RU116288U1 - AUTONOMOUS LOW FREQUENCY INVERTER - Google Patents

Abstract

The utility model relates to electrical engineering, in particular, to the field of converter technology. The technical result of an autonomous low-frequency inverter is to simplify the circuit of a single-phase bridge voltage inverter and control system. In the device, a single-phase bridge voltage inverter contains two reverse diodes, a sawtooth voltage generator, a comparator, a pulse distributor are introduced into the control system, a timer is inserted into each of the power switch control channels, the output of which is connected to the input of the first pulse shaper, and the outputs of the antiphase clock pulse source are connected with inputs of a sawtooth voltage generator, pulse distributor and timers in each power switch control channel of a single-phase bridge inverter voltage rotor, the output of the sawtooth voltage generator is connected to the first input of the comparator, and its second input to the output of the governing body. 1 n.p., 2 z.p. f-ly.

Description

The utility model relates to electrical engineering, in particular, to the field of converter technology.

Known single-phase bridge autonomous voltage inverter (AIN), made on the basis of dual-operation lockable thyristors with pulse-width regulation and a DC link, made on a rectifier with a capacitor filter (Rudenko BC, Senko V.I., Chizhenko I.M. technology ”. / M .: Higher School, 1980, p.237-240). Conversion of direct voltage to alternating current for supplying an active-inductive load of a given frequency occurs by switching diagonally arranged pairs of thyristor switches with pulses offset by 180 electrical degrees. When switching the keys, the electromagnetic energy of the load through the return diodes is discharged into the capacitor bank of the DC voltage source. The capacity of the capacitor bank C reaches a large value, especially at low frequencies f and high currents AIN:

,

Where:

I is the load current;

t≡1 / f is the current flow time through the capacitor bank;

ΔU is the permissible value of the overvoltage on the capacitors.

At a current of several hundred amperes and low frequencies f (less than 5 Hz), the capacitance of a capacitor bank can reach large values, which is the main disadvantage of this device.

The closest in technical essence to the claimed solution and taken as a prototype is an autonomous low-frequency inverter with an active-inductive load, with a transistor power unit and a two-channel control system (RU 98650 U1 with priority dated 05/24/2010, published on 10/20/2010, Bull. No. 29 )

The power part of the prototype AIN with an active-inductive load is a single-phase bridge inverter, consisting of a rectifier and power transistor switches with four reverse diodes. The inverter power keys are controlled from a two-channel control system with identical control channels. Each control channel has control pulse shapers and containing drivers (devices for controlling power switches).

The inverter output voltage is controlled by changing the duration τ _{2 of the} on state of the power switches and, which is determined by the pulse shapers in the control channels and in the function of the control signal U _{p of the} control body. A complicated scheme of a single-phase bridge voltage inverter and control system, where in each power switch control channel the pulse shapers contain phase-shifting devices, leads to asymmetry of the control pulses arriving at the power switches, which negatively affects the quality of the inverter output voltage, increases the power loss in the load, complicates the regulatory system, and as a result reduces the reliability and efficiency in general.

The technical result of the claimed device is a simplification of the circuit of a single-phase bridge voltage inverter and control system.

The technical result is achieved by the fact that in an autonomous low-frequency inverter containing a single-phase bridge voltage inverter, made on the basis of a rectifier, power switches and reverse diodes, an active-inductive load and a control system with a source of antiphase clock pulses with a frequency f identical to the control channels of the power switches, each of which contains a pair of control pulse shapers connected to control circuits of power switches, a governing body, a single-phase bridge inverter e.g. The line contains two reverse diodes, a sawtooth voltage generator, a comparator, a pulse distributor are introduced into the control system, a timer is introduced into each of the power switch control channels, the output of which is connected to the input of the first pulse shaper, and the outputs of the antiphase clock pulse source are connected to the inputs of the sawtooth voltage generator , a pulse distributor and timers in each power switch control channel, the output of the sawtooth voltage generator is connected to the first input of the compar ator, and its second entrance with the exit of the governing body. The sawtooth generator is made with a frequency of 2f. The pulse distributor contains, for example, two keys whose outputs are connected to the inputs of the second control pulse shapers of both power key control channels.

