SU896723A1 - Statistic converter - Google Patents

Description

one

The invention relates to electrical engineering, in particular, to converters of alternating voltage of increased frequency into alternating voltage of lower frequency or continuously rectified with natural switching of controlled voltage gates in a wide range.

Static transducers are known that can be used to convert an alternating voltage to an alternating voltage of a lower frequency or to a constant voltage.

A frequency converter with direct coupling and an improved output voltage waveform is known. The improvement in shape is achieved not by changing the control angle S, but due to the fact that the secondary windings of the three-phase normal frequency transformer are made with an equal number of turns 1.

In such converters, the ratio of the frequency of the transmitting and receiving networks is constant, i.e. regulation-. Output voltage frequency is not possible.

Direct frequency converters are also known in which an approximation of the output voltage shape is achieved by changing the control angle oi. In this case, it is possible to regulate the frequency of the output voltage, as well as the magnitude of the output voltage in a wide range 2.

The disadvantages of such converters are low power factor, the presence of harmful harmonics, occur j. equalization currents (in direct frequency converters with joint control of groups). All this makes it necessary to increase the power, and hence the mass, of harmonic filters, devices for localizing and suppressing radio interference, leveling reactors, etc.

Methods of discrete transformation of the magnitude and form of the output voltage 3 and 4 are also known.

20

In particular, a method and a device for discrete conversion of alternating voltage is known, where the regulation of the output voltage in a wide range is realized without

25 of the distortion of the output voltage form (the angle of the whole control range is zero). Since the angle. oL is unchanged and zero, and only the amplitude of the sinusoidal voltage changes discretely, then in all

The control range has a power factor that remains consistently high and is independent of the mode of operation of the converter; there are no conditions for causing radio interference. These AC regulators can be used in conjunction with an auxiliary output converter to convert the frequency to -. You are 4.

The closest to the proposed is a static converter containing n converting ones made under one of the single-phase inverter circuits on keys with double-sided conductivity, and output tractors, the secondary windings of which are connected in series and form a summing circuit. The inputs of the inverter cells form the power input terminals of the converter, and the summing circuit is connected to the power input of the output of the conversion cell, which acts as a demodulator f 5 J.

The omission of a known converter is the increased mass and losses, as well as the deterioration of saepre-thic characteristics.

The purpose of the invention is to reduce the mass and losses, as well as to improve the energy characteristics of the converter.

The goal is achieved by a static converter that contains n per phase converter cells made along one of the single-phase inverter circuits on the keys with two-sided conductivity, their power inputs through the t-phase transformer connected to the supply network, and the outputs connected to the primary windings of the output transformers The secondary windings of which are connected in series and form a summing circuit connected to the input of the main output converter cell, m are summing connection circuits Inna star or triangle, to the common points of connection of these m summation circuits and to the inputs of the main output converter cell, made t-phase, one of the terminals of each phase made as m sections of the secondary winding of the supply transformer is connected additionally -phase output preparative cells, the number equal to the number of these sections, their MI1 inputs are connected to the terminals of at least one of the sections of the mentioned windings, and the secondary section of the t-phase transformer and summing the circuit in each of the m phases is connected in series.

In this case, the outputs of the additionally inputted t-phase output converter cells can be connected in parallel with the output of the main output converter cell.

In addition, the outputs of the additionally inputted t-phase output converter cells can be connected in series with the output of the main output converter cell.

Figures 1 and 2 depict single-phase to single-phase transducer circuits, two options; Fig. 3 are diagrams illustrating the formation of the output voltage form; 4 shows a three-phase single-phase converter circuit / FIG. 5 shows three-phase single-phase converter circuits whose secondary windings of a transformer (or generator windings) are made in the form of two sections; FIG. 6 shows a block of transformers in the converter shown in FIG. 5, FIG. 7 is a complete diagram of a converter cell; on Fig - diagram of a three-phase-single-phase converter, the secondary windings of the transformer which is made in the form of three sections; Figure 9 is the same as schema modification; 10 to 12 are converters, the outputs of the converter cells of which are connected in series, three options; Figures 13 and 14 are converters in which the phase voltage of the supply voltage is increased by combining two power supply systems; the variants in Figures 15 and 16 are a three-phase three-phase converter assembled from single-phase converters shown in Figure 9, a block diagram and timing diagrams removing the formation of his weekend

