SU1229931A1 - Device for controlling self-excited inverter with tracking - Google Patents

Abstract

The invention relates to electrical engineering and can be used to create frequency-controlled electric drives. The purpose of the invention is to improve the harmonic composition of the output voltage. The device contains an adder 1, a source 2 of a controlled voltage, a generator of 3 clock pulses, a unit 4 for the formation of a control unit. voltages, integrator 8, two threshold nodes 10 and 11, control valve and their pulses (RUI) 13. Introduction to the device design of the simplest additional nodes: frequency divider (QH) 5, trigger 9, two-position inverter 6, implemented on the basis of peak electronic circuits, allows to improve the harmonic composition of the output voltage of adjustable half-bridge inverters. Additional symmetry in the process of forming the output curve is introduced by clock pulses coming from the first input of DC 5 through disjunctor 12 to the input of RUI 13 and at the beginning of each half period. There are no even harmonics in the output signal spectrum, the pulse duration of the voltage curve increases sequentially as it approaches the middle of the half period, which also improves the quality of the output energy of the device. 2 Il. & (L you go () WITH 00 f1 / g. 1

Description

The invention relates to electrical engineering and can be used to create frequency-controlled electric drives based on autonomous voltage inverters.

The purpose of the invention is to improve the harmonic composition of the inverter output voltage.

FIG. 1 shows a functional diagram of the device; 2 shows timing diagrams explaining the principle of operation of the system.

The output voltage of the inverter, whose reduced value is designated as KoUsbix, is fed to the plus input of the adder 1. The minus input of the adder 1 receives the sinusoidal control signal of the control voltage source 2, consisting of successively connected clock generator 3 and the control forming unit 4 a tensioner. The frequency of the control signal is determined by the pulse frequency of the 3 clock pulse generator, which is directly connected to the control voltage generation unit 4 (digital sine wave generator), as well as frequency divider 5. The output of the adder 1 directly and through the logic inverter is connected to the two terminals of the on-off switch 7, the common terminal of which is connected to the integrator 8, and the control circuit of the switch 7 is connected to the output of the counting trigger 9 connected to the first output of the frequency divider 5, the output signal DSCI) which is shown in figa.

The output of the integrator 8 is connected to the threshold nodes 10 and 11, which through the disjunctor 12 are connected to the distributor 13 of control pulses. The input of the disjunctor 12 also receives the signal from the second output of the frequency divider 5 (Us b) in Fig. 2a).

The operation of the device is carried out as follows.

The clock pulse generator 3 generates pulses whose frequency is many times greater than the inverter output frequency and determines the degree of stepped approximation with uniform time quantization of the sine wave of the control voltage generated by block 4, the smooth component of which is shown in Fig. 2c. Frequency divider 5 reduces the clock frequency to a frequency that is twice as large (on the second output) and four times (on the first output) higher than the output frequency of the inverter. The signal of block 4 is fed to the negative input of the adder 1, to the plus input of which comes the reduced feedback voltage of the switchgear, matched in level with the voltage of the control system through the transfer coefficient k. The output voltage U of the adder 1 is shown in dots in Fig. 2d. On the first quarter of each half-period (interval O- / 2 in FIG. 2) the output

0

0 5

0 5 5

0

The signal of the adder 1 through the dip key 7 is fed to the input of the integrator 8 and thereby directly determines the form of its output voltage Us, which is shown in Fig. 2 by dotted lines.

The closest form to the linear voltage of the integrator 8 Us is fed to the inputs of threshold devices 10 and 11, the tripping voltages of which are indicated in Fig. 2d as Unopio and Unopn- At the moments when the signal of the integrator 8 Ue is equal to the mentioned Unop and Unopn voltages The devices 10 and 11 produce command signals (impulses) for switching the half-bridge inverter valves, which are via a disjunctor. 12 are alternately fed to the inlet of the distributor 13, implemented on the basis of the simplest trigger link and alternately switching on the two main valves of the half bridge circuit. The form of the output voltage of the inverter in this case corresponds to the signal K o UBUX (Fig. 2d).

In the second half of each half-period of the output curve (interval l / 2- in Fig. 2), the device operation algorithm is somewhat modified. The next clock pulse generated at the time / 2 from the first output, the frequency divider 5 changes the state of the counting flip-flop 9, the output voltage Ug of which is shown in Fig. 26. The signal Ug arrives at the control circuit of the electronic two-position key 7 and causes it to switch. In this case, the output of the adder 1 is connected to the integrator 8 via the logical inverter 6, the output of which is indicated in Fig. 2g as Ue, so that at time I, as shown in Fig. 2g, the output voltage of the integrator 8 Ug starts changing in the opposite direction. The additional symmetry in the process of forming the output curve is introduced by clock pulses from the first output of the frequency divider 5 through disjunctor 12 to the input of the distributor 13 and at the beginning of each half period. The curve of the formed inverter output voltage is characterized by an increased degree of symmetry (symmetry of the third kind relative to the beginning of the ordinates), in the spectrum of the output signal of the inverter throughout the control range there are practically no even harmonics, as well as subharmonics and combination harmonics. The pulse duration of the output voltage curve increases sequentially as it approaches the middle of the half period, which also improves the quality of the output energy of the converter.

Thus, the inclusion in the scheme of the device of the simplest additional nodes: a frequency divider, a trigger, a two-position electronic key and a logic inverter, implemented on the basis of the simplest typical electronic circuits, including the basic version, allows to significantly improve the harmonic composition of the output voltage half bridge inverters.

Claims (1)

Invention Formula A device for controlling an autonomous voltage inverter with tracking, containing an adder, to the minus input of which is connected the main output of the control source, its voltage, the integrator connected to the two threshold nodes, and the distributor, in order to improve the harmonic content the inverter's output voltage, it is supplied with A frequency output with two outputs, a counting trigger, a two-position switch, a logic inverter, a disjunctor, and the control voltage source is made of series-connected clock generator and a step-sinusoidal control signal shaping unit, which is the main output of the control voltage source, the input of the frequency divider is connected to the clock pulse generator, the first output of the frequency divider is connected to the counting trigger, the second is connected to the disjunctor, the output of the adder is connected to the first terminal of the two-position key is directly, and the second terminal is through the logical inverter, the common terminal of the key is connected to the integrator, and the control circuit of the key is connected to the counting trigger. FIG. 2