SU1179499A1 - Single-phase reversible converter with artificial switching - Google Patents

Description

The invention relates to electrical engineering and can be used to improve the energy and dynamic performance of two-piece reverse single-phase converters with zero output, which are widely used in small and medium-sized electric drives.

The purpose of the invention is to simplify the converter. ten

FIG. 1 shows a circuit diagram of a converter with two separation diodes; in fig. 2 and 3 - converter with one divider diode; in fig. 4 - 15 diagrams of electromagnetic processes in the converter; in fig. five - . timing diagrams of the output voltage (a) and current (b) of the converter, valve state diagrams (d) ₂ 0

Follow up the control signal (c), which illustrate the operation of the converter in the mode of multiple switching of thyristors on the network period. 25

In the drawings, marked and _to , ί _κ voltage and current of the k-th element of the circuit; and _y , and _cf - control and reference voltage in the system of pulse-phase-<. thyristor control; - ₃ θ

control voltage of the thyristor.

The device (Fig. 1) contains power thyristors 1-4, forming a pair of parallel-parallel connected: on thyristors 1 and 3 and thyristors 2 and 4.

These thyristor pairs are connected to the secondary winding of the transformer 5 with the middle output forming the first output terminal, and the free terminals of the thyristor pairs 1-4 are combined to form the second output terminal for connecting the load 6.

The converter also contains 45 artificial switching nodes, including a single-phase bridge on commutating diodes 7-10, the diagonal of alternating current of which is connected to the secondary winding of the transformer 5.50 and the series-connected switched capacitor 11 and choke 12, which are shunted in the conductive the direction of the bridge by the commutating thyristor 55, as well as the separation diode 14, connected by the anode to the cathode of the commuting thyristor, to the anode

which the cathode is connected to the separation diode 15, and the other opposite conclusions of the separation diodes combined and connected to the second output terminal.

With such a construction, the artificial switching node can be used to perform artificial switching in turn in both valve groups of the reverse converter. It may be necessary to control the converter using the method of multiple switching of thyristors on a period, network, or, for example, when using this device as a direct frequency converter.

The operation of the device, we consider first with a single turn on thyristors. The advantage of reversible converters with artificial switching is the possibility of implementing joint coordinated control of valve groups without equalizing currents. For this, it is necessary that one, for example, a cathode thyristor group, works with leading control angles -ίϊΎοί _κ <Ο with artificial switching, and the other, for example, the anode group, works with lagging control angles with natural

switching. Under the condition // = οί, the instantaneous voltage curves at the outputs of the valve groups will be identical, and there will be no need for balancing inductors. We also believe that the cathode group operates in a rectifier mode with control angles that do not exceed / k \ / <90 el. deg., and the anode control group prepared for the inverter mode, working with angles greater than € about,> 90 el. hail. Since only one valve group should work with artificial switching in this case, the converter can be made without diode 15 in a simpler version (Fig. 2). To illustrate the processes of the '6 converter in the mode of a single turn-on of the thyristors, time diagrams of voltages and currents are used (Fig. 4).

When connecting the converter

to the mains, the capacitor will be charged with a polarity indicated by

scheme without brackets. Due to the presence of

four

3 1 1 7 (

The charge circuit of the inductive elements of the initial voltage on the capacitor is set at a level higher than the amplitude of the voltage on the secondary winding of the transformer ₅ and therefore the diodes 7-10 are locked. Let the load current flow through the circuit containing the left half winding, thyristor 2 and load 6.

At the beginning of switching, control impulses are fed simultaneously to the next power thyristor 4, commuting thyristor 13, and also according to the rule of joint coordinated control to thyristor 3 of the inverter group. In this case, an auxiliary oscillatory overcharge of the capacitor along the circuit containing the thyristor 13 and the choke 12. After the completion of the auxiliary recharging, the polarity of the voltage across the capacitor will be shown in brackets. The subsequent working overcharge then follows two parallel loops, one of which contains choke 12, diodes 7 and 8, and the other choke 12, diode 14, on-line thyristor 2 and diode 8. At the time when component 3

the reverse charge current is compared with the direct load current in thyristor 2, the latter is turned off.

After switching off, the reverse voltage is applied to the thyristor 2 for approximately half a period of its own oscillations of the switching node, which is released on diodes 7 and 8.

At this time interval, the switching thyristor 13 also restores the locking ability. After turning off the thyristor 2, the current of the left half-winding of the transformer begins to decrease, flowing through the circuit containing diode 8, capacitor 11,. four

choke 12, diode 14 and load 6.

In this case, the capacitor will be recharged, having the voltage polarity again indicated in the ’scheme without brackets. Under the influence of the voltage on the capacitor, the load current begins to pass into the circuit of the next power thyristor 4. Switching is completed when all the current passes to the right. the half-winding of a transformer with Tiris-5: torus 4, and diodes 7-10 are again locked. Switching current from thyristor 4 to thyristor occurs

similarly. In the inverter mode, current switching between thyristors 1 and 3 occurs naturally according to the usual rules.

