SU1317588A1 - Device for artificial commutation of converter thyristors - Google Patents

Abstract

The invention relates to a converter technique, namely to traction semiconductor devices of a rolling stock. The goal is to increase reliability by reducing switching voltages. The device contains switching thyristors 2-5, to which switching circuits 10-13 are connected. The windings 18, 19 of the switching tr-ra are connected to charge thyristors 6, 8, separation diode 7 and discharge diodes 20,21. Additional thyristors 16, 17 are connected to the junction points of the capacitors and chokes of the LC circuits 10-13. The switching LC circuits 10-13 are switched on with a shift in time, and in each half-cycle of the thyristors switching frequency, excess energy is applied to the LC capacitor The chain is limited at the voltage level of the power source. 2 pcs. with SL with SP 00 00 figure 1 L 2,3.4,5; 6. 8. / H 75, 76.77

Description

eleven

The invention relates to power converter technology, namely, to traction semiconductor devices of rolling stock, and can be used to force the switching of thyristors in frequency converters.

The aim of the invention is to increase reliability by reducing switching overvoltages.

Figure 1 is a schematic diagram of the proposed device; FIG. 2 shows timing diagrams explaining its principle of operation.

The device (Fig. Contains a power source 1, to the sources of which two pairs of serially connected switching thyristors 2, 3 and 4, 5 are connected, a chain of series-connected charging thyristor 6, separation diode 7 and charging thyristor 8, corresponding conclusions of the thyristor converter 9 and also two switching LC circuits 10, 11 and 12, 13, with the first plates of capacitors P and 13 connected to common connection points of switching thyristors 2, 3 and 4, 5, and the first ends of the windings of switching chokes 10 and 12 are connected to the electrodes of the separation diode 7. The device also contains an anode group of distribution thyristors 14, connected by cathodes to cathodes of lockable thyristors, a thyristor converter 9 and anodes to the cathode of separation diodes 7, a cathode group of distribution thyristors 15, connected by anodes to the anodes of lockable thyristors, thyristor converter 9 and cathodes to the anode of the separation diode 7, additional thyristors 16 and 17, each connected between one output of the power source 1 and the junction point of the second plates of the switching capacitors and the second ends of the windings of inductance chokes of LC circuits 10, 11 and 12, 13. In addition, the device is equipped with an overcurrent circuit for recharging LC circuits containing a switching transformer, two of which are primary windings 18 and 19 connected, respectively, to the cathode and anode of the separation diode 7 and to the ends through the discharge diodes 20 and 21 with the terminals of the power source 1,

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the secondary winding 22 of which is connected to the diagonal of a single-phase diode bridge 23-26, which is connected in opposite way to the power supply of the power source 1, and

also, the control unit 27 of the respective outputs connected to the control electrodes of the thyristors of the artificial switching device. Figure 2 shows timing diagrams of control signals switching 2-5, charge 6 and 8, and additional 16 and 17 thyristors, as well as timing diagrams of currents in switching reactors 10.

and 12 and voltages on commuting

capacitors 11 and 13.

I

The device works as follows.

Suppose that in the initial state the capacitors 11 and 13 were charged with the polarity indicated in Fig. 1. For artificial (forced switching) the thyristor of the converter 9 connected by the cathode to the cathode of the corresponding distribution thyristor of group 14, at the time tp include the indicated thyristor of the distribution thyristor group 14 and switching thyristor 2. Under the action of the voltage of the switching capacitor 11 the current from the switched thyristor converter 9 is forced into switching circuit 10 and 11 along the circuit: 9, 2, 11, 10, 7, 14, 9. At time t, the switched thyristor is locked, and the excess oscillating current A resurrection and a switching circuit of 1-0 and 11 LC circuits are closed in a circuit: II, 10, 7, 18, 20, 2, 11. At a time t with a shift of 2/3 half-period of oscillation of the natural frequency of oscillating LC circuits, the switching thyristor turns on 4. Load current of

The LC circuits 10 and II are redistributed into the LC circuit 12 and 13 along the circuit: 9, 4, 13, 12, 14, 9. The excess oscillating current of the recharge of the commuting LC circuit 12 and 13 is closed along the circuit: 13, 12, 18, 20, 4, 13. At time tj, the recharge current of the LC circuit 10 and P drops to zero, commutation thyristor 2 and razg.

divider diode 7 is locked by the reverse voltage of the switching capacitor along the following circuits: II, 2, 4, 13, 12, 7, 10, 1I.

3

With the flow of excess current recharged both LC circuits through the primary winding 18 of the switching transformer on its secondary winding

22 an emf is given, the amplitude of which is the institute which is limited at the voltage level of the power source 1,

by connecting the secondary winding 22 to the source 1 via diodes

23 and 26 along the chain: + 22, 20, 1, 26, -22. Thus, on the primary winding 18, a square-shaped voltage drop occurs, plus when a group 14 thyristor is applied to the cathode through a switchboard, and a minus through a discharge diode 20

to the anode of the commutated thyristor 9, an amplitude equal to the voltage of the power source 1 divided by the coefficient of the transformation of the switching transformer. Typically, the transformation ratio is chosen so as to obtain an amplitude of the reverse voltage pulse on the thyristor of the order of 50-80 V, which provides the passport time t, restoring the locking properties of the switched thyristor. In the moment

H

time t, the current of the LC circuit 12 and 13 becomes less than the load current I discharge diode 20 is closed. If we assume that the current 1 "when switching remains constant, then

the time interval

t tj. the voltage of the opposite sign on the switching capacitor 13 will increase linearly. At the moment of time t, the voltage on the capacitor 13 begins to exceed the voltage of the power source 1, the additional thyristor 17 and the corresponding converter thyristor 9 turn on. In the interval

of time

t

t, the load current is transferred from the reactor 12 to the corresponding thyristor of the converter 9. Moreover, the current of the reactor 12 is redistributed along parallel circuits: 9, 4, 12 13 and 9, 1, 17, 12. Since the capacity of power supply 1 is much greater than capacity switching capacitor, the falling current of the switching reactor will flow mainly through the power source, which significantly reduces the switching voltage

voltage on the commutation

Satore 13.

