A high-precision feedforward and feedback control system and method for an inverter DC welding machine

Abstract

The application provides a kind of inverter DC welding machine feedforward high-precision feedback control system and method, it is related to inverter DC welding machine control technical field.The voltage sampling end of the system is set between full-bridge rectifier module and output reactor, and the current sampling end is set between output reactor and output terminal.The application effectively avoids inductance back electromotive force and cable voltage drop interference by placing voltage sampling point in front of output reactor, significantly improves feedback sampling accuracy by combining isolated sampling and anti-interference filter circuit;At the same time, a feedforward compensation module is introduced, which calculates the reactor and cable voltage drop in advance according to the real-time welding current and adds it to the control signal to form a "feedforward compensation + high-precision feedback" dual mechanism cooperative control.The application has fast dynamic response speed, strong anti-interference ability and high steady-state control precision, and can meet the demand of high-precision MIG / MAG welding process.

Description

Technical Field

[0001] This invention relates to the field of inverter DC welding machine control technology, and more specifically to an inverter DC welding machine feedforward high-precision feedback control system and method for MIG / MAG welding processes. Background Technology

[0002] Currently, constant voltage control in inverter-type DC welding machines generally adopts a single closed-loop feedback control mode. The voltage feedback point is located at the welding machine output (i.e., between the welding torch and ground), and the voltage across the arc is directly collected as the feedback signal to achieve stable output voltage control. To suppress output current fluctuations, an output reactor is usually connected in series between the welding machine output and the rectifier module. However, in actual welding processes, various complex conditions exist, such as arc length variations, molten droplet spatter, and short-circuit transitions.

[0003] In existing technologies, some welding machines attempt to use simple feedback control, but an effective feedforward compensation mechanism has not yet been introduced. Furthermore, the feedback sampling stage is susceptible to factors such as the inductive back electromotive force of the output reactor, the distributed voltage drop of the welding cable, and electromagnetic interference under high current conditions, leading to feedback signal distortion, low sampling accuracy, and lag in control response. Especially during sudden changes in welding conditions, a single feedback control method cannot simultaneously meet the requirements of dynamic response speed and static control accuracy, easily resulting in problems such as adjustment overshoot, oscillation, and welding parameter drift, making it unsuitable for precision welding scenarios with high control performance requirements.

[0004] Therefore, there is an urgent need to propose a control system that can effectively overcome the above-mentioned defects. By optimizing the feedback sampling structure and introducing a feedforward compensation mechanism, the dynamic response capability, anti-interference performance and steady-state control accuracy of the system can be improved. Summary of the Invention

[0005] The purpose of this invention is to provide a high-precision feedback control system and method for inverter DC welding machines, in order to solve the problems of low feedback accuracy and delayed control response caused by the influence of output reactor, cable voltage drop and electromagnetic interference on feedback sampling in existing single closed-loop feedback control of inverter DC welding machines, and the lack of a feedforward compensation mechanism, thus failing to achieve high-precision and high-stability welding control.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A high-precision feedback control system for an inverter-type DC welding machine includes: The main power circuit includes a rectifier and filter module, an inverter module, an inverter transformer, a full-bridge rectifier module, an output reactor, and output terminals connected in sequence. The voltage sampling module has its sampling terminal located between the full-bridge rectifier module and the output reactor, and is used to collect the rectified DC voltage U.f As a voltage feedback signal; The current sampling module, with its sampling terminal located between the output reactor and the output terminal, is used to collect the welding current I. out As a current feedback signal; The feedforward compensation module receives the current feedback signal and calculates the feedforward compensation amount according to the preset compensation parameters. The deviation correction module receives voltage feedback signals, current feedback signals, and feedforward compensation amounts, and generates control signals based on the target welding parameters. The inverter drive module receives the control signal and drives the switching devices of the inverter module to operate.

[0007] A high-precision feedback control method for an inverter-type DC welding machine, employing the aforementioned high-precision feedback control system for an inverter-type DC welding machine, includes the following steps: S1, Set target voltage U ref The inductance value L of the output reactor and the DC resistance value R of the output reactor. L Equivalent resistance value R of welding cable cable ; S2, The rectified DC voltage U is acquired by the voltage sampling module. f As a voltage feedback signal, the welding current I is acquired by the current sampling module. out As a current feedback signal; S3. The feedforward compensation module receives the current feedback signal and outputs the inductance value L and DC resistance value R of the reactor according to the preset compensation parameters. L Equivalent resistance value R of welding cable cable Calculate the feedforward compensation amount U ff (t); S4, the deviation correction module receives the voltage feedback signal, current feedback signal, and feedforward compensation amount U. ff (t), and calculate the corrected control deviation based on the target voltage. Among them, U ref The target voltage; S5. The deviation correction module outputs a PWM duty cycle control signal to the inverter drive module based on the corrected control deviation, which drives the switching devices of the inverter module to operate and adjusts the output of the inverter module. S6. Repeat S2 to S5 to form a closed-loop control.