stress I

The static frequency converter (Fig. 1 consists of a block 1 of a transformer, converter cells 2-4, the outputs of which are connected to an alternating voltage network (supplying a t-phase transformer or an alternator), and the outputs to transformers 5-7, secondary windings of which are connected in series to form a summing circuit. Cells 2-4 are assembled on keys 8-19. One of the conclusions of the summing circuit is connected via keys 20 and 21 to the input terminals of the converter, and the other to one of the input terminals of the output converter Collected on the keys 22-25. Boc keys converter must -has bilateral conductivity.

The converter works as follows.

Since the transformer blocks 1 and cells 2-4 form a discrete action variable voltage regulator 4}, then using a control circuit fitted with a low-frequency sinusoidal voltage master oscillator, the smaller of the supply voltage frequency, at the input of the output converter cell ( keys 22-25 / a curve is formed from the cutoffs of sinusoids with an envelope close to the sinusoidal half-waves, and at the output close to a sinusoid. On these same elements a different static converter circuit can be assembled, in which sequence key key connection keys 20 and 21). Figure 2 shows the simplest single-phase converter containing a block of power transformers that are connected via bridge conversion cells 2-4 to the output terminals of the converter. The secondary windings of transformers 5-7 are connected in series with each other and with the primary power source. Transformer cells 2-4 are collected on keys 8-11, 12-15 and 16-19, respectively. The output of the primary power source is connected to the input of the main output converter cell (keys 20-23. Successively connected secondary windings of transformers are connected to the input of the output auxiliary cell on the keys 20, 21, 24, 25, the output of which is connected in parallel with the output of the main output converter cell on the keys 20-23 (keys 20 and 21 are common to both cells), the formation of the shape of the output voltage of the converter is explained using diagrams (Fig. 3). The shape of the output voltage is shown in Fig. 3 where Levels U. are also shown which can be realized at the output of a static converter. The levels can be realized, for example, by the known method 4. The levels that need to be realized at the output with a frequency proportional to the frequency of the mains supply are determined using the control scheme as follows. intervals 2R; / r, i, using cxeNM comparison, determine the instantaneous value of the input voltage and the nearest level proportional to this value of the input voltage. The required level can be determined graphically (Fig. 3a). Thus, at time t, the instantaneous value of the input signal is between the level BX.r (Fig. 3a). The number of levels measured at time t; j in code form is memorized and then realized with a delay t at the output of the transmitter at time IQ (Fig. 36) in the form of a half-wave voltage with the supply frequency and Q. amplitude proportional to the input signal half-wave supply voltage at the output of the converter. At the same time, the shape of these half-waves is unchanged, and their amplitude changes in accordance with the code signal so that the envelope of these half-waves after rectification is close to the shape of the input voltage (Fig. 3b). The accuracy of the half-wave amplitude is determined by the magnitude of the voltage quantization step by level. The amplitude deviation does not exceed half the quantization step. The output voltage is obtained as the algebraic sum of the voltages of the secondary windings of the transformers 5-7 and the primary power source. As an example, a combination of stresses .i .g is shown in FIG. 1 was put into operation, the source source was excluded for the interval t -t2 (Fig. 36). The output voltage at this interval is defined as the accumulation of these voltages (Fig. ZG). unlike the converter (Fig. 1), the converter (Fig. 2) does not contain keys connected in series with the secondary windings of the transformers and the power source, which allows reducing its mass and losses. To improve the harmonic composition of the output voltage in this case, the installation of a filter is required. The mass of the filter can be reduced by increasing the number of phases of the mains. Figure 4 shows a variant of a static converter made on the basis of a multiphase primary power source. Its device is similar to that described. A transformer unit is connected via a cell converter 2-4 to a primary power source (for example, transformer 26) connected in series with the windings of transformer unit 1 6. In this case, the transformer windings are connected to the input of the auxiliary cell 27, and the primary power source winding input converter cells 28. The outputs of the cells 27 and 28 are interconnected in parallel. In the converter (Fig. 5), the windings of the primary power source are divided into two sections. Such a converter consists of a transformer unit 1, the complete diagram of which is shown in fig.b, as well as converter cells 2-4, with which transformers are