SU447801A1 - Artificial Switching Device - Google Patents

Description

Artificial switching devices are known that contain a filter capacitor, and such a switching capacitor and a choke.

The proposed device is characterized in that it is made of an incompletely controlled single-phase bridge, in the diagonal of which the filter capacitor is connected on the AC side, and the series-connected switching capacitor and the choke on the DC side.

This makes it possible to reduce switching overvoltages and increase the energy performance of the device.

Figs. 1-3 depict the circuit diagram of the device in three variants, where it is used for the artificial switching of a three-phase, single-ended compensating transformer.

Device I consists of a semi-controlled bridge formed by uncontrolled gates 2 and 3 and control gates 4 and 5. The diagonal of the bridge includes: on the ac side, the capacitance b of the filter, and on the dc side, the switching / C node consisting of a switching capacitance 7 and an inductance 8 and serving to lock the controlled gates 4 and 5 some time after they are unlocked. The switching device is connected to the power converter 9 via an uncontrolled rectifier 10.

When applying the voltage of the filter capacitance 6 and the switching 7, it is charged from the network through the rectifier 10 and the load. In this case, the polarity of the voltage on the capacitors corresponds to the signs without brackets in FIG. I,

To turn off the conductive valves of the converter 9, the unlocked control unit valves and the filter capacitance are connected through the control valves 5 and the uncontrolled rectifier 10 in parallel with the converter control's 9 valves so that it closes the vectors The converter drives and the load current begins to flow through the filter capacitance, discharging it. Simultaneously with the switching off of the conductive valves of the converter 9 when the valves are unlocked and 5, the resonant charge of the commutating capacitor 7 through the inductance 8 from the filter capacitance is complete. , on. The guideline on which to the specified Moment corresponds to the signs in brackets (see FIG.). When the reverse recharge current is compared with the load current, valves 4 and 5 are closed, the discharge of capacitance b is stopped, and the load current begins to flow through the inductance 8 and the switching capacitance 7, discharging and then reloading the latter. When in the process of recharging the voltage of the capacitor 7 is comparable to the voltage of capacitance 6, diodes 2 and 3 open, and most of the load current is not flowing into the filter capacitance circuit b, then the charge will start charging from the working phase to the next one. when the voltage on the capacitors b and 7 is comparable to the linear voltage between the indicated phases. Since the capacitance b is chosen to be of considerable size, the switching voltage varies rather slowly, without causing large switching neranes in the network. After the final transfer of the load current from the operating phase to the next switching device, the rectifier 10 turns off and the voltage on the capacitor b is terminated. Thus, at the first switching point, when control valves 4 and 5 are open, the filter capacitance is discharged by the inrush current, giving up the energy stored during the previous commutation. At the last stage of koim-utation, when diodes 2 and 3 are unlocked, it is charged. The specified alternation during each switching of the processes of discharge and charging of capacity b makes it possible to do without additional devices that allow for returning energy from the capacitance of the electrode, V At the same time, due to the large capacitance b, the switching of the current from phase to phase proceeds quite smoothly, without causing overvoltages in the network. However, the dependent discharge of the switching capacitor 7, after its resonant charge from the filter capacitance b, carried out by the load current, makes the external characteristic of a steeply dipping transform and causes overvoltage on the load. To eliminate this, it is proposed to turn on the opposite-parallel-controlled valves of bridge 4 and 5 unmanaged diodes II and 12 (see Fig. 2). In this embodiment, after locking the controlled valves 4 and 5, the process of resonant recharge of capacitance 7 continues and approximately after a period natural oscillations of the circuit formed from capacitances b and 7 and inductance 8, the voltage on the capacitance 7 restores the original value. The valves 2 and 3 are then unlocked, and the process then proceeds as described above. A common disadvantage of the artificial switching devices shown in FIGS. I and 2 is the large voltage amplitude at the switching capacitor 7, which increases its installed power, which is proportional to the square of the voltage. Instead of a common switching node, it is proposed to switch on a similar node parallel to each control valve of the switching device, in order to reduce the power of the switching capacitance. Such a device is depicted in FIG. 3 where inductance 8 and switching capacitance 7 are connected in parallel with controlled valve 4, and inductance 13 and capacitance 14 in parallel of valve 5. In this vacuum generator, also when valves 4 and 5 are turned on, resonant recharging of capacitances 7 and 14 will occur, and then reverse them through diodes II and 12. Thus, the capacitance of the filter b of the filter b will continue. During the period of natural oscillations of the switching circuits formed by capacitance 7 with inductance 8 and volume 14 with inductance 13, diodes 2 and 3 will open, and the process will continue as described above. It is easy to see that although the total value of the switching capacitances has increased B twice, their installed capacity has decreased by one and a half. SUMMARY OF THE INVENTION I. An artificial switching device comprising a filter capacitor, a switching capacitor and a choke, characterized in that, in order to reduce switching overvoltages and improve energy performance, it is made as an incompletely controlled single-phase bridge, in the diagonal of which alternating current is turned on the capacitor of the filter, and on the DC side, the switching capacitor and the choke are connected in series, 2, the device according to claim I, - in parallel controlled valves of the bridge included diodes, 3, Device according to PP, I and 2, about aphid. So that the chains of series-connected commutating capacitor and throttle are connected in parallel to each controlled valve of the floor of the controlled bridge.

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