CZ2015672A3

CZ2015672A3 - Device to symmetrize load of three-phase electric network

Info

Publication number: CZ2015672A3
Application number: CZ2015-672A
Authority: CZ
Inventors: Miroslav Svoboda; Lubomír Slavík; Milan Kolář
Original assignee: Technická univerzita v Liberci
Priority date: 2015-09-30
Filing date: 2015-09-30
Publication date: 2016-07-07
Also published as: CZ306041B6

Abstract

Vynález se týká zařízení (1) k symetrizaci zatížení třífázové elektrické sítě (2) při nesymetrickém odběru elektrické energie do jednofázové, dvoufázové nebo třífázové sítě, jehož vstupy jsou připojeny k výstupním svorkám tří fází (L1, L2, L3) třífázové sítě (2), přičemž jeho výstupy jsou připojeny na fázové svorky (U, V, W) jednotlivých spotřebičů (3, 4, 5) odporového charakteru, s rozdílnými elektrickými příkony, přičemž toto zařízení obsahuje elektrické a/nebo elektronické prostředky, jimiž je alespoň jeden třífázový transformátor (100) nebo tři jednofázově transformátory (101, 102, 103). Vinutí (11, 12, 13) každého transformátoru (101, 102, 103) nebo každé fázové části třífázového transformátoru (100) obsahuje primární vinutí (111, 121, 131) s odbočkou (112, 122, 132) a dvě sekundární vinutí (113, 114, 123, 124, 133, 134).BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device (1) for symmetrizing the load of a three-phase electrical network (2) in an unsymmetrical power take-off to a single-phase, two-phase or three-phase network whose inputs are connected to the three-phase output terminals (L1, L2, L3) of a three-phase network the outputs of which are connected to phase terminals (U, V, W) of resistive consumers (3, 4, 5) with different electrical inputs, the device comprising electrical and / or electronic means, at least one three-phase transformer (100) or three single-phase transformers (101, 102, 103). The windings (11, 12, 13) of each transformer (101, 102, 103) or each phase portion of the three-phase transformer (100) include a primary winding (111, 121, 131) with a tap (112, 122, 132) and two secondary windings ( 113, 114, 123, 124, 133, 134).

Description

Equipment for symmetrizing the load of three-phase electrical site

Apparatus for symmetrizing the load of three-phase electrical network with unsymmetrical f) collecting electrical energy from individual phases of a three-phase network, the inputs of which are connected to three terminals of a three-phase network, with single-phase, two-phase or three-phase consumers of resistive nature connected to its output terminals, with different electrical power in each phase, the device comprising electrical and / or electronic means.

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Background Art

A number of devices are known to enable the removal of power from a three-phase network and its supply to a single-phase, two-phase or three-phase network. Often, such devices are used, for example, to power a single-phase overhead line from a three-phase grid, for example, to feed the overhead line. An example is the solution according to EP ί ^ 25θ | θ44 B1. In its symmetric connection, a three-phase DC link rectifier with its own line is used.

The power supply for single-phase traction lines in accordance with US 4 ^ 689735 A solves (f current consumption by means of special balancing circuits. US 5i109j327 A solves power supply by means of a three-phase network with AC-DC and DC-AC converters using capacitors or storage devices. is complex and used elements expensive.

These devices are mostly designed for a single purpose using different types of controllers, and their variability is small and the drawn power from all phases may not be sufficiently uniform. The object of the present invention is to enable symmetrized three-phase power supply to power single-phase, two-phase, or three-phase consumers of resistive nature. This solution should allow the take-off (combination of power from individual phases to almost full generator power, of course, with efficiency and Without a symmetrization device, only one third of the full power of the generator can be taken from one phase in theory, but usually only 10 to 15% of the full generator power is due to the considerable complications associated with the control of the excitation. the power of the generator, provided that the remaining phases are not loaded, so the device could be used especially for generators serving as back-up sources that supply en ergii to a three-phase network of a local building where both three-phase and single-phase or two-phase power consumers are installed (eg. thermal). Moreover, the device according to the invention also allows the connection of a symmetrical three-phase load of general nature (eg electric motors).

