A control method of a dual-voltage inverter welder, and an inverter welder system

Abstract

The application discloses a control method and an inverter welding machine system of a dual-voltage inverter welding machine. In the initial stage of power-on, an AC power grid voltage is collected, and a three-phase line voltage signal is extracted; the three-phase line voltage signal is sent to a main control unit for algorithm determination, so that the current input system is identified as three-phase 220V or three-phase 380V, and a target control parameter set including at least a bus voltage stabilizing threshold, a PWM drive duty cycle reference and current closed-loop curve parameters is automatically matched and generated; the aforementioned parameters are used as control instructions to drive a silicon carbide power device to perform high-frequency inversion to output initial welding direct current; output end voltage and current are sampled in real time, and corresponding theoretical reference values are extracted from the closed-loop curve, and a dynamic deviation is calculated by comparison, so that the PWM drive duty cycle is closed-loop regulated. The application realizes full-automatic identification and debugging-free of dual voltage, deeply links voltage identification with silicon carbide high-frequency drive and digital closed-loop compensation, and can greatly improve welding constant current control precision and stability.

Description

Technical Field

[0001] This invention relates to the field of welding equipment control technology, specifically to a control method and system for a dual-voltage inverter welding machine. Background Technology

[0002] Inverter welding machines are core equipment in modern industrial manufacturing, construction, and equipment maintenance. Their performance and control precision directly affect welding quality and operational efficiency. In complex work sites such as industrial workshops and construction sites, due to differences in power supply conditions in different areas or facilities, there are usually two common power grid supply conditions: three-phase 220V and three-phase 380V.

[0003] Existing inverter welding machines typically rely on manual dialing or internal wiring modifications for speed switching to adapt to different power grid systems. This method is not only cumbersome in complex power supply environments but also highly susceptible to damage to the entire circuitry due to human error (such as incorrectly setting the speed to 220V under 380V power supply). Although some existing technologies have proposed automatic identification solutions, they often only involve simple hardware relay switching and fail to achieve deep digital linkage between voltage identification results and subsequent inverter drives. This makes it difficult to achieve true plug-and-play functionality without debugging, and improvements are needed. Summary of the Invention

[0004] In view of the above-mentioned shortcomings mentioned in the background art, the purpose of this invention is to provide a control method and an inverter welding machine system for a dual-voltage inverter welding machine.

[0005] This invention provides a control method for a dual-voltage inverter welding machine, comprising the following steps:

[0006] During the initial power-on phase, after processing by the filtering and rectification circuit, the input AC grid voltage is acquired in real time, and the three-phase line voltage signals are extracted.

[0007] The three-phase line voltage signal is sent to the main control unit for algorithm determination to identify whether the current input mode is three-phase 220V or three-phase 380V; based on the identified input mode, the target control parameter set is automatically matched and generated, including at least the bus voltage stabilization threshold, PWM drive duty cycle reference and current closed-loop curve parameters.

[0008] The bus voltage regulation threshold and the PWM drive duty cycle reference are used as control commands to drive the silicon carbide power device to perform high-frequency inversion. After the transformer step-down and secondary rectification and filtering, the initial welding DC power is output.

[0009] The output current and output voltage of the initial welding DC power are sampled in real time, and the corresponding theoretical reference value is analyzed and extracted from the current closed-loop curve parameters. The sampled output current and output voltage are compared with the theoretical reference value to calculate the dynamic deviation. Based on the dynamic deviation, the current PWM drive duty cycle is adjusted in a closed loop to achieve constant current control and parameter compensation in the welding process.

[0010] The present invention also provides an inverter welding machine system, the system comprising:

[0011] The input acquisition module is used to acquire the input AC grid voltage in real time during the initial power-on stage after processing by the filtering and rectification circuit, and extract the three-phase line voltage signal.

[0012] The main control identification and parameter generation module is used to send the three-phase line voltage signal into the main control unit for algorithm judgment, and identify whether the current input mode is three-phase 220V or three-phase 380V; based on the identified input mode, it automatically matches and generates a target control parameter set, which includes at least the bus voltage stabilization threshold, PWM drive duty cycle reference and current closed-loop curve parameters.

[0013] The inverter drive module is used to use the bus voltage regulation threshold and the PWM drive duty cycle reference as control commands to drive the silicon carbide power device to perform high-frequency inversion. After the transformer step-down and secondary rectification and filtering, the initial welding DC power is output.

[0014] The closed-loop control module is used to sample the output current and output voltage of the initial welding DC current in real time, and simultaneously analyze and extract the corresponding theoretical reference value from the current closed-loop curve parameters; compare the sampled output current and output voltage with the theoretical reference value to calculate the dynamic deviation, and adjust the current PWM drive duty cycle based on the dynamic deviation to achieve constant current control and parameter compensation in the welding process.

[0015] Compared with the existing technology, the present invention achieves fully automatic identification and debugging-free switching of three-phase 220V and three-phase 380V input modes by acquiring three-phase line voltage signals in real time during the initial power-on stage and making algorithm judgments by the main control unit. This avoids the cumbersome operation and risk of burn-out caused by manual dialing or changing jumper wires.