[0008] Compared with the prior art, the inverter-type DC welding machine feedforward high-precision feedback control system and method of the present invention have achieved the following significant technical effects: 1. This invention places the voltage sampling terminal between the full-bridge rectifier module and the output reactor, effectively avoiding interference from the inductive back electromotive force generated by the output reactor. Simultaneously, the voltage and current sampling modules incorporate isolated sampling circuits and anti-interference filtering circuits, suppressing electromagnetic interference under high-current conditions and ensuring a true and stable feedback signal. Actual testing shows that using this solution, the sampling error of the voltage feedback signal can be controlled within ±0.5%, which is approximately an order of magnitude higher than the traditional welding machine output sampling method (with errors typically ranging from ±3% to ±5%).

[0009] 2. This invention utilizes a dual mechanism of "feedforward compensation + high-precision feedback" to work collaboratively. The deviation correction module uses the corrected control deviation as input to the PID control algorithm, enabling precise control of the arc voltage. Under steady-state welding conditions, the welding voltage fluctuation range can be stabilized within ±0.5% of the target value.

[0010] 3. The feedforward compensation module of this invention pre-calculates the voltage drop of the output reactor and the voltage drop of the welding cable based on the real-time collected welding current and its rate of change, generating a feedforward compensation amount. This feedforward compensation amount is superimposed on the control signal before the deviation occurs, effectively offsetting the interference effects of the reactor, cable, and other components. Actual tests show that when the load changes abruptly, the control system of this invention can complete the adjustment and re-enter steady state within 5 to 10 ms, while the traditional single feedback control method usually requires 30 to 50 ms, improving the dynamic response speed by 3 to 6 times, and effectively avoiding overshoot and oscillation phenomena.

[0011] 4. The feedforward compensation module of this invention can predict and compensate for welding machine-specific interferences such as grid voltage fluctuations, arc length changes, and short-circuit transitions in real time. Combined with the isolation and filtering design of the high-precision sampling module, it forms a dual anti-interference guarantee. When sudden conditions such as spatter or short circuits occur during welding, the control system can quickly suppress parameter drift and maintain consistent welding quality. Extreme operating condition tests show that under grid voltage fluctuations of ±15%, the output voltage fluctuation of the system can still be controlled within ±1%, demonstrating excellent robustness.

[0012] 5. This invention does not require significant modifications to the main power circuit of existing inverter DC welding machines. It only optimizes the sampling topology and control algorithm, resulting in a simple structure, controllable cost, and ease of upgrading and modifying existing welding machine platforms.

[0013] In summary, this invention effectively solves the problems of low feedback accuracy, slow response, and weak anti-interference ability in the single closed-loop feedback control of existing inverter DC welding machines, significantly improving the control accuracy, dynamic response speed, and system stability of the welding process, and can meet the actual production needs of high-precision MIG / MAG welding processes. Attached Figure Description

[0014] Figure 1 This is a topology diagram of the feedforward high-precision feedback control system for an inverter-type DC welding machine according to an embodiment of the present invention. Figure 2 This is a flowchart of the high-precision feedback control method for the inverter-type DC welding machine according to an embodiment of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. Certain embodiments of the invention will be described more fully below with reference to the accompanying drawings, and some, but not all, of these embodiments will be shown. In fact, various embodiments of the invention can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to enable the invention to meet applicable legal requirements.

[0016] In the description of this invention, it should be noted that the terms "inner," "outer," "upper," "lower," "front," and "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0017] Example 1

[0018] In this embodiment of the invention, a high-precision feedback control system and method for an inverter-type DC welding machine are provided. Please refer to [link / reference]. Figure 1 , Figure 2 As shown.

[0019] A high-precision feedback control system for an inverter-type DC welding machine includes a main power circuit, a voltage sampling module, a current sampling module, a feedforward compensation module, a deviation correction module, and an inverter drive module.

[0020] The main power circuit includes a rectifier and filter module, an inverter module, an inverter transformer, a full-bridge rectifier module, an output reactor, and output terminals connected in sequence. The rectifier and filter module is connected to the mains frequency AC power, which is then inverted by the inverter module, transformed by the inverter transformer, and rectified by the full-bridge rectifier module. Finally, the power is output to the output terminals (welding torch and workpiece / load) through the output reactor, providing stable power for welding.

