| Arc welding inverter has become currently the main direction of welding power, because of its high efficiency and energy-saving, small size, light weight, easy to realize automation and intelligent etc. IGBT inverter welding which is the typical representative on the market, is basically adopts hard switching technology or soft switch range is narrow. Therefore, this paper studies the phase shift full-bridge zero-voltage and zero-current soft switching PWM main circuit (FB-ZVZCS-PWM) and designs the software and hardware of its control system based on digital signal processor (DSP).Control system is the core of the whole arc welding inverter. This topic takes DSP TMS320F2812 produced by TI company as the core control chip. To save development time, increase the efficiency and ensure the system stability and reliability, this paper selects the Tech_V-2812 embedded control board as DSP minimum system. The board is produced by Beijing Tech Shine Technology Co., LTD. And then, this thesis focuses on the design of the arc voltage and current sampling feedback circuit and the IGBT driving circuit. The software of the control system adopts the modular and structured programming design, mainly including main program, PWM generated subroutines, A/D conversion subroutines and fuzzy control subroutines. According to the feedback of the arc voltage and current, the fuzzy controller calculates system duty factor incremental, control PWM phase-shifting angle, and then control the output voltage, current, and power external characteristics.This paper establishes the phased-shift PWM model, the power load model and the soft switch inverter main circuit model, by MATLAB/SIMULINK toolbox. The simulation results prove that the main inverter circuit well implements zero voltage switch of the advanced bridge and zero current switch of the retarding bridge, and reduces duty ratio loss of the secondary side of the transformer. On this basis, this paper builds the sampling keep model, the soft start-up model, and the fuzzy control simulation model through which the various kinds of power external characteristics are gotten such as constant voltage, constant current, outer-drawing current and so on. Through the simulation of fuzzy controller, the quantification factors and the scaling factor have been optimized, and the waveform of the arc voltage and current has been given and made detailed analysis in different load conditions. The result is showed that the design of the fuzzy control system can be good for power external characteristics in welding. |
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