Power Allocation Control Method for Hybrid Energy Storage System of Lithium Ion Battery and Supercapacitor

In this paper, a hybrid energy storage system with energy balance is presented to solve the capacity limitation of supercapacitor (SC) in traditional power allocation methods. Power allocation is realized by droop control algorithm. Energy equalization is realized by model predictive control algorithm. Bidirectional energy equalizers transfer energy between supercapacitor and batteries. Therefor supercapacitor can continuously absorb or provide high-frequency fluctuating power while batteries are responsible for steady-state power only. It can protect batteries and prolong the life cycle of the system. For different working states of system such as load switching, the simulation of hybrid energy storage system consisting of 25.6V series batteries, 16.2V supercapacitor and 48V bus voltage is carried out. The result verified the effectiveness of the proposed system structure and control methods.