SU1109680A1 - Device for measuring three-phase network electrical power quality parameters - Google Patents

Abstract

DEVICE FOR MEASURING; PARAMETERS QUALITY ELECTRIC ENERGY three-phase network comprising three voltage divider, three summing element, switch, inverter voltage - code calculating unit, registration unit, a source of reference phase voltage direct sequence generator, a frequency multiplier block control, functional converter and register, with the input terminals of the device through voltage dividers connected to the first inputs of the summation elements, the first input terminal of the connection Nena with series odds mirovatolem, frequency multiplier and by the control unit, the output frequency of the multiplier is also connected to the first input reference voltage source .i-; / iU- "13 .-. Y.L.: CL 5.Y5LIOTAG {A direct sequence, the switch output through a voltage converter is the code and the calculator is connected to the registration unit, the register input, through the function converter is connected to the output of the calculator, and the outputs of the control unit are connected to the control the inputs of a switch, a voltage converter — a code, a calculator, a functional converter, and a register, characterized in that, in order to increase accuracy and speed, three controllable scales are introduced into it x three analog converter and the memory unit, the W blocks analog memory elements are connected between the outputs and the inputs of summing switch scale converters are connected between the outputs of the reference voltage source forward sequence and the second inputs of summing elements, the output of register is connected to a. the control and inputs of the scaled pre-ores: generators, the output of the former is connected to the second input of the source 00 of the direct voltage of the direct sequence, the second input of the calculator is connected to the input of the register, and the output of the control unit is connected to the control inputs of the analog memory blocks.

Description

The invention relates to information-measuring technology and can be used to measure symmetric components, as well as in the construction of information-measuring systems for monitoring the parameters of the quality of electrical energy.

A device for measuring symmetrical components of the direct and reverse sequences of three-phase voltage systems is known, comprising a side-frequency filter, a three-phase voltage system converter in a W-phase, full-wave rectifiers, a frequency-frequency filter, a voltmeter. This device allows you to measure the symmetric components of the harmonics of three-phase network voltages.

The disadvantages of this device are the use of cumbersome and complex in the manufacture of multi-phase transformers, the need to select diodes for identical volt-ampere characteristics, as well as the use of selective filters tuned to different voltage harmonics, which reduces the accuracy of determining the symmetrical voltage components.

The closest to the invention according to the technical nature and the problem to be solved is a meter of electric energy parameters of a three-phase network containing voltage dividers, summation elements, a switch, a voltage converter code, a frequency multiplier, a control unit, a computing unit, a recording unit, a reference three-phase source. Direct sequence function converter and register t 2J.

The disadvantages of the known device are relatively low accuracy and speed. When measuring the parameters of power quality, it is necessary to know in advance the nominal value of three-phase network voltages. The nominal voltage values of a three-phase network vary in the length of the transmission line. This leads to the fact that as with voltage deviations of a three-phase network (more important quality parameters as asymmetry, imbalance is measured against the background of a non-informative pair).

meter (direct sequence voltage, which is an order of magnitude or more superior to the measured informative parameter. This does not allow the power quality parameters to be measured with the required accuracy, because for real transmitters, the transmission coefficient for the non-informative parameter is different

0 from zero The conversion cycle lasts for three periods of the three-phase network voltage, which adversely affects the measurement accuracy, since with a change in the amplitude of the voltages, there are 5 errors due to non-simultaneity of the voltage readings, in addition, it is impossible to fix the rapid changes in the electric power quality parameters.

0 The aim of the invention is to improve accuracy and speed. The goal is achieved by the fact that in a device for measuring the parameters of power quality

5 three-phase network containing three voltage dividers, three summation elements, a switch, a voltage converter — a code, a calculator, a recording unit, a direct sequence reference voltage source, a driver, a frequency multiplier, a control unit, a function converter, and a register The input terminals of the device are connected via voltage dividers to the first inputs of the summation elements, the first input terminal is connected to the sequentially connected driver, frequency multiplier and the control unit, the output of the frequency multiplier is also connected to the first input of the direct voltage source of the direct sequence, the output of the switch is connected to the output of the calculator, and the outputs of the control unit are connected to the output unit via the function converter with the control inputs of the switch, the voltage converter - the code, the calculator, the functional converter of the I register, additionally 5 three controlled m an upsized converter and three analog memory blocks, with analog memory blocks connected between the outputs

summation elements and switch inputs, scale converters are connected between the outputs of the direct sequence voltage source and the second inputs of the summation elements, the register output is connected to the control inputs of the scale converters, the output of the shaper is connected to the second input of the direct sequence voltage source, the second the input of the computation unit is connected to the input of the register, and the output of the control unit is connected to the control inputs of the analog memory blocks.

The drawing shows a block circuit for measuring the electrical quality parameters of a three-phase network.