[0021] The sampling terminal of the voltage sampling module is located between the full-bridge rectifier module and the output reactor to avoid interference from the output reactor. The voltage sampling module is used to acquire the rectified DC voltage U.f As a voltage feedback signal, the sampling terminal of the current sampling module is located between the output reactor and the output terminal. The current sampling module is used to collect the welding current I. out As a current feedback signal.

[0022] The voltage sampling module and the current sampling module have built-in isolated sampling circuits and anti-interference filtering circuits, which can suppress electromagnetic interference under high current conditions, ensure that the feedback signal is true and stable, and improve sampling accuracy.

[0023] The feedforward compensation module receives the current feedback signal and calculates the feedforward compensation amount according to the preset compensation parameters.

[0024] The preset compensation parameters include the inductance value L of the output reactor and the DC resistance value R of the output reactor. L Equivalent resistance value R of welding cable cable .

[0025] Feedforward compensation ; Among them, K drop An adaptive droop coefficient; ; Among them, U L (t) represents the voltage drop across the output reactor; t represents time. ; Among them, U cable This is for the voltage drop of the welding cable.

[0026] The deviation correction module receives voltage feedback signals, current feedback signals, and feedforward compensation amounts, and generates control signals based on the target welding parameters.

[0027] The deviation correction module employs a PID control algorithm to correct the control deviation. As input, the output is the PWM duty cycle D(t) control signal; Among them, U ref The target voltage; ; in, It is a saturation constraint function; ; Among them, K p K i K d K is a constant in the PID control algorithm. p K is a proportionality constant. i K is the integration constant. d is a differential constant.

[0028] The inverter drive module is connected to the inverter module. The inverter drive module receives the control signal and drives the switching device (IGBT) of the inverter module to operate, adjusts the output of the inverter module, and realizes precise control of welding parameters.

[0029] A high-precision feedback control method for an inverter-type DC welding machine, employing the aforementioned high-precision feedback control system for an inverter-type DC welding machine, includes the following steps: S1, Set target voltage U ref The inductance value L of the output reactor and the DC resistance value R of the output reactor. L Equivalent resistance value R of welding cable cable and initialize the PID constant K p K i and K d .

[0030] S2, The rectified DC voltage U is acquired by the voltage sampling module. f As a voltage feedback signal, the welding current I is acquired by the current sampling module. out As a current feedback signal.

[0031] S3. The feedforward compensation module receives the current feedback signal and outputs the inductance value L and DC resistance value R of the reactor according to the preset compensation parameters. L Equivalent resistance value R of welding cable cable Calculate the feedforward compensation amount U ff (t).

[0032] Among them, feedforward compensation amount ; Among them, K drop An adaptive droop coefficient; ; Among them, U L (t) represents the voltage drop across the output reactor; t represents time. ; Among them, U cable This is for the voltage drop of the welding cable.

[0033] S4, the deviation correction module receives the voltage feedback signal, current feedback signal, and feedforward compensation amount U. ff (t), and calculate the corrected control deviation based on the target voltage. Among them, U ref The target voltage.

[0034] S5. The deviation correction module outputs a PWM duty cycle control signal to the inverter drive module based on the corrected control deviation, driving the switching devices of the inverter module to operate and adjusting the output of the inverter module.

[0035] Among them, the deviation correction module adopts the PID control algorithm, takes the corrected control deviation as input, and outputs the PWM duty cycle D(t) control signal; ; in, It is a saturation constraint function; ; Where Kp, Ki, and Kd are constants in the PID control algorithm, Kp is the proportional constant, Ki is the integral constant, and Kd is the derivative constant.

[0036] S6. Repeat S2 to S5 to form a closed-loop control, so that the welding voltage fluctuation range is stabilized within ±0.5% of the target value, and high-precision welding control is achieved.

[0037] Example 2 This embodiment 2 describes an electronic device including a memory and one or more processors. Executable code is stored in the memory. When the processor executes the executable code, it implements the steps of the feedforward high-precision feedback control method for the inverter-type DC welding machine as described in embodiment 1 above.

[0038] Example 3 This embodiment 3 describes a computer-readable storage medium storing a program that, when executed by a processor, is used to implement the steps of the feedforward high-precision feedback control method for an inverter-type DC welding machine as described in embodiment 1 above.

[0039] The computer-readable storage medium can be an internal storage unit of any device or apparatus with data processing capabilities, such as a hard disk or memory, or an external storage device of any device with data processing capabilities, such as a plug-in hard disk, smart media card (SMC), SD card, flash card, etc.

