Power conversion system for energy storage system and controlling method of the same

PURPOSE: A power converting system for an energy storage system and a control method thereof are provided to have an effect of reducing generation of the circulating current by connecting inverters in parallel. CONSTITUTION: A power converting system for an energy storage system comprises converting units (11) and an output controller (40). The converting units are composed of at least two, which are connected to one power source or a load, respectively. The output controller is composed of at least one, and controls at least one between two converting units to produce a reference voltage. At least one among the converting units comprises a sub converter and a sub converter controller. The sub converter is composed to have an input terminal connected to at least one power supply and an output terminal connected to the input terminal. The sub converter controller controls the output voltages so that plural sub converter output voltages are practically identical according to the reference voltage. The reference voltage corresponds to the output voltage and the output current of plural sub converters. [Reference numerals] (11) Electricity converting units; (12) DC link unit; (13) Bidirectional inverter; (14) Bidirectional converter; (15) First switch; (16) Second switch; (17) Integrated controller; (2) Power generating system; (3) System; (30) Battery; (4) Load