ENERGY STORAGE DEVICE AND SYSTEM, AND POWER SYSTEM

Embodiments of this application provide an energy storage device and system as well as a power system, and relate to the technical field of a power grid. The energy storage device includes: at least two parallel-connected energy storage units, where each energy storage unit includes: a battery cluster and a power conversion system; and the battery cluster includes at least two cells; a direct-current side of the power conversion system is electrically connected to the battery cluster, an alternating-current side of the power conversion system is configured to electrically connect to an input side of an alternating-current combiner cabinet, and an output side of the alternating-current combiner cabinet is configured to electrically connect to an alternating-current side of a transformer. The energy storage device is configured to improve safety and reliability of the energy storage system.