JP7455050B2 - self-excited converter - Google Patents

Description

Embodiments of the invention relate to self-commutated converters. More specifically, the present invention relates to a self-excited converter for ozonizers.

A self-excited converter for an ozonizer is known that generates ozone in the ozonizer by supplying high-frequency, high-voltage AC power between a pair of electrodes of the ozonizer and generating silent discharge between the pair of electrodes.

Ozonizers are capacitive loads. Therefore, in self-commutated converters for ozonizers, the output voltage of the inverter is boosted to a high voltage using a high-frequency transformer, and the ozonizer and resonant reactor resonate to generate high-frequency high voltage. . In this case, a gate pulse corresponding to the resonant frequency of the load is input to the gate of the inverter.

However, ozonizer constants such as capacitive impedance vary from ozonizer to ozonizer. Therefore, in the method of generating high frequency and high voltage as described above, it is necessary to design a high frequency transformer and a resonant reactor each time according to the ozonizer constant, which increases design costs and increases lead time. There is a possibility that it will become.

Therefore, in a self-commutated converter for an ozonizer, it is desirable to be able to supply high-frequency, high-voltage AC power to the ozonizer without being affected by the constant of the ozonizer.

Patent No. 3540227 Patent No. 4228524 Patent No. 6068667

Embodiments of the present invention provide a self-commutated converter that can supply high frequency, high voltage AC power to an ozonizer without being affected by the constant of the ozonizer.

According to an embodiment of the present invention, there is provided a self-excited converter for an ozonizer that supplies alternating current power between a pair of electrodes of an ozonizer, which converts power supplied from a power source into alternating current ozonizer power compatible with the ozonizer. and a main circuit unit that supplies power for the ozonizer to the ozonizer, and a control unit that controls power conversion operation by the main circuit unit, and the main circuit unit is configured to supply the power supplied from the power supply to the ozonizer. has a plurality of conversion circuits that convert the AC power into AC power, the plurality of conversion circuits have a pair of AC output terminals that output the AC power, and the pair of AC output terminals of the plurality of conversion circuits: They are connected in series, and the main circuit section generates the ozonizer power by the sum of the AC power of the plurality of conversion circuits and supplies it to the ozonizer , and the plurality of conversion circuits It is possible to switch between a first state in which the voltage between the output terminals is set to a first voltage and a second state in which the voltage between the pair of AC output terminals is set to a second voltage higher than the first voltage. , the control unit switches the first state and the second state of the plurality of conversion circuits at the operating frequency of the ozonizer, and when the number of the plurality of conversion circuits is n, the control unit switches the first state and the second state of the plurality of conversion circuits. By shifting the timing of switching between the first state and the second state by π/n, a self-excited converter is provided that causes the main circuit section to generate the power for the ozonizer .

A self-commutated converter is provided that can supply high-frequency, high-voltage AC power to an ozonizer without being affected by the constant of the ozonizer.

FIG. 1 is a block diagram schematically representing a self-excited converter according to an embodiment. FIGS. 2(a) to 2(g) are timing charts schematically representing an example of the operation of the self-excited converter according to the embodiment.

Each embodiment will be described below with reference to the drawings.
Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Furthermore, even when the same part is shown, the dimensions and ratios may be shown differently depending on the drawing.
In the present specification and each figure, the same elements as those described above with respect to the existing figures are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

FIG. 1 is a block diagram schematically representing a self-excited converter according to an embodiment.
As shown in FIG. 1, the self-excited converter 10 for ozonizers includes a main circuit section 12 and a control section 14. The main circuit section 12 is connected to the power supply 2 and also to the ozonizer 4 which is a load. The main circuit section 12 converts the power supplied from the power source 2 into high-frequency, high-voltage AC ozonizer power corresponding to the ozonizer 4 , and supplies the ozonizer power after conversion to the ozonizer 4 . The main circuit section 12 supplies ozonizer power between the pair of electrodes of the ozonizer 4, and generates silent discharge between the pair of electrodes. This allows the ozonizer 4 to generate ozone. The ozonizer power supplied to the ozonizer 4 is, for example, single-phase AC power.