[0016] Meanwhile, based on the identification results, a target control parameter set including bus voltage regulation threshold, PWM drive duty cycle reference and current closed loop curve parameters is automatically matched and generated. The voltage identification results are deeply linked with the high-frequency inverter drive and digital closed loop compensation of silicon carbide power devices, giving full play to the advantages of high frequency and low loss of silicon carbide devices, which can effectively improve the overall efficiency and dynamic response speed.

[0017] Furthermore, by sampling the output current and voltage in real time and comparing them with the theoretical reference value to obtain the dynamic deviation, and then adjusting the PWM drive duty cycle in a closed loop, precise constant current control and parameter adaptive compensation in the welding process are achieved. This can significantly enhance the output stability and anti-interference ability of the welding machine under complex working conditions such as power grid fluctuations and load changes, ensuring smooth arc initiation, stable arc and weld formation quality. Attached Figure Description

[0018] Figure 1 This is a schematic flowchart of a control method for a dual-voltage inverter welding machine disclosed in an embodiment of the present invention;

[0019] Figure 2 This is a schematic diagram of the structure of an inverter welding machine system disclosed in an embodiment of the present invention. Detailed Implementation

[0020] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0021] It is understood that the control method for a dual-voltage inverter welding machine described in this embodiment can be deployed in high-frequency inverter welding machine systems employing DSP main control units and silicon carbide (SiC) power devices. This method is particularly suitable for complex power supply environments where three-phase 220V and three-phase 380V are mixed, the power grid fluctuates significantly, and long-term continuous operation is required, such as steel structure workshops, equipment maintenance sites, and field construction sites.

[0022] Reference Figure 1 As shown in the figure, an embodiment of the present invention provides a control method for a dual-voltage inverter welding machine, the method comprising the following steps:

[0023] S1, during the initial power-on phase, after processing by the filtering and rectification circuit, the input AC grid voltage is acquired in real time, and the three-phase line voltage signal is extracted.

[0024] In this embodiment, after the welding machine is connected to a three-phase three-wire power supply, there is no need to manually distinguish the phase sequence or manually set the voltage level; it can be powered on directly. The input AC grid voltage is first processed by EMI filtering and rectification circuits to filter out high-frequency interference signals in the grid and ensure the purity of the sampled signal. At a specific node in the rectification stage, the current AC grid voltage is acquired in real time through a high-precision voltage sampling circuit, and the three-phase line voltage signals that can characterize the grid characteristics are extracted from it.

[0025] S2, the three-phase line voltage signal is sent to the main control unit for algorithm judgment, and the current input mode is identified as three-phase 220V or three-phase 380V; based on the identified input mode, the target control parameter set is automatically matched and generated, including at least the bus voltage stabilization threshold, PWM drive duty cycle reference and current closed-loop curve parameters.

[0026] In this embodiment, after receiving the three-phase line voltage signal, the main control unit (e.g., a fully digital DSP chip) performs intelligent judgment through a built-in algorithm. This step can automatically complete the voltage system identification throughout the entire process and deeply digitally link the identification result with the inverter drive parameters of the subsequent stage, thereby avoiding the cumbersome operation, low efficiency, and risk of equipment damage due to misoperation caused by relying on manual dialing or jumper rewiring in traditional solutions.

[0027] Specifically, the main control unit first performs algorithmic analysis on the input signal to distinguish whether the current power supply is three-phase 220V or three-phase 380V. After determining the input standard, it actively retrieves and generates a set of target control parameters that perfectly match the standard from its internally stored control parameter library. This set of parameters includes at least: a bus voltage regulation threshold for stabilizing the DC bus voltage, a PWM drive duty cycle reference for determining the initial switching behavior of the power devices, and current closed-loop curve parameters to guide subsequent constant current control characteristics.

[0028] It should be understood that through the above-mentioned multi-dimensional parameter linkage, it can be ensured that the welding machine can automatically adapt to the optimal working reference regardless of the input voltage.

[0029] As an example, identifying whether the current input standard is three-phase 220V or three-phase 380V includes:

[0030] S21, the three-phase line voltage signal is filtered and envelope extracted to calculate the effective voltage feature value, and the effective voltage feature value is compared with the preset three-phase 220V voltage threshold range and the three-phase 380V voltage threshold range respectively.

[0031] In practice, industrial sites often involve the start-up and shutdown of high-power equipment, causing instantaneous distortion or large fluctuations in grid voltage. Directly using the raw sampled values ​​for judgment can easily lead to malfunctions. Therefore, the main control unit first performs digital filtering on the extracted three-phase line voltage signals to remove high-frequency noise and spike interference. Based on this, envelope extraction is further performed to obtain a smooth signal that truly reflects the effective value of the grid fundamental wave, i.e., the effective voltage characteristic value.

[0032] Next, the effective voltage characteristic value is compared with two pre-stored voltage threshold ranges: one is a threshold range set for a three-phase 220V system (e.g., 190V-240V), and the other is a threshold range set for a three-phase 380V system (e.g., 350V-400V). By using this range comparison method instead of a single-point comparison, the tolerance to normal fluctuations in the power grid can be effectively improved.

[0033] S22, if the effective voltage characteristic value continues to fall stably within a certain voltage threshold range within a consecutive preset number of sampling periods, then the current input format result is determined and output.

[0034] In practice, to avoid misjudgments caused by voltage transients (such as voltage drops caused by the startup of high-power equipment in the same power grid), a time window stability verification mechanism was further designed.

