Study On Dsp Based Digital Control For Twin-wire Pulsed Mag High Speed Inverter Power Supply

Twin-wire pulsed MAG high speed welding technology possesses the advantages of high efficiency, quality and automation, and is paid much more attention today, it has become the research focus in the welding field. However, our country's research on it is later and can't produce this kind of twin-wire welding equipment in batch production. Under the project of Guangdong Industrial Technology research (No.2007A010300005), based on power electronics and digital control, this paper presents a research on the multi-phase digital synchronic control systems base on DSP for twin-wire pulsed MAG high speed welding power supply and their character and application.Firstly, the features of twin-wire pulsed MAG high speed welding are analyzed. The control system based on I/O communication of master and slave power supply is proposed. The main-circuit topology of the master and slave inverter is analyzed, and with the request of output power, the parallel full bridge inverter topology. To meet the requirements of control system for twin-wire pulsed MAG high speed welding power supply, the selection of external characteristic and the multi-phase digital synchronic control system are put forward.Secondly, the hardware and software of the multi-phase digital synchronic control system based on DSP are designed, it has been proved that the hardware and software are feasible and practical. Disturbance resistance of the hardware and software is also designed via investigating disturbance source of welding location.Thirdly, because the power supply choose the constant current external characteristic, it causes the disadvantages of weak arc voltage self-adjusting ability in master and slave power supply. In order to overcome the disadvantages and achieve the control of arc length, the voltage threshold method and PI control method of pulse base's time are adopted.Fourth, the digital system controller based on DSP and LCD of human machine interface (HMI) is designed in order that the Pulse MAG welding power supply's parameters can be given accurately, stored and displayed.This paper has designed the hardware about DSP with LCD, touch screen, EEPROM and other interface's circuit, and the corresponding software has also been designed. The human machine interface communicates with the welding process control system through the RS232 bus. It has achieved a digital man-machine interface.Finally, the technologic experiment of twin-wire welding was done with the equipment of twin-wire pulsed MAG high speed welding power supply and its multi-phase digital synchronic control system. The results of the experiment demonstrate that the developed twin-wire power supply's control system meet the design requirements, the twin-wire welding process was realized in synchronization, alternation and random three type phases output mode, and the merits of twin-wire pulsed MAG high speed welding are stable welding process, high speed, and high quality welding seam in the appropriate matching of the welding parameters.