Provided is a method of controlling a three phase equivalent voltage in a multilevel inverter including sensing a state of each of power cells (120) of the multilevel inverter to determine whether or not failure occurs at each of the power cells, bypassing power cells which are determined as being failed to connect power cells operating normally to each other in series per each phase, calculating an offset voltage value using a phase voltage reference per each phase and a sum of each of direct current, DC, link voltages of the power cells which operate normally and configure each of the phases, and calculating a pole voltage reference per each phase for maintaining an equivalence of a three phase line-to-line output voltage using the phase voltage reference per each phase and the calculated offset voltage.
