There is disclosed a large scale energy storage system enabling balanced control of inverters, the large scale energy storage system including an inverter controller comprising a PWM generation circuit configured to generate a reference PWM signal and a first O/E converter configured to convert the reference PWM signal transmitted from the PWM generation circuit into an optical signal and to output the optical signal, and a plurality of PCS inverters configured to output a grid voltage, each of the PCS inverters comprising a second O/E converter embedded therein to convert the PWM signal and the optical signal output from the inverter controller into an optical signal and a plurality of inverter modules.