DC electric springs with modified droop control for storage reduction in DC microgrids

Series DC electric springs (series ESs) can be a cost-effective technology to tackle the intermittency of the renewable generations in DC distribution grids. When multiple series ESs are connected to differently rated non-critical loads (NCLs) and are operated to regulate the voltages at their respective points of common coupling, the charging and discharging characteristics among the ESs are different. In this paper, a modified droop controller, which is designed to reduce the total storage capacity of the series ES, is proposed to coordinate the operation of multiple series ESs. The power curves of series ESs with light, medium, and heavy NCLs are compared and analyzed. Experimental results on a 60 V DC grid have confirmed that the proposed controller can effectively reduce the total storage capacity with good coordination among multiple series ESs.