Development Of Underwater Local Dry Welding Power Source Based On Single-chip Microcomputer Control

In recent years,my country has implemented a series of major special marine resource development projects,which has promoted the rapid growth of the number of important marine engineering facilities such as offshore oil platforms and various submarine pipelines.The connection and repair of underwater welded structural parts of marine engineering facilities are inseparable from underwater welding technology.At the same time,the quality of underwater welded joints is also related to the reliability and safety of the entire marine engineering facility.At present,due to the blockade of advanced underwater welding technology by developed countries such as Europe and the United States,the special underwater welding equipment imported from abroad is expensive.Therefore,the low-cost traditional land-use analog welding power source is still used in China for conventional underwater welding operations.However,the traditional land-use analog welding power sources not only have problems such as slow response speed and low control accuracy,but also are affected by the deep water environment,resulting in unstable underwater welding arcs,excessive spatter and unsightly weld formation;Therefore,in order to effectively improve the quality of underwater welded joints,it is essential to develop a local dry welding power source with fast response speed,high control accuracy and less spatter.This thesis combines high-frequency power electronic technology and single-chip microcomputer technology to design an underwater local dry welding power source based on single-chip microcomputer control.The design content of the welding power source includes three parts: design of the power main circuit,design of the digital control circuit and design of the software program.The power main circuit adopts saturated inductance IGBT full-bridge inverter soft-switching topology to meet the application requirements of high current,high power and low energy consumption,it mainly includes input rectifier and filter circuit,IGBT full-bridge inverter soft switching circuit,intermediate frequency transformer,output rectifier and filter circuit;The digital control circuit adopts the 32-bit micro-control unit PIC32MK0512GPG048,and use it as the control core to build peripheral functional hardware circuits,mainly including main control circuit,auxiliary power supply circuit,drive circuit,motor control circuit,parameter preset and display circuit;The design of the software program uses MPLAB X IDE as the desktop development environment,including two parts of the main program and function subprograms,which realizes the control of the welding output waveform.In this thesis,the developed underwater local dry welding power source based on single-chip microcomputer control is tested in blocks,and the working conditions of the main power circuit and the digital control circuit are tested respectively.After testing the two parts of the circuit to work normally,then carry out the welding output test of the whole machine.The test results show that the saturated inductance IGBT full-bridge inverter soft-switching circuit designed in this thesis can completely realize the ZVS of the two-arm IGBT and the ZCS of the lagging-arm IGBT,effectively reducing the IGBT voltage,current stress and IGBT power loss;The designed auxiliary power supply circuit's DC voltage ripple output from each secondary output terminal is less than 2%,which improves the stable operation of the control system;The designed integrated drive circuit has good performance and can output PWM drive signals with normal timing to ensure the reliability of the IGBT turn on and turn off;The designed underwater local dry welding power source has high output no-load voltage,fast response speed,high control accuracy,less spatter,and has good regulation characteristics.