Provided is a method of controlling a power supply system for supplying power to a load in conjunction with a generation system, a battery and a system, including a determining step whether connection of the system with the load and a method of controlling to operate as independent power generating system or in grid-connected power generation system. [Reference numerals] (10) Switch 1; (2) System; (3) Power System; (30) Switch 2; (40) Switch 3; (70) Critical load; (80) Typical load