SUMMARY OF THE INVENTION The object of the invention is achieved in particular by suitable interconnection of the windings of three single-phase or one three-phase transformers. The addition is the connection of a combination of compensating capacitor batteries and chokes.

The essence of the device for symmetrizing the load of a three-phase electrical network in the unsymmetrical abstraction of electricity to a single-phase, two-phase or three-phase network that includes electrical and / or electronic means whose essence is that the electrical means is at least one three-phase transformer or three single-phase transformers wherein the windings of each transformer or each phase portion of the three-phase transformer comprise a primary winding with a tap and two secondary windings.

The end of the primary winding of the first transformer is connected to one terminal of the three-phase network, the end of the primary winding of the second transformer is connected to the third terminal of the three-phase network and the beginnings of the primary windings of the transformers are connected to the neutral. The primary winding of the first transformer is connected to the end of the first Mk of the second winding of the second transformer, the primary winding of the second transformer is connected to the end of the first secondary winding of the third transformer and the primary winding of the third transformer is connected to the end of the first secondary winding of the first transformer

The beginning of the first secondary winding of the first transformer is connected to the end of the second secondary winding of the second transformer, the beginning of the first secondary winding of the second transformer is connected to the end of the second secondary winding of the first transformer.

The start of the second secondary winding of the third transformer is applied to the input terminal of one consumer, the start of the second secondary winding / first transformer is applied to the input terminal of the second consumer and the beginning of the second secondary winding of the second transformer is applied to the input terminal of the third consumer, the second terminals of the appliances being connected to neutral. h (This arrangement achieves that even at different loads of the individual appliances the voltages at the terminals of all appliances are the same and the individual phases of the three-phase network are evenly loaded with active power. Output current measuring devices are included upstream of the consumer input terminals.

Secondly, the apparatus includes capacitor batteries and choke batteries which are connected via switches to the output of the switching circuit of the batteries, wherein the switches and the switching circuit are connected in parallel to the output of the logic unit which is preceded by a differential amplifier circuit connected to the current meter outputs of the individual appliances. ^ 5 Compensating with battery capacitors and chokes eliminates reactive currents in the secondary part that arise during this connection. This eliminates both the overload of the transformer windings and the three-phase power supply.

The apparatus further comprises a phase sequence for identifying the phase sequence whose inputs are connected to the individual phases of the three-phase network phase which are simultaneously connected in parallel to the relay input of the primary winding of the three-phase transformer, respectively. single-phase transformers. For the desired function of the device according to the invention, it is necessary to ensure a correct phase sequence. If not properly connected, the phase sequence identification circuit will not connect the device to the network.

The device further comprises a three-phase unbalance load indicator circuit that is connected between the neutral wires of the three-phase network and the individual consumers. In doing so, the output of the unbalance indicator circuit is connected via a switch to the primary winding disconnection relay input and / or to a fault signaling means. In the event of a zero-current equalization current being exceeded due to a device failure or exceeding the reactive power non-compen- sation, the indicator turns the primary winding off via the switch and the corresponding relay, and / or at least gives a fault signal.

Clarifying drawings

The device according to the invention is shown in the drawing, where in Fig. 1 is a block diagram of the whole load-symmetric device of the three-phase electric network, Fig. 2 is a detailed diagram of all transformer windings and Fig. 3 is a phasor diagram of the device operation. Examples of carrying out the invention

In the exemplary embodiment of the invention, the symmetrization device 1 is shown in the block diagram of FIG. 1, where the device 7 is connected between the output terminals of the three-phase network 2 and the input terminals of the individual appliances 3, 4, 5. The basic means of the symmetrization device 1 is a three-phase transformer 100 or three single phase transformers 101, 102, 103 with their respective winding connections. Detailed connection of all windings H, 12, 13 of the three-phase transformer 100, respectively. the three single-phase transformers 101, 102, 103 of the symmetrization device 1 are shown in FIG. 2, in which the beginnings of the individual windings are indicated by a dot outside the connecting lines.