[0035] Specifically, the main control unit tracks the comparison results of multiple consecutive sampling cycles. For example, a judgment window can be set for 20 consecutive sampling cycles. Only when the effective voltage characteristic value calculated in each of these 20 consecutive sampling cycles consistently and stably falls within the same voltage threshold range (e.g., always within the 220V range) is the input system finally confirmed as three-phase 220V, and the corresponding judgment result is output. If, during this period, the effective voltage characteristic value jumps out of the range or falls into another range, the counter is reset to zero and accumulation restarts.

[0036] It should be understood that the above mechanism can significantly improve the anti-interference capability and identification reliability of equipment in complex power grid environments, and avoid frequent misjudgments or incorrect parameter switching caused by short-term voltage fluctuations.

[0037] As an example, a set of target control parameters is automatically matched and generated based on the identified input format, including:

[0038] S23, based on the identified input mode, perform correlation matching in the control parameter library, extract the corresponding bus voltage regulation threshold, PWM drive duty cycle reference, and current closed-loop curve parameters, and combine them to generate the target control parameter set; wherein, the control parameter library contains multiple power grid input modes and corresponding reference parameters.

[0039] In practice, the main control unit has a pre-built structured control parameter library. This library uses the power grid input standard (e.g., three-phase 220V or three-phase 380V) as a unique index and stores a complete set of corresponding control reference parameters that have been calibrated offline or experimentally verified. Once the current output input standard (e.g., three-phase 220V) is determined, this standard is used as an addressing feature to directly perform association matching in the parameter library.

[0040] It should be understood that the parameters extracted through matching are a complete set of parameters including front-end voltage regulation, mid-end drive, and end-end feedback. Among them, the bus voltage regulation threshold is used to set the desired stable point of the DC bus voltage, with a lower threshold (e.g., 310V) set for 220V input and a higher threshold (e.g., 540V) set for 380V input; the PWM drive duty cycle reference is used to determine the duty cycle of the initial pulse width modulation signal in the inverter stage to ensure appropriate power output under different input voltages; the current closed-loop curve parameters include the proportional, integral, and derivative coefficients of the PID controller, as well as the current response characteristic curves for different welding modes.

[0041] The extracted parameters are combined and encapsulated into a structured set of target control parameters.

[0042] S3, using the bus voltage regulation threshold and the PWM drive duty cycle reference as control commands, drive the silicon carbide power device to perform high-frequency inversion, and output the initial welding DC power after transformer step-down and secondary rectification and filtering.

[0043] In this embodiment, the bus voltage regulation threshold and PWM drive duty cycle reference in the aforementioned generated target control parameter set are used as core control commands to drive the subsequent power inverter stage. To achieve efficient and low-loss power conversion, this embodiment uses silicon carbide (SiC) MOSFETs, a third-generation semiconductor material, as the core inverter switching device. Compared to traditional silicon-based IGBTs or MOSFETs, silicon carbide devices have significant advantages such as fast switching speed, low switching loss, and high temperature resistance, enabling the welding machine to operate at higher inverter frequencies (e.g., 50kHz to 100kHz), thereby significantly reducing the size and weight of the main transformer, improving the overall power density and dynamic response speed, and significantly reducing the temperature rise during long-term full-load operation.

[0044] Specifically, the main control unit generates corresponding drive pulses according to the aforementioned control commands, controlling the silicon carbide power devices to alternately turn on and off, inverting the unstable DC power after the pre-stage rectification and filtering into high-frequency AC power. This high-frequency AC power is then fed into an intermediate frequency step-down transformer to reduce the voltage to a suitable amplitude for welding. Finally, after secondary rectification and filtering, a smooth and stable initial welding DC power is output.

[0045] As an example, using the bus voltage regulation threshold and the PWM drive duty cycle reference as control commands to drive silicon carbide power devices to perform high-frequency inversion includes:

[0046] S31, Real-time acquisition of the actual DC bus voltage at the inverter front end, comparison and calculation with the bus voltage regulation threshold to output duty cycle correction amount; Real-time modulation of the PWM drive duty cycle reference using the duty cycle correction amount to generate target high-frequency drive pulse sequence;

[0047] In practice, a high-precision voltage sampling circuit is used to acquire the actual voltage value across the DC bus after the pre-stage rectification and filtering in real time. The comparator inside the main control unit calculates the difference between this measured value and the previously matched bus voltage regulation threshold to obtain the voltage deviation.

[0048] The DSP core runs a pre-defined PID (Proportional-Integral-Derivative) control algorithm, using the voltage deviation as input to calculate the duty cycle correction amount for adjusting the power output. It should be understood that this duty cycle correction amount reflects the degree of deviation of the current actual bus voltage from the target threshold and the direction of correction. For example, when the measured bus voltage falls below the threshold due to grid fluctuations, the PID algorithm calculates a positive duty cycle correction amount.

[0049] For example, let voltage deviation be... ,in The bus voltage stabilization threshold. This is the actual DC bus voltage sampled in real time. The duty cycle correction amount is... The calculation formula is:

[0050]

[0051] in: The duty cycle correction amount for the current output (dimensionless, usually expressed as a percentage or normalized value); This is a proportionality coefficient used to linearly amplify the current deviation, determining the speed of the response; The integral coefficient is used to eliminate static error, and steady-state error-free regulation is achieved by accumulating and integrating the historical deviations. The differential coefficient is used to predict the trend of deviation changes, playing a proactive adjustment role and suppressing oscillations.

