AN ENERGY STORAGE SYSTEM FOR A DIRECT CURRENT TRANSMISSION SYSTEM AND A METHOD FOR EXCHANGING ENERGY WITH A DIRECT CURRENT TRANSMISSION SYSTEM

There is disclosed herein an energy storage system for a direct current (DC) transmission system, the energy storage system being configured to be connected to a DC link. The energy storage system comprises a first system terminal, a second system terminal, a first converter connected to the first system terminal, and a second converter connected to the first converter and the second system terminal. The energy storage system further comprises an AC loop device providing an alternating current (AC) path, and a plurality of energy storage devices connected in parallel with the second converter comprising a cell having power electronic switches, and an energy storage element connected to the cell, wherein the cells are individually switchable. The present disclosure further relates to a method for providing energy storage to a DC transmission system.