cos(W₂t+180)
U_B(t) = U_mcos(W₁t+120)-cos(W₂t+60)
U_C(t) = U_mcos(W₁t+240)-cos(W₂t-60), (2)
где U_m - амплитуда напряжения.These currents form the voltage at the inputs of the FSS 4 and FSS 5:
U ₂ (f ₁ ) and

or in another form of notation:
U _A (t) = U _m cos W ₁ t-cos (W ₂ t + 180)
U _B (t) = U _m cos (W ₁ t + 120) -cos (W ₂ t + 60)
U _C (t) = U _m cos (W ₁ t + 240) -cos (W ₂ t-60), (2)
where U _m is the amplitude of the voltage.

At the output of the FSS 4 in the reverse sequence, which responds only to the first terms (2), the reverse phase rotation of the ABCs have:
U ₁ (t) = U _m1 cosW ₁ t, (3)
where U _m1 is the voltage amplitude.

At the output of the FSS 5 of a direct sequence, which reacts only to the second terms (2), the direct phase sequence ABC have:
U ₂ (t) = U _m2 cosW ₂ t, (4)
where U _m2 is the voltage amplitude.

The voltages U ₁ (t) and U ₂ (t) are supplied to the output of the multiplier 6. It is known that when applying to the input of the multiplier two voltages with different frequencies W ₁ and W ₂ at its output have:
U ₆ (t) = K ₁ U _m1 cos (W ₂ -W ₁ ) t + K ₂ U _m2 cos (W ₂ + W ₁ ) t, (5)
where K ₁ and K ₂ are the conversion coefficients of the multiplier 6. FAS - 7 selects the second term of voltage (6) with a frequency of W ₀ = W ₁ + W ₂ .

The bandwidth width Δ F SCF - 7 is selected from the condition of the signal transmission speed:
ΔF = 2 / t, (6)
where τ is the duration of the radio pulse. Thus, at a speed of 50 Baud - τ = 0.02 s,
ΔF (50 Baud) = 2 / 0.02 = 100 Hz,
at a speed of 100 Baud - τ = 0.01 s
ΔF (100 Baud) = 2 / 0.01 = 200 Hz,
The voltage at the output of the ShPF - 7 is equal to:
U ₀ (t) = U ₇ (t) = U _m0 cosW ₀ t, (7)
where W ₀ = 2P (f ₁ + f ₂ ); f ₁ = nF; f ₂ = (n + 2) F; n ≥ 10 is a natural number. U _m0 is the voltage amplitude, P = π.

They fulfill the condition:
T >> 1 / f ₁ + f ₂ . (8)
The voltage U ₀ (t) is applied to the first input of the multiplier 11.

Consider the operation of generating the local oscillator voltage for a special case when n is an odd number. The Converter 8 converts the sinusoidal voltage U (t) into a voltage like "meander", which can be mathematically expressed in coordinates:
Y axis - U ₈ (t)
X axis - t
U ₈ (t) = 2U _m8 (0 ≅ t ≅ T / 4)
U ₈ (t) = 0 (T / 4 ≅ T / 2), (9)
where T = 0.02 s is the period of the frequency F; 2U _m8 is the maximum meander value.

Having expanded in a Fourier series (9), they have:
U ₈ (t) = U _m8 + U _m8 4 / П (cosЛt - 1 / 3cos3Лt ... + 1 / 5cos5Лt - ... 1 / ncosnЛt). (10)
Expression (10) has a DC voltage and a set of voltages with frequencies that are multiples of the odd harmonics L, 3L, 5L ... nL.

 UPF 9 emit a voltage with a given odd harmonic n of frequency L = 2PF, which is the local oscillator voltage. P = π.

 Note: the passband of UPF 9 does not depend on the signal transmission rate, then for technical implementation it is enough to set Δ F ≅ 20 Hz.

U _g (t) = U ₉ (t) = U _mg cosW _g t, (11)
where W _g = W ₀ = nL, U _mg - the amplitude of the voltage.

