Voltage balancer in three-phase network
SUBSTANCE: invention relates to the electrical engineering. The device is intended for improvement of electric energy quality in regard to unbalance level in power networks with voltage of 0.4kV. It eliminates voltage unbalance due to vector subtraction of zero-phase-sequence voltage from voltage for all the three phases; to this end each of three groups of in-series secondary windings of step-down single-phase four-winding transformers with transformer ration equal to three is connected in series to wire of the respective phase so that voltage added to the line is subtracted by geometric vectors from voltage of the respective phases. The device is connected to the line break; it may be used for improvement of electric energy quality both for individual devices and their groups in regard to unbalance level. The balancer consists of three step-down single-phase four-winding transformers (1) with one primary (2) and three secondary (3) windings, input terminals (4), output terminals (5).
EFFECT: simplification of design, improvement of reliability and efficiency.
The invention relates to electrical engineering and can be used in electric networks with voltage of 0.4 kV.
The purpose of the device: the improvement of power quality by the level of voltage unbalance in accordance with GOST 13109-97, especially in rural power grids, where the quality of electricity on the level of asymmetry is often unsatisfactory, due to the applications in these networks transformers with winding connection star - star with a zero, the presence of a large fraction of single-phase loads and the length of lines in excess of 500 meters.
A device for control and voltage balancing in three-phase network with neutral conductor, in which the purpose of expanding the functionality of filtering harmonic currents additionally contains two groups of capacitors, each of which had three of the capacitor, and the first terminals of the capacitors in the first and second groups respectively connected together, the second terminals of the capacitors of the first group are connected respectively to the junction points Polubotok primary winding in each phase, the second terminals of the capacitors of the second group connected to the input of the phase terminals of the device (prototype - patent 1746466, 5 H02J 3/26, 09.07.1990).
The main disadvantage of this invention is the presence of three-phase switching� devices and other elements in addition to inductive, complicating the design of the device, reduce the reliability and do not provide, however, a complete removal of voltage unbalance.
The task of the invention is to provide a technically simple, reliable and effective device for balancing voltages of three-phase network with a range fixed asymmetry value to 100% and without the use of a three-phase switching devices and any additional elements, except induction.
The required technical result is achieved by using a device only booster transformers connected in a special way therein for receiving components of the zero sequence voltage and connected to input and output terminals of the device so that happened geometric subtraction of the obtained zero sequence components of the voltages of all three phases for the purpose of obtaining a symmetrical system of voltages.
Summary of the invention
The invention consists in the allocation of voltage zero-sequence and geometric subtract this voltage from the voltages of all three phases to obtain a symmetric system. The proposed method is based on the method of symmetrical components. The selection of voltage zero-sequence by geo�etnicheskogo addition a reduced three times voltages of the three phases. If the system is symmetric, that is, the voltage unbalance is present, the zero sequence voltage is equal zero and the geometric subtraction of it from the voltages of the three phases unchanged. If the system voltages of the three phases are unbalanced, the selected zero sequence voltage is not zero and the geometric subtraction of it from the voltages of the three phases is obtained symmetric system direct sequence. A reduced three times the voltage of the three phases form a three-phase step-down four winding transformer with one primary and three secondary windings with a transformation ratio equal to three. The primary windings are connected in star connection and connected to the phase voltage, however, is calculated for a voltage of 380 volts, as the possibility of eliminating the unbalance value to 100%. Geometric addition is obtained on the secondary windings of the voltage is performed by means of a serial connection of these secondary windings is obtained three groups of series-connected windings, which stands out on the zero sequence voltage. Geometric subtraction of the zero sequence voltage from the voltages of the three phases shall be implemented by consecutive inclusion in wire Tr�x phase obtained groups of series-connected windings, to ensure that the selected zero sequence voltage in the opposite phase to the voltage zero-sequence, present in the voltage of the corresponding phase. In contrast to the prior art, the present invention provides for the elimination of the unbalance value to 100% and correction voltages of the phases is carried out geometric subtraction of them selected voltage zero-sequence, which provides high efficiency and reliability of the device.
Fig.1 shows a circuit diagram of the device for balancing the voltages of the three-phase network. The device consists of three United in a special way-down-phase four winding transformer (1) having one primary (2) and three secondary windings (3). Terminals (4) are for connecting the device to a three-phase network, and the terminals (5) - for connection of consumers, the quality of electricity on the level of unbalance at the input which is necessary to maintain the proper level in accordance with GOST 13109-97.