The power source 2 is, for example, an AC power source. In this case, the main circuit section 12 is connected to the power source 2 via the transformer 3 or the like, for example. The main circuit section 12 converts the first AC power supplied from the power source 2 into second AC power compatible with the ozonizer 4, and supplies the second AC power to the ozonizer 4 as ozonizer power. The first AC power of the power source 2 is, for example, three-phase AC power. The main circuit section 12 converts, for example, three-phase AC power supplied from the power source 2 into single-phase AC power compatible with the ozonizer 4 and supplies the same to the ozonizer 4 .

However, the AC power of the power source 2 may be single-phase AC power or the like. Further, the power source 2 is not limited to an AC power source, and may be a DC power source. The main circuit section 12 may convert DC power into AC power and supply it to the ozonizer 4. The main circuit section 12 may have any configuration capable of converting the power supplied from the power source 2 into AC ozonizer power compatible with the ozonizer 4.

The control section 14 is connected to the main circuit section 12. The control unit 14 controls the power conversion operation by the main circuit unit 12.

The main circuit section 12 has a plurality of conversion circuits 20. The plurality of conversion circuits 20 are each connected to the power supply 2. In other words, the plurality of conversion circuits 20 are connected to the power supply 2 in parallel. Thereby, the power of the power supply 2 is input to each of the plurality of conversion circuits 20. The plurality of conversion circuits 20 convert the power supplied from the power source 2 into AC power. In this example, the plurality of conversion circuits 20 convert AC power supplied from the power source 2 into other AC power. More specifically, the plurality of conversion circuits 20 convert the power supplied from the power source 2 into single-phase AC power.

The plurality of conversion circuits 20 have a pair of AC output terminals 20a and 20b that output AC power. A pair of AC output terminals 20a and 20b of the plurality of conversion circuits 20 are each connected in series. In other words, the output sides of the plurality of conversion circuits 20 are connected in series. For example, one AC output terminal 20a of one conversion circuit 20 is connected to the other AC output terminal 20b of the next conversion circuit 20. Thereby, the output sides of the plurality of conversion circuits 20 are connected in series. The AC output terminal 20a on one end side and the AC output terminal 20b on the other end side of the plurality of conversion circuits 20 connected in series are connected to the ozonizer 4.

In the main circuit section 12, the output sides of the plurality of conversion circuits 20 connected in series are directly connected to the ozonizer 4 without using an inductive load such as a high frequency transformer or a resonant reactor. Thereby, in the main circuit section 12, the sum of the outputs of the plurality of conversion circuits 20 becomes the output of the main circuit section 12. The main circuit unit 12 generates ozonizer power from the sum of the AC power of the plurality of conversion circuits 20 and supplies it to the ozonizer 4 . In other words, the main circuit section 12 includes a plurality of conversion circuits 20 having a serial multiplex configuration.

In this example, the main circuit section 12 has six conversion circuits 20, U1 to U6. In this example, the number of series connections of the plurality of conversion circuits 20 is six. However, the number of conversion circuits 20 in the main circuit section 12 is not limited to six, and may be any number. The number of conversion circuits 20 may be appropriately set depending on, for example, the magnitude of the voltage required by the ozonizer 4.

Each of the plurality of conversion circuits 20 includes a converter 21 and an inverter 22. Converter 21 converts AC power supplied from power source 2 into DC power. Inverter 22 converts the DC power converted by converter 21 into AC power.

Converter 21 includes a rectifier 23 and a DC capacitor 24. The rectifier 23 has a plurality of bridge-connected rectifying elements 30, and converts the AC power supplied from the power source 2 into pulsating current power using the plurality of rectifying elements 30. The DC capacitor 24 converts the pulsating power converted by the rectifier 23 into DC power. Thereby, AC power supplied from the power source 2 can be converted into DC power.

The inverter 22 has a plurality of switching elements 31 connected in a bridge manner, and converts DC power into AC power by switching the plurality of switching elements 31. The inverter 22 is, for example, a full bridge circuit in which four switching elements 31 are bridge-connected. In this case, in the conversion circuit 20, the series connection point of the two switching elements 31 of the inverter 22 becomes the AC output terminals 20a, 20b of the conversion circuit 20. A self-excited switching element such as an IEGT (Injection Enhanced Gate Transistor), a GCT (Gate Commutated Turn off thyristor), or an IGBT (Insulated Gate Bipolar Transistor) is used as the plurality of switching elements 31 of the inverter 22, for example.

