SU1638653A1 - Electronic power/energy meter - Google Patents

Abstract

The invention relates to instrumentation engineering and can be used in the construction of active power meters and energy meters for alternating current signals. The purpose of the invention is to improve accuracy - by converting bipolar input signals into unipolar signals, obtaining instant codes from unipolar signals and forming a product sign of the two instantaneous values of current and voltage in analog form. For this purpose, an analog rectifier 6 and a sign definition unit 7 are introduced into the device. In addition, the electronic power and energy meter contains sampling and storage units 1 and 2, respectively, an analog switch 3, an analog-to-digital converter 4, a control and processing unit 5. 4 il. S (l

Description

figure 1

The invention relates to instrumentation technology and can be used in the construction of meters of active power and energy of alternating current signals.

The aim of the invention is to improve the accuracy of determining the values of energy and power.

FIG. 1 shows a functional diagram of an electronic power and energy meter; in fig. 2 is a functional block diagram of the control and processing unit; in fig. 3- functional block diagram of the sign; in fig. 4 - time diagrams of the electronic power meter and energy.

The electronic power and energy meter (Fig. 1) contains blocks 1 and 2 of sampling and storage (BVH), analog switch 3, analog-to-digital converter (ADC) 4, control and processing block 5 (CCD), analog rectifier 6 and block 7 sign definitions (BR). The input data input voltage input 1 is the input of the voltage meter, and the data input input voltage input 2 is the input of the voltage meter, which is proportional to the current in the network. The BVH 1 and 2 outputs are connected to the first and second data inputs of the analog switch 3 and БЗ 7. The BVH 1 and 2 control inputs are connected to the first output of the CPUU 5. The control input of the analogue switch 3 is connected with the second output of the CPUU 5. connected to the third output of the CPUU 5. The output of the BS 7 is connected to the input for the sign bit of the CPUU 5. The output of the analog switch 3 is connected to the input of the analog rectifier 6, the output of which is connected to the data input of the ADC 4. The output of the AFP 4 is connected to the data inputs BUO 5, the group of outputs of which is information the output of the meter.

BUO 5 can be implemented on a single-crystal microcomputer.

BUO 5 (FIG. 2) contains two digital multipliers 8 h 9, adder-subtractor 10, two registers 11 and 12, a binary counter 13, two D-flip-flops 14 and 15, three one-shot 16, 17 and 18, generator 19 reference pulses (GOI), two two-input elements AND 20 and 21, two-input element OR NOT 22 and element NOT 23. The inputs of the first (A and second (B) multipliers of multiplier 8 are interconnected and are

the data inputs of the CPUU 5, the outputs of the multiplier 8 are connected to the inputs of the second (B) multiplier 9, the inputs of the first (A) multiplier of which are connected to buses of zero and unit potentials, so that the multiplier 9 is an NT code proportional to the sampling period input signals, which is a constant value. The outputs of the multiplier 9 are connected to the inputs of the first term of the adder 10, the inputs of the second term of which are connected to the outputs of the register 11 and the inputs of the register 12. The outputs of the adder 10 are connected to the data inputs of the register 11, and the outputs of the register 12 and the meter as a whole. The synchronization input of the first multiplier multiplier 8 is connected to the direct output of the trigger 15, which is also connected to the trigger input of the one-shot 16 and is the second output of the CPU 15. The synchronization input of the second multiplier 8 is connected to the inverse output of the trigger 15, which is also connected to the synchronization inputs receiving data register 11 and trigger 14 and with the D-input of the trigger 15, the synchronization input of which is connected to the output of GOI 19, the inverse start input of the one-shot 18, the first input element And 20 and the synchronization input Receiving the first (A) of the multiplier factor 9. clock input receiving the second factor (B) of the multiplier 9 is connected to the inverted output of one-1 novibratora 16, whose output is straight

connected to a summing input counter-. 13 and is the first output of the CPUBU 5. The input of the setting of the mode of summation or subtraction of the adder 10 is connected to the output of the trigger 14, the input D of which is the input of the CPUU 5 for the sign bit. The reset input of the register 11 is connected to the output of the one-shot 17, the inverse start input of which is connected to the output of the element 21 and the first input of the element OR NOT 22, the second input of which is connected to the output of the element 20 and the output to the synchronization input of the register 12. Inverse output overflow counter 13 is connected to the first input element And 21, the second input of which is connected to the output element NO 23, the input of which, as well as the second input element And 20

connected to a single potential bus in the case of energy measurement and to a zero potential tire when measuring active power. The output of the single vibrator 18 is the third output of the CPUU 5.

BR 7 may contain (Fig. 3) two voltage comparators 24 and 25 and an EXCLUSIVE OR element 26, the output of which is the output of BR 7. The first and second inputs of the EXCLUSIVE OR element 26 are connected to the outputs of the Comparators 24 and 25, respectively, the inverse inputs of which connected to the bus of zero potential, and the direct inputs are the first and second inputs of the BR 7, respectively.

Electronic meter works as follows (figure 4).

GOI 19 generates pulses with a period T / 2, where T is the sampling period of the input periodic signals. Trigger 15 operates in a frequency divider mode with a division factor of 2 and produces pulses with a period T. For each differential signal from the output of trigger 15 of 1, a one-shot 16 is triggered, the pulse from which instantaneous values of the input voltages are recorded in BVH 1 and 2 and network current. At the end of this pulse, the instantaneous values are stored in BVH

1 and 2. The sign of the instantaneous voltage of the network is determined by the comparator 24, and the current by the comparator 25, which compares the values stored in BVH 1 and

2 instantaneous values with zero potential. In this case, if the instantaneous value is positive, a signal 1 is generated at the output of the corresponding comparator, and if it is negative, then O. The EXCLUSIVE OR 26 element, depending on the signs of the two input values, produces at its output and at the output of the BR 7 the sign from the product that is used for performing a digital integration operation when averaging instantaneous power.

