RU2581033C1 - Single-phase voltage inverter - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention relates to electrical engineering, particularly to single-phase voltage inverters. Single-phase voltage inverter comprises control system, a transistor half-bridge, additional two transistors, two diodes, two throttles and two capacitors, which enables to realise a change of frequency, phase and level of current value of output voltage both below and above level determined by voltage of primary source of DC voltage.

EFFECT: technical result is improved weight and dimensions and characteristics of energy converter with stabilisation of output voltage.

2 cl, 2 dwg

Description

The proposal relates to the field of electrical engineering and power electronics, in particular to converters of electrical energy from DC voltage to AC voltage (inverters), and can be used in stand-alone power supply systems to stabilize the output AC voltage, or change it according to a given law.

A device for a single-phase bridge autonomous voltage inverter [patent RU 2421870, class H02M 7/53846, issue date 06/20/2011], comprising a bridge converter made on four diodes and four transistors, an active-inductive load and a control system. The presented device implements the conversion of DC voltage into a single-phase AC voltage. A disadvantage of the known device is the inability to increase the voltage at the inverter output above the voltage level determined by the voltage level of the DC source. A device for converting a direct voltage to a three-phase alternating current [patent SU 944027, class H02M 7/48, issuance date 07/15/1982], comprising a single-phase inverter, loaded on the primary winding of a matching transformer, the secondary windings of which are switched through electronic switches to three output phases. A voltage inverter device is also known [certificate for utility model No. 16888, class H02M 7/48], containing two single-phase inverter bridges, a transformer, diodes connected in parallel to the emitter-collector junctions of the transistors, and an inverter input capacitor. The disadvantages of the known schemes are the presence of a matching transformer and, as a consequence, a fixed frequency of the output voltage, as well as a large mass and dimensions.

The closest in technical essence is the device of the DC voltage Converter with an intermediate link of high frequency [patent RU 2414802, class H02M 7/539, date of issue 03/20/2011], which allows to improve overall dimensions. The task is achieved in that the voltage converter contains an intermediate link of increased frequency, consisting of a single-phase inverter bridge and a high-frequency transformer, the output of which is equipped with a thyristor switch and a filter. The disadvantage of the proposed device is a complex circuit containing a filter matching a transformer and a large number of semiconductor elements, as well as low quality output voltage. The disadvantages of the known electrical Converter can also include a large number of conversions of electricity, and therefore, low efficiency.

The proposed single-phase voltage inverter allows you to change the current value, frequency and phase of the output voltage, as well as improve weight and size and energy characteristics. Moreover, it becomes possible to change the level of the output voltage both below and above the level determined by the voltage of the constant voltage source, while the frequency of the output voltage can vary over a wide range.

The described advantages are achieved in that the single-phase voltage inverter is equipped with additional elements that make it possible to obtain an adjustable two-level source of constant voltage, and a transistor half-bridge that implements a voltage inverter. By changing the duty cycle of the controlled keys, it is possible to change according to a given algorithm or stabilize the level of the output voltage relative to the voltage level of the constant voltage source.

A single-phase voltage inverter, the circuit of which is shown in FIG. 1, contains conclusions 1, 2 for connecting a constant voltage source 3, load 4, control system 5, transistor half-bridge 6, consisting of two transistors 7, 8 and two antiparallel diodes connected to them 9, 10. Positive terminal 1 for connecting a constant voltage source 3 is connected to the collector of the first transistor 7 and the cathode of the first diode 9, the emitter of the first transistor 7 is connected to the anode of the first diode 9 and the collector of the second transistor 8 and the cathode of the second diode 10. The emitter of the second transistor 8 is connected to the anode of the second diode a 10. A single-phase voltage inverter contains an additional transistor 11, a diode 12, a choke 13 and a capacitor 14. A collector of the third transistor 11 is connected to the positive terminal 1 of the DC voltage source 3, the emitter of which is connected to the cathode of the third diode 12 and the first terminal of the first choke 13. The anode of the third diode 12 is connected to the negative lining of the first capacitor 14 and the emitter of the second transistor 8, the negative terminal 2 of the DC voltage source 3 is connected to the first terminal 15 of the load 4, the output terminal of the first inductor 13 and the positive lining of the first capacitor 14. The second terminal 16 of the load 4 is connected to the emitter of the first transistor 7. Information about the voltage levels at the constant voltage source 3 and the capacitor 14 are fed to the control system 5, into which the control leads of all transistors 7 are connected , 8, 11.