The device contains voltage dividers 1 3, summation elements 4-6, analog blocks 7–9 of memory, switch 10, voltage converter 11 – code, calculation block 12, registration block 13, direct sequence voltage source 14 of 14 converters 15-17, driver 18, frequency multiplier 19, control block 20, function converter 21, register 22, outputs 23-25 for forward, inverse, and zero sequences.

The device works as follows.

Voltage U (t / phase A enters the driver 18, from whose output pulses are removed, the period of which is equal to TX to the voltage period Ufyli,) These pulses are formed at the time of voltage passing through the zero level when the voltage decreases. correspond to the moment of the initial phase of voltage), equal to 180. The pulses from the output of the former 18 are fed to the input of the installation of the initial phase of the reference voltage of source I4. Therefore, the system of reference voltages of source 14 is always in antiphase with the voltage IdN / The pulses from the output of the former 18 also arrive at the input of the frequency multiplier 19, the period of the output pulses of which is Tu / | where P is the frequency multiplication factor., The pulses from the output of the frequency multiplier are fed to the synchronization inputs of the reference source 14 and the control unit 20.

Source 14 is digital-analog and generates stepped sine waves. After the 1 st pulse at its sync output, which is counted from the moment of the initial phase setting, the output stage

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The control unit 20, after the arrival of a pulse at the synchronization input, generates a signal at the output, which is fed to the control inputs of the analog memory blocks 7–9, and the voltages that were at their inputs at the moment of arrival of the control pulses are fixed in them. Then, according to the signals of the control unit 20, which control the switch 10, the analog memory blocks 7-9 are connected in series via

the switch 10 to the input of the voltage converter 11 is a code. The voltage conversion times to the code are strobed by the signals of the control unit 20. The output code of the I1 converter enters the block 12 computed. The reception of the code in block 12 and the control of its operation are effected by the signals of the control block 20. .

Input voltages ID (1), Ug (i) Mc. (I-) through dividers 1 - 3 voltages,

transfer coefficients of which are equal to Kdn, are fed to the first inputs of the elements 4-6 of summation, the second inputs of which are supplied with voltage from the outputs of controlled

scale converters 15-17, whose transmission coefficients are equal. Output voltages of elements 4-6 of the sum are fed to the inputs of analog blocks of 7-9 memory.

Moreover, in accordance with the description of the operation of blocks 7-11, blocks 7-9 fix instantaneous values of stresses at times ofHHti equal to (, then these

the stresses are converted into codes, respectively, ,, Net, which enter block 12.

Computing unit 12 identifies and outputs to its outputs 23-25.

voltage modules, respectively, of the direct, inverse, and zero sequences. The algorithm of operation of block 12 is described by a known sequence of formulas. By Nftl,. . 5 W J, | (pj; instantaneous voltage values are used to determine the cosine and sine orthogonal components of the phase voltages of the fundamental frequency, from which the cosine and sine orthogonal components of the forward, reverse, and zero sequences of the fundamental frequency are then calculated the moduli of the effective values of the direct, inverse, and zero sequence voltages are calculated, while learning that in the voltage at the output of blocks 7–9 there is a direct voltage system of the direct sequence, from ort The i / d 06 of the direct voltage sequence components are subtracted by the orthogonal components of the reference voltage system. The forward, reverse, and zero sequence values from the outputs 23-25 of block 12 enter the registration block 13. At this time, the operation cycle of the device ends. ... The positive qualities of the proposed device make it possible to use it as part of information measuring systems for monitoring the parameters of the quality of electrical energy.

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Claims (1)

DEVICE FOR MEASURING 'ELECTRICAL QUALITY PARAMETERS ENERGY OF A THREE-PHASE NETWORK, comprising three voltage dividers, three summation elements, a switch, a voltage-to-code converter, a calculation unit, a registration unit, a direct three-phase voltage source of direct sequence, a shaper, a frequency multiplier, a control unit, a functional converter and a register, and the input terminals of the device through voltage dividers they are connected to the first inputs of the summation elements, the first input terminal is connected to the series forwarder, hour multiplier frequency converter and the control unit, the output of the frequency multiplier is also connected to the first input of the direct sequence reference voltage source, the output of the switch through the voltage converter is a code and the calculation unit is connected to the registration unit, the register input is connected to the output of the calculation unit through the functional converter, and the outputs of the control unit connected to the control inputs of the switch, voltage-to-code converter, calculation unit, functional converter and register, characterized in that, with the aim of higher accuracy and speed, it also introduced three controllable scale converters and three analog memory blocks, with analog memory blocks connected between the outputs of the summing elements and the inputs of the switch, scale converters included between the outputs of the reference voltage source of the direct sequence and the second inputs of the summing elements, register output connected to the control inputs of large-scale converters, the output of the driver is connected to the second input of the reference voltage source In direct sequence, the second input of the calculation unit is connected to the input of the register, and the output of the control unit is connected to the control inputs of the analog memory units.