Patent ID: 7960926

Claim:
A controller for an AC rotary machine, which controls an AC rotary machine, the controller comprising: a power converter that generates a three-phase AC output voltage being able to be varied in voltage and frequency to be corresponding to a three-phase voltage instruction value, and supplies the three-phase AC output voltage to the AC rotary machine; current detection means that detects a three-phase current of the AC rotary machine; angular-frequency estimate output means that outputs an angular-frequency estimate value being an estimate value of angular frequency of the three-phase AC output voltage; voltage instruction calculation means that calculates a voltage instruction value based on a current instruction value and the angular-frequency estimate value in a rotating biaxial coordinate system; phase calculation means that calculates a phase θin the rotating biaxial coordinate system from the angular-frequency estimate value; dq-axis/three-phase conversion means that converts the voltage instruction value in the rotating biaxial coordinate system into the three-phase voltage instruction value based on the phase; three-phase/dq-axis conversion means that converts the three-phase current detected by the current detection means into a current detected value in the rotating biaxial coordinate system based on the phase; and rotation angular-frequency estimate calculation means that calculates a rotation angular-frequency estimate value being an estimate value of rotation angular frequency of the AC rotary machine based on the voltage instruction value, the current detected value, and the angular-frequency estimate value in the rotating biaxial coordinate system, wherein the angular-frequency estimate output means includes lower-limit constant value output means that outputs a lower-limit constant value, comparison means that compares an angular-frequency calculated value calculated based on the rotation angular-frequency estimate value to the lower-limit constant value, and switching means that performs switching to the angular-frequency calculated value or the lower-limit constant value, whichever is larger, according to a result of comparison by the comparison means, and outputs the larger value as the angular-frequency estimate value, and when it is assumed that primary resistance of the AC rotary machine is Rs and primary inductance of the AC rotary machine is Ls, the lower-limit constant value is set to be equal to the value Rs/Ls or more.