Static state power smoothing and transient power quality enhancement of a DC microgrid based on multi-function SMES/battery distributed hybrid energy storage system

Using hybrid energy storage system (HESS) to solve the issues of power regulation and fault protection of DC microgrids has attracted extensive attention. To realize multiple functions of power flow control and power quality enhancement of the DC microgrid, a concept of distributed HESS based on superconducting magnetic energy storage (SMES) and battery energy storage (BES) is introduced in this paper. A SMES-based energy-storage-composited DC transformer (ESDCT) is designed to interconnect the low-voltage DC microgrid into a medium-voltage DC power system. It is with the functions of DC voltage transformation, and grid fault isolation. The BES is selected to regulate the unstable output power of the LVDC microgrid caused by renewable energy generators and load variations. The modeling of the SMES-based ESDCT and the cooperative control of the BES and SMES is analyzed. Finally, the performance of the SMES/BES distributed HESS is verified via a simulation, and the feasibility of the proposed SMES-based ESDCT is demonstrated via a scaled-down experiment.