RU2501142C2 - Power three-phase harmonic filter for supply current of non-linear loads - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: power filter contains: phase windings of inductors 1-3 connected by their starts to filter inputs 4-6; resonant secondary windings 7-9 connected by their ends to phase windings ends of inductors 1-3 and by their starts to the first outputs of capacitors 10-12; resonant third windings 13-15 to which second outputs capacitors 19-24 (or 25-27) are connected by the first outputs. The second outputs of capacitors 10-12 depending on hardware version are connected either to adjacent outputs of the filter 16-18 and to the first outputs of capacitor 19-24 (or 25-27) or to starts of adjacent resonant secondary windings 7-9 and thus form connection of capacitors into a triangle or connected to adjacent outputs of filter 16-18 or interconnected and form star-connection. The second outputs of capacitors 25-27depending on hardware version are connected either to second outputs of capacitors 10-12 thus forming a triangle-connection or interconnected thus forming star-connection or they are connected to ends of second windings 7-9.

EFFECT: expanding functionality due to improvement of consumed current quality, improving weight and dimensions of the system, increasing reliability.

9 cl, 9 dwg

Description

The invention relates to electrical engineering and may find application in power supply systems using a frequency converter for submersible motors in the oil industry and other consumers with non-linear load.

Non-linear load causes harmonic distortion of the supply voltage due to higher current harmonics, in the three-phase circuits, as a rule, the 5th, 7th, 11th, 13th, etc.

Higher harmonics of the load current in power supply systems distort the voltage shape on the buses of the supply transformers, increase energy losses in the supply networks, cause premature aging of the insulation, thereby reducing the reliability and durability of electrical equipment. That is why in developed countries, state standards have been introduced that regulate the allowable levels of harmonic voltage distortions caused by the load current (GOST 13109-97 applies in Russia).

Known passive broadband filter (US patent No. 6,127,743, H02J 1/02, 2000.03.10), consisting of a multi-winding reactor and a capacitor bank. This filter includes a blocking inductor and a filter element containing inductive and capacitive elements that form branched circuits. This filter, effectively reduces the wide range of higher harmonics of the current consumed from the power supply system.

The disadvantage of this harmonic current filter is that since all inductive filter elements are wound on a common magnetic core, there is a magnetic coupling between them, which induces current harmonics in the blocking element that penetrate directly into the power supply system, increasing the total current of higher harmonics, thereby reducing the efficiency of harmonic suppression with such a filter, and for its restoration it is necessary to increase and power up the blocking element, which, in addition to increasing the cost, leads When, to an unacceptable decrease in the voltage at the load at its nominal value, and at low loads, especially in modes close to idling, the input voltage increases unacceptably.

The closest technical solution is a device with a magnetic shunt, designed to suppress harmonics of currents generated by the load (patent No. US 2006/0197385 A1, H02J 1/02, 2006.07.09), having an input connected to the power supply system and an output connected with a load, consisting of: a magnetic core having three rods, each rod corresponding to one of the three phases of the power supply system; at least one magnetic shunt passing through all the rods and magnetically connected to the rods in their middle part; wherein the first and second part of the core on either of the two sides of the shunt contain for each phase a first element with reactance, including a phase winding having one end for connecting to the first phase and a second end, this phase winding being on the first part core; for each phase, a second element with reactance, including a first winding forming a branched circuit located on the second part and having a first end connected to the second end of the phase winding and a second end connected to the capacitor, this capacitor having a second terminal, connected to another phase or to a corresponding capacitor connected to another phase; in this case, the phase blocking winding and the corresponding resonant winding forming a branched chain are magnetically coupled for each phase using a magnetic shunt, and the core has at least one non-magnetic gap.

Thanks to this embodiment, firstly, the dimensions of the filter are reduced, and secondly, the open circuit voltage is reduced and thereby its reliability is increased.

However, this technical solution has a significant drawback, which consists in a sharp dependence of the currents of the blocking and especially resonating windings on the capacitance of the capacitor bank. Even with deviations from the nominal value of 5-10% allowed by capacitor manufacturers, excess current can reach 30-40% and lead to unacceptable overheating of the windings. Therefore, it is necessary either to overestimate the cross section of the winding conductors, or to conduct a thorough rejection of capacitors in the process of manufacturing filters; both that and another leads to their rise in price. This drawback is especially acute in the manufacture of powerful filters, for example, for variable frequency drives with a capacity of 200-2000 kW. In this case, the capacitance of the capacitors is large, and in each phase it is necessary to include several of the same type capacitors in parallel. The failure of one of them can lead to an emergency due to an increase in current by 2-3 times.

