Device for controlling inverter

An inverter-controlling device for controlling an inverter system, wherein the inverter system comprising an inverting module including a plurality of switching elements for supplying the AC voltage to a motor, the inverter-controlling device includes:

• a main controller configured to generate a predetermined command current when the supply of the AC voltage to the motor stops;
• a comparison module configured to calculate a difference between the command current and an output current of the inverting module;
• a current controller configured to perform a proportional-integral (PI) control based on the difference;
• and
• a frequency estimation module configured to estimate a rotation speed of the motor based on a current response to the command current while the command current is injected to the current controller,
• wherein the main controller is further configured:
• when a flying start operation of the inverting module begins, to set an output frequency of the inverting module based on the rotation speed of the motor estimated by the frequency estimation module.