An energy storage system, comprising a plurality of energy storage branches, at least one switch unit, and a control circuit, wherein each of the energy storage branches comprises a first bus, a string-level converter, and a battery string that are sequentially connected in series, a plurality of balancing converters (11, 12, 13), and a shared bus, wherein the battery string comprises a plurality of battery units connected in series, and each of the battery units comprises one battery pack (A11, A12, A13); each of the battery packs is connected to an input side of one corresponding balancing converter, and output sides of the plurality of balancing converters are separately connected to the shared bus; and a positive terminal of the battery string is connected to the string-level converter, and a negative terminal of the battery string is connected to a reference ground; the string-level converter is configured to: modulate a voltage on the first bus to a charging voltage, to charge the battery string; or modulate a voltage of the battery string to a discharging voltage, to charge a load coupled to the first bus; each of the balancing converters is configured to: when the balancing converter operates in a first working mode, balance a current of a connected battery pack; and when the balancing converter operates in a second working mode, modulate a voltage of the shared bus to a charging voltage, to charge the connected battery pack; or modulate the voltage of the connected battery pack to a discharging voltage, and output the discharging voltage to the connected shared bus; the switch unit is disposed between two neighboring energy storage branches; and shared buses in the two energy storage branches are turned on when the switch unit is in a first state, or the shared buses in the two energy storage branches are not turned on when the switch unit is in a second state; and the control circuit is separately coupled to the at least one switch unit and each of the energy storage branches, and is configured to: when any component in a first energy storage branch in the two neighboring energy storage branches is faulty, control a switch unit between the first energy storage branch and a neighboring second energy storage branch to be in the first state, and control an operating mode of each of the balancing converters in the first energy storage branch to switch from the first working mode to the second working mode, wherein the any component comprises a battery pack and/or a string-level converter. each of the energy storage branches comprises a first bus, a string-level converter, and a battery string that are sequentially connected in series, a plurality of balancing converters (11, 12, 13), and a shared bus, wherein the battery string comprises a plurality of battery units connected in series, and each of the battery units comprises one battery pack (A11, A12, A13); each of the battery packs is connected to an input side of one corresponding balancing converter, and output sides of the plurality of balancing converters are separately connected to the shared bus; and a positive terminal of the battery string is connected to the string-level converter, and a negative terminal of the battery string is connected to a reference ground; the string-level converter is configured to: modulate a voltage on the first bus to a charging voltage, to charge the battery string; or modulate a voltage of the battery string to a discharging voltage, to charge a load coupled to the first bus; each of the balancing converters is configured to: when the balancing converter operates in a first working mode, balance a current of a connected battery pack; and when the balancing converter operates in a second working mode, modulate a voltage of the shared bus to a charging voltage, to charge the connected battery pack; or modulate the voltage of the connected battery pack to a discharging voltage, and output the discharging voltage to the connected shared bus; the switch unit is disposed between two neighboring energy storage branches; and shared buses in the two energy storage branches are turned on when the switch unit is in a first state, or the shared buses in the two energy storage branches are not turned on when the switch unit is in a second state; and the control circuit is separately coupled to the at least one switch unit and each of the energy storage branches, and is configured to: when any component in a first energy storage branch in the two neighboring energy storage branches is faulty, control a switch unit between the first energy storage branch and a neighboring second energy storage branch to be in the first state, and control an operating mode of each of the balancing converters in the first energy storage branch to switch from the first working mode to the second working mode, wherein the any component comprises a battery pack and/or a string-level converter.