RU2811981C1 - Universal balancing device for four-wire electrical networks - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention can be used to compensate for negative and zero sequence currents caused by the fundamental frequency current, as well as additional direct, negative and zero sequences caused by higher harmonic components of currents in three-phase electrical networks when connecting to it a three-phase asymmetrical load of consumers with nonlinear current-voltage characteristic. A device for balancing currents and voltages with self-regulating inductance is supplemented with a negative and positive sequence filter circuit, to which corresponding narrow-band resonant filters are connected, absorbing sets of negative and positive sequences formed by the emission of the corresponding higher harmonic components. Taken together, this makes it possible to create a universal balancing device for four-wire electrical networks.

EFFECT: reduced asymmetry of currents and voltages of the fundamental frequency and additional sets of higher harmonic components that form direct, negative and zero sequences.

1 cl, 1 dwg

Description

The invention relates to electrical engineering and can be used to compensate for negative and zero sequence currents caused by the fundamental frequency current, as well as additional direct, negative and zero sequences caused by higher harmonic components of currents in three-phase electrical networks when connecting to them a three-phase asymmetrical load of consumers with nonlinear current-voltage characteristic.

A filter-balancing device for three-phase networks with a neutral wire is known, containing a three-phase electromagnetic device, the windings of which are connected in a counter-zigzag pattern, having three phase wires and one neutral. In this case, the phase terminal is intended for connection to the phase wires, and the neutral one to the neutral wire. A filter balancing device for three-phase networks with a neutral wire is equipped with three capacitor banks, the terminals of each of which are connected respectively between the phase and neutral terminals of the electromagnetic device (Pat. SU No. 1206881 A, H02J 3/26, 01/23/1986) [1].

The disadvantage of this device is that the parameters of its inductance are unchanged, which does not allow the power of the device to be regulated when the power of the connected load changes.

The closest technical solution, chosen as a prototype, is a device for balancing currents and voltages with self-regulating inductance, containing suspended magnetic cores capable of changing their position under the influence of electromagnetic forces caused by changes in the asymmetrical load, automatically adjusting their power (Pat. RU No. 2796074 C1, H02J 3/26, 05/16/2023) [2].

The disadvantage of this device is the impossibility of balancing additional sets of higher harmonic components (HHC), forming positive, negative and zero sequences, as well as the inability to compensate for non-functional reactive power flows.

The objective of the invention is to create a universal balancing device for four-wire electrical networks.

The essence of the invention is as follows. A universal balancing device for four-wire electrical networks, containing an electromagnetic device for balancing currents and voltages with self-regulating inductance, containing a three-phase electromagnetic device with steel cores placed in coils installed on the base, the windings of the said device are connected in a counter zigzag pattern, having three phase terminals and one neutral, and each phase terminal is intended for connection to the phase wires of the network, and the neutral - to the neutral wire, in addition, each core is installed in a corresponding coil with the possibility of its axial movement, characterized in that it additionally contains negative and positive sequence current filters , consisting of current transformers and transreactors, to which narrow-band resonant filters (BRFs) are connected, absorbing sets of negative and positive sequences formed by the emission of the corresponding higher harmonic components, in addition, a bank of capacitors is connected to the phases of the electromagnetic device according to the “triangle” circuit. Taken together, this makes it possible to create a universal balancing device for four-wire electrical networks.

In fig. a universal balancing device for four-wire electrical networks is presented.

The universal balancing device for four-wire electrical networks consists of six blocks: block 1 - electromagnetic device (EMD), block 2 - capacitor bank, block 3 and 4 - negative and positive sequence filters, block 5 and 6 - URF blocks, respectively, negative and positive sequence sequences.

Block 1 - a device for balancing currents and voltages with self-regulating inductance, has three phase terminals A, B and C and one neutral N for connecting to a four-wire network and additional contacts “a, b, c, d, e, f” for connecting filters current of reverse (block 3) and direct (block 4) sequences.

Block 2 is a battery of capacitors C1, C2 and C3, which is connected to the phase terminals of the EMU A, B and C (block 1) according to the “triangle” circuit in order to reduce non-functional reactive power flows and the corresponding additional losses caused by these flows.

