SU1748079A1 - Sinusoidal current active and reactive components transducer - Google Patents

Abstract

Usage: in the systems of control and management of industrial electrical equipment. SUMMARY OF THE INVENTION: The measuring transducer comprises primary voltage transducers 1 and current 2, a driver of 3 pulses, a phase shifter 4, a rectifier 5, a voltage-frequency converter 6, two reversible counters 9,10, two dividing units 11, 12. two registers , 14, two elements AND 7, 8, the converter 15 period - a code and a control block 16, which includes two null-organs 20, 21, three flip-flops 22, 23, 24, element AND 25, element OR 28, driver 29 pulses, delay element 27, button 26 and switch 30. In this converter The current in the circuit under study is transformed into a proportional pulse frequency, subjected to digital integration at certain time intervals and further digital processing of the received codes. 1 hp f-ly, 2 ill.

Description

(L

WITH

The invention relates to electrical measurements and can be used in systems for monitoring and controlling industrial electrical equipment.

A sensor for the active and reactive components of an electrical installation is known, comprising an integrator, a sample-storage unit, a phase-turning unit, a threshold unit, a reference unit, a control unit, and a matching unit.

The disadvantages of the known invention are the significant errors caused by the use of an integrator and especially a sampling-storage unit, which has a significant dynamic memory error, depending on frequency, and a storage error. The phase shifter can also introduce a noticeable error, which also depends on the frequency

input signals. It is also not clear how, in this invention, the influence of network transients, which can lead to an inaccurate conversion result, is excluded.

The closest to the proposed invention is a measuring transducer of active and reactive components of sinusoidal current, containing a series-connected primary voltage converter, a pulse shaper and a phase shifter, as well as a primary current converter, to the output of which two identical chains of series-connected synchronous detector and filter are connected low frequency, while the output of the pulse generator is connected to the control input of the first synchronous detector, Exit phase shifter h

4 00

oh h

ChE

to the control input of the second synchronous detector, the inputs of the first and second primary converters to the first and second input terminals, and the outputs of the first and second low-pass filters to the first and second output terminals of the device.

The disadvantages of this device are low conversion accuracy due to the use of synchronous detectors and especially low frequency filters having relatively large errors, which also depend on the frequency range, and the long conversion time (or low performance) caused by time transients in low-pass filters, which takes 15-20 periods of input signals.

The purpose of the invention is to improve the accuracy and speed of conversion.

The goal is achieved by the fact that the active and reactive components of the sinusoidal current are contained in the measuring transducer, which contain serially connected primary voltage transducer, pulse shaper and phase shifter, as well as primary current transducer, and the inputs of the first and second primary transducers are connected to the first and second input terminals, introduced rectifier, voltage-frequency converter, first and second three-input elements And, the first and second reversible counters, the first and the second dividing unit, the first and second registers, the period-code converter and the control unit, while the outputs of the pulse shaper and phase shifter are connected to the first inputs of the first and second And elements, respectively, the second inputs of which and the period-code converter input are interconnected and connected to the first output of the control unit, the third inputs of the first and second elements And are connected to the output of the voltage-frequency converter, connected via an input rectifier to the output of the primary current converter and to the input of the control unit, the outputs of the first and second elements I are connected to the counting inputs of the first and second reversible counters, the reverse inputs of which are interconnected and connected to the second output of the control unit, and the information outputs of the first and second reversible counters are connected to the first information inputs the first and second dividing units, the second information of which are interconnected and connected to the output of the period – code converter, the control inputs of the first and second dividing units are connected to retim output control unit, and are connected to information outputs of the first and second registers, the outputs of which are in- l first and second outputs of the device.

