Integrated double-wire variable-polarity high-frequency pulse MIG welding power supply system and control method thereof

Abstract

The invention discloses an integrated double-wire variable-polarity high-frequency pulse MIG welding power supply system and a control method thereof. The integrated double-wire variable-polarity high-frequency pulse MIG welding power supply system comprises a three-phase alternating current input power grid, a host power supply, a slave power supply, a digital control circuit, a main arc load and a slave arc load. The host power supply and the slave power supply have the same structure, and each comprises a low-frequency pulse module, a high-frequency pulse module and a secondary inverter circuit. After the double-wire variable-polarity high-frequency pulse is adopted, the double-arc interference is reduced, the stability of double-arc and molten drop transition is enhanced, the advantages of the variable-polarity pulse and the high-frequency pulse are combined, adjustable parameters are increased, and the stability is improved. The effects of variable polarity pulse welding on heat input distribution, deposition rate improvement and cathode cleaning and the effects of high-frequency pulse welding arc energy density, stability and rigidity and comprehensive mechanical property improvement are considered, and high-frequency pulse current is overlaid on variable polarity pulses so that the stability of variable polarity switching and falling of molten drops can be improved. And the welding stability and the welding quality can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of welding, and in particular to an integrated double-wire variable polarity high-frequency pulse MIG welding power supply system and a control method thereof. Background Art

[0002] With the continuous development of aluminum alloy welding technology, aluminum alloy has been widely used. However, aluminum alloy is prone to defects such as hump, undercut, weld collapse or burn-through during welding, and the welding quality is difficult to guarantee, which limits its wide application in different fields.

[0003] Polarity-variable pulse welding is an effective method to improve the welding quality of aluminum alloys. When the DC is positively connected, the base material is the anode and the welding wire is the cathode. During the welding process, the welding wire melts quickly, which can improve the welding efficiency. When the DC is reversely connected, the base material is the cathode and the welding wire is the anode. The anode emits positive ions, which can break and remove the oxide film on the surface of the aluminum alloy base material as the cathode, and has a "cathode cleaning" effect. Polarity-variable pulse welding takes into account the advantages of DC positive connection and DC reverse connection. By adjusting the ratio of the two in the polarity-variable pulse waveform, different welding effects can be obtained. When the negative polarity ratio in the polarity-variable welding waveform increases, the width of the weld increases, the residual height increases, and it also leads to a shallow penetration, which is beneficial for thin plate welding. You can also add a base value before and after the positive polarity of the polarity-variable pulse waveform to reduce the impact of polarity switching and make the arc and droplet transition more stable.

[0004] Superimposing high-frequency pulses on the welding current is also beneficial to the welding of aluminum alloys. High-frequency pulse current can be superimposed not only on ordinary direct current, but also on the peak and base values ​​of pulse current. The frequency and superposition method of high-frequency pulse current are different, and the effects on aluminum alloy welding are also different. By adding high-frequency pulse current, the arc energy can be more concentrated, the arc stability and rigidity can be improved, thereby reducing the impact on droplet transfer and improving welding quality. At the same time, high-frequency pulse current can increase the vertical pressure of the arc, deepen the weld penetration, reduce weld porosity, control heat input, refine the weld regional organization, and improve the weld mechanical properties and weld quality. Summary of the invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the present invention provides an integrated dual-wire variable polarity high-frequency pulse MIG welding power supply system and a control method thereof.

[0006] Based on twin-wire welding, variable polarity pulse welding and high-frequency pulse welding, the present invention proposes an integrated twin-wire variable polarity high-frequency pulse MIG welding power supply system and its control method. In this power supply system, a phase-shifting twin-wire variable polarity high-frequency pulse phase control method is adopted to achieve high-performance current waveform and precise current phase control, reasonably distribute heat input, improve the stability of double arcs and droplet transfer, and thus improve the mechanical properties and quality of the weld.

[0007] Combining variable polarity pulse welding with high-frequency pulse welding, variable polarity high-frequency pulse welding is obtained, which takes into account the effects of variable polarity pulse welding on heat input distribution, improving deposition rate, and cathode cleaning, and the effects of high-frequency pulse welding on improving arc energy density, stability and rigidity, and improving comprehensive mechanical properties.