Phase raids in the system eliminate the PV 10. The voltage U _g (t) is applied to the second input of the multiplier 11.

It is known that when applying to the inputs of the multiplier two voltages with the same frequencies and phases at its output have:
U ₁₁ (t) = U _m0 K ₃ cosW ₀ t + U _m0 K ₄ cos2W ₀ t + U _m0 K ₄ , (12)
where K ₃ and K ₄ are the conversion factors of the multiplier 11.

The low-pass filter 12 is isolated from (12) the voltage of the DC component U _n K ₄ .

U _n = U ₁₂ = U _m0 K ₄ . (thirteen)
Note: the cutoff frequency f _cf low-pass filter 12 for a speed of 100 Baud is chosen from the conditions:
F _cf = 1 / τ = 1 / 0.01 = 100 Hz,
where τ is the pulse duration.

This voltage is supplied to the first input of the integrator 13. The pulses of the synchronizer 14 are fed to its second input, and with the help of PV 15 these pulses are simultaneously followed by the pulses of the synchronizer 1. The frequency W _{from the} start of the passive-active type 2 transmitters is formed from the frequency F similarly to the formation local oscillator frequencies.

Let us prove the fulfillment of inequality (8) with n _min = 10; T = 0.01 s (signal rate 100 baud), f ₁ = nF = 500 Hz, f ₂ = (n + 2) F = 600 Hz. Moreover, inequality (8) will have the form:
0.01 >> 1/500 + 600,
those. it is satisfied more than 10 times, which is perfectly acceptable.

The increase of noise immunity when receiving signals is provided as follows:
1. The voltage U _n at the input of the integrator 13 is unipolar in the integration time interval 0 ≅ t ≅ T.

2. The interference voltage U _interference (t) on the integration time interval 0 ≅ t ≅ T has a variable (fluctuating around zero) component with the mathematical expectation:
M / U _interference (t) / = 0.

3. Fulfill the condition:
T >> 1 / f ₁ + f ₂ .

 The ability to receive signals with a signal to noise ratio is less than in the prototype, proves the achievement of the goal - increasing 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, at the transfer point, the supply voltage U (t) of industrial frequency F is converted into three-phase currents of the negative sequence signal

at a frequency f ₁ and currents of the direct sequence signal

at a frequency f ₂ , these currents are transmitted over the network to the receiving point, where they are converted respectively into three-phase voltages of the negative sequence

at a frequency f ₁ and direct sequence

at a frequency f ₂ , characterized in that it is converted to a receiving point

and

respectively, in the voltage U ₁ (t) = U _m1 cosW ₁ t and U ₂ (t) = U _m2 cosW ₂ t, where U _m1 and U _m2 are the amplitudes of the voltages, W ₁ = (W _c - Ω); W ₂ = (W _c + Ω); W _c = 2Pf _c ; Ω = 2PF; f ₁ = (f _c - F); f ₂ = (f _c + F);

; W _c is the start-up frequency of the passive-active type transmitter, multiply U ₁ (t) and U ₂ (t), filter out the voltage U _o (t) = U _mo cosW _o t, where W _o = 2П (f ₁ + f ₂ ); U _mo is the voltage amplitude, (f ₂ - f ₁ ) = 2F; f ₁ = nF; f ₂ = (n + 2) F; n ≥ 10 is a natural number, the supply voltage U (t) of frequency F is converted to the local oscillator voltage U _g (t) = U _mg cosW _g t, where U _mg is the voltage amplitude, W _g = W _o ; P = π, multiplied U _o (t) and the voltage U _r (t), is isolated by filtering a DC component U _n, U _n integrate in the time interval 0 <t <T, T = 0,02 C at a signaling rate of 50 Baud and T = 0.01 s at a signal transmission rate of 100 Baud, and the beginning and end, respectively, of the signal transmission and integration operations correspond to single moments of the transition of the supply voltage U (t) through zero of one of the network phases at the transmission and reception points, while satisfy the condition T >> 1 / f ₁ + f ₂ .