SiC-based double-wire alternate high-frequency pulse MIG welding power supply and system

Abstract

The application discloses a SiC-based double-wire alternating high-frequency pulse MIG welding power supply and system, wherein the welding power supply comprises a power supply power circuit, a digital control system and a man-machine interaction system; the power supply power circuit comprises a master machine, a slave machine low-frequency pulse power supply and a high-frequency pulse power supply, a master-slave two-way synchronous low-frequency pulse current is generated by the master machine and the slave machine low-frequency pulse power supply, two-way alternating high-frequency pulse currents are generated by the high-frequency pulse power supply through a high-frequency chopper circuit, and double-wire alternating high-frequency pulse MIG welding currents are realized through parallel output. The welding power supply only uses a single high-frequency power supply, adopts SiC devices, can reduce the volume and simplify the system, has small switching loss, fast dynamic response, stable output waveform and relatively low cost, and can improve the welding joint quality.

Description

Technical Field

[0001] The present invention relates to the field of welding technology, and in particular to a SiC-based double-wire alternating high-frequency pulse MIG welding power supply and system. Background Art

[0002] Metal Inert-gas Welding (MIG), as an efficient welding technology, plays an important role in the aluminum alloy welding process. With the popularization of digital power supplies, pulsed MIG welding (P-MIG) has strong controllability of droplet transfer and heat input by controlling the peak and base currents, and can be used for welding aluminum alloy thin plates. With the development of power electronics technology and the improvement of industrial technology level, high-frequency pulse current is superimposed on ordinary DC or low-frequency pulse current to make the arc energy more concentrated, and the high-frequency stirring effect on the molten pool can promote the flow of molten metal, refine the grains, and improve the mechanical properties of the welded joint. On this basis, the use of a double-wire method can increase the welding speed and coverage rate, which fully meets the current manufacturing requirements of my country for efficient and high-quality development.

[0003] On the other hand, Si-based IGBTs have a tailing effect and suffer from high switching losses, making it difficult to further increase the current switching frequency of the welding power supply. While Si-based MOSFETs have a higher switching frequency, their withstand voltage and current capacity are relatively low, making them inadequate for high-power welding power supplies. Compared to traditional Si semiconductor devices, SiC has lower on-resistance and lower switching losses, making it more suitable for high-frequency, high-power applications. Using SiC to build a welding power supply system makes it easier to increase the system's switching frequency, efficiency, and control accuracy, promoting the miniaturization and efficiency of power supply systems.

[0004] For twin-wire alternating high-frequency pulse MIG welding, if the traditional DC chopper and secondary inverter dual power supply parallel topology is adopted to generate two alternating high-frequency pulse currents, multiple welding power supplies are required, which is relatively expensive. Summary of the Invention

[0005] In order to achieve a stable and efficient twin-wire pulse MIG welding process, the purpose of the present invention is to provide a SiC-based twin-wire alternating high-frequency pulse MIG welding power supply and system. The power supply system uses a small number of power supplies, reduces the volume, has high energy efficiency, outputs stable high-frequency pulses, and has a fast dynamic response speed. It is suitable for superimposing two alternating high-frequency pulse currents with adjustable amplitude and frequency on the twin-wire synchronous low-frequency pulse current.

[0006] Based on the chopper circuit, the present invention adopts SiC-based MOSFET and diode to provide dual-path alternating high-frequency pulse output through a single high-frequency power supply, thereby achieving high frequency, low cost and high efficiency of the power supply system.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A SiC-based twin-wire alternating high-frequency pulse MIG welding power source, comprising a power circuit, a digital control system, and a human-computer interaction system;

[0009] The power supply circuit includes a host low-frequency pulse power supply, a slave low-frequency pulse power supply and a high-frequency pulse power supply. The host low-frequency pulse power supply and the slave low-frequency pulse power supply generate a master-slave two-way synchronous low-frequency pulse current. The high-frequency pulse power supply generates two alternating high-frequency pulse currents after passing through a high-frequency chopping circuit, and then is connected to the host low-frequency pulse power supply and the slave low-frequency pulse power supply respectively through an anti-backflow SiC diode;