connected to the primary source 26. The complete diagram of such a converter cell is shown in Fig.7. The windings of the primary source are divided into two sections 29-31, 32-34 .. To the common connection points of section 35-37, the input of the auxiliary converter cell 38 is connected. The converter cell 27 is connected to the outermost primary source, and the cell 28 is connected to the output of unit 1 The outputs of cells 27, 28, and 38 are connected in parallel and work for a total load of 39. In this converter, as in the converter shown in Fig. 4, the harmonic composition of the output voltage is improved by increasing the phase voltage of the primary power supply, thereby causes reduced filter weight ;. In many cases, filters may not be available at all. In addition, in Converter C of FIG. 5, the mass reduction is achieved by breaking up the windings of a different source into equal sections. In this case, the mass of the trans-j block formators and the mass of the conversion cells 2-4 are reduced, although the source 26 mass increases. A static converter (fig. As a converter (fig. 57) contains a transformer unit 1, which in particular can be made similarly to a unit (fig. 67, and converter cells 2-4, which are filled similarly to cells (fig. 71) another scheme. The difference of this converter from the converter shown in Fig. 5 is that the windings of the primary source 26 are divided into three sections: 29-31, 32-34 and 40-42, respectively. Another one was introduced, except 27, 28, 38, converter cell 43. All sections are interconnected sequentially. However, they are sequentially connected to the secondary windings of the block 1 of transformers, but the conversion cells themselves are not made according to bridge, but according to zero schemes, and the outputs of cells 27, 28, 38 and 43 are connected in parallel. In all the converters (Figs.2, 4 , 5 and 8) when forming, as the instantaneous value increases, the output voltage from zero to the maximum value, all the levels that can be obtained at the output of transformer unit 1, obtained with the help of converter cells 2-4, are entered first. only that transform works the spacing cell, which is directly connected with the output of block 1 (clips X, Y), i.e. a converter 43 (FIG. 8) or a converter 28 (FIG. 5), etc. Then, the winding sections of the primary power source are inserted in order of increasing voltage. For example, in the converter (Fig. 8, sections 40-42 are first introduced, then sections 32-34, and finally sections 29-31. The static converter (Fig. 9), similarly to the converter (Fig. 8), contains a transformer unit 1 and converter cells, 2-4, the connections between which are simplified. The primary power source is also divided into three sections, but the phase windings 29-31 have a common connection point (connected by a star). In addition, additional taps are provided on the windings 29-31, 44-46 , 47-49 and 50-52 respectively. Zero t-phases are attached to these taps. converter cells 53-55. The same taps can be used to build a converter with a multi-phase output, the circuit of which is described below.Converting cell 56 is connected at the output of unit 1 using-clamps 57-59. The same clamps are connected to cells 53-55. Thus, in this case, the outputs of the cells 53-56 are connected in parallel to a common load 39 having a common connection point (terminal 60) with a zero output of the primary power source. In this converter, with increasing output voltage, levels are first obtained using cells 2–4 at the output of unit 1 while the cell 56 is working and cell 55 is turned on. (First stage of the primary source; the voltage of the first stage of the primary power source is summed with the output voltage of block 1, which changes discretely with the help of cells 2-4. With a further increase in the output voltage, the output cell 55 and the next step of the primary source is entered with the help of cell 54, etc. If the output voltage is large enough, in practice it is often advisable to connect the outputs of the converter cells not in parallel as in the converters (Fig.2, 4, 5, 8, 9), a. in series (Fig. 10-12). The converter (Fig.10 contains a transformer block 1 and transforming cells 2–4, which are made similarly to the considered transformers. The secondary windings of the primary source 26 are divided into three sections: 29–31, 32–34 and 40–42, respectively. The primary windings 61-63 of source 26 are connected to the inputs of cells 2-4, and the secondary to the outputs of cells 27, 28 and 38. The outputs of the block are connected to the inputs of cell 43. The difference is in the fact that the outputs of all these converter cells are not connected. in parallel, but in series. However, in this case, the load circuit levels with increasing output voltage are entered in the same sequence: first, the levels formed at the output of block 1 are entered with the help of cells 2–4 when the cell 43 is operating in the rectifier mode and the pass-through key pairs converting cells 27, 28 and 38 (the other two laras of through keys included in pairs of SKOEONnyh keys cells hoops sections 29-31, 32-34, respectively) .; with further uve

