JP2017152341A - Control apparatus for plasma reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control apparatus for a plasma reactor, capable of determining occurrence of an abnormal discharge in a plasma reactor.SOLUTION: In a control apparatus for a plasma reactor, an application current applied to a discharge electrode of the plasma reactor is detected. A detected value is integrated in a period that the application current value is set to a positive value, thereby an integration current value is acquired. A peak current value as a peak value of the application current in the period that the application current value is set to a positive value is acquired. When the integrated current value is equal to a predetermined integrated abnormality determination value or more (S1: YES) or when the peak current value is equal to a predetermined peak abnormality determination value or more (S2: YES), it is determined that an abnormal discharge occurs in the plasma reactor (S3).SELECTED DRAWING: Figure 5

Description

  The present invention relates to a control device used in a plasma reactor.

  Exhaust gas discharged from an engine, particularly a diesel engine, includes CO (carbon monoxide), HC (hydrocarbon), NOx (nitrogen oxide), PM (particulate matter), and the like.

  As a technique for removing PM contained in exhaust gas, a technique for removing PM contained in exhaust gas using a plasma reactor has been proposed. The plasma reactor includes a plurality of electrode panels. The electrode panel has, for example, a configuration in which an electrode is built in a dielectric, and the plurality of electrode panels are arranged to face each other with a gap in a direction orthogonal to the flow direction of the exhaust gas. When a voltage is applied between the electrodes from the power supply device for the plasma reactor, dielectric barrier discharge occurs, low temperature plasma (non-equilibrium plasma) is generated between the electrode panels, and PM in the exhaust gas flowing between the electrode panels is oxidized. Is removed.

  The plasma reactor power supply device includes a flyback step-up transformer. A switching element is connected in series to the primary coil of the flyback type step-up transformer, and a DC power source is connected to a series circuit of the primary coil and the switching element. The secondary coil of the flyback type step-up transformer is connected to the electrode of the plasma reactor.

  When the switching element is turned on, a current flows through the primary coil of the flyback type step-up transformer, and energy is stored in the primary coil. After that, when the switching element is turned off, the energy accumulated in the primary coil is released, an electromotive force is generated in the primary coil, and a secondary voltage corresponding to the turn ratio is generated in the secondary coil of the flyback step-up transformer. To do. By repeatedly turning on / off the switching element, a secondary voltage is generated in a pulsed manner, and a secondary voltage that changes in a pulse waveform is applied between the electrodes of the plasma reactor.

JP 2002-129949 A

  In order to control the discharge in the plasma reactor, for example, the amount of PM contained in the exhaust gas and the voltage value applied to the electrode of the plasma reactor are acquired by the control device. Then, the control device sets a target voltage value corresponding to the amount of PM contained in the exhaust gas, and turns on / off the switching element so that the voltage value applied between the electrodes of the plasma reactor matches the target voltage value. Is controlled.

  By providing a voltage sensor that detects a voltage applied to the electrode of the plasma reactor, a voltage value applied to the electrode of the plasma reactor can be acquired. However, the voltage applied between the electrodes of the plasma reactor is a high voltage of several kV to several tens of kV, and it is technically difficult to produce such a voltage sensor that can detect such a high voltage, even if it can be produced. Even so, it becomes expensive and unsuitable for mass production.

  Therefore, the applicant provides a current sensor for detecting the current applied to the electrode of the plasma reactor, and the voltage applied to the electrode of the plasma reactor from the integrated value (integrated current value) of the current value detected by the current sensor. A method to obtain the value by estimation has been proposed previously.

  FIG. 6 is a graph showing waveforms of current and voltage applied to the plasma reactor during normal discharge. FIG. 7 is a graph showing waveforms of current and voltage applied to the plasma reactor during abnormal discharge.