A single-phase voltage inverter, the circuit of which is shown in FIG. 2, contains additional transistor 17, diode 18, inductor 19 and capacitor 20 included in the connection circuit between the positive terminal 1 of the DC voltage source 3 and the collector of the first transistor 7. The first terminal of the second inductor 19 is connected to the positive terminal 1 of the DC voltage source 3 and the collector of the third transistor 11. The second output of the second inductor 19 is connected to the collector of the fourth transistor 17 and the anode of the fourth diode 18, the cathode of which is connected to the positive lining of the second cond the sensor 20 and the collector of the first transistor 7. An emitter of the fourth transistor 17 and a negative lining of the second capacitor 20 are connected to the negative terminal 2 of the DC voltage source 3 and the voltage level information from the second capacitor 20 is connected to the control system 5, to which the control terminals of the fourth transistor 17.

The operation of the single-phase voltage inverter shown in FIG. 1 occurs as follows. In the operating mode, the required voltage value is generated on the first capacitor 14 by changing the duty cycle of the transistor 11

γ ₁₁ = t ₁₁ / T;

the voltage on the capacitor 14 is determined according to (in the case of a subsequent discharge of the capacitor 14 to the load 4)

, $$U_{\mathrm{fourteen}}={\mathrm{<figure-callout\; id="3"\; label="U"\; filenames="00000004.png,00000005.png"\; state="\{\{state\}\}">U</figure-callout>}}_3\cdot \frac{{\gamma }_{\mathrm{eleven}}}{\mathrm{one}-{\gamma }_{\mathrm{eleven}}}$$

,

where γ ₁₁ is the duty cycle of the transistor 11, t ₁₁ is the closed time of the transistor 11, T is the pulse repetition period, U ₁₄ is the required voltage level across the capacitor 14, U ₃ is the voltage level of the constant voltage source 3.

At that time, when the transistor 11 is turned on, energy is accumulated in the inductor 13. The charge current flows along the plus circuit of the constant voltage source 3 through the transistor 11, the inductor 13 and to the minus of the constant voltage source 3. In this case, the current through the inductor 13 grows according to a linear law. After closing the transistor 11, the energy stored in the inductor 13 is transferred to the charge of the capacitor 14 through the circuit to the second output of the inductor 13, the positive lining of the capacitor 14, the negative lining of the capacitor 14, the diode 12 and the first output of the inductor 13. As a result, the energy is transferred from the inductor 13 on the charge of the capacitor 14, which is then discharged to the load using a transistor 8. Moreover, with γ ₁₁ <0.5, the circuit operates with a decrease in the voltage level on the capacitor 14 relative to the input voltage of the constant voltage source 3, with γ ₁₁ > 0.5 - with an increase, and with γ ₁₁ = 0.5, the voltage level a capacitor 14 and a level at a constant voltage source 3. In this embodiment, the circuit of FIG. 1 it is most rational to ensure the duty cycle of the transistor 11 γ ₁₁ = 0.5, while we will have a bipolar voltage source with equal voltage levels.

Thus, a bipolar DC voltage source is organized, one level is the voltage at the constant voltage source 3, the second level is the voltage at the capacitor 14. Transistors 7, 8 and diodes 9, 10 organize a transistor half-bridge 6 and a voltage inverter circuit to power the load 4. By changing the order and duty cycle of the transistors 7 and 8, it is possible to change the effective value, frequency and phase of the output voltage supplying the load 4. By the algorithm of the transistors 7 and 8, it is possible to achieve the implementation of the control law I output voltage at the load according to the law of unipolar or bipolar PWM. In this case, the simultaneous on state of both transistors 7 and 8 should be excluded. Thus, the elements of the circuit 3, 11, 13, 12, 14 are responsible for the organization of the bipolar power source, and the elements of the circuit 7, 8, 9, 10 are responsible for the conversion of the bipolar DC voltage to AC voltage with the required parameters of the effective value, frequency and phase.

