Segmented Frequency Conversion Control Method Applied to High-Frequency AC Pulse Power Supply for Arc Discharge

Abstract

The present invention provides a segmented frequency conversion control method applied to an arc discharge high-frequency AC pulse power supply. The arc ignition pulse f at high frequency s_ignition , and the arc holding pulse f at low frequency s_retainer . At the same time, the amplitude of the high-frequency AC pulse remains unchanged. During the arc ignition stage of the air jet, the high-frequency AC pulse power supply outputs the pulse power of high frequency f s_ignition , and maintains it for t ignition time. After successful arc ignition and entering the arc holding stage, the high-frequency AC pulse power supply is controlled to output the pulse power of low frequency f s_retainer , and maintains it for t retainer time until the discharge extinguishes and enters the next cycle. The present invention can complete the control of air jet arc discharge only by adjusting the form of the pulse power output by the power supply, and can meet the different air jet discharge requirements in different application scenarios, which is beneficial to the integration, miniaturization and portability of the plasma source whole machine equipment.

Description

Technical Field

[0001] The present invention belongs to the field of arc discharge and relates to a segmented frequency conversion control method applied to a high-frequency alternating current pulse power supply for arc discharge. Background Art

[0002] Air jet arc discharge is a typical form of arc discharge. During its arc ignition stage, a strong pulse power is required to excite enough seed electrons to achieve the breakdown of the air between the electrodes. This strong pulse power requires the high-frequency alternating current pulse power supply to output a pulse voltage amplitude high enough to achieve the ignition breakdown of the air between the electrodes. After the arc is formed, it can be equivalent to a low-impedance current path. Under the action of the air flow, the arc will be blown out along the electrode gap. During this arc maintenance process, a very high pulse maintenance voltage is not required, and only a certain arc maintenance current is needed. Therefore, for the arc electrode discharge of the air jet, relative to the driving pulse power supply, it has the load working characteristics of high voltage - low current - low power for arc ignition and low voltage - high current - low power for arc maintenance.

[0003] In order to meet the requirement of a high ignition arc voltage for air jet arc discharge in the existing high-frequency alternating current pulse power supply, when designing the power supply, a high-frequency alternating current pulse power is output according to the normal state with a high pulse voltage amplitude. This design scheme will cause the high pulse voltage to be short-circuited during the arc maintenance process, forcing the high-frequency alternating current pulse power supply to output the maximum short-circuit current, thus forming a power redundancy problem in arc electrode discharge, that is, it is very difficult to maintain a low power loss under normal driving working conditions. The entire plasma source has problems such as low system efficiency, large loss, inability to operate normally, and low reliability. The solution to the related technical problems can be to separate the ignition process and the arc maintenance process, and design and develop two different functional high-frequency power supply units respectively, that is, design the ignition power supply unit to output a high pulse voltage amplitude but a small overall power, and the arc maintenance power supply unit to output a low pulse voltage amplitude but a high output current, which can well solve the power redundancy problem of arc electrode discharge. However, using two sets of drive power systems, the entire plasma source device is bulky and is suitable for high-power arc electrode discharge occasions, and is not suitable for the occasions where high volume integration is required, such as portable plasma source devices. Summary of the Invention

[0004] 1. Technical problems to be solved:

[0005] It is very difficult for the existing high-frequency alternating current pulse power supply to maintain a low power loss under normal driving working conditions. The entire plasma source has problems such as low system efficiency, large loss, inability to operate normally, and low reliability.

[0006] 2. Technical solutions:

[0007] To solve the above problems, the present invention provides a segmented frequency conversion control method applied to an arc discharge high-frequency AC pulse power supply. The envelope frequency f pulse remains unchanged. The envelope frequency f pulse is divided into two forms of pulse power drive. The arc ignition pulse f s_ignition at high frequency and the arc-maintaining pulse f s_retainer at low frequency. Meanwhile, the amplitude of the high-frequency AC pulse remains unchanged. During the arc ignition stage of the air jet, the high-frequency AC pulse power supply gives the pulse power of high frequency f s_ignition and maintains it for t ignition time. After successful arc ignition and entering the arc-maintaining stage, control the high-frequency AC pulse power supply to output the pulse power of low frequency f s_retainer and maintain it for t retainer time until the discharge extinguishes and enters the next cycle. Among them, the frequency f s_ignition is more than ten times the frequency f s_retainer .