[0052] In digital DSP implementations, the above continuous formulas need to be discretized. Let the sampling period be... , No. The deviation at each sampling time is The formula for calculating discrete PID is:

[0053]

[0054] The above This is the duty cycle correction amount, used to modulate the PWM drive duty cycle reference in real time to generate the target high-frequency drive pulse sequence.

[0055] The aforementioned duty cycle correction is superimposed and modulated in real time with the original PWM drive duty cycle reference to dynamically generate a corrected target high-frequency drive pulse sequence capable of resisting grid fluctuations. It should be understood that this processing ensures that the inverter stage always operates under the desired voltage conditions.

[0056] S32, the target high-frequency drive pulse sequence is output to the drive terminal of the silicon carbide power device to control the silicon carbide power device to perform high-frequency switching action to complete the high-frequency inverter conversion of electrical energy.

[0057] In practice, the generated target high-frequency drive pulse sequence is sent to the drive circuit of the silicon carbide power device. The drive circuit performs level conversion and power amplification on the pulse sequence to give it sufficient driving capability, and then applies it directly between the gate and source of the silicon carbide MOSFET. During the high level of the pulse sequence, the silicon carbide device is turned on; during the low level, the device is turned off. Through this high-frequency switching action, the DC power input from the rectifier circuit is chopped into a series of high-frequency voltage pulses, which, after passing through subsequent transformers and rectifier filter circuits, complete the DC-to-high-frequency AC inverter conversion process.

[0058] It should be understood that, thanks to the high switching speed of silicon carbide devices, the above conversion process has extremely low switching losses and very high conversion efficiency.

[0059] S4. The output current and output voltage of the initial welding DC power are sampled in real time, and the corresponding theoretical reference value is extracted from the current closed-loop curve parameters. The sampled output current and output voltage are compared with the theoretical reference value to obtain the dynamic deviation. Based on the dynamic deviation, the current PWM drive duty cycle is adjusted in a closed loop to achieve constant current control and parameter compensation in the welding process.

[0060] In this embodiment, relying on the powerful computing power and high-speed sampling capability of the all-digital DSP, the present invention constructs a dual closed-loop control logic for output current and output voltage. Specifically, the welding machine output end acquires the instantaneous output current and output voltage values ​​of the initial welding DC current in real time through a high-precision current sensor (such as a Hall effect current sensor) and a voltage sampling circuit. At the same time, the main control unit extracts the current closed-loop curve parameters from the generated target control parameter set, and, combined with the current working state (such as the user-set target current value, the current welding mode, etc.), parses the theoretical reference value (including theoretical reference current and theoretical reference voltage) that the system should theoretically output at the current sampling moment from these parameters.

[0061] Next, the actual sampled output current and output voltage are compared with the corresponding theoretical reference values ​​cycle by cycle to calculate the dynamic deviation. This dynamic deviation comprehensively reflects the instantaneous deviation between the actual welding arc state and the ideal state. Based on this dynamic deviation, the main control unit dynamically adjusts the PWM drive duty cycle of the current output through a built-in digital PID (proportional-integral-derivative) compensation algorithm or other control algorithms, thus forming a closed-loop real-time feedback control system. This closed-loop adjustment mechanism can effectively suppress output drift caused by factors such as changes in the distance between the welding electrode and the workpiece, droplet transfer, power grid fluctuations, and sudden load changes, ensuring that the welding current maintains a high-precision constant current output under various harsh working conditions, ultimately achieving a stable welding process and good weld formation quality.

[0062] As an example, the corresponding theoretical reference value is analyzed and extracted from the parameters of the current closed-loop curve, including:

[0063] S41, obtain the current welding mode instruction, parse the rated operating curve and compensation coefficient corresponding to the current mode from the current closed-loop curve parameters according to the welding mode instruction, and extract the theoretical reference value corresponding to the current sampling time based on the rated operating curve and the compensation coefficient; wherein, the welding mode instruction includes manual arc welding, argon arc welding or carbon arc gouging mode.

[0064] In practice, different welding processes have drastically different requirements for arc characteristics, so the differences in working conditions must be fully considered when extracting theoretical reference values. For example, manual arc welding (SMAW) requires a strong thrust current to prevent the electrode from sticking to the workpiece and requires additional energy impact during arc ignition; argon arc welding (TIG) requires a gentle arc ignition, a soft current, and a dynamic response that is not too violent; while carbon arc gouging requires a large current output capability and an extremely fast current rise rate.

[0065] Therefore, the main control unit reads the current welding mode command set by the user through the operation panel or external interface, and uses the command as an index to parse the rated operating curve (i.e. the preset trajectory of the output current and output voltage changing with the load or with time under ideal conditions) that is completely matched with the generated current closed-loop curve parameter package, as well as a series of compensation coefficients (such as thrust current intensity coefficient, thermal arc ignition energy coefficient, current slow rise / slow fall time coefficient, etc.).

