SU758013A1 - Symmetric component filter - Google Patents

Description

The invention relates to the field of electrical engineering and can be used to highlight the symmetrical components of voltages and currents of the direct and reverse sequences in three-phase electrical networks. ^five

There are various filters of symmetrical components [Υ].

These filters consist of actively capacitive, actively inductive or actively - inductive - capacitive arms. ^{, 0}

The disadvantage of all filters is the error in the allocation of symmetrical components due to the passage of the filter to the output of the higher harmonic components supplied to the filter input together with the useful signal.

The closest to the claimed filter by its technical essence and the achievable effect is a filter of symmetric ’components, consisting of active - inductive and active - capacitive arms [2}.

The disadvantage of this filter is the error in the allocation of symmetrical components, due to the passage at the output of the filter voltage higher harmonic components applied to the input of the filter, together with the useful signal.

The output voltage of the filter selected for the prototype, when summing to him a three-phase voltage system is

; ω Н Π + ΐωίι

ν ⁰

one? + ίωΒ ⁰¹ СωСЯ / '

where 11 ', II ¹ ' are the voltage of the direct and reverse sequences;

operator of the three-phase voltage system.

In the absence of the input to the filter

sinfaznoy system of higher voltage

3 758013. four

harmonic components of the podstayov-

, , _n and) b - o.

ka in (1) the values ” ⁼ and ⁿ , rg ^,, g ^tsaat

_L LGB> e and) I "I 2 -; i.e. at the output of the filter voltage is proportional to the reverse sequence voltage.

The presence of higher harmonics in the input signals leads to a violation of equality (2), due to the presence at the output of the filter voltage from higher harmonics

- η, ί ί η ω Ь 2 1.

ten

1-FSSC;

15

, ι {η Ь> Ь ______ ι__

π Ικ +) ηωθ ^{+ σ} ϊ + μιω ^ π / ⁵

(five)

where ώύχ ^ is the absolute error of the filter due to higher harmonics;

P - 2, 3, 4. . . ~ serial number

harmonic components, C _p and ϋ _η

symmetrical components at higher harmonics.

The aim of the invention is to reduce the error of the filter from the higher harmonic components of the input signals. This goal is achieved by the fact that in the filter of symmetrical components containing a resistor one output of which is input, and the other output is connected to the output of the coil pitsuctqu’O

25

50

one of the output terminals of the filter, the other output of the inductor is connected to the output of the capacitor ₃₅ and the second input terminal of the filter, and the other output of the capacitor is connected to the output of another resistor and the second output terminal of the filter, and the other output of the resistor is the third input of the filter, 40 Parallel An additional capacitor is connected to the filter's inductance. And an additional coil, D ~, is connected in parallel with the filter capacitor, the values of which are chosen 45 such that the mains Formations of the formed LC - circuits were equal to each other modulo ı - / 'times the resistance values of the resistors, and one L-C circuit had an equivalent capacitive resistance, and the other L-C — the circuit equivalent of an inductor — t and in a to e with about π p from and

The drawing shows a diagram of the filter symmetric soars with a y i y and x.

The filter consists of active resistances T? | and K ₂ , inductance ld, in parallel with which capacitance C is connected, and capacitance C?, in parallel with which inductance Ts ?.

The output voltage of the filter is

5 b 4

ί - s, L L., S z_

Ct

1 -ad'-Ь ₁ with ₁

4. □ ..1 ': ± ϊΔ ¹ 62 C 2

B S

X45 SO b. about

(4ί

Provided that the network frequency

a) to k 1-ω ² b

ί. ^ν '1

5, then after substituting n simple transformations we get

“* X y ί‘ “ί A β

______________......._____

K ί, 1 - ω ² Ь ι С £) + о Ь,

, P . ..... '.? ··'; with_____

^7! · Sun to (1 ^ Ch7s ^ -l ωΕ,

Expressing linear stresses through symmetrical components and grouping the coefficients with the corresponding components, we have

