Patent ID: 8884561

Claim:
An AC motor driving apparatus comprising: a DC power supply which supplies DC power; an inverter which is connected to the DC power supply via a DC bus bar and converts the DC power to AC power and supplies the AC power to an AC motor; and a power compensator which is connected in parallel with a DC power input portion of the inverter, wherein the power compensator includes: a power storage device which absorbs/discharges power; a step-up/down circuit which is connected between the DC bus bar and the power storage device and converts a voltage level; and a control device which controls the step-up/down circuit for exchanging DC power between the DC bus bar and the power storage device, and the control device performs: (A) a power compensation process A in which in a period when DC-power-supply power exchanged by the DC power supply exceeds a DC-power-supply power running power limit determined on the basis of power which can be supplied by the DC power supply, power supplied from the DC power supply is reduced to the DC-power-supply power running power limit by discharging energy stored in the power storage device, and in a period when the DC-power-supply power is less than a DC-power-supply regeneration power limit determined on the basis of power which can be regenerated by the DC power supply, power regenerated to the DC power supply is suppressed to the DC-power-supply regeneration power limit by charging the power storage device with energy; and a power storage adjustment process B including: (B-1) a process in which in the period when the DC-power-supply power exceeds the DC-power-supply power running power limit, energy of the power storage device is discharged to the inverter or the DC power supply such that a voltage of the power storage device becomes a predetermined value; (B-2) a process in which in the period when the DC-power-supply power is less than the DC-power-supply regeneration power limit, the power storage device is charged with energy from the inverter or the DC power supply such that the voltage of the power storage device becomes a predetermined value; and (B-3) a process in which in a period when the DC-power-supply power is not less than the DC-power-supply regeneration power limit and is not greater than the DC-power-supply power running power limit, the power storage device is charged in a power range of a difference between the DC-power-supply power running power limit and required power of the inverter, or is discharged in a power range of a difference between the required power of the inverter and the DC-power-supply regeneration power limit, such that the voltage of the power storage device becomes a predetermined value.