An electrical energy storage system is provided in this dislosure, which includes: M battery packs; M first DC/DC converters, where first terminals of the M first DC/DC converters are respectively connected to the M battery packs, the M first DC/DC converters are classified into N first DC/DC converter sets; and N second DC/DC converters, where the N second DC/DC converters one-to-one correspond to the N first DC/DC converter sets, a first terminal of each second DC/DC converter is connected to second terminals of all first DC/DC converters in a first DC/DC converter set corresponding to the second DC/DC converter, a second terminal of each second DC/DC converter is connected to a first interface of the electrical energy storage system, the first interface is to receive a direct current from a power generation system or output a direct current to the power generation system.