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EP-4496213-B1 - DIAGNOSTIC DEVICE AND PROGRAM

EP4496213B1EP 4496213 B1EP4496213 B1EP 4496213B1EP-4496213-B1

Inventors

  • KOBAYASHI, KAZUKI
  • CAO, JUNMIN
  • TAKEMURA, YUICHI

Dates

Publication Date
20260506
Application Date
20230216

Claims (9)

  1. A diagnostic device (80) applicable to a power supply system (60), the power supply system (60) comprising: a power supply (61) ; an inverter (73) connected to the power supply (61), wherein the inverter (73) is a power conversion circuit with multiple switching elements for each phase; a motor (72) connected to the inverter (73); a power switch (75) on a power supply path connecting the power supply (61) and the inverter (73); a voltage sensor (77) that detects a path voltage, the path voltage being a voltage of the power supply path on the inverter side of the power switch (75), wherein the diagnostic device (80) comprising: a shutdown command unit that is configured to output a shutdown command to shut down the power switch (75) with the control of the inverter (73) stopped when a switch diagnostic condition is satisfied in the conduction state of the power switch (75); characterized by an acquisition unit that is configured to acquire a voltage change, which is the change in the detected voltage of the voltage sensor (77) in response to the change in the number of revolutions of the motor (72) after the output of the shutdown command by the shutdown command unit; a diagnostic unit that is configured to diagnose whether the power switch (75) is in an on-failure state based on the voltage change of at least two different time points, wherein the path voltage changes in response to the change in the number of revolutions of the motor (72) when the shutdown command is output and the control of the inverter (73) is stopped, the power supply system (60) is configured to rotate a propeller (71) by the motor (72) in an aerial vehicle that flies with the rotation of the propeller (71), the diagnostic device (80) further comprises a propeller rotation control unit, that is configured, when the shutdown command is output by the shutdown command unit, to reduce the number of revolutions of the motor (72) along with the number of revolutions of the propeller (71), and the propeller rotation control unit is further configured to, after the shutdown command is output and the diagnostic unit diagnosed, when the power switch (75) is determined to be normal and there is a request to increase the number of revolutions of the propeller (71), cancel the reduction in the number of revolutions of the propeller (71).
  2. The diagnostic device (80) according to claim 1, wherein in the power supply system (60), a smoothing capacitor (76) is connected in parallel to the power supply (61) in the power supply path on the inverter side of the power switch (75), the diagnostic device (80) further comprises a discharge processing unit that is configured to discharge the smoothing capacitor (76) under the condition that a decrease in the number of revolutions occurs after the output of the shutdown command by the shutdown command unit, and the acquisition unit is configured to acquire the difference between the detected voltage before the discharging of the smoothing capacitor (76) by the discharging processing unit and the detected voltage after the discharging of the smoothing capacitor (76) as the voltage change under the situation where the number of revolutions decreases after the output of the shutdown command.
  3. The diagnostic device (80) according to claim 2, wherein the discharge processing unit is configured to discharge the smoothing capacitor (76) to make the path voltage lower than an electromotive force voltage of the motor (72) at the end of the smoothing capacitor discharge.
  4. The diagnostic device (80) according to claim 2, wherein the discharge processing unit is configured to discharge the smoothing capacitor (76) multiple times under the situation where the number of revolutions decreases after the output of the shutdown command, the acquisition unit is configured to acquire, when the smoothing capacitor (76) is discharged multiple times, the number of revolutions and the path voltage before the first discharge of the smoothing capacitor (76) and after each discharge after the first discharge, respectively, the diagnostic unit is configured to calculate an approximate straight-line, which is a linear approximation of the relationship between the number of revolutions and the path voltage, using the number of revolutions and the path voltage in three or more combinations acquired by the acquisition unit, and diagnoses the on-failure state of the power switch (75) based on the slope of the approximate straight-line and the scatter of the path voltage relative to the approximate straight-line.
  5. The diagnostic device (80) according to claim 4, wherein the acquisition unit is configured to acquire the number of revolutions and the path voltage before and after the first capacitor discharge by the discharge processing unit as first data and second data respectively, under the condition that the number of revolutions decreases after the output of the shutdown command, and then to acquire the number of revolutions and the path voltage after the second capacitor discharge as third data, the diagnostic unit is configured to, in a case that the number of revolutions of the motor (72) is higher than the predetermined value when the second data is acquired, acquire the first to third data and diagnoses the on-failure state of the power switch (75) using the first to third data, and in a case that the number of revolutions of the motor (72) is lower than the predetermined value when the second data is acquired, acquire the first data and the second data and diagnoses the on-failure state of the power switch (75) using the first data and the second data.
  6. The diagnostic device (80) according to claim 1, wherein the power supply system (60) further comprises a current sensor (28) that is configured to detect the power supply current, which is the current flowing in the power supply (61), the acquisition unit is configured to acquire the detected current of the current sensor after the output of the shutdown command by the shutdown command unit, the diagnostic unit is configured to perform a first determination process to determine whether the voltage change is greater than a predetermined voltage threshold and a second determination process to determine whether the detected current is greater than a predetermined current threshold, and when the voltage change is determined to be smaller than the voltage threshold in the first determination process and the detected current is determined to be larger than the current threshold in the second determination process, the diagnostic unit is configured to diagnose the power switch (75) is in the on-failure state.
  7. The diagnostic device (80) according to claim 1, wherein the power supply system (60) is mounted to a mobile object having a plurality of drive units, each of the drive unit comprising an inverter, a motor, a power switch, and a voltage sensor, the mobile object can move by driving some of the drive units out of all the drive units, the shutdown command unit is configured to, when some of the drive units out of a plurality of drive units in the drive state are to be stopped while the mobile object is moving, assume that the switch diagnosis condition is satisfied for the drive unit to be stopped and output the shutdown command.
  8. The diagnostic device (80) according to claim 7, further comprising a power control unit that is configured to output a power command value to the drive unit to which the shutdown command is not output, when stopping the drive of some of the drive units during the movement of the mobile object, and the shutdown command is output by the shutdown command unit for the drive unit to be stopped, the power command value is to maintain the state of movement of the mobile object.
  9. A program executed by a computer of a power supply system (60), the power supply system (60) comprising: a power supply (61) ; an inverter (73) connected to the power supply (61); a motor (72) connected to the inverter (73); a power switch (75) on a power supply path connecting the power supply (61) and the inverter (73); a voltage sensor (77) that detects a path voltage, the path voltage being a voltage of the power supply path on the inverter side of the power switch (75), wherein the program causes the computer to: output a shutdown command to shut down the power switch (75) with the control of the inverter (73) stopped when a switch diagnostic condition is satisfied in the conduction state of the power switch (75), characterized in that the program further causes the computer to: acquire a voltage change, which is the change in the detected voltage of the voltage sensor (77) in response to the change in the number of revolutions of the motor (72) after the output of the shutdown command; diagnose whether the power switch (75) is in an on-failure state based on the voltage change of at least two different time points, wherein the inverter (73) is a power conversion circuit with multiple switching elements for each phase, the path voltage changes in response to the change in the number of revolutions of the motor (72) when the shutdown command is output and the control of the inverter (73) is stopped, the power supply system (60) is configured to rotate a propeller (71) by the motor (72) in an aerial vehicle that flies with the rotation of the propeller (71), wherein the program causes the computer to: when the shutdown command is output by the shutdown command unit, reduce the number of revolutions of the motor (72) along with the number of revolutions of the propeller (71), and, after the shutdown command is output and the diagnostic unit diagnosed, when the power switch (75) is determined to be normal and there is a request to increase the number of revolutions of the propeller (71), to cancel the reduction in the number of revolutions of the propeller (71).