The primary winding 111, 121, 131 of the transformers 100 and 100, respectively. 101, 102, 103 are connected to the phase terminals L1, L2, L3 of the three-phase network 2. The taps 112, 122, 132 of the primary windings 111, 121, 131 are connected so as to have the voltage Upi, Up2, UP3 at the voltage of zero against the neutral conductor N. one third of the phase voltage Uf at the input terminals of the load U, V, W to the individual loads 3, 4, 5.

Each transformer 100, resp. 101, 102, 103 further comprises two secondary windings 113, 114, 123, 124, 133, 134. Each of these secondary windings has a number of turns to have a voltage Usn, Usi2, Us2i, Us22, US3i, US32 of the two-thirds of the phase output voltage Uf of the phases connected to the input terminals U, V, W of the individual appliances 3, 4, 5. The primary winding branch 112, 122, 132 of each transformer 100 and 100 respectively. 101,102,103 is always connected to the end of the first secondary winding 123,133, 113 of the subsequent phase transformer. The start of this first secondary winding 113, 123, 133 is then coupled to the end of the second secondary winding 124, 134, 114 of the downstream transformer, and the start of this second secondary winding 114, 124, 134 is coupled to the input phase terminals V, W, U of each ^ The input phase terminals V, W, U of the individual consumers 4, 5, 3 are connected via a measuring device 62, 63, 61 to the output streams. Primary windings 111-121, 131 of transformers 100 and 100, respectively. 101, 102, 103 with taps 112, 122, 132 operate as autotransformers.

To compensate for the reactive power component, the pairs of terminals a1, b1; a2, b2; and a3, b3 of the first secondary windings 113, 123, 133 connected by compensating capacitors, and to pairs of terminals cl, d1; c2, d2; and c3, d3 of the second secondary winding 114, 124, 134, 134 of the compensating choke. When connecting the transformer windings, it is necessary to respect the correct phase sequence with respect to compensation. The outputs of the measuring devices 61, 62, 63 of the output currents are connected to the 64 differential amplifiers whose outputs control the A / D converters with the switching logic of the 65 circuit. the outputs of the secondary windings 113, 114, 123, 124, 133, 134 of the transformers 100 and 100, respectively. 101, 102, 103. Switching circuit 66 of batteries 686 of capacitors and batteries 69, 70 is controlled by the switching logic unit 65. Thus, the switching circuit 66 switches the secondary windings of the transformers 100 and 100, respectively, according to the reactive current magnitude evaluation via the circuits 64 and 65. 101, 102, 103 to respective switches 11, 72, 73 and 74. By means of switches 71, 72, 73 and 74, the secondary windings of the transformers 100 and 100 are respectively. 101, 102, 103 are connected to individual capacitors and / or chokes in batteries 67, 68 compensation capacitors and 69, 70 compensation chokes. y (In the exemplary embodiment, the primary windings of the transformers 100 are connected to the terminals of phases L1, L2, L3 of the three-phase network 2 via a relay 75 which disconnects the primary windings of the transformers 100-resP · 131 132, 103 from the three-phase network 2 in case of incorrect phase sequence, or When the correct phase sequence is indicated, the phase sequence indicator 76, which fails to connect the device to the three-phase network 2, is used to indicate the correct phase sequence. The load unbalance indicator 77 of the three-phase grid 2 monitors the permissible values of the equalizing current flow through the neutral. the device should be disconnected if the zero current conductor current limit is exceeded due to equipment failure or exceeded reactive power overcompensation, both indicators 76 and 77 are connected to switch 78 that controls rel 75.

If the phase of the three-phase network 2, i.e. the inputs to the symmetrization device 1 according to the invention, is denoted U, L2, L3 and the outputs of the device 1 according to the invention, to which the phase terminals U, V, W of the individual appliances 3, 4, 5 are connected , then the active power and power can be described as Pli = Pc2 = Pc3 = 1/3 (Pc + Pcv + Pcw), whereby the reactive power PjLi, PjL2, PjL3 can be minimized by compensation.