Due to the fact that a sawtooth voltage generator, a comparator, a pulse distributor are introduced into the control system, and a timer is entered into each of the power switch control channels, only two reverse diodes are contained in a single-phase bridge voltage inverter, instead of four a single-phase bridge inverter circuit is simplified compared to the prototype voltage and control systems. The device eliminates the occurrence of asymmetry of the control pulses supplied to the power switches, the quality of the inverter output voltage increases, the power loss in the load decreases, and as a result, the reliability and efficiency in general are increased.

Figure 1 shows a diagram of a prototype, figure 2 - shows a diagram of the proposed device, figure 3 - shows a diagram of the source of antiphase clock pulses, figure 4 - diagram of the operation of the proposed device. The following notation is used in the figures:

1 - single-phase bridge voltage inverter;

2 - rectifier;

3, 5 - power switches made on thyristors;

4, 6 - power switches made on transistors (transistors);

7, 8 - reverse diodes;

9 - active-inductive load (u, i - voltage and current in the load);

10 - control system;

11 is a source of antiphase clock pulses with a frequency f and two outputs " a " and "x" (source 11 can be performed, for example, based on a generator 26 and two comparators 27 and 28);

12, 13 - control channels for power keys of a single-phase bridge inverter;

14 - first pulse shapers;

15 - second pulse shapers;

16 - governing body;

17 - a sawtooth voltage generator with a frequency of the output signal 2f, made, for example, on the elements 21 ... 23;

18 - a comparator;

19 - pulse distributor, consisting, for example, of two keys 24 and 25;

20 - governing body;

21 - amplifier;

22 - key "reset" (for zeroing the capacitor in the integrator 23);

23 - integrator;

24, 25 - control keys;

26 - a sinusoidal voltage generator with a frequency f;

27, 28 — comparators;

U _and - the voltage of the pulses "reset" at the output 21;

U _p - sawtooth voltage at the output 23;

U _y - control voltage at the output 20;

U _p is the voltage at the input 20;

U _cm is the bias voltage at input 21.

U ₁ , U ₂ , a , x, U _and , U _p , U _y - signals;

FI1 - 14, FI2-15 - the corresponding pulse shapers 1 and 2 in the control channel 12, their digital designations 14 and 15;

FI1 - 14, FI2 - 15 - the same, but in the control channel 13;

τ ₁ , τ ₂ - pulse duration, respectively, at the outputs of blocks 14, 15 in the control channels 12 and 13;

τ ₁ (3), τ ₁ (5) - the duration of the control pulses on thyristors 3 and 5;

τ ₂ (4), τ ₂ (6) - the same on transistors 4 and 6;

t ₁ - rise and fall times to zero load current i;

Δt - pulse time "reset" U _and ;

U _d is the voltage at the output of rectifier 2;

u, i - respectively, the voltage and current in the load 9.

The device contains a single-phase bridge voltage inverter 1, which includes a rectifier 2, power switches 3 ... 6, made on thyristors 3 and 5, transistors 4 and 6, two reverse diodes 7, 8, active inductive load 9, control system 10, consisting of a source of antiphase clock pulses 11 with a frequency f, two identical control channels for power switches 12, 13, a sawtooth voltage generator 17, a comparator 18, a pulse distributor 19, a control body 10. Each of the control channels for power keys 12, 13 contains a time p 20, the output of which is connected to the input of the first pulse shaper 14, and the outputs of the source of the out-of-phase clock pulses 11 are connected to the inputs of the sawtooth voltage generator 17, the pulse distributor 19 and timers 20 in each channel for controlling the power keys of a single-phase bridge voltage inverter 12, 13, the output of the generator sawtooth voltage 17 is connected to the first input of the comparator 18, and its second input with the output of the governing body 16.