The goal is also achieved by the fact that the control unit contains the first and second null-organs, the first, second and third triggers, the two-input element AND, the three-input element OR, the pulse driver, the delay element, the Start button and the Operating mode switch connected to the combined inputs of the first and second zero-bodies, the output of the first zero-organ is connected to the S-input of the second trigger and the second input of the element I, the first input of which is connected to the forward output of the third trigger, and the output of the element And soi There is a diner with a counting input of the first trigger, the direct output of which is the first output of the control unit, the output of the second null organ is connected to the R input of the second trigger, the forward output of which serves as the second output of the control unit, and the inverse output of the first trigger is connected to a point, combining the third output of the control unit; the R input of the third trigger and the moving contact of the switch; Operating mode, the first fixed contact of which is open; the second fixed contact of the switch through the delay element is connected to the second input of the OR element connected by the first input with the Start button, the third input with the External Start terminal and the output through the pulse shaper with the S input of the third trigger.

The proposed transducer of the active and reactive components of the sinusoidal current is characterized by the introduction of new units: rectifier, voltage-frequency transducer, two reversible counters, two dividing units, two registers, a period-code converter, a control unit, and two three-input elements And as well as functional links between inserted and known blocks.

The limiting features of the present invention include primary voltage and current transducers, a pulse shaper, and a phase shifter at 90 °.

The essence of the invention is that it uses current conversion, the active and reactive components of which are measured, to the proportional pulse frequency subjected to further digital processing. This will lead to a transition from low-current operations of synchronous detection and low-frequency filtering in the prototype to an algebraic pulse counting at certain time intervals, which ensures the achievement of the goal and the positive effect of the invention.

1 shows a functional diagram of the device; 2 shows timing diagrams for his work.

The measuring transducer of the active and reactive components of the sinusoidal current contains a primary voltage converter 1, a primary current converter 2, a pulse shaper 3, a phase shifter 4, a rectifier 5, a voltage-frequency converter 6, the first and second three-input elements And 7, 8, the first and second reversible counters 9, 10, first and second division blocks 11.12, first and second registers 13, 14, period-code converter 15, and control block 16.

The period-code converter 15 includes a two-input element AND 17, an exemplary frequency generator 18 and a counter 19.

The control unit 16 contains the first and second zero-bodies 20, 21 of the first, second and third triggers 22, 23, 24, the two-input element AND 25, the start button 26, the delay element 27, the element OR 28, the pulse shaper 29 and the switch 30. .

In addition, the diagram shows the first input terminal 31, the second input terminal 32, the first information (or code) output 33 and the second information (or code) output 34, as well as the external trigger terminal 35 (figure 1).

The purpose of the functional units and elements of the device is unambiguously determined by their names; all of them are classical for measuring and computing equipment and can be performed on standard, well-designed circuits, usually in integral form. We only indicate that the phase shifter 4 can be made according to the scheme given in 2, the precision rectifier 5 - according to the schemes given in 3. p. 117-120, the voltage-frequency converter 6 - according to the schemes 3. p. 269-276 , 4.p.277-181, 5.p. blocks 11, 12 divisions - according to the schemes of matrix dividers 6. p. 580-590, 7. C.145, 8. C.79-80.

The period-code converter 15 implements the widely used discrete counting method or electronic-counting control unit 16, since its construction is determined by the principle of operation of the device. The remaining nodes and elements of the proposed device, as well as its converter 15, the period code, and the control unit 16 can be executed on standard, integrated chips 3, 10.

Input converter 1

the voltage is connected to the first input terminal 31 of the device, the output of this converter is connected to the input of the former of 3 pulses, the output of which is connected

0 with a line uniting the input of the phase shifter 4 and the first input of the first three-input element And 7, and the output of the phase shifter is connected to the first input of the second three-input element And 8. The second inputs of the first and

5 of the second elements And 7, 8 and the input of the period-code converter 15 are interconnected and connected to the first output of the control unit 16. Input primary current converter 2 is connected to the second

0 input terminal 32 of the device, the output of the converter is connected to the input of the control unit 16 and through the series-connected rectifier 5 and converter 6 the voltage-frequency is connected to the third

5 inputs of the elements And 7, 8, the outputs of which are connected to the counting inputs of the reversible counters 9, 10, respectively. The reverse inputs (control modes - summation or subtraction) reverse

0 counters 9, 10 are interconnected and connected to the second output of control block 16, their information (code) outputs are connected to the first information inputs of the first and second blocks

5 11, 12 divisions, the second information inputs of which are connected to the output of the period-code converter 15, the control (or permission) inputs to the third output of the control unit 16, and the information

0 (code) outputs to the first and second output registers 13, 14. The outputs of the registers 13, 14 are the first and second information (or code) outputs of the device 33, 34.