The principle of operation of the device according to the invention is evident from the phasor diagram in FIG. 101, 102, 103 in FIG. If the output phase voltage at all phase terminals U, V, W is equal to Uf 'yg and if it passes through the phase terminal U of the appliance 3 the current lu, the phase terminal V the appliances 4 current Iv and the phase terminal W of the appliance 5 current lw (assuming sampling active power), then the effective power of the size is taken from the terminal of the first input phase U (which is in phase with the phase terminal U of the appliance 3)

active power is taken from the L2 phase terminal (in phase W phase terminal V of appliance 4)

and active power is taken from the L3 phase terminal (in phase with phase terminal W of consumer 5)

, which means that the same active power is taken from all phase terminals L1, J2, L3

that is, all phases are loaded equally by one third of the total power consumed. The reactive power that loads the L1 phase has two components, inductive, of size ^

and capacitance size

. Phase L2 loads the reactive power of the inductive character

capacity

and the L3 phase reactive inductive power

capacity

These reactive power components need to be compensated by capacitors and $ chokes. Because each transformer 100, respectively. 101, IM-103 has two secondary windings, one of which is loaded with inductive current and the other with capacitive, partial self-compensation occurs, or with full output compensation for symmetrical output load. Therefore, only the reactive power of size must be compensated for the LI phase

, in L2 phase, reactive power is.

and at L3, reactive power of size

. If the resulting power for each phase is positive, it is necessary to compensate the reactive current in the first winding by a capacitor, otherwise in the second winding by a choke. As mentioned above and in Figure 1, only two batteries 67, 68 compensation capacitors and two batteries 69, 24 are sufficient for compensation. 70 compensating chokes, because there is no case where all three phases are only loaded with inductive or only by reactive power.

The number of compensating capacitors and compensating chokes in the batteries 67, 68 and 69, 70 can be minimized by connecting them in parallel. If the permissible value of uncompensated reactive power Pj is determined by the RC, the whole range of reactive power can be contained by sequentially connecting or switching capacitors and / or chokes by means of a binary A / D converter. If the capacitors in each battery have 67, 68 capacitance C and its binary multiples of% 2C, 4C etc., and the chokes in each battery of 69, 70 the inductance size L and its binary proportions L / 2, L / 4, etc. where the capacity C or inductance L compensates for the allowable value of the uncompensated reactive power Pj, then the number n of the capacitors and the chokes in one battery 67, 68, 69, 70 will cover the reactive power of the total PjCeik = Pj 2n.

The device according to the invention makes it possible to achieve very good symmetrization of the phase load of the three-phase mains when the resistive consumers with unequal input power is applied via a primary and secondary transformer winding system, up to a full three-phase mains power consumption by a single-phase consumer.

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List of Reference Symbols 1 Symmetric Device 100 Three-Phase Transformer 101 First Single-Phase Transformer 102 Second Single-Phase Transformer 103 Third Single Phase Winding Transformer 11 (Primary Transformer 100, 101) 111 Primary Winding (First Transformer 100, 101) 101) 113 first secondary winding (first transformer 100, 101) 114 second secondary winding (first transformer 100, 101) 12 winding (second transformer 100, 102) 121 primary winding (second transformer 100,102) 122 (primary winding of second transformer 100, 102) ^ 123 first secondary winding (second transformer 100, 102) 124 second secondary winding (second transformer 100, 102) 13 winding (third transformer 100,103) 131 primary winding (third transformer 100, 103) 132 tap (primary winding) third tran 100, 103) ^ 133 first secondary winding (third transformer 100, 103) 134 second secondary winding (third transformer 100,103) 2 three-phase generator

3 appliance connected to phase terminal U

4 appliance connected to phase terminal V

5 appliance connected to phase terminal W 61 output current measuring device (for appliance 3) 62 output current measuring device (for appliance 4) 63 output current measuring device (for appliance 5) 64 differential amplifier circuit 65 logic switching unit 66 capacitor switching circuit and chokes 67 capacitor battery 68 capacitor battery 69 choke battery 70 choke battery 71 switch 72 switch ^ 73 switch 74 switch 75 relay transformer primary winding 100 76 phase sequence identification circuit 77 generator load unbalance indicator 78 relay control switch (primary winding disconnection) transformers 100) L1 phase of three-phase generator L2 phase of three-phase generator L3 phase of three-phase generator U phase terminal of consumer 3 V phase terminal of consumer 4 W phase terminal of consumer 5