[0066] Furthermore, by combining the user-set welding current value at the current sampling moment, the corresponding theoretical reference value is extracted from the rated operating curve for that moment. This reference value is then calculated with the compensation coefficient (e.g., by multiplication or weighted summation) to obtain the theoretical reference value for the actual expected output at the current sampling moment, including the theoretical reference voltage and theoretical reference current values. For example, in manual arc welding mode, when the system determines that it is in the arc ignition stage, the thermal arc ignition compensation coefficient is greater than 1, making the theoretical reference current value significantly higher than the rated curve value corresponding to the user-set value at the moment of arc ignition. After the arc ignition is completed and steady-state welding begins, the compensation coefficient returns to 1. In this way, the extracted theoretical reference value is a comprehensive reference standard that integrates rated operating characteristics and dynamic compensation requirements, ensuring that subsequent deviation calculations and closed-loop adjustment strategies always maintain a high degree of consistency with the arc physics requirements of the current welding mode.

[0067] After obtaining the real-time sampled output current and voltage, as well as the theoretical reference current and voltage extracted from the current closed-loop curve parameters, the main control unit performs cycle-by-cycle difference comparison on the current and voltage. Specifically, the dynamic deviation includes two independent components: current deviation, which is the theoretical reference current minus the actual output current; and voltage deviation, which is the theoretical reference voltage minus the actual output voltage. These two components reflect the instantaneous deviation of the output current and output voltage from the theoretical reference values, respectively.

[0068] If the current deviation is positive, it indicates that the actual current is less than the theoretical requirement, and the output power needs to be increased; if it is negative, it indicates that the actual current exceeds the theoretical requirement, and the output power needs to be reduced. The voltage deviation is used to help determine the arc state. For example, when an arc is ignited and short-circuited, the output voltage drops sharply, resulting in a large positive deviation in the voltage deviation. Based on this, the short-circuit state can be identified and the corresponding compensation logic can be triggered.

[0069] As an example, adjusting the current PWM drive duty cycle based on the dynamic deviation in a closed loop specifically includes:

[0070] S42, when the dynamic deviation indicates that the output voltage is lower than the preset arc ignition threshold or the output current undergoes a sudden change within a preset range, a thrust current compensation command or a thermal arc ignition compensation command is generated.

[0071] In practice, different types of compensation instructions are intelligently generated based on the different characteristics of the dynamic deviation to adapt to the arc requirements at different stages of the welding process.

[0072] The thermal arc ignition compensation command is primarily triggered during the arc ignition stage. At the moment of arc ignition, the welding electrode and the workpiece are directly short-circuited, causing the output voltage to drop sharply from the open-circuit voltage (approximately 65V-75V) to near zero. When the main control unit detects that the output voltage is lower than the preset arc ignition threshold (e.g., 15V), it determines that the welding machine is in a short-circuit arc ignition state and generates a thermal arc ignition compensation command. This command temporarily boosts the output energy at the moment of arc ignition, providing a strong current surge to help the welding electrode quickly melt the workpiece surface and establish a stable arc, thereby effectively preventing electrode sticking or arc ignition failure due to insufficient arc ignition energy.

[0073] The thrust current compensation command is primarily triggered during welding when there is a sudden change in arc length. During normal welding, if the arc length suddenly lengthens due to electrode vibration, workpiece unevenness, or hand instability, the output current will experience a momentary drop. When the main control unit detects a sudden drop in output current exceeding a preset range (e.g., a current drop exceeding a set amplitude within a very short time), it determines that the arc is in an unstable state and generates a thrust current compensation command. This command automatically replenishes additional energy when the current drops, dynamically maintaining arc rigidity, preventing arc breakage, and ensuring smooth droplet transition while reducing spatter.

[0074] By making the above distinctions, the appropriate compensation strategy can be intelligently selected according to different working conditions (arc initiation stage or welding process) to achieve refined arc control.

[0075] S43, based on the thrust current compensation command or the thermal arc compensation command, calculate the compensation duty cycle and superimpose it on the current PWM drive duty cycle in real time for linear dynamic adjustment.

[0076] In practice, after generating any of the above compensation commands, the main control unit further quantifies and calculates the compensation duty cycle. Since thermal arc ignition compensation and thrust current compensation differ fundamentally in their action time and control objectives, different calculation strategies are employed, as detailed below.

[0077] For thermal arc ignition compensation commands, the action time is extremely short, mainly providing a one-time energy surge at the moment of arc ignition. This is based on the output voltage deviation. and the preset thermal arc ignition energy coefficient Combined with reference voltage (For example, take the rated open-circuit voltage of 70V) and normalize it to calculate the initial compensation duty cycle:

[0078]

[0079] in, The theoretical reference voltage, This is the actual output voltage. This is the output voltage deviation (during arcing and short circuit). Therefore ); This represents the thermal arc ignition energy coefficient, with a value ranging from 0 to 0.5. To provide sufficient arc ignition energy while avoiding arc energy overshoot that could damage the workpiece, an extremely short decay time window is set. (For example, 50 milliseconds), within this window, the compensated duty cycle is linearly decayed to zero over time:

[0080]

[0081] Thus, a strong arc-initiating energy can be obtained at the moment of arc initiation, and then it quickly returns to the normal level.

