A high-power torch power supply applied to plasma

Abstract

The application discloses a kind of high-power torch power supply applied to plasma, it is related to plasma technical field, based on existing high-power torch power supply is improved, additional controllable direct current power loop, through controllable direct current power loop and main power loop cooperation to adapt to different stages of plasma production, in plasma generation stage, loop no-load voltage stringing direct current power to avoid the redundancy of multiple power loop, improve the application range of high-power torch power supply;In plasma arc stabilization stage, direct current power loop inhibits the growth rate of current;Plasma discharge maintenance stage, direct current power loop conduction voltage drop is small, reduces heat loss;Plasma extinction stage, direct current power loop plays the role of power inductance, and by algorithm preset, can be equivalent to the effect of larger inductance;Through the effect of controllable direct current power loop in different stages, the load adaptability, volume weight, output dynamic characteristic etc. of high-power torch power supply are all improved.

Description

Technical Field

[0001] This invention relates to the field of plasma technology, and more specifically to a high-power torch power supply for use in plasma. Background Technology

[0002] With the rapid development of my country's industrialization, thermal plasma melting technology has significant advantages in the treatment of hazardous waste, medical infectious waste, and chemical and heavy metal contaminated waste. For example, in these areas, thermal plasma melting technology has outstanding advantages such as high processing temperature, suitability for a wide range of types, and minimal secondary pollution, and is therefore widely used.

[0003] With the widespread application of thermal plasma melting technology, the output power of plasma torch power supplies is increasing. For ultra-large-scale power systems, it is often necessary to achieve output currents of nearly 1,000 amps and output power of nearly 1 megawatt. As a crucial component of thermal plasma melting technology, the stable and reliable performance of high-power torch power supplies is a vital guarantee for the application of thermal plasma melting. The working process of thermal plasma melting is divided into four stages.

[0004] The first stage is the plasma generation stage. A high-voltage trigger excitation generates an electric field that accelerates gas particles, ionizing them to produce plasma. The trigger excitation voltage is related to the distance between the anode and cathode, the gas composition, and the gas flow rate. The longer the distance between the cathode and anode, the higher the required trigger excitation voltage; the more difficult the gas composition to ionize, the higher the required trigger excitation voltage and the higher the power circuit open-circuit voltage. For example, the trigger excitation voltage for atmospheric nitrogen is five times that for vacuum-ionized argon. A higher power circuit open-circuit voltage makes trigger excitation and arc stabilization easier. To reduce the difficulty of plasma generation, multiple electrodes are often added, along with an arc-switching circuit. To meet the changing application scenarios, the plasma torch power supply needs a certain power redundancy. For ultra-large-scale power systems, avoiding this power redundancy is crucial.

[0005] The triggering voltage in this stage is relatively high, exceeding several kilovolts, but its power is very low, below one hundred watts. Through this high-voltage triggering excitation, a plasma channel is formed between the anode and cathode, the power circuit changes from no-load to loaded, and the output current increases rapidly. Due to the above factors, the level of the no-load voltage in the power circuit during this stage directly affects whether the plasma channel breaks down rapidly and whether the output current can increase rapidly.

[0006] The second stage is the arc stabilization stage. The output current of the power circuit rapidly increases to nearly 100 amps and remains stable, allowing the plasma to form a stable arc circuit. This stage is often accompanied by high-voltage triggering excitation and drastic changes in load impedance. The power supply system needs to have a rapid dynamic response capability to adjust and stabilize the output current while avoiding electrode ablation caused by overcurrent. In this stage, the higher open-circuit voltage of the power circuit is beneficial for arc stabilization, and the better current limiting effect of the output circuit helps suppress ablation.

[0007] The third stage is the maintenance stage. In the later stages of the process, the output voltage and current of the plasma torch power supply gradually increase, and the conduction loss of the power devices is proportional to the square of the current. Reducing conduction loss is therefore of great significance.

[0008] The fourth stage is the annihilation stage. This stage is not a necessary part of the plasma torch's operation. During the process, changes in the type and composition of hazardous waste, as well as the flow rate of gases, can cause significant changes in plasma impedance. If the power supply cannot respond quickly, it will be unable to maintain a normal discharge state, leading to plasma annihilation and forcing the process to stop. To avoid this, high-power plasma torch power supplies use power inductors with large inductance in series at the output. However, for ultra-large-scale power systems, high-current, high-inductance power inductors are costly, bulky, and have high heat loss. Therefore, avoiding large-capacity power inductors is of great importance.

[0009] Traditional high-power plasma torch power supplies often consist of multiple power loops connected in parallel to output large currents and high power, which cannot adapt to the various stages of plasma torch operation. This results in power redundancy, higher costs, increased size and weight of high-power plasma torch power supplies, and extremely high requirements for the loop stability of the power supply. Summary of the Invention

[0010] The technical problem this invention aims to solve is that traditional high-power plasma torch power supplies often consist of multiple power circuits connected in parallel to output large currents and high power, which cannot adequately adapt to the various stages of a plasma torch operation. The purpose of this invention is to provide a high-power torch power supply for plasma applications. Based on existing high-power torch power supplies, this invention improves upon them by adding a controllable DC power circuit. Through the coordination of this controllable DC power circuit with the main power circuit, problems arising at each stage of torch operation are optimized.