[0010] The positive electrodes of the host low-frequency pulse power supply and the slave low-frequency pulse power supply are connected to the master and slave wire end conductive nozzles respectively, and the negative electrodes thereof are connected to the workpiece;

[0011] The digital control system is connected to the high-frequency pulse power supply, the high-frequency chopping circuit, the host low-frequency pulse power supply and the slave low-frequency pulse power supply respectively through the driving circuit;

[0012] The digital control system also communicates with the human-computer interaction system via a serial port.

[0013] Furthermore, the digital control system includes a low-frequency control circuit and a high-frequency control circuit, which communicate through IO. The two control circuits have the same structure, including an STM32 minimum system, a current and voltage sampling feedback circuit, a fault detection circuit, a SiC MOSFET drive circuit, an IGBT drive circuit and a wire feeding drive circuit.

[0014] Furthermore, the STM32 minimum system is specifically a 32-bit STM32 as a processor, and the digital PWM control signal generated by the STM32 acts on the SiC MOSFET drive circuit, the IGBT drive circuit and the wire feeding drive circuit.

[0015] Furthermore, the human-computer interaction system includes welding parameter setting, welding parameter display and high-frequency pulse output control.

[0016] Furthermore, the host low-frequency pulse power supply and the slave low-frequency pulse power supply both include an input rectifier filter circuit, an IGBT phase-shift full-bridge soft switching circuit, a transformer and an output rectifier filter circuit connected in sequence. The IGBT phase-shift full-bridge soft switching circuit includes four IGBT switching tubes and a resonant inductor, and each IGBT switching tube is respectively connected to the drive circuit of the low-frequency control circuit.

[0017] Furthermore, the high-frequency pulse power supply includes an input rectifier filter circuit, a MOSFET phase-shift full-bridge soft switching circuit, a transformer, an output rectifier filter circuit and a high-frequency chopper circuit in sequence. The MOSFET phase-shift full-bridge soft switching circuit includes four SiC MOSFET switching tubes, a resonant inductor and a DC blocking capacitor.

[0018] Furthermore, the switching frequency of the four SiC MOSFET switching tubes is 80 kHz, wherein the switching tubes of two SiC MOSFETs are leading bridge arms, and the switching tubes of two SiC MOSFETs are lagging bridge arms, and the two bridge arms are connected in parallel to the input rectifier filter circuit.

[0019] Furthermore, the high-frequency chopping circuit is composed of two SiC MOSFET switching tubes connected in parallel.

[0020] Furthermore, the digital control system coordinates the driving signals of each switching tube to ensure that the low-frequency pulse current outputs a low-frequency pulse current waveform with a synchronous phase, and superimposes a high-frequency pulse current with an alternating phase on the base current or peak current or the entire process of the corresponding pulse current according to the program setting of the human-computer interaction system. The two are superimposed to form a double-wire alternating high-frequency pulse MIG welding current without causing backflow.

[0021] A welding system comprises the SiC-based double-wire alternating high-frequency pulse MIG welding power source.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The high-frequency pulse power supply of the present invention uses SiC as the main switching device. The frequency of the inverter circuit can reach 80kHz, which is higher than that of IGBT. The power supply is smaller in size and has a more ideal dynamic response. In addition, since the switching loss and conduction loss of SiC devices are smaller, the energy efficiency of the power supply is improved.

[0024] (2) The high-frequency chopper circuit used in the high-frequency pulse power supply of the present invention can output two alternating high-frequency pulse currents from a single power supply, thereby realizing the alternating output of high-frequency pulse currents of two wires by a single high-frequency pulse power supply, simplifying the system, further reducing the size and cost of the power supply, and being able to reduce to a certain extent the current overshoot caused by the current rise during high-frequency pulse switching and the peak voltage during shutdown.