The technical result obtained by carrying out the invention is expressed in expanding the functionality by improving the quality of the current consumed from the network, improving the overall dimensions of the power supply system using a frequency converter, and increasing reliability.

The specified technical result is achieved by the fact that in the power three-phase harmonic filter of the supply current of nonlinear loads having inputs for connecting to the power supply system, and outputs for connecting to the load, it contains a magnetic core with one or more non-magnetic gaps having three rods, each rod corresponds to one of the three phases of the power supply system; for each phase contains a first element including a first phase winding having one end for connecting to an input and a second end; for each phase comprises a second element including a winding having a first end connected to a second end of the phase winding and a second end connected to a first terminal of a capacitor of the first group; for each phase contains a third element consisting of a winding for magnetic coupling with the load; characterized in that on each rod of the magnetic core corresponding to one of the three phases, the first and second and third windings are wound in opposite directions, the second end of each phase winding is connected to the corresponding phase output, and the capacitors of the first group are connected either to their second terminals or to the second ends of the second windings of adjacent phases, forming a connection of capacitors in a triangle, or the second terminals of the capacitors of the first group are interconnected, connected to a common wire and form a cond connection nsatorov first group to the star, the first ends of the third windings are interconnected to form a compound of third windings in star, and to the second ends of the third windings are connected first terminals of two capacitors of the second group, the second terminals of which are connected to the second ends of the second windings of the two adjacent phases.

The indicated technical result is also achieved by the fact that in the power three-phase harmonic filter of the supply current of nonlinear loads, the magnetic core can contain at least one magnetic shunt passing through all the rods, dividing them into two parts, and magnetically connected with these parts; while on the first part of the rod there is a phase winding, and on the second part of the rod - the second and third windings.

The specified technical result is also achieved by the fact that the power three-phase harmonic filter of the supply current of non-linear loads, which has inputs for connecting to the power supply system and outputs for connecting to the load, contains a magnetic core with one or more non-magnetic gaps, has three rods, each rod corresponding to one of the three phases of the power supply system; for each phase contains a first element including a phase winding having one end for connecting to the input and a second end; for each phase comprises a second element including a winding having a first end connected to a second end of the phase winding and a second end connected to a first terminal of a capacitor of the first group; for each phase contains a third element consisting of a winding for communication with the load; characterized in that on each rod of the magnetic core corresponding to one of the three phases, the first and second and third windings are wound in opposite directions, the first end of each third winding is connected to the second end of the corresponding phase winding, and the second end of each third winding is connected to the corresponding phase output, the second outputs of the capacitors of the first group are connected to adjacent phase outputs, and, between the phase outputs for connecting to the load, a second group of capacitors is also formed, forming compound of the triangle or between the phase outputs connected by their first terminals of the second group of capacitors, second terminals of which are connected together, are connected to ground and to form a compound of the second group of capacitors in a star.

The indicated technical result is also achieved by the fact that in the three-phase power harmonic filter of the supply current of non-linear loads, shunt capacitors of the third group can be connected in parallel to the terminals of each phase winding.

The expansion of functionality by improving the quality of current consumed from the network and improving the overall dimensions of the power supply system using a frequency converter, as well as increasing the reliability of the filter, is ensured by the use of a second and third resonant windings wound in opposite phases with a phase winding and placed on one of the rods a three-core core, on which the corresponding phase winding is placed, and by connecting the second ends of the third resonant winding threads for each phase through the respective capacitors of the first and second groups to the second ends of the second resonant windings of two adjacent phases.

Figure 1 presents the electrical schematic diagram of the first embodiment of the filter containing capacitors of the first group, forming a connection in a triangle.

Figure 2 presents the electrical schematic diagram of a second embodiment of a filter containing capacitors of the first group forming a connection in a star.

Figure 3 presents an electrical schematic diagram of a third embodiment of a filter, comprising, in each phase, third resonant windings connected to the output of the filter and capacitors of the second group forming a connection in a triangle.

Figure 4 presents the electrical schematic diagram of the fourth embodiment of the filter, containing in each phase third resonant windings connected to the output of the filter and capacitors of the second group forming a connection in a star.

Figure 5 presents the electric circuit diagram of the fifth embodiment of the filter, containing in each phase capacitors shunting the phase winding.

Figure 6 presents the first embodiment of the placement of the windings on the filter core, containing a magnetic gap on each rod.

