On Bidirectional DC Nano-Grids: Design Considerations and an Architecture Proposal

The use of DC distribution networks has several advantages, especially for energy saving and integration of energy storage system and renewable energies. In this regard, DC nano-grids are a very interesting solution when distributing electrical power in households. In this paper, an analysis about the possible bidirectional capability of this DC nano-grid is presented. The end-user can freely connect either a passive load (demanding power) or an active one (able to sink current to the grid). The analysis is divided into three different parts. First, a discussion about the most promising power architecture is addressed, taking into consideration the loads in a house. Second, a standard for voltage regulation in a bidirectional DC nano-grid is proposed. Finally, a possible bus provider for this particular bidirectional DC nano-grid is also addressed. This power converter is based on a Dual Active Bridge cascaded with five synchronous buck converters. The key design aspects of the proposed topology are analyzed to emphasize the particular constraints imposed by the standard and the power architecture. A 500 W, 380 V to 24 V bidirectional bus provider has been built in order to experimentally validate the standard proposal and the design aspects.