SU1317623A1 - Method of controlling bridge rectifier converter - Google Patents

Abstract

The invention relates to a converter technique and can be used to control rectifiers and driven inverters. The aim of the invention is to increase the power factor of the converter. The use of this control method allows one to control the voltage of the mites and the network-driven inverters with a wide change in the value of the emf of the dc source, to maintain the current within the specified limits due to the fact that when the dc value exceeds the dc current rectifying mode and. when it decreases below the minimum value in the inverter mode, unlock two valves of the same phase of the converter, and then prohibit unlocking of all. gates. In the case of a decrease in the value of direct current below the minimum value of the current setpoint in the bitwise mode and when its maximum value is exceeded, the current setting in the inverter mode removes the prohibition on valve unlocking. 2 hp f-ly, 8 silt .. (/) SO h O) y OE

Description

113

The invention relates to a converter technique, in particular to methods of controlling a bridge converter, which is equipped with controllable gates and can operate as a gate and driven by an inverter network.

The purpose of the invention is to increase the power coefficient of the converter.

FIG. 1 is a diagram of a single-axis converter J in FIG. 2 and .3 are the diagrams of voltages and currents during the operation of a single-bridge converter, respectively, in the up-and-down and inverting mode, in FIG. 4 is a block diagram of a control system implementing the proposed method for a single-bridge converter j in FIG. 5 is a schematic diagram of the four-bridge converter in FIG. 6 shows voltage diagrams for operation of a four-bridge converter i in FIG. 7 is a block diagram of a control system implementing the proposed method for a four-bridge converter; in fig. 8 is a block diagram of a control system implementing the proposed method in. in accordance with claim 3. .

A three-phase bridge converter (Fig. 1a) is formed by valves 1-6, which are connected directly through a transformer to an alternating current network. On the side of the alternating current of the converter there are phase EMF 7 (e „, s, e) and inductance 8 (L ..). On the DC side of the converter between its poles are connected in series the source 9 of the constant electromotive voltage (e) and reactor 10 with inductance L. The source of the 9 emf can be a direct current machine, which acts as a motor when the converter is operating in the me mode or generator during operation inverter in inverter mode. In addition, as a source of emf 9, a transfer or insertion converter, battery, or a capacitor battery can be used. FIG. 16 shows a circuit for switching on a capacitor battery 11 instead of a source of 9 EMF. During operation of the converter, for example, disconnectors 12 and 13 are turned on as a rectifier and capacitors of the energy storage capacitor are charged. Dp the accumulated energy2

The switches to the AC mains disconnectors 12 and 13 open, disconnectors 14 and 15 are turned on, and the converters ,. phase change pulse generator

control (by changing the adjustment angles) is transferred to the inverter mode.

FIG. Figures 2 and 3 show the time-varying EMF curves, voltage

control currents and pulses, namely about axis 0 - three-phase system EMF, ec, e, PC relative to axis Oj - control pulses that enable even gates (indices

the pulses correspond to the positions of the valves in FIG. 1a), with respect to the axis Oj - control pulses, enabling odd gates, with respect to axis 0 - valve currents (currents of even gates are shown above the axis, and odd ones - under the axis: the dashed lines indicate the setting levels of the maximum and minimum currents) 5 relative to the axis Oj - Secondary voltage Uj and emf

e source 9 EMF

FIG. 4 shows a block diagram of a control system comprising a comparison unit 16 provided with a switch 17 of a kind of operation. Two exits

the comparison unit 16 is connected to the control inputs of the thyristor control units 18 and 19 1,3, 5 and 2, Л, 6 respectively, and to the locking inputs of these blocks, and to one of the

THEM, for example 19, through time delay block 20. The magnitude of the direct current is detected by the sensor 21, made, for example, in the form of a direct current transformer. Block- 16

Comparison contains elements 22 and 23 Comparison with settings .. and accordingly; accordingly. The outputs of the elements of the settings are connected to the switch 17 directly or through inverters

24 and 25, One of the outputs of the switch 17 is connected to one input of D-flip-flop 26 directly, and the go is via the logical element HE 27. The outputs of D-flip-flop 26 are the outputs of block 16 of comparison.