[0008] The present invention adopts the following technical solution:

[0009] An integrated double-wire variable polarity high-frequency pulse MIG welding power supply system includes a three-phase AC input power grid, a host power supply, a slave power supply, a digital control circuit, a master arc load and a slave arc load;

[0010] The host power supply and the slave power supply have the same structure, both including a low-frequency pulse module, a high-frequency pulse module and a secondary inverter circuit;

[0011] The input ends of the low-frequency pulse module and the high-frequency pulse module are connected to the three-phase AC power grid, and the output ends are connected in parallel to the input end of the secondary inverter circuit;

[0012] The low-frequency pulse module includes an input rectifier filter circuit, an IGBT full-bridge inverter circuit, a transformer and an output rectifier filter circuit which are electrically connected in sequence;

[0013] The high-frequency pulse module comprises a constant current source circuit and a high-frequency pulse chopper circuit electrically connected in sequence;

[0014] The digital control circuit is connected to the host power supply and the slave power supply respectively.

[0015] Furthermore, the constant current source circuit adopts a phase-shifted full-bridge inverter circuit, including an input rectifier filter circuit, a MOSFET full-bridge inverter circuit, a transformer and an output rectifier filter circuit electrically connected in sequence.

[0016] Furthermore, the IGBT full-bridge inverter circuit adopts a phase-shifted full-bridge inverter circuit or a hard-switching full-bridge inverter circuit.

[0017] Furthermore, the digital control circuit includes a voltage and current detection circuit, a fault protection circuit, an IGBT drive circuit, a MOSFET drive circuit, a wire feeding drive circuit, and a first DSP control chip, a second DSP control chip, and a third DSP control chip.

[0018] Furthermore, the PWM generated by the first DSP control chip is used to control the IGBT full-bridge inverter circuit and wire feeding drive circuit of the low-frequency pulse module, the PWM generated by the second DSP control chip is used to control the high-frequency pulse chopper circuit and secondary inverter circuit, and the PWM generated by the third DSP control chip is used to control the MOSFET full-bridge inverter circuit of the constant current source circuit of the high-frequency pulse module.

[0019] Furthermore, the first DSP control chip and the second DSP control chip communicate with each other through isolation optocoupler IO control, and the high-frequency flag signal is transmitted from the first DSP control chip to the second DSP control chip through the isolation optocoupler.

[0020] Furthermore, the high-frequency flag signal is at a high level, indicating that the high-frequency pulse current is superimposed on the peak value of the low-frequency pulse current.

[0021] A control method based on the dual-wire variable polarity high-frequency pulse MIG welding power supply system comprises:

[0022] Realize the output rectification and filtering circuit of the low-frequency pulse module to output low-frequency pulse current;

[0023] Realize constant current output of constant current source of high frequency pulse module;

[0024] Realize the high-frequency pulse module to output high-frequency pulse current;

[0025] Realize polarity-changing pulses on the master wire and the slave wire;

[0026] Realize the phase shift between the master and slave low-frequency pulse currents, with the phase shift range of 0° to 180°.

[0027] Furthermore, the phase angle of the low-frequency pulse current of the host and the slave is first given, and then constant current PI control is performed through the current signal sampled by the voltage and current detection circuit and the given current value, and the drive PWM output by the first DSP control chip is adjusted to achieve phase shifting of the low-frequency pulse current of the host and the slave.

[0028] Furthermore, by changing the conduction time of the two groups of bridge arm IGBTs in the secondary inverter circuit, the duty cycle of the positive and negative polarities of the variable polarity pulse can be changed. As needed, the base current can be added before and after the positive and negative polarities at the same time. There are 14 waveforms in total.

[0029] Beneficial effects of the present invention:

[0030] (1) The present invention adopts variable polarity high-frequency pulse current, which reduces the interference of double arcs and enhances the stability of double arcs and droplet transition. It combines the advantages of variable polarity pulse and high-frequency pulse, taking into account the effects of variable polarity pulse welding on heat input distribution, improving deposition rate, and cathode cleaning, and the effects of high-frequency pulse welding on improving arc energy density, stability and rigidity, and improving comprehensive mechanical properties.

[0031] (2) The present invention integrates twin-wire welding, high-frequency pulse welding and variable polarity pulse welding into an organic whole, thereby reducing the volume of the welding power source.

[0032] (3) Compared with the existing double-wire high-frequency pulse MIG welding power supply system, the hardware circuit of the present invention only adds a secondary inverter circuit, which has a simple structure, small changes, and is easy to maintain.

[0033] (4) After the present invention adopts double-wire variable polarity high-frequency pulses, the high-frequency pulse frequency, high-frequency pulse amplitude, the phase between the master and slave wire pulses, the positive and negative polarity pulse ratio, the positive and negative polarity base value and peak current amplitude, the positive and negative polarity pulse base value and peak current time can be adjusted, and multiple modes of output current can be achieved, so as to make more subtle adjustments and controls to the heat input and droplet transfer process.