[0025] (3) The master-slave low-frequency pulse power supply of the present invention adopts a phase-shifted full-bridge soft switching circuit, which reduces switching losses. Moreover, through the digital control of the PI algorithm, it can stably output current waveforms such as DC, pulse current, median current, and double pulses. The welding process is stable and undistorted, which is conducive to promoting the development of double-wire MIG welding.

[0026] (4) The welding system of the present invention combines technologies such as digital control system, phase-shifted full bridge, and high-frequency chopping, and the system has high integration and more precise control. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the welding power supply structure of the present invention;

[0028] Figure 2 It is the low-frequency pulse circuit of the present invention;

[0029] Figure 3 The high-frequency pulse circuit of the present invention;

[0030] Figure 4 1 is a schematic diagram of the welding current waveform of the present invention;

[0031] Figure 5 It is a schematic diagram of the system application structure of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0033] like Figure 1 As shown, this embodiment is a SiC-based double-wire alternating high-frequency pulse MIG welding power supply, including a power circuit, a digital control system and a human-computer interaction system.

[0034] The power circuit includes a master low-frequency pulse power supply, a slave low-frequency pulse power supply, and a high-frequency pulse power supply. The master and slave low-frequency pulse power supplies generate master and slave synchronous low-frequency pulse currents, while the high-frequency pulse power supply generates two alternating high-frequency pulse currents.

[0035] The master and slave low-frequency pulse power supplies share the same structure, including an input rectifier and filter circuit, an IGBT phase-shifted full-bridge soft-switching circuit, a transformer, and an output rectifier and filter circuit, all connected in sequence. The input rectifier and filter circuit is connected to the three-phase AC, and the output rectifier and filter circuit is connected to the main arc load.

[0036] The high-frequency pulse power supply includes an input rectifier and filter circuit, a MOSFET phase-shifted full-bridge soft-switching circuit, a transformer, an output rectifier and filter circuit, and a high-frequency chopper circuit, all connected in sequence. The input rectifier and filter circuit is connected to three-phase AC power. The positive poles of the master and slave low-frequency pulse power supplies are connected to the master and slave wire end contact nozzles, respectively, while the negative poles are connected to the workpiece. After passing through the high-frequency chopper circuit, the high-frequency pulse power supply is connected in parallel to the master and slave low-frequency pulse power supplies via SiC diodes for backflow protection, with the negative poles connected to the workpiece.

[0037] The digital control system utilizes a fully digital control circuit, primarily consisting of a low-frequency control circuit and a high-frequency control circuit. The two control circuits share a similar structure, specifically comprising an STM32 minimum system, current and voltage sampling and feedback circuits, a fault detection circuit, a SiC MOSFET driver circuit, an IGBT driver circuit, and a wire feeder driver circuit. The current and voltage sampling and feedback circuit is connected after the output rectifier and filter circuits. The digital control system communicates with the human-machine interface system via a serial port to implement pre-defined functions. The STM32 minimum system uses a 32-bit STM32 processor, which generates digital PWM control signals that act on the SiC MOSFET driver circuit, IGBT driver circuit, and wire feeder driver circuit. The IGBT driver circuit utilizes an optocoupler-based isolated driver solution, and the SiC MOSFET uses a TI UCC2150 driver chip. The low-frequency and high-frequency control circuits communicate via I / O.

[0038] Figure 1 As shown in the figure: STM32 control chip 1 is the control chip of the master-slave low-frequency pulse power supply, and STM32 control chip 2 is the control chip of the high-frequency pulse power supply.

[0039] The human-computer interaction system includes three functions: welding parameter setting, welding parameter display and high-frequency pulse output control. The above functions are realized through serial communication via a low-frequency control circuit.