Figure 7 shows a second embodiment of placing the windings on the filter core containing a magnetic shunt and two magnetic gaps on each rod.

On Fig presents a third variant of placing the windings on the filter core containing a magnetic shunt and six magnetic gaps on each rod.

Figure 9 presents the frequency characteristics of the elements of the inventive filter.

The three-phase power filter for harmonics of the supply current of non-linear loads in all versions (see Figs. 1-5) for each phase contains: phase windings of inductors 1 - 3 (L11. L12 and L13) connected by their own beginnings (marked with dots) to the corresponding inputs filter 4-6 (A, B, C); resonant second windings 7-9 (L21. L22 and L23), connected at their ends to the corresponding ends of the phase windings of inductors 1-3, and the beginnings to the first terminals of the corresponding capacitors 10-12 (C21, C22, C23) forming the first group; resonating third windings of inductors 13-15 (L31. L32 and L33).

In the first and second versions of the power three-phase filter of harmonics of the supply current of non-linear loads (see Fig. 1, 2) the phase windings of inductors 1-3 (L11. L12 and L13) are connected by their ends to the corresponding outputs of the filter 16-18 (A1, B1 , C1); the resonating third windings of inductors 13-15 (L31. L32 and L33) are connected to each other with their ends and form a connection in a star; to the beginnings of the resonating third inductors 13-15 are connected by their first terminals two capacitors each, forming the second group, respectively, capacitors 19 and 20 (C31, C32), 21 and 22 (C33, C34), 23 and 24 (C35, C36) . The second terminals of the capacitors 19 and 20 (C31, C32) of the second group are connected to the beginnings of the second resonant windings 7 and 8 (L21. L22), the second terminals of the capacitors 21 and 22 (C33, C34) of the second group are connected to the beginnings of the second resonant windings 7 and 9 (L22. L23), the second terminals of the capacitors 23 and 24 (C35, C36) of the second group are connected to the beginnings of the second resonant windings 8 and 9 (L22. L23).

In the first embodiment of the power three-phase filter of harmonics of the supply current of nonlinear loads (see Figure 1), the second terminals of the capacitors of the first group 10-12 (C21, C22, C23) are connected to the beginnings of the second resonant inductors 8, 9 and 7, respectively.

In the second embodiment of the power three-phase filter of harmonics of the supply current of non-linear loads (see Figure 2), the second terminals of the capacitors of the first group 10-12 (C21, C22, C23) are interconnected, connected to a common wire and form a connection of capacitors in a star.

In the third, fourth and fifth versions of the power three-phase filter for harmonics of the supply current of non-linear loads (see Figs. 3, 4, 5), the second terminals of the capacitors of the first group 10-12 (C21, C22, C23) are connected to adjacent outputs of the filter 16-18 (A1, B1, C1), namely: capacitor 10 - to the output 18 (C1); capacitor 11 - to the output 16 (A1); capacitor 12 - to the output 17 (B1); in addition, the second terminals of the capacitors of the first group 10-12 are connected to the first terminals of the capacitors of the second group 25-27 (C31, C32, C33), respectively.

In the third and fifth versions of the power three-phase filter of harmonics of the supply current of nonlinear loads (see Figs. 3 and 5), the second terminals of the capacitors of the second group 25-27 (C31, C32, C33) are connected to the second terminals of the capacitors of the first group 10-12 (C21 , C22, C23) of adjacent phases, namely: the second terminal of the capacitor 25 (C31) - to the second terminal of the capacitor 11 (C22); the second terminal of the capacitor 26 (C32) - to the second terminal of the capacitor 12 (C23); the second terminal of the capacitor 27 (C33) - to the second terminal of the capacitor 10 (C21), and form a connection of the capacitors of the second group in a triangle.

In the fourth embodiment, the power three-phase filter of harmonics of the supply current of non-linear loads (see Figure 4), the second terminals of the capacitors of the second group 25-27 (C31, C32, C33) are interconnected, connected to a common wire and form a connection of capacitors in a star.

In the third, fourth and fifth versions of the power three-phase filter of harmonics of the supply current of non-linear loads (see Figs. 3, 4, 5) for each phase, the third resonant windings of inductors 13-15 (L31. L32 and L33) are connected to their ends by phase ends inductance windings 1-3 (L11. L12 and L13), respectively, and connected to the corresponding outputs of the filter 16-18 (A1, B1, C1).