The principle of operation of the device
The device of the balancing of tension is inserted in the opening lines that feed a three-phase load or a group of three-phase loads. The elimination of voltage unbalance occurs due to the geometric subtraction of the selected voltage zero posledovatelnostei voltages of all three phases. For this purpose, three groups of series-connected secondary windings of three single-phase step-down four winding transformers with a transformation ratio equal to three, sequentially each wire in the corresponding phase so that happened geometric subtraction allocated to groups of these series-connected secondary windings of the zero sequence voltage from the voltages of the respective phases, and the data of the primary winding of the transformers are connected in star connection and connected to the phase voltage.
The balancing device voltage three-phase network, characterized in that it contains switching devices and other elements, in addition to inductive, and compensates for the unbalance voltages up to 100% due to the geometric subtraction of the selected zero sequence voltage from the voltages of all three phases, for which three groups of series-connected secondary windings of three single-phase step-down four winding transformers with a transformation ratio equal to three, sequentially each wire in the corresponding phase so that happened geometric subtraction allocated to groups of these series-connected secondary windings of the voltage zero-sequence voltage applied to�testwuide phases and data of the primary winding of the transformers are connected in star connection and connected to the phase voltage.
SUBSTANCE: device comprises network terminals, three fast-operate fast-release voltage relays with closing and opening contacts, seven repeater relays per a phase with closing and opening contacts, three phase-recovering capacitors, three phase-shifting chokes, three phase-compensating capacitors, terminals for the connection of a three-phase load and a power supply source. The voltage relays are coupled to phase voltage of the respective phases in the network, the phase-recovering capacitors are coupled to linear voltage, at that each of the capacitors is connected in series to an opening contact of the repeater relay of the respective phase, each of the phase-shifting chokes is shunted by the closing contacts of the first and second repeater relays of the respective phase and by the in-series closing contacts of the third and fourth repeater relays of the respective phase, the repeater relays are connected to the negative output of the power supply source directly and to the positive output through the closing contacts of the voltage relay respectively. Each phase-compensating capacitor is shunted by the closing contacts of the fifth and sixth repeated relay of the respective phase and the phase-shifting capacitor of each phase is coupled between the same phase of the network and the phase next to the retarding phase through the opening contact of the seventh repeated relay of the respective phase.
EFFECT: faster operation and bigger power of the device.
1 tbl, 1 dwg
SUBSTANCE: in the method which assumes switch-over, at least, of part of single-phase loads to the least loaded phase for each switched-over single-phase load in the place of its connection to the line the values of active power corresponding to each phase voltage and current of zero wire of the line without considering the current of single-phase load are determined, and as the least loaded phase the line phase with the maximum value of the absolute value of active power is accepted the sign of which is opposite to the sign of active power of the most loaded phase. The device implementing the method contains the switching unit (1), four inputs (7, 8, 9 and 10) which are inputs of the device and are used for connection to phase wires F1, F2, F3 and zero wires N of the line, and two outputs (11) and (12) of the switching unit are used as the device outputs and are intended for connection of the single-phase load. The device also contains the current sensor (3) connected to zero wire N of the current line, and the first (4), the second (5) and the third (6) phase voltage sensors connected to device inputs, and also the unit 2 for determination of the least loaded phase the output bus (20) of which is connected to the control input of the switching unit 1. The unit (2) for determination of the least loaded phase contains the multichannel analogue-digital converter (17) connected to the input (19) unit (18) of digital signal processing. Inputs of the multichannel analogue-digital converter (17) are connected to the first (13), to the second (14), to the third (15) and to the fourth to inputs of the unit (2) of determination of the least loaded phase the output bus (20) of which is the output of the unit (18) of digital signal processing.
EFFECT: decrease of disbalance level at which the balancing of phase currents is performed, simplification of implementation and improvement of operational reliability.
5 cl, 2 dwg
SUBSTANCE: invention is used in electrical engineering. The method consists in following stages: formation of the component of the positive phase sequence system, intended for power supply, formation of the component of the negative phase sequence system, intended for power supply, superposition of the component of the positive phase sequence system and the component of the negative phase sequence system with obtaining of supply current, and supply of such composite current into a three-phase mains.
EFFECT: decrease of non-symmetry in three-phase mains.
12 cl, 5 dwg
SUBSTANCE: invention is used in electrical engineering. The device represents an earthing bipole - a tracking width-modulated voltage converter (a tracking PWM converter) attaching the neutral of the network feeding transformer to earth and forming lagging current for compensation of leading capacitance current of single-phase fault to earth, as well as a neutral current sensor, a network voltage transformer, a clock signal generator for measurement of network capacity and a calculation unit for determination of the required admittance of the above bipole. In addition to a common set of functional units, the tracking PWM converter is equipped with a current setting unit, the inputs of which are represented by neutral voltage and the required admittance, and the output of which is represented by current demand supplied to the current control input of the tracking PWM converter, and transfer function of the current setting device provides for lagging phase shift of about 90 degrees on network frequency.
