Stability Analysis of Battery-Supercapacitor Energy Storage System for Resistance Welding

This paper proposes a high-efficiency energy storage system within the micro resistance welding device based on battery-supercapacitor semi-active hybrid topology. A SEPIC converter is chosen for energy management between individual energy storages because it can considerably improve Li-ion battery performance in terms of shelf life and increase the overall system efficiency compared to other topologies. Accurate state-space mathematical model of SEPIC converter used within the hybrid energy storage system is obtained by means of average values analysis. It is then used to analyze the overall hybrid energy storage system stability by means of Nyquist stability criterion. The results show that the proposed battery-supercapacitor hybrid energy storage system should be characterized by stable behavior regardless of the variations of duty cycle and load current over a wide range of regimes.