[0034] (5) The present invention superimposes a high-frequency pulse current on the polarity-changing pulse, which helps to improve the stability of the polarity-changing switching and the shedding of the molten droplet. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0036] Figure 2 It is a schematic diagram of the main circuit principle of the present invention;

[0037] Figure 3 It is a schematic diagram of the principle of the secondary inverter circuit of the present invention;

[0038] FIG4( a ) is a schematic diagram of current waveforms of the host and slave devices of the present invention when the phase of the polarity-changing pulses is 0°;

[0039] FIG4( b ) is a schematic diagram of current waveforms of the host and slave devices of the present invention with a phase of 180° between the polarity-changing pulses;

[0040] FIG4( c ) is a schematic diagram of current waveforms of the host and slave devices of the present invention when the polarity pulse phase is a random phase φ (0°<φ<180°);

[0041] FIG4(d) is a current waveform of the base value after adding the positive polarity of the variable polarity pulse of the present invention;

[0042] FIG4(e) is a current waveform of the base value before adding the positive polarity of the variable polarity pulse of the present invention;

[0043] FIG4( f ) is a current waveform of the base value before adding the negative polarity pulse of the present invention;

[0044] FIG4( g ) is a current waveform of the base value after adding a negative polarity pulse of the present invention;

[0045] FIG4(h) is a current waveform of the base value before and after adding the positive polarity of the variable polarity pulse of the present invention;

[0046] FIG4(i) is a current waveform of the base value before and after the addition of the positive polarity of the variable polarity pulse and the base value after the addition of the negative polarity;

[0047] FIG4(j) is a current waveform of the base value before and after the addition of the positive polarity of the variable polarity pulse and the base value before the addition of the negative polarity pulse of the present invention;

[0048] FIG4(k) is a current waveform of the base value before adding the positive polarity pulse and after adding the negative polarity pulse of the present invention;

[0049] FIG4(l) is a current waveform of the base value before adding the positive polarity pulse and the base value before adding the negative polarity pulse of the present invention;

[0050] FIG4(m) is a current waveform of the base value after adding the positive polarity pulse and the base value after adding the negative polarity pulse of the present invention;

[0051] FIG4(n) is a current waveform of the base value after adding the positive polarity of the variable polarity pulse and the base value before adding the negative polarity pulse of the present invention;

[0052] FIG5( a ) is a flow chart of a method for controlling a low-frequency pulse current according to the present invention;

[0053] FIG5( b ) is a flow chart of a method for controlling high-frequency pulse current according to the present invention;

[0054] FIG5(c) is a flow chart of the control method of the variable polarity high frequency pulse current of the present invention. DETAILED DESCRIPTION

[0055] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0056] Example

[0057] like Figure 1 As shown, an integrated double-wire variable polarity high-frequency pulse MIG welding power supply system includes a host power supply, a slave power supply, a digital control circuit, a main arc load and a slave arc load.

[0058] The host power supply comprises a host low-frequency pulse module, a host high-frequency pulse module and a host secondary inverter circuit.

[0059] The input ends of the host low-frequency pulse module and the host high-frequency pulse module are connected to the three-phase AC power grid, and the output ends are connected in parallel as the input of the host secondary inverter circuit, and the output of the host secondary inverter circuit is connected to the main arc load.

[0060] The slave power supply includes a slave low-frequency pulse module, a slave high-frequency pulse module and a slave secondary inverter circuit.

[0061] The input ends of the slave low-frequency pulse module and the slave high-frequency pulse module are connected to the three-phase AC power grid, and the output ends are connected in parallel as the input of the slave secondary inverter circuit, and the output of the slave secondary inverter circuit is connected to the slave arc load.

[0062] The host low-frequency pulse module and the slave low-frequency pulse module have the same structure, and both include an input rectifier filter circuit, an IGBT full-bridge inverter circuit, a transformer, and an output rectifier filter circuit that are electrically connected in sequence.

[0063] The host high-frequency pulse module and the slave high-frequency pulse module have the same structure, and both include a constant current source circuit and a high-frequency pulse chopping circuit that are electrically connected in sequence.

[0064] The digital control circuit includes a voltage and current detection circuit, a fault protection circuit, an IGBT drive circuit, a MOSFET drive circuit, a wire feeding drive circuit, a first DSP control chip, a second DSP control chip, and a third DSP control chip.