[0082] The thrust current compensation command differs from the hot arc ignition command; it is a continuous dynamic compensation during the welding process, used to address current drops caused by arc elongation, electrode vibration, etc. It is based on the current deviation. and the preset thrust current intensity coefficient The duty cycle is dynamically compensated in real time, and compensation is only performed when the actual current is insufficient.

[0083]

[0084] in, The theoretical reference current, This refers to the actual output current. is the thrust current intensity coefficient, dimensionless, with a value range of (0, 0.3); This is the rated maximum output current of the welding machine (e.g., 630A). The compensation duty cycle increases linearly with the increase of current deviation, and no compensation is generated when the actual current is higher than the theoretical reference, thus avoiding further increase in output during overcurrent.

[0085] After calculating the thermal arc compensation duty cycle and the thrust current compensation duty cycle separately, the two are injected into the existing PWM drive duty cycle in a linear superposition manner, and then limited:

[0086]

[0087] in, This provides the base duty cycle for the current closed-loop regulation. Indicates will Limited to Within the range, ensure that the output duty cycle does not exceed the physical range of 0 to 1.

[0088] Through the above instantaneous and stepless adjustment, precise compensation of the inverter output power can be achieved, ensuring smooth arc initiation, stable arc, and a smooth welding process.

[0089] As an example, the method further includes:

[0090] During inverter operation, the voltage distortion rate and voltage fluctuation amplitude of the three-phase line voltage signal are monitored in real time. When it is determined that the voltage fluctuation amplitude is within the preset range of the rated voltage, the corresponding distortion compensation coefficient is generated in combination with the voltage distortion rate.

[0091] The bus compensation bias is dynamically calculated based on the voltage fluctuation amplitude and the distortion compensation coefficient, and the bus voltage regulation threshold is corrected in real time using the bus compensation bias to maintain the stability of the output current.

[0092] In practice, after the welding machine enters normal inverter operation, the power grid does not always maintain an ideal sinusoidal waveform. Especially in industrial sites, when nonlinear loads such as high-power frequency converters, welding machines, and cranes are connected to the same grid, the three-phase voltage waveform will be distorted, accompanied by random fluctuations in amplitude.

[0093] To further improve the output stability of the welding machine under harsh power grid conditions, this embodiment, based on the aforementioned closed-loop control, further designs a dynamic correction mechanism for the bus threshold based on power grid quality feedforward. The main control unit continuously performs harmonic analysis on the extracted three-phase line voltage signals to calculate the voltage distortion rate (i.e., total harmonic distortion, THD). Simultaneously, it also monitors the voltage fluctuation amplitude in real time, i.e., the range of the effective voltage value fluctuating around the rated value.

[0094] When the voltage fluctuation is determined to be within the preset range of the equipment's rated voltage (e.g., within ±15% of the rated voltage), it is considered that the power grid is not severe enough to require shutdown protection, but compensation intervention is necessary. At this time, the main control unit, based on the calculated voltage distortion rate, looks up and matches the distortion compensation coefficient table pre-stored in the control parameter library to generate the corresponding distortion compensation coefficient. This distortion compensation coefficient reflects the extent to which the bus voltage regulation threshold needs to be adjusted to maintain a constant output current under the current distortion level.

[0095] The distortion compensation coefficient is fused with the current voltage fluctuation amplitude (e.g., multiplied or weighted summation) to dynamically generate the bus compensation bias. This bus compensation bias is then used to adjust the bus voltage regulation threshold in real time. For example, when grid distortion is severe, appropriately relaxing the control dead zone of the bus voltage regulation threshold or adjusting its target value can prevent the inverter from frequently triggering protection or causing output current fluctuations due to instantaneous peaks or dips in bus voltage.

[0096] Through the aforementioned feedforward compensation mechanism, the welding machine, based on its adaptability to a wide power grid, can further enhance its ability to suppress latent interferences such as waveform distortion, ensuring the stability and constancy of the output current under complex power supply environments.

[0097] As an example, the method further includes:

[0098] The system collects the phase sequence status of the power grid, the operating current of the inverter circuit, and the operating temperature of the silicon carbide power devices in real time; it determines whether the preset abnormal triggering conditions are met, and generates a corresponding fault prompt code when any of the abnormal triggering conditions are met; wherein, the abnormal triggering conditions include phase loss, phase imbalance, overvoltage, undervoltage, overcurrent, and overheating.

[0099] In practice, to achieve comprehensive equipment safety protection, a real-time monitoring and diagnostic task, independent of the constant current control loop, is run in parallel during the welding process. This is achieved through a dedicated detection circuit that continuously collects the following key parameters:

[0100] 1) The phase sequence status and three-phase voltage amplitude information of the power grid are used to determine whether there is a phase loss (a phase voltage is missing), phase imbalance (the difference in the three-phase voltage amplitude exceeds a set ratio, such as 20%), overvoltage (any phase voltage exceeds the upper limit threshold, such as 450V) or undervoltage (any phase voltage is lower than the lower limit threshold, such as 300V).

[0101] 2) The operating current of the inverter circuit is usually obtained through the current sensor on the DC bus side or the transformer primary current sampling circuit, which is used to determine whether an overcurrent has occurred (the instantaneous or effective value of the current exceeds the maximum withstand current of the silicon carbide power device or the transformer).

