MOTOR DRIVE DEVICE AND CONTROL METHOD FOR MOTOR DRIVE DEVICE

• US 20200021217A1
• Filed: 09/19/2018
• Published: 01/16/2020
• Est. Priority Date: 10/11/2017
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: HANO, Masaki
• Granted Patent: US 10,848,089 B2
• Time in Patent Office: Days
• CPC Class Codes: F02D 15/02 by alteration or displacement of piston stroke
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 7/5395 by pulse-width modulation
• CPC Class Codes: H02P 21/05 specially adapted for damping motor oscillations, e.g. for reducing hunting
• CPC Class Codes: H02P 21/22 Current control, e.g. using a current control loop
• CPC Class Codes: H02P 27/12 pulsing by guiding the flux vector, current vector or voltage vector on a circle or a closed curve, e.g. for direct torque control
• CPC Class Codes: H02P 29/024 Detecting a fault condition, e.g. short circuit, locked rotor, open circuit or loss of load
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An abnormality diagnostic unit of a motor drive device has an inverter that supplies AC power to an electric motor, and a current measuring means for measuring a DC bus current of the inverter, calculates an estimated upper q-axis current limit and an estimated lower q-axis current limit based on a diagnostic q-axis voltage command value obtained by subjecting a q-axis voltage command value to an absolute value process. The abnormality diagnostic unit calculates a diagnostic q-axis current measurement based on: a q-axis current measurement calculated based on an output of the current measuring means; and sign information of the q-axis voltage command value. Then, the abnormality diagnostic unit determines whether the current measuring means is abnormal based on duration of deviation of the diagnostic q-axis current measurement from a normal range defined by the estimated upper q-axis current limit and the estimated lower q-axis current limit.

Claims

1. A motor drive device comprising:

an inverter that supplies an alternating-current power to an electric motor;

a current sensor that measures a direct-current bus current of the inverter; and

a controller that controls the inverter based on an output of the current sensor,

wherein the controller compares a q-axis current measurement calculated based on the output of the current sensor and an estimated q-axis current value estimated based on a q-axis voltage command value, and determines whether the current sensor is abnormal based on a duration of deviation that is a duration of continuous deviation of the q-axis current measurement from the estimated q-axis current value.

2. The motor drive device according to claim 1, wherein the controller compares the q-axis current measurement and the estimated q-axis current value, when a rotational speed of the electric motor is within a predetermined range including zero.

3. The motor drive device according to claim 1,

wherein the electric motor is for use as an actuator for an internal combustion engine,

wherein the estimated q-axis current value is estimated as a normal range defined by an estimated upper q-axis current limit and an estimated lower q-axis current limit, considering a variation of at least one selected from:

current measurement performed by the current sensor;

voltage measurement of the output of the current sensor;

a motor characteristic of the electric motor;

a margin of voltage drop due to dead time at switching of the inverter;

and an oil temperature or an exhaust performance of the internal combustion engine.

4. The motor drive device according to claim 1, wherein the controller integrates the duration of deviation each time the q-axis current measurement continuously deviates from the estimated q-axis current value, and determines that the current sensor is abnormal when the integrated duration of deviation, which is an integrated value of the duration of deviation, reaches a predetermined time length.

5. The motor drive device according to claim 4, wherein, when the rotational speed of the electric motor is fluctuating, the predetermined time length is set based on a fluctuation period of the rotational speed, a fluctuation amount of the rotational speed, and a fluctuation amount of an object to be driven by the electric motor.

6. The motor drive device according to claim 1, wherein the estimated q-axis current value is estimated considering a current response delay due to a motor characteristic of the electric motor in responding to application of the q-axis voltage command value.

7. The motor drive device according to claim 1,

wherein the estimated q-axis current value is estimated based on a diagnostic q-axis voltage command value obtained by converting the q-axis voltage command value into an absolute value,

wherein the q-axis current measurement is a diagnostic q-axis current measurement, a sign of which is determined based on whether the q-axis voltage command value is a positive number or a negative number.

8. A control method for a motor drive device including:

an inverter that supplies an alternating-current power to an electric motor; and

a current sensor that measures a direct-current bus current of the inverter,

the method comprising the steps of;

comparing a q-axis current measurement calculated based on an output of the current sensor and an estimated q-axis current value estimated based on a q-axis voltage command value; and

determining whether the current sensor is abnormal based on a duration of deviation that is a duration of continuous deviation of the q-axis current measurement from the estimated q-axis current value.