In the fifth embodiment of the power three-phase filter of harmonics of the supply current of non-linear loads (see Figure 5), shunt capacitors 28-30 (C41-C43) are connected in parallel to the phase windings of inductors 1-3 (L11. L12 and L13). Similarly to the fifth embodiment, shunt capacitors can be connected in parallel with the phase windings of inductances according to the schemes of the third and fourth versions of the power three-phase filter of harmonics of the supply current of nonlinear loads.

In the three-phase power filter of harmonics of the supply current of nonlinear loads in all versions, the phase windings 1-3, the resonating second windings 7-9 and the third resonant windings 13-15 of each phase are located on one of the three rods of the three-rod W-shaped magnetic core, the beginning of the windings are marked points (see Fig.6-8), while the magnetic core on each of the three rods may contain: one gap 31 (see Fig.6); two gaps 32, 33 and a magnetic shunt 34 passing through all the rods (see Fig.7); or, for example, six gaps 35-40 and a magnetic shunt 34 passing through all the rods (see Fig. 8). A magnetic shunt, divides all the rods into two parts, and is magnetically connected to these parts; while on the first part of the rod there is a phase winding, and on the second part of the rod - the second and third resonant windings.

The resonant second windings 7-9 and the third resonant windings 13-15 together with the capacitors connected to them form resonant circuits, while the first group of resonant circuits containing the second windings 7-9 is tuned to a resonant frequency lower than the frequency of the 5th harmonic of the mains frequency (50 Hz for Fig. 9), the second group of resonant circuits containing the third windings 13-15 - at a frequency higher than the frequency of the 5th harmonic, but so that the resulting resonant frequency of the filter as a whole was less than the 5th harmonic frequency of the supply frequency network. In Fig.9. the frequency characteristics of the inventive filter and its elements are presented: 41 - frequency response of the first resonating element, 42 - frequency response of the second resonating element, 43 - frequency response of the filter as a whole with an agreed load; where Io is the current value of the current through the winding; In - the nominal value of the current flowing through the blocking phase winding.

In this case, the phase and resonant second and third windings through the capacitors of the first and second groups are connected to each other counterclockwise, which ensures the subtraction of the currents flowing through these windings. In this case, for the first and second filter versions (see Figs. 1, 2), it is possible to obtain in the nominal load mode the harmonic coefficient of the current consumption of about 5-6% instead of 7-8% when using an LC filter containing only phase windings with connected capacitors at the output. For the third, fourth and fifth filter versions (see Figs. 3, 4, 5), it is possible to obtain a harmonic coefficient of the consumed current of the order of no more than 8% in the range of load currents from 100 to 75% of the nominal value, which is 1.4- 1.6 times better than using an LC filter containing only phase windings with capacitors connected to the output. In the fifth embodiment of the filter (see Figure 5), to improve the filtering of the consumed current at the frequencies of the 21st to 29th harmonics of the frequency of the supply network, which is necessary when using converters with a modulation frequency of 2-3 kHz in parallel with blocking phase windings 1-3 connected correction capacitors 28-30.

The inventive three-phase power filter of harmonics of the current supply of nonlinear loads can be manufactured in mass production using standard equipment.

Placing in the filter for each phase on one rod of the three phase magnetic core of the phase blocking winding, the second and third resonating windings and turning them on counter-decreases the harmonic components of the phase currents, and connecting the third resonant windings through the capacitors of the second group to adjacent phases extends the range of variation of the load currents filter with its effective suppression of the harmonic components of the current to the values required by GOST, thereby reducing the overall dimensions of the filter and increasing its reliability.

Claims (9)