[0102] 3) The operating temperature of silicon carbide power devices is obtained by installing a negative temperature coefficient thermistor (NTC) or thermocouple near the heat sink of the power module or chip. This is used to determine whether overheating has occurred (the temperature exceeds the maximum allowable junction temperature of the silicon carbide device, such as 125°C).

[0103] The main control unit compares each of the real-time acquired signals with its corresponding preset safety threshold. If any signal meets its corresponding abnormal trigger condition—for example, if the voltage of any phase is detected to be below the undervoltage threshold, or the temperature of the silicon carbide device exceeds a set value—a fault is immediately determined, and a unique fault code is generated based on the fault type. For example, E-001 represents phase loss, E-002 represents overvoltage, E-003 represents undervoltage, E-004 represents overcurrent, E-005 represents overheating, and E-006 represents phase imbalance, etc.

[0104] As an example, the method further includes:

[0105] After generating the fault indication code, a protection interruption command is generated; based on the protection interruption command, the control commands sent to the silicon carbide power device are immediately blocked to perform a shutdown and locking action, and the fault indication code is output to the interactive panel for display.

[0106] In practice, once any abnormal triggering condition is met and a corresponding fault indication code is generated, the system enters the highest-priority fault protection mode. The main control unit (DSP) generates a non-maskable protection interrupt instruction. This instruction has the highest execution priority and can immediately interrupt the ongoing constant current closed-loop control algorithm and other routine tasks.

[0107] Upon responding to this interrupt command, all control signals sent to the drive terminals of the silicon carbide power devices are blocked. Specifically, this involves forcibly pulling the output of the PWM waveform generator low to an invalid level and clearing the output enable bit of the control register, ensuring that the drive circuit no longer provides any switching pulses to the gate of the silicon carbide MOSFET. It should be understood that this action allows the inverter circuit to completely stop operating within microseconds, achieving a hardware-level safety lockout for immediate shutdown in case of a fault, thereby maximizing the protection of the silicon carbide power devices, transformers, and other circuits from further damage due to overvoltage, overcurrent, or overheating.

[0108] While blocking the drive signal, the corresponding fault code (e.g., via a digital tube, LCD display, or LED indicator array) is output in real time to the welding machine's interactive panel for display. Simultaneously, the locked state must remain until the user manually disconnects the power and troubleshoots the fault, or until power is restored via a specific reset command.

[0109] The aforementioned protection mechanism, which integrates detection, locking, and display, not only effectively extends the service life of the entire machine but also provides on-site maintenance personnel with intuitive diagnostic information, thereby significantly improving the maintainability of the equipment and the efficiency of on-site fault handling.

[0110] Reference Figure 2 As shown, this embodiment of the invention also provides an inverter welding machine system 100, the system comprising:

[0111] The input acquisition module 101 is used to acquire the input AC grid voltage in real time during the initial power-on stage after processing by the filtering and rectification circuit, and extract the three-phase line voltage signal.

[0112] The main control identification and parameter generation module 102 is used to send the three-phase line voltage signal into the main control unit for algorithm judgment, identify whether the current input mode is three-phase 220V or three-phase 380V; and automatically match and generate a target control parameter set based on the identified input mode, including at least the bus voltage stabilization threshold, PWM drive duty cycle reference and current closed-loop curve parameters.

[0113] The inverter drive module 103 is used to use the bus voltage regulation threshold and the PWM drive duty cycle reference as control commands to drive the silicon carbide power device to perform high-frequency inversion. After the transformer step-down and secondary rectification and filtering, the initial welding DC power is output.

[0114] The closed-loop adjustment module 104 is used to sample the output current and output voltage of the initial welding DC current in real time, and simultaneously analyze and extract the corresponding theoretical reference value from the current closed-loop curve parameters; compare the sampled output current and output voltage with the theoretical reference value to calculate the dynamic deviation, and adjust the current PWM drive duty cycle based on the dynamic deviation to achieve constant current control and parameter compensation in the welding process.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to the above embodiments without departing from the principles and spirit of the present invention, and all such changes, modifications, substitutions, and variations fall within the protection scope of the present invention.

Claims

1. A control method for a dual-voltage inverter welding machine, characterized in that, Includes the following steps: During the initial power-on phase, after processing by the filtering and rectification circuit, the input AC grid voltage is acquired in real time, and the three-phase line voltage signals are extracted. The three-phase line voltage signal is sent to the main control unit for algorithm determination to identify whether the current input mode is three-phase 220V or three-phase 380V; based on the identified input mode, the target control parameter set is automatically matched and generated, including at least the bus voltage stabilization threshold, PWM drive duty cycle reference and current closed-loop curve parameters. The bus voltage regulation threshold and the PWM drive duty cycle reference are used as control commands to drive the silicon carbide power device to perform high-frequency inversion. After the transformer step-down and secondary rectification and filtering, the initial welding DC power is output. The output current and output voltage of the initial welding DC power are sampled in real time, and the corresponding theoretical reference value is analyzed and extracted from the parameters of the current closed-loop curve. The sampled output current and output voltage are compared with the theoretical reference value to calculate the dynamic deviation. Based on the dynamic deviation, the current PWM drive duty cycle is adjusted in a closed loop to achieve constant current control and parameter compensation in the welding process.

