A new digital control system based on the double closed-loop for the full-bridge inverter

The control system based on the primary current feedback mode can effectively suppress the magnetic bias and avoid the overcurrent for the full bridge inverter. But in the process of its digitalization, the magnetic bias signal can be missed easily and the control accuracy is low, resulting in poor system stability and reliability. First, a new double closed-loop digital control method is proposed, which has advantages of the magnetic bias suppression in the primary current feedback mode and fast fine current adjustment in the secondary current feedback mode. Second, results of theoretical analysis on system stability and simulation prove that the method is feasible. Third, a single-chip design idea based on analog-digital mixed field-programmable gate array (FPGA) is proposed, and the detailed design program is described for the submerged arc welding system, which has high integration and strong anti-interference. Experimental results show that the digital control system has high stability and reliability to produce high submerged arc welding quality.