A Hierarchical Control of Supercapacitor and Microsources in Islanded DC Microgrids

Abstract

This paper proposes a hierarchical control approach for SuperCapacitor (SC) energy storage and microsources in islanded DC microgrids. It takes into account microsources' dynamic and steady-state limitations. The proposed approach relies on an architecture presented for the SC's and microsources' interfaces with the DC bus. In the proposed architecture, DC microsources interface with the DC bus through buck converters. Moreover, the SC interfaces with the DC bus through the bi-directional buck converter. The instantaneous loads currents are measured and employed in the secondary control to calculate the reference currents for buck converters. In the primary control, we run buck converters as current sources. Moreover, the bi-directional buck converter is run to regulate the DC bus voltage. The proposed approach is generic; meaning that it can be employed for any islanded DC microgrid. Without loss of generality, to prove its effectiveness, we utilized it for a Low Voltage DC (LVDC) microgrid in this paper. Analysis, design, simulations, and experimental verifications are presented for the LVDC microgrid. The experimental results confirm that, by employing the proposed approach, the DC bus voltage deviations from its reference voltage is 5% and it restores in less than $1~sec$.