A Droop Control Algorithm with Frequency Partitioning Capability and SoC Balancing for Different Energy Storage Systems

Energy Storage Systems (ESS) are essential elements of all DC microgrids to compensate for the uncertainties in renewable resources. When multiple ESS operate in parallel, their State of Charges (SoC) can deviate from each other if there is no control over them. Moreover, each ESS with its own converter has a dynamic that can respond to a specific load current frequency. Conventional droop controllers lack the consideration of these two concepts. By manipulating the droop controllers and through the introduction of non-linear droop controllers, ESS's dynamics can be taken into consideration. In this paper, a novel method of battery management is proposed to consider these criteria simultaneously. Simulation and hardware in the loop results demonstrate the proposed method effectiveness.