the output voltage is introduced, except for cell 43, cell 27, with the pairs of pass-through keys 28 and 38 turned on; then cell 38 is entered with cells 27 and 43 entered and a pair of pass-through keys of cell 28 turned on; and finally, a sequential cell 28 is input. As can be seen from the diagram, with the described algorithm of cells 27, 28 and 38, sections of the secondary windings of source 26 are connected between themselves and the transformer windings of unit 1 in series, and the output voltage is equal to the algebraic sum of the successively connected primary windings power supply and unit 1. Such converters can be recommended when converting high voltages and having several separate primary sources (for example, synchronous generators) about the number of sections. In order to reduce losses in cells 27, 28 and 38, they are executed either according to a simplified bridge circuit (the cathode and anode groups of successive cells are combined), as shown in Fig. 11, or the cells are executed according to zero schemes, input is additional keys 64-67 for shunting the cells and block 1 for excluding the corresponding cell from the EMF circuit (Fig. 12). Here, the secondary winding sections of the power supply 26 (Fig. 11) are introduced into the summing circuit as follows.

To enter three sections, switches 68-71 (linear voltage is introduced into the circuit), or switches 7275 f, linear voltage Ug (j) is introduced into the circuit, or keys 76-79 (linear voltage is introduced into the circuit) -. In order to enter two sections, include keys 68-70 and 79 (linear voltage idr is introduced into the circuit), keys 72-74 and 71 (linear voltage Ug is entered), keys 76-78 and 75 (UCA linear voltage is introduced ,) If it is necessary to enter a linear voltage of one section, then turn on the keys alternately. 68, 69, 78, 75 or keys 72, 73, 70 and 79 or keys 76, 77, 74, 71. In this case, the winding sections of source 26 and block 1 are included in the summing circuit also. sequentially. The same can be said about the converter in FIG. 12.

Figures 13 and 14 show variants in which the phase voltage of the supply voltage is increased by combining two power systems: one of the power systems is carried out by an input transformer, the primary winding of which is connected by a star, and the second by a triangle. The outputs of the converters, 2-4 (Figs. 13 and 14), connect the outputs of the two power systems (according to the star and triangle schemes) with the designation 2b and 26, which are connected to the common buses of the A, B network, C. Secondary windings divided into sections, connected in series with each other and the windings of the transformer unit 1, connected via converter cells 80-82 with the output of the first supply system 26 (star connection). Sections of the second system 26 according to the delta scheme are also connected in series with each other and with the windings of block 1, which is connected through cells 83-85 to the output of the second power supply network (three-way connection}. Since the outputs of cells 2-4 are connected parallel to the total load

I

5 39, the voltage input sequence in this case is no different from the previously described converter with parallel connection of output cells. The difference scheme in Fig.13

0 from the circuit in FIG. 14 consists only in the execution of cells 2-4. In the first case, the converter cells 2-4 are made in the form of two series-connected bridges, and in the second case, 5 in the form of parallel-connected bridges. The converters have been described above, in which the primary voltage system is made of a single-phase or multiphase system and the secondary voltage system obtained by the converter of the primary system is single-phase. A three-phase system of secondary voltages can be obtained by combining the three described single-phase converters into one three-phase.

5 As an example, FIG. 15 shows a three-phase system obtained from the three single-phase converters shown in FIG. 9, conventionally shown in FIG. 15 in the form of blocks 2-4.