In the rectifier mode at a current lower than both settings, the signal from the logical element HE 27 transfers the D-flip-flop 26 to the state at which the control signal is sent to the control blocks 18 and 19 and the converter operates in the normal mode. As the current rises,

its magnitude i ..

input signal to

3 13176234

The D-flip-flop disappears, it remains in O, at which the power ratio, the operation of the circuit does not change. With increasing current 1, above, d (. A signal appears at the other input of D-flip-flop 26, the signal at its control output disappears and a signal appears at the locking output that blocks the pulses of the control blocks 18 and 19, and the introduction of delay unit 20, the delay and forage of pulses of one of the thyristor groups, namely 2, 4, 6, occurs with a shift by one repeat interval, which results in the converter's operation having the greatest possible value. point in time when during normal operation the rectifier occurs at the increase of the direct current ij, and the value of this current is between the values of the current settings 1y

smart x The current rise is because 4ToUc (-e., the constant rise time is determined by the ratio L to L- ..

Difference and .g perceived

Difference and .g perceived

Te converter in combustion mode 15 by reactor 10.

single phase valves After this, the current, at time t, current i reaches the value of current I and as a result, this I begins to decrease, and when it decreases below the value of "" "", a signal appears at the output of the element, after which the cycle repeats. 20

In the inversion mode, the process is repeated in reverse order. In order to match the polarity of the voltage of the elements 22 and 23 of the comparison in both modes by the switch 17 25 of the valve py), in the other group an impulse blocking was introduced into the circuit of their output circuits with a twist 24 and 25. one regular impulse

If the converter works only in inverted mode, the translation

It is commanded to switch to single phase mode, which is executed as follows (see pulses on axes 0 and Oj): the next pulse after t is blocked (pulse 5 in Fig. 2) and all pulses from its group (in Fig. 2 the pulses of an odd group (in Fig. 2, the even pulses block-: Yuts not immediately, but after the

it is in single-phase overturning mode of the next in this group of impulse 6).

can be done by simply opening the valves of those phases in which the conductive valves already exist. The control circuit dp of this case is shown in FIG. 8. In addition to the indicated elements, a block 28 of disposable pulses is introduced into it, which forms single pulses with a duration of 60 ° for a bridge circuit. These pulses are applied to all thyristors 1-6 of the converter simultaneously with the application of the blocking voltage to control blocks 18 and 19. When the control voltage is applied to the control blocks 18 and 19 at the same time, it supplies a signal to bring the block 28 to the working position.

Block 28 of disposable pulses can be performed, for example, in the form of a capacitive storage device equipped with a charging device and a triggering device.

Plots on .fig. 2 illustrates the operation of the converter in the rectifier mode and the gradual growth of the counter EMF e of the source 9 of the EMF (for example, the process of charging a capacitor battery 11). Valves 1-6 are pulsed with control angle d

AND

transducer has the highest possible value. The process is shown starting from a certain point in time, when during normal operation of the rectifier an increase in the direct current ij occurs, and the value of this current is between the values of the current settings

mind x The current increase occurs because 4ToUc (-e., the constant of the rise time is determined by the ratio L to L- ..

Difference and .g perceived

reactor 10.

valve), in another group of pulses, blocking is performed with a delay of one regular pulse

It is commanded to switch to single phase mode, which is executed as follows (see pulses on axes 0 and Oj): the next pulse after t is blocked (pulse 5 in Fig. 2) and all pulses from its group (in Fig. 2 the pulses of an odd group (in Fig. 2, the even pulses block-: Yuts not immediately, but after the

five

0

five

0

five

As a result, the current continues to flow through the valve 3, at the time t the current switches from valve 4 to valve 6 and after it ends the single-phase mode starts: current i passes through valves 3 and 6 connected to the same phase on the AC side in this example to phase C ..

In single-phase mode, the current LJ decreases with a constant voltage, where R is the resistance of the reactor 10, two valves and other circuit elements. If a capacitor bank 11 is used, the electromagnetic energy of the reactor 10 is transferred to the energy of capacitors 11 and the value of e continues to increase. At time t, the current decreases to a value of "" "and as a result, the command is issued to resume the formation and supply to the valves 1-6 of control pulses, as before, with a minimum angle of regulation. The normal operation of the converter is restored, the rectified voltage becomes more EMF e due to what the current i increases again. Going on 5, 13

a row of a capacitor battery 11 (increase in c).