EFFECT: improving quick action and enlarging functional capabilities.
9 cl, 46 dwg
SUBSTANCE: invention relates to electric engineering. The invention claims a three-phase balancing device where a three-phase three-leg transformer contains windings connected in an opposite staggered way. Free leads of the first windings are connected to output terminals and free leads of the second windings are connected into a common zero point to couple phase loads. In each phase there is one or two in-series voltage adding windings coupled through a two- or three-position switch in sequence with load at the side of the supply mains.
EFFECT: provision of the phase voltage balancing.
SUBSTANCE: control method for shunting of power supply units includes the following steps: measurement of the first three-phase output eclectic signal; calculation of the first direct and reverse sequences of the first three-phase output eclectic signal; generating of the preset components for direct and reverse sequences of phases in order to perform automatic compensation for the components of the first direct and reverse sequences thus outputting components of the second direct and reverse sequences; summing-up of the second direct and reverse sequences and output of the second three-phase output eclectic signal in the preset mode.
EFFECT: reducing output voltage ripple.
10 cl, 10 dwg
SUBSTANCE: invention is related to the field of electric engineering and power electronics and can be used for manufacturing of HV three-phase alternating current generating systems for aircraft. The suggested three-phase alternating current generating system with voltage inverter contains a three-phase synchronous generator, a static electric energy transducer based on a three-phase bridge rectifier which inputs are connected to outputs of the synchronous generator, two filter capacitors in the direct current link connected in-series and switched on in parallel to the output terminals of the rectifier and a three-phase bridge voltage inverter which inputs are connected to the rectifier outputs and outputs are connected to inputs of three low-frequency LC filters; a neutral load wire of the generation system is connected to the average point of filter capacitors in the direct current link; an inductance coil is connected by its one output to the neutral load wire of the generation system and by its other output to the neutral wire of the stator three-phase winding of the synchronous generator.
EFFECT: reducing electric losses in elements and improving efficiency ratio of the system as a whole.
SUBSTANCE: voltage stabiliser for a power supply system, which stabilises load of active power, comprises the first AC-DC and DC-AC converter to convert between AC power and DC power; and a nickel-metal-hydride battery located between and connected to a high-voltage cable at the DC side of the first AC-DC and DC-AC converter and a low-voltage cable at the DC side of the first AC-DC and DC-AC converter.
EFFECT: reduced mass and dimension parameters of a device.
10 cl, 17 dwg
SUBSTANCE: balancer is purposed to improve quality of current and voltage balancing in three-phase networks with neutral wire due to self-adjustment of power in case of current change in the neutral wire. The device contains additionally two power stages and automatic control circuit operating as current function of the neutral wire.
EFFECT: improving quality of adjustment due to detuning parameters of the suggested device from current unbalance in the network of 0,38 kV present at the moment.
FIELD: electrical engineering.
SUBSTANCE: power supply device (100) for immediate electric heating of a pipeline system contains basically a three-phase transformer (2), a symmetrisation unit (14), a compensation unit (22). The three-phase transformer (2) is adapted for supporting a single-phase load connected between the first phase (6) and the second phase (8) of the transformer (2). The transformer (2) contains at least one first tap switch (10) on the high-voltage side (12) of the transformer (2). The symmetrisation unit (14) contains the first capacitor means (16) connected between the first phase (6) and the third phase (18) of the transformer and an inductor means (20) connected between the second phase (8) and the third phase (18) of the said transformer (2). The compensation unit (22) contains the second capacitor means (24) connected between the first phase (6) and the second phase (8) of the transformer (2). The first tap switch (10), the first capacitor means (16), the second capacitor means (24) and/or the inductor means (20) are adapted for variation under load.
EFFECT: changing the value of capacity and inductivity of the corresponding capacitive and inductive means under load and optimisation under load on a real time basis.
7 cl, 4 dwg
FIELD: electrical and power engineering.
SUBSTANCE: proposed method intended for measuring current and voltage unbalance level and organizing on-line impact on them in three-phase power systems characterized in low quality of their power characteristics includes measurement of unbalance level with respect to reverse and zero sequence of both line and phase voltages and currents at frequency of each harmonic component. Frequency at which unbalance in analyzed characteristics occurs is found. Results obtained are used to generate control signal by correcting devices.
EFFECT: facilitated procedure.
1 cl, 5 dwg
FIELD: power engineering.
SUBSTANCE: method allows to fully utilize power of traction transformer due to loading its free phase by rectifiers and inverters, one of which is lead by leading phase of contact network, and second one of late phase, which allows to transfer electric energy to contact network, to exclude idling mode, to provide for lower asymmetry on reverse series in power grid 220 (110) kV, and also decreases level of higher harmonics.
