Reduction of storage capacity in DC microgrids using PV-embedded series DC electric springs

In the integration of photovoltaics (PV) with the power grids, battery energy storage systems (BESS) are often adopted to buffer the intermittent solar power. For the PV-battery combination, the capacity of the BESS increases with the scale of PV integration, which increases the cost. In this paper, a PV-embedded series DC electric spring (PVES), which is a new combination of non-critical load, PV, and series DC electric spring (series ES), is proposed as a means for reducing the storage capacity as typically desired in microgrids. A comparison among the BESS, the series ES, and the PVES integrated DC microgrid is provided. Experimental works on a 48 V DC grid with constant and variable load have been performed to verify the storage reduction achievable with the PVES. The results show that the PVES can tackle the intermittency of the solar power with less energy storage capacity.