Accurate Power Sharing With Balanced Battery State of Charge in Distributed DC Microgrid

This paper presents an accurate power sharing method to balance the state of charge (SoC) among the distributed battery energy units (BEUs) in a dc micro-grid. The virtual power rating concept of the proposed control method is introduced, and accurate power sharing is achieved according to the SoC levels and the virtual power ratings, regardless of the line resistance difference. With the accurate power sharing based on SoC, BEUs with higher SoC accurately supply more power to the system than the lower SoC BEUs during the discharging period, and BEUs with lower SoC accurately supply less power to the system than the higher SoC BEUs during the charging period. Moreover, with the voltage restoring method, the dc grid voltage is maintained within the desired voltage level, and with the proposed control method, the system stability is verified. The proposed control scheme is implemented in a distributed manner that relies on low bandwidth communication. The effectiveness of the proposed control method is proved by simulation and experiments.