Device and method for maintaining pulse power control at different plasma discharge stages

Abstract

This invention provides a device and method for controlling pulse power at different plasma discharge stages. This invention can effectively fit the discharge characteristics of the arc initiation and sustaining stages of an arc discharge, providing a voltage amplitude of n*U during the arc initiation stage. M The high-voltage pulse power enables the air jet to rapidly initiate an arc with high voltage and low current, providing a voltage amplitude of U during the arc-holding phase. M The low-pressure pulse power allows the air jet to travel for a longer period of time. t retainer During the arc-holding period, it maintains low voltage, high current, and low power operation, thereby significantly reducing discharge power loss and improving discharge efficiency while ensuring the intensity of air jet discharge. Simultaneously, it reduces discharge heat generation, ensuring stable operation of the air jet device for extended periods. The use of modular small batteries in series for power supply saves system space and weight, enabling the portable rechargeable air jet device to have a longer battery life and improved standby time.

Description

Technical Field

[0001] This invention belongs to the field of plasma discharge and relates to a device and method for controlling pulse power at different plasma discharge stages. Background Technology

[0002] Low-temperature plasma discharge forms mainly include: dielectric barrier, corona, glow discharge, microwave, sliding arc, and jet discharge. However, regardless of the discharge form, the discharge electrodes share a common characteristic regarding the pulse rate of the pulse drive, namely, a higher pulse power voltage amplitude U is required before the discharge occurs. ignition Achieving gas breakdown (ignition for short), followed by a small discharge voltage amplitude U. retainer It can still maintain the discharge state of gas breakdown (referred to as maintenance), and U exists. ignition Significantly greater than U retainer Due to the special power requirements of discharge plasma, if the ignition pulse voltage amplitude is maintained consistently under normal operating conditions, it will cause the discharge electrodes to overheat, resulting in local breakdown. This will also reduce the discharge efficiency of the entire plasma source system and cause system reliability issues.

[0003] Low-temperature plasma generated by electric arc discharge, due to its high energy density, is widely used in fuel reforming, assisted combustion, organic pollutant removal, wastewater treatment, material surface modification, and sterilization. The segmentation of the ignition-sustainment discharge stages is particularly pronounced, characterized by high voltage, low current, and short duration during the arc initiation stage, and low voltage, high current, and long duration during the arc sustaining stage. Air jet arc discharge, using air as the working gas, offers advantages such as simple electrode structure, low pulse drive voltage, high concentration of active particles in the discharge plasma, high particle activity, significant treatment effect, and high efficiency, making it the discharge form with the greatest potential for industrial application. Commonly used driving power supplies for air jet arc dischargers include high-voltage DC power supplies, unipolar pulse power supplies, and high-frequency AC pulse power supplies. Among them, high-voltage DC power supplies have the best driving effect, strong discharge, high concentration of active particles, and high energy intensity, but they also cause severe electrode heating, thermal erosion, and low energy efficiency. High-frequency AC pulse power supplies drive arc discharges better than unipolar pulse power supplies, achieving discharge effects comparable to high-voltage DC drives. However, traditional high-frequency AC power supplies cannot well match the special load characteristics of high voltage-low current-short time during the arc initiation stage and low voltage-high current-long time during the arc holding stage. This leads to excessive power loss and unnecessary heat loss during arc discharge. This not only limits the application of air jet arc discharges in thermally unfavorable environments but also causes faster damage to the air jet arc discharge electrodes. In addition, the extra energy waste also limits the standby time of portable rechargeable air jet plasma sources.

[0004] To meet the high ignition and arc-holding voltage requirements of air jet arc discharge, existing high-frequency AC pulse power supplies are designed to output high-pulse voltage amplitudes under normal conditions. However, this design leads to a short circuit during the arc-holding process, forcing the high-frequency AC pulse power supply to output its maximum short-circuit current. This results in power redundancy in the arc electrode discharge, making it difficult to maintain low power loss under normal driving conditions. Consequently, the entire plasma source suffers from low system efficiency, high losses, inability to operate under normal conditions, and low reliability. A possible solution is to separate the ignition and arc-holding processes by designing and developing two high-frequency power supply units with different functions. The ignition power supply unit outputs a high-pulse voltage amplitude but has low overall power, while the arc-holding power supply unit outputs a low-pulse voltage amplitude but has a higher output current. This effectively solves the power redundancy problem in arc electrode discharge. However, using two separate drive power supply systems results in a bulky plasma source device, suitable only for high-power arc electrode discharge applications and unsuitable for portable, handheld plasma source devices requiring high integration. Summary of the Invention

[0005] 1. The technical problem to be solved:

[0006] The power redundancy problem exists in arc discharge driven by high-frequency AC power supply.

