An energy storage system, wherein the energy storage system comprises M cell strings and N energy storage converters, a first end of any one of the N energy storage converters is coupled to at least one of the M cell strings, a second end of the any energy storage converter is configured to connect to a power grid, M and N are integers greater than 0, and M ≥ N; a first end of a first energy storage converter is coupled to Q cell strings in the M cell strings, the first energy storage converter comprises a direct current/alternating current DC/AC conversion unit and at least one direct current/direct current DC/DC conversion unit, Q is an integer greater than 0, Q ≤ M, and the first energy storage converter is any one of the N energy storage converters; a first DC/DC conversion unit is coupled to at least one of the Q cell strings by using the first end of the first energy storage converter, the first DC/DC conversion unit is coupled to the DC/AC conversion unit, the DC/AC conversion unit is coupled to the power grid by using a second end of the first energy storage converter, and the first DC/DC conversion unit is any one of the at least one DC/DC conversion unit; and the first DC/DC conversion unit is configured to perform adaptation between a voltage of the DC/AC conversion unit and a voltage of at least one of the Q cell strings, wherein both ends of any one of the at least one DC/DC conversion unit are connected in parallel to a switch; characterized in that the first energy storage converter is configured to detect voltages of the Q cell strings, and when a voltage of any one of the Q cell strings is greater than or equal to a first voltage threshold, a switch connected in parallel to a DC/DC conversion unit coupled to the cell string whose voltage is greater than or equal to the first voltage threshold is configured to be closed: and when a voltage of any one of the Q cell strings is less than or equal to a second voltage threshold, a switch connected in parallel to a DC/DC conversion unit connected to the cell string whose voltage is less than or equal to the second voltage threshold is configured to be open, wherein the first voltage threshold is greater than or equal to the second voltage threshold. a first end of a first energy storage converter is coupled to Q cell strings in the M cell strings, the first energy storage converter comprises a direct current/alternating current DC/AC conversion unit and at least one direct current/direct current DC/DC conversion unit, Q is an integer greater than 0, Q ≤ M, and the first energy storage converter is any one of the N energy storage converters; a first DC/DC conversion unit is coupled to at least one of the Q cell strings by using the first end of the first energy storage converter, the first DC/DC conversion unit is coupled to the DC/AC conversion unit, the DC/AC conversion unit is coupled to the power grid by using a second end of the first energy storage converter, and the first DC/DC conversion unit is any one of the at least one DC/DC conversion unit; and the first DC/DC conversion unit is configured to perform adaptation between a voltage of the DC/AC conversion unit and a voltage of at least one of the Q cell strings, wherein both ends of any one of the at least one DC/DC conversion unit are connected in parallel to a switch; characterized in that the first energy storage converter is configured to detect voltages of the Q cell strings, and when a voltage of any one of the Q cell strings is greater than or equal to a first voltage threshold, a switch connected in parallel to a DC/DC conversion unit coupled to the cell string whose voltage is greater than or equal to the first voltage threshold is configured to be closed: and when a voltage of any one of the Q cell strings is less than or equal to a second voltage threshold, a switch connected in parallel to a DC/DC conversion unit connected to the cell string whose voltage is less than or equal to the second voltage threshold is configured to be open, wherein the first voltage threshold is greater than or equal to the second voltage threshold.