SU473269A1 - Control method for autonomous inverter - Google Patents

Description

one

The invention relates to the field of converter technology and can be used in voltage inverters operating on a load with a low power factor, for example, in thyristor sources of reactive power for driving and controlling asynchronous generators.

A known method of controlling a three-phase autonomous voltage inverter with interphase switching involves the formation of a series of control pulses with a duration of 120 e. hail, and feed them to the inverter power thyristors at intervals of 60 el. hail, in a sequence corresponding to the order of their work.

The known method of controlling the thyristor inverters of the specified type does not allow for changing the angle of control of the thyristors and thereby adjusting the output voltage of the inverter with its constant power circuit without additional power devices.

According to the proposed method, in order to regulate the output voltage of the inverter with a constant power circuit, a narrow control pulse is applied to the control electrode of each thyristor during the working period, in accordance with the specified order of operation of the thyristors, and after an adjustable time delay a repeated control pulse. FIG. 1 shows an autonomous voltage circuit with reverse and cut-off diodes (the numbering of the thyristors corresponds to the order of their operation); in fig. 2 shows time diagrams of currents and voltages on the elements of the specified inverter at

the operation of its pa inductive load with a known control method (a) and the proposed method (b).

The inverter is controlled as follows. Let, in accordance with the control law, include the thyristor T of the inverter, the inductive load current (/ fout)

conducts thyristor Ti. According to the proposed method, the thyristor Gz is initially supplied with a narrow control pulse (Fig. 26). The previously charged capacitor Cis ("plus on the left plate) starts to discharge in this case through the thyristor Ti along the circuit:

Ci3-Ti-Gz-Li3.

When comparing the discharge current of the capacitor and the load current, the thyristor TI closes, then the reverse voltage is applied to it due to a drop in the voltage of the D and D diodes as the capacitor Cia continues to discharge in the following circuit:

Cis-DI-DI Gz-Li3.

Further, the capacitor current Cis, decreasing, again becomes equal to the load current flowing at this time through D :, and Dx turns off, as a current flowing through it equal to the difference between the load and switching current.

When the voltage of capacitor Ct3 is reached, which is equal in magnitude to the input voltage of the inverter, diode D4 turns on and the recharging of the capacitor ends. Thyristor Gz is turned off, because the load current of phase B due to inductive load continues to flow in a non-conductive direction through the reverse diode Dz (see Fig. 26), / tz, / D) - Diode Dz turns off

3

earlier when disconnecting T.

The thyristor Gz is opened by supplying the second control pulse through an adjustable time delay (a) greater than or equal to the time of the load current flowing through the reverse diode Dz.

FIG. Figure 2 also shows the voltage across the thyristor (t / Ta) n phase voltage (Fout) at two values of the delay angle a.

The minimum delay of the repetitive control pulse per thyristor is 30 el. hail, when the inverter is working on an indicative load. With an increase in the power factor of the load, the magnitude of the minimum delay decreases (the proposed method can be realized with the MOHI coefficient, the load of no more than 0.55). Thus, the proposed method allows you to adjust the output voltage of the inverter with its measuring input and without additional power elements, which simplifies the device in the sawn and expands the field of application of the pivotver with interphase switching.

Subject invention

The control method of the autonomous inverter with interphase switching according to the scheme with

reverse and cut-off diodes when operating on an inductively active load by forming a series of control pulses and supplying them and power thyristors in accordance with the order of their operation, characterized in that, in order to control the output voltage of the inverter with a constant power circuit, control During the working period, each electrode of each thyristor is supplied with a narrow control pulse, in accordance with the indicated order of operation of the thyristors, and through an adjustable time delay - a repeated control pulse.

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