De-Coupled Control of Energy-Efficient High-Power CC/CV Power Source for Arc Welding

In industry, for proper utilization of large capital equipment for welding applications, a single large-current high-power converter is desired for dynamic control of several welding methods (e.g., for making joints, hard-facing, gouging, welding overlay, etc.). They mostly follow either constant voltage (CV) or constant current (CC) arc type. Due to completely different type of dynamic load characteristics involved, this article proposes a novel de-coupled control approach to guide the power source to independently take care of each arc type. It proposes feed-forward control for inherently self-regulating CV arc type where the electrode feeding is motorized. The second order sliding mode control (SOSMC) approach is proposed for robust control of disturbance prone CC arc type in manual welding. This article also details that, for welding applications using full-bridge dc–dc converter (FBDC), the robustness features of SOSMC would help reduce the current in all loss-making components in the primary side and reduce the maximum value of dc voltage needed in the secondary side. Both would help reduce the power loss significantly to boost the energy efficiency of the system. Finally, this article validates the proposed ideas in a 1000 A power converter for control of welding using both arc types.