Decentralized control for renewable DC Microgrid with composite energy storage system and UC voltage restoration connected to the grid

In this paper we propose a new decentralized control strategy applied to a DC Microgrid in order to manage the power delivery of storage devices into a common DC-link, avoiding high-bandwidth communication (HBC) between the storage devices (SD) and alternative sources. Batteries and Ultracapacitors (UC) are used as SD and the common DC-link is fed by alternative sources such as photovoltaic panels, wind turbines and fuel cells as well. The batteries are used to supply/absorb extra power in steady-state regime while the UC absorbs the power transients caused by variations on the power production or load connections. The proposed strategy uses as input for the batteries control only the DC-link voltage and state of charge (SOC), while for the UC only the DC-link voltage and UC terminal voltage are used to achieve the power sharing among the storage devices, equalization of the batteries and voltage restoration of the UC without HBC. The DC-link voltage is not restored in order to work as the sharing signal between storage devices. Additionally, the DC Microgrid is connected to the AC grid in order to deliver the extra power to the distributed system; however, the voltage variation on the DC-link does not affect the power quality of the produced energy. Simulated and experimental results are presented to demonstrate the feasibility of the proposed approach.