5 The first entry of the element And 17 is

the input of the converter is period-code, the second input of the element 17 is connected to the output of the generator 18 of exemplary frequency, and its output is connected to the input of the counter 19,

0 informational (or code) output of which serves as the output of the period-code converter 15.

In the control block 16, the inputs of the null organs 20, 21 are interconnected and connected to its input. The Start button 26, the output of the delay element 27 and the terminal 35 External Start are connected to the first, second and third inputs of the OR element 28, the output of which is connected via a pulse shaper 29 to the S input of the third

trigger 24 and to the reset bus (not shown in the diagram so as not to clutter up the drawing with obvious connections). The direct output of trigger 24 is connected to the first input of element AND 25, the second input of which is combined with the S input of the second trigger 23 and connected to the output the first null organ 20. The output of the element 25 is connected to the counting input of the first trigger 22, the direct output of which is the first output of the control unit 16, and its inverse output is connected to the third output of the control unit 16, the R input of the trigger 24 and the movable contact switch 30, the first fixed the contact of which is open, and the second fixed contact is connected to the input of the element 27 of the delay.

The output of the second null organ 21 is connected to the R input of the second trigger 23, the forward output of which serves as the second output of the control unit 16.

The measuring transducer operates as follows.

Voltage u (t) and current i (t) (Fig. 2, a) of the monitored AC mains are fed to the input terminals 31, 32 and from them to the primary converters 1, 2 respectively From the output of the primary converter 1, the voltage ui (t) arrives at the shaper of 3 pulses, the output of which produces rectangular pulses (Fig. 2, b), their duration is equal to half the period T of the input signals, i.e. T / 2. The output pulses of the imaging unit 3 are fed to the input of the phase shifter 4 and to the first input of the element And 7. The phase shifter 4 shifts by 90 ° rectangular pulses from the output of the imaging unit 3, and its output pulses (FIG. 2, c) enter the first input of the element I 8. To the second inputs of the And 7, 8 elements in the initial state, a inhibitory signal (low level) is supplied from the first output of the control unit 16.

In the primary converter 2, the input current with phase retention is normalized and transformed into a proportional voltage uaft), which is supplied via a rectifier. There was a voltage-frequency converter 6. From the output of the converter 6, pulses with a frequency f (t) proportional to the voltage U2 (t) and, consequently, the current I l (t) I, are fed to the third inputs of the And 7, 8 elements, but do not pass through them, like they are closed at the second entrance.

In control unit 16, the output voltage U2 (t) of the primary converter 2 is fed to the inputs of the zero-organs 20, 21, the first of which selects the voltage transitions U2 (t) through zero from the negative

regions in positive (moments of time t2, tf, .., in Fig. 2, a), and the second zero-organ 21 highlights the moments of voltage crossing U2 (t) through zero from the positive region to

negative (moments of time ts, te, ... in figure 2, a). From the output of the zero-organ 20, the pulses arrive at the S-input of the trigger 23, switching it to one state, and to the second input of the element I 25, and from the output of the zero-organ

0 21 - to the R input of the trigger 23, returning it to the zero state. The trigger 23 alternately triggers from the output pulses of the zero-organs 20, 21, and the signal at its direct output determines the polarity of the voltage

5 U2 (t) (n of current i (t)), this signal at the second output of control unit 16 is fed to the reverse inputs of reversible counters 9, 10.

In the measurement (or conversion) mode, the device is transferred by the signal

0 Start, with either one-time or manual mode (in this case, starting with the 26 Start button), or automatic mode (in this case, starting automatically with a signal

5 end of the measurement cycle coming from the inverted output of the trigger 22 through the switch 30, set to the second state Auto), or external triggering (in this case, the trigger is carried out by means of the pulse itself, input terminal 35). control Consider the operation of the device in the mode of one-off measurements, and then we specify

5 in two other modes.