[0065] One end of the fault protection circuit is connected to the first DSP control chip and the third DSP control chip, and the other end is connected to the main circuit input end.

[0066] One end of the IGBT drive circuit is connected to the first DSP control chip, and the other end thereof is connected to the IGBT full-bridge inverter circuit in the low-frequency pulse module.

[0067] One end of the MOSFET driving circuit is connected to the second DSP control chip and the third DSP control chip, and the other end is connected to the MOSFET of the high-frequency pulse chopper circuit and the MOSFET full-bridge inverter circuit of the constant current source circuit in the high-frequency pulse module.

[0068] One end of the wire feeding drive circuit is connected to the first DSP control chip, and the other end thereof is connected to the wire feeding machine.

[0069] The first DSP control chip and the second DSP control chip are communicatively connected by using isolated optical coupling IO control.

[0070] like Figure 2 The main circuit of the present invention is shown. Taking the host power supply as an example, the input ends of the host low-frequency pulse module and the host high-frequency pulse module are connected to the three-phase AC power grid, and the output ends are connected in parallel as the input of the host secondary inverter circuit, and the output of the host secondary inverter circuit is connected to the main arc load.

[0071] The IGBT full-bridge inverter circuit of the low-frequency pulse module adopts a phase-shifted full-bridge inverter circuit or a hard-switching full-bridge inverter circuit.

[0072] The constant current source circuit of the high-frequency pulse module adopts a phase-shifted full-bridge circuit, including an input rectification and filtering circuit, a MOSFET full-bridge inverter circuit, a transformer and an output rectification and filtering circuit.

[0073] like Figure 3The secondary inverter circuit of the present invention is shown, which is an IGBT full-bridge inverter hard switch circuit. The ratio of the positive and negative polarities of the variable polarity pulse is adjusted by changing the opening time and switching sequence of the two groups of bridge arm IGBTs of the secondary inverter circuit.

[0074] Specifically, if Figure 3 As shown, Q1 and Q4 form a group of IGBT tubes, and Q2 and Q3 form a group of IGBT tubes.

[0075] like Figure 4(a)-Figure 4(c) As shown, the current waveforms of the host and slave variable polarity pulses at different phases are adjusted by adjusting the phase difference between the PWM of the secondary inverter circuit and the high-frequency pulse chopper circuit of the host power supply and the PWM of the secondary inverter circuit and the high-frequency pulse chopper circuit of the slave power supply, so that the phase of the variable polarity high-frequency pulses of the master wire and the slave wire is adjusted between 0° and 180°, which is conducive to realizing the control of the current phase.

[0076] like Figure 4(d)-Figure 4(n) As shown, the polarity-changing pulse can add a base current before and after the positive and negative polarity waveforms by changing the turn-on time and switching order of the two groups of bridge arm IGBTs of the secondary inverter circuit, which is beneficial to improving the stability of the polarity-changing high-frequency pulse waveform during polarity switching.

[0077] like Figure 5(a)-Figure 5(c) As shown, a control method for an integrated dual-wire variable polarity high-frequency pulse MIG welding power supply system is as follows:

[0078] To achieve low-frequency pulse module output low-frequency pulse current: set the phase angle between the host and slave low-frequency pulses, set the high-frequency flag, and set the given peak current I p , I p and the peak feedback current I collected by the voltage and current detection circuit pf Together, they are controlled by constant current PI to obtain a constant peak current. Then the high frequency flag is reset and the given base current I is set. b , I b And the base feedback current I collected by the voltage and current detection circuit bf Together, a constant base current is obtained through constant current PI control.

[0079] Realize constant current of high-frequency pulse module: given reference current I h , I h Together with the current signal collected by the voltage and current detection circuit, it is controlled by constant current PI to adjust the phase shift angle of the high-frequency pulse module constant current source driving PWM and output a constant current.

[0080] The high-frequency pulse chopping circuit includes a fifth transistor V5, a sixth transistor V6, a third diode D3, a first resistor R1 and a third inductor L3;

[0081] To realize the high-frequency pulse chopping circuit to output high-frequency pulses: set the frequency of the high-frequency pulse and determine whether the high-frequency flag is set. If the high-frequency flag is 1, V5 is turned off and V6 is turned on; if the high-frequency flag is 0, V5 is turned off and V6 is turned on, thereby outputting high-frequency pulse current.

[0082] The secondary inverter circuit performs secondary inversion on the current with high and low pulses superimposed: by changing the conduction time of Q1, Q4 and Q2, Q3, the duty cycle of the positive and negative polarity of the variable polarity pulse can be changed, and base values ​​can be added before and after the positive and negative polarity waveforms as needed.