1. The three-phase power filter for harmonics of the supply current of nonlinear loads, which has inputs for connecting to the power supply system and outputs for connecting to the load, contains a magnetic core with one or more non-magnetic gaps, having three rods, each rod corresponding to one of the three phases of the power supply system ; for each phase contains a first element including a first phase winding having one end for connecting to an input and a second end; for each phase comprises a second element including a winding having a first end connected to a second end of the phase winding and a second end connected to a first terminal of a capacitor of the first group; for each phase contains a third element consisting of a winding for magnetic coupling with the load, characterized in that on each rod of the magnetic core corresponding to one of the three phases, the first and second and third windings are wound in opposite directions, the second end of each phase winding is connected with the corresponding phase output, the second terminals of the capacitors of the first group are connected to the second ends of the corresponding second windings of adjacent phases, forming a connection of capacitors in a triangle, the first ends of the third windings are connected They are interconnected, forming a connection of the third windings into a star, and to the second ends of the third windings are connected the first terminals of two capacitors of the second group, the second terminals of which are connected to the second ends of the second windings of two adjacent phases. 2. The three-phase power harmonic filter of the supply current of nonlinear loads according to claim 1, characterized in that the magnetic core contains at least one magnetic shunt passing through all the rods, dividing them into two parts, and magnetically connected to these parts; while on the first part of the rod there is a phase winding, and on the second part of the rod - the second and third windings. 3. A three-phase power filter for harmonics of the supply current of non-linear loads, which has inputs for connecting to the power supply system and outputs for connecting to the load, contains a magnetic core with one or more non-magnetic gaps, having three rods, each rod corresponding to one of the three phases of the power supply system ; for each phase contains a first element including a first phase winding having one end for connecting to an input and a second end; for each phase comprises a second element including a winding having a first end connected to a second end of the phase winding and a second end connected to a first terminal of a capacitor of the first group; for each phase contains a third element consisting of a winding for magnetic coupling with the load, characterized in that on each rod of the magnetic core corresponding to one of the three phases, the first and second and third windings are wound in opposite directions, the second end of each phase winding is connected with the corresponding phase output, the second terminals of the capacitors of the first group are interconnected, connected to a common wire and form a connection of the capacitors of the first group in a star, the first ends of the third windings are connected between fight forming compound third windings in star, and to the second ends of the third windings are connected first terminals of two capacitors of the second group, the second terminals of which are connected to the second ends of the second windings of the two adjacent phases. 4. The power three-phase harmonic filter of the supply current of nonlinear loads according to claim 3, characterized in that the magnetic core contains at least one magnetic shunt passing through all the rods, dividing them into two parts, and magnetically connected to these parts; while on the first part of the rod there is a phase winding, and on the second part of the rod - the second and third windings. 5. The three-phase power filter for harmonics of the supply current of nonlinear loads, which has inputs for connecting to the power supply system and outputs for connecting to the load, contains a magnetic core with one or more non-magnetic gaps, having three rods, each rod corresponding to one of the three phases of the power supply system ; for each phase contains a first element including a phase winding having one end for connecting to the input and a second end; for each phase comprises a second element including a winding having a first end connected to a second end of the phase winding and a second end connected to a first terminal of a capacitor of the first group; for each phase contains a third element, consisting of a winding for communication with the load, characterized in that on each rod of the magnetic core corresponding to one of the three phases, the first and second and third windings are wound in opposite directions, the first end of each third winding is connected to the second end of the corresponding phase winding, and the second end of each third winding is connected to the corresponding phase output, the second terminals of the capacitors of the first group are connected to adjacent phase outputs, and between adjacent phase Exit connected to its first and second terminals of the second group of capacitors forming the compound of the second group of capacitors in a triangle. 6. The three-phase power harmonic filter of the supply current of nonlinear loads according to claim 5, characterized in that the magnetic core contains at least one magnetic shunt passing through all the rods, dividing them into two parts, and magnetically connected to these parts; while on the first part of the rod there is a phase winding, and on the second part of the rod - the second and third windings. 7. The three-phase power harmonic filter of the supply current of nonlinear loads according to claim 5, characterized in that the shunt capacitors of the third group are connected in parallel to the terminals of each phase winding. 8. The three-phase power filter for harmonics of the supply current of nonlinear loads, which has inputs for connecting to the power supply system and outputs for connecting to the load, contains a magnetic core with one or more non-magnetic gaps, having three rods, each rod corresponding to one of the three phases of the power supply system ; for each phase contains a first element including a phase winding having one end for connecting to the input and a second end; for each phase comprises a second element including a winding having a first end connected to a second end of the phase winding and a second end connected to a first terminal of a capacitor of the first group; for each phase contains a third element, consisting of a winding for communication with the load, characterized in that on each rod of the magnetic core corresponding to one of the three phases, the first and second and third windings are wound in opposite directions, the first end of each third winding is connected to the second end of the corresponding phase winding, and the second end of each third winding is connected to the corresponding phase output, the second terminals of the capacitors of the first group are connected to adjacent phase outputs, and between the phase outputs By connecting their first terminals of the second group of capacitors, second terminals of which are connected together, are connected to a common wire to form a compound of the second group of capacitors in a star. 9. The three-phase power harmonic filter of the supply current of nonlinear loads according to claim 8, characterized in that the magnetic core contains at least one magnetic shunt passing through all the rods, dividing them into two parts, and magnetically connected to these parts; while on the first part of the rod there is a phase winding, and on the second part of the rod - the second and third windings.

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