In the one-time measurement mode of the device, the switch 30 Operating mode is set to the first state Manual. and the device starts up with a button

0 25 Start, when pressed, a pulse is generated at the output of the pulse driver 29 (let it be the time moment to in FIG. 2, d) arriving at the S input of the trigger 24, putting it into a single state. A high-level signal from the direct output of trigger 24 opens element I 26 at the first input, and after that the first impulse from the output of the zero-body 20 (time n) passes through element 25 at the counting input

0 flip-flop 22, set it to one. The high level signal from the direct output of the trigger 22 (FIG. 2, d) is fed through the first output of the control unit 16 to the second inputs of the And 7, 8 elements, opening them

5 second entrance.

The second output pulse of the zero-body 20 (time t), coming through the open element AND 25 to the counting input of the trigger 22, sets this trigger to the initial, zero state and low signals from its output And elements 7, 8 are closed at the second input . The high level signal from the inverted output of the trigger 22 is fed to the R input of the trigger 24, to the third output of the control unit 16 and to the moving contact of the switch 30 Operating mode. The trigger 24 is set to the initial, zero state, closed by a low level signal from the direct output of the AND element 25 on the first input. The purpose of the signal from the third output of the control unit 16 will be described below.

Thus, the elements AND 7, 8 with the signal from the first output of the control unit 16 (or from the direct output of the flip-flop 22) are opened at the second input for a time equal to the period T of the input signals (Fig. 2, d). In this interval, the element And 7 will be opened at the first input by a signal coming from the output of the imaging unit 3 pulses (FIG. 2, d) and the element And 8 by a signal coming from the output of the phase shifter 4 (FIG. 2, e).

In the open state of the And 7, 8 elements, the first and second inputs to their outputs will receive pulses from the output of the voltage-frequency converter 6 at the outputs of the counting inputs of the reversible counters 9, 10, where they are summed (or integrated) algebraically. This is achieved by the fact that when l (t) 0, the reversible counters 9,10 work on subtraction, and when i (t) 0, the reversible counters 9, 10 work on addition. The mode of operation of the reversible counters 9, 10 (summation or subtraction) is set by the signal arriving at their reverse inputs on the second output of control unit 16 (from the direct output of trigger 23). The pulses fed to the reversible counters 9, 10 for summation, are shown positive, and those arriving at subtraction are negative (figure 2, d, e),

The number of pulses recorded in the reversible counters 9, 10 is determined respectively by the expression:

T / 2

Na / 0 f (t) dt;

ST / 4

Np / 0 f (t) dt.

The frequency of the pulses at the output of the voltage-frequency converter 6

f (t) K, „Kv Kpnch l (t), (3)

Where

i (t) - In Sin ((t f)

- sinusoidal current in a controlled circuit, Im, (o, p - c), respectively, its amplitude, circular frequency and phase shift relative to the voltage u (t); Kpt - primary transmission coefficient

current transducer 2;

KV is the transfer coefficient of rectifier 5;

Кпнч - transfer coefficient of voltage-frequency converter 6.

Substituting equalities (3), (4) into expression (1), we get

T / 2 15Nl Kg, t KV Kpnch1t J 81p (yL-y) oCh1

 Kpt KB Kpnch Im to 2COS Kl la,

(five)

20 where la Im cos p - the current component is active;

Kl - Kpt KB Kpnch T / F

(6)

25 is a proportionality coefficient depending on the period T of the input signals.

Similarly, substituting equality (3.4) into expression (2) has

30zt / 4

N2 Kpt Kv Kpnch Im / Sln (ftj t- p) dt Kl lp, (7) T / 4

where p Imsln p is a reactive component

35 current.

Thus, the NI and Na codes obtained in the reversible counters 9, 10 are proportional to the active 1a and reactive p components of the current, but they also depend on

40 period T of the input signals. To eliminate this dependence, the codes NI, N2 from the information outputs of the reversible counters 9 and 10 are fed to the first information inputs of the dividing units 11, to the second

45 informational inputs of which the code comes from the converter 15 period-code.

