基于级联多电平直流变换器的超级电容 储能系统能量自均衡控制策略

Energy-balancing control is one of the key problems to be solved urgently in energy storage system. This paper proposes an energy self-balancing control strategy based on cascaded multilevel super capacitor energy storage system. This strategy adopts super capacitor state-of-charge (SOC) to build separated half bridge sub-module current loops. Accordingly, the average operating current of each module can be independently controlled according to super capacitor SOC. Therefore, the proposed strategy can directly use system current to achieve energy balance between sub-modules without affecting the current response of system. Meanwhile, to solve the issue of the balancing speed reduction in the process of energy balance, a weight coefficient based on SOC is designed to promote the balancing speed. The proposed strategy does not affect the ability of energy storage system to stabilize DC bus voltage, avoids the external balancing circuit, and simplifies the entire control of energy storage system. At last, the proposed strategy is verified by the experimental results.