An AC–DC Hybrid Nanogrid System for PV and Battery Storage Based Futuristic Buildings

A seven-bus ac-dc hybrid nanogrid system for futuristic buildings (FBs) and its related control strategy are proposed in this article. The nanogrid has one ac bus and six dc buses which can be operated simultaneously and power from any bus can be transferred seamlessly to the other buses. Further, two dc buses and the ac bus are designed to operate both in the grid connected as well as in stand-alone mode. The other two dc buses are meant for interfacing solar photovoltaic (PV) system and the battery storage. The remaining two dc buses are configured to negotiate loads at medium voltage levels. The reconfigurable feature of some of the buses enhances the applicability of the nanogrid for powering a wide range of home appliances. The battery bus and the PV bus are designed for low voltage rating to minimize the series connection of batteries and PV modules, respectively. Further, the requirement of lower number of series connected modules for the PV array minimizes the effect of shading which is normally experienced in case of roof top installations. The system is also made transformerless, thereby reducing its size, volume, and weight as compared to the schemes involving line frequency transformers. The viability of the proposed nanogrid system is validated by performing detailed experimental studies on a laboratory scale 1.2-kW nanogrid system developed for the purpose.