A Temperature-Suppression Charging Strategy for Supercapacitor Stack With Lifetime Maximization

It is expected, the growing demand for supercapacitor energy storage system (ESS) in which thousands of supercapacitor cells are connected as a stack for meeting the desired load power. The lifetime of ESS dramatically depends on the operating thermal effects of individual cells. In this paper, a temperature-suppression charging strategy is proposed for supercapacitor ESS to maximize its lifetime. First, the charging current and equivalent series resistance (ESR) construct the supercapacitor thermal model, and the ESR represents the degradation degree of the supercapacitor. Second, the maximization of system lifetime and equalization of unit degradation degree jointly form a convex optimization problem with the charging time constraint. The optimization problem is solved to obtain the equivalent charging current, which is realized through pulse width modulation (PWM) digital control. Simulation and experimental results show that the proposed method has the advantages of reducing ESS operating temperature and maximizing its lifetime.