JP2005147125A - Power source circuit for plasma reactor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power source circuit for a plasma reactor enhancing energy efficiency in the plasma reactor, and a power source control method for a plasma reactor. <P>SOLUTION: The power source circuit 10 for the plasma reactor has a voltage measurement part 14 and a current measurement part 16 for measuring a voltage and a current fed to the plasma reactor; and a control means 18 for calculating a thrown power amount from the measured voltage value and the current value to the plasma reactor and feedback-control the high voltage power source such that the required power amount required in the plasma reactor is fed to the plasma reactor based on the thrown power amount. The power source control method for the plasma reactor includes a process for calculating the thrown power amount from the measured voltage value and the current value to the plasma reactor; and a process for feedback-controlling the high voltage power source such that the required power amount is fed to the plasma reactor based on the calculated thrown power amount. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power supply circuit for a plasma reactor, particularly a plasma reactor for purifying exhaust gas from an internal combustion engine or the like, and a method for controlling the power supply for the plasma reactor.

At present, various purification systems using plasma have been proposed for exhaust purification of automobiles, exhaust purification of garbage incineration plants, and generation of ozone for sterilization and deodorization. Particularly in the field of automobile exhaust purification, it is known to use plasma in combination with an exhaust purification catalyst to purify NO _x , CO (carbon monoxide), HC (hydrocarbon component) and PM (particulate). ing.

  When using a plasma reactor in a moving medium such as an automobile, the performance of the plasma reactor itself is also important, but what kind of power supply is used to supply power is important from the viewpoint of reliability and energy efficiency. come. Therefore, various modes and power supply circuits for supplying power to the plasma reactor have been proposed.

  For example, in Patent Document 1, low voltage power for control and high voltage power for a plasma reactor are respectively generated by an engine as a power source for vehicle travel. Patent Document 2 proposes a method for determining an abnormality of a plasma reactor based on a change in a waveform of a voltage or current supplied to the plasma reactor.

  When such a pulse power supply is used in combination with a plasma reactor for exhaust purification of an automobile, for example, as shown in Patent Document 1, power supply is intermittently supplied depending on the exhaust purification catalyst and / or the warm-up state of the engine. It is known to adjust and / or regulate.

Japanese Patent Laid-Open No. 7-253014 JP 2001-314749 A

  When a conventionally known pulse power source is used in combination with a plasma reactor for purifying automobile exhaust, for example, as shown in Patent Document 1, power supply is intermittently supplied depending on the exhaust purification catalyst and / or the warm-up state of the engine. And / or adjustment (eg, by increasing or decreasing the pulse repetition frequency and / or increasing or decreasing the output of each pulse).

  When the power supply to the plasma reactor is adjusted with high accuracy in accordance with the exhaust purification catalyst and / or the warm-up state of the engine, it is necessary to know the generation state of the plasma. However, the plasma generation state may vary depending on the flow rate and / or composition of the exhaust, the deterioration state of the plasma reactor, and the degree of warm-up, and is difficult to know directly.

  Accordingly, the present invention provides a power supply circuit and method for controlling the input power to the plasma reactor.

  The power supply circuit for a plasma reactor according to the present invention includes a voltage measurement unit that measures a voltage applied to the plasma reactor, a current measurement unit that measures a current flowing through the plasma reactor, a voltage measurement unit, and a voltage and a current value measured by the current measurement unit. Calculate the actual power input to the plasma reactor, and feed back the high voltage power supply based on this input power so that the required power required by the plasma reactor is fed to the plasma reactor by the high voltage power supply Control means for controlling.

  According to the power supply circuit for a plasma reactor of the present invention, it is possible to achieve highly accurate input power control based on the input power actually input to the plasma reactor.

  In the power supply circuit for a plasma reactor according to the present invention, the plasma reactor may be an exhaust purification plasma reactor.

  Examples of the exhaust gas purification plasma reactor include a plasma reactor for treating exhaust gas from a waste treatment plant and exhaust gas from an internal combustion engine such as an automobile engine.

In the power supply circuit for a plasma reactor of the present invention, the required power amount is at least based on the flow rate of the exhaust gas flowing through the plasma reactor, particularly with respect to one or more of a desired exhaust purification rate, for example, HC, NO _x and CO. It can be determined such that a purification rate of 50%, 70% or 90% is achieved.