[0007] 2. Technical Solution:

[0008] To address the above problems, this invention provides a pulse power regulation device for maintaining different plasma discharge stages, comprising a power supply, the power supply including a control system, the control system, an inverter drive unit, a high-frequency inverter unit, and a high-voltage transformer connected in sequence, a multi-level bus adjustment unit provided between the control unit and the high-frequency inverter unit, one end of the multi-level bus adjustment unit being connected to the high-frequency inverter unit for controlling the input voltage Udc of the inverter unit, and the other end being connected to the fiber optic drive unit, the other end of the fiber optic drive unit being connected to the control unit.

[0009] The multi-level bus regulation includes a battery module that supplies power to the entire device. The battery module consists of N batteries with the same voltage connected in series. Each battery corresponds to a level-controlled MOSFET switch. The control system controls the nth switch to turn on by changing the control signals of the N switches, where n ≤ N, thereby controlling the output DC voltage Udc of the N batteries to power the high-frequency inverter unit. n is the actual number of batteries supplying power to the inverter unit.

[0010] Each MOSFET switch is connected in series with a reverse current protection diode.

[0011] The high-frequency inverter unit uses a full-bridge inverter circuit to invert the input DC power and output high-frequency AC power, which is then boosted by a high-voltage transformer to drive the air jet arc discharge device.

[0012] A control method based on the aforementioned pulse power control device for maintaining different plasma discharge stages is disclosed. During the air jet arc ignition stage, a high-frequency AC pulse power supply provides a high-voltage arc ignition pulse with a duration of n*UM, enabling the air jet to rapidly ignite at high voltage and low current. After successful arc ignition, the air jet enters the arc sustaining stage. The high-frequency AC pulse power supply is controlled to output a low-voltage arc sustaining pulse with a duration of UM, allowing the air jet to maintain low voltage, high current, and low power operation during the arc sustaining time of UM. Then, the next cycle begins. The high-voltage amplitude n*UM is adjusted by controlling the nth switch in the multi-level bus adjustment unit to conduct during the arc ignition pulse time. Tignition is the duration of the arc ignition pulse in one discharge cycle; tretainer is the duration of the arc sustaining pulse in one discharge cycle; tcharge is the duration of one discharge cycle; td is the dead time when different switches in the multi-level bus adjustment unit are on; UM is the rated output voltage of a battery; and Upuse is the pulse voltage output by the high-frequency AC pulse power supply.

[0013] The duration of a discharge cycle, tcharge, and the duration of the arc initiation and arc holding phases within a discharge cycle, tignition and tretainer, remain unchanged.

[0014] 3. Beneficial effects:

[0015] This invention's segmented frequency conversion controlled high-frequency AC pulse power supply can drive air jet arc discharge without the need for an additional power resistor. Furthermore, it eliminates the need for an additional power resistor and utilizes modular small batteries in series for power supply, significantly saving system space and weight. The power savings also extend the battery life of portable rechargeable air jet devices, further improving the standby time of small, portable air jet discharge devices. Due to lower discharge heat generation, this invention is suitable for applications where air jet discharge heat is unfavorable. Simultaneously, the reduced heat generation also results in less electrode wear in the air jet device, extending its lifespan using the same materials. Attached Figure Description

[0016] Figure 1 It is a system control block diagram.

[0017] Figure 2 This is a schematic diagram of a modular amplitude modulation high-frequency AC power supply circuit.

[0018] Figure 3 This is a schematic diagram of the system's switching timing control.

[0019] Figure 4 This is a schematic diagram of the multi-level amplitude modulation control output pulse principle.