  When the switching element of the power supply device for the plasma reactor is switched from on to off and the discharge is normally generated between the electrode panels (during normal discharge), the plasma reactor is applied to the electrode of the plasma reactor as shown in FIG. Current and voltage change. On the other hand, when an abnormal discharge occurs between the electrode panels when the switching element of the power supply device for the plasma reactor is switched from on to off due to a defect such as a crack in the electrode panel (during abnormal discharge) As shown in FIG. 7, the current and voltage applied to the electrodes of the plasma reactor change.

  In the configuration in which the integration period of the current value for estimating the voltage value applied to the electrode of the plasma reactor is set until the voltage value reaches the maximum voltage value (while the current value takes a positive value), FIG. As shown in FIG. 7 with hatching, the integrated current values are substantially the same during normal discharge and during abnormal discharge. Therefore, in the configuration provided with the voltage sensor for detecting the voltage applied to the electrode of the plasma reactor, abnormal discharge can be determined from the detected voltage value, whereas the current applied to the electrode of the plasma reactor In the configuration provided with the current sensor for detecting the abnormal discharge, the abnormal discharge cannot be determined from the integrated current value.

  The objective of this invention is providing the control apparatus for plasma reactors which can determine generation | occurrence | production of abnormal discharge in a plasma reactor.

  In order to achieve the above object, a control device for a plasma reactor according to one aspect of the present invention includes a current integrating unit that integrates a value of an applied current applied to an electrode of a plasma reactor over a predetermined period, and an application during a predetermined period. Peak value acquisition means for acquiring a peak value of current, and whether the integrated current value by the current integration means is greater than or equal to a predetermined integration abnormality determination value, or the peak value acquired by the peak value acquisition means is a predetermined peak abnormality determination And abnormal discharge determination means for determining occurrence of abnormal discharge in the plasma reactor when the value is equal to or greater than the value.

  According to this configuration, the applied current applied to the electrode of the plasma reactor is detected, and the value of the current is integrated over a predetermined period. Further, the peak value of the applied current during the predetermined period is acquired.

  If the integrated current value is equal to or greater than a predetermined accumulated abnormality determination value, or the peak value is equal to or greater than a predetermined peak abnormality determination value, or at least one of them is established, it is determined that an abnormal discharge has occurred in the plasma reactor. . Specifically, when an abnormal discharge occurs in the plasma reactor, an integrated current value different from that during normal discharge is obtained, and when the integrated current value is equal to or greater than the integrated abnormality determination value, the occurrence of the abnormal discharge is determined. The Even if an abnormal discharge occurs in the plasma reactor, even if the integrated current value is almost the same as the integrated current value during normal discharge and less than the integrated abnormality determination value, the applied current flowing to the electrode due to the abnormal discharge When the peak value exceeds the peak abnormality determination value, the occurrence of the abnormal discharge is determined.

  Therefore, even when an abnormal discharge occurs in the plasma reactor, it is possible to determine the occurrence of the abnormal discharge without providing a voltage sensor for detecting the voltage applied to the electrode of the plasma reactor.

  Instead of the peak value of the applied current, the time change rate of the applied current may be acquired. When abnormal discharge occurs in the plasma reactor, the applied current flowing through the electrodes of the plasma reactor changes sharply. In particular, the time change rate immediately before the applied current reaches the peak value is greatly different from that during normal discharge. Therefore, when the time change rate of the applied current exceeds a predetermined change rate abnormality determination value, the occurrence of abnormal discharge may be determined.

  That is, a control device for a plasma reactor according to another aspect of the present invention includes a current integrating unit that integrates a value of an applied current applied to an electrode of a plasma reactor over a predetermined period, and a time change rate of the applied current in a predetermined period. The change rate acquisition means to acquire and the integrated current value by the current integration means are greater than or equal to a predetermined integration abnormality determination value, or the time change rate acquired by the change rate acquisition means is greater than or equal to a predetermined change rate abnormality determination value In some cases, it includes abnormal discharge determination means for determining occurrence of abnormal discharge in the plasma reactor.

  Also with this configuration, when an abnormal discharge occurs in the plasma reactor, it is possible to determine the occurrence of the abnormal discharge without providing a voltage sensor for detecting the voltage applied to the electrode of the plasma reactor.

