A control device of a high voltage inverter, comprising: a phase shift transformer configured to shift phases (R, S, T) of inputted 3-phase voltage to generate a plurality of 3-phase voltages each having a different phase; an inverter configured to switch, by a plurality of U phase unit cells, a plurality of V phase unit cells and a plurality of W phase unit cells, the plurality of 3-phase voltage generated by the phase shift transformer to generate voltages each having a different phase, and to output a 3-phase high voltage to a load by combining the generated voltages of each phase; a plurality of current transformers (CTs) configured to detect a current of each phase outputted to the load by the inverter; and a master controller configured to determine a current level outputted to the load by the inverter using an output signal of the plurality of CTs to control a switching operation of the inverter, characterized in that the master controller determines self preset neutral point information and performs a communication with cell controllers each disposed at the plurality of U phase unit cells (112a∼112f), the plurality of V phase unit cells (114a∼114f) and the plurality of W phase unit cells (116a∼116f) and operates the high voltage inverter by allowing the cell controller to be set up with the same neutral point information as the self preset neutral point information, determines a polarity of a current supplied to a load and a polarity of current outputted by each of the plurality of U phase unit cells, the plurality of V phase unit cells and the plurality of W phase unit cells, if a trip is generated while the high voltage inverter is operated, and changes the set-up information on the neutral point set up in the master controller and the plurality of cell controllers to operate the high voltage inverter, if the polarity of the current supplied to the load is different from that of each of the plurality of U phase unit cells, the plurality of V phase unit cells and the plurality of W phase unit cells. a phase shift transformer configured to shift phases (R, S, T) of inputted 3-phase voltage to generate a plurality of 3-phase voltages each having a different phase; an inverter configured to switch, by a plurality of U phase unit cells, a plurality of V phase unit cells and a plurality of W phase unit cells, the plurality of 3-phase voltage generated by the phase shift transformer to generate voltages each having a different phase, and to output a 3-phase high voltage to a load by combining the generated voltages of each phase; a plurality of current transformers (CTs) configured to detect a current of each phase outputted to the load by the inverter; and a master controller configured to determine a current level outputted to the load by the inverter using an output signal of the plurality of CTs to control a switching operation of the inverter, characterized in that the master controller determines self preset neutral point information and performs a communication with cell controllers each disposed at the plurality of U phase unit cells (112a∼112f), the plurality of V phase unit cells (114a∼114f) and the plurality of W phase unit cells (116a∼116f) and operates the high voltage inverter by allowing the cell controller to be set up with the same neutral point information as the self preset neutral point information, determines a polarity of a current supplied to a load and a polarity of current outputted by each of the plurality of U phase unit cells, the plurality of V phase unit cells and the plurality of W phase unit cells, if a trip is generated while the high voltage inverter is operated, and changes the set-up information on the neutral point set up in the master controller and the plurality of cell controllers to operate the high voltage inverter, if the polarity of the current supplied to the load is different from that of each of the plurality of U phase unit cells, the plurality of V phase unit cells and the plurality of W phase unit cells.