RU15822U1 - SINGLE-PHASE DC CONVERTER TO VARIABLE THREE-STAGE QUASI-SINUSOIDAL - Google Patents

Abstract

A single-phase converter of direct voltage to alternating three-stage quasi-sinusoidal, containing a bridge voltage inverter, the input of which is connected in series with two power sources connected in series, characterized in that each of the sources is connected through a transistor connected in series with the power source and a diode connected in parallel to non-conductive direction to the circuit containing the power source and the transistor, while the branch of the series-connected diodes is shunted condensers.

Description

SINGLE-PHASE CONSTANT CONSTANT

VOLTAGES IN A VARIABLE THREE-STAGE

Quasisinusoidal

The utility model relates to the field of converter technology and can be used in power supply systems, which are subject to increased requirements regarding the coefficient of non-linear distortion of the output voltage.

A known power circuit of a DC-to-AC converter three-stage 1, where the approximation of a sinusoidal output voltage occurs by switching the solder in the output transformer. The disadvantage of this device is the presence of the output transformer unit, as well as the inability of the circuit to operate on an active inductive load.

Also known is a single-phase converter 2, the output of which is formed by an alternating three-stage voltage, however, this device has the following disadvantages:

- a large number of power sources (three sources);

-the presence of a transformer block at the output;

- the absence of channels for returning the reactive power of the load to the power supply circuit, which will negatively affect the operation of circuit elements.

Closest to the proposed device is a single-phase inverter with switching sections of the power source 3, containing an inverter bridge, to the input of which are connected two series-connected power sources, each of which is shunted by a capacitor, and the common zero point of the power sources is connected to both shoulders of the inverter bridge using two branches, each of which contains a key with two-sided conductivity. The harmonic distortion coefficient of the output voltage of this device is 15%.

The disadvantage of this converter is that during the physical implementation of the above-mentioned keys with two-sided conductivity, four transistors will be required. Thus, the converter will contain a total of eight transistors. In addition, two shunt capacitors at the input will be required.

The objective of the claimed utility model is to simplify the converter circuit - reducing the number of elements during its implementation while maintaining the quality of the output voltage.

The solution to this problem is achieved by the fact that in the circuit of a single-phase converter of direct voltage to an alternating three-stage quasi-sinusoidal, containing a bridge voltage inverter with two series connected to its input

IPC N 02 M 7/48

connected by power sources, transistors and diodes are introduced, moreover, a transistor is connected to the circuit of each of the power sources and connected to it in series, and the diode is connected in parallel in a non-conductive direction to the circuit consisting of a power source and a transistor, while a branch of series-connected diodes is shunted by a capacitor .

The technical solution is illustrated by drawings - in FIG. 1 shows the power circuit of the converter, and figure 2 is a curve of the output voltage and the control algorithm of the valves of the circuit.

The proposed device comprises a main power source 1, a transistor 2 and a diode 3 connected in parallel to it, connected in parallel in a non-conductive direction to the circuit, which comprises a power source 1 and a transistor 2. In addition, the converter contains an additional power source 4, connected in series with a power source 1 The power supply 4 with a transistor 5 connected in series with it forms a circuit parallel to which a diode 6 is connected in a non-conductive direction. The bridge circuit includes a bridge second voltage inverter comprising transistors chetfe 7-10, four freewheeling diodes 11-14 and the active inductive load 15 connected to the inverter bridge diagonal. To the input of the inverter bridge, power supplies 1 and 4 and a capacitor 16 are connected, which shunts the branch from the series-connected diodes 3 and 6.

The functioning of the proposed device is as follows (figure 2):

1) in the interval About wt wt t / b, only the additional power supply 4 is working on the load (transistor 5 is open), the main power supply 1 is turned off (transistor 2 is locked). The output voltage has a positive polarity (open transistors 7 and 10 of the inverter bridge);

2) on the interval to the load 15 only the main power source 1 works (transistor 2 is open). Additional power supply 4 is turned off (transistor 5 is locked). Conduct transistors 7 and 10 of the inverter bridge - the output voltage has a positive polarity;

3) in the interval 7t / 3 wt 27i / 3, load 15 operates both the main power supply 1 and the additional power supply 4 (transistors 2 and 5 are open). Spend transistors 7 and 10 of the inverter bridge;

4) on the interval 271/3 wt 57c / 6, the operation algorithm of the transistors is the same as in paragraph 2);

5) on the interval 57i / 6 wt, the transistors of the circuit operate as well as in paragraph 1).

output voltage (instead of transistors 7 and 10 conduct transistors 8 and 9 of the inverter bridge).