In the event that it is necessary to obtain the effective voltage at the load 4 above the voltage level determined by the voltage level of the constant voltage source 3, it is necessary to use the circuit of the single-phase voltage inverter shown in FIG. 2. Operation of the single-phase voltage inverter shown in FIG. 2 occurs as follows. In the operating mode, the required voltage values are generated on the first 14 and second 20 capacitors by changing the duty cycle of the transistors 11 and 17, respectively. The duty cycle of the transistor 17 is determined according to

γ ₁₇ = t ₁₇ / T;

the voltage on the capacitor 20 is determined according to (in the case of a subsequent discharge of the capacitor 20 to the load 4)

, $$U_{\mathrm{twenty}}={\mathrm{<figure-callout\; id="3"\; label="U"\; filenames="00000004.png,00000005.png"\; state="\{\{state\}\}">U</figure-callout>}}_3\cdot \frac{\mathrm{one}}{\mathrm{one}-{\mathrm{<figure-callout\; id="17"\; label="\gamma "\; filenames="00000005.png"\; state="\{\{state\}\}">\gamma </figure-callout>}}_{17}}$$

,

where γ ₁₇ is the duty cycle of the transistor 17, t ₁₇ is the closed time of the switch 17, T is the pulse repetition period, U ₂₀ is the required voltage level on the capacitor 20, U ₃ is the voltage level of the constant voltage source 3.

At that moment in time, when the transistor 17 is turned on, energy is accumulated in the inductor 19. The charge current flows along the plus circuit of the constant voltage source 3 through the inductor 19, the transistor 17 and to the minus of the constant voltage source 3. In this case, the current through the inductor 19 is increasing according to a linear law. After the transistor 17 is closed, the voltage drop across the inductor 19 is added to the voltage of the constant voltage source 3 and the energy stored in the inductor 19 and the energy of the constant voltage source 3 are transferred to the charge of the capacitor 20 along the plus circuit of the constant voltage source 3, inductor 19, diode 18, the positive lining of the capacitor 20, the negative lining of the capacitor 20 and the minus of the DC voltage source 3.

Moreover, when γ ₁₇ > 0, the circuit operates with increasing voltage level on the capacitor 20 relative to the input voltage of the constant voltage source 3. To obtain a symmetrical sinusoidal voltage at the output of a single-phase duty cycle inverter, the operation of the transistors γ ₁₁ and γ ₁₇ must be such that on the capacitors 14 and 20, a bipolar voltage source with equal levels was arranged. Elements of the circuit 3, 11, 13, 12, 14, 17, 18, 19, 20 are responsible for the organization of the bipolar power source, and elements of the circuit 7, 8, 9, 10 are responsible for converting the bipolar DC voltage to alternating voltage with the required parameters of the effective value , frequencies and phases.

Thus, the proposed device single-phase voltage inverter allows you to change the frequency, phase, and also the level of the effective value of the output voltage both below and above the level determined by the voltage of the primary source of constant voltage. A single-phase voltage inverter, in comparison with known schemes, allows to improve weight and size and energy characteristics.

Claims (2)

1. A single-phase voltage inverter containing terminals for connecting a constant voltage source, a load, a control system, a half-bridge transistor consisting of two transistors and two anti-parallel diodes connected to them, the positive terminal of a constant voltage source being connected to the collector of the first transistor and the cathode of the first diode , the emitter of the first transistor is connected to the anode of the first diode and the collector of the second transistor and the cathode of the second diode, the emitter of the second transistor is connected to a a second diode node, characterized in that the single-phase voltage inverter contains an additional transistor, diode, inductor and capacitor, and the collector of the third transistor, the emitter of which is connected to the cathode of the third diode and the first output of the first inductor, the anode of the third diode, is connected to the positive terminal of the DC voltage source connected to the negative lining of the first capacitor and the emitter of the second transistor, the negative terminal of the DC voltage source is connected to the first load terminal, a second terminal of the first inductor and the positive plate of the first capacitor, the second terminal of the load connected to the emitter of the first transistor, the voltage levels of the information on the source of DC voltage and the capacitor is supplied to the control system, which manages all control terminals of transistors. 2. The single-phase voltage inverter according to claim 1, characterized in that the circuit contains additional transistor, diode, inductor and capacitor included in the connection circuit between the positive terminal of the DC voltage source and the collector of the first transistor, the first terminal of the second inductor connected to the positive terminal connecting the DC voltage source and the collector of the third transistor, the second terminal of the second inductor is connected to the collector of the fourth transistor and the anode of the fourth diode, the cathode of which It is connected to the positive side of the second capacitor and the collector of the first transistor, and the emitter of the fourth transistor and the negative side of the second capacitor are connected to the negative terminal of the DC voltage source, and information about the voltage level from the second capacitor is connected to the control system to which the control terminals of the fourth transistor are connected .

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