Regulation and control method and system for direct-current arc plasma power supply

Abstract

The invention belongs to the technical field of arc plasma power supplies, and particularly relates to a regulation and control method and system for a direct-current arc plasma power supply, and the method comprises the steps: providing a power supply circuit system which comprises a direct-current power supply module, an inversion rectification module, a voltage compensation module, a steady-current inductor and an arc load which are connected in sequence, and a current negative feedback drive control circuit and a voltage positive feedback drive control circuit. The current negative feedback driving control circuit adjusts the output voltage of the inversion rectification module in a negative feedback mode so as to change the output current. When the forward fluctuation of the voltage pulse of the arc load exceeds the output voltage of the inversion rectification module by a certain proportion, the voltage positive feedback driving control circuit performs voltage compensation by controlling the voltage compensation module; the arc breaking problem caused by large fluctuation of accidental pulse of load voltage is fundamentally solved, stable operation of the arc load can be effectively guaranteed, and the production efficiency and the product quality are improved.

Description

Technical Field

[0001] This invention belongs to the field of arc plasma power supply technology, specifically relating to a control method and system for DC arc plasma power supply. Background Technology

[0002] DC arc plasma power supplies, as key energy conversion devices, have been widely used in industrial fields such as plasma cutting, welding, smelting, hazardous waste treatment, and materials synthesis. Their basic function is to convert AC grid power into DC power suitable for arc loads through rectification, inversion, high-frequency transformation, and further rectification. However, due to the significant negative resistance and dynamic instability of arc plasma during operation, existing power supplies exhibit poor arc stability under load fluctuations, making them prone to arc interruption.

[0003] Patent application number 201911120776.6 discloses a DC arc plasma power supply and system. This power supply and system includes an input rectifier module, an inverter module, a high-frequency transformer module, an output rectifier module, and a power output terminal connected in sequence. It also includes a "voltage compensation module," whose compensation voltage output terminal is connected in series with the DC terminal of the output rectifier module. The voltage output terminal of this series connection is then connected to the power output terminal. Simultaneously with the DC arc-initiating voltage output from the output rectifier module, the voltage compensation module outputs a compensation voltage in the same direction as the DC arc-initiating voltage. This invention aims to solve the technical problem of insufficient high voltage required for arc initiation. By using a voltage compensation module that operates simultaneously with the main output during arc initiation, a compensation voltage is superimposed to assist in breaking down the gas medium and reliably completing the initial arc ignition. Essentially, it is a high-voltage ignition module. However, the triggering and control of the compensation action in this technical solution is for the instantaneous event of arc initiation. Once the arc is established, the compensation task is completed. Its design goal does not include dynamic response and compensation for load fluctuations that occur during continuous operation after the arc is established.

[0004] In actual use of plasma processing equipment, the plasma arc may experience rapid, random pulse fluctuations exceeding the power supply voltage due to factors such as changes in the workpiece surface condition and environmental airflow disturbances. When the arc is unexpectedly elongated or its physical state undergoes a sudden change, the arc voltage spikes instantaneously. If the power supply cannot immediately provide a matching higher voltage, the arc current will rapidly decay, power will plummet, and ultimately, the arc will break. Arc breakage directly causes process interruption, reduced processing quality, decreased production efficiency, and may damage the electrodes and torch. To address this problem, traditional power supplies generally use a large-inductance current-stabilizing reactor after output rectification to smooth current pulsations, or increase the rated value of the rectified output voltage, resulting in increased energy consumption and higher equipment costs. Therefore, developing a control system and method capable of intelligently detecting the arc plasma operating state and rapidly compensating for pulse fluctuations in the working arc is of significant practical importance for improving the reliability, automation level, and overall efficiency of plasma processes. Summary of the Invention

[0005] The purpose of this invention is to provide a method for regulating a DC arc plasma power supply, enabling it to intelligently detect the operating status of the arc plasma and rapidly compensate and regulate the fluctuations of the working arc, thereby improving the reliability, automation level, and overall efficiency of the plasma process.