  According to this, when the flow rate of the exhaust gas is large, that is, when the residence time of the exhaust gas in the plasma reactor that processes the exhaust gas is short, the input power per unit time is increased, and conversely, when the exhaust gas flow rate is small, that is, When the residence time of the exhaust gas in the plasma reactor is long, the input power per unit time can be reduced to contribute to the improvement of energy efficiency. For example, when the plasma reactor is an automobile exhaust gas purification plasma reactor, the flow rate of the exhaust gas can be determined from the engine speed or the like.

  In the power supply circuit for a plasma reactor of the present invention, an exhaust purification catalyst is arranged on the exhaust flow upstream side and / or the exhaust flow downstream side in the plasma reactor, and the required power amount is a warm-up state of the exhaust purification catalyst. Can be determined based on

  According to this, when the exhaust purification catalyst is not warmed up sufficiently and the exhaust purification by the catalyst is insufficient, the exhaust gas by the exhaust purification catalyst is increased by supplying power to the plasma reactor or increasing the input power to the plasma reactor. Can assist in purification.

  In the power supply circuit for a plasma reactor according to the present invention, the current measuring unit can have a shunt resistor arranged in the main path for power feeding and a voltmeter arranged in the shunt.

  This is useful for high-accuracy detection of the amount of current flowing through the plasma reactor, particularly high-precision detection of short pulse currents with a fast rise time, such as nanosecond order pulse currents.

  In the power supply circuit for a plasma reactor of the present invention, the current measuring unit can further include an operational amplifier disposed in the shunt, and preferably a surge clamper connected to the input side of the operational amplifier.

  According to this, since the voltage value measured by the voltmeter can be amplified by using the operational amplifier, the resistance value of the shunt resistor can be reduced to reduce the influence on the power supply circuit. Further, by using a surge clamper, for example, when the plasma reactor shifts to spark discharge, it is possible to prevent a high voltage from entering the current detection circuit and damaging the circuit.

  The method for controlling a power source for a plasma reactor according to the present invention includes determining a required power amount required for the plasma reactor, measuring a voltage value and a current value actually supplied to the plasma reactor by a high voltage power source, and measuring. Calculating the actual input power amount to the plasma reactor from the calculated voltage value and current value, and based on the calculated input power amount, the high voltage power supply is connected so that the required power amount is supplied to the plasma reactor. Including feedback control.

  According to the method for controlling a power source for a plasma reactor of the present invention, it is possible to achieve highly accurate input power control based on the input power actually input to the plasma reactor.

  When the power source for the exhaust gas purification plasma reactor is controlled by the method for controlling the power source for the plasma reactor according to the present invention, the required amount of electric power is achieved particularly based on the flow rate of the exhaust gas flowing through the plasma reactor. As can be determined.

  According to the present invention, high-accuracy power input control to the plasma reactor can be achieved.

  Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings. However, these drawings are diagrams schematically showing a power circuit for a plasma reactor constituting the present invention, and the present invention is not limited to these embodiments. It is not limited to.

  An embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, the plasma reactor power supply circuit 10 of the present invention surrounded by a two-dot broken line includes a voltage measuring unit 14 that measures a voltage applied to the plasma reactor P, and a current that measures a current flowing through the plasma reactor. The measurement unit 16 and control means 18 for controlling the high voltage power supply 12 are provided. Here, the voltage measurement unit 14 and the control unit 18 are connected by a signal line 15, and the current measurement unit 15 and the control unit 18 are connected by a signal line 16, and the control unit 18 and the control unit 18 have a high voltage. The power supply 12 is connected by a signal line 19. The control means 18 supplies the plasma reactor with the required power amount required by the plasma reactor P based on the input power amount to the plasma reactor P calculated from the measured values at the voltage measurement unit 14 and the current measurement unit 16. As described above, the high-voltage power supply 12 is feedback-controlled. The plasma reactor power supply circuit is preferably bus-connected so that the parasitic inductance is minimized.

  In the use of the plasma reactor power supply circuit 10 shown in FIG. 1, first, the flow rate and / or composition of the exhaust gas to be processed in the plasma reactor, the warm-up state of the exhaust purification catalyst used in combination with the plasma reactor, or these Based on the combination or the like, for example, the control means 12 determines the required power amount required in the plasma reactor P and supplies this power amount from the high voltage power supply 12. Here, when determining the required power amount based on the flow rate of the exhaust gas to be processed by the plasma reactor, the required power amount can be calculated based on the exhaust flow rate and optionally the desired exhaust gas purification rate. It is also possible to make a power amount map and determine the required power amount based on this map.