The optimal shape of the output voltage curve of the converter in the sense of the minimum of the coefficient of nonlinear distortion is shown in Fig. 2, the transistor control algorithm is indicated there, which are indicated by the numbers 2, 5, 7-10. To suppress higher harmonics, the following conditions must be met:

(l + V3)

at given angles of engagement - O, l / b and l / 3, where E is the voltage of the main power source 1, and dU is the voltage of the additional power source 4.

For a single-phase bridge voltage inverter 4 circuit, the harmonic distortion factor is 30%. In this case, the output voltage contains higher harmonics with numbers:

 ± 1, meN,, 7, ...

The harmonic composition (the content of higher harmonics in% of the main) of the output voltage of a single-phase bridge inverter is presented in table 1:

(1)

(2)

Table 1

For the claimed Converter circuit using the optimal choice of the relations between dU and E (expression (1)), the coefficient of non-linear distortion of the output voltage is reduced to 15%, while it contains the higher harmonics with numbers:

 l, meN ,, 13, ...

Therefore, the proposed device provides suppression of higher harmonics with numbers:

(2-m- 1) ± l, meN

The harmonic composition of the output voltage of the inventive converter is presented in table2 (for control angles 0, l / 6.7s / 3):

(3)

(4)

table 2

the proposed device allows to reduce the coefficient of nonlinear distortion of the output voltage to 11.3% if the control angles are taken equal to 71/18, Zl / 18, 5: 1/18, and the voltage of the power sources is set equal to:

.,.

- where Umax is the voltage amplitude at the load. In this case, the output voltage curve contains harmonics with numbers satisfying equation (2) and has a zero step from O to l / 18. The operation algorithm of the transistors of the circuit will differ from the algorithm shown in figure 2 in that the transistors 7 and 10 are open from 7T / 18 to 1771/18, the transistors 8 and 9 are open from 1971/18 to 357C / 18, the transistor 2 conducts at intervals n / 6 - 5ya / 6 and 7k / b - k / 6, transistor 5 conducts at intervals of 7g / 18 - n / 6, 5l / 18 - 13l / 18, 5l / 6 17L / 18, 19L / 18 - 7l / 6, 23L / 18 - 31l / 18, 11l / 6 - 35l / 18.

The harmonic composition of the output voltage for this case is presented in table 3:

Thus, the technical effect of using the proposed device is that the inventive converter does not require an output transformer and provides the ability to operate in a wide adjustable frequency range for an active inductive load with a quasi-sinusoidal three-stage output voltage. In addition, unlike the prototype, the proposed device contains a smaller number of controlled gates - not eight transistors, but six, as well as a smaller number of shunt capacitors at the input - not two capacitors, but one.

(5)

Table 3

List of sources used:

1. Rozanov Yu. K. Fundamentals of power converting equipment. M: Energy, 1979, p. 241-242.

2. Lipkovsky K.A. et al. DC-DC converter into a multi-stage variable. // USSR AS No. 944 025 class. H 02 M 7/48.

3.Moyin B.C. Stabilized transistor converters. M: Energoatomizdat, 1986.P.311-312.

4. Chizhenko I. M. et al. Handbook of transformative technology. Kiev: Technique, 1978, p. 128-131.

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/ Wv First Vice-Rector of the СГТ Professor: Authors:

, v, -. i- - (/ 0 I Atoyan V.R. Golembiovsky Yu.M. Kodtsaev R.V.

Claims (1)

A single-phase converter of direct voltage to alternating three-stage quasi-sinusoidal, containing a bridge voltage inverter, the input of which is connected in series with two power sources connected in series, characterized in that each of the sources is connected through a transistor connected in series with the power source and a diode connected in parallel to non-conductive direction to the circuit containing the power source and the transistor, while the branch of the series-connected diodes is shunted condensers.