Control device and control method for permanent magnet motor

1. A control device for a permanent magnet motor, comprising:

a rotor position detector configured to detect a rotating speed of a rotor of a permanent magnet motor in a state in which the permanent magnet motor is disconnected from a load by a clutch and rotates without power supply;

a magnet temperature estimator configured to estimate a magnet temperature of the permanent magnet motor based on the detected rotating speed;

a current compensator configured to determine a compensation amount for compensating a current command to the permanent magnet motor based on the estimated magnet temperature; and

a drive control device configured to control a power converter for driving the permanent magnet motor based on the compensation amount,

wherein the magnet temperature estimator is configured to:

store in advance a second magnet temperature map determined as a map of second magnet temperature information indicating a relationship between an armature interlinkage magnetic flux of the permanent magnet motor and the magnet temperature of the permanent magnet motor;

calculate the armature interlinkage magnetic flux based on the rotating speed detected by the rotor position detector and an induced voltage between terminals of the permanent magnet motor detected by the power converter; and

estimate the magnet temperature of the permanent magnet motor based on the calculated armature interlinkage magnetic flux and the second magnet temperature map.

2. A control device for a permanent magnet motor according to claim 1 , wherein the current compensator is configured to:

store in advance:

a current-temperature compensation amount map indicating a relationship between the magnet temperature of the permanent magnet motor and the compensation amount for compensating the current command in the same torque;

a maximum current value of the power converter; and

a current-temperature map for start of magnet demagnetization indicating a relationship between the magnet temperature of the permanent magnet motor when the permanent magnet starts demagnetization and a maximum current when the permanent magnet is demagnetized; and

determine the compensation amount by referring to a smallest value among the value extracted from the current-temperature compensation amount map, the maximum current value of the power converter, and the value extracted from the current-temperature map for start of magnet demagnetization by using the magnet temperature estimated by the magnet temperature estimator.

3. A control device for a permanent magnet motor, comprising:

a rotor position detector configured to detect a rotating speed of a rotor of a permanent magnet motor in a state in which the permanent magnet motor is disconnected from a load by a clutch and rotates without power supply;

a magnet temperature estimator configured to estimate a magnet temperature of the permanent magnet motor based on the detected rotating speed;

a current compensator configured to determine a compensation amount for compensating a current command to the permanent magnet motor based on the estimated magnet temperature; and

a drive control device configured to control a power converter for driving the permanent magnet motor based on the compensation amount,

wherein the magnet temperature estimator is configured to:

store in advance a first magnet temperature map determined as a map of first magnet temperature information indicating a relationship among the rotating speed of the rotor, a sum of an iron loss and a mechanical loss of the rotor, and the magnet temperature of the permanent magnet motor;

calculate the sum of the iron loss and the mechanical loss based on a rotation gradient of the rotating speed detected by the rotor position detector and inertia of the rotor; and

estimate the magnet temperature of the permanent magnet motor by referring to the first magnet temperature map based on the calculated sum of the iron loss and the mechanical loss and the detected rotating speed.

4. A control device for a permanent magnet motor according to claim 3 , wherein the current compensator is configured to:

store in advance:

a current-temperature compensation amount map indicating a relationship between the magnet temperature of the permanent magnet motor and the compensation amount for compensating the current command in the same torque;

a maximum current value of the power converter; and

a current-temperature map for start of magnet demagnetization indicating a relationship between the magnet temperature of the permanent magnet motor when the permanent magnet starts demagnetization and a maximum current when the permanent magnet is demagnetized; and

determine the compensation amount by referring to a smallest value among the value extracted from the current-temperature compensation amount map, the maximum current value of the power converter, and the value extracted from the current-temperature map for start of magnet demagnetization by using the magnet temperature estimated by the magnet temperature estimator.

5. A control method for a permanent magnet motor,

the permanent magnet motor being rotatable without power supply when disconnected from a load by a clutch,

the control method comprising:

detecting rotation of the permanent magnet motor;

detecting a power supply state to the permanent magnet motor;

measuring a rotating speed of the permanent magnet motor when it is detected that the permanent magnet motor is rotating without power supply;

estimating a magnet temperature of the permanent magnet motor based on the measured rotating speed;

extracting a compensation amount for compensating a current command to the permanent magnet motor based on the estimated magnet temperature; and

controlling a power converter for driving the permanent magnet motor based on the compensation amount,

wherein the estimating the magnet temperature comprises:

storing in advance a second magnet temperature map determined as a map of second magnet temperature information indicating a relationship between an armature interlinkage magnetic flux of the permanent magnet motor and the magnet temperature of the permanent magnet motor;

calculating the armature interlinkage magnetic flux based on the rotating speed detected by the rotor position detector and a voltage between terminals of the permanent magnet motor detected by the power converter; and

estimating the magnet temperature of the permanent magnet motor based on the calculated armature interlinkage magnetic flux and the second magnet temperature map.

6. A control method for a permanent magnet motor according to claim 5 , wherein the extracting the compensation amount comprises:

storing in advance:

a current-temperature compensation amount map indicating a relationship between the magnet temperature of the permanent magnet motor and the compensation amount for compensating the current command in the same torque;

a maximum current value of the power converter; and

a current-temperature map for start of magnet demagnetization indicating a relationship between the magnet temperature of the permanent magnet motor when the permanent magnet starts demagnetization and a maximum current when the permanent magnet is demagnetized; and

determining the compensation amount by referring to a smallest value among the value extracted from the current-temperature compensation amount map, the maximum current value of the power converter, and the value extracted from the current-temperature map for start of magnet demagnetization by using the magnet temperature estimated in the estimating the magnet temperature.