SU1359758A1 - Symmetric component filter - Google Patents

Abstract

The invention can be used in measuring devices of automatic control of electric power systems. The purpose of the invention is to increase measurement accuracy. The filter contains an integrator 2 and a divider made up of active-reactive elements 7 and 8. The introduction of multiplier 1, amplitude detectors 3 and 4, and adder 5 greatly reduces the effect of frequency variation on the output signals of the filter. I il. (L 00 SP co 00 a

Description

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The invention relates to electrical engineering and can be used in measuring devices for automatic control of electrical power systems.

The aim of the invention is to improve the measurement accuracy by eliminating errors due to changes in network frequency.

The drawing shows a block diagram of a symmetrical component filter.

The device contains a series-connected multiplying unit 1, an integrator 2 and a first detector 3 amps-5 liters, a second detector 4 amplitudes, an adder 5, the outputs of the first 3 and second 4 amplitude detectors and the constant-voltage source 6 are connected to the corresponding inputs, the output of the adder 5 is connected to one of the inputs of the multiplying unit 1, the second input of which is combined with the input of the second amplitude detector 4 and connected to phase C. Between phases A and B a divider from active-reactive elements 7 and 8 is turned on, the midpoint to expensively connected to the second input of the integrator 2.

The forward and reverse sequence signals are removed from phases A, B and the integrator output.

The device works as follows.

The signal at the output of the integrator 2 is equal to (and ")

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, 7p transfer ratio of 40

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UooK nominal frequency O) i the amplitude of the voltage between the points OCj the transfer ratio of the multiplying unit 1. If the value of K is 1 and constant, then the signals taken from the integrator output are inversely proportional to the frequency of the mains supply.

In the device, the coefficient K is changed in such a way as to eliminate the effect of frequency variation on the integrator voltage. For this, the first amplitude detector 3 is connected to the output of the integrator, and the phase C is the second amplitude detector 4. Signals from the detectors

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and,

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fed to the adder 5, which implements the function

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Where

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OUT2:

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and.

 with

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- signal at the output of the adder;

- totalizer transfer coefficient for all inputs;

- constant voltage

selected so that at the nominal frequency provided the condition K, and 1 K.

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List 3 K. Uoc CORC

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Assume that the network frequency has increased, then

  to

. 3 (oRC The signal at the output of adder 5, i.e. K, increases and, consequently, the resulting transfer coefficient of integrator 2 and multiplier block 1 varies slightly. The error in the change of integrator transfer coefficient from frequency is smaller, the greater the gain coefficient of adder K

Similarly, the circuit works at lower frequencies.

Thus, the effect of frequency variation on the filter output is significantly attenuated. :

5 of the invention

A symmetrical component filter containing an integrator is two series-connected active-reactive Q elements, one of which is connected to phase A, the second active-reactive element is connected to phase B, the common

Vyshod active-reactive elements.

I

connected to the integrator input with a transfer factor-J and with a common pin, the output terminals of the filter are phases A and B and the integrator output, characterized in that, c.

3 1359758

the purpose of increasing the accuracy by the mouth, the amplitude detector is connected to the second of the errors due to the input of the adder, the output of which

by varying the frequency of the network, the two detector units are added to the second input to the multiplier, and the first input from the sigmmator

amplitude, the multiplier block of the I.Sum-connected through the second detector ammator, the phase C is connected to the amplitude of the phase C, and the third input of the integrator through the multiplier is connected to the output of the source

unit, the integrator output through the first voltage.

Claims (1)

The formula is composed of two components, a symmetrical filter containing an integrator, which are connected actively – reactively, then the signals taken from the output of the integrator; inversely proportional to the frequency of the mains. In the device, the coefficient K is changed in such a way as to eliminate the influence of a frequency change on the integrator voltage. To do this, the first amplitude detector 3 is connected to the integrator output, and the amplitude detector 4 is connected to the Srtoroy phase. There are signal elements, one of which is connected to phase A, the second active-reactive element is connected to phase B, the general output of the active-reactive elements ... I is connected to the integrator input with a transmission coefficient of 43 43 - and with a common bus, the output terminals of the filter are phases A and B and the integrator output, characterized in that, p. In order to increase accuracy by eliminating errors caused by a change in the network frequency, two amplitude detectors, a multiplier unit and an adder are additionally introduced into it, with phase C connected to the integrator input through the multiplier unit, the integrator output through the first 1359758 A ⁴ amplitude detector is connected to the second input of the adder, the output of which is connected to the second input of the multiplier of the _5th block, and the first input of the adder is connected through the second amplitude detector to phase C, and the third input of the adder is connected to the output of the constant voltage source.