Power-sharing for dc microgrid with composite storage devices and voltagerestoration without communication

In this paper, we propose a new decentralized control and power-sharing strategy to manage the powerflow among energy sources (ESs), energy storage systems (ESSs) and the common dc-link. In the proposedtechnique, we eliminate all communication among the ESSs, to reduce the complexity and increase reliability,maintaining dc-link voltage restoration. In this context, batteries and ultracapacitors (UCs) are the ESSs,while ESs can be any power source such as photovoltaic, wind, fuel-cell and etc. This technique sharesthe microgrid power imbalance between batteries, proportionally to their state-of-charge (SoC) and energycapacity, achieving SoC equalization. The technique also promotes voltage restoration for the UCs, keepingtheir average voltage constant after supplying the power peaks during power transients. For all ESSs only localvariables are measured, such as local current and dc-link voltage, with no shared data between ESSs. Smallsignal and stability analysis are performed, along with experimental results in a lab bench show the feasibilityand performance of the technique.