  Thereafter, the voltage measuring unit 14 and the current measuring unit 16 measure the voltage and current supplied to the plasma reactor P, respectively, and send these measured values to the control means 18 through the signal lines 15 and 17, respectively. The amount of electric power actually supplied to the plasma reactor P is calculated from the product of these measured values. The detection of the input power can be performed, for example, as shown in FIG. That is, the voltage (a) and current (b) applied to the plasma reactor P are detected over a period determined by the gate signal (d), and these are multiplied and integrated to obtain an integrated power value (d), and peak hold (E) and analog-to-digital conversion (f) are performed to obtain a digital signal, and the power per pulse can be taken into the control means 18.

  The control unit 18 compares the actual input power amount calculated here with the required required power amount, and the signal line is supplied so that the required power amount required by the plasma reactor P is supplied to the plasma reactor. The high voltage power supply 12 is feedback-controlled through 19. In order to supply the required power amount to the plasma reactor, in addition to increasing / decreasing the input power amount based on a comparison between the actual input power amount and the required power amount, the input power amount per pulse and the number of pulses It is also possible to control the high voltage power supply so that the product becomes the required power amount.

  Hereinafter, each part constituting the plasma reactor power supply circuit of the present invention shown in FIG. 1 will be described in more detail.

The current measuring unit 16 may be an ammeter 22 connected in series to the power supply circuit as shown in FIG. 2, but other modes as shown in FIGS. 3 to 5 may be used. That is, the current measuring unit 16 may be a shunt circuit having _two resistors R ₁ and R ₂ and an ammeter 32 as shown in FIG. In this case, the current value can be determined from the product of the indicated value of the ammeter 32 and the ratio (R ₂ / R ₁ ) of these two resistors.

Further, the current measuring unit 16 may include a shunt resistor R _s disposed on the main path for supplying power and a voltmeter 42 disposed on the shunt as shown in FIG. Thus, it is preferable that the resistor used in the circuit has a low inductance. In this case, the current value can be determined by dividing the indicated value of the voltmeter 42 by the resistance value of the shunt resistor R _s .

Further, when a shunt resistor is used as shown in FIG. 4, an operational amplifier 52 is further arranged in a shunt as shown in FIG. 5, and the voltage value measured by the voltmeter 54 can be amplified. That is, it is possible to reduce the influence by reducing the resistance value of the shunt resistor R _s to the power supply circuit. In this case, the current value can be determined from the product of the value obtained by dividing the indicated value of the voltmeter 54 by the resistance value of the shunt resistor R _s and the voltage gain of the operational amplifier. Although only one operational amplifier is used here, it is possible to amplify the voltage to a signal level by using a plurality of operational amplifiers, for example, using two operational amplifiers. Further, the operational amplifier needs to have a wide frequency band in order to handle a high-speed pulse signal. By connecting the surge clamper 56 to the input side of the operational amplifier, it is possible to prevent the high voltage from entering the current detection circuit and damaging the circuit when the plasma reactor shifts to spark discharge.

  An arbitrary voltmeter can be used as the voltage measuring unit 14, but it must be capable of measuring a high voltage applied to the plasma reactor, for example, a voltage of several kV to 50 kV.

  The control means 18 may be an electronic device only for controlling the high-voltage power supply 12, or may have other functions like an ECU (electronic control unit) in the case of an automobile.

  The high voltage power supply 12 may generate a pulsed or steady DC or AC voltage. As the applied voltage and the pulse period, general values for generating plasma can be used. For example, a pulse voltage of several kV to 50 kV and a pulse period of 10 Hz to 2,000 Hz can be used. A DC voltage, an AC voltage, a periodic waveform voltage, or the like can be applied between both electrodes, and a DC pulse voltage is particularly preferable because corona discharge can be caused satisfactorily. When a DC pulse voltage is used, the applied voltage, pulse width, and pulse period can be arbitrarily selected as long as corona discharge can occur between both electrodes. The voltage of the applied voltage may be subject to certain restrictions from the design of the device and economy, but a high voltage and a short pulse period voltage are desirable from the viewpoint of generating corona discharge satisfactorily. .

  The plasma reactor P fed by the plasma reactor power supply circuit of the present invention may be any plasma reactor. For example, this plasma reactor may be an exhaust purification plasma reactor as shown in FIG. 2 of Patent Document 2, or may be as shown in FIG. Here, FIGS. 6A and 6B are a side view and a cross-sectional view of the plasma reactor, respectively.

