SU1746466A1 - Device for regulation and balancing of voltage on three- phase network with neutral wire - Google Patents

Abstract

Use: in electrical engineering - to improve the quality of the supply voltage in three-phase distribution networks with a neutral wire. SUMMARY OF THE INVENTION: A three-phase network with a zero wire contains a booster transformer (VDT), the primary windings of which are connected in a counter-zigzag pattern, the secondary windings are included in the dissection of each phase wire. Three switching devices are connected to each phase between the primary and secondary windings, one poles of which are combined, others are connected to the corresponding phase wire of the primary winding. Three capacitors are connected to the phases of one part of the primary winding respectively. Three other capacitors are connected to the secondary winding, which helps to filter the currents of higher harmonics. 2 Il. Yo

Description

The invention relates to electrical engineering and can be used to improve the quality of the supply voltage in three-phase zero-wire distribution networks, such as urban and rural distribution networks.

The purpose of the invention is to expand the functionality by filtering higher harmonic currents.

FIG. 1 is a schematic diagram of the device; in fig. 2 is a replacement scheme.

The device contains secondary windings 1-3 booster transformer (VDT), primary windings 4-9, asymmetrical and non-linear resistances of loads 10-12, groups of switching devices 13-15, input terminals 16-19 devices, control unit 20, two groups of capacitors 21 -23 and 24-26.

In the device replacement circuit, the following notation is accepted: Li is the inductance of the primary semi-winding of the VDT; - inductance of secondary semi-windings of VDT; Za. Ze, Zc - asymmetrical and nonlinear load resistances; Zo - zero sequence resistance; Ci is the capacitance of the first three capacitors; C2 - capacitance of the second three capacitors.

In this device, the zero-sequence currents 10y are closed through the VDT, the secondary windings of the transformer pass through, and the connection circuit of the windings of the counter-zigzag provides the ratio Zoy "Z0, therefore toy is almost equal to 1o, and the current in the neutral wire I0z is very small.

Since this scheme of connection of the primary windings of the VDT provides a very low resistance at the highest harmonic components that are multiples of three, when the device operates on nonlinear load

V

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with.

all currents of higher harmonic components, multiples of three, are closed mainly through the device, while there is no additional voltage drop on the secondary windings of the VDT, and therefore the efficiency of regulation and balancing of the output voltage of the device noticeably increases.

However, when operating on a nonlinear load on the network, other higher harmonic components of currents and voltages may occur. The device provides filtering of higher harmonic currents in the filter formed from the inductance of Li (inductance of the excitation half winding) and capacitance Ci.

The contour is tuned to a specific harmonic (for example, p 5) by selecting the capacitance parameter Ci. Since for XLI filter Xci (i.e.

pSho11 1G -sG

where (0o is the angular frequency of the main harmonic, we find

one

Ci

l ftte 2 li

Thus, in the filter assembly device, the already existing inductive element VDT field winding is used, which allows more efficient use of equipment and expanding the field of application of the device.

To enable the filtering of other harmonic currents, a second triple capacitor 24-26 is introduced into the device, which, together with the secondary long-winding windings, forms the second

filter (and Ca). The choice of parameters of these capacitors is similar to the case considered above.

The device provides filtering

harmonic currents, a multiple of three, and, for example, the fifth and seventh harmonics, i.e. practically covers the entire main harmonic composition of a distorted voltage waveform.

Claims (1)

Apparatus of the Invention A device for regulating and balancing a voltage in a three-phase network with a neutral wire, comprising booster transformer with a primary winding consisting of two half windings connected in a counter zigzag scheme and a secondary winding included in the dissection of each phase wire, three three-phase switching devices, one poles of each of which are interconnected and connected to the corresponding phase output of the primary winding, the other poles are connected respectively to the phase terminals of the secondary windings of other phases, characterized in that, in order to extend the functionality by filtering high harmonic currents, it additionally contains two groups capacitors, each of which has three capacitors, the first terminals of the capacitors in the first and second groups, respectively, are interconnected, the second terminals of the capacitors of the first group are connected respectively to the junction points of the primary windings of the primary windings in each phase, the second terminals of the capacitors of the second group are connected to the input phase terminals device clamps. W if jft jf l b ZA SHSh