[0011] This invention is achieved through the following technical solution:

[0012] This solution provides a high-power torch power supply for plasma applications. The high-power torch power supply includes a controllable DC power circuit and multiple power circuits. The multiple power circuits are connected in parallel to form a main power circuit, and the controllable DC power circuit is connected in series with the main power circuit.

[0013] During the plasma generation stage, a controllable DC power circuit is connected in series with a power circuit to increase the open-circuit voltage, which is used to adapt to different torch devices and torch processes to generate plasma discharge.

[0014] During the plasma arc stabilization phase, connecting the controllable DC power circuit in series with the power circuit to increase the open-circuit voltage is beneficial for quickly stabilizing the arc, while suppressing the growth rate of the main power circuit current.

[0015] During the plasma sustaining phase, the controllable DC power circuit short-circuits the turn-on voltage drop of the power devices via a pass-through switch. The contact resistance of the pass-through switch is within 0.5 milliohms, and heat loss is reduced by connecting multiple pass-through switches in parallel.

[0016] During the plasma annihilation stage, the controllable DC power circuit is connected in series with the power circuit to act as a power inductor, and through algorithm preset, it can be equivalent to a large inductance.

[0017] The working principle of this solution: Traditional high-power plasma torch power supplies often consist of multiple power circuits connected in parallel to output large currents and high power, which cannot adapt to the various stages of plasma torch operation. The purpose of this invention is to provide a high-power torch power supply for plasma applications. Based on existing high-power torch power supplies, it improves upon them by adding a controllable DC power circuit. This controllable DC power circuit works in conjunction with the main power circuit to adapt to different stages of plasma torch operation; it is particularly suitable for the treatment of hazardous materials at ultra-high power scales, such as radioactive nuclear waste and waste residue containing heavy metals and other harmful substances.

[0018] A further optimized scheme is that the controllable DC power circuit includes: a DC circuit soft-switching inverter circuit, a DC circuit power transformer, a DC circuit high-frequency rectifier and filter circuit, a DC circuit chopper power switching device, a DC circuit freewheeling power switching device, a DC circuit current-limiting resistor, a DC circuit through-power switching device group, and a DC circuit control circuit;

[0019] The DC power required by the DC soft-switching inverter circuit can be provided by the AC-DC rectifier circuit of a main power circuit, or by AC-DC rectification of the three-phase power from the grid. The DC power is output sequentially through the DC soft-switching inverter circuit, the DC power transformer, and the DC high-frequency rectifier and filter circuit. The positive output terminal of the DC high-frequency rectifier and filter circuit is connected in series with a DC chopper power switch to serve as the positive output terminal of the high-power torch. The negative output terminal of the DC high-frequency rectifier and filter circuit is connected to the positive output terminal of the main power circuit. A DC freewheeling power switch and a DC current-limiting resistor are connected in series, with one end connected to the positive output terminal of the high-power torch and the other end connected to the negative output terminal of the DC high-frequency rectifier and filter circuit. A DC direct-through power switch group is connected with one end to the positive output terminal of the high-power torch and the other end to the negative output terminal of the DC high-frequency rectifier and filter circuit.

[0020] The DC circuit control circuit is connected to the DC circuit soft-switching inverter circuit, the DC circuit high-frequency rectifier and filter circuit, the DC circuit chopper power switch, the DC circuit freewheeling power switch, and the DC circuit through-power switch group, respectively.

[0021] The DC-DC soft-switching inverter circuit inverts the received DC power into a high-frequency bipolar output, providing a high-frequency AC input for the power transformer. The DC-DC soft-switching inverter circuit preferably uses the same structure as the soft-switching inverter circuit, implemented by a multi-level phase-shifting full-bridge inverter circuit, an interleaved series two-level full-bridge phase-shifting inverter circuit, or a three-level full-bridge LLC inverter circuit, reducing switching losses, improving efficiency, and reducing electromagnetic interference.

[0022] The DC circuit power transformer realizes power isolation and level conversion, and provides high-frequency AC input for the high-frequency rectifier and filter circuit;

[0023] The DC circuit high-frequency rectifier and filter circuit rectifies the high-frequency AC input into DC power with an isolation potential. It is preferably implemented using a synchronous rectifier circuit, a full-bridge rectifier circuit, a full-wave rectifier circuit, a half-bridge rectifier circuit, a half-wave rectifier circuit, an LC filter circuit, and a capacitor filter circuit.

[0024] The DC circuit freewheeling power switch provides a freewheeling path for the DC circuit chopper power switch during the turn-off moment. By selecting an appropriate on-resistance, the DC circuit freewheeling power switch can reduce the voltage of the anti-parallel diode when it is turned on.