[0020] Figure 5 This is a flowchart of the modular amplitude modulation control logic.

[0021] Figure 6 This is a structural diagram of an air jet arc discharge electrode.

[0022] Figure 7 The DC switching transistor output voltage U when the inverter bridge is not connected. dc .

[0023] Figure 8 It is the output voltage U of the DC switching transistor when connected to the inverter bridge. dc .

[0024] Figure 9 It is the output voltage U of the DC switching transistor from 0-14ms. dc and high-frequency AC output voltage U pulse .

[0025] Figure 10 It is the output voltage U of the DC switching transistor in 4-8ms. dc and high-frequency AC output voltage U pulse .

[0026] Figure 11 It shows the discharge voltage-current and DC input voltage waveforms.

[0027] Figure 12 It is a discharge image. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings.

[0029] Currently, most high-frequency AC pulse power supplies used for air jet arc discharge employ a fixed-frequency, fixed-amplitude driving method. During the arc initiation phase of air jet discharge, the voltage is high, and a power resistor is typically added to the load side to limit the discharge current. During the arc sustaining phase, the power resistor absorbs excessively high voltage. However, the power resistor consumes a significant amount of power and generates heat, reducing the efficiency of air jet discharge and greatly limiting its application. The segmented frequency conversion control high-frequency AC pulse power supply proposed in this patent effectively avoids this problem, driving air jet arc discharge without the need for a power resistor.

[0030] To address the different requirements for pulsed power discharge voltage amplitude in the ignition and sustaining states of plasma discharge, a modular amplitude-modulated high-voltage AC pulse power supply is proposed, which provides power in one discharge cycle. t chargeInternally, it is divided into two pulse power drive modes: high-voltage ignition pulse n*U M Arc-holding pulse U under low voltage M With the inverter circuit frequency remaining constant, it periodically outputs high-voltage arc-starting pulses and low-voltage arc-sustaining pulses, thereby reducing the power redundancy of the entire power supply.

[0031] like Figure 1 As shown, the power supply includes a control unit, an optical fiber drive unit, a multi-level bus regulation unit, an inverter drive unit, a high-frequency inverter unit, and a high-voltage transformer. The multi-level bus regulation unit on the left is the core of the entire power supply, controlling the input voltage U of the high-frequency inverter unit by changing the control signals of the switching transistors Q1~QN. dc This controls the output pulse amplitude of the entire power supply.

[0032] like Figure 2 and Figure 3 As shown, the multi-level bus regulation unit consists of a battery, a level control switch, and an anti-reverse current diode. N voltages are identical (all U). M Small batteries are connected in series to form a multi-level power supply system, providing the entire unit with a multi-adjustable DC voltage. Replacing the traditional large portable rechargeable plasma source with N modular small batteries not only allows for flexible adjustment of the number of small batteries to reduce the overall size and weight of the device according to application needs, but also greatly saves energy consumption and increases the standby time of the portable rechargeable plasma source device.

[0033] Modular amplitude modulation maintains the cycle of one discharge. t charge Without changing the average power per cycle, the arc-starting pulse voltage within a single cycle is n times U. M The arc holding voltage is U M Adjust the number of DC input modules n and the voltage U of a single DC input module. M The discharge intensity of the air jet electrode is adjusted to ensure that the entire plasma source device has functions such as electrode temperature control, discharge intensity control, and active particle concentration control under different surface treatment applications.

[0034] The modular power supply section is followed by level-controlled MOSFETs Q1~QN. By changing the control signals of the N switches, the nth switch can be turned on (n≤N), thus controlling the DC voltage U output from the n batteries. dcPower is supplied to the inverter bridge. 'n' represents the actual number of batteries supplying the inverter unit, determined by which switch is turned on during the arc initiation phase. The proposed modular amplitude modulation control method controls the voltage change of the series-connected modular DC power supply input to the inverter bridge simply by regulating the on / off state of N switches. This achieves the voltage transition between the arc initiation and arc sustaining phases of air jet arc discharge. Changing the switch control signals alters the amplitude of the high-frequency AC voltage output on the high-voltage side to adapt to the discharge requirements of air jet devices in different scenarios, thus facilitating the widespread application of air jet plasma source devices.

