Motor control device for controlling current phase on dq/three-phase coordinates

1. A motor control device for controlling a three-phase AC motor by using dq-three-phase coordinate conversion, the motor control device comprising:

a phase correction amount calculation unit for calculating a phase correction amount by using a detected motor speed and a q-axis current command initial value, which is a value obtained by dividing the torque command by the torque constant;

a rotor phase angle correction unit for adding or subtracting the phase correction amount to or from a detected rotor phase angle of the motor to calculate a corrected rotor phase angle; and

a coordinate conversion unit for performing coordinate conversion between parameters on a dq coordinate system and parameters on a three-phase coordinate system on a basis of the corrected rotor phase angle, wherein

the phase correction amount calculation unit comprises a storage unit for storing a speed coefficient N A , a first reference speed N B , a phase correction amount limit value N L , a current coefficient T A , and a reference current rate T B as predetermined parameters; a speed correction term calculation unit for calculating a speed correction term on a basis of:

Speed correction value=min[ N A ×max{0,( N−N B )}, N L ]

where N represents the motor speed;

a current correction term calculation unit for calculating a current correction term on a basis of:

Current correction value= T A ×min[1,max{0,( T r −T B }]

where T r represents an initial q-axis current command rate that is a percentage of a q-axis current command initial value with respect to a maximum current outputtable by an inverter that converts DC power into AC power to supply the AC power as a drive power for the motor; and

an output unit for outputting, as the phase correction amount, a value obtained by multiplying the speed correction term and the current correction term together.

2. The motor control device according to claim 1 , wherein the storage unit further stores a reference voltage as a predetermined parameter, and the phase correction amount calculation unit comprises a correction unit for correcting the speed coefficient, the first reference speed, and the phase correction amount limit value, respectively, read out from the storage unit, by using a DC voltage value detected on a DC side of the inverter and the reference voltage pre-stored in the storage unit.

3. The motor control device according to claim 1 , further comprising a d-axis current command initial value calculation unit for calculating a d-axis current command initial value comprising a function that uses the motor speed as an independent variable.

4. The motor control device according to claim 3 , wherein the d-axis current command initial value calculation unit calculates the d-axis current command initial value on a basis of:

Initial value of d -axis current command=max{0, IDA □( N−IDB )}

where IDA represents a predetermined d-axis current command initial value coefficient and IDB represents a predetermined second reference speed.

5. The motor control device according to claim 1 , wherein the rotor phase angle correction unit further adds or subtracts, to or from the corrected rotor phase angle, a phase angle corresponding to a time delay in a current control loop that controls so that a current that flows to the motor follows a current command, a phase angle corresponding to a phase advance of a q-axis current command necessary to maximize torque of the motor, or both of the phase angles to calculate a new corrected rotor phase angle that is used for the coordinate conversion by the coordinate conversion unit.