[0025] The DC loop control circuit controls the power switch of the soft-switching inverter circuit, enabling the power switch to turn on with zero voltage and turn off with zero current, resulting in low switching losses. The DC loop control circuit also needs to sample electrical signals such as output voltage, output current, and inverter current in real time and send them to microprocessors such as ARM, DSP, and FPGA to implement various algorithm functions.

[0026] A further optimized solution is that the power circuit includes: a three-phase EMI filter circuit, a controllable rectifier circuit, a soft-switching inverter circuit, a power transformer, a high-frequency rectifier and filter circuit, and a control circuit;

[0027] After the three-phase AC power is denoised by the three-phase EMI filter circuit, it is input to the controllable rectifier circuit for rectification to obtain DC power. The DC power is then output after passing through the soft-switching inverter circuit, the power transformer and the high-frequency rectifier filter circuit in sequence. The negative output terminal of the high-frequency rectifier filter circuit serves as the negative output terminal of the high-power torch, and the positive output terminal of the high-frequency rectifier filter circuit is connected to the negative output terminal of the high-frequency rectifier filter circuit in the DC circuit.

[0028] The control circuit is connected to the controllable rectifier circuit, the soft-switching inverter circuit, and the high-frequency rectifier and filter circuit, respectively.

[0029] The three-phase EMI filter circuit performs noise reduction and anti-interference on the three-phase AC power on the grid side, and provides AC input for the controllable rectifier circuit; the controllable rectifier circuit converts the three-phase AC power into DC power, and inputs the DC power into the soft-switching inverter circuit and the DC circuit soft-switching inverter circuit of the controllable DC power circuit respectively;

[0030] A further optimized solution is that the three-phase EMI filter circuit consists of an X capacitor, a Y capacitor, a differential-mode filter inductor, a common-mode filter inductor, a varistor, and a thermistor.

[0031] The controllable rectifier circuit is preferably a three-phase three-wire three-level VIENNA rectifier circuit or a three-phase six-switch PFC circuit to reduce the harmonic content on the grid side and improve the power factor.

[0032] The soft-switching inverter circuit converts the received DC power into a high-frequency bipolar output, providing a high-frequency AC input for the power transformer. The soft-switching inverter circuit is preferably implemented using a multi-level phase-shifting full-bridge inverter circuit, an interleaved series two-level full-bridge phase-shifting inverter circuit, or a three-level full-bridge LLC inverter circuit, which reduces switching losses, improves efficiency, and reduces electromagnetic interference.

[0033] The power transformer achieves power isolation and level conversion, providing a high-frequency AC input with isolation potential for the high-frequency rectifier and filter circuit;

[0034] The high-frequency rectifier and filter circuit rectifies the high-frequency AC input into DC power. The high-frequency rectifier and filter circuit is preferably implemented using a synchronous rectifier circuit, a full-bridge rectifier circuit, a full-wave rectifier circuit, a half-bridge rectifier circuit, a half-wave rectifier circuit, an LC filter circuit, and a capacitor filter circuit.

[0035] The control circuit controls the power switch of the soft-switching inverter circuit, enabling the power switch to turn on with zero voltage and turn off with zero current, resulting in low switching losses. The control circuit also controls the power switch of the synchronous rectifier circuit, enabling the power switch to turn on with zero voltage and turn off with zero current, again resulting in low switching losses. The control circuit also needs to sample output voltage, output current, inverter current, and other electrical signals in real time, and implement various control functions through microprocessor algorithms such as ARM, DSP, and FPGA.

[0036] A further optimization scheme is proposed, where the number n of power loops in the main power loop is determined based on the maximum output power P of the high-power torch power supply:

[0037] n = P / a

[0038] In the formula, a represents the power provided by a power loop, and a ranges from 20 to 80 kW; n is an integer.

[0039] A further optimized scheme is that the DC loop control circuit is also used to determine the stage of the plasma, and control the switching on and off of the DC loop soft-switching inverter circuit, the DC loop high-frequency rectifier filter circuit, the DC loop chopper power switch device, the DC loop freewheeling power switch device, and the DC loop through-power switch device group according to the stage of the plasma.

[0040] A further optimized scheme involves turning on the DC circuit chopper power switch during the plasma generation stage, while turning off the DC circuit freewheeling power switch and the DC circuit direct-through power switch group. The turn-on of the DC circuit chopper power switch ensures that the open-circuit voltage of the high-power torch power supply is a series combination of the DC circuit output voltage and the main power circuit output voltage. This increases the open-circuit voltage between the torch cathode and anode, and, in conjunction with the arc-switching circuit, facilitates the generation of stable plasma discharge.

[0041] A further optimized scheme involves turning off the DC circuit chopper power switch and the DC circuit direct-acting power switch group during the plasma arc stabilization phase, while turning on the DC circuit freewheeling power switch. The resistor acts as a current limiter, suppressing the current growth rate and allowing for a rapid and gradual establishment of the plasma load, thus preventing cathode ablation.