After the current i becomes equal to 1 ";., Kc the described process is repeated. When charging the capacitive accumulator 11, the process ends when the emf does not become equal to the maximum values of the rectified voltage, and the current i drops to zero.

The plots in FIG. 3 illustrates the operation of a bridge converter in inverter mode. Suppose that on the DC side as a source of emf e, a charged capacitor 11 is turned on and the process consists in transferring its energy through an inverter to an AC network. The capacitor 11 is gradually discharged and, accordingly, decreases i. The gates 1-6 of the inverter can be unlocked with a constant angle of advance B, the value of which is chosen as small as possible, but such that the switching of most currents close to 1 "", s, is successful. Power factor improvement is achieved if the inverter is equipped with an extinction angle adjuster that changes the advance angle so that for all current values the extinction angle is possibly minimal.

The process in FIG. Figure 3 shows starting from a certain point in time when, during normal operation of the inverter, the current decreases, and its value is between the values of the current settings 1 "a. and IMUU. Current reduction sweat occurs.

L & H

This counter voltage of the inverter Uj is greater than the emf of capacitor 1 (e). The difference is compensated for by the electromotive force (EMF) arising at the reactor 10 with decreasing -current. At the time t, the current becomes equal to the setpoint current, and as a result, a command is given to switch to single-phase mode. Such a transition can be carried out in the same way as when the converter is operating in the rectifier mode. As a result, starting from the moment t, the counter voltage of the inverter U 0, the valves 5 and 2, which are connected on the AC side to phase a, are flowing through. In the inverting mode, the single-phase mode can be switched to premature unlocking of the valve that belongs to the same phase as conductive in this gap

36

time one of two gates, and the subsequent blocking of all pulses. So, immediately after the moment t (Fig. 5), it is possible to prematurely apply a pulse to the valve 5 and then block all the pulses. The current passes from valve 3 to valve 5, and single-phase mode with conductive valves 5 and 2 starts before tj.

In the single-phase mode, the current under the action of the emf e begins to increase, part of the energy of the capacitor 11 is transferred to the electromagnetic energy of the reactor 10. At the moment t, the current reaches the value of the installation current. and as a result, the command is issued to resume the formation and supply to the gates 1-6 of control pulses, still with the minimum allowable angle of angle B. The normal operation of the converter is restored, again 7 e1 the current decreases, the rediation continues. giving energy from a capacitor 11 in

AC network.

After current i becomes equal to -f, the described process is repeated. The process ends with full discharge of the capacitor 11.

Thus, the application of the proposed bridge converter control method allows it to operate both in the rectifier mode and in the inverter mode, with a wide change in the emf value of the dc source source, to maintain the current within the specified limits and to ensure a high power factor value.

However, when using the proposed control method, power consumption is uneven in the straightening mode and the power output in the inversion mode. The negative effect of this deficiency on the AC network can be reduced by connecting to the network in parallel two S1I more converters operating with a shift in time intervals of normal operation. In addition, a multi-stage cascade converter can be used, for example, according to the scheme of FIG. five.

The work of such a converter in

The straightening mode is illustrated in FIG. 6, the axis Oj, and in the inverted mode, by the graph in FIG. 6, axis Oy. EMF e of source 9 EMF increases during operation in the output mode, and decreases in operation in the inverter mode (for example, as a result of charging and discharging capacitors of the capacitive energy storage device). The change in the rectified voltage Uj is shown in the first approximation as its constant change. this component.