  According to the present invention, when an abnormal discharge occurs in the plasma reactor, it is possible to determine the occurrence of the abnormal discharge without providing a voltage sensor for detecting the voltage applied to the electrode of the plasma reactor.

It is sectional drawing which shows the structure of a plasma reactor schematically. It is a circuit diagram which shows the structure of the power supply device for plasma reactors. It is a block diagram which shows the functional structure of the control apparatus for plasma reactors concerning one Embodiment of this invention. It is a circuit diagram which shows the structure of an electric current integration and peak detection circuit. It is a flowchart which shows the flow of an abnormal discharge determination process. It is a graph which shows the waveform of the electric current and voltage which are applied to a plasma reactor at the time of normal discharge. It is a graph which shows the waveform of the electric current and voltage applied to a plasma reactor at the time of abnormal discharge.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Plasma reactor>
FIG. 1 is a cross-sectional view schematically showing the configuration of the plasma reactor 1.

  The plasma reactor 1 is interposed in the middle of an exhaust pipe 2 such as an exhaust pipe in order to remove PM contained in exhaust gas discharged from a vehicle engine (not shown), for example.

The plasma reactor 1 is provided with discharge electrodes 3 and 4. The discharge electrodes 3 and 4 extend in the direction along the flow of the exhaust gas, and are alternately arranged in parallel with a space therebetween. An example of the material of the discharge electrodes 3 and 4 is tungsten. In addition, the discharge electrodes 3 and 4, for example, are built in a rectangular plate-like dielectric 5, thereby constituting an electrode panel 6 together with the dielectric 5. Between the electrode panels 6, the space | interval which can distribute | circulate waste gas is opened. As a material of the dielectric 5, Al ₂ O ₃ (alumina) can be exemplified.

  A high voltage in the form of a pulse wave output from the plasma reactor power supply device 7 is applied between the discharge electrodes 3 and 4. When the output voltage of the plasma reactor power supply device 7 is applied between the discharge electrodes 3 and 4, a dielectric barrier discharge is generated between the electrode panels 6, and plasma is generated by the dielectric barrier discharge. Due to the generation of plasma, PM contained in the exhaust gas flowing between the electrode panels 6 is oxidized (burned) and removed.

<Power supply for plasma reactor>
FIG. 2 is a circuit diagram showing the configuration of the plasma reactor power supply device 7.

  The plasma reactor power supply device 7 includes a flyback step-up transformer 11, an energization control switching element 12, and a gate drive circuit 13.

  The flyback step-up transformer 11 has a primary coil 21 and a secondary coil 22. One end of the primary coil 21 is connected to the wiring 23. A positive terminal of a battery 25 is connected to the wiring 23 via a fuse 24. The battery 25 is an in-vehicle battery that outputs a DC voltage of 12V, for example. The other end of the primary coil 21 is connected (grounded) to the ground via the energization control switching element 12. One end and the other end of the secondary coil 22 are connected to the discharge electrodes 3 and 4 of the plasma reactor 1, respectively.

  The energization control switching element 12 is, for example, an enhancement type nMOSFET, and its drain is connected to the other end of the primary coil 21 of the flyback step-up transformer 11 and its source is connected to the ground.

  The gate drive circuit 13 is a circuit that outputs a signal (gate signal) for turning on / off the energization control switching element 12.

<Control device for plasma reactor>
In order to control the power supplied from the plasma reactor power supply device 7 to the plasma reactor 1, a plasma reactor control device 31 is connected to the plasma reactor power supply device 7.

  The plasma reactor control device 31 includes a CPU, a ROM, a RAM, and the like, and may be one of a plurality of ECUs (Electronic Control Units) mounted on the vehicle. It may be incorporated in one of these. A current sensor 32 is connected to the plasma reactor control device 31. The current sensor 32 detects an applied current applied to the discharge electrodes 3 and 4 of the plasma reactor 1, that is, an applied current output from the plasma reactor power supply device 7, and outputs a signal corresponding to the current value.

