Method for compensating instantaneous power failure in medium voltage inverter and medium voltage inverter system by using the same

A method for compensating instantaneous power failure in medium voltage inverter including a plurality of power cells supplying a phase voltage to a motor by being connected to the motor in series, the method comprising maintaining an output frequency during restoration as long as a predetermined time, in a case an input voltage of the plurality of power cells is restored after being less than a reference value.

A medium voltage inverter system, the system comprising:

• a plurality of power cells supplying a phase voltage to a motor by being connected to the motor in series;
• and a controller connected to the plurality of power cells via a network for decreasing an output frequency of the plurality of power cells by as much as a predetermined value at a relevant point where an input voltage of the plurality of power cells is less than a reference value, decreasing the output frequency at a predetermined deceleration gradient, and maintaining the output frequency during restoration of input voltage as long as a predetermined time, in a case the input voltage is restored.