SOC balance-based decentralized control strategy for hybrid energy storage in integrated power systems

The hybrid energy storage systems (HESSs) in vessel integrated power systems can support pulse load and improve system stability. However, the unbalanced SOC of different energy storage devices can cause over-charge and over-discharge which damages the energy storage devices and affects the stable operation of the entire system, especially when there are multiple groups of HESSs. Therefore, a decentralized control strategy for the HESSs in integrated power systems (IPSs) based on extended droop control combined with SOC balance control is proposed in this paper. In the proposed strategy, SOC recovery control is introduced to the virtual capacitance droop coefficient of the supercapacitor, and SOC equalization control is introduced to the virtual resistance droop coefficient of the lithium battery to adjust the output characteristics of the HESS according to the SOC. Then the frequency response characteristics are analyzed and the stability of the system is calculated. Finally, the hardware in loop simulation is conducted to verify the effectiveness of the proposed strategy. Comparisons show that the proposed strategy can compensate for the pulse load according to the responding characteristics of the HESS and achieve SOC balance between different energy storage devices under various working conditions.