0 Blocks 2-4 feed a three-phase load 86.

Converters with a multi-phase mains supply system make it possible to significantly approximate the shape of the output voltage to a sinusoidal one.

five

FIG. 16, thickened lines show the curves Uog,, Ugg of a three-phase system of output voltages with the ratio of the frequencies of primary and secondary voltages equal to three and

0 For consistency, the Ugg curve shows the envelope of UQg (,,. With an increase in the frequency and phase of the primary voltages, the output voltage form approaches sinusoidal and already at

5, the actual value of the output voltage differs little from the actual value of the first harmonic, remaining unchanged over the entire range of output voltage regulation.

Claims (5)

Compared to known converters, the proposed ones are not only different in the harmonic composition of the output voltage. With a sinusoidal control signal in the proposed transducers, it is possible to achieve a shift factor of one, while the theoretical value of the shift factor is 0.8436 in those who have found practical application of direct frequency transducers. The high values of the shift coefficient in the converters according to the proposed scheme are explained by the fact that the control angle during the formation of the shape of the output voltage remains unchanged and is equal to zero. The salient feature of the proposed converters is that when the number of phases of the output voltage is more than two, the loads of the phases exchange reactive power between themselves, without consuming the reactive energy from the network. The proposed transducer does not require the installation of compensating devices, whereas, as known in direct converters, it is required. The mass of the harmonics of the primary current and the output voltage, as well as the mass of devices for localizing and suppressing radio interference, are drastically reduced due to the absence of high rates of current buildup and voltage during the switching of the thyristors, the angle of regulation of which in the discrete method is zero. Since the harmonic composition of the output voltage with the discrete control method is better than with the phase, the external characteristics of the proposed converters are lower than with the phase control and will be somewhat tougher. When jointly controlling groups of output converter cells, the equalizing currents do not arise due to the equality of instantaneous voltage groups, therefore, the proposed converters do not require the installation of equalizing reactors, which allows not only to maintain good dynamic characteristics without resorting to an increase in the mass of the converter by equalizing reactors , but also to improve such indicators as speed, overshoot, linearity of characteristics. The proposed converters can work not only in the mode of frequency converters, but also in the mode of reversible and non-reversible rectifiers. Such converters, too, have higher rates: improved harmonic composition of input currents and output voltages, independence of the harmonic composition of the output voltage from the degree of output voltage regulation, increased power factor, etc. Claim 1. Static converter containing p per phase converter cells, made by one of the single-phase inverter circuits on the keys with two-sided conductivity, its power inputs through the t-phase transformer connected to the mains, and outputs connected to the primary output windings transformers, the secondary windings of which are connected in series and form a summing circuit, connected to the input of the main output converter cell, with the aim of improvement of energy and mass-dimensional indices, m summing circuits are connected by a star or a triangle, one of the conclusions of each phase made as a secondary section of the supply transformer is connected to the common points of the common output converter cell, made t-phase ,, additionally introduced t-phase output converter cells, the number equal to the number of specified sections, are connected to the terminals of at least one of the sections mentioned by their inputs utyh windings and the secondary windings t-phase transformer and the summing circuit in each of the m phases are connected in series. 2. The converter according to claim 1, characterized in that the outputs of the additionally inputted t-phase output converter cells are connected in parallel with the output of the main output converter cell. 3. The converter according to claim 1, wherein the outputs of the additionally inputted t-phase output converter cells are connected in series with the output of the main output converter cell. Sources of information taken into account during the examination 1. I. Kaganov. Electronic and Ion converters. M., L., GEP, 1956, p.455, Fig.5.50. 2.Zhemerov G.G. Directly coupled thyristor frequency converters. M., Energie, 1977. 3. USSR author's certificate for application No. 2556418/07, cl. Н02М 5/12, 12.19.77. 4. USSR author's certificate on application no. 2580023/07, cl. Н02М5 / 12, 12.19.78. 5. USSR author's certificate for application No. 2480779/07, cl. НММ 5/12, 08.28.78. 24 {. i / .l k 1 five Wow K7US; .25 27 28 Tj 38 3 03 4jXjVj2y 2A 7 FIG. 6 o ovs f i. 9 0 86 . 15