Method for controlling multilevel converter

The present invention provides a method for controlling a multilevel converter which improves efficiency. The present invention provides the method for controlling the multilevel converter comprising; a step of sensing a modulation state value of sub modules and a current direction; and a step of designating average switching times per one period of an output waveform of one sub module according to the state value and the current direction. The step of designating average switching times comprises; a step of grouping the sub modules according to the on and off states of the sub module; a step of comparing the number of the sub modules of the on state with the number of the sub modules of the off state and changing the state according to the difference; a step of comparing the sub modules of the on state having a high voltage with the sub modules of the off state having a low voltage value as a predetermined value in a charging condition and changing the state of the compared sub modules of the on and off states; and a step of comparing the sub modules of the on state having a low voltage with the sub modules of the off state having a high voltage as a predetermined value in a discharging condition and changing the state of the compared sub modules of the on and off states if a value of the sub modules of the off state is high.