[0008] The number of arc ignition pulses in a single cycle is N ignition , and the number of arc-maintaining pulses in a single cycle is N retainer . Set the regulation ratio K . By adjusting the number of arc ignition pulses N ignition and the number of arc-maintaining pulses N retainer in a single cycle, the value of the regulation ratio K is further regulated to achieve the regulation of the discharge intensity of the air jet electrode.

[0009] The high-frequency AC pulse power supply includes a control circuit and a drive circuit. A filter is provided at the front end of the power supply. The filter is respectively connected to an auxiliary source and a rectifier circuit. The auxiliary source is connected to the control circuit. The control circuit is connected to the drive circuit. The drive circuit is connected to an IGBT full-bridge inverter circuit. The IGBT full-bridge inverter circuit is connected to an LC filter circuit. The LC filter circuit is connected to a high-voltage transformer. The auxiliary source outputs stable direct current for powering various chips in the entire power supply circuit. The control circuit outputs different control signals to obtain target pulses. The drive circuit converts the control signals given by the control circuit into drive signals that can drive the IGBTs in the inverter circuit. The rectifier circuit rectifies the industrial frequency alternating current filtered by the pre-filter to provide high-quality DC voltage for the inverter circuit. The IGBT full-bridge inverter circuit inversely converts the direct current rectified by the rectifier circuit into the high-frequency alternating current of the target output according to different control signals. The capacitor in the LC filter circuit cooperates with the primary inductor of the transformer to filter the pulses output by the inverter circuit. After filtering, the pulses are then boosted by the transformer into a segmented frequency conversion type high-voltage alternating current that can drive arc discharge.

[0010] The high-frequency AC pulse power supply further includes a protection circuit. The protection circuit collects the high-voltage side current as feedback. When the power supply has an overcurrent or open circuit, it cuts off the power supply of the control circuit to force the power supply to stop working, protecting the load and the power supply.

[0011] For the experiment of the segmented variable-frequency high-voltage AC pulse power supply, an air jet arc discharge device is used. The air jet arc discharge device includes a needle-shaped high-voltage electrode (1) and a ground electrode (2). The ground electrode (2) also serves as the outer shell, and the central support (3) fixes the high-voltage electrode (1) at the central position all the time.

[0012] 3. Beneficial effects:

[0013] 1) The segmented variable-frequency control high-frequency AC pulse power supply proposed by the present invention can well avoid this problem and drive the air jet arc discharge without adding a power resistor.

[0014] 2) When the segmented variable-frequency high-frequency AC power supply proposed by this patent drives the air jet discharge, no additional power resistor is required. It can not only save the space and weight occupied by the system, but also save power, enabling the rechargeable portable air jet device to operate for a longer time and further improving the standby time of the small portable air jet discharge device.

[0015] 3) When the segmented variable-frequency high-frequency AC power supply proposed by this patent drives the air jet discharge device, the heat generation during discharge is lower, which is friendly to some application scenarios where the heat of air jet discharge is unfavorable. At the same time, due to less heat generation, the electrode loss of the air jet device is also weaker, and the service life of the air jet device can be extended using the same materials. Description of the drawings

[0016] Figure 1 is the structure diagram of the segmented variable-frequency high-voltage AC power supply.

[0017] Figure 2 is the schematic diagram of the segmented variable-frequency control method based on the arc-type air jet discharge electrode.

[0018] Figure 3 is the control logic flow chart.

[0019] Figure 4 is the structure diagram of the air jet arc discharge electrode.

[0020] Figure 5 is the no-load voltage waveform of the high pulse frequency - fixed frequency control signal output.

[0021] Figure 6 is the load voltage and current waveform of the high pulse frequency - fixed frequency control signal output.

[0022] Figure 7 is the discharge image under the discharge waveform condition of the high pulse frequency - fixed frequency control signal output.

[0023] Figure 8 is the no-load voltage waveform of the low pulse frequency - fixed frequency control signal output.

[0024] Figure 9 is the loaded voltage and current waveforms of the low pulse frequency - fixed frequency control signal output.

[0025] Figure 10 is the discharge image under the discharge waveform condition of the low pulse frequency - fixed frequency control signal output.

[0026] Figure 11 is the no-load voltage waveform of the segmented variable frequency control signal output.

[0027] Figure 12 is the loaded voltage and current waveforms of the segmented variable frequency control signal output.

[0028] Figure 13 is the discharge image under the discharge waveform condition of the segmented variable frequency control signal output. Detailed implementation mode

[0029] The present invention will be described in detail below with reference to the accompanying drawings.

