An advanced DBS strategy for a DC nanogrid integrating several energy storage technologies

A DC nanogrid is a hybrid power supply system integrating several small-scale resources, generation, conversion and storage technologies on a common DC bus. To ensure a reliable, safe and efficient operating condition, all resources included in a DC nanogrid must be properly integrated and a suitable control strategy has to be implemented. A distributed control strategy based on DBS is usually applied to control a DC nanogrid. The DBS is used as a distributed decentralized control strategy in which the control nodes, the source/storage interface converters, induce DC bus voltage-level changes to communicate with the other control nodes. It is an extension of the concept of using charge/discharge thresholds to schedule individual sources in a distributed fashion, which induces DC bus voltage level changes to activate communications between difference source/storage interface converters. A DC bus voltage threshold is assigned to each converter to trigger the point at which it begins discharging or charging. In this paper, an advanced DBS is proposed. More in detail, the DC bus voltage thresholds are dynamically changed depending on the real DC nanogrid configuration. Two case studies are analyzed to show the ability of the proposed advanced DBS to make the DC nanogrid stable in all normal and critical operating conditions.