  The plasma reactor control device 31 controls the gate drive circuit 13 to switch output / stop of the signal from the gate drive circuit 13. That is, when an ON instruction signal is input from the plasma reactor control device 31 to the gate drive circuit 13, a signal is output from the gate drive circuit 13, and the signal is input to the energization control switching element 12. The control switching element 12 is turned on. When the off instruction signal is input from the plasma reactor control device 31 to the gate drive circuit 13, the output of the signal from the gate drive circuit 13 is stopped, and no signal is input to the gate of the energization control switching element 12. As a result, the energization control switching element 12 is turned off.

  When the energization control switching element 12 is turned on, a current flows through the primary coil 21 of the flyback type step-up transformer 11, and energy is accumulated in the primary coil 21. Thereafter, when the energization control switching element 12 is turned off, the energy accumulated in the primary coil 21 is released, an electromotive force is generated in the primary coil 21, and the secondary coil 22 of the flyback step-up transformer 11 has a turn ratio. A corresponding secondary voltage is generated. By repeatedly turning on / off the energization control switching element 12, a secondary voltage is generated in a pulsed manner, and a secondary voltage that changes in a pulse waveform is applied between the discharge electrodes 3 and 4 of the plasma reactor 1.

  FIG. 3 is a block diagram showing a functional configuration of the plasma reactor control device 31 according to the embodiment of the present invention.

  The plasma reactor control device 31 includes a current integration / peak detection circuit 41, an applied voltage estimation unit 42, a target voltage setting unit 43, a subtraction unit 44, a signal output unit 45, and an abnormal discharge determination unit 46.

  FIG. 4 is a circuit diagram showing a configuration of the current integration / peak detection circuit 41.

  The current integration / peak detection circuit 41 integrates the current value of the applied current detected by the current sensor 32 and outputs the integrated current value, and the peak current value that is the peak value (maximum value) of the applied current. This is an analog circuit having a configuration in which a peak detection circuit 52 for detecting the above is provided in parallel.

  The current integrating circuit 51 holds an integrating circuit 53 that integrates the current value of the applied current with time, an inverting amplifier 54 that amplifies the output of the integrating circuit 53 and inverts its polarity, and a maximum value of the output of the inverting amplifier 54. And a peak hold / reset circuit 55 for output.

  The integrating circuit 53 has a circuit configuration similar to that of a bandpass filter.

  The inverting amplifier 54 has a widely known configuration, and a resistor for eliminating the influence of a bias current is connected to the “+” terminal of the operational amplifier.

  The peak hold / reset circuit 55 is a combination of a general peak hold circuit and a reset circuit. When the input from the inverting amplifier 54 is larger than the voltage of the hold capacitor of the peak hold circuit, the hold capacitor is charged. On the other hand, when the input from the inverting amplifier 54 is equal to or lower than the voltage of the hold capacitor, the voltage of the hold capacitor is held. From the peak hold / reset circuit 55 (peak hold circuit), the voltage of the hold capacitor (input from the inverting amplifier 54) is impedance-converted and output. The reset circuit is a circuit for turning on / off a reset switch provided in parallel with the hold capacitor. When a reset signal is input to the reset circuit, a signal is input from the reset circuit to the reset switch, and the reset switch is turned on. When the reset switch is turned on, the electric charge accumulated in the hold capacitor is released (discharged).

  The peak detection circuit 52 includes a high-pass filter circuit 56 that passes a high-frequency component of the current value of the applied current, an inverting amplifier 57 that amplifies the output of the high-pass filter circuit 56 and inverts its polarity, and the output of the inverting amplifier 57. And a peak hold / reset circuit 58 that holds and outputs the maximum value.

  The high pass filter circuit 56 has a circuit configuration similar to that of the differentiation circuit.

  The inverting amplifier 57 has a widely known configuration, and a resistor for eliminating the influence of the bias current is connected to the “+” terminal.

