SU1086546A1 - Method for converting d-c voltage into quazisinusoidal voltage - Google Patents

Abstract

A METHOD FOR CONVERSION OF CONSTANT VOLTAGE TO QUASISINUSIDOIDAL, which consists in converting a constant voltage into a multi-phase alternating frequency wave arrays, increasing the frequency arcs, transforming it into a voltage of a predetermined frequency, by cyclic connection of frequency arrests with frequency arcs, transforming it, and transforming it into a voltage of a predetermined frequency, by looping the frequency patterns with frequency gains, with the frequency gains, by transforming it into the voltage of a given frequency, by cyclically connecting the frequency patterns with frequency gain signals, by transforming it into the voltage of a given frequency, by cyclic connection of frequency patterns with frequency gains, with the frequency amplifiers; A converter with two-conductor keys, which is characterized in that, with the aim of improving the quality of the converted electricity and expanding domain application, on the secondary side transformator- Iogo forschruyut symmetrical node (A it four system voltages having in each half-cycle pause duration 90 e. degree.

Description

"

eo a: ate

four

The invention relates to converter technology and can be used in power supply and electric drive systems for producing alternating voltage, quasi-sinusoidal shape with improved power quality. A known method of converting a DC voltage to an AC is converting a DC voltage into a single-phase AC voltage of the lower frequency, transforming it and converting it to an AC voltage of a given frequency using a direct frequency converter performed on the keys with two-way conductivity l. The disadvantage of this solution is the low quality of the output voltage curve due to the large one. ripple amplitudes. The closest to the technical essence of the present invention is a method of conversion, which consists in converting a constant voltage into a multi-phase (for example, three-phase) voltage of a higher frequency, transforming it and transforming it into an alternating voltage of a given frequency with two-way keys. make it easy 2. An increase in the number of carrier phases leads to an increase in the frequency of the ripple in the output voltage curve, however, the oc os disadvantage — the large ripple amplitude is conserved. In addition, the scope of application of the prototype is limited, since the implementation of the method is possible only on fully controlled keys. G. The purpose of the invention is to improve the quality of power conversion and expand the scope of use. The goal is achieved by converting a constant voltage to quasi-sinusoidal, which involves converting a constant voltage to a multiphase alternating voltage of high frequency, transforming it and transforming it into voltage. a given frequency by cyclically connecting each of the phases of the high-frequency voltage to the output terminals of the converter using two-way keys sided conductivity on the secondary side of the transformer assembly formed it four symmetrical voltage system, having in each half-cycle pause duration 90 el.grad. FIG. Figure 1 shows diagrams explaining the voltage produced by a known method; Fig. 2 the same, according to the proposed method; on . 3 is an example of the implementation scheme of the proposed method; in fig. 4 - diagrams of the converter operation (e.) And the block diagram of the control channel (6). According to FIG. 1, portions of the low frequency UH voltage curve at various control angles are obtained at the output of the direct converter when it is powered with a square corner U ttecytteK. The presence of inductance in the load circuit leads to the appearance in the curve of the output voltage of pulses of opposite polarity in the sections, corresponding to the shift time of unlocking the next converter key relative to the beginning of the carrier half period, which determines the large amplitude of the pulsations. An increase in the number of carrier phases does not lead to a decrease in the amplitude of the pulsations. The FIG. 2 plots of the voltage curve and q at different control angles are obtained by feeding the direct carrier converter formed by the proposed method. As can be seen, the carrier is formed in the form of a symmetrical four-phase system of voltages (voltages shifted by 180 degrees electr. Relative to those shown, not shown) shifted among themselves by 90 degrees electr. and imekntsih in each half-pause duration of 90 e. hail. This ensures, in the entire range of control angles, the appearance of pauses in the output curve instead of pulses of opposite polarity, which halves the amplitude of the pulsations, i.e. improving the quality of the output curve. The circuit (fig. 3) includes the keys of the inverter 1-8, the transformers of the inverter 9 and 10, and the keys with two-sided conductors 11-12. Conversion of a constant voltage to a voltage of superficial frequency is carried out by an inverter made on keys 1-8 in the form of two bridges. As switches 1-8, reverse transistor-biased transistors or thyristors with forced switching nodes can be used. In each bridge, the switching of keys of one rack 1 and 2 (5 and 6) is carried out in phase (i.e., both racks can be replaced by one), and the switching of keys of the other rack in one bridge (3 and 4) is carried out 90 degrees ahead el.grad., in the other (7 and 8) - with a lag. As a result, the primary windings of transformers 9 and 10 form the same form

and shifted by 90 el.grad. voltage (figure 2).

