Voltage balancer in three-phase network

FIELD: electricity.

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.

1 dwg

 

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.



 

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