  The peak hold / reset circuit 58 is a combination of a general peak hold circuit and a reset circuit. When the input from the inverting amplifier 57 is larger than the voltage of the hold capacitor of the peak hold circuit, the hold capacitor is charged. On the other hand, when the input from the inverting amplifier 57 is equal to or lower than the voltage of the hold capacitor, the voltage of the hold capacitor is held. From the peak hold / reset circuit 58 (peak hold circuit), the voltage of the hold capacitor (input from the inverting amplifier 57) is impedance-converted and output. The reset circuit is a circuit for turning on / off a reset switch provided in parallel with the hold capacitor. When a reset signal is input to the reset circuit, a signal is input from the reset circuit to the reset switch, and the reset switch is turned on. When the reset switch is turned on, the electric charge accumulated in the hold capacitor is released (discharged).

  Each time the on-instruction signal is output from the plasma reactor control device 31 to the gate drive circuit 13 (see FIG. 2), each of the peak hold / reset circuits 55 and 58 receives the on-instruction signal. The reset signal is input within a period from the output to the output of the off instruction signal. Thereby, the current integration circuit 51 outputs an integration current value during a period in which the applied current value takes a positive value every time one pulse of the pulse-wave secondary voltage is output from the plasma reactor power supply device 7. The peak detection circuit 52 outputs a peak current value during a period in which the applied current value takes a positive value.

  As shown in FIG. 3, the applied voltage estimation unit 42 receives the integrated current value from the current integration / peak detection circuit 41 (current integration circuit 51). The non-volatile memory (ROM, flash memory, EEPROM, etc.) of the plasma reactor control device 31 stores the relationship between the integrated current value and the applied voltage value in the form of a two-dimensional map. Based on the relationship, the applied voltage estimation unit 42 acquires an applied voltage value corresponding to the integrated current value input from the current integration / peak detection circuit 41 and applies the applied voltage value between the discharge electrodes 3 and 4. The applied voltage value is estimated.

  The target voltage setting unit 43 sets a target value (target voltage value) of an applied voltage applied between the discharge electrodes 3 and 4 of the plasma reactor 1. Specifically, the target voltage setting unit 43 acquires the air-fuel ratio of the exhaust gas discharged from the engine (not shown), and obtains the PM amount contained in the unit volume of the exhaust gas from the air-fuel ratio. And the target voltage setting part 43 sets the target voltage value according to the calculated | required PM amount.

  The subtracting unit 44 subtracts the applied voltage value estimated by the applied voltage estimating unit 42 from the target voltage value set by the target voltage setting unit 43.

  The signal output unit 45 controls the input of the on instruction signal and the off instruction signal to the gate drive circuit 13 so that the subtraction value calculated by the subtraction unit 44 approaches 0, and turns on / off the switching element 12 for energization control. Control off.

  The abnormal discharge determination unit 46 receives the integrated current value of the applied current and the peak current value of the applied current from the current integration / peak detection circuit 41. The abnormal discharge determination unit 46 determines the occurrence of abnormal discharge in the plasma reactor 1 based on the integrated current value and the peak current value input from the current integration / peak detection circuit 41. If it is determined that an abnormal discharge has occurred, a command for stopping the discharge in the plasma reactor 1 or reducing the intensity of the discharge is input to the signal output unit 45. In this case, the signal output unit 45 controls the input of the on instruction signal and the off instruction signal to the gate drive circuit 13 in response to a command from the abnormal discharge determination unit 46, and turns on / off the energization control switching element 12. Control.

<Abnormal discharge determination processing>
FIG. 5 is a flowchart showing the flow of the abnormal discharge determination process.

  The abnormal discharge determination unit 46 executes the abnormal discharge determination process shown in FIG. 5 in order to determine the occurrence of abnormal discharge in the plasma reactor 1.

  In the abnormal discharge determination process, first, it is determined whether or not the integrated current value of the applied current input from the current integration / peak detection circuit 41 is equal to or greater than a preset integrated abnormality determination value (step S1).