[0035] A reverse current protection diode is connected in series after each MOSFET switch to prevent reverse current from causing excessive directional overvoltage that could damage the switch. This also isolates the multilevel bus unit from the inverter unit.

[0036] The inverter unit uses a classic full-bridge inverter circuit to invert the input DC power and output high-frequency AC power, which is then stepped up by a high-voltage transformer to drive an air jet arc discharge device.

[0037] like Figure 4 As shown, with 2 times U M Taking the output as an example, during the arc initiation stage of the air jet, the high-frequency AC pulse power supply provides continuous... t ignition The time amplitude is n*U M The high-voltage arc ignition pulse is applied; after successful arc ignition, the arc holding phase begins, controlling the continuous output of the high-frequency AC pulse power supply. t retainer The time amplitude is U M A low-voltage arc-holding pulse is applied, followed by the next cycle, where the high-voltage amplitude is n*U. M The adjustment can be achieved by controlling the nth switching transistor in the multi-level bus adjustment unit to conduct during the arc ignition pulse time. (See diagram:) t ignition The duration of the arc-starting pulse in one discharge cycle; t retainer The duration of the arc-holding pulse in one discharge cycle; t charge The duration of one discharge cycle; t d U represents the dead time when different switching transistors of the multi-level bus regulating unit are turned on; M U is the rated output voltage of a battery; pulse It outputs pulse voltage for high-frequency AC pulse power supply.

[0038] like Figure 5 As shown, the duration of one discharge cycle t charge The duration of the arc initiation and arc sustaining phases in a discharge cyclet ignition , t retainer Keeping the inverter input voltage U constant, the control signals of the switching transistors of the multi-level bus regulating unit during the arc initiation and arc sustaining phases within a single cycle are adjusted to control the switching transistors that are turned on in the two phases, thereby regulating the inverter input voltage U. dc By fitting the load characteristics of air jet arc discharge, while ensuring stable discharge of the air jet, the discharge current during the arc initiation stage and the discharge voltage during the arc holding stage are reduced, thereby reducing the energy consumption and heat loss of the entire plasma source device and improving the device's endurance.

[0039] Arc discharge has the load operating characteristics of high voltage, low current, and low power during the arc initiation stage, and low voltage, high current, and low power during the arc sustaining stage. In order to ensure that the arc electrode can discharge successfully, the minimum discharge voltage of traditional high-frequency AC pulse power supply must be greater than the arc initiation voltage of the arc discharge electrode. However, during the long-lasting arc sustaining stage, the power loss mode of high voltage, high current, and high power will be maintained, and the lost power will be released in the form of heat generation, resulting in excessively high temperature of the discharge electrode. This is not conducive to long-term normal operation, will affect the service life of the air jet discharge electrode, and will also limit the application of air jet arc discharge.

[0040] The modular amplitude modulation control method proposed in this invention can well fit the discharge characteristics of the arc initiation and sustaining stages of air jet arc discharge, considering the load characteristics of air jet arc discharge. Figure 2 As shown, the voltage amplitude during the arc initiation stage is given as n*U M The high-voltage pulse power enables the air jet to rapidly initiate an arc with high voltage and low current, providing a voltage amplitude of U during the arc-holding phase. M The low-pressure pulse power allows the air jet to travel for a longer period of time. t retainer During the arc holding time, it maintains low voltage-high current-low power operation, thereby greatly reducing discharge power loss and improving discharge efficiency while ensuring the intensity of air jet discharge, and reducing discharge heat generation, so as to ensure that the air jet device can operate stably for a long time.

[0041] This invention uses, for example Figure 6 The air jet arc discharge device shown was used to test the proposed segmented frequency conversion high-voltage AC pulse power supply. The air jet electrode mainly consists of three parts: unit 1 is a needle-type high-voltage electrode, unit 2 is a ground electrode and also serves as the outer shell of the air jet device, and unit 3 is a central support that fixes the high-voltage electrode unit 1 in a central position at all times.

[0042] The experiment controlled two DC power supply modules to conduct an amplitude-modulated high-frequency AC driven air jet arc discharge experiment. The proposed modular amplitude modulation control technology was verified by the discharge voltage and current waveforms and the amplitude-modulated DC voltage input to the inverter.