[0006] This invention is achieved through the following technical solution: A method for controlling a DC arc plasma power supply includes the following steps: S1: Provide a power supply circuit system, the power supply circuit system including a DC power supply module, an inverter rectifier module, a voltage compensation module, a current stabilizing inductor and an arc load connected in sequence, as well as a current negative feedback drive control circuit and a voltage positive feedback drive control circuit. S2: The current negative feedback drive control circuit includes at least a load current detection circuit and a current stabilization control circuit. The current negative feedback drive control circuit adjusts the output voltage of the inverter rectifier module through negative feedback, thereby stabilizing the current of the arc load. S3: The voltage positive feedback drive control circuit includes at least an arc load voltage detection circuit and a compensation power supply control circuit. When the arc load voltage pulse positive fluctuation exceeds the set value, the voltage positive feedback drive control circuit will perform voltage compensation by controlling the voltage compensation module. The arc load voltage detection circuit detects the voltage value of the arc load in real time and compares the detected voltage value with a preset voltage threshold. When the detected arc load voltage value is higher than the voltage threshold, the compensation power supply control circuit will turn on the power supply switch in the voltage compensation module, and the voltage compensation module will input a compensation voltage in the same direction to the output terminal of the inverter rectifier module. When the detected arc load voltage value does not exceed the voltage threshold, the compensation power supply control circuit will turn off the power supply switch in the voltage compensation module, so that it stops outputting the compensation voltage.

[0007] As a further feature of the above scheme, the voltage compensation module does not output compensation voltage during the arc initiation stage of the arc load.

[0008] As a specific setting of the above scheme, the voltage threshold is greater than 70% of the highest value of the power supply output voltage under the rated load of the arc load.

[0009] As a specific configuration of the above scheme, the compensation voltage output terminal of the voltage compensation module is connected in series or in parallel with the DC output terminal of the inverter rectifier module, and the direction of the compensation voltage is the same as the direction of the voltage output by the inverter rectifier module.

[0010] As a specific setting of the above scheme, the compensation voltage output by the voltage compensation module is processed by the transformer module and the diode rectifier module to transform and rectify the external AC power, and the processed compensation voltage is then controlled by the power switch to compensate the output.

[0011] As a specific setting of the above scheme, the compensation voltage output by the voltage compensation module is obtained from the AC power in the inverter rectifier module by the additional winding of the high-frequency transformer, and then rectified by the diode rectifier module before being controlled by the power switch to compensate the output.

[0012] As a specific feature of the above scheme, the compensation voltage output by the voltage compensation module is rectified by the diode rectifier module and then stored in an energy storage capacitor.

[0013] As a specific configuration of the above scheme, the inverter rectifier module includes an inverter module, a high-frequency transformer module, and an output rectifier module connected in sequence.

[0014] The present invention also provides a circuit system for a DC arc plasma power supply, which is the power supply circuit system provided in step S1 above.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention overcomes the limitations of existing technologies that only focus on voltage compensation at the moment of "arc initiation" and proposes a dynamic control mechanism based on positive feedback of load voltage. This power supply circuit system can detect abnormal voltage pulse increases caused by arc elongation and disturbances during operation in real time, and immediately trigger the voltage compensation module for precise voltage injection. This allows the power supply to actively adapt to positive voltage pulse changes during arc load operation, fundamentally solving the problem of arc interruption caused by occasional large fluctuations in load voltage pulses. It effectively ensures the stable operation of the arc load, improves production efficiency and product quality, and achieves a technological leap from "one-time arc initiation assistance" to "full-process dynamic arc stabilization."

[0016] This invention constructs a collaborative intelligent control architecture of "current negative feedback for base stabilization and voltage positive feedback for disturbance suppression." This control architecture is not a simple replacement or superposition of control loops, but rather a well-defined, highly efficient dual-loop control system. The load current negative feedback loop, as the main loop, is responsible for maintaining the long-term steady state and precise adjustment of the arc working current; the load voltage positive feedback loop, as a fast auxiliary loop, is specifically used to detect and suppress sudden positive pulse fluctuations in the load voltage, thereby effectively ensuring the stable operation of the arc load and improving production efficiency and product quality.

[0017] This invention also provides various implementation schemes for voltage compensation modules (such as independent controllable sources, power drawn from the main transformer, etc.), which can flexibly adapt to power supply designs with different power levels and cost requirements. At the same time, the key protection design in the voltage compensation module circuit (such as freewheeling diodes) effectively suppresses voltage spikes generated by switching operations, protects power devices, and improves the long-term operational reliability of the entire power supply system.