When the voltage of the DC capacitor 24 is V, the inverter 22 outputs a positive voltage +V and a negative voltage -V to the AC output terminals 20a and 20b by switching the plurality of switching elements 31. state, and a state in which no voltage is output (a state in which the voltage between the AC output terminals 20a and 20b is substantially 0V). Inverter 22 is a so-called two-level inverter.

In this way, the plurality of conversion circuits 20 have a first state where the voltage between the AC output terminals 20a and 20b is set to the first voltage, and a second state where the voltage between the AC output terminals 20a and 20b is set to the first voltage. A second state in which the voltage is set is switchable. The first state is, for example, a state in which -V is output between the AC output terminals 20a and 20b. The first state may be, for example, a state in which the voltage between the AC output terminals 20a and 20b is substantially 0V. The second state is, for example, a state in which +V is output between the AC output terminals 20a and 20b.

The conversion circuit 20 further includes reactors 25 and 26, for example. Reactor 25 is connected to AC output terminal 20a. Reactor 26 is connected to AC output terminal 20b. For example, the reactors 25 and 26 suppress noise superimposed on the AC power output from the inverter 22.

However, the configuration of the plurality of conversion circuits 20 is not limited to the above. For example, if the power of the power source 2 is DC power, the converter 21 may be omitted. The reactors 25 and 26 are provided as necessary and can be omitted. The inverter 22 is not limited to a full bridge circuit, but may be a half bridge circuit or the like. The configuration of the plurality of conversion circuits 20 may be any configuration capable of converting the power supplied from the power source 2 into AC power.

The main circuit section 12 may be connected to the ozonizer 4 via a reactor, such as reactors 25 and 26, for suppressing noise superimposed on AC ozonizer power. The main circuit section 12 only needs to be connected to the ozonizer 4 without intervening an inductive load for causing resonance with the ozonizer 4, which is at least a capacitive load.

The control unit 14 is connected to each of the plurality of switching elements 31 of the inverters 22 of the plurality of conversion circuits 20, and controls the power conversion operation by the main circuit unit 12 by controlling the switching of the plurality of switching elements 31 of each inverter 22. control. The control unit 14 controls switching between the first state and the second state of each of the plurality of conversion circuits 20 by controlling switching of the plurality of switching elements 31 of each inverter 22, for example.

FIGS. 2(a) to 2(g) are timing charts schematically representing an example of the operation of the self-excited converter according to the embodiment.
FIGS. 2A to 2F schematically represent examples of control signals input from the control unit 14 to each of the six conversion circuits 20 (inverters 22) U1 to U6.
FIG. 2(g) schematically represents an example of the output voltage output from the main circuit section 12.

Lo of the control signals in FIGS. 2(a) to 2(f) represents a state in which the conversion circuit 20 is set to the first state. Hi of the control signal in FIGS. 2(a) to 2(f) represents a state in which the conversion circuit 20 is set to the second state. When the control signal is set to Lo, the first voltage (for example, -V) is output from the conversion circuit 20, and when the control signal is set to Hi, the second voltage (for example, -V) is output from the conversion circuit 20. , +V) are output. However, the relationship between the control signal and the first and second states of the conversion circuit 20 is not limited to the above. The control signal may be any signal capable of switching the conversion circuit 20 between the first state and the second state.

As shown in FIGS. 2A to 2F, the control unit 14 switches the plurality of conversion circuits 20 between the first state and the second state at the operating frequency f of the ozonizer 4. At this time, the control unit 14 sets the duty ratio of switching the conversion circuit 20 between the first state and the second state to 50%, for example. In other words, the control unit 14 switches the plurality of conversion circuits 20 between the first state and the second state every half cycle of the operating frequency f of the ozonizer 4. Then, when the number of the plurality of conversion circuits 20 is n, the control unit 14 shifts the timing of switching between the first state and the second state of the plurality of conversion circuits 20 by π/n. In this example, since the number of the plurality of conversion circuits 20 is six, the control unit 14 shifts the timing of switching between the first state and the second state of the plurality of conversion circuits 20 by π/6. Thereby, the control unit 14 causes the main circuit unit 12 to generate ozonizer power.

