SU347863A1 - WAY OF MANAGING DIRECT - Google Patents

Description

There are known methods for controlling a direct frequency converter with artificial commutation by means of a waveform, we have the output voltage (current) curve to a given one.

The proposed method differs from the known ones in that the COM capacitor capacitor charges up to the maximum time of an APM power supply: the network at a given JMO element, and the output voltage curve is formed by alternating zero voltage intervals with phase voltage intervals:: closest to the specified value .

This makes it possible to increase the power and indicators of the converter.

FIG. 1 shows a scheme for implementing the proposed control method; in fig. 2 is a block diagram of the comparison; in fig. 3 - graphs of currents and voltages in the circuit.

Consider the following control method using as an example the operation of a single load phase of the converter shown in FIG. one.

This converter has one switching unit common to one phase of the load, consisting of a switching throttle /, switching capacitor 2 liters of two switched on and off-parallel commutator1, their tyrstors 3 and 4.

A comparison in which a comparison of a signal proportional to, eg, a load load generator, occurs, with the voltage of the master oscillator 5, and control pulses are generated for switching a positive or negative pulse (load) to load. The distributor 7 distributes these pulses to the corresponding valves of the comylects. The distributor is controlled by two blocks: a unit 8 sampling the polarity of the phases of the supply network and a block 9 of the choice and the closest amplitude of the phase to the modulating signal.

At time point j, the signal C, phase C.4, which is closest to the signal, yy (see fit. 3), includes thyristors 10 and //, a positive voltage pulse is generated in the load, the commuting mutated 1sator 2 is discharged almost to zero naira wives

A part of the output voltage is supplied to the comparison device} 2 (see Fig. 2), where it is added to the antiphase signal of the BSG master oscillator, then this is integrated and fed to the threshold devices 13 and 14. The increasing integrated total loss at the moment / reaches the threshold tensions L ,,: -. Block /, generates a pulse to turn off the main valves 10 and //. To shut down working vectors, you need to prepare

switching co-capacitor for switching.

For this purpose, pulses are supplied to the main thyristor 11, connected to the Bay1bolb negative phase, the main thyristor 15, connected to the most positive phase, as well as the mutating valve 3. The capacitor 3 (arises up to double linear voltage UAB valve 75, the thyristor 10 is turned off due to natural switching, and the load current closes through valves 11 and 15. When the charge of the capacitor is over, the control emulsion is immediately applied to turn on the thyristor 4. The capacitor starts discharging, the discharge current of the condensate The capacitor will be directed oppositely to the current of the thyristors 11 and 15 and will reduce it to zero. To maintain an unchanged capacitor discharge circuit, valves 16 and 17 are switched on, which are turned on by the oppositely switched off Tirycors 11 and 15, the capacitor No. is almost discharged to zero The operation time of the valves 16 and 17 (as long as the switching circuit current exceeds the load CURRENT) is BpeTvieHeM, provided to restore the control properties of the switched off T1 thyristors.

/ With the inductive nature of the load, it is necessary to ensure the flow of reactive current, otherwise it will additionally charge the switching capacitor. In order to ensure the flow of reactive current, two valves in the main set, just left from work, which close the load circuit, at the time in question, these are valves 10 and 18. The load current will be circulated in a short circuit (open loop, and nair (a woman at load 1 will be zero).

At time B) of the c (CM. Fig. 36), the integrated difference reaches zero voltage, the sensor 19 of zero cure will detect the zero crossing of this difference in the negative direction and will generate a control impulse on the activated positive pulse on the load. This includes valves, the linear voltage on which is close at the moment to the reference. After the integrated difference reaches the value Lln + again, the switching process is repeated (rits.

By achieving the integrated sum of the positive horizon f /.-, i (see Fig. 3) on

the load is turned on. the zero voltage is turned on, and when the zero threshold is reached in the negative direction, a positive pulse is applied to the load. When changing the polarity of the modulating signal “and the load is now

negative pulses are given upon reaching the inter- nounced sum of the zero threshold in the positive direction and zero voltage when compared with the negative level.

The emerging voltage peaks at the end and the beginning of positive (rational) impulses of nanrheng (if the amplitude of the impulse on the load is smaller than the envelope of the maximum linear voltages) are practically

affect the harmonic composition of the output voltage, since their duration is equal to the switching interval, i.e., about 100-200 µs-sec.

Thus, the proposed method of controlling the frequency converter with direct connection and artificial switching allows to improve the shape of the output voltage and at the same time ensures the constant switching capacity of the MUT1 COD node by maintaining the amplitude of the N and the switching capacitance at a constant level without using additional sources for its charge.

Present Invention

SIOSSB control directly;: iy, m frequency converter with artificial commutation by approximating the shape of the curve

output voltage (current) to a predetermined one, differing in m. that, in order to increase the energy performance of the converter, the com- muting capacitor is charged from the maximum dGal at a given time,

the phase voltage of the i.power network, la the output voltage curve is formed by alternating zero voltage intervals with the phase voltage intervals closest to the specified value.

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