Electric ships have become popular for the purpose of reducing greenhouse gas emissions and improving energy efficiency. The DC shipboard microgrid (SMG) provides a good solution to integrate the battery energy storage system (BESS), generators, electric propulsion system, and shipboard loads. In order to avoid over-discharging and over-charging of batteries and prolong the battery lifetime, it is necessary to balance the state-of-charge (SoC) of batteries. This paper proposes a decentralized SoC balance method based on droop control in the DC SMG. The battery SoC balancing speed is regulated by an exponent parameter n, and larger n leads to faster SoC balance. In addition, the voltage drop caused by the proposed SoC-based droop control can be ensured within the allowed value in the entire SoC range. Verification of the proposed method is implemented in Matlab/Simulink model, which consists of two batteries. The simulation results verify the effectiveness of the proposed method.

DC shipboard microgrid,battery energy storage system,state of charge,droop control