SU817919A1 - Transformer-thyristor direct frequency converter - Google Patents

Description

The invention relates to a power converter technology, namely, to a class of direct frequency converters, and can be used to power frequency controlled AC drives, when building stand-alone power plants with variable speed drive generator to obtain a stable frequency, and also to power various electromagnetic devices. working on the principle of a running floor, for example for powering linear motors or electromagnetic stirring installations x metals.

Known direct frequency converters, made by zero or bridge circuit l.

However, the strength part of them is relatively complex, since it contains a large number of controlled key elements. In addition, taking into account that, by virtue of its principle of operation, the converter provides the output voltage at the fundamental harmonic less than the output voltage in an overwhelming number of cases, installation of the input transformer of the matching transformer is required. For those slunai where the use of a matching transformer is unavoidable, it is worthwhile to use it appropriately not only for the purpose of matching, but also for other purposes, for example, to simplify the power part of the converter itself.

Direct frequency converters are also known, for which

0 is characteristic of the presence of a matching transformer with several sets of secondary three-phase windings loaded on three-phase valve bridges, at the outputs of the direct current which is installed. Fully controlled key elements. cops. When key elements of a thyristor converter are executed for locking them (since they cost

0 dc circuits) use forced switching units. In this case, as a rule, the windings of the throttles, which are an integral part of the switching unit, are included in series with the thyristors, and the rest of the switching unit can be made in various modifications of PI, G3,).

Closest to the proposed. is a converter containing a three-phase transformer with a primary winding connected to a three-phase mains supply, sets of secondary three-phase windings connected by an iB star and connected to the inputs of three-phase valve bridges, and the outputs of each of these bridges are loaded on key elements in the form of serially connected windings and thyristor, and the zero points of the sets of secondary windings of the transformer form the output terminals of the converter. The switching unit of this converter contains distribution and separation valves connecting the anodes and cathodes of the main thyristors with the output terminals of a single-phase thyristor bridge, c. the ac diagonal of which is installed is a switching capacitor, as well as chains of series-connected recharge valves and windings of the throttle connected in parallel with the key element fsj.

The disadvantages of the known converter include the comparative complexity of the power part, in particular, the fact that the number of sets of output windings is sufficiently large and equal (by the number of input phases involved in the formation of the output voltage) and reduced efficiency or degraded weight and size indicators from - due to imperfection of switching units.

The purpose of the invention is to simplify the converter and improve its efficiency.

The goal is achieved by the fact that frequency converters containing a t-phase transformer, the primary winding of which is connected to the t-phase power supply network, and sets of secondary t-phase windings connected in a star, are connected to the inputs of the t-phase valve bridges, and the outputs each of these bridges is loaded on the control key 1.me, one of the three output pins of each of the t-phase gate bridges is formed by the integration point of one of the input pins, and the remaining inputs of these bridges are connected to the opposite ontsam secondary t-phase windings of the transformer. In addition, when performing each of the controlled key elements in the form of serially connected windings of the commutator circuit and the main thyristor with a forced switching unit containing a switching capacitor, as well as controlled distribution valves, isolating valves, and a chain of successively connected recharge windings and valve, dividing valves are made controlled, the plates of the switching capacitor are connected to the main power lines Hur

through distribution and separation, controlled valves, with each of the capacitor plates connected to the cathodes of one half and the anodes of the other half of the main thyristors.

FIG. 1 shows the principle. Pial electric circuit of the proposed converter For case% 6; in fig. 2 - the same, block clocking / in FIG. 3.- modification of the switching unit for the case of a voltage-controlled converter; FIG. 4 is a circuit for replacing a converter in one of the switching intervals, explaining the principle of forming the output voltage; in fig. 5 - timing diagrams that show the operation of the converter.

The thyristor transformer direct frequency converter contains a t-phase transformer 1 with primary winding 2 and with secondary windings 3-14, a diode bridge 15-20 with control of key elements 21-26. At powers up to units of kVA B: nowadays it is advisable to use transistors as key elements, and at high powers, thyristors with switching blocks.

In the converter (Fig. 1a), each key element 51-26 is made in the form of serially connected main thyristors, for example, 27 and 28 and windings 29 and 30 switching throttle 31, all of which main windings are well magnetized to each other due to their corresponding winding and positioning on a common magnitopipe. In addition to the main windings of the inductance throttles, the switching device also includes a capacitor unit 32, including, in particular, capacitors 33 and 34 (for

simplification of the presentation, the main windings of the throttles and the thyristors, as well as the switching capacitors are indicated selectively in the minimum number necessary for explaining the operation of the converter). .