The converter works in the same way if the artificial switching is performed in the anode group and the cathode group of the thyristors operates from the natural switch 3 days. In this case, a simplified version of the converter without diode 14 has the form shown in FIG. 3

Let us consider artificial switching in this device by the example of transferring the load current from thyristor 1 to thyristor 3. After supplying control pulses to thyristors 3, 13 and 4, an auxiliary overcharge of the capacitor along the thyristor circuit occurs 13

3 and choke 12. Reverse working overcharge also occurs along two parallel circuits, one of which contains choke 12, diodes 7 and 8, and the other - choke 12, diode 7,

? opposite thyristor 1 and diode 15. After switching on, thyristors 1 and 13 also have the ability to restore the locking ability under the influence of reverse voltage,

} released on diodes 7 and .8. In this case, the current of the left half-winding of the transformer is forced to close along the circuit containing the load 6, diode 15, capacitor 11, choke 12, diode 7,

. decreasing and charging the capacitor. In this case, the current of the right half winding begins to increase, flowing into the next power thyristor 3. The switching also ends when diodes 7-10

, under the influence of the voltage on the capacitor will be locked.

It is obvious that the basic properties and characteristics of both considered variants of the converter are the same,

^: and preference for one or the other can be given only in the specific conditions of practical application. In both cases, the converter consumes current from the mains with leading

v relative to the phase shift voltage, so that it can be classified as a compensation rectifier. It is known that compensation rectifiers work with opera ^; by the shear factor and the poet—

are able to generate reactive

power to the network, and in the same

volume in what usual rectifiers

five

1179499

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consume it. However, the functionality of a more complex version of the device (Fig. 1) is not limited to the specified scope. The presence of an artificial switching node (Fig. 1) allows you to control the converter when you turn on the thyristors multiple times on the network period and thereby significantly expand its frequency bandwidth. This possibility is illustrated by diagrams (Fig. 5). The flow of commutations in the valve groups of this converter occurs in a similar manner and therefore is not considered. With repeated switching on, it is also advisable to control the valve sets according to a joint coordinated method, which eliminates the possibility of a balancing current in static and dynamic modes. To this end, as follows from the state diagrams of the valves (Fig. 5 and 3), control pulses are simultaneously applied to both antiphase thyristors connected to the same half winding of the transformer.

On these diagrams, the areas of the conductive state of the valves are blackened. It is believed that the thyristors are controlled in accordance with the well-known vertical principle, while the switching times of the thyristors are located at the intersection points of the control and the reference and _op voltages (Fig. 5 6). In addition, to improve the shape of the output voltage, additional commutation is carried out at the moments when the mains voltage passes through O,

'n, 2 ((, ... Control pulses for the switching thyristor and are formed at a conditionally positive load current (βΐβη ί ₆ = 1) on increasing sections of the reference voltages, and at a negative load current (s1gr _B = -1) - on decreasing sections of the reference voltages. From the diagram it can be seen that in the interval O - ν _ζ at positive values of control voltage and load current alternately thyristors 1 and 3 work, while turning on thyristor 3 in this case occur with artificial switching, and turning on thyristor 1 - with natural commutation. In this range, most of the time the inverter operates in the rectifier mode. In the range -24 V ₂ (in are alternately thyristors 2 and 4. At the station K-V ₂ due to the decrease of the control signal and the subsequent change its sign inverter most of the time works in the inverter mode Similarly, the processes proceed at negative values of the control voltage and load current. From the diagrams presented, it follows that when the thyristors are repeatedly turned on, the converter has a higher speed, How does it acquire the ability to work out control actions with a frequency exceeding the frequency of the supply network? The level of the initial voltage on the plates of communi

The capacitor in this device does not depend on the angle of control of the thyristors and the load current, and therefore the adjustment properties of the transducers with independent oscillatory switching are not inferior to the properties of conventional transducers with natural commutation.

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1179499

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Claims (1)

REVERSE PHASE CONVERTER with forced switching having a single-phase transformer, the secondary winding of which is provided with a middle terminal, forming the first output terminal, and each of the free .vyvodov winding connected to a pair of power thyristors, as well as artificial switching unit, characterized in that, in order simplification of the converter, the primary winding of the transformer forms the input pins, the indicated pairs of power thyristors are turned on in anti-parallel, free combined pins to form volts The output is output, and the artificial switching node is made in the form of switching diodes forming a single-phase bridge, the AC diagonal of which is connected to the free secondary terminals, and the DC diagonal includes a switching capacitor and a choke, which is shunted in the bridge conducting direction by a switching driver; at the same time, the diagonal of the direct current of the bridge is connected with one or two additionally introduced reverse separation diodes to the second output terminal with one or two Displayed DC. M & WITH WITH ί 1179499 2