  If the integrated current value is not greater than or equal to the integrated abnormality determination value, that is, if the integrated current value is less than the integrated abnormality determination value (NO in step S1), then the peak of the applied current input from the current integration / peak detection circuit 41 It is determined whether or not the current value is greater than or equal to a preset peak abnormality determination value (step S2).

  If the peak value is not equal to or greater than the peak abnormality determination value (NO in step S2), it is determined again whether or not the integrated current value of the applied current is equal to or greater than the integration abnormality determination value (step S1). As a result, the determination of whether or not the integrated current value of the applied current is equal to or greater than the integrated abnormality determination value and the determination of whether or not the peak current value of the applied current is equal to or greater than the peak abnormality determination value are determined by one of those determinations. Repeat until affirmed.

  Then, an integrated current value equal to or greater than the accumulated abnormality determination value is input from the current accumulation / peak detection circuit 41 (YES in step S1), or a peak current value equal to or greater than the peak abnormality determination value from the current accumulation / peak detection circuit 41 Is input (YES in step S2), it is determined that an abnormal discharge has occurred in the plasma reactor 1 (step S3), and the abnormal discharge determination process is terminated.

<Effect>
As described above, the plasma reactor control device 31 detects the applied current applied to the discharge electrodes 3 and 4 of the plasma reactor 1 and integrates it over a period in which the current value takes a positive value. The accumulated current value is acquired. Further, a peak current value that is a peak value of the applied current in a period in which the applied current value takes a positive value is acquired.

  If at least one of the accumulated current value is equal to or greater than a predetermined accumulated abnormality determination value or the peak current value is equal to or greater than a predetermined peak abnormality determination value, it is determined that an abnormal discharge has occurred in the plasma reactor 1. The Specifically, when an abnormal discharge occurs in the plasma reactor 1, an integrated current value different from that during normal discharge is obtained, and when the integrated current value is equal to or greater than an integrated abnormality determination value, the occurrence of the abnormal discharge is determined. Is done. Even if an abnormal discharge occurs in the plasma reactor 1, even if the integrated current value is substantially the same as the integrated current value during normal discharge and is less than the integrated abnormality determination value, the discharge electrodes 3 and 4 are caused by abnormal discharge. When the peak current value of the applied current flowing through the current exceeds the peak abnormality determination value, the occurrence of the abnormal discharge is determined.

  Therefore, even if an abnormal discharge occurs in the plasma reactor 1 without providing a voltage sensor for detecting the voltage applied to the discharge electrodes 3 and 4 of the plasma reactor 1, the occurrence of the abnormal discharge can be determined. .

<Modification>
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  For example, instead of the peak current value of the applied current, the time change rate of the applied current may be acquired. When an abnormal discharge occurs in the plasma reactor 1, the applied current flowing through the discharge electrodes 3 and 4 of the plasma reactor 1 changes sharply. In particular, the rate of time change immediately before the applied current reaches the peak current value is significantly different from that during normal discharge. Therefore, when the time change rate of the applied current exceeds a predetermined change rate abnormality determination value, the occurrence of abnormal discharge may be determined.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

1 Plasma reactor 3 Discharge electrode (electrode)
4 Discharge electrode (electrode)
31 Control device for plasma reactor 32 Current sensor 46 Abnormal discharge determination unit (abnormal discharge determination means)
51 Current integration circuit (current integration means)
52 Peak detection circuit (peak value acquisition means)

Claims (1)

Current integrating means for integrating the value of the applied current applied to the electrode of the plasma reactor over a predetermined period;
Peak value acquisition means for acquiring a peak value of the applied current in the predetermined period;
In the plasma reactor, when the integrated current value by the current integrating means is equal to or greater than a predetermined accumulated abnormality determination value, or when the peak value acquired by the peak value acquiring means is equal to or greater than a predetermined peak abnormality determination value An apparatus for controlling a plasma reactor, comprising: an abnormal discharge determining means for determining occurrence of abnormal discharge.

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