[0030] The segmented variable frequency control method for an arc discharge high-frequency AC pulse power supply proposed by the present invention controls the inverter bridge in a manner of alternately circulating control of high-frequency signals and low-frequency signals, and further controls the output high-voltage AC pulses to be output alternately at high frequency and low frequency.

[0031] As Figure 2 shown, during the air jet arc starting stage, the high-frequency AC pulse power supply gives a pulse power of high frequency f s_ignition and maintains it for a time t ignition . After the arc starting ignition is successful and enters the arc holding stage, the high-frequency AC pulse power supply is controlled to output a pulse power of low frequency f s_retainer and maintains it for a time t retainer . When the discharge extinguishes, it enters the next cycle, where the frequency f s_ignition is more than ten times the frequency f s_retainer . At the same time, the amplitude of the high-frequency AC pulse remains unchanged, thereby reducing the power redundancy of the entire power supply. Without increasing the pulse voltage amplitude, only by increasing the ignition pulse frequency within the ignition time, the ignition function of the air jet arc electrode is realized, the insulation performance requirement is not high, the whole machine can be further compacted, and the safety and economy of the whole machine device are improved.

[0032] The number of arc starting ignition pulses in a single cycle is N ignition , and the number of arc holding pulses in a single cycle is N retainer . Let the regulation ratio be K. By adjusting the number of arc starting pulses in a single cycle to be Nignition 、 The number N of holding arc pulses retainer , and then adjust the ratio K value to achieve the regulation of the discharge intensity of the air jet electrode. Ensure that the entire plasma source device has functions such as electrode temperature regulation, discharge intensity regulation, and active particle concentration under different surface treatment applications.

[0033] Such as Figure 3 shown, the envelope frequency f pulse remains unchanged. When increasing the number of arc ignition pulses N ignition and decreasing the number of holding arc pulses N retainer , the regulation ratio K value increases. Conversely, the regulation ratio K value decreases. When the regulation ratio K value increases, the discharge becomes stronger. When the regulation ratio K value decreases, the discharge becomes weaker.

[0034] The higher the frequency of the drive power supply, the easier the discharge of the plasma electrode and the better the discharge effect; while when the frequency of the drive power supply is low, the plasma discharge is weak and less active substances are generated, and even there may be no discharge. However, the frequency of the drive power supply is not the higher the better. The most important factor restricting the increase in the frequency of the plasma drive power supply is power loss. Although a higher frequency results in a stronger discharge of the plasma electrode, more power will be wasted at the same time.

[0035] Taking the air jet arc discharge as an example, the arc discharge has the load working characteristics of high voltage, low current, and low power in the arc starting stage, and low voltage, high current, and low power in the holding arc stage. When the frequency is too high, the arc discharge starts easily, has a short duration, and low power, while the holding arc stage will maintain a high voltage - high current - high power power loss mode for a long time, and the lost power is released in the form of heat, resulting in too high a temperature of the discharge electrode, which 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 the air jet arc discharge.

[0036] Aiming at the load characteristics of the air jet arc discharge, the segmented frequency conversion control method proposed by the present invention can well fit the discharge characteristics of the arc starting stage and the holding arc stage of the arc discharge. Such as Figure 2 shown, in the arc starting stage, a high-frequency f s_ignition pulse power is given to make the air jet start arc quickly. In the holding arc stage, a low-frequency f s_retainer pulse power is given to make the air jet maintain low-power operation within a long holding arc time t retainer , so as to greatly reduce the discharge power loss while ensuring the discharge intensity of the air jet, improve the discharge efficiency, and at the same time reduce the discharge heat generation, ensuring that the air jet device can operate stably for a long time.

[0037] Such as Figure 1As shown in the figure, the high-frequency AC pulse power supply includes a control circuit, a drive circuit, and a main circuit. The main circuit includes a rectifier circuit, an IGBT full-bridge inverter circuit, and an LC filter circuit. A filter is provided at the front end of the power supply. The filter is connected to the auxiliary power supply and the rectifier circuit respectively. The auxiliary power supply is connected to the control circuit. The control circuit is connected to the drive circuit. The drive circuit is connected to the IGBT full-bridge inverter circuit. The IGBT full-bridge inverter circuit is connected to the LC filter circuit. The LC filter circuit is connected to the high-voltage transformer.

[0038] Filter: Placed at the front end of the power supply, it is used to eliminate various interferences from the power grid, such as spike pulse interferences generated by motor starting, closing and opening of electrical switches, lightning strikes, etc. At the same time, it also prevents the high-frequency noise generated by the switching power supply from spreading to the power grid and polluting the power grid.