[0083] Specifically, the high-frequency pulse current passes through the high-frequency marker to ensure that it is superimposed on the peak value of the low-frequency pulse current.

[0084] The secondary inverter circuit changes the conduction time of Q1, Q4 and Q2, Q3 during secondary inverter, that is, changes the duty cycle of the driving PWM.

[0085] 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 equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An integrated dual-wire variable polarity high-frequency pulse MIG welding power supply system, characterized in that: It includes a three-phase AC input power grid, a host power supply, a slave power supply, a digital control circuit, a main arc load and a slave arc load; The host power supply and the slave power supply have the same structure, both including a low-frequency pulse module, a high-frequency pulse module and a secondary inverter circuit; The input ends of the low-frequency pulse module and the high-frequency pulse module are connected to the three-phase AC power grid, and the output ends are connected in parallel to the input end of the secondary inverter circuit; The low-frequency pulse module includes an input rectifier filter circuit, an IGBT full-bridge inverter circuit, a transformer and an output rectifier filter circuit which are electrically connected in sequence; The high-frequency pulse module comprises a constant current source circuit and a high-frequency pulse chopper circuit electrically connected in sequence; The digital control circuit is connected to the host power supply and the slave power supply respectively.

2. The double-wire variable polarity high-frequency pulse MIG welding power supply system according to claim 1 is characterized in that: The constant current source circuit adopts a phase-shifted full-bridge inverter circuit, which includes an input rectifier filter circuit, a MOSFET full-bridge inverter circuit, a transformer and an output rectifier filter circuit which are electrically connected in sequence.

3. The double-wire variable polarity high-frequency pulse MIG welding power supply system according to claim 1 is characterized in that: The IGBT full-bridge inverter circuit adopts a phase-shifted full-bridge inverter circuit or a hard-switching full-bridge inverter circuit.

4. The double-wire variable polarity high-frequency pulse MIG welding power supply system according to any one of claims 1 to 3, characterized in that: The digital control circuit includes a voltage and current detection circuit, a fault protection circuit, an IGBT drive circuit, a MOSFET drive circuit, a wire feeding drive circuit, a first DSP control chip, a second DSP control chip, and a third DSP control chip.

5. The double-wire variable polarity high-frequency pulse MIG welding power supply system according to claim 4 is characterized in that: The PWM generated by the first DSP control chip is used to control the IGBT full-bridge inverter circuit and wire feeding drive circuit of the low-frequency pulse module, the PWM generated by the second DSP control chip is used to control the high-frequency pulse chopper circuit and secondary inverter circuit, and the PWM generated by the third DSP control chip is used to control the MOSFET full-bridge inverter circuit of the high-frequency pulse module.

6. The double-wire variable polarity high-frequency pulse MIG welding power supply system according to claim 5, characterized in that: The first DSP control chip and the second DSP control chip communicate with each other through the isolation optocoupler IO control, and the high-frequency flag signal is transmitted from the first DSP control chip to the second DSP control chip through the isolation optocoupler.

7. The double-wire variable polarity high-frequency pulse MIG welding power supply system according to claim 6, characterized in that: The high-frequency flag signal is at a high level, indicating that the high-frequency pulse current is superimposed on the peak value of the low-frequency pulse current.

8. A control method for a double-wire variable polarity high-frequency pulse MIG welding power supply system according to any one of claims 1 to 7, characterized in that: include: Realize the output rectification and filtering circuit of the low-frequency pulse module to output low-frequency pulse current; Realize constant current output of constant current source of high frequency pulse module; Realize the high-frequency pulse module to output high-frequency pulse current; Realize polarity-changing pulses on the master wire and the slave wire; Realize the phase shift between the master and slave low-frequency pulse currents, with the phase shift range of 0° to 180°.

9. The control method according to claim 8, characterized in that: First, the phase angle of the low-frequency pulse current of the host and the slave is given, and then the constant current PI control is performed through the current signal sampled by the voltage and current detection circuit and the given current value, and the drive PWM output by the first DSP control chip is adjusted to achieve the phase shift of the low-frequency pulse current of the host and the slave.

10. The control method according to claim 8, characterized in that: By changing the conduction time of the two groups of bridge arm IGBTs in the secondary inverter circuit, the duty cycle of the positive and negative polarity of the variable polarity pulse can be changed. As needed, base current can be added before and after the positive and negative polarities. There are 14 waveforms in total.

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