Adaptive droop control scheme with error functioned-based SoC balancing for distributed battery storage system in renewable energy-based DC shipboard microgrid

As the world faces increasingly severe energy shortages and environmental pollution, the maritime industry is compelled to explore new energy solutions for sustainable and environmentally friendly ship operations. DC microgrid systems are garnering increased attention because of their significant advantages in facilitating the integration of sustainable energy sources. This paper introduces an adaptive droop control strategy with an error function-based State-of-Charge (SoC) equilibrium approach for parallel battery storage systems within renewable energy-based DC shipboard microgrids. The strategy addresses critical challenges such as maintaining dynamic SoC equilibrium, ensuring precise load current sharing, and regulating DC bus voltage. In the primary control layer, this work introduces a novel SoC-based current sharing (SBCS) controller that utilizes SoC information and dynamically adjusts droop coefficients based on an error function. The SBCS is designed to dynamically balance the state of charge (SoC) while ensuring accurate current distribution among the energy storage units (ESUs). This controller also lessens the severity of line impedance mismatches. Additionally, to mitigate deviations in the DC bus voltage, a Voltage Drop Compensation (VDC) controller is employed at the secondary control level. In the communication level, communication is recognized through a series of sparse systems, with each ESU communicating exclusively to its neighboring ESUs. An iterative multi-agent consensus method is applied to collectively estimate the average of global variables, thereby reducing communication overhead and enhancing coordinated control.Furthermore, this paper carries out a comprehensive stability assessment of the proposed control methodology. Lastly, To validate the effectiveness of the proposed approach, a MATLAB/Simulink simulation platform and a Star Sim HIL experimental environment have been established. The findings demonstrate that the introduced methodology successfully achieves SoC balance, accurate current distribution, and restoration of bus voltage across diverse operating conditions. Additionally, it demonstrates significantly rapid SoC equalization compared to current modern and advanced approaches.