[0018] Compared to the traditional approach of passively dissipating energy with a "large inductance reactor" to smooth the current or increase the rated value of the rectified output voltage, this invention employs an active intelligent compensation strategy that only instantaneously injects energy when the arc fluctuates, avoiding energy loss of the inductor under continuous conduction, thus significantly improving the overall operating energy efficiency of the DC arc plasma. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the control method for the DC arc plasma power supply in this invention; Figure 2 This is a circuit diagram of the power supply circuit system in Embodiment 1 of the present invention; Figure 3 This is a circuit diagram of the power supply circuit system in Embodiment 2 of the present invention; Figure 4 This is a circuit diagram of the power supply circuit system in Embodiment 3 of the present invention; Figure 5 This is a circuit diagram of the power supply circuit system in Embodiment 4 of the present invention; Figure 6 This is a circuit diagram of the first type of rectifier circuit for the compensation voltage module in this invention; Figure 7 This is a circuit diagram of the second type of rectifier circuit for the compensation voltage module in this invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0022] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The following will refer to the appendix... Figures 1-7 This application will be described in detail with reference to the embodiments.

[0023] This invention discloses a method for controlling a DC arc plasma power supply, which is implemented based on a specially designed power supply circuit system. (See attached document.) Figure 1 and attached Figure 2 The power supply circuit system includes a complete power supply circuit consisting of a DC power supply module 10, an inverter rectifier module 20, a voltage compensation module 30, a current stabilizing inductor 40, an arc load 50, a current negative feedback drive control circuit 60, and a voltage positive feedback drive control circuit 70.

[0024] The DC power supply module 10 includes an input rectifier module and an external power grid. The AC terminal of the input rectifier module is connected to the power grid, thereby converting the AC power from the power grid into DC power.

[0025] The inverter rectifier module 20 includes an inverter module, a high-frequency transformer module, and an output rectifier module. The inverter module converts the DC power output from the input rectifier module into high-frequency AC power. The inverter module adopts a full-bridge topology and contains four insulated-gate bipolar transistors as switching transistors, labeled VT1 to VT4 in the circuit. A freewheeling diode is connected in reverse parallel between the collector and emitter of each switching transistor, labeled VD1 to VD4 in the circuit, to provide a freewheeling path for inductive loads and absorb turn-off spikes.

[0026] The high-frequency transformer module boosts the high-frequency AC output from the inverter module for subsequent rectification. The high-frequency transformer module includes a primary winding N1 and a secondary winding N2. The primary winding N1 is connected to the output of the inverter module, and the secondary winding N2 is connected to the input of the output rectifier module to provide the main power current.

[0027] The output rectifier module rectifies the high-frequency AC power output from the high-frequency transformer module into DC power. The output rectifier module is a single-phase full-bridge rectifier circuit composed of four diodes (VD5-VD8). Its AC input terminal is connected to the main and secondary windings N2 of the high-frequency transformer module, and its DC output terminal outputs a pulsating DC voltage.

[0028] The current-regulating inductor 40 filters the rectified DC power to reduce current ripple and improve the stability of the power output. It is connected in series with the current-regulating inductor L1 at the DC output terminal of the output rectifier module. The small inductance value of the current-regulating inductor L1 smooths the output current and voltage, further improving the stability of the power output. Finally, the entire DC power supply output, after being processed by the current-regulating inductor 40, is used to connect the arc load 50.

[0029] The core of this invention lies in the design of the current negative feedback drive control circuit 60, the voltage positive feedback drive control circuit 70, and the voltage compensation module 30. The current negative feedback drive control circuit 60 includes at least a load current detection circuit and a current stabilization control circuit. The load current detection circuit monitors the magnitude of the current input to the arc load 50 after filtering and rectification online, while the current stabilization control circuit performs negative feedback regulation on the inverter rectifier module 20. When a decrease in load current is detected, the inverter rectifier module 20 increases the output DC voltage to ensure stable output from the DC power supply module 10.

[0030] The compensation voltage output terminal of the voltage compensation module 30 is connected in series or in parallel with the DC output terminal of the output rectifier module, and the direction of its compensation voltage is the same as the direction of the voltage of the output rectifier module. Simultaneously, the output voltage of the voltage compensation module 30 is controlled by the voltage positive feedback drive control circuit 70.