2. The control method for a dual-voltage inverter welding machine according to claim 1, characterized in that: Identify whether the current input standard is three-phase 220V or three-phase 380V, including: The three-phase line voltage signal is filtered and envelope extracted to calculate the effective voltage feature value. The effective voltage feature value is then compared with the preset three-phase 220V voltage threshold range and the three-phase 380V voltage threshold range, respectively. If the effective voltage characteristic value consistently and stably falls within a certain voltage threshold range within a preset number of sampling periods, then the current input format result is determined and output.

3. The control method for a dual-voltage inverter welding machine according to claim 2, characterized in that: Based on the identified input format, a set of target control parameters is automatically matched and generated, including: Based on the identified input mode, the system performs correlation matching in the control parameter library, extracts the corresponding bus voltage regulation threshold, PWM drive duty cycle reference, and current closed-loop curve parameters, and combines them to generate the target control parameter set; wherein, the control parameter library contains multiple power grid input modes and corresponding reference parameters.

4. The control method for a dual-voltage inverter welding machine according to claim 1, characterized in that: Using the bus voltage regulation threshold and the PWM drive duty cycle reference as control commands, the silicon carbide power device is driven to perform high-frequency inversion, including: The actual DC bus voltage at the inverter front end is acquired in real time and compared with the bus voltage regulation threshold to calculate and output the duty cycle correction amount; the duty cycle correction amount is used to modulate the PWM drive duty cycle reference in real time to generate the target high-frequency drive pulse sequence. The target high-frequency drive pulse sequence is output to the drive terminal of the silicon carbide power device to control the silicon carbide power device to perform high-frequency switching action, so as to complete the high-frequency inverter conversion of electrical energy.

5. The control method for a dual-voltage inverter welding machine according to claim 1, characterized in that: The corresponding theoretical reference values ​​are analyzed and extracted from the current closed-loop curve parameters, including: The current welding mode instruction is obtained, and the rated operating curve and compensation coefficient corresponding to the current mode are parsed from the current closed-loop curve parameters according to the welding mode instruction. The theoretical reference value corresponding to the current sampling time is extracted based on the rated operating curve and the compensation coefficient. The welding mode instruction includes manual arc welding, argon arc welding or carbon arc gouging mode.

6. The control method for a dual-voltage inverter welding machine according to claim 5, characterized in that: Based on the dynamic deviation, the current PWM drive duty cycle is adjusted in a closed loop, specifically including: When the dynamic deviation indicates that the output voltage is lower than the preset arc ignition threshold or the output current undergoes a sudden change within a preset range, a thrust current compensation command or a thermal arc ignition compensation command is generated. Based on the thrust current compensation command or the thermal arc ignition compensation command, the compensation duty cycle is calculated and superimposed on the current PWM drive duty cycle in real time for linear dynamic adjustment.

7. The control method for a dual-voltage inverter welding machine according to claim 1, characterized in that: The method further includes: During inverter operation, the voltage distortion rate and voltage fluctuation amplitude of the three-phase line voltage signal are monitored in real time. When it is determined that the voltage fluctuation amplitude is within the preset range of the rated voltage, the corresponding distortion compensation coefficient is generated in combination with the voltage distortion rate. The bus compensation bias is dynamically calculated based on the voltage fluctuation amplitude and the distortion compensation coefficient, and the bus voltage regulation threshold is corrected in real time using the bus compensation bias to maintain the stability of the output current.

8. The control method for a dual-voltage inverter welding machine according to claim 1, characterized in that: The method further includes: The system collects the phase sequence status of the power grid, the operating current of the inverter circuit, and the operating temperature of the silicon carbide power devices in real time; it determines whether the preset abnormal triggering conditions are met, and generates a corresponding fault prompt code when any of the abnormal triggering conditions are met; wherein, the abnormal triggering conditions include phase loss, phase imbalance, overvoltage, undervoltage, overcurrent, and overheating.

9. The control method for a dual-voltage inverter welding machine according to claim 8, characterized in that: The method further includes: After generating the fault indication code, a protection interruption command is generated; based on the protection interruption command, the control commands sent to the silicon carbide power device are immediately blocked to perform a shutdown and locking action, and the fault indication code is output to the interactive panel for display.

10. An inverter welding machine system, characterized in that, The system includes: The input acquisition module is used to acquire the input AC grid voltage in real time during the initial power-on stage after processing by the filtering and rectification circuit, and extract the three-phase line voltage signal. The main control identification and parameter generation module is used to send the three-phase line voltage signal into the main control unit for algorithm judgment, and identify whether the current input mode is three-phase 220V or three-phase 380V; based on the identified input mode, it automatically matches and generates a target control parameter set, which includes at least the bus voltage stabilization threshold, PWM drive duty cycle reference and current closed-loop curve parameters. The inverter drive module is used to use the bus voltage regulation threshold and the PWM drive duty cycle reference as control commands to drive the silicon carbide power device to perform high-frequency inversion. After the transformer step-down and secondary rectification and filtering, the initial welding DC power is output. The closed-loop control module is used to sample the output current and output voltage of the initial welding DC current in real time, and simultaneously analyze and extract the corresponding theoretical reference value from the current closed-loop curve parameters; compare the sampled output current and output voltage with the theoretical reference value to calculate the dynamic deviation, and adjust the current PWM drive duty cycle based on the dynamic deviation to achieve constant current control and parameter compensation in the welding process.

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