On the time interval t, the dispensing of the capacitor 11 is performed.

10, 15

20 25

thirty

35

40

45, 50 o switching on the switching thyristor 2 and charge thyristor 8 (at idle converter 9, the dosing and the capacitor 13 are switched on by turning on the thyristor 4). If the surplus switching energy accumulated in the power source is not fully compensated by the power consumption for charging, then it should be withdrawn by one of the known methods, for example, using dependent interruption into the AC network.

After the end of the dose at the time. Tg, the voltage on the switching capacitor 11 may exceed the supply voltage by 10-20%, which is due to the oscillatory nature of the dose process. By introducing active resistances into the charge thyristor circuit, an increase in the attenuation coefficient of the oscillating circuit of the dosage is achieved. As a result, the indicated value of overvoltage decreases to 2-3%,

In the second half-period of the artificial switching device operation, the corresponding thyristor of the converter 9 connected by the anode to the anode of the corresponding thyristor of the distribution thyristor 15 group is forcedly locked. The process proceeds as described.

At time t, the corresponding thyristor of distribution group 15 and commuting thyristor 5 are turned on. At time t, commuting switches are inserted - thyristor 3. The load current flows through the following circuits: 9, 15, 6, 12, 13, 5, 9 and 9, 15, 10, i, 3, 9. The excess recharge current of the LC circuits is closed in the following circuits: 13, 5, 21, 19, 7, 12, 13 and 11, 3, 21, 19, 10, 11. In the time interval t ,, t the load current decays in reactor 10, an additional thyristor 16 is turned on, and the current is closed in the following circuits: 9, 15, 10, 16, 1, 9 and 9, 15, 10, 11, 3, 9. At time t , the thyristors 6 and 5 are turned on, additional charge of the capacitor 13 is made for the price and 1, 6, 12, 13, 5.1.

Thus, during the operation of the proposed device at intervals of TSC, t, the output of the excess switching energy from the switching reactors, as was shown above, an increase in the voltage occurs513

nor on switching capacitors. which allows to limit the maximum voltage applied to the thyristors of the device at the voltage level of the power source and, consequently, increases the reliability of the operation of the proposed switching device. It is known that the magnitude of switching overvoltages uU in the device prototype (without taking into account the active resistance) is determined from the expression

75886

ruy1; i am using a capacitor equal to the magnitude of the overvoltage AUj on the capacity of the power source

uU, uU, from here

where C, C is the capacitance, respectively, of the fc switching capacitor and the power source, If you take a C-25C.

uu,

p is the characteristic impedance of the LC circuit.

(one)

The characteristic impedance p is related to the voltage U on the switching capacitor and the amplitude 1 of the switching current pulse by the dependence

and,

R ---- .

Given this equation, (1) can be written as

 I ,, t

here

uu

yu and,

In

l

to

(2)

etc

where .di - the relative value of switching overvoltages °,

W. - the ratio of the amplitude of the switching current pulse over the load current.

In the prototype device, the coefficient is chosen in the order of 1.2 - 1.25. Then, according to expression (2), the relative value of switching voltages is

U-U 0.8-0.83 i, 2 - I, zb

1-13 of the obtained expression (2), it follows that in those artificial switching devices, where the shape of the switching current pulse is approximated in a rectangular one, due to a decrease in the K coefficient ,. , the amount of switching overvoltages reaches the greatest value: s.

In the proposed device, the value of uU, overvoltage on commi

the current value is --- 5 and agree 2

but (i) the value of the overvoltages uU will be 5 times less than in the device prototype.

As a thyristor converter 9 (FIG, U can take any of the well-known converters: an autonomous voltage inverter, a direct frequency converter, a converter voltage converter into a constant. Control systems of such converters are also known.

In the control unit 27 of the proposed device, control signals for switching and distributing thyristors are generated on the falling edges of the thyristor control pulse 9 (the duration of such a control pulse corresponds to the entire duration of the thyristor conducting state) using an I1 pulses short pulse generator.

40

45

50

55

Claims (1)

Invention Formula A device for artificially switching a thyristor of a converter containing a power source, to the output outputs of which two pairs of serially connected switching thyristors and a chain of serially connected first charge thyristor, separation diode and second charge thyristor, as well as two switching LC circuits, one plates are connected capacitors, each of which is connected to the connection points of the respective pairs of commuting thyristors, and one ends of the windings of the inductor of inductances These connections are connected to the specified charge thyristors with 713 A diode, the latter points of connection, are connected via distribution thyristors to the output of the device connected to the thyristors of the converter, and also a control unit of the device, characterized in that, in order to increase reliability by reducing the switching overvoltages. 75888 it is equipped with additional thyristors, power electrodes connected between the connection points, the second plates and the ends of the windings g inductors of the respective LC circuits and the corresponding output ports of the power supply, and the control inputs to the corresponding outputs of the control unit. FIG. 2