[0031] The voltage positive feedback drive control circuit 70 includes at least an arc load voltage detection circuit and a compensation power supply control circuit. When the arc load voltage detection circuit detects that the load voltage exceeds the specified voltage (e.g., 70% of the highest output voltage of the power supply under the rated load of the arc load), the compensation power supply control circuit controls the power supply switch in the voltage compensation module 30 to open and output full voltage. When the load voltage is lower than the specified voltage, the voltage compensation module 30 outputs zero voltage. This invention, through this dynamic closed-loop control method, can promptly provide the required high voltage when the voltage of the arc load 50 experiences positive pulse fluctuations, and when the amplitude of the positive pulse fluctuations is large, ensuring stable arc combustion. Furthermore, the voltage compensation module 30 does not output compensation voltage during the arc ignition phase of the arc load.

[0032] In the specific design, the arc load voltage detection circuit includes a protection resistor R1 and a detection resistor R2 connected in parallel across the arc load 50. A voltage detection module, which can be a voltage sensor, is connected in parallel across the detection resistor R2. The voltage sensor obtains a low-voltage analog signal proportional to the load voltage, which is then connected to a microcontroller with a preset threshold voltage. Finally, the compensation power supply control circuit controls the power supply switch (transistor switch VT5) in the voltage compensation module 30 to open or close. Example 1

[0033] Example 1 discloses a specific implementation of a voltage compensation module 30, see attached figure. Figure 2 In this embodiment 1, a controllable DC compensation voltage output module consisting of a "rectifier circuit-voltage compensation control switch circuit" is connected in series at the output terminal of the output rectifier module.

[0034] The rectifier circuit in this controllable DC compensation voltage output module consists of a transformer module, a diode-based rectifier module (which can be a half-wave rectifier with a single diode or a full-bridge rectifier circuit with four diodes), and a parallel energy storage capacitor. The voltage compensation control switch circuit includes a power input switch (specifically, a transistor switch VT5) connected in series at the output of the rectifier circuit. This power input switch is controlled by a voltage positive feedback drive control circuit 70, thus forming a closed-loop process of "sensing-decision-execution".

[0035] Finally, a freewheeling diode VD9 is connected in parallel across the two ends of the controllable DC compensation voltage output module. This freewheeling diode VD9 is used to provide a freewheeling path for the inductive components in the module when the voltage compensation module 30 stops outputting or the internal switching devices are turned off, to absorb and release the magnetic energy stored therein, thereby suppressing voltage spikes, protecting the controllable rectifier devices and transistor switches, and improving the reliability of the system. Example 2

[0036] Example 2 discloses a specific implementation of a voltage compensation module 30, see attached figure. Figure 3 In this embodiment 2, a controllable DC compensation voltage output module consisting of a "rectifier circuit - voltage compensation control switch circuit" is connected in parallel at the output terminal of the output rectifier module.

[0037] The specific controllable DC compensation voltage output module is the same as in Example 1, consisting of a transformer module, a rectifier module composed of diodes (the rectifier module can be a half-wave rectifier composed of a single diode or a full-bridge rectifier circuit composed of four diodes), and a parallel energy storage capacitor. The voltage compensation control switch circuit includes a power input switch (specifically, a transistor switch VT5) connected in series at the output of the rectifier circuit. This power input switch is controlled by the voltage positive feedback drive control circuit 70, thereby forming a closed-loop process of "sensing-decision-execution".

[0038] Finally, when the controllable DC compensation voltage output module is connected in parallel to the output terminal of the output rectifier module, the capacitor C1 in the original power supply circuit system is removed, and the freewheeling diode VD9 is not set. Example 3

[0039] Example 3 discloses a specific implementation of a voltage compensation module 30, see attached figure. Figure 4 In this embodiment 3, a voltage output module consisting of "high-frequency transformer additional winding - diode rectification - series switch - parallel diode" is connected in series at the low voltage terminal of the output rectifier module to ground.

[0040] The high-frequency transformer additional winding N3 in the voltage output module is used to obtain the output voltage of the primary winding N1 and boost it for output. The diode rectification is the same as in Example 1; it can be a half-wave rectifier composed of a single diode or a full-bridge rectifier circuit composed of four diodes. An energy storage capacitor is connected in parallel at the output of the rectifier circuit, and a power input switch (transistor switch VT5) is connected in series at the output of the rectifier circuit. This allows the power input switch to be controlled by the voltage positive feedback drive control circuit 70, thus forming a closed-loop process of "sensing-decision-execution".