[0042] A further optimized scheme involves turning off the DC circuit chopper power switch and the DC circuit freewheeling power switch during the continuous plasma discharge phase, while turning on the DC circuit direct-through power switch group. This avoids power heat loss caused by a large current flowing through the DC circuit freewheeling power switch and the DC circuit current-limiting resistor when the DC circuit chopper power switch is not conducting.

[0043] A further optimization scheme involves turning on the DC circuit chopper power switching device before the process changes when changes in discharge conditions may cause the plasma to be in the annihilation stage. The output voltage of the DC circuit soft-switching inverter circuit is adjusted by high-speed current acquisition, which changes the voltage between the torch cathode and anode. The algorithm maintains a constant output current, thus replacing the power inductor.

[0044] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0045] This invention provides a high-power torch power supply for plasma applications. Based on existing high-power torch power supplies, it improves upon existing ones by adding a controllable DC power circuit. This controllable DC power circuit works in conjunction with the main power circuit to adapt to different stages of plasma production. During the plasma generation stage, the main power circuit is connected in series with the DC power circuit to increase the open-circuit voltage, avoiding redundancy from multiple power circuits and expanding the application range of the high-power torch power supply. During the plasma arc stabilization stage, the higher open-circuit voltage facilitates rapid arc establishment, while the DC power circuit suppresses the current growth rate. During the plasma discharge stabilization stage, the DC power circuit achieves low-loss conduction. During the plasma annihilation stage, large components such as external power inductors are avoided in the power circuit; instead, an algorithm maintains a constant output current, effectively replacing the role of a power inductor. Through these different functions at different stages, the high-power torch power supply's load adaptability, size and weight, and output dynamic characteristics are improved. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0047] Figure 1 A schematic diagram of the principle of a high-power torch power supply applied to plasma;

[0048] Figure 2 Schematic diagram of the working principle of a high-power torch power supply in the plasma generation stage;

[0049] Figure 3 Schematic diagram of the working principle of a high-power torch power supply during the plasma arc stabilization stage;

[0050] Figure 4 This is a schematic diagram of the working principle of a high-power torch power supply during the plasma sustaining phase.

[0051] The attached diagram shows the markings and corresponding component names:

[0052] 1-Three-phase EMI filter circuit, 2-Controllable rectifier circuit, 3-Soft-switching inverter circuit, 4-Power transformer, 5-High-frequency rectifier and filter circuit, 6-Control circuit, 7-Power circuit, 8-DC circuit soft-switching inverter circuit, 9-DC circuit power transformer, 10-DC circuit high-frequency rectifier and filter circuit, 11-DC circuit chopper power switch device, 12-DC circuit freewheeling power switch device, 13-DC circuit current-limiting resistor, 14-DC circuit through-through power switch device group, 15-DC circuit control circuit, 16-Controllable DC power circuit. Detailed Implementation

[0053] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0054] Example 1

[0055] This embodiment provides a high-power torch power supply for plasma applications, such as... Figure 1 As shown, the high-power torch power supply includes a controllable DC power circuit 16 and multiple power circuits 7; the multiple power circuits 7 are connected in parallel to form a main power circuit, and the controllable DC power circuit 16 is connected in series with the main power circuit;

[0056] During the plasma generation stage, the open-circuit voltage superimposed in series between the controllable DC power circuit 16 and the main power circuit is used to adapt to different torch devices and torch processes to generate plasma discharge.

[0057] During the plasma arc stabilization stage, the controllable DC power circuit 16 is connected in series with multiple power circuits 7 to increase the open-circuit voltage, which is beneficial for quickly stabilizing the arc and suppressing the current growth rate.

[0058] During the plasma sustaining phase, the controllable DC power circuit 16 nearly short-circuits the on-state voltage drop by directly connecting the DC circuit to the power switching device group 14, thereby reducing heat loss.

[0059] During the plasma annihilation stage, the controllable DC power circuit 16 is connected in series with multiple power circuits 7 to act as a power inductor, and through algorithm preset, it can be equivalent to a large inductance.

[0060] The controllable DC power circuit 16 includes: a DC circuit soft-switching inverter circuit 8, a DC circuit power transformer 9, a DC circuit high-frequency rectifier and filter circuit 10, a DC circuit chopper power switch device 11, a DC circuit freewheeling power switch device 12, a DC circuit current-limiting resistor 13, a DC circuit through-power switch device group 14, and a DC circuit control circuit 15.

[0061] The DC power required by the DC soft-switching inverter circuit 8 can be provided by a controllable rectifier circuit 2 in a power loop, or by AC-DC rectification of the three-phase power from the mains. In this embodiment, the DC power required by the DC soft-switching inverter circuit 8 is provided by the controllable rectifier circuit 2.