  In the plasma reactor shown in FIG. 6, a discharge space 66 exists between the mesh electrodes 62 and 64 connected to the high voltage power supply 12, and fluid to be processed in the plasma reactor flows through the discharge space 66. Have been to.

  Here, the mesh electrodes 62 and 64 can be made of any material capable of applying a voltage between these electrodes. As the material, a conductive material or a material such as a semiconductor can be used, but a metal material is preferable. Specifically, Cu, W, stainless steel, Fe, Pt, Al or the like can be used as this metal material, and stainless steel is particularly preferable from the viewpoint of cost and durability.

An insulating carrier such as a ceramic honeycomb carrier is disposed in the discharge space 66 between the mesh electrodes 62 and 64, and an exhaust purification catalyst such as a so-called three-way catalyst, a NO _x storage reduction catalyst, An oxidation catalyst can be supported. However, instead of or in addition to disposing the exhaust purification catalyst in the plasma reactor, the exhaust purification catalyst can be disposed in the plasma reactor on the exhaust flow upstream side and / or the exhaust flow downstream side.

FIG. 1 is a circuit diagram showing one embodiment of a power supply circuit for a plasma reactor according to the present invention. FIG. 2 is a circuit diagram showing one embodiment of a current measuring unit that can be used in the plasma reactor power supply circuit of the present invention. FIG. 3 is a circuit diagram showing another embodiment of a current measuring unit that can be used in the plasma reactor power supply circuit of the present invention. FIG. 4 is a circuit diagram showing another embodiment of a current measuring unit that can be used in the plasma reactor power supply circuit of the present invention. FIG. 5 is a circuit diagram showing another embodiment of a current measuring unit that can be used in the plasma reactor power supply circuit of the present invention. FIG. 6 is a side view and a cross-sectional view showing one embodiment of a plasma reactor in which power supply can be controlled by the plasma reactor power supply circuit of the present invention. FIG. 7 is a timing chart for detecting the input power according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 ... High voltage power supply 14 ... Voltage measuring part 15, 17, 19 ... Signal line 16 ... Current measuring part 18 ... Control means 22, 32 ... Ammeter 42, 54 ... Voltmeter 52 ... Operational amplifier 56 ... Surge clamper P ... Plasma reactor R ₁ , R ₂ ... Shunt resistance R _s ... Shunt resistance

Claims (9)

A voltage measuring unit for measuring the voltage applied to the plasma reactor,
A current measuring unit for measuring a current flowing through the plasma reactor;
The actual input power amount to the plasma reactor is calculated from the voltage and current values measured by the voltage measurement unit and the current measurement unit, and based on this input power amount, the required power amount required for the plasma reactor is high. Control means for feedback-controlling the high-voltage power supply so that the plasma reactor is powered by the voltage power supply;
A plasma reactor power circuit.   The power supply circuit for a plasma reactor according to claim 1, wherein the plasma reactor is an exhaust purification plasma reactor.   The power supply circuit for a plasma reactor according to claim 2, wherein the required power amount is determined based on a flow rate of exhaust gas flowing through the plasma reactor.   The power supply circuit for a plasma reactor according to claim 3, wherein the required power amount is determined so as to achieve a desired exhaust gas purification rate based on a flow rate of exhaust gas flowing through the plasma reactor.   In the plasma reactor, an exhaust purification catalyst is arranged on the exhaust flow upstream side and / or the exhaust flow downstream side, and the required power amount is determined based on a warm-up state of the exhaust purification catalyst. The power supply circuit for a plasma reactor according to any one of claims 2 to 4.   The power supply circuit for a plasma reactor according to any one of claims 1 to 5, wherein the current measuring unit includes a shunt resistor arranged in a main path for power feeding and a voltmeter arranged in a shunt.   The power supply circuit for a plasma reactor according to claim 6, wherein the current measurement unit further includes an operational amplifier disposed in the shunt. Determining the amount of power required in the plasma reactor;
Measuring voltage and current values actually supplied to the plasma reactor by a high voltage power source;
Calculate the actual input power amount to the plasma reactor from the measured voltage value and current value, and based on the calculated input power amount, the required power amount is supplied to the plasma reactor, Feedback controlling the high voltage power supply;
A method for controlling a power source for a plasma reactor, comprising:   9. The method of controlling a power source for a plasma reactor according to claim 8, wherein the plasma reactor is an exhaust purification plasma reactor, and the required power amount is determined based on a flow rate of exhaust gas flowing through the plasma reactor.

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