[0040] like Figure 2 As shown, in the master and slave low-frequency pulse power supplies, the IGBT phase-shifted full-bridge inverter circuit, or primary inverter circuit, consists of four IGBT switches Q1-Q4 and a resonant inductor L1. Each IGBT switch is connected to the drive circuit of the low-frequency control circuit. The leading bridge arm composed of Q1 and Q2 and the lagging bridge arm composed of Q3 and Q4 are connected in parallel to the three-phase rectifier and filter circuit. The midpoints of the bridge arms are connected in sequence to the resonant inductor L1, the primary side of the transformer T1, and the DC-blocking capacitor C2. The switching frequency is 20kHz. Diodes D1 and D2 are connected to the secondary side of the transformer, and the junction of the diodes is connected to the filter inductor L2, forming the output rectifier and filter circuit. The output is then connected back to the center tap of the transformer secondary through the load.

[0041] like Figure 3As shown, the primary inverter circuit structure in the high-frequency pulse power supply is similar to that of the master-slave low-frequency pulse power supply. The MOSFET phase-shifted full-bridge soft switching circuit uses four SiC-based MOSFETs V1-V4 to replace the IGBTs. The four SiC MOSFETs are connected to the drive circuit on the corresponding control circuit. V1 and V2 are the leading bridge arms, while V3 and V4 are the lagging bridge arms, connected in parallel to the input rectifier and filter circuit; the midpoint of the bridge arm is connected in sequence to the resonant inductor L3, the primary side of the transformer T2, and the DC blocking capacitor C4. The switching frequency is 80kHz to ensure sufficiently high dynamic response characteristics, achieve precise control of the high-frequency current in the subsequent stage, and provide a basis for the stable output of high-frequency pulse current. Diodes D3 and D4 are connected to the secondary of the transformer, and the diode connection is connected to the filter inductor L4 to form an output rectifier filter circuit. After the filter inductor, the circuit is divided into two paths, which are respectively connected to the high-frequency chopping circuit SiC MOSFET switch tubes V5 and V6. Because the MOSFET has a parasitic anti-parallel diode, a loop exists between the master and slave wires during the alternating conduction of V5 and V6. Therefore, anti-backflow SiC diodes D5 and D6 are connected after the switch tubes. Through the diodes, the two high-frequency outputs are respectively connected to the master and slave wires of the double-wire pulse MIG welding, and then connected back to the middle tap of the transformer secondary through the load.

[0042] The working principle of the dual-wire high-frequency pulse MIG welding power supply is: the dual-wire high-frequency pulse MIG welding power supply includes a master-slave low-frequency pulse power supply and a high-frequency pulse power supply. The master and slave low-frequency pulse power supplies supply power to the master wire and the slave wire respectively, while the high-frequency power supply supplies power to the master and slave wires at the same time and outputs in parallel.

[0043] The low-frequency pulse power supply is converted from 380V three-phase AC power input from the grid into a relatively smooth 540V DC power after passing through the three-phase rectifier bridge BR1 and filter capacitor C1. Four PWM signals control the phase-shifted full-bridge soft switching circuit to invert the DC into an AC square wave, which is then electrically isolated, transformed, and power-transmitted through transformer T1 before being converted into a DC output through the output rectifier and filter circuit. The digital control system generates a PWM signal using the PI algorithm based on the difference between the collected output current and the set reference value. The PWM signal is then passed through the IGBT drive circuit to adjust the phase shift angle of the leading and lagging bridge arms to control the common conduction time of the diagonal IGBTs, thereby adjusting the output current amplitude and generating a low-frequency pulse current output.

[0044] The front-stage circuit of the high-frequency pulse power supply is similar to that of the host and slave low-frequency pulse power supplies (host low-frequency pulse power supply and slave low-frequency pulse power supply). It uses SiC-based MOSFET as the switch tube of the phase-shifted full-bridge soft switching circuit. The control method is consistent, and it can obtain a stable DC output with good dynamic response, that is, the peak current of the high-frequency pulse current; the digital control system controls the SiC MOSFET switch tubes V5 and V6 through complementary PWM signals to control the output of the high-frequency pulse current. When V5 is turned off and V6 is turned on, the front-stage current output acts on the master wire. When V5 is turned on and V6 is turned off, the front-stage current output acts on the slave wire. By chopping the DC current, the high-frequency pulse power supply outputs high-frequency pulse current with alternating phases.