Claims

PATENT CLAIMS

1. Apparatus (1) for symmetrizing the load of a three-phase electrical network (2) in unsymmetrical power take-off to a single-phase, two-phase or three-phase network, the inputs of which are connected to three phases (L1, L2, L3) of a three-phase network (2), its the outputs are connected to the phase terminals (U, V, W) of each resistive consumer device (3, 4, 5) with different electrical inputs, the device comprising electrical and electronic means characterized by at least one three-phase transformer (100) or three single-phase transformers (101, 102, 103), wherein the windings (11, 12, 13) of each transformer (101, 102, 103) or each phase portion of the three-phase transformer (100) comprise a primary winding ( 111, 121, 131) with a branch (112, 122, 132) and two secondary windings (113, 114, 123, 124, 133, 134).

Device according to claim 1, characterized in that the end of the primary winding (111) of the first transformer (101) is connected to the output terminal of the phase (L1) of the three-phase network (2), the end of the primary winding (121) of the second transformer (102) being connected to the phase output terminal (L2) of the three-phase network (2). the end of the primary winding (131) of the third transformer (103) is connected to the output terminal of the phase (L3) of the three-phase network (2) and the beginning of the primary windings (111, 121, 131) of the transformers (101, 102, 103) is connected to the neutral ( N), wherein the branch (112) of the primary winding (111) of the first transformer (101) is connected to the end of the first secondary winding (123) of the second transformer (102), the branch (122) of the primary winding (121) of the second transformer (102) is connected at the end of the first secondary winding (133) of the third transformer (103) and the branch (132) of the primary winding (131) of the third transformer (103) is connected to the end of the first secondary winding (113) of the first transformer (101), wherein the beginning of the first secondary winding ( 113) of the first transformer (101) is connected to the end of the second secondary winding (124) of the second transformer (102), the beginning of the first secondary winding (123) of the second transformer (102). The transformer (102) is connected to the end of the second secondary winding (134) of the third transformer (103) and the beginning of the first secondary winding (133) of the third transformer (103) is connected to the end of the second secondary winding (114) of the first transformer (101), the beginning of the second secondary winding (134) of the third transformer (103) is applied to the phase terminal (U) of the consumer (3), the beginning of the second secondary winding (114) of the first transformer (101) is applied to the phase terminal (V) of the appliance (4) and the start of the second secondary winding (124) of the second transformer (102) is fed to the phase terminal (W) of the consumer (5), the second consumer terminals (3, 4, 5) being connected to the neutral (N).

Device according to claim 1 or 2, characterized in that the measuring devices (61, 62, 63) of the output streams are arranged upstream of the input phase terminals (U, V, W) of the consumers (3, 4, 5).

Apparatus according to any one of claims 1 to 3, characterized in that it comprises capacitor batteries (67, 68) and choke batteries (69, 70) connected to the switching output via switches (71, 72, 73, 74). the circuitry (66) of the batteries, the switches (71, 72, 73, 74) and the switching circuit (66) being connected in parallel to the output of the logic unit (65), the circuit 10 is upstream of the differential amplifier circuit (64) connected to the outputs of the measuring devices (61, 62, 63) current inputs to the individual appliances (4, 5, 6).

Device according to any one of claims 1 to 4, characterized in that it comprises a circuit (76) for identifying the phase sequence whose inputs are connected to the individual phase terminals (L1, L2, L3) of the three-phase network which are simultaneously connected to the the relay (75) input to disconnect the primary windings (111, 121, 131) of the three-phase transformer (100), respectively. single-phase transformers (101, 102, 103).

Device according to any one of claims 1 to 5, characterized in that it comprises a load unbalance indicator circuit (77) of a three-phase network (2) which is connected between the neutral wires (N) of the three-phase network (2) and the individual consumers (3, 4, 5), wherein the output of the unbalance indicator circuit (77) is connected via a switch (78) to the primary winding disconnection relay (75) input and / or the fault signaling means (75).