EFFECT: higher efficiency, lowered values of quality coefficients of electric energy - asymmetry coefficient of reverse series and values of higher harmonics.
FIELD: electrical engineering.
SUBSTANCE: proposed method intended to enhance power quality characteristics for users subject to negative influence of higher harmonic components includes generation of circuit current higher harmonic components which are in phase opposition to higher harmonics of supply mains using electrical energy of independent power supply.
EFFECT: enhanced electrical energy quality characteristics for power consumers.
1 cl, 3 dwg
FIELD: electrical engineering.
SUBSTANCE: proposed method used to enhance quality characteristics of electrical energy supplied to users susceptible to impact of negative factors of electrical-energy higher harmonic components includes generation of higher harmonic components of current in network which are acting in phase opposition relative to higher harmonics of supply mains.
EFFECT: enhanced quality characteristics of electrical energy supplied to users.
1 cl, 3 dwg
FIELD: electric engineering, possible use in power circuits of various equipment.
SUBSTANCE: three-phased balancing device contains input and output clamps of powering networks. To output clamps, three-phased transformer is connected, primary windings of which are oppositely coupled in a zigzag. In accordance to the invention, between input and output clamps of powering network, first three-phased automatic switch is coupled, having an independent release. Serially with primary windings of three-phased transformer, second three-phased automatic switch is coupled. As zero contact for connection of phase loads, zero contact of primary windings of three-phased transformer, coupled oppositely in a zigzag, is used. Control block is connected serially to independent release, coupled between output clamp of one of the phases and zero contact of powering network, and ensures supply of voltage to independent release and activation of first automatic switch on disabling of second automatic switch.
EFFECT: increased reliability when powered from three-conductor or four-conductor powering network.
FIELD: electric engineering, possible use for powering various equipment.
SUBSTANCE: the balancing three-phased to one-phased transformer of alternating voltage contains input and output contacts, to which a transformer is connected which has primary windings in all three phases and two secondary windings in phases A and C. Primary windings are connected in a "zigzag". Windings of phases A and B, B and C, and also C and A are connected respectively. Secondary windings in phases A and C are coupled oppositely and are connected to output contacts.
EFFECT: reduction of stabilized power and asymmetry of primary currents and voltages.
FIELD: power production.
SUBSTANCE: when non-sinusoidal shape of supply voltage is decreased, electric power is distributed between electronic devices distorting the shape of supply voltage and electronic devices improving the shape of supply voltage during the semi-wave of supply voltage. Device is connected in parallel with consumers introducing distortions of voltage shape. Main voltage is supplied to the device input. Device includes serial connection of phase-shifting chain, control pulse shaper, dc power supply and power switcher, which connects consumers improving the shape of supply voltage to the mains at a certain period of time.
EFFECT: improvement of supply voltage shape and simplification of device design.
2 cl, 4 dwg
SUBSTANCE: invention concerns current power transmission equipment, particularly high-voltage power transmission. Device includes reactive shunts connected by reactive switches to line, with additional special reactive shunts connected to the line in star network pattern with unearthed neutral conductor.
EFFECT: enhanced shunt compensation of power transmission line in low load mode, stability and reliability in elimination of single-phase short circuits at single-phase reclosing.
FIELD: electrical engineering.
SUBSTANCE: invention relates to electrical engineering and may be used for hardware designing to improve quality and reduce voltage and electric power losses, when such power is transmitted in three-phase four-wire electric networks due to reduction of anharmonicity and asymmetry. Protection device generates 150 Hz frequency current from phase currents. This current is immediately introduced to harmonics 3 current of neutral working wire in opposite phase.
EFFECT: compensating highest current harmonics flowing along neutral conductor.
2 cl, 2 dwg
FIELD: electrical engineering.
SUBSTANCE: invention relates to electrical engineering, and can be used for phase-to-phase distribution of current in magnetically unstable three-phase signals, for example for neutralisation of zero-sequence harmful effects on current feed circuit in three-phase AC-to-DC and DC-to-AC voltage transformers. Proposed device comprises the transformer with its two phase windings connected, each by one output terminal, to zero input terminal, while their other output terminal is connected to appropriate phase input terminal. The transformer comprises two magnetic cores with phase windings connected in series and furnished with central tap. The said windings have their central and extreme free terminals connected to zero and common phase input terminals, respectively. Note here that central output terminal divides the number of turns in each phase windings into unequal parts, smaller ones being connected to opposing phase input terminals.
EFFECT: possibility to use two single-phase transformers with various-shape magnetic cores instead of three-phase transformer.