[0045] The IGBT switch tubes of the master and slave low-frequency pulse power supplies are connected to the IGBT drive circuit on the low-frequency control circuit, and the MOSFET switch tubes of the high-frequency pulse power supply are connected to the drive circuit on the high-frequency control circuit, so as to output corresponding drive signals to the switch tubes respectively.

[0046] The low-frequency control circuit uses the PI algorithm to adjust the phase-shift angles of the leading and lagging arms of the phase-shifted full-bridge soft-switching circuit, achieving stable output of two low-frequency pulse currents. It also sends waveform state variables in real time to the high-frequency control circuit for controlling the high-frequency output. The high-frequency control circuit uses the PI algorithm to control the current amplitude of the phase-shifted full-bridge soft-switching circuit. It controls the frequency of the high-frequency pulses by alternating the conduction frequency of switches V5 and V6, and outputs high-frequency pulse currents at different stages of the low-frequency pulses based on the settings of the human-computer interaction system or program and the waveform state variables.

[0047] The digital control system coordinates the driving signals of the switching tubes to ensure that the low-frequency pulse current outputs a low-frequency pulse current waveform with a synchronous phase, and according to the program settings of the human-computer interaction system, the high-frequency pulse current of the alternating phase is superimposed on the base current or peak current or the whole process of the corresponding pulse current. The superposition of the two forms a double-wire alternating high-frequency pulse MIG welding current without causing backflow.

[0048] like Figure 4 The figure shows the output current waveform of the double-wire alternating high-frequency pulse MIG welding power supply; the left side is the low-frequency pulse current, and the example uses a low-frequency pulse of 50Hz. The frequency of the high-frequency pulse is above 20kHz, and the two alternating high-frequency pulses are output in parallel to realize the double-wire alternating high-frequency pulse MIG welding current. The high-frequency stirring effect on the molten pool can promote the flow of molten metal, refine the grains, and effectively improve the quality of the weld joint.

[0049] This embodiment also includes a welding system, including the SiC-based double-wire alternating high-frequency pulse MIG welding power source.

[0050] The welding power supply of the present invention can be applied to welding systems, such as Figure 5 As shown in the figure, the welding system works as follows: First, the path of the welding travel platform is planned. The welding workpiece is fixed and moved to the welding starting point, waiting for the synchronization signal from the low-frequency control circuit. The power output is connected, and the welding parameters are set through the human-machine interface. Before welding, the gas supply is activated, and the welding gun switch signal is transmitted to the digital control system through the panel. The master and slave low-frequency pulse power supplies are first activated, and the arc ignition procedure for double-wire welding is performed. The arc ignition success is determined by current detection. After the arc is successfully ignited, the low-frequency control circuit sends a synchronization signal to the travel platform, and the travel platform moves along the predetermined route. The low-frequency pulse power supply outputs synchronized low-frequency pulse currents from both the master and slave channels. IO communication is used to control the high-frequency pulse power supply in real time, superimposing high-frequency pulse currents at the corresponding stages. After welding is completed, the high-frequency pulse power supply and travel platform are turned off, and the low-frequency control circuit executes the arc extinguishing procedure. Among them, the master-slave low-frequency pulse power supply (master and slave low-frequency pulse power supply) can output two independently controllable low-frequency pulse currents, and the high-frequency pulse power supply can simultaneously output two alternating high-frequency pulse currents. The system achieves organic coordination and high-speed collaboration through communication between the low-frequency control circuit and the high-frequency control circuit, thereby improving the level of automation and digitization in the welding process.