The first half of the sampling period, with a single signal from the output of the trigger 15, the instantaneous voltage value stored on the UI1 is fed to the analog rectifier 6 and after rectifying to the input of the ADC 4. In the second half the same

It comes with an instantaneous value stored on the DI2. Regardless of the polarity of the voltages stored on both the DI1 and DI2, the input of the ADC 4 receives a unipolar signal, the value of which can vary between 0-1TM ( UC, where UWQKC is the maximum value of input voltages for measuring voltages. In this case, if ADC 4 has a size n, the reduced conversion error is determined by

0 | .р

Uon

II OP UMQKC

where u

on

- the reference voltage of the ADC 4, which is a constant value.

This is twice as accurate as in the case of converting a two-pole voltage, varying in the range -UMqKc -Decc, the conversion error of which is

I'm right TJ

2U0

Max

sh

In the middle of the first half of the sampling period, a one-shot 18 is triggered by a differential signal from the output of GOI 19 of 1 to O, the pulse of which by its end starts the process of converting the rectified instantaneous voltage value from the output BVH 1 to a digital code.

The resulting code is entered into the internal source of the multiplier 8 spa 0

house in

trigger output signal

15 (transition to 1 signal at its inverse output). The same signal in the trigger 14 is entered the sign of the product of two quantities stored in BVH 1 and 2, produced by the block BZ 7.

In the second half of the sampling period, the rectified instantaneous value of the voltage from the output BVH 2 and the differential code from O to 1 of the signal from the output of trigger 15 are entered into register A of multiplier 8. In a time interval equal to the delay time of operation of multiplier 9, a code appears at its output

Np .-. Nu.-N1;)

where mts. - digital equivalent of input voltage

Np is the digital equivalent of the input current.

This code is written back to the register R of the multiplier 9 by the falling edge of the pulse coming from the one-shot 16. The code N. is entered into the register A of the multiplier 9 at the rate of operation of GUI 19. After multiplying the output of the multiplier 9 appears

 N

Pi

NT

N

U; .

N

g i

which by the signal drop from the inverse output of the trigger 15 from O to 1 is subtracted or added up depending on the sign of the received product whose value is stored in the trigger 14, with the contents of the accumulating adder, built on register 1 and the combiner adder-subtractor 10, as a result register

11 the algebraic sum code of the form is formed.

Ј, e N2.SNЈ;

where 1 is the number of summed photons energy

If the meter is set to measure the energy and the signal E / P 1, then a constant signal O is received at the input of the one-vibrator 1 7 and it never starts, i.e. the contents of register 11 are never reset at the same time as the input of register reception sync

12, elements AND 20 and OR-NOT 22 receive pulses from the output of GOI 19. Thus, register 12 constantly records the contents of register 11, i.e.

e

Ne

.Nu.-hj

N

t;

which corresponds to the value of electricity,

With E / P 0, the transfer input of the register code 12 through the elements 21 and ILY-HE 22 connects the transfer output of counter 13 to the input. The same output through the element 21 and 21 is connected to the inverse trigger input of the single vibrator 17. Since Since active power is energy released per unit of time, it can be determined by dividing the energy received by the time interval. The time during which it is necessary to measure the energy is chosen from the condition T, .1U TRV, where Tvx. - input period

1VH

0

five

0

five

0

five

0

five

0

five

signal in order to create an averaging property. On the other hand, at 2J-T, where j is an arbitrary integer, the division is replaced by a shift operation. Since the shift operation does not change the form of the code, but only tpumps the comma, then at 24 T the code of the received energy at the output of the register 11 has the same form as the active power code. Counter 13 counts the number of calculation cycles. At its output, an overflow signal appears when the measurement time of Tizy 2 -T, where K is the counter width 13. In this case, the code at the output of register 11, which coincides in appearance with the active power code, is rewritten at the leading edge1 of the overflow signal into register 12 and appears at the output of the meter. At the same time, the one-shot 17 is started, which by its pulse resets the contents of register 11 to zero. Next, the process of calculating the active power in the network is repeated.

Thus, the proposed meter has a higher accuracy in determining active power and energy due to the fact that the ADC digit is used as a data bit and the sign is formed using additional hardware.

Claims (1)

Invention Formula An electronic power and energy meter containing two sampling and storage units, an analog switch, an analog-to-digital converter and a control and processing unit, the data input of the first sampling and storage unit being the voltage input of the meter, the data input of the second sampling and storage unit the input of the meter for voltage proportional to the current in the network, the outputs of the first and second sampling and storage units are connected to the first and second data inputs of the analog switch, respectively, and the inputs are controlled sample and hold units connected to the first output of the control and processing unit, the analog switch control input coupled to the second output of the control and processing unit, the start input of analog-to-digital converter coupled / with the third output of the control and processing unit, the outputs of the analog-to-digital converter are connected to the data inputs of the control and processing unit, and the group of outputs of the control and processing unit is an information output of the meter, which is additionally introduced into it rectifier and sign definition block, with input An analog rectifier is connected to the output of the analog switch, and the output is connected to the data input of an analog-digital converter, the outputs of the first and second sampling and storage units are connected to the first and second inputs of the sign determining unit, the output of which is connected to the input for the sign bit of the control unit and processing. FIG. 2 KS FIG. 3 w V / fc. $ SL FIG. four Editor A.Lezhnina Compiled by S. Khromov Tehred A. Kravchuk Proofreader L. Pilipenko Order 926 Circulation 41 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moskpa, Zh-35, 4/5 Raushsk nab. /: tL Subscription