Along with its simplicity (the absence of additional valves), the first version of the switching unit (Fig. 1a) has degraded weight and size indicators due to the large number of switching capacitors. These shortcomings are devoid of the second version of the switching unit, (Fig. 1 b). It contains distribution thyristors 35-40, separation valves 41-46 and only one commutator capacitor 47 in the diagonal of an alternating current of a single-phase bridge on thyristors 48-51, and the output of this bridge is bridged by a chain of thyristor 52 and winding 53 of the drossel, intended for forced reset, and the capacitor 47.

The disadvantage of this unit is a slightly underestimated efficiency due to the increased number of valves connected in series in the switching circuits.

An exception to this disadvantage is, to a certain extent, the kOMmutation unit represented in FIG. 2. It contains distribution thyristors 35-40, but the isolation valves 41-46 are controllable switch capacitor 47 connected directly between the connection points of distribution and separation thyristors and shunted by two recharge chains from series-connected windings 54 and 55 chokes and thyristors 56 and 57. Compared with the second option, this switching unit contains a slightly larger number of thyristors, however, due to this structure of its construction, the total number of gates in it is less, and Efficiency is higher due to the lower number of the series-connected valves in the switching circuits. In both variants, the second and third blocks of the switching winding 53, 54 and 55 of the choke of the recharging chains are magnetically connected to the main windings of the chokes 31, and the number of turns of these non-diverging windings 53, 54 and 55 choose more turns of the main windings of the chokes 31 This makes it possible to limit the accumulation of energy in the switching capacitor 47 and to avoid increasing the installed power of the converter elements.

Typical for the second and third variants of the switching unit is the use of one switching capacitor instead of six (in the first option), which determines, on the one hand, the best weight and size parameters, and on the other hand, different areas of their application. The first variant of the switching unit is advisable to use at elevated, and the second and third - at lower switching frequencies (f | yy).

In - de cases, not only frequency control, but also voltage control is required. The ability to control the output voltage in this converter. provided by the introduction of an additional seventh diode bridge 58, loaded on the same controllable key element 59 in the form of, for example, a thyristor with a series-connected winding 60 of the switching throttle 31 (Fig. 3). The switching unit (Fig. 1a) is equipped with one more the switching capacitor connected to the output of the bridge 58, the power block (fig. 3) - two additional thyristors 61 and 62. In the latter case, the connection circuit of the distribution and separation thyristors is changed accordingly. In cases where the problem of limiting the accumulation of energy on a capacitor is solved in other ways, recharging the chain can be performed with one winding 63 located on a separate core.

The Converter operates as follows.

FIG. Figure 4 shows the wiring diagram for one of the points in time when one of the diode bridges is closed, for example, 15. When closing a controlled key element 21, voltage is applied to the load from a pair of jointly operating secondary windings 3 and 4 of transformer 1. At the considered the phase voltage

20

U3 - U sinuJ t;

U (aJ t-12o °).

Using the superposition method, it is easy to show that the voltage on the phases of the load in this case will be equal to: and

V -: jf-Sin (uLi, t-30 °);

 -sivi (u t-iso),

vg

Uvn

.- 51P. ()

where is the circular frequency

Cpr is the maximum value of the voltage on the secondary windings of the transformer 1.

As a result of the alternate, sequential connection of all sets of secondary windings during the load phase phases, the voltage shown in FIG. 5 b, the frequency of the main harmonic voltage is equal to

D® d is the switching frequency of controlled key elements.

The key switching algorithms of the Aldd converter are shown in FIG. 5 in.

The switching unit (Fig. 1 a) works in the following way.

Claims (2)

