RU2003984C1 - Active power digital measuring converter - Google Patents

Abstract

The invention relates to techniques for the automatic control of electric power facilities and can be used in anti-emergency automation devices of power systems. SUMMARY OF THE INVENTION: an active power digital measuring transducer comprises a clock generator, an analog-to-digital converter, a discrete instantaneous voltage and current multiplier, a pulse counter, a demultiplexer. three accumulating adders, ele. a delay delay, two adders, two multipliers and a register. 2 ill.

Description

The invention relates to techniques for automatically controlling electric power systems and is intended for use in emergency control devices.

Known measuring transducer of active power of a single-phase current of industrial frequency 1, consisting of a multiplier of the instantaneous values of the input voltage and current and a frequency filter emitting a constant component of the voltage at the output of the multiplier (active power signal), and suppressing the harmonic component of twice the industrial frequency and the oscillatory component of industrial frequency, due to the free aperiodic component of the input current that occurs during the transient in the electric power rgeticheskoy system (interference),

The disadvantages of such an active power measuring transducer are the significant inertia caused by the frequency filter and the weak suppression of the oscillatory component of the industrial frequency.

The closest in technical essence to the proposed one is a digital measuring transducer of active power 2, containing an analog-to-digital converter (ADC), a multiplier of instantaneous voltage and current values, accumulating adders, registers, interfaces, a computing unit and a synchronization unit.

The disadvantages of the known digital measuring transducer of active, power are increased inertia due to the integration of positive and negative values of instantaneous power, and low noise immunity due to the transmission of an oscillating component of the industrial frequency to the output.

The aim of the invention is to provide noise immunity due to the almost complete suppression of the oscillatory component of the industrial frequency and to increase the speed by reducing the integration intervals.

The goal is achieved. that in a digital measuring transducer of active power containing an ADC. a multiplier of instantaneous voltage and current values, two accumulating adders and a synchronization unit, the two outputs of which are connected to the synchro inputs of the accumulating adders, a third accumulating adder, the first adder connected to the outputs of the first and third

accumulating adders, two multipliers by constant coefficients

To 1 / 481p2 (about pat / 4) and K2 1-1 / 2sin2 (ShPA T / 4)},

the first of which is connected to the output of the first adder, and the second to the output of the second accumulating adder, the second adder connected by the inputs to the outputs of the first and second multipliers, and the signal delay element from the synchronization unit, connected by the output to

the clock input of the register, the information input of which is connected to the output of the second adder, and the synchronization unit is made of series-connected clock generator, counter and

demultiplexer with three outputs.

Figure 1 shows a functional diagram of a digital measuring transducer of active power; figure 2 shows graphs illustrating it

act.

The digital measuring converter of active power consists of ADC 1, multiplier 2, accumulating adders 3, 4, 5, adders b, 7, multipliers

8.9 by constant coefficients, register 10, synchronization block 11, consisting of a clock pulse generator 12, a pulse counter 13 and a demultiplexer 14 with three outputs 15.16, 17 and a delay element 18. The converter operates as follows.

From the output of the generator 12, the clock pulses are fed to the clock input of the ADC 1.

The 8-way counter 13 and the information S-input of the demultiplexer 14. The input voltage ADI 1 and current 1Bx are input to the information input of ADC 1 and their digital values UBx (uTi), iex (uTi) with a sampling interval of MW TL are output at the input of multiplier 2 from the ADC output 1, the voltage Uex {uTi) Umsin (Wh) Hiex (uTi} lmSin (yn nTi +, where the voltage is the sum of the periodic component lmsin (UE nTi + p) and the free aperiodic component 1е,

due to the electromagnetic transient in the power system; rp and & - initial phases of the periodic components of voltage and current; 1i

d is the initial value and constant of the decay time of the free aperiodic component of the current. After the indicated voltage and current are multiplied under the usually real condition g Tn (in this case, the component is 1 pT1 / g I in the time interval t Tp), digital values are obtained at the output of the multiplier 2

U (nTi) UBx (nTi) UmSin (WhnTi + pn) x x lmsin (ftfc Hh

UmlmCOS () - UmlmCOS (nTi +

 + |) HJmlmSin (nTl + 9 n)

 Uo + Um1 Sin ((On nTi + уы f

+ Um2Sin (2 fWn rtTl + pn), (1)

consisting, as indicated, of the active POWER signal Uo k- UmlmCOS (p)

and interference-vibrational component of the industrial frequency Umisin (nTi + pn) U {) UmIsin (Oh nTi-f- (fa) and the harmonic component of the doubled industrial frequency

Um2Sin (2 (Wn Пт1 + рп2) -U (2uh} UmlmCOS (2 СОп Ш + (fa + fi),

where Umt Uml; Um2 -% JT / 2- (4

WnflTl-f pn).

