Grid-connected power storage system and method for controlling grid-connected power storage system

A grid-connected power storage system for coupling a power generation system to a grid to supply power to a load system, comprising:

• a main battery for discharging stored power to the load system;
• at least one additional battery coupled to the main battery for discharging stored power to the load system;
• a bidirectional converter coupled to the main and additional batteries, and comprising a plurality of switches for performing a conversion between a DC link voltage, between the power generation system and the grid, and a battery voltage, a first switch of the plurality of switches corresponding to the main battery and a second switch of the plurality of switches corresponding to the additional battery, wherein the first and second switches are connected to each other in parallel;
• an integrated controller for selectively controlling operations of the first switch and the second switch based on an amount of power used by the load system;
• and
• a bidirectional inverter for converting the DC link voltage output from the bidirectional converter into an AC voltage of the grid and the AC voltage of the grid into the DC link voltage,
• wherein the bidirectional inverter is configured to supply power from the power generation system to the grid via the bidirectional inverter.