Suppose that the main thyristor 27 (key element 21) is open, and the remaining main thyristors (key elements 22-26) are closed. Then, on the capacitor 33, the voltage is practically absent, or rather, it is equal to the voltage drop on the chain of the main thyristor 27 connected in series and the winding 29 of the drossel. The main capacitors are charged by the voltage from the secondary windings 5 14 through the respective bridges 16 20, as a result of which these capacitors are charged with the field shown on the capacitor 34, i.e. with the plus on the right facing. When the signal to the control electrode of the thyristor 28 is delivered, the latter opens and the capacitor discharges along the chain 34 28-30-34. Under the action of the discharge current of the capacitor 34 in the winding 30 drossel induced EMF with polarity, shown in the diagram ,. Since all the windings of the throttles are magnetically connected, then in the winding 29 an emf of the same sign is induced, which leads to the locking of the thyristor 27 due to the application of a reverse voltage along it to the circuit 29-27-ЗЗт29. When a signal is applied to the control electrode of the thyristor of the key element 23, the process of locking the thyristor 28 is carried out in a similar way. The sequence of control signals supplied to the thyristors of the key elements 21–26 are of a program cyclical nature (see Fig. 5c). This leads to the alternate connection of sets of secondary windings to the load and to the formation on the latter of a quasi-sinusoidal voltage with a frequency J, depending on the frequency of the control signals. The switching unit (Fig. 1 b) operates as follows. To lock, for example, thyristor 27 with the polarity of the capacitor 47, shown without brackets, the thyristors 35, 48 and 49 are unlocked and the reverse polarity is applied to the lockable thyristor along the circuit 47-4 -35-27-41-49-47 . After that, the thyristors 34, 48, 49, and 52 are locked in a natural way due to the current flowing through them to O, After the time required to restore the locking properties of these thyristors, the capacitor 47 is recharged by turning on the thyristor 52 and after some time The unit is ready for locking the next oh main thyristor. Block cog / mutatsni. (Fig. 2) works as follows. With the polarity of the voltage on the capacitor shown without brackets, the thyristors 35 and 41 are unlocked for locking the thyristor 27. After holding the frame necessary for locking this thyristor, the recharge thyristor 56 and codedensor 47 are forcedly recharged through the winding 54 of the throttle 31. For lock the following of thyristor 28 turn on thyristors 36 and 42, and then after an appropriate delay thyristor 57. Then the process repeats. The voltage-controlled variant uses a switching unit (Fig. 3. The output voltage is controlled by introducing an adjustable pause between the switching of the main thyristors. The reactive load current closure during adjustment pauses is provided by switching on the thyristor 59 of the bridge 58. In this case the capacitor 47 with the polarity shown without brackets is locked by the main thyristors, and the thyristor 59 of the bridge 58 is locked by the voltage with the polarity shown with brackets by unlocking When using the proposed direct frequency converter for building autonomous power supply systems for moving objects made in the form of a synchronous generator and converter, the need for a three-phase transformer is eliminated, and the secondary windings of the transformer in this case are uncoupled core generator windings. Thus, the proposed converter, in comparison with the known, is characterized by the simplicity of its design due to by eliminating two three-phase secondary winding sets, and in thyristor execution it allows: to increase the efficiency due to a more rational construction of the switching unit. The proposed principle of simplifying the power section and the switching unit also extends to transformer-thyristor converters with any number. For example, with 3, the converter contains only three bridges (15, 17, and 19) without corresponding distribution and separation valves. In addition, variants of the forced switching units can be used in non-simplified (by the power part) transformer-thyristor type frequency converters. Claim 1. Transformer-thyristor direct frequency converter containing a t-phase transformer with sets of secondary t-phase windings connected in a star, t-phase valve bridges, the outputs of each of which are loaded on controlled key elements, and the inputs are connected to the secondary t -phase windings of different phases of different sets of m-phase transformer, and the zero points of the sets of secondary windings form the output terminals of the transformer, which, in order to simplify, dyn and From the three output pins of the converter, it is formed by the merging point of ОДН9ГО of the input pins of each of the mentioned t-phase valve bridges, and the remaining inputs of these bridges are connected to the opposite ends of the secondary t-phase windings of the transformer. 2. The converter according to claim 1, each of the key elements of which is made in the form of series-connected windings of the switching dumps and the main thyristor with a forced switching unit containing a switching capacitor, lightweight distribution valves, dividing valves and a chain of series-connected rechargeable the valve and the windings of the inductance throttles, the separation and recharge throttles and valves, and the fact that the separation valves are controllable, the plates of mutating congameI I I 1 1 «1 -Ur l a) l | 1-jHb- I LCUI, 1 -T byJI y, I Kff jf "yg" ywg of the capacitor are connected to the power terminals of the main thyristors through distribution and controlled control valves, each having one half of the capacitor plates and the other half of the main thyristors. Sources of information taken into account in the examination 1. The author's certificate of the USSR W 133950, cl. H 02 M 5/30, 1960. 2. Electrical Engineering, 10, 1966. 3. Switzerland Patent No. 476419 Cl. - H 02 R 7/62, H 02 R, 13/30, 1969. 4. Japan Patent 48-31408 , cl. 56 В 3, .1973.х 5. US patent number 3435321, cl. 321-7 1969. 6.СВ. Modern tasks of converting equipment, vol. 2. Kiev, Institute of Electrodynamics, Academy of Sciences of the Ukrainian SSR, 1975, p. 132-140. L1 K CI -iTTi "Y" Y "i I i. il, I I .. i rW «« M tWl 1 1 with I-M t 1 I «v I I 1 M t F LJr4 LJMLf L f i t IG w