In the period-code converter 15, an NT code of a period T of the input signals is formed. For this, the element And 17 opens on

50 to the first input by a signal from the first output of the control unit 16, the duration of which is T (FIG. 2, d). During this time, the number of pulses from the generator 18 of the exemplary frequency f0 will go to the input of the counter 19 through the element I 17 at its second input:

NT T to

(eight)

(four)

At the first information inputs (the inputs of the dividend) of blocks 11, 12, under the

The NI and N2 codes are correspondingly from the information outputs of reversible counters 9, 10, and to their combined second information inputs (divider inputs) - the NT code from the output of the 15 period-code converter (from the output of its counter 19). The signal from the third output of the control unit 16, arriving at the control inputs (or resolution inputs) of the division blocks 11.12, performs the input of the codes on the information inputs of the division blocks 11 and 12 and performs the division operation. At the outputs of blocks 11 and 12, the codes are formed, respectively.

Na Ni / NT;

NP N2 / NT.

Substituting the expressions (5), (70 in these formulas, taking into account equality (6) and relation (80)), we obtain

Na Kfa.

No K:

Kpt KV Kpnch

where K --- g - the coefficient passed

chi device.

The Na and Np codes, proportional to the active a and reactive p components of the current, from the outputs of the division blocks 11, 12 are written to the output registers 13, 14, respectively, from which they can be removed via the outputs 33 and 34 of the device or to display the measurement results, or for other uses.

In the automatic measurement mode, the switch 30 Operating mode is set to the second state - Auto. In this case, the first measurement cycle is set either by the Start button 26 or by an external trigger signal on input terminal 35, and each subsequent measurement cycle is set by the signal from the inverse output of the trigger 22 via switch 30, delay element 27, OR element 28 and pulse shaper 29 to the S input of the trigger 24. Otherwise, the operation of the device is completely repeated, as in the one-time mode.

Claims (2)

Claim 1. A transducer of active and reactive components of sinusoidal current, containing a series-connected primary voltage converter, a pulse shaper and a phase shifter, as well as a primary current converter, with the inputs of the first and second primary converters connected to the input terminals of the device; In order to improve the accuracy and speed of the conversion, additionally introduced are a rectifier, voltage-frequency converter, two And elements, two reversible counters, two dividing units, two registers, a converter period - code and control unit, while the outputs of the pulse generator and the phase shifter are connected to the first inputs of the first and second I elements, respectively; the first output of the control unit of the connector is connected to the second inputs of the AND elements and the converter input; period, the code, the output of the voltage converter is connected with the third inputs of the first and second elements And the output of the primary 5 the current converter is connected to the input of the control unit and the input of the rectifier whose output is connected to the input of the voltage-frequency converter, the outputs of the first and second elements VI are connected to the counting inputs 1 of the first and second reversible counters, the second output of the control unit is connected to the inputs of the reverse accounts of the first and second reversible counters, information outputs of which are connected to 5 by the first information inputs of the first and second dividing units, respectively; the output of the period converter — the code is connected to the second information inputs of the first and second dividing units, 0, the third output of the control unit is connected to the control inputs of the first and second division blocks, the information outputs of which are connected to the inputs of the first and second registers, the outputs of which are 5 with the first and second outputs of the device. 2. The converter according to claim 1, of which the control unit contains two null organs, three triggers, element AND, the element OR, pulse shaper, 0 delay element, start button and operating mode switch, the inputs of the first and second null organs are combined and are the input of the control unit, the output of the first null organ is connected to the input of the second trigger and the second input of the And element, the third output of the third trigger connected to the first input of the second element I, the output of which is connected to the counting input of the first trigger, direct 0 the output of which is the first output of the control unit, the output of the second null organ is connected to the reset input of the second trigger, the direct output of which is the second output of the control unit, the inverse output of the first trigger is the third output of the control unit and connected to the reset input of the third trigger and movable contact of the switch. Operating mode, the fixed contact of which through the delay element is connected to the second input of the OR element, the output of the Start button is connected to the first input of the OR element, the external start terminal with dinena with a third l / ttl J5 external hall mustache the input element OR, the output of which is connected through a pulse shaper to the input of the installation of the third trigger. fy ™ Cfycc -K Mode 4g / f 06p / r t and t