The operation of the claimed device

At the outputs " a " and "x" of the clock source 11, two antiphase sequences of pulses are formed with a given frequency f, which, with the help of a sawtooth voltage generator 17, is converted into a sawtooth voltage U _p with a frequency of 2f. The sawtooth voltage generator contains an amplifier 21, a “reset” key 22, and an integrator 23. This process is reflected in the four upper diagrams in FIG. 3, where U ₁ and U ₂ are the voltages at the outputs “ a ” and “x” of the antiphase clock pulse source 11. impulse voltage U _and is formed on the output of the amplifier 21 and supplied to the key 22, a short time (during Δt) shunt capacitor integrator 23, performing "reset""saw" from maximum to zero twice per period T = 1 / f. The signal U _p from the output 23 is fed to the first input of the comparator 18, and the signal U _y from the output 16 is supplied to its second input. As a result of comparing these signals, the signal U ₃ (Fig. 3d) with a frequency of 2f occurs, which, passing through the keys 24, 25 at the inputs of the pulse shapers FI2 (15) in the control channels of the power switches 12, 13, it turns into two antiphase signals U ₄ and U ₅ with a duration of τ ₂ and a frequency f (Fig. 3e and Fig. 3g). In this case, the timers 16 in blocks 12, 13 receive signals U ₁ and U ₂ with a frequency f (figa and figb). As a result, at the outputs of each of the control channels of the power switches 12 and 13, two sequences of pulses of different durations τ ₁ and τ ₂ occur (FIGS. 3z, 3l). In this case, τ ₁ is selected from the condition of reliable unlocking of thyristors 3, 5 taking into account the electromagnetic inertia of the active-inductive load 9. Over time τ _{1, the} current in the thyristor should increase to a value higher than the holding current. The duration τ _{2 is} determined by the signal U _y (points N ₁ and N ₂ in Fig. 3d) and determines the output voltage at load 9 (Fig. 3m).

In each control channel of the power switches 12, 13, the leading edges of the control pulses from the outputs of the pulse shapers 14 and 15 coincide. The current i drops through the included thyristor, for example, 3, and diode 8 (or thyristor 5 and diode 7) during the time t ₁ (Fig.3m), which is determined by the electromagnetic time constant of the load circuit T _e and is equal to

t ₁ ≈4T _e = 4L / R.

The condition for safe operation of the AIN, excluding the emergency mode of a short circuit on the circuit of thyristor 3 and transistor 4 (or 5 and 6), has the form:

τ ₂ + t ₁ <0.5T, where T = 1 / f.

The operation of the valves is given in Fig.3n.

The effective value of the voltage at the active inductive load 9 is determined by the formula:

where τ ₂ is the adjustable duration in seconds, f is the frequency in hertz.

The value of τ ₂ depends on the value of the control voltage U _y

where U _p.m - the maximum voltage of the "saw".

The maximum value of τ _2max = (0.5 / f + t ₁ ), which ensures the exclusion of emergency _{operation of the} AIN, is established by the limitation of the signal U _{уmax of the} governing body 16. Combining formulas (1) and (2), we finally have:

Where is the relative magnitude of the control voltage.

So, with , which is obvious from fig.3m.

It should be noted that the source of clock pulses 11 can be performed, for example, on the basis of a sinusoidal oscillation generator 26 and two comparators 27, 28. Due to a certain threshold of operation of the comparators at the outputs " a ", "x" we have pulses in accordance with figure 3 .

Thus, due to the fact that a sawtooth voltage generator, a comparator, a pulse distributor are introduced into the control system, and a timer is entered into each of the power switch control channels, only two reverse diodes are contained in a single-phase bridge voltage inverter, instead of four, the circuit is simplified compared to the prototype single-phase bridge voltage inverter and control system. The device eliminates the occurrence of asymmetry of the control pulses supplied to the power switches, the quality of the inverter output voltage increases, the power loss in the load decreases, and as a result, the reliability and efficiency in general are increased.

Claims (3)

1. Autonomous low-frequency inverter containing a single-phase bridge voltage inverter, made on the basis of a rectifier, power switches and reverse diodes, an active inductive load and a control system with a source of out-of-phase clock pulses with a frequency f, identical control channels for power switches of a single-phase bridge voltage inverter, each of which contains shapers of control pulses connected to control circuits of power switches, a control body, characterized in that the single-phase bridges The first voltage inverter contains two reverse diodes, a sawtooth voltage generator, a comparator, a pulse distributor are introduced into the control system, a timer is introduced into each of the power switch control channels, the output of which is connected to the input of the first pulse shaper, and the outputs of the antiphase clock pulse source are connected to the generator inputs sawtooth voltages, pulse distributor and timers in each power switch control channel of a single-phase bridge voltage inverter, output generator A wave of sawtooth voltages is connected to the first input of the comparator, and its second input to the output of the governing body. 2. Autonomous low-frequency inverter according to claim 1, characterized in that the sawtooth voltage generator is made with a frequency of 2f. 3. The autonomous low-frequency inverter according to claim 1, characterized in that the pulse distributor contains, for example, two keys, the outputs of which are connected to the inputs of the second control pulse shapers of both power channel control keys of a single-phase bridge voltage inverter.