[0062] The DC power required by the DC circuit soft-switching inverter circuit 8 is output after passing through the soft-switching inverter circuit 8, the DC circuit power transformer 9, and the DC circuit high-frequency rectifier and filter circuit 10. The positive output terminal of the DC circuit high-frequency rectifier and filter circuit 10 is connected in series with the DC circuit chopper power switch device 11 and serves as the positive output terminal of the high-power torch power supply. The negative output terminal of the DC circuit high-frequency rectifier and filter circuit 10 is connected to the positive output terminal of multiple power circuits 7. The DC circuit freewheeling power switch device 13 and the DC circuit current-limiting resistor 13 are connected in series, with one end connected to the positive output terminal of the high-power torch power supply and the other end connected to the negative output terminal of the DC circuit high-frequency rectifier and filter circuit 10. One end of the DC circuit direct-through power switch device group 14 is connected to the positive output terminal of the high-power torch power supply and the other end is connected to the negative output terminal of the DC circuit high-frequency rectifier and filter circuit 10.

[0063] The DC circuit control circuit 15 is connected to the DC circuit soft-switching inverter circuit 8, the DC circuit high-frequency rectifier and filter circuit 10, the DC circuit chopper power switch device 11, the DC circuit freewheeling power switch device 12, and the DC circuit through-through power switch device group 14, respectively.

[0064] The DC circuit soft-switching inverter circuit 8 inverts the received DC power into a high-frequency bipolar output and provides a high-frequency AC input to the DC circuit power transformer 9; the DC circuit power transformer 9 realizes power isolation and level conversion; the DC circuit power transformer 9 can use the same materials as the power transformer 4; the DC circuit high-frequency rectifier and filter circuit 10 rectifies the high-frequency AC input into DC power with isolation potential, and the circuit used in the DC circuit high-frequency rectifier and filter circuit 10 is the same as that in the high-frequency rectifier and filter circuit 5;

[0065] The DC circuit chopper power switch device 11 controls whether the potential difference of the DC circuit is superimposed on the positive potential of the power circuit 7. When the drive circuit of the DC circuit chopper power switch device 11 is low, the DC circuit chopper power switch device 11 is not turned on, and at this time the potential difference of the DC power circuit 16 is not superimposed on the positive potential of the power circuit 7. When the drive circuit of the DC circuit chopper power switch device 11 is high, the DC circuit chopper power switch device 11 is turned on, and at this time the potential difference of the DC power circuit 16 is superimposed on the positive potential of the power circuit 7.

[0066] During the high-voltage triggering excitation stage to generate plasma, the DC circuit chopper power switching device 11 is turned on. By changing the pulse width or pulse frequency of the DC circuit soft-switching inverter circuit 8, a large potential difference is ensured in the DC power circuit 16. At this time, the voltage between the cathode and anode is increased, and with the help of the arc-switching circuit, a stable plasma discharge can be easily generated.

[0067] During the plasma arc stabilization stage and the plasma continuous discharge stage (i.e., when the plasma is in a relatively stable discharge condition), the DC circuit chopper power switching device 11 is not turned on.

[0068] During the plasma discharge condition change phase, the DC power circuit 16 maintains a small potential difference by varying the pulse width or pulse frequency of the DC soft-switching inverter circuit 8. The magnitude of the potential difference can be preset by the controller algorithm or set by the user. The increased potential difference increases the output voltage and maintains a constant output current.

[0069] The DC circuit chopper power switching device 11 uses devices such as MOSFET, IGBT, and SiC. The selection principle is related to the maximum output current and maximum output voltage of the DC power circuit 16.

[0070] The DC-loop freewheeling power switch 12, together with the DC-loop chopper power switch 11 and the DC-loop current-limiting resistor 13, forms a power topology similar to a Buck circuit. When the drive circuit of the DC-loop freewheeling power switch 12 is low, the DC-loop freewheeling power switch 12 is not turned on. When the drive circuit of the freewheeling power switch 12 is high, the DC-loop freewheeling power switch 12 is turned on. The DC-loop freewheeling power switch 12 can provide a freewheeling path at the moment when the DC-loop chopper power switch 11 is turned off.

[0071] During the high-voltage triggering excitation stage to generate plasma, the DC circuit freewheeling power switching device 12 is not turned on.

[0072] During the plasma arc stabilization phase, the DC circuit freewheeling power switch 12 is turned on. The DC circuit freewheeling power switch 12 is connected in series with the DC circuit current limiting resistor 13, which can limit the rapid change of plasma impedance.

[0073] When the plasma is in a relatively stable discharge condition stage, or when the plasma is in a stage where the discharge condition changes, the DC circuit freewheeling power switch device 12 is not turned on.

[0074] The DC circuit freewheeling power switching device 12 can be made of MOSFET, IGBT, SiC, etc. The selection principle is related to the maximum output current and maximum output voltage of the DC power circuit 16.