· M) from 6 ₄ 1? >, 1 “with ² L C + with ² SZ,) with 6 ₄ 7 (I-with 6 ₄ with <1 + <З ² 6 _{4 ху1 -Ц} - + ·

3 ω Ь 4. K (1-ω ² · I, | C ₄ ) + ω ² L; -αω 6 _x Ί7 (1 - ω ² !, Ι C ₄ And a ω ~ 1D

(b)

For selection on the output of the filter inverse sequence, it is necessary to have a proportional component, so that the coefficient of the component

5,758013

my sequence in (7) went to zero. This is possible with the following equality:

.2, 2

+ ί *> * L ι ω L + · α ² ω ² O

and)

The solution of equation (7) gives an unambiguous relationship between the active resistances of the filter shoulders and the resistances of the filter circuits at the frequency of the network CO 1 £ CO 2

^{i 1 =} ^ ΓΤΪΓ-ω ² ^^ ⁼ 43ЧГ ^ ь ₂ 'с ₂ )' (3)

ten

15

Substituting the values and β ₂ from (8) into expression (6), we obtain the output voltage of the filter in the absence of higher harmonics

^υ ^ ί "Τ ^ ''. (9)

Comparing expressions (2) and (9), we can conclude that the output voltage of the filter, taken as a prototype, and this filter in the absence of higher harmonics. monique are the same and proportional to the voltage of the inverse sequence.

The presence of higher harmonics in the input phase voltage applied to this filter results in a measurement error equal to

2,, 2

and. + cr ι

+

,, ΐηωΙιΚΗ-η ² ω ² Ε ₁ 0 ₁ ) ίί-α ² ^ η ² ωΐ4? (^ α " ^and n +

,, оη оЦТ? (ί-η ² ω'4 ιΟ ^ ίί-αν η ² ω ^{2 2} (1 + α) η Κ ² (ΐ-π ω ^{2 2} ₁ 0 ₁ Ύ) 2 £ _ίΊ 2 _ω 2 2 _Ε

η

hee ι

+ -and

(YU)

Calculation of LP _XC1 by expression (10) with values of η —2, 3, 4 .... showed that the PSG of the measurement of the voltage of the negative sequence with the increase of the harmonics' serial number decreases sharply. And the experimental studies carried out make it possible to assert that when Q is good, the filter circuits are 0, = 0 2 - θ in resonant frequency circuits with an inductive character at a network frequency £ ^ = 51 Hz, and contours with a capacitive character at a network frequency 4 ^ - 49 Hz is already at the second harmonic, n —2, the relative error due to the higher harmonics of the proposed filter is an order of magnitude smaller than the relative error from the higher harmonics of the filter chosen for the prototype. This conclusion is consistent with formulas (3) to (10).

Connecting in parallel to the inductance of a filter consisting of active-inductive and active-capacitive arms, capacitance, and parallel to capacitance inductance distinguishes the proposed filter from the specified prototype, as the component of the error decreases from higher harmonics. As a result, the accuracy of determining symmetrical components will be increased by an order of magnitude, which will expand the field of application of the filter and eliminate the need to develop additional electoral devices, which in addition to additional costs will lead to additional errors caused by the instability of the transmission coefficient of these devices when exposed to destabilizing filters.

Claims (1)

Claim A symmetrical component filter containing a resistor, one output of which is input, and another output connected to the inductance terminal and one of the output terminals of the filter, another inductance terminal connected to the capacitor and the second input terminal of the filter, and another capacitor output and to the second output terminal of the filter, and the other output of the resistor is the third input of the filter, due to the fact that, in order to reduce the error from the higher harmonic components in of the output signals, an additional capacitor is connected parallel to the filter inductance coil, and an additional inductance coil is connected parallel to the filter capacitor, and the values of the additional inductance to the capacitor are chosen such that, at the network frequency, the resulting b - C - circuits are equal ! 3 times the resistance value of the resistors and one L-C-conΊ 75 801.3 the tour had an equivalent capacitive impedance, and the other L-C-circuit is equivalent to inductive impedance.