Optimal Voltage Level for DC Microgrids

Depleting fossil fuels, increasing energy demand and concern over climate change due to CO2 emission motivate the use of renewable sources. However, supplying electronics, variable speed drives and LED loads from renewable sources requires multiple ac-dc and dc-ac conversions. This causes substantial energy wastage before end use. To address this limitation, dc system is suggested, which offers high efficiency and reliability with low system cost. In this paper, suitable power electronic interfaces for sources/loads/storage elements are discussed along with their performance requirements. Further, efficiency, cost and safety issues of the dc system with various voltage levels are compared. With suitable case studies, optimal dc voltage level is determined for residential and commercial application. The proposed dc system with this optimum voltage level offers 10-22% improvement in energy efficiency over the conventional ac system.