The output voltage of the main circuit section 12 (voltage of ozonizer power) is the sum of the output voltages of the plurality of conversion circuits 20. Therefore, when the plurality of conversion circuits 20 are switched between the first state and the second state as described above, the output voltage of the main circuit section 12 is changed from that of the ozonizer 4, as shown in FIG. At the operating frequency f, the voltage becomes a high-frequency, high-voltage alternating current voltage that changes the magnitude of the voltage in steps of the number n+1 of the plurality of conversion circuits 20. The frequency of the output voltage of the main circuit section 12 (the operating frequency f of the ozonizer 4) is, for example, about 0.5 kHz or more and 20 kHz or less. The magnitude (maximum value) of the output voltage of the main circuit section 12 is, for example, approximately 1 kV or more and 10 kV or less.

As described above, in the self-commutated converter 10 according to the present embodiment, the main circuit section 12 has a plurality of conversion circuits 20, and has a series multiplex configuration in which the output sides of the plurality of conversion circuits 20 are connected in series. Thereby, in the self-commutated converter 10, the main circuit section 12 can generate the high-frequency, high-voltage alternating current ozonizer power required by the ozonizer 4 without requiring a high-frequency transformer, a resonant reactor, or the like. Therefore, in the self-excited converter 10, there is no need to design a high frequency transformer, a resonant reactor, etc. each time according to the constant of the ozonizer 4, and the increase in design cost and lengthening of lead time due to each design is suppressed. be able to.

Further, since there is no longer a need for a component that is affected by the constant of the ozonizer 4, it becomes possible to use the self-excited converter 10 in common for a plurality of ozonizers 4 having different constants, for example. The versatility of the self-excited converter 10 can be increased compared to a load resonance type configuration that uses a high frequency transformer, a resonant reactor, or the like.

In this way, the self-commutated converter 10 according to the present embodiment can supply high-frequency, high-voltage AC power to the ozonizer 4 without being affected by the constant of the ozonizer 4.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

2...Power supply, 3...Transformer, 4...Ozonizer, 10...Self-excited converter, 12...Main circuit section, 14...Control section, 20...Conversion circuit, 20a, 20b...AC output terminal, 21...Converter, 22...Inverter , 23... Rectifier, 24... DC capacitor, 25, 26... Reactor, 30... Rectifying element, 31... Switching element

Claims (3)

A self-excited converter for an ozonizer that supplies alternating current power between a pair of electrodes of the ozonizer,
a main circuit unit that converts power supplied from a power source into AC ozonizer power compatible with the ozonizer and supplies the ozonizer power to the ozonizer;
a control unit that controls power conversion operation by the main circuit unit;
Equipped with
The main circuit section includes a plurality of conversion circuits that convert the power supplied from the power source into AC power,
The plurality of conversion circuits have a pair of AC output terminals that output the AC power,
The pair of AC output terminals of the plurality of conversion circuits are each connected in series,
The main circuit unit generates the ozonizer power by the sum of the AC power of the plurality of conversion circuits, and supplies the ozonizer power to the ozonizer,
The plurality of conversion circuits have a first state in which the voltage between the pair of AC output terminals is set to a first voltage, and a voltage between the pair of AC output terminals is set to a second voltage higher than the first voltage. It is possible to switch between the second state and the second state.
The control unit switches the first state and the second state of the plurality of conversion circuits at the operating frequency of the ozonizer, and when the number of the plurality of conversion circuits is n, the control unit switches the first state and the second state of the plurality of conversion circuits. A self-excited converter that causes the main circuit section to generate power for the ozonizer by shifting timing of switching between the first state and the second state by π/n . When switching the first state and the second state of the plurality of conversion circuits at the operating frequency of the ozonizer, the control unit changes the first state of the plurality of conversion circuits by half a period of the operating frequency of the ozonizer. The self-commutated converter according to claim 1, wherein the self-commutated converter switches between the state and the second state. The self-excited converter according to claim 1 or 2 , wherein the main circuit section is directly connected to the ozonizer without an inductive load.

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