[0039] Auxiliary power supply: Outputs stable direct current, which is used to supply power to various chips in the entire power supply circuit, that is, to provide direct current that meets certain requirements for the control circuit and the protection circuit to ensure their stable and reliable operation.

[0040] Control circuit: Outputs different control signals to obtain the target pulse. By changing the program, the PWM control signal output by the digital controller can be adjusted to control the single-cycle t pulse The number of starting arc pulses in the period is N ignition And the number of holding arc pulses N retainer , and then control the ratio K = N ignition / N retainer , control the output voltage pulse, which is the core of the entire power supply. The control of the air jet arc discharge can be completed only by regulating the pulse power form output by the power supply, without adding any additional power or control hardware circuit. The volume of this power supply can be minimized, the system power density is high, and it can meet the different air jet discharge requirements in different application scenarios, which is beneficial to the integration, miniaturization, and portability of the plasma source whole machine equipment.

[0041] Drive circuit: Converts the control signal given by the control circuit into a drive signal that can drive the IGBT in the inverter circuit, and at the same time isolates the control signal from the output pulse to avoid interference to the control signal.

[0042] Rectifier circuit: Rectifies the industrial frequency alternating current filtered by the pre-filter to provide high-quality DC voltage for the inverter circuit, which is the basis for ensuring the normal output of high-frequency AC pulses.

[0043] IGBT full-bridge inverter circuit: It is the key part of this power supply system. It inversely converts the direct current rectified by the rectifier circuit into the target output high-frequency alternating current according to different control signals.

[0044] LC filter circuit and transformer: In the LC filter circuit, the capacitor and the primary inductor of the transformer cooperate to filter the output pulses of the inverter circuit. After filtering, the pulses are boosted by the transformer to a segmented variable-frequency high-voltage alternating current that can drive arc discharge.

[0045] It also includes a protection circuit. The protection circuit collects the high-voltage side current as feedback. When overcurrent or open circuit occurs in the power supply, it cuts off the power supply of the control circuit to force the power supply to stop working, which can protect the load and the power supply.

[0046] An air jet arc discharge device is used for the experiment of the segmented variable-frequency high-voltage AC pulse power supply, such as Figure 4 shown. The air jet arc discharge device includes a needle-shaped high-voltage electrode (1) and a ground electrode (2). The ground electrode (2) also serves as the outer shell, and the central support (3) fixes the high-voltage electrode (1) at the central position all the time.

[0047] The experiment conducts on-load discharge experiments for the output of high-frequency, low-frequency, and segmented variable-frequency control signals respectively, and compares the output of high-voltage AC pulses corresponding to the three control signals from the discharge voltage and current waveforms and the discharge light-emitting images. As Figures 5 - 13 shown, Figure 5 is the no-load voltage waveform of the high pulse frequency - fixed frequency control signal output. Figure 6 is the on-load voltage and current waveform of the high pulse frequency - fixed frequency control signal output. Figure 7 is the discharge image under the discharge waveform condition of the high pulse frequency - fixed frequency control signal output. Figure 8 is the no-load voltage waveform of the low pulse frequency - fixed frequency control signal output. Figure 9 is the on-load voltage and current waveform of the low pulse frequency - fixed frequency control signal output. Figure 10 is the discharge image under the discharge waveform condition of the low pulse frequency - fixed frequency control signal output. Figure 11 is the no-load voltage waveform of the segmented variable-frequency control signal output. Figure 12 is the on-load voltage and current waveform of the segmented variable-frequency control signal output. Figure 13 is the discharge image under the discharge waveform condition of the segmented variable-frequency control signal output.

[0048] It can be seen from the discharge voltage and current waveforms of the three control signal outputs that during the high-frequency signal, discharge occurs once per cycle, and the maximum discharge current is 1.6A, but the power density is high. It can be seen from the discharge light-emitting image that the discharge is the strongest. During the low-frequency signal, discharge occurs only once every few cycles, and the maximum discharge current is 4.4A, slightly higher than the discharge current during the high-frequency signal, but the power density is small. It can be seen from the discharge light-emitting image that the discharge is the weakest and almost no discharge can be seen. When the segmented variable-frequency control signal output drives the air jet with high-voltage pulses, the maximum discharge current reaches 8.6A, the power density is second only to that during the high-frequency signal, and it can be seen from the discharge image that the discharge intensity is slightly weaker than that during the high-frequency signal.

[0049] The temperature at the port of the jet device was measured experimentally after 1.5 min of high-voltage pulsed discharge with three different control signals output. The high-voltage AC pulse outputs corresponding to the three control signals were compared, as shown in Table 1. The experiment was carried out at room temperature of 25 °C.

