Design and Verification of a DC Direct-mounted Energy Storage Topology

The modular multilevel converter based battery energy storage system (MMC-BESS) has the problem of pulsating current affecting battery life, and the high cost of retrofitting traditional modular multilevel converter (MMC) stations. The proposed DC direct-mounted energy storage topology in this paper is battery friendly and required number of battery cells is only 1/6 of MMC-BESS, greatly saving costs. This paper analyzes the topology structure and working principle of DC direct-mounted energy storage devices, and proposes a design method for the DC direct-mounted energy storage devices. The proposed design method is validated through simulation and prototype experiments. The simulation and construction of a DC 750V prototype have verified that the prototype has achieved good charging and discharging functions for DC energy storage, with small fluctuations in DC grid connected current and good power control effect. This study can provide reference and guidance for the design and application of high-voltage and high-capacity direct current energy storage devices that support offshore wind power to move towards the deep sea in the future.