Control device for alternating current motor

Patent metadata

Field	Value
Publication number	US-10594240-B2
Application number	US-201916254281-A
Country	US
Kind code	B2
Filing date	Jan 22, 2019
Priority date	Jan 23, 2018
Publication date	Mar 17, 2020
Grant date	Mar 17, 2020

Abstract

In a MG control device, a standard voltage calculation part calculates a d axis standard voltage and a q axis standard voltage in a standard state in which no demagnetization occurs in permanent magnets of a MG. A magnetic flux change amount estimation value calculation part calculates a basic magnetic flux change amount estimation value based on a deviation of a specific value from the q-axis standard voltage. This specific value is obtained by multiplying q axis real voltage with a ratio of the d axis standard voltage and the d axis real voltage. A magnetic flux change amount estimation value correction part adjusts a magnetic flux change amount estimation value by correcting the basic magnetic flux change amount estimation value relatively to a detection threshold value based on characteristic change of the MG in a demagnetization state of the permanent magnets of the MG.

First claim

What is claimed is:

1. A control device for alternating current motors configured to perform a power supply control of an alternating current motor comprising permanent magnets, the control device comprising a computer system including a central processing unit, the computer system being configured to provide:
a voltage instruction calculation part calculating voltage instruction values on the basis of an output torque instruction to be supplied to the alternating current motor;
an electric power conversion unit converting a direct current power to an alternating current power on the basis of the voltage instruction values, and supplying the alternating current power to the alternating current motor;
a magnetic flux change amount estimation part calculating a magnetic flux change amount estimation value which is a deviation of a real magnetic flux amount of the permanent magnets of the alternating current motor from a standard magnetic flux amount, where the standard magnetic flux amount of the permanent magnets is an amount when no demagnetization has occurred in the permanent magnets; and
a demagnetization detection part detecting occurrence of demagnetization of the permanent magnets when the magnetic flux change amount estimation value calculated by the magnetic flux change amount estimation part is lower than a detection threshold value, wherein
the magnetic flux change amount estimation part comprises:
a real voltage estimation part estimating a d axis real voltage and a q axis real voltage to be supplied to the alternating current motor, or obtaining voltage detection values as the d axis real voltage and the q axis real voltage, correlated with the voltage instruction values;
a standard voltage calculation part calculating a d axis standard voltage and a q axis standard voltage to be supplied to the alternating current motor in a standard state of the alternating current motor on the basis of an electrical angular speed and a current of the alternating current motor;
a magnetic flux change amount estimation value calculation part calculating a basic magnetic flux change amount estimation value on the basis of a deviation of a specific value from the q axis standard voltage, where the specific value is obtained by multiplying a q axis real voltage with a ratio of the d axis standard voltage and the d axis real voltage; and
a magnetic flux change amount estimation value correction part calculating the magnetic flux change amount estimation value by correcting the basic magnetic flux change amount estimation value relatively to the detection threshold value on the basis of characteristic change of the alternating current motor in a demagnetization state of the permanent magnets of the alternating current motor.

2. The control device for alternating current motors according to claim 1 , wherein
the magnetic flux change amount estimation value correction part calculates a correction value which corresponds to the characteristic change of the alternating current motor in the demagnetization state of the permanent magnets of the alternating current motor, corrects the basic magnetic flux change amount estimation value on the basis of the correction value, and transmits, to the demagnetization detection part, the corrected basic magnetic flux change amount estimation value as the magnetic flux change amount estimation value,
wherein
the magnetic flux change amount estimation value correction part comprises a first correction map part, a second correction map part, a map switching part and a correction calculation part,
the first correction map part generates a first correction map value as the correction value, with which the basic magnetic flux change amount estimation value is corrected so that the d axis real voltage becomes equal to the d axis standard voltage on the basis of one of an output torque, a current and an electrical angular speed of the alternating current motor based on characteristics of the alternating current motor in the standard state in which no demagnetization occurs in the permanent magnets of the alternating current motor,
the second correction map part generates a second correction map value as the correction value, with which the basic magnetic flux change amount estimation value is corrected so that the d axis real voltage becomes equal to the d axis standard voltage on the basis of one of the output torque, the current and the electrical angular speed of the alternating current motor based on characteristics of the alternating current motor in a transition state when the alternating current motor transits from the standard state to an irreversible demagnetization state,
the map switching part compares a map switching threshold value, which is a negative value which is more than the detection threshold value, with the basic magnetic flux change amount estimation value, and selects the first correction map value when the basic magnetic flux change amount estimation value ΔΦ_b is more than the map switching threshold value, and selects the second correction map value when the basic magnetic flux change amount estimation value ΔΦ_b is not more than the map switching threshold value, and
the correction calculation part corrects the basic magnetic flux change amount estimation value ΔΦ_b by using one of the first correction map value and the second correction map value selected by the map switching part, and transmits the corrected basic magnetic flux change amount estimation value as the magnetic flux change amount estimation value to the demagnetization detection part.

3. The control device for alternating current motors according to claim 1 , wherein
the detection threshold value is adjusted on the basis of the one of the output torque, the current and the electrical angular speed of the alternating current motor.

4. A control method of performing a power supply control of an alternating current motor comprising permanent magnets, comprising steps of:
calculating voltage instruction values on the basis of an output torque instruction to be supplied to the alternating current motor;
converting a direct current power to an alternating current power on the basis of the voltage instruction values, and supplying the alternating current power to the alternating current motor;
calculating a magnetic flux change amount estimation value which is a deviation of a real magnetic flux amount of the permanent magnets of the alternating current motor from a standard magnetic flux amount, where the standard magnetic flux amount of the permanent magnets is an amount when no demagnetization has occurred in the permanent magnets; and
detecting occurrence of demagnetization of the permanent magnets when the magnetic flux change amount estimation value is lower than a detection threshold value,
wherein
the estimation of the magnetic flux change amount of the permanent magnets of the alternating current motor comprises steps of:
estimating a d axis real voltage and a q axis real voltage to be supplied to the alternating current motor, or obtaining voltage detection values as the d axis real voltage and the q axis real voltage, correlated with the voltage instruction values;
calculating a d axis standard voltage and a q axis standard voltage to be supplied to the alternating current motor in a standard state of the alternating current motor on the basis of an electrical angular speed and a current of the alternating current motor;
calculating a basic magnetic flux change amount estimation value on the basis of a deviation of a specific value from the q axis standard voltage, where the specific value is obtained by multiplying a q axis real voltage with a ratio of the d axis standard voltage and the d axis real voltage; and
calculating the magnetic flux change amount estimation value by correcting the basic magnetic

Assignees

• Denso Corp

Inventors

• Ogawa Takashi
• Nishiyama Masaki
• Matsuno Mitsuharu

Classifications

• H02P29/02

  Providing protection against overload without automatic interruption of supply (protection against faults of stepper motors H02P8/36) · CPC title

• H02P21/10 Primary

  Direct field-oriented control; Rotor flux feed-back control · CPC title

• H02P21/141 Primary

  Flux estimation · CPC title