SoC-based droop method for distributed energy storage in DC microgrid applications

With the progress of distributed generation nowadays, microgrid is employed to integrate different renewable energy sources into a certain area. For several kinds of renewable sources have DC outputs, DC microgrid has drawn more attention recently. Meanwhile, to deal with the uncertainty in the output of microgrid system, distributed energy storage is usually adopted. Considering that the state-of-charge (SoC) of each battery may not be the same, decentralized droop control method based on SoC is shown in this paper to reach proportional load power sharing. With this method, the battery with higher SoC supplies more load power, while the one with lower SoC supplies less load power. Different kinds of relationship between SoC and droop coefficient are selected and their performance of power sharing speed is evaluated. Small signal model of SoC-based droop method is reached to test the system stability. Theoretical analysis is validated by both simulation and experimental results.