[0075] The aforementioned DC circuit freewheeling power switching device 12 contains an anti-parallel diode. However, by selecting an appropriate on-resistor, the voltage drop across the diode can be reduced by controlling the on-state of the device, thereby reducing power consumption.

[0076] During the plasma arc stabilization phase, the DC circuit current-limiting resistor 13 is connected in series with the DC circuit freewheeling power switch 12 to suppress the current growth rate and play a role in quickly and smoothly establishing the plasma load.

[0077] Whether the output positive potential of the DC-DC direct-through power switching device group 14 is the same as the output positive potential of the power circuit 7, and whether the operating states of the DC-DC direct-through power switching device group 14 and the DC-DC chopper power switching device 11 are mutually exclusive.

[0078] The DC-loop direct-through power switching device group 14 uses back-to-back MOSFETs, SiCs, DC contactors, and other devices to form a bidirectional switch. The DC-loop direct-through power switching device group 14 conducts during the plasma arc stabilization stage, when the plasma discharge conditions are relatively stable. This avoids power heat loss caused by a large current flowing through the DC-loop freewheeling power switching device and the DC-loop current-limiting resistor when the DC-loop chopper power switching device is not conducting. Using back-to-back MOSFETs and SiCs to form the bidirectional switch offers advantages such as fast switching speed and rich control algorithms. Using DC contactors to form the bidirectional switch offers advantages such as low on-resistance, low cost, and suitability for high currents.

[0079] The main functions of the DC loop control circuit 15 include: sampling analog quantities such as output voltage, output current, and inverter current; acquiring and protecting the current of power devices; implementing PWM or PFM drive signals; and communicating with the control circuit 6. The DC loop control circuit 15 outputs power device drives for the DC loop soft-switching inverter circuit 8, the DC loop high-frequency rectifier and filter circuit 10, the DC loop chopper power switch device 11, the DC loop freewheeling power switch device 12, and the DC loop through-through power switch device group 14.

[0080] The power circuit 7 includes: a three-phase EMI filter circuit 1, a controllable rectifier circuit 2, a soft-switching inverter circuit 3, a power transformer 4, a high-frequency rectifier filter circuit 5, and a control circuit 6.

[0081] After the three-phase AC power is denoised by the three-phase EMI filter circuit 1, it is bipolarly input to the controllable rectifier circuit 2 for rectification to obtain bipolar DC power. The bipolar DC power is then output after passing through the soft-switching inverter circuit 3, the power transformer 4, and the high-frequency rectifier filter circuit 5. The negative output terminal of the high-frequency rectifier filter circuit 5 serves as the negative output terminal of the high-power torch power supply, and the positive output terminal of the high-frequency rectifier filter circuit 5 is connected to the negative output terminal of the DC circuit high-frequency rectifier filter circuit 10.

[0082] The control circuit 6 is connected to the controllable rectifier circuit 2, the soft-switching inverter circuit 3, and the high-frequency rectifier and filter circuit 5, respectively.

[0083] In this embodiment, the three-phase EMI filter circuit 1 is used to suppress noise and interference in the three-phase AC power supply on the grid side, providing AC input for the controllable rectifier circuit. The three-phase EMI filter circuit 1 consists of an X capacitor, a Y capacitor, a differential-mode filter inductor, a common-mode filter inductor, a varistor, and a thermistor, which significantly suppresses electromagnetic common-mode noise and differential-mode noise.

[0084] The controllable rectifier circuit 2 consists of a rectifier topology composed of multiple diodes and multiple power switches, used to convert three-phase AC power into DC power and input the DC power to the soft-switching inverter circuit. The controllable rectifier circuit 2 can reduce the harmonic content on the grid side and improve the power factor; in this embodiment, the controllable rectifier circuit 2 can be implemented by a three-level VIENNA rectifier circuit or a three-phase six-switch PFC circuit.

[0085] The soft-switching inverter circuit 3 inverts the received DC power into a high-frequency bipolar output to the power transformer 4. The soft-switching inverter circuit 3 is implemented using a multi-level phase-shifting full-bridge inverter circuit, an interleaved series two-level full-bridge phase-shifting inverter circuit, or a three-level full-bridge LLC inverter circuit, which can reduce switching losses, improve efficiency, and reduce electromagnetic interference.

[0086] The power transformer 4 achieves power isolation and level conversion; the magnetic core of the power transformer 4 is made of ferrite, amorphous, nanocrystalline and other materials, and the coil of the power transformer 4 is made of high frequency wire, copper foil and other materials.

[0087] The high-frequency rectifier and filter circuit 5 rectifies the high-frequency AC input into DC with an isolation potential. The high-frequency rectifier and filter circuit 5 is implemented using a synchronous rectifier circuit, a full-bridge rectifier circuit, a full-wave rectifier circuit, a half-bridge rectifier circuit, a half-wave rectifier circuit, an LC filter circuit, and a capacitor filter circuit.

