Provided is a converter system including: a plurality of converter modules connected to one power source in parallel; and a controller for storing mapping information of first parameters corresponding to processing power of the converter modules and second parameters corresponding to the number of converter modules that optimally process the processing power among the converter modules, configuring a value of the first parameter according to a measurement value of power input into the converter modules or power output from the converter modules, calculating a value of the second parameter by substituting the value of the first parameter into the mapping information, selecting the number of converter modules corresponding to the value of the second parameters as active converter modules from the converter modules and processing the processing power by using the active converter modules, and controlling output power of the active converter module to gradually increase or decrease in a transient state where the value of the second parameter is changed.