Speed estimation apparatus for AC motor, driving apparatus for AC motor, refrigerant compressor, and refrigeration cycle apparatus

A speed estimation apparatus for an AC motor, comprising:

• a model deviation calculation unit to calculate a model deviation based on a voltage, a current, and an estimated angular velocity of an AC motor;
• a first angular velocity estimation unit to calculate a first estimated angular velocity as a low-frequency component including a DC component of a real angular velocity based on the model deviation, the first angular velocity estimation unit having a first transfer function with maximum values in a first frequency range;
• a second angular velocity estimation unit to calculate a second estimated angular velocity as a high-frequency component of a real angular velocity based on a specific high-frequency component included in the model deviation, the second angular velocity estimating unit having a second transfer function with a peak in the specific high-frequency component, the specific high-frequency component being in a second frequency range non-overlapping with the first frequency range;
• and
• an adder to add the first estimated angular velocity and the second estimated angular velocity together to produce a sum of the first estimated angular velocity and the second estimated angular velocity such that the low-frequency component including the DC component and the high-frequency component are added, wherein
• the sum of the first estimated angular velocity and the second estimated angular velocity is fed back as the estimated angular velocity to the model deviation calculation unit.