[0088] The main functions of control circuit 6 include: sampling analog quantities such as output voltage, output current, and inverter current; acquiring and protecting the current of power devices; implementing PWM or PFM drive signals; communication with the host computer; and interface display. Control circuit 6 drives the power devices of soft-switching inverter circuit 3 and high-frequency rectifier and filter circuit 5.

[0089] The number of power circuits n in the main power circuit is determined based on the maximum output power P of the high-power torch power supply:

[0090] n = P / a

[0091] In the formula, a represents the power provided by a power loop, and a ranges from 20 to 80 kW.

[0092] Example 2

[0093] Based on Example 1, during the plasma generation stage, the DC circuit chopper power switch is turned on, while the DC circuit freewheeling power switch and the DC circuit direct-through power switch are turned off. The operating circuit of the high-power torch power supply is as follows: Figure 2 As shown:

[0094] During the high-voltage triggering and excitation plasma generation stage, the negative output potential of DC power circuit 16 is superimposed on the positive output potential of power circuit 7. The high-power plasma torch power supply, combined with the high-voltage triggering and excitation, and the relatively high open-circuit voltage, along with the arc-switching circuit, easily generates stable plasma discharge. When the DC circuit control circuit 15 detects that the voltage of the high-power plasma torch device drops to the arc voltage and the current rises and remains there for hundreds of milliseconds, the high-voltage triggering and excitation plasma generation stage ends.

[0095] Example 3

[0096] Based on Example 1, during the plasma arc stabilization stage, in this example, the DC circuit chopper power switch and the DC circuit direct-through power switch are turned off, while the DC circuit freewheeling power switch is turned on. The operating circuit of the high-power torch power supply is as follows: Figure 3 As shown:

[0097] During the plasma arc stabilization phase, the impedance changes rapidly, with the parallel loads of multiple power circuits abruptly changing from infinity to plasma impedance, for example, approximately 0.4 ohms in an argon atmosphere. If the current is instantaneously large, short-circuit protection and device shutdown will occur, preventing stable operation. If the current is not limited, the extremely large current will cause cathode erosion. At this time, the DC power circuit 16 controls the DC circuit chopper power switch 11 to be off, the DC circuit freewheeling power switch 12 to be on, and the DC circuit direct-through power switch group 14 to be off, thereby suppressing the current increase and achieving soft start on the rising edge. When the DC circuit control circuit 15 detects that the high-power plasma torch device has risen to a preset value and remains stable for several hundred milliseconds, it determines that the plasma arc is stable, and the plasma arc stabilization phase ends.

[0098] Example 4

[0099] Based on Example 1, during the plasma sustaining phase, the DC-loop chopper power switch and the DC-loop freewheeling power switch are turned off, while the DC-loop direct-through power switch group is turned on. The operating circuit of the high-power torch power supply is as follows: Figure 4 As shown:

[0100] When the plasma is in a relatively stable discharge condition stage, the DC loop direct-through power switching device group 14 uses back-to-back MOSFETs, IGBTs, SiC, DC contactors, and other devices to form a bidirectional switch. At this time, multiple power loops 7 are connected in parallel to power the plasma torch device. With the development and advancement of power devices, when the DC loop voltage drop is less than 300V, low on-resistance MOSFETs can be selected as back-to-back power devices; when the DC loop voltage drop is greater than 300V, low on-resistance SiC can be selected as back-to-back power devices. When using DC contactor devices to form a bidirectional switch, it has the advantages of low on-resistance, low cost, and is more suitable for high current, but the response speed is relatively slow, and it can only achieve good results in a defined process step. The DC loop control circuit 15 controls the DC loop chopper power switching device 11 to be off, controls the DC loop freewheeling power switching device 12 to be off, and controls the DC loop direct-through power switching device group 14 to be on. When the DC loop control circuit 15 detects that the high-power torch power supply process is about to end and the load voltage and current change drastically, the relatively stable discharge condition stage of the plasma ends.

[0101] Example 5

[0102] Based on Example 1, in this example, when the discharge conditions change and the plasma may be in the annihilation stage, the DC loop control circuit 15 determines whether to execute the following algorithm at the microsecond level:

[0103] The DC circuit control circuit 15 controls the DC circuit chopper power switch 11 to conduct, controls the DC circuit freewheeling power switch 12 to de-conduct, and controls the DC circuit direct-through power switch group 14 to de-conduct. At this time, the DC power circuit 16 increases the output voltage and maintains a constant output current, thus stabilizing the output of the high-power torch. The DC circuit control circuit 15, through microsecond-level electrical parameter acquisition and preset adjustable DC power circuit output voltage, can simulate the inductance effect of different inductance values. When the DC circuit control circuit 15 detects that the output of the high-power plasma torch is stable, the plasma re-enters a stage with relatively stable discharge conditions. The operating circuit of the high-power torch is as follows: Figure 2 As shown

[0104] The DC loop control circuit is also used to determine the stage of the plasma and control the switching on and off of the DC loop soft-switching inverter circuit, the DC loop high-frequency rectifier filter circuit, the DC loop chopper power switch, the DC loop freewheeling power switch, and the DC loop through-power switch group according to the stage of the plasma.