[0051] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A SiC-based twin-wire alternating high-frequency pulse MIG welding power source, characterized in that: Including power circuit, digital control system and human-computer interaction system; The power supply circuit includes a host low-frequency pulse power supply, a slave low-frequency pulse power supply and a high-frequency pulse power supply. The host low-frequency pulse power supply and the slave low-frequency pulse power supply generate a master-slave two-way synchronous low-frequency pulse current. The high-frequency pulse power supply generates two alternating high-frequency pulse currents after passing through a high-frequency chopping circuit, and then is connected to the host low-frequency pulse power supply and the slave low-frequency pulse power supply respectively through an anti-backflow SiC diode; The positive electrodes of the host low-frequency pulse power supply and the slave low-frequency pulse power supply are connected to the master and slave wire end conductive nozzles respectively, and the negative electrodes thereof are connected to the workpiece; The digital control system is connected to the high-frequency pulse power supply, the high-frequency chopping circuit, the host low-frequency pulse power supply and the slave low-frequency pulse power supply respectively through the driving circuit; The digital control system also communicates with the human-computer interaction system via a serial port; The high-frequency pulse power supply includes an input rectifier filter circuit, a MOSFET phase-shift full-bridge soft switching circuit, a transformer, an output rectifier filter circuit and a high-frequency chopper circuit in sequence. The MOSFET phase-shift full-bridge soft switching circuit includes four SiC MOSFET switching tubes, a resonant inductor and a DC blocking capacitor. The switching frequency of the four SiC MOSFET switches is 80 kHz, wherein the switching tubes of two SiC MOSFETs are leading bridge arms, and the switching tubes of two SiC MOSFETs are lagging bridge arms, and the two bridge arms are connected in parallel to the input rectifier filter circuit; The high-frequency chopping circuit is composed of two SiC MOSFET switching tubes, and the two switching tubes are connected in parallel.

2. The double-wire alternating high-frequency pulse MIG welding power source according to claim 1, characterized in that: The digital control system includes a low-frequency control circuit and a high-frequency control circuit, which communicate through IO. The two control circuits have the same structure, including an STM32 minimum system, a current and voltage sampling feedback circuit, a fault detection circuit, a SiC MOSFET drive circuit, an IGBT drive circuit, and a wire feeding drive circuit.

3. The double-wire alternating high-frequency pulse MIG welding power source according to claim 2, characterized in that: The STM32 minimum system specifically uses a 32-bit STM32 as a processor, and the digital PWM control signal generated by the STM32 acts on the SiC MOSFET drive circuit, the IGBT drive circuit and the wire feeding drive circuit.

4. The double-wire alternating high-frequency pulse MIG welding power source according to claim 1, characterized in that: The human-computer interaction system includes welding parameter setting, welding parameter display and high-frequency pulse output control.

5. The double-wire alternating high-frequency pulse MIG welding power source according to claim 1, characterized in that: The host low-frequency pulse power supply and the slave low-frequency pulse power supply both include an input rectifier filter circuit, an IGBT phase-shift full-bridge soft switching circuit, a transformer and an output rectifier filter circuit connected in sequence. The IGBT phase-shift full-bridge soft switching circuit includes four IGBT switching tubes and a resonant inductor. Each IGBT switching tube is respectively connected to the drive circuit of the low-frequency control circuit.

6. The double-wire alternating high-frequency pulse MIG welding power source according to any one of claims 1 to 5, characterized in that: The digital control system coordinates the driving signals of each switching tube to ensure that the low-frequency pulse current outputs a low-frequency pulse current waveform with a synchronous phase, and superimposes a high-frequency pulse current with an alternating phase on the base current or peak current or the entire process of the corresponding pulse current according to the program setting of the human-computer interaction system. The two are superimposed to form a double-wire alternating high-frequency pulse MIG welding current without causing backflow.

7. A welding system, characterized in that: A SiC-based twin-wire alternating high-frequency pulse MIG welding power source comprising any one of claims 1-6.

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