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Application of computer simulation technology in inverter welding power supply

Abstract: inverter welding power supply is one of the main development directions of welding power supply. This paper introduces the development status and problems of inverter welding power supply at home and abroad, and points out the necessity of using computer simulation technology to develop welding inverter power supply. After reviewing the development of computer simulation technology, especially the current situation and characteristics of power electronic simulation technology, combined with its application in the field of welding power supply, this paper introduces several commonly used circuit simulation software and its application characteristics. Finally, the problems existing in the application of simulation technology in welding inverter power supply are deeply analyzed, and its development trend is prospected

key words: computer simulation; Welding inverter power supply

0 preface

the manufacturing of welding power supply has a development history of more than 100 years. After entering the 1960s, silicon rectifier elements, high-power transistors (GTRs), MOSFETs, insulated gate bipolar transistors (IGBT) and other devices have emerged one after another, and the development of integrated circuit technology and control technology has provided a broader space for the development of electronic welding power supply, The most striking one is the inverter welding power supply [1]

inverter welding power supply has the advantages of small volume, light weight, energy saving and material saving, good control performance, fast dynamic response, easy to realize real-time control of welding process, and has great potential advantages in performance. From a long-term point of view, inverter welding power supply is the development direction of welding power supply, and the development of inverter welding machines abroad also fully illustrates this point. At present, inverter power supply has been widely used in manual arc welding, TIG welding and mig/mag welding in industrial developed countries. Several major welding machine manufacturers in the world have completed the serialization of inverter welding machine products, and take this as one of the symbols of the technical level

1 development status of welding inverter power supply

inverter power supply is called "tomorrow's power supply", and its application in welding equipment has brought revolutionary changes to the development of welding equipment [2]. First of all, the inverter welding power source can save 20% - 30% energy compared with the power frequency welding power source, and the efficiency can reach 80% - 90%; Secondly, the inverter welding power supply is small in size and light in weight. The weight of the whole machine is only 1/5 ~ 1/10 of that of the traditional power frequency rectifier welding power supply, reducing material consumption by 80% - 90%. In particular, the inverter welding power supply has the advantage of fast dynamic response speed, which is 2 ~ 3 orders of magnitude higher than the traditional power frequency rectifier welding power supply, which is conducive to the automation and intelligent control of the welding process. All these indicate that inverter welding power supply has a wide application prospect and market potential. Previously, among the arc welding machines of Panasonic Corporation and Osaka transformer Corporation, inverter welding machines accounted for more than 50%. Inverter welding machines produced by major welding machine manufacturers in the United States have exceeded 30%. The development speed of inverter welding power supply in other industrial developed countries is also very fast [2]

the research and development of inverter welding machines in China started in the late 1970s and began to develop in the 1980s. In 1982, Chengdu Electric Welding Machine Research Institute began the research on thyristor inverter arc welding rectifier, developed China's first commercialized ZX inverter arc welding power supply in 1983, and passed the ministerial appraisal of the project. Subsequently, Tsinghua University, Harbin Institute of technology, South China University of technology and time company successively launched inverter welding machines using various switching elements. At present, four generations of inverter welding machine power supply have been formed in China: the first generation is the inverter with SCR as the main power device; The second generation is transistor inverter; The third generation is FET inverter; The fourth generation is IGBT inverter, which has high inverter frequency, low saturation voltage, low power consumption, high efficiency and no noise. Compared with the previous three generations of inverters, it has more obvious advantages [3]

the broad prospects for the development of inverter welding machines have attracted many colleges and universities and research institutes. However, due to the combination of strong current and weak current of inverter welding power supply, the traditional test method will not only consume a lot of manpower, material resources and time, but also some problems are difficult to find and solve by the test method. Therefore, it is necessary to propose new design methods and means

in recent years, the methods of circuit analysis and design have developed rapidly due to the use of computer simulation technology. The circuit design adopts computer simulation technology to quickly simulate and analyze different design schemes, and after the circuit form is determined, the sensitivity analysis and tolerance analysis of the circuit component parameters are carried out, so as to optimize the component parameters and ensure the design quality. Therefore, the use of computer simulation technology in circuit design can greatly reduce manual labor, shorten the design cycle, and reduce the design cost. At present, in the research of power electronic devices, more and more devices use computer simulation technology. For high-power welding inverter power supply, its working environment and load conditions are very bad, and the power devices used are very expensive, so it is more advantageous to use computer simulation technology in the design of welding inverter power supply

