High-voltage energy storage system and device at power grid side

The utility model discloses a high-voltage energy storage system at a power grid side. The high-voltage energy storage system comprises an access unit, a reactance unit, a current conversion unit and a battery unit, the access unit comprises an isolating switch and a starting loop, the isolating switch is used for isolating a power grid from the starting loop, and the starting loop is used for pre-charging and accessing high-voltage electricity of the power grid to the reactance unit; the reactance unit is connected with the starting loop and the current conversion unit, the current conversion unit comprises a first bridge arm structure and a second bridge arm structure, and the first bridge arm structure and the second bridge arm structure are symmetrically arranged; the battery unit is connected with the current conversion unit and comprises a plurality of battery monomers which are connected in series. Internal circulation is effectively avoided through series connection of the battery monomers, the capaci