SU729749A1 - Device for balancing three-phase source output voltage - Google Patents

Description

sources of alternating current, in which, while maintaining a simple initial two-element scheme for incorporating reactive type balancing elements, the energy indices and the device balancing limits would be increased.

The goal is achieved in that the device for balancing the output voltage of a three-phase AC source, to which a three-phase asymmetrical load is connected, containing a common voltage regulator, two magnetic amplifiers, equipped with symmetry regulators and connected to a linear voltage network magnetic amplifier connected capacitor.

Fig. 1 is a circuit diagram of the proposed arrangement for providing symmetry; in fig. 2 adjustment characteristic of the loading element used; in fig. 3-5 are vector diagrams for different modes of operation.

FIG. The 1-three-phase AC voltage source 1 with output phases A, B, C has a common voltage regulator 2 connected by its input measuring device to the linear voltage AB and stabilizing the linear voltage of this phase with a high degree of accuracy at a given level Equivalent asymmetrical three-phase load 3, formed by a set of compensated single-phase and symmetrical three-phase loads of a known type, is powered by a three-phase voltage of source 1 and its component loads are grouped so that the greatest number of often included single-phase loads that also require high accuracy of the supply voltage, in addition to the same number of high-precision single-phase loads that also require high precision precisely to the reference phase AB, creating a deterministic single-phase asymmetry of the load 3 in the most likely and loaded mode of operation of the source power supply 1.

The two 15 symmetry controller 4, associated with its measuring input circuits with the linear voltages of all three phases of source 1, changes in accordance with the characteristic and asymmetry magnitude of these voltages, the magnitude of the control currents of the magnetic amplifiers, the output operating windings of which together with parallel-connected capacitors, they form two balancing loading elements, formed in parallel by an amplifier 5 and a capacitor 6, connected to a field voltage of A C-A vt B-C, unstabilized by a common regulator of 2 voltages,

In the absence of asymmetry of the TERMINATING linear voltages of source 1, the magnitude of the currents of the control windings of the magnetic amplifiers is selected in accordance with the explanatory adjustment characteristic (Fig. 2) per polo. wine from the nominal level in order to ensure the equality of capacitive and inductive conpoTiffi.ieHHH elements 5-6 with their transfer to the original mode of resonance, in which the equivalent resistance of each such parallel circuit is very large and is active. If the voltage of the source 1 is unbalanced, a corresponding increase in (or decrease) of the control current leads to a decrease (or increase) in the inductive resistance of the output working winding of the magnetic amplifier and a surge of inductive (or capacitive) current consumed by the element 5 1 of the 6.

Possible variants of the occurrence of asymmetry and the corresponding states of the reactive elements 5-6 of the proposed device for providing symmetry are also explained 5 by simplified replacement schemes and vector diagrams of currents and linear voltages presented in FIG. 3, 4, 5, where, for simplicity, only a single-phase part of an unbalanced load is shown 3. 0 Thus, in the most likely and loaded mode, when most single-phase loads are connected to the reference phase AB, stabilized by the action of a common regulator 2, 4 symmetry transfers element 5 to inductive mode of operation, and element 6 converts to capacitive mode with equal moduli of reactive currents, which is 1/3 of the current equivalent to an unbalanced load (Fig. 3). Realizable in this case, the symmetrization scheme corresponds to the well-known Shimetetm symmetristor scheme and provides a high value of the power factor (SoCh), i.e. increased energy indicators compared with the prototype. 5 When the same (less probable and unloaded) modes of operation of source 1 occur, when a single-phase equivalent asymmetrical load 3 appears in phase B – C (Fig. 4) or phase C – A (Fig. 5), Q balancing load elements 5-6 are simultaneously translated by the metric 4 in the same mode capacitive for the case shown in FIG. 4 f inductive - for the case in FIG. 5. The symmetry of linear currents and voltages of three-phase source 1 provided in these cases is accompanied, however, as in the prototype device, by decreasing the power factor to 0.5, which corresponds to the angle

a shift of 60 ° between the directions of the linear current and phase voltage vectors in the vector diagrams of FIG. 4-5. The deterioration of the energy performance of the proposed device in such less likely modes of operation of the symmetrical three-source source 1 is not significant, however, since there are loaded modes of its operation, when most of its single-phase loads that create asymmetry and normally connect to the reference phase AB, disabled.

The proposed device for providing symmetry (as opposed to the prototype device) works well also in cases of manifestation of two-phase asymmetry, when the active components of single-phase asymmetrical loads appear simultaneously on phases А-В and В-С or phases В-А and С-А supply source. Since these cases are intermediate in comparison with the boundary cases of single-phase asymmetry occurrence considered in FIG. 3, 4, 5, then the necessary parameters of elements 5 and 6 (automatically set in the real system by the symmetry controller 4) can be, for example, found by superposition (imposition) by reducing these two-phase asymmetry cases to two simultaneously existing cases single phase asymmetry, see FIG. 3-4 or 3-5. Only in one case of the manifestation of two-phase asymmetry (simultaneous at phases C – C and C – A) is the proposed device inoperative; however, this case is almost impossible with a given regular distribution of loads across the phases of the supply source, when most of its most frequently switched on and single-phase loads are connected to phase A – B, the line voltage of which is stabilized by the action of common regulator 2.

The positive technical and economic effect created by the invention is determined by increasing the energy indicators and extending the limits of the possibility of balancing the proposed device for providing symmetry.

Claims (1)

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