[0050] Table 1 Temperature at the device port after 1.5 min of air jet discharge under different control signals

[0051]

[0052] From Table 1 and the above Figures 5 - 13 It can be seen that within the 1.5-min discharge time, the high-voltage pulsed discharge driven by the pure high-frequency output for air jet discharge is intense, and the temperature at the port of the jet device rises rapidly by 53 °C; the high-voltage pulsed discharge driven by the pure low-frequency output for air jet discharge is weak; while when the proportionality coefficient K = 1, the high-voltage pulsed discharge driven by the segmented variable-frequency output for air jet discharge can, while ensuring the discharge intensity, only increase the temperature by 14 °C, which is much lower than that of the pure high-frequency signal discharge. The change in temperature also proves from the side that the high-voltage pulse power supply with segmented variable-frequency control signal output proposed in this patent can save energy and improve the discharge efficiency while ensuring similar discharge intensity.

Claims

1. A segmented frequency conversion control method applied to an arc discharge high-frequency AC pulse power supply, characterized in that: Periodic envelope frequency f pulse remains unchanged, and the envelope frequency f pulse is divided into two forms of pulsed power drive. The arc ignition pulse f s_ignition at high frequency, and the arc holding pulse f s_retainer at low frequency. At the same time, the amplitude of the high-frequency AC pulse remains unchanged. During the arc ignition stage of the air jet, the high-frequency AC pulse power supply gives a high-frequency f s_ignition pulse power and maintains it for t ignition time. After successful arc ignition, it enters the arc holding stage. Control the high-frequency AC pulse power supply to output a low-frequency f s_retainer pulse power and maintain it for t retainer time until the discharge extinguishes and enters the next cycle. Among them, the f s_ignition frequency is more than ten times that of f s_retainer .

2. The segmented frequency conversion control method applied to the arc discharge high-frequency AC pulse power supply according to claim 1, wherein: The number of arc-starting ignition pulses in a single cycle is N ignition , and the number of arc-holding pulses in a single cycle is N retainer . Let the regulation ratio be K By adjusting the number of arc-starting ignition pulses in a single cycle to be N ignition , the number of arc-holding pulses N retainer , and then regulating the value of the ratio K, the discharge intensity of the air jet electrode is regulated 3. The segmented frequency conversion control method applied to the arc discharge high-frequency AC pulse power supply according to claim 1 or 2, characterized in that: The high-frequency AC pulse power supply includes a control circuit and a drive circuit. A filter is provided at the front end of the power supply. The filter is connected to an auxiliary source and a rectifier circuit respectively. The auxiliary source is connected to the control circuit. The control circuit is connected to the drive circuit. The drive circuit is connected to an IGBT full-bridge inverter circuit. The IGBT full-bridge inverter circuit is connected to an LC filter circuit. The LC filter circuit is connected to a high-voltage transformer. The auxiliary source outputs stable direct current to supply power to various chips in the entire power supply circuit. The control circuit outputs different control signals to obtain target pulses. The drive circuit converts the control signals given by the control circuit into drive signals that can drive the IGBTs in the inverter circuit. The rectifier circuit rectifies the industrial-frequency alternating current filtered by the pre-filter to provide high-quality DC voltage for the inverter circuit. The IGBT full-bridge inverter circuit inversely converts the direct current rectified by the rectifier circuit into high-frequency alternating current with the target output according to different control signals. In the LC filter circuit, the capacitor cooperates with the primary inductor of the transformer to filter the pulses output by the inverter circuit. After filtering, the pulses are boosted by the transformer into segmented variable-frequency high-voltage alternating current that can drive arc discharge.

4. The segmented frequency conversion control method applied to the arc discharge high-frequency AC pulse power supply according to claim 3, wherein: The high-frequency AC pulse power supply further includes a protection circuit. The protection circuit collects the high-voltage side current as feedback. When overcurrent or open circuit occurs in the power supply, it cuts off the power supply of the control circuit to force the power supply to stop working, protecting the load and the power supply.

5. The segmented frequency conversion control method applied to the arc discharge high-frequency AC pulse power supply according to claim 1 or 2 or 4, characterized in that: For the experiment of the segmented variable-frequency high-voltage AC pulse power supply, an air jet arc discharge device is used. The air jet arc discharge device includes a needle-shaped high-voltage electrode (1) and a ground electrode (2). The ground electrode (2) also serves as the outer shell. The central support (3) fixes the high-voltage electrode (1) at a central position all the time.

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