[0105] The control circuit is also used to determine the stage of the plasma and control the controllable rectifier circuit, soft-switching inverter circuit and high-frequency rectifier filter circuit according to the stage of the plasma.

[0106] The three-phase EMI filter circuit consists of an X capacitor, a Y capacitor, a differential-mode filter inductor, a common-mode filter inductor, a varistor, and a thermistor.

[0107] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-power torch power supply for plasma applications, characterized in that, The high-power torch power supply includes a controllable DC power circuit and multiple power circuits; the multiple power circuits are connected in parallel to form a main power circuit, and the controllable DC power circuit is connected in series with the main power circuit. During the plasma generation stage, the controllable DC power circuit and the power circuit together generate an open-circuit voltage to generate plasma discharge. During the plasma arc stabilization phase, the controllable DC power circuit is used to suppress the growth rate of the main power circuit current. During the plasma sustaining phase, the controllable DC power loop is activated; During the plasma annihilation phase, the DC power circuit is equivalent to a power inductor. The controllable DC power circuit includes: a DC circuit soft-switching inverter circuit, a DC circuit power transformer, a DC circuit high-frequency rectifier and filter circuit, a DC circuit chopper power switch device, a DC circuit freewheeling power switch device, a DC circuit current-limiting resistor, a DC circuit through-power switch device group, and a DC circuit control circuit. The main power circuit provides rectified bipolar DC power to the controllable DC power circuit. The bipolar DC power passes sequentially through the DC circuit soft-switching inverter circuit, the DC circuit power transformer, and the DC circuit high-frequency rectifier and filter circuit before being output. The positive output terminal of the DC circuit high-frequency rectifier and filter circuit is connected in series with the DC circuit chopper power switching device and serves as the positive output terminal of the high-power torch. The negative output terminal of the DC circuit high-frequency rectifier and filter circuit is connected to the main power circuit. The DC circuit freewheeling power switching device and the DC circuit current-limiting resistor are connected in series, with one end connected to the positive output terminal of the high-power torch and the other end connected to the negative output terminal of the DC circuit high-frequency rectifier and filter circuit. One end of the DC circuit through-power switching device group is connected to the positive output terminal of the high-power torch and the other end is connected to the negative output terminal of the DC circuit high-frequency rectifier and filter circuit. The DC loop control circuit is connected to the DC loop soft-switching inverter circuit, the DC loop high-frequency rectifier and filter circuit, the DC loop chopper power switching device, the DC loop freewheeling power switching device and the DC loop through-power switching device group, respectively. The power circuit includes: a three-phase EMI filter circuit, a controllable rectifier circuit, a soft-switching inverter circuit, a power transformer, a high-frequency rectifier and filter circuit, and a control circuit. After the three-phase AC power is denoised by the three-phase EMI filter circuit, it is bipolarly input to the controllable rectifier circuit for rectification to obtain bipolar DC power. The bipolar DC power is then output after passing through the soft-switching inverter circuit, the power transformer and the high-frequency rectifier filter circuit in sequence. The negative output terminal of the high-frequency rectifier filter circuit is used as the negative output terminal of the high-power torch, and the positive output terminal of the high-frequency rectifier filter circuit is connected to the negative output terminal of the high-frequency rectifier filter circuit of the DC circuit. The control circuit is connected to the controllable rectifier circuit, the soft-switching inverter circuit, and the high-frequency rectifier and filter circuit respectively. During the plasma generation stage, the DC circuit chopper power switch is turned on, and the DC circuit freewheeling power switch and the DC circuit direct-through power switch are turned off. During the plasma arc stabilization phase, the DC circuit chopper power switch and the DC circuit direct-through power switch group are turned off, and the DC circuit freewheeling power switch is turned on. During the plasma sustaining phase, the DC loop chopper power switch and the DC loop freewheeling power switch are turned off, while the DC loop shoot-through power switch group is turned on.

2. The high-power torch power supply for plasma application according to claim 1, characterized in that, The number of power circuits n in the main power circuit is determined based on the maximum output power P of the high-power torch power supply: n = P / a; In the formula, a represents the power provided by a power loop, and a ranges from 20 to 80 kW.

3. The high-power torch power supply for plasma application according to claim 1, characterized in that, The DC loop control circuit is also used to determine the stage of the plasma and control the switching on and off of the DC loop soft-switching inverter circuit, the DC loop high-frequency rectifier filter circuit, the DC loop chopper power switch, the DC loop freewheeling power switch, and the DC loop through-power switch group according to the stage of the plasma.

4. A high-power torch power supply for plasma application according to claim 1, characterized in that, The control circuit is also used to determine the stage of the plasma and control the controllable rectifier circuit, soft-switching inverter circuit and high-frequency rectifier filter circuit according to the stage of the plasma.

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