[0040] The present invention has been described in detail above with reference to the accompanying drawings. Based on the above description, those skilled in the art should have a clear understanding of the inverter-type DC welding machine feedforward high-precision feedback control system and method of the present invention. Of course, 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 descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-precision feedback control system for an inverter-type DC welding machine, characterized in that, include: The main power circuit includes a rectifier and filter module, an inverter module, an inverter transformer, a full-bridge rectifier module, an output reactor, and output terminals connected in sequence. The voltage sampling module has its sampling terminal located between the full-bridge rectifier module and the output reactor, and is used to collect the rectified DC voltage U. f As a voltage feedback signal; The current sampling module, with its sampling terminal located between the output reactor and the output terminal, is used to collect the welding current I. out As a current feedback signal; The feedforward compensation module receives the current feedback signal and calculates the feedforward compensation amount according to the preset compensation parameters. The deviation correction module receives voltage feedback signals, current feedback signals, and feedforward compensation amounts, and generates control signals based on the target welding parameters. The inverter drive module receives the control signal and drives the switching devices of the inverter module to operate.

2. The high-precision feedback control system for an inverter-type DC welding machine according to claim 1, characterized in that, The voltage sampling module and / or current sampling module have built-in isolated sampling circuits and anti-interference filtering circuits.

3. The high-precision feedback control system for an inverter-type DC welding machine according to claim 1, characterized in that, The preset compensation parameters include the inductance value L of the output reactor and the DC resistance value R of the output reactor. L Equivalent resistance value R of welding cable cable .

4. The high-precision feedback control system for an inverter-type DC welding machine according to claim 3, characterized in that, Feedforward compensation ; Among them, K drop An adaptive droop coefficient; ； Among them, U L (t) represents the voltage drop across the output reactor; t represents time. ； Among them, U cable This is for the voltage drop of the welding cable.

5. The high-precision feedback control system for an inverter-type DC welding machine according to claim 4, characterized in that, The deviation correction module uses a PID control algorithm to correct the control deviation. As input, the output is the PWM duty cycle D(t) control signal; Among them, U ref The target voltage; ； in, It is a saturation constraint function; ； Among them, K p K i K d K is a constant in the PID control algorithm. p K is a proportionality constant. i K is the integration constant. d is a differential constant.

6. A high-precision feedback control method for an inverter-type DC welding machine, employing the high-precision feedback control system for an inverter-type DC welding machine as described in any one of claims 1 to 5, characterized in that... The method includes the following steps: S1, Set target voltage U ref The inductance value L of the output reactor and the DC resistance value R of the output reactor. L Equivalent resistance value R of welding cable cable ; S2, The rectified DC voltage U is acquired by the voltage sampling module. f As a voltage feedback signal, the welding current I is acquired by the current sampling module. out As a current feedback signal; S3. The feedforward compensation module receives the current feedback signal and outputs the inductance value L and DC resistance value R of the reactor according to the preset compensation parameters. L Equivalent resistance value R of welding cable cable Calculate the feedforward compensation amount U ff (t); S4, the deviation correction module receives the voltage feedback signal, current feedback signal, and feedforward compensation amount U. ff (t), and calculate the corrected control deviation based on the target voltage. Among them, U ref The target voltage; S5. The deviation correction module outputs a PWM duty cycle control signal to the inverter drive module based on the corrected control deviation, which drives the switching devices of the inverter module to operate and adjusts the output of the inverter module. S6. Repeat S2 to S5 to form a closed-loop control.

7. The high-precision feedback control method for inverter-type DC welding machines according to claim 6, characterized in that, In S3, the feedforward compensation amount ; Among them, K drop An adaptive droop coefficient; ； Among them, U L (t) represents the voltage drop across the output reactor; t represents time. ； Among them, U cable This is for the voltage drop of the welding cable.

8. The high-precision feedback control method for inverter-type DC welding machines according to claim 6, characterized in that, In S5, the deviation correction module adopts the PID control algorithm, takes the corrected control deviation as input, and outputs the PWM duty cycle D(t) control signal. ； in, It is a saturation constraint function; ； Among them, K p K i K d K is a constant in the PID control algorithm. p K is a proportionality constant. i K is the integration constant. d is a differential constant.

9. An electronic device comprising a memory and one or more processors, wherein the memory stores executable code, characterized in that, When the processor executes the executable code, it implements the feedforward high-precision feedback control method for inverter DC welding machines as described in any one of claims 6 to 8.

10. A computer-readable storage medium having a program stored thereon, characterized in that, When the program is executed by the processor, it implements the feedforward high-precision feedback control method for inverter DC welding machines as described in any one of claims 6 to 8.

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