[0041] Finally, a freewheeling diode VD9 is connected in parallel at the output of the rectifier circuit. This freewheeling diode VD9 is used to provide a freewheeling path for the inductive components in the module when the voltage compensation module 30 stops outputting or the internal switching devices are turned off, to absorb and release the magnetic energy stored therein, thereby suppressing voltage spikes, protecting the controllable rectifier devices and transistor switches, and improving the reliability of the system. Example 4

[0042] Example 4 discloses a specific implementation of a voltage compensation module 30, see attached figure. Figure 5 In this embodiment 4, a voltage output module consisting of "high-frequency transformer additional winding - diode rectification - series switch - parallel diode" is connected in parallel to the low voltage terminal of the output rectifier module.

[0043] The specific voltage output module is the same as in Example 3. It uses an additional winding N3 of a high-frequency transformer to obtain the output voltage of the primary winding N1 and boost it for output. The diode rectification can be a half-wave rectification composed of a single diode or a full-bridge rectifier circuit composed of four diodes. An energy storage capacitor is connected in parallel at the output of the rectifier circuit, and a power input switch (transistor switch VT5) is connected in series at the output of the rectifier circuit. This allows the power input switch to be controlled by the voltage positive feedback drive control circuit 70, thus forming a closed-loop process of "sensing-decision-execution".

[0044] Finally, when the voltage output module is connected in parallel to the output terminal of the output rectifier module, the capacitor C1 in the original power supply circuit system is removed, and the freewheeling diode VD9 is not installed.

[0045] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling a DC arc plasma power supply, characterized in that, Includes the following steps: S1: Provide a power supply circuit system, the power supply circuit system including a DC power supply module, an inverter rectifier module, a voltage compensation module, a current stabilizing inductor and an arc load connected in sequence, as well as a current negative feedback drive control circuit and a voltage positive feedback drive control circuit. S2: The current negative feedback drive control circuit includes at least a load current detection circuit and a current stabilization control circuit. The current negative feedback drive control circuit adjusts the output voltage of the inverter rectifier module through negative feedback, thereby stabilizing the current of the arc load. S3: The voltage positive feedback drive control circuit includes at least an arc load voltage detection circuit and a compensation power supply control circuit. When the arc load voltage pulse positive fluctuation exceeds the set value, the voltage positive feedback drive control circuit will perform voltage compensation by controlling the voltage compensation module. The arc load voltage detection circuit detects the voltage value of the arc load in real time and compares the detected voltage value with a preset voltage threshold. When the detected arc load voltage value is higher than the voltage threshold, the compensation power supply control circuit will turn on the power supply switch in the voltage compensation module, and the voltage compensation module will input a compensation voltage in the same direction to the output terminal of the inverter rectifier module. When the detected arc load voltage value does not exceed the voltage threshold, the compensation power supply control circuit will turn off the power supply switch in the voltage compensation module, so that it stops outputting the compensation voltage.

2. The method for controlling a DC arc plasma power supply according to claim 1, characterized in that, The voltage compensation module does not output compensation voltage during the arc initiation stage of the arc load.

3. The method for controlling a DC arc plasma power supply according to claim 1, characterized in that, The voltage threshold is greater than 70% of the highest output voltage of the power supply under the rated load of the arc load.

4. The method for controlling a DC arc plasma power supply according to claim 1, characterized in that, The compensation voltage output terminal of the voltage compensation module is connected in series or in parallel with the DC output terminal of the inverter rectifier module, and the direction of the compensation voltage is the same as the direction of the voltage output by the inverter rectifier module.

5. The method for controlling a DC arc plasma power supply according to claim 4, characterized in that, The compensation voltage output by the voltage compensation module is obtained by the transformer module and the diode rectifier module transforming and rectifying the external AC power. The processed compensation voltage is then controlled by the power switch to output the compensation.

6. The method for controlling a DC arc plasma power supply according to claim 4, characterized in that, The compensation voltage output by the voltage compensation module is obtained from the AC power in the inverter rectifier module by the additional winding of the high-frequency transformer, and then rectified by the diode rectifier module before being controlled by the power switch to compensate the output.

7. The method for controlling a DC arc plasma power supply according to claim 5 or 6, characterized in that, The compensation voltage output by the voltage compensation module is rectified by the diode rectifier module and then stored in an energy storage capacitor.

8. The method for controlling a DC arc plasma power supply according to claim 1, characterized in that, The inverter rectifier module includes an inverter module, a high-frequency transformer module, and an output rectifier module connected in sequence.

9. A circuit system for a DC arc plasma power supply, characterized in that, The circuit system is the power supply circuit system provided in step S1 of any one of claims 1 to 8.

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