Power conversion device and control method

Patent metadata

Field	Value
Publication number	US-2024396483-A1
Application number	US-202418672013-A
Country	US
Kind code	A1
Filing date	May 23, 2024
Priority date	May 26, 2023
Publication date	Nov 28, 2024
Grant date	—

Abstract

A power conversion device includes: power conversion circuitry configured to supply drive power to an induction motor; and control circuitry configured to: generate a torque command; correct the torque command, in response to determining that a magnitude of a primary frequency of the induction motor is less than a lower limit level, so that the magnitude of the primary frequency approaches the lower limit level; and control the power conversion circuitry to supply the drive power so that the induction motor generates a torque corresponding to the torque command.

First claim

What is claimed is:

1 . A power conversion device comprising:
power conversion circuitry configured to supply drive power to an induction motor; and control circuitry configured to:
generate a torque command;
correct the torque command, in response to determining that a magnitude of a primary frequency of the induction motor is less than a lower limit level, so that the magnitude of the primary frequency approaches the lower limit level; and
control the power conversion circuitry to supply the drive power so that the induction motor generates a torque corresponding to the torque command.

2 . The power conversion device according to claim 1 , wherein the control circuitry is configured to correct the torque command to accelerate a rotor of the induction motor in a present rotating direction so that the primary frequency approaches the lower limit level.

3 . The power conversion device according to claim 1 , wherein the control circuitry is further configured to:
determine the lower limit level based on a lower limit profile and the torque command before correction, the lower limit profile being defined in advance to represent a relationship between the torque command and the lower limit level; and correct the torque command based on the determined lower limit level.

4 . The power conversion device according to claim 3 , wherein the lower limit profile is defined such that the lower limit level increases as the torque command increases.

5 . The power conversion device according to claim 4 , wherein the lower limit profile is defined so as to limit the lower limit level to be less than or equal to a predetermined limit value.

6 . The power conversion device according to claim 1 , wherein the control circuitry is configured to:
integrate a deviation between a target rotational speed and a rotational speed of a rotor of the induction motor; generate the torque command so as to reduce a result of integrating the deviation; and stop integrating the deviation in response to determining that the torque command is corrected based on the lower limit level.

7 . The power conversion device according to claim 1 , wherein the control circuitry is further configured to selectively execute a first mode of operation or a second mode of operation,
wherein the first mode of operation comprises:
generating the torque command;
correcting the torque command, in response to determining that the magnitude of the primary frequency of the induction motor is less than the lower limit level, so that the magnitude of the primary frequency approaches the lower limit level; and
controlling the power conversion circuitry so that the induction motor generates the torque corresponding to the torque command, and
wherein the second mode of operation comprises:
determining, in response to determining that the magnitude of the primary frequency approaches zero, a target frequency having an inverse sign to a sign of the primary frequency;
correcting a magnetic flux command to reduce a deviation between the target frequency and the primary frequency; and
controlling the power conversion circuitry so that the induction motor generates a secondary magnetic flux corresponding to the magnetic flux command.

8 . The power conversion device according to claim 7 , wherein said determining the target frequency includes determining, in response to determining that the magnitude of the primary frequency decreases to a first lower limit level, the target frequency greater than the first lower limit level.

9 . The power conversion device according to claim 8 , wherein said determining the target frequency includes:
determining, in response to determining that the magnitude of the primary frequency according to the magnetic flux command before correction decreases to a second lower limit level greater than the first lower limit level, the target frequency having the same sign as the sign of the primary frequency and the same magnitude as the magnitude of the second lower limit level; and inverting the sign of the target frequency, in response to determining that the magnitude of the primary frequency according to the corrected magnetic flux command decreases to the first lower limit level.

10 . The power conversion device according to claim 7 , wherein the second mode of operation further comprises controlling the power conversion circuitry so as to reduce a change in the torque caused by correcting the magnetic flux command.

11 . The power conversion device according to claim 7 , wherein the control circuitry is configured to select the first mode of operation or the second mode of operations based on a user setting.

12 . The power conversion device according to claim 7 , wherein the control circuitry is configured to select the first mode of operation or the second mode of operation based on whether there is a constraint condition for a rotational speed of a rotor of the induction motor.

13 . The power conversion device according to claim 7 , wherein the second mode of operation further comprises controlling the power conversion circuitry so that the induction motor generates the torque corresponding to the torque command based on a model of the induction motor including a primary resistance of the induction motor, and
wherein the control circuitry is further configured to:
calculate a standard value of the torque based on a relationship among the secondary magnetic flux, a rotation speed, and the torque, the relationship being under a condition where the primary frequency is zero; and
correct the primary resistance in the model, in response to determining that a deviation between the torque command and the standard value of the torque is greater than a predetermined level, to reduce the deviation.

14 . The power conversion device according to claim 13 , wherein the control circuitry is further configured to select the first mode of operation in response to determining that the primary resistance is corrected.

15 . A power conversion device comprising:
power conversion circuitry configured to supply drive power to an induction motor; one or more processing devices; and one or more memory devices including computer program code configured to cause the one or more processing devices to:
determine, in response to determining that a magnitude of a primary frequency of the induction motor approaches zero, a target frequency having an inverse sign to a sign of the primary frequency;
correct a magnetic flux command so as to reduce a deviation between the target frequency and the primary frequency; and
control the power conversion circuitry so that the induction motor generates a secondary magnetic flux corresponding to the magnetic flux command.

16 . The power conversion device according to claim 15 , wherein the computer program code is configured to cause the one or more processing devices to determine, in response to determining that a magnitude of the primary frequency decreases to a first lower limit level, the target frequency greater than the first lower limit level.

17 . The power conversion device according to claim 16 , wherein the computer program code is configured to cause the one or more processing devices to:
determine, in response to determining that the magnitude of the primary frequency according to the magnetic flux command before correction decreases to a second lower limit level greater than the first lower limit level, the target frequency having the same sign as the sign of the primary frequency and the same magnitude as the magnitude of t

Assignees

• Yaskawa Electric Corp

Inventors

• Takase Yoshiyasu
• Yamazaki Akira
• Hamabe Yasumasa
• Saeki Takahiro

Classifications

• H02P21/13

  Observer control, e.g. using Luenberger observers or Kalman filters · CPC title

• H02P21/14 Primary

  Estimation or adaptation of machine parameters, e.g. flux, current or voltage · CPC title

• H02P23/30 Primary

  Direct torque control [DTC] or field acceleration method [FAM] · CPC title

• H02P21/18

  Estimation of position or speed · CPC title

• H02P21/0017

  Model reference adaptation, e.g. MRAS or MRAC, useful for control or parameter estimation · CPC title