The control block diagram for four bridges is shown in Fig. 7. The control circuit of the bridge 1M is not different from that of FIG. 4. The remaining 2M-4M bridges have comparison blocks 29-31, control blocks 32-37, and time delay blocks 38-40. The circuit of their connection does not differ from the circuit of FIG. 4. However, since these bridges are transferred from a single-phase mode to a normal one not by a current signal, but by a voltage signal, the input voltage signal on the capacitor 11 is compared in blocks 29-31 compared to voltage settings 1/4 U, 1/211, i, j | respectively for bridges 2M, 3M and 4 m. The magnitude of the voltage on the capacitive storage device 11 is determined by a voltage sensor 41 made, for example, in the form of a divider. To convert the 2M-4M bridges to single-phase mode at the beginning of the charging process of the capacitive storage device 11, the signals to the control units 32-37 are supplied from one comparison unit 42 when the voltage supplied from the voltage sensor 41 is less than / W. Comparison units 29-31 are connected to the control inputs of the control units 32-37 directly, and to the locking elements through the logical elements NOT.

When operating in the rectifying mode (Fig. 6, axis 0), at times tj, tj, t4, in accordance with the increase in the emf e, a single bridge is introduced, which was previously in the single-phase mode. The proposed control with alternation of normal and single-phase modes during the whole process of growth is carried out on one of the operating 1M-4M bridges. So, in the span in controlled mode

there may be a bridge W or 2M and, accordingly, in normal mode, the bridge 2M or IMi and the 3M bridge in this period of time are in single-phase mode. One of the possible management methods is that one bridge is selected for control, for example, 1M, and the remaining bridges are in normal or single-phase mode depending on the required level of rectified voltage.

When the superature is started up at the moment C on the 2M, 3M, 4M axles, the control pulses only unlock two valves of the same phase. To transfer the bridge from one phase to normal, control pulses are sent to all its valves.

When operating in the inversion mode (Fig. 6, axis Oj) at times t, tj, t in accordance with a decrease in the EMF, a single bridge is output (transfer from the normal mode

in single phase). The proposed control with alternation of normal and single-phase modes during the whole process of e decline is carried out on one of the operating bridges.

As can be seen from the graphs, when using a multi-bridge cascade converter, oscillations of rectified voltage (in accordance with the number of bridges) are significantly reduced. In addition, it is possible to reduce the range of current variation, to reduce the difference

settings, the difference arises when managing one of several bridges connected in series, and as a result of the transition from a single-side converter to a multi-bridge, the negative influence of the control method is significantly reduced.

 on the AC network due to uneven power consumption or power consumption.

Formula of invention

40

Claims (3)

1. The control method of the bridge valve converter, which sets the maximum value of the current setting, measures the value of the direct current, compares it with the set current setting, generates the control pulses of the converter's converters and unlocks them with normal phase alternation, in order to increase the power factor, set the minimum value of the current setting, compare it with the measured value of the direct current, when the value of the direct current exceeds the maximum value of In the inverter mode, the current in the rectifier mode and when it drops below the minimum setpoint value in the inverter mode unlocks two valves of the same phase of the converter, and then prohibits all valves from unlocking, when the DC value drops below the minimum value of the current setting in the rectifying mode and when the maximum value of the current setting in the inverter solution is removed. The prohibition on unlocking the valves. 2. The method according to claim 1, characterized in that for unlocking Two valves of one phase of the converter fix the open valve and prohibit the unlocking of the next valve of the converter. 3. A pop method, 1, characterized in that for unlocking two valves of one phase of the converter in the inverter mode, the phases are fixed, the first valves of which are open, and the second valve is unlocked in one of these phases. but V 1 So e. e. c (0  L 6 g Jlz ILI  S jbl J is qJUZ.Z / ts 0, 1 t, and S c o (fe Fig.Z /// l FIG. five Vd 1M / r mfHT iftftrc in.ZM Iftftft Iftftftr } m, gn: ffi.zM Jfl.UH IMrtrL CPU g. B 1mgzm, ri TT t; II II (p I rT H rV4 H4i% 4T1  II I I I. | I J -Y y / st / r Z2 fj (x) 4 . (ig.V Compiled by V. Mironov Editor A. Ogar Tehred V. Kadar 2432/53 Circulation 660 VShPI State Committee of the USSR on inventions and discoveries 113035, Moscow, Zh-35, Raushsk Haj5., 4/5 Correct Signature Production and printing company, Uzhgorod, st. Project, 4 Proofreader L.Pilipenko Subscription