In DC microgrids, distributed energy storage plays a key role in stabilizing the DC bus voltage. The bidirectional DC/DC converter in the distributed energy storage system should be designed according to the voltage level and electromagnetic isolation requirements, and multiple energy storage units should be coordinated for load current distribution according to the state of charge (SOC). This paper proposes a SOC power index droop control strategy by communication lines to coordinate the fast and high-precision distribution of load current among multiple energy storage units, and the SOC between energy storage units quickly converges to a consistent state. Considering that communication lines are susceptible to interference, this paper further proposes an improved SOC power index droop control to overcome the effects of communication line failures. Considering the high cost of the energy storage unit, it should be connected to the DC microgrid in layers to achieve a reasonable allocation of resources in practical applications. In order to provide high-quality power to a large power grid, the quantification standards of the DC bus fluctuation range and the working range of each converter are further discussed to maximize the stability of the DC bus voltage and grid-connected power fluctuation.
Bidirectional DC/DC and SOC Drooping Control for DC Microgrid Application