[0043] Depend on Figure 7 and Figure 8 It can be seen that controlling the DC switching transistor to turn on and off enables the amplitude modulation output voltage of the two modules to switch between 6-12V, which is consistent with the expected modular amplitude modulation input voltage. Figure 8 Compare Figure 7 The voltage drop time is longer because of stray capacitance introduced by the MOSFET switches in the inverter bridge, which lengthens the voltage drop edge. Simultaneously, high-frequency inverter interference also contributes to this. Figure 8 The waveform may have jagged or volatile patterns; these are all normal phenomena.

[0044] Depend on Figure 9 and Figure 10 It can be seen that, whether from multiple discharge cycles or a single discharge cycle, the modular amplitude modulation high-frequency AC output voltage meets expectations. The periodic arc-starting voltage and arc-holding voltage are output alternately to fit the characteristics of the air jet arc discharge load.

[0045] Figure 11 Voltage-current and DC input voltage U for driving air jet arc discharge with modular amplitude-modulated high-frequency AC power supply dc Waveform, Figure 12 For discharge images, by Figure 12 As can be seen from the proposed modular amplitude modulation high-frequency AC power supply control method, it can drive air jet arc discharge, and the voltage during discharge fits well with the characteristics of the arc discharge load, reducing the voltage during the arc holding stage, thereby reducing energy consumption and improving energy utilization efficiency.

Claims

1. A device for regulating pulse power at different plasma discharge stages, comprising a power supply, characterized in that: The power supply includes a control system, an inverter drive unit, a high-frequency inverter unit, and a high-voltage transformer connected in sequence. A multi-level bus regulation unit is provided between the control system and the high-frequency inverter unit. One end of the multi-level bus regulation unit is connected to the high-frequency inverter unit and is used to control the voltage U input to the inverter unit. dc The other end is connected to the fiber optic drive unit, and the other end of the fiber optic drive unit is connected to the control system. The multi-level bus adjustment unit includes a battery module, which supplies power to the entire device. The battery module consists of N batteries with the same voltage connected in series. Each battery corresponds to a level-controlled MOSFET switch. The control system controls the nth switch to turn on by changing the control signals of the N switches, where n ≤ N, thereby controlling the output DC voltage U of the N batteries. dc The high-frequency inverter unit is powered by a battery, where n is the actual number of batteries that power the inverter unit. Each MOSFET switch is connected in series with an anti-reverse current diode.

2. The pulse power control device for maintaining different plasma discharge stages as described in claim 1, characterized in that: The high-frequency inverter unit uses a full-bridge inverter circuit to invert the input DC power and output high-frequency AC power, which is then boosted by a high-voltage transformer to drive the air jet arc discharge device.

3. A control method based on the pulse power control device for maintaining different plasma discharge stages as described in claim 1 or 2, characterized in that: During the arc initiation stage of the air jet, the high-frequency AC pulse power supply provides continuous... t ignition The time amplitude is n*U M The high-voltage arc-initiating pulse enables the air jet to rapidly ignite with high voltage and low current; after successful arc ignition, it enters the arc-holding stage, controlling the continuous output of the high-frequency AC pulse power supply. t retainer The time amplitude is U M The low-pressure arc-holding pulse causes the air jet to... t retainer During the arc-holding period, it maintains low voltage-high current-low power operation, and then enters the next cycle, where the high voltage amplitude n*U M Adjustment is achieved by controlling the nth switching transistor in the multi-level bus adjustment unit to conduct during the arc ignition pulse time. t ignition The duration of the arc-starting pulse in one discharge cycle; t retainer The duration of the arc-holding pulse in one discharge cycle; t charge The duration of one discharge cycle; t d U represents the dead time when different switching transistors of the multi-level bus regulating unit are turned on; M U is the rated output voltage of a battery; pulse It outputs pulse voltage for high-frequency AC pulse power supply.

4. The control method as described in claim 3, characterized in that: Duration of one discharge cycle t charge The duration of the arc initiation and arc sustaining phases in a discharge cycle t ignition , t retainer It remains unchanged.

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