2 computer simulation technology

2.1 development status of computer simulation technology

computer simulation technology combines modern simulation technology with the development of computer. By establishing the mathematical model of the system, taking computer as a tool and numerical calculation as a means, experimental research is carried out on the existing or envisaged system [5]. 3. Ensure the smoothness of metal materials in China, since the mid-1950s, system simulation technology has been applied in aerospace, aviation, military and other cutting-edge fields, and has achieved significant results. Since the early 1980s, with the wide application of computers, digital simulation technology has also been widely used in automatic control, electrical transmission, machinery manufacturing, shipbuilding, chemical engineering and other engineering technology fields

compared with traditional empirical methods, the advantages of computer simulation are: ① it can provide complete and detailed data of all relevant variables in the whole computer domain; ② No systematic experiment is needed; ③ It can predict the change process and final result of a specific process, so that people have a deep understanding of the law of process change; ④ It is the only research method when the measurement method is difficult. In addition, digital simulation also has the advantages of high efficiency, high accuracy and it is difficult to carry out destructive or dangerous experimental research on the actual system br>2.2 research status of power electronic simulation technology

the application of simulation technology in power electronic circuits is a very important part of its many applications, and has become an indispensable and important tool to carry out this research. In the design of power electronic circuits, computer simulation is mainly used for the verification of design schemes, the prediction of system performance, the discovery of potential problems of new products and the evaluation of problem-solving methods. It mainly solves two problems, that is, how to establish circuit equations and how to solve circuit equations

since the 1970s, the analysis methods used in circuit simulation mainly include: state variable method, node analysis method, improved node analysis method and state space average method. These modeling methods have their own advantages and disadvantages, and have their own scope of use. In specific use, corresponding methods should be used to establish specific simulation models according to specific purposes

it is often very difficult to accurately analyze the spatial and dynamic performance of switching converter, which is a strong nonlinear time-varying system. Establishing an accurate mathematical model has always been a difficult problem in the field of power electronics. Usually, only by assuming certain conditions and ignoring some secondary factors, can we get a suitable mathematical model in a certain range, which can provide help for the analysis and design of circuits. There are usually two methods for modeling: ① establish a physical electrical model according to the physical law of carrier movement in the device; ② An equivalent macro model is established according to the external behavior of the device [7]

in recent decades, many scholars at home and abroad have done a lot of work in the modeling of electromagnetic devices. The first problem to be solved is to describe the magnetization characteristics of magnetic materials. Among them, the more practical models include the J-A model with clear physical meaning and the macro model constructed using general component models. Based on the magnetic material model, the magnetic circuit model of electromagnetic devices can be determined by comprehensively applying Faraday, ampere and Gauss laws. According to the coupling principle of circuit and magnetic circuit, the circuit model of electromagnetic device can be established [7]

in a word, the modeling, theoretical analysis and computer simulation technology of control circuit has been relatively mature, while the practical simulation model of power electronic devices and electromagnetic devices, especially the parameter acquisition technology, needs to be further improved

2.3 commonly used circuit simulation software

commonly used circuit simulation software includes PSpice, saber, Simplis, MATLAB, etc. Generally, the power supply electronic simulation software is divided into two kinds: the simulator that focuses on circuit and the simulator that focuses on equation solving. PSpice, SABERT and MATLAB are the representatives of the two kinds of simulators respectively

Pspice is one of the earlier EDA software, which was launched by Microsim in 1985. In circuit simulation, its function can be said to be the most powerful, and it is widely used in China. Pspice 6.2 is widely used now. It works in Windows environment and takes up more than 20 megabytes of hard disk space. Pspice can carry out various circuit simulation, excitation establishment, temperature and noise analysis, analog control, waveform output, data output, and display analog and digital circuits at the same time in the same window. No matter which device or circuit is simulated, including IGBT, pulse width modulation circuit, a/D conversion, D/a conversion, etc., accurate simulation results can be obtained. For components and modules that are not in the library, you can also do it yourself

matlab 5.2 was launched by MathWorks in 1998. The newly added power system blockset (PSB) contains component models under certain service conditions, including power system network components, motors, power electronic devices, control and measurement links, three-phase component libraries, etc. with the help of other module libraries or toolboxes, the simulation calculation of power system can be carried out in the Simulink environment, Complex control method simulation can be realized, and the execution process of simulation can be observed at the same time. The simulation results are stored in the workspace of MATLAB with variables at the end of the simulation

pspice and PSB simulation software have their own application advantages, and their versions are also constantly updated. PSB has now launched version 6.1. PSB is applicable to the simulation of medium-sized circuits and the circuit simulation of variable/fixed step size simulation algorithm

the powerful computing power of matlab/simulink is very convenient for the post-processing of simulation results. Pspice is suitable for component level modeling of small-scale systems. If the system scale is too large, the simulation execution time will become very long [8]

3 application status of computer simulation in welding inverter power supply

at present, computer simulation technology has been widely used in aviation, aerospace, military and other cutting-edge technology fields, and has played a huge role. A few years ago, welding technology researchers began to introduce it into welding power supply, and made some achievements, but its research is not very in-depth, and there are not many literatures in this regard

it can be seen from the existing literature that the simulation technology in arc welding inverter is relatively mature. The earliest research in this area is the China University of technology, which undertakes the National Natural Science Foundation Project "arc"

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