 The values of U (uTi) from the output of the multiplier 2 go to the information inputs of the accumulating adders. Clock pulses from the output of the generator 12 at time intervals ti-tn; ti + AT / 2-ti + + AT / 2 + Tn; ti + DT-T1 + DT + T (Fig. 2) to the information S-input of the demultiplexer 14, pass to its outputs 15, 16, 17, respectively, depending on the address signal at the address A-input of the demultiplexer 14 coming from the counter output 13. The signals from the outputs 15, 16, 17 of the demultiplexer 14 are fed to the clock inputs of the accumulating adders, which allow recording signals. coming from the output of the multiplier 2, in the accumulating adders 3, 4, 5, respectively. At the outputs of the accumulating adders 3, 4, 5, the integrated signal values are allocated

U 1-7 I U (nTl): U2n 7 2 and (pT1):

„.-- G -„ h

 n 1

n g1

1 G + 2M

IE 7 B u (nTi), gp 2r1

where r Tn / Ti; n AT / 2Ti. From the outputs of the accumulating adders 3 and 5, the values of Uin and 1) pass to the inputs of the adder 6, and from the output of the accumulating adders 4 the values of U2H go to the input of the multiplier 9. From the output of the adder 6, the UIH + Uzi values

5

10

0

5

0

5

to the input of the multiplier 8, and from the outputs of the multipliers 8 and 9, the values of Ki (Uni + ui) and K2i2i - to the inputs of the adder 7, where

Ki- 1 / 4sin2 (OAiAT / 4); K2-H1 / 2sin2 (WnA T / 4).

From the output of adder 7, the value of Uo Ki (Uin + U3M) + K2U2H is supplied to the input of register 10. At the output of delay element 18, a pulse signal is generated that is delayed relative to the last pulse at output 17 of demultiplexer 14, and the value of the delay time is determined by the transient multipliers 8, 9 and adders 6, 7. The output of delay element 18 writes Uo information to register 10 and simultaneously resets the values recorded in accumulative adders 3, 4, 5. The process is repeated.

The action of the proposed measuring transducer of active power and the allocation of the constant component U0 at the output of the digital multiplier are based on the solution of the system of equations (Fig. 2)

{Ui Uo + Umi sin (On ti:

| U2 U0 + Umi sin od, (ti + AT / 2); (2)

(jJ3 Uo + Um1 Sin Wn (ti + AT),

determining instantaneous voltage values U U (nTi) equal to Ui, U2. U3, containing one oscillatory component of industrial circular frequency Шп. The solution of system (2) with respect to the constant component Uo is the expression

40 Uo Ki (Ui + Us),

where Ki 1/4 sin2 (o DT / 4); K2 sin2 (Uh DT / 4),

(3)

5

0

providing the separation of the constant component u0 from the value containing only the vibrational component of industrial frequency.

The elimination of the harmonic component of the doubled industrial circular frequency 2 a) n is achieved by integrating the voltage U containing the specified harmonic component during a time interval equal to its period Tn ЛУ ЛУ п п (Fig. 2). In this case, the integral values of UiH, from. Ozi and voltage U, a

U0 Kl (Um + U3w) + K2U2M.

Thus, a high noise immunity of the measuring transducer of active power of a single-phase current with an aperiodic free component is achieved — the harmonic component of the doubled industrial frequency is eliminated, and the vibrational component of the industrial frequency is almost completely suppressed, and its speed is the time Te of the active power signal extraction

single-phase current at DT 5 Tp / 2 does not exceed the duration Tp of one period of its change.

(56) Copyright certificate of the USSR No. 14516.14. class G 01 R 21/06. 1989. USSR Copyright Certificate No. 1449921. cl. G 01 R 21/06, 1989.

Claims (1)

The claims A DIGITAL ACTIVE POWER TRANSMITTER that contains an analog-to-digital converter, a multiplier of instantaneous values of the input voltage and current of industrial frequency cp, a synchronization unit and two accumulating adders, the sync inputs of which are connected to the first and second outputs of the synchronization unit, characterized in that a third accumulating adder, a delay element, two adders and two multipliers are introduced, and the synchronization unit consists of a clock generator and a counter connected in series pulses, as well as the demultiplexor, the output of the clock generator is connected to the sync input of the analog-to-digital converter and the information input of the demultiplexer, the output of the pulse counter to the address inputs of the multiplexer, and the outputs of the analog-to-digital converter to the inputs of the multiplier of instantaneous voltage and current, the output of which is connected to the information inputs of three accumulating adders, the third output of the synchronization unit is connected to the sync the input of the third accumulator accumulating to the adders the input of the delay element, the output of which is connected to the reset inputs of the accumulating adders and the input of the register, the outputs of the first and third accumulating the adders are connected to the inputs of the first adder, the output of the first adder to the input of the first multiplier, and the output of the second accumulating adder to the input of the second multiplier, the outputs of the first and second multipliers are connected to the inputs of the second adder, the output of which is connected to the second input of the register, while the multiplication factor the first multiplier Kt is 1 / 4s1p2 (cp DT / 4), and the multiplication coefficient of the second multiplier Kg I is l1 / 2s r 2 (DT / 4}. where DT / 2 is the shift interval between the beginnings of the formation of integral values at the inputs of the first, second and third of accumulators, respectively. U, + t / M (/ r + t / 3J) pЈ / &. f i /, y / y &), v№) (/ о / / Ufu) fi & 2