The resulting voltages are transformed and form a secondary four-phase voltage system on the secondary windings of transformers 9 and 10, which is transformed into a three-phase system of a given frequency using 11-12 double-conductor keys, which form a direct four-pulse zero-frequency converter with a three-phase output .

When implementing the proposed spacing keys 11-22, they can be either fully controllable (transistors with diodes) or partially controlled (thyristors), since with the selected form of phase voltage curves, the linear voltages have shown that each switch They have a rectangular shape without a pause, which allows KONwyTHpoBaTb keys without additional switching devices in the whole range of disconnected control angles.

The change (modulation) of the control angles of the keys 11-22 can be carried out according to any desired law. With simultaneous adjustment of the modulation depth, if necessary, the output voltage is controlled.

The control of the converter made by the proposed method is carried out by known control systems.

The block diagram of one channel such (Fig. 4) includes a synchronization device (US) 23 connecting the control cap to the supply network; shaper (F) 24 of the reference signal and a saw-tooth low-frequency driver (SG) 25, a comparator (K) 26 that generates a signal “equality of the reference signal and the SG signal, pulse shaper (FI) 27, generating a signal of a given duration, logical device (LU) 28, provide, with separate control, removal and supply of pulses, valve state sensor (DSV) 29, output device (IU) 30, which generates signals with specified parameters for supplying a valve to the control electrode.

According to FIG. 4, phase voltages. H, - and h on the secondary windings of the transformer node unlock pulses (hatched) of keys 11-14 and form one phase of the output voltage and phase voltage at the output of If (ф) at the trapezoidal signal of the EG. If the keys are fully controllable, control pulses for them can be doubled (one option is shown above the axis, the other under the axis). Corresponding to these variants, the phase voltages are denoted by Zf and Uq ,. Whitewash keys are not fully controllable (anti-parallel thyristors, both pulse systems are formed, but they are fed to the thyristors depending on the current direction (with separate control). With consistent control, the previous 11 and reverse thyristor groups are combined through reactors and pulses are applied to all thyristors. Due to the equalization of instantaneous voltages with the help of reactors and Of both groups, the output voltage curve is known to be further improved.

one

The construction of the moments of occurrence

pulses are shown for one key. Pulse end points are generated at the moment of occurrence of a pulse in the next channel. The keys of the other phases of the direct converter work with the same ZG signal shifted by 120 al. in one direction or another.

This example of a converter with a three-phase output eliminates the pulsation of the active system and the consumption of reactive power with a doubled output frequency, which is typical of converters of the same type with a single-phase output.

Using the proposed method allows to improve the quality of electricity conversion by reducing the amplitude of the pulsator in the output voltage curve, which leads to a decrease in the cost of filtering it, and also allows the pacmHpHtb application area for using control keys with incomplete control, (thyristors), which enables the implementation of converters that implement the method to a wider range of power

rv

T

eleven

P

15

19 20

r ±

forest

ig, 3 Lr U U 10 P P nmrrm

a П П nnnnnrrmnn n 11

four

a

linjUULJIJLR. leUUUUULJLlL U LJ nnn n n

Claims (1)

A METHOD FOR CONVERTING A DC VOLTAGE TO A QUASI-SINUSOIDAL method, which consists in converting direct voltage to a multiphase alternating voltage of increased frequency, transforming it and converting it into a voltage of a given frequency by cyclically connecting each of the phases of the voltage of increased frequency in the order of their rotation to the output terminals of the converter using two-way keys conductivity, they are distinguished by the fact that, in order to improve the quality of the converted electricity and expand the field at changes, on the secondary side of the transformer unit, a symmetrical four-phase voltage system is routed, having a pause of 90 el. in each half-period. hail. _m 1086546