Blocks 3 and 4 are reverse (block 3) and forward (block 4) sequence current filters. The negative sequence current filter (block 3) has eight terminals: six terminals “a', b', c', d', d', f'" for connecting the EMU (block 1) and two terminals "P', 0'" for connecting negative sequence URF (block 5). The positive sequence current filter (block 4) also has eight terminals: six terminals “a'', b'', c'', d'', d'', e''” for connecting the EMU (block 1) and two terminals “P'', 0''” for connecting direct sequence URF (block 6). The filters consist of current transformers TLA and transreactors TAV, as well as variable resistance resistors R ₁ and R ₂ connected to the secondary windings of TAV and TLA, respectively.

Blocks 5 and 6 are narrow-band resonant filters assembled in parallel, each of which is tuned to resonate precisely its own component from the total VGS flow. Block 5 forms a set of URFs for negative sequence (1 ₍₂₎ , 1 ₍₅₎ , 1 ₍₈₎ , 1 _(j) - 1 ₍₃₈₎ ) and is connected to the negative sequence current filter to the terminals “P', 0'” (block 3). Block 6 forms a set of URFs for positive sequence (1 ₍₄₎ , 1 ₍₇₎ , 1 ₍₁₀₎ , 1 _(i) - 1 ₍₄₀₎ ) and is connected to the positive sequence current filter to the pins “P'', 0''" (block 4).

The operating principle of a universal balancing device for four-wire electrical networks is as follows. A device for balancing currents and voltages with self-regulating inductance (block 1) minimizes the zero-sequence currents of the fundamental frequency and the additional zero-sequence formed by the VGS, multiples of three. Filtering of additional direct and reverse sequences formed by the corresponding VGS currents is carried out by filters of the reverse (block 3) and direct (block 4) sequence currents. The principle of operation is to compare the voltage from the TLA current transformer and from the TAV transreactor. The primary windings of the TLA transformer (block 3) are connected to the current difference and the TAV transreactor for the difference The primary current of the current transformer TLA is in phase with the secondary current, therefore the voltage across R ₂ will be in phase with the primary current. The phase of the secondary current of the TAV transreactor depends on the secondary load. The resistance of resistors R ₁ and R ₂ is selected so that the voltage in phase with the current . Wherein will lead the current at an angle π/3. When positive sequence currents are applied to the filter, the voltage at the filter output will be equal to zero, since the voltage vectors And opposite in direction. If negative sequence currents are supplied to the filter input, then the voltage vectors will shift relative to each other by an angle π/3 and a significant voltage will appear at the filter output If the current transformer TLA (block 4) is switched on to the current difference and TAV transreactor for current difference then a positive sequence current filter will be obtained, which will direct positive sequence currents to the URF (block 6). In the URF (blocks 5 and 6), consisting of circuits of inductive-capacitive elements, each of which is tuned to resonance with the corresponding harmonic, additional reverse (block 5) and direct (block 6) sequences formed by the VGS are filtered.

Thus, a universal balancing device for four-wire electrical networks has been proposed, which allows reducing the asymmetry of currents and voltages of the fundamental frequency and additional sets of higher harmonic components that form direct, negative and zero sequences.

SOURCES OF INFORMATION TAKEN INTO ATTENTION

1. Patent SU No. 1206881 A, H02J 3/26, 01/23/1986.

2. Patent RU No. 2796074 C1, H02J 3/26, 05/16/2023 - prototype.

Claims (1)

A universal balancing device for four-wire electrical networks, containing an electromagnetic device for balancing currents and voltages with self-regulating inductance, containing a three-phase electromagnetic device with steel cores placed in coils installed on the base, the windings of the said device are connected according to a “counter zigzag” pattern, having three phase output and one neutral, each phase terminal is intended for connection to the phase wires of the network, and the neutral one to the neutral wire, in addition, each core is installed in a corresponding coil with the possibility of its axial movement, characterized in that it additionally contains reverse and reverse current filters positive sequences, consisting of current transformers and transreactors, to which narrow-band resonant filters are connected, absorbing sets of negative and positive sequences formed by the emission of the corresponding higher harmonic components; in addition, a bank of capacitors is connected to the phases of the electromagnetic device according to the “triangle” circuit.

Images