Description

[TECHNICAL FIELD] This disclosure relates to a diagnostic device and a program for diagnosing power switch on-failure state. [BACKGROUND ART] A conventional power supply system is known. The conventional power supply system has a power supply, an inverter, a motor, a power switch (system main relay) that connects or disconnects between the power supply and the motor in a power supply path connecting the power supply and the inverter. In addition, a device for diagnosing the welding of the power switch while the motor is rotating and driven for this power supply system is also known. For example, the device described in patent document 1 controls the inverter so that the path voltage, which is the voltage of the power supply path on the inverter side rather than the power switch, becomes the predetermined target voltage while outputting a shutdown command to shut down the power switch when a power failure is detected., the device diagnoses the welding of the power switch based on whether the path voltage becomes the target voltage. [PRIOR ART REFERENCES] [PATENT DOCUMENT] [Patent Document 1] JP2009-183134A Document US 2011 / 221374 A1 discloses a discharging control device for an electric power conversion system, which is mounted on a motor vehicle. The discharge control device turns off a relay in order to instruct an electric power conversion circuit to supply a reactive current into a motor generator, and thereby to decrease a capacitor voltage to a diagnostic voltage. After this process, the discharge control device outputs an emergency discharging instruction signal in order to turn on both power switching elements at high voltage side and a low voltage side in the electric power conversion circuit. This makes a short circuit between the electrodes of the capacitor in order to discharge the capacitor, and executes a discharging control to detect whether or not an emergency discharging control is correctly executed and completed. The discharge control device detects whether or not the electric power stored in the capacitor is discharged on the basis of the voltage of a voltage sensor. Document JP 2006 280070 A discloses a control method and a controller of a motor. In the controller of a motor comprising a relay for interrupting power supply, a switching circuit of the relay for interrupting power supply, a preliminary charging circuit and a relay for switching the preliminary charging circuit, a switching circuit of the relay for switching the preliminary charging circuit, a capacitor for smoothing a power supply, and an inverter circuit for controlling the motor, if a voltage not lower than some threshold V1 is remaining in the capacitor for smoothing the power supply when both switching circuits for turning the relay for interrupting power supply and the relay for switching the preliminary charging circuit off are operating, charges remaining in the capacitor for smoothing the power supply are conducted to the motor through the inverter circuit for controlling the motor and discharged. If the voltage difference before and after discharge is not higher than a threshold V2, a decision is made that the relay for interrupting power supply is deposited. Document US 2013/106423 A1 discloses a main relay monitoring system and method for a green vehicle, where a main relay is installed between a high voltage battery and an inverter in order to diagnose whether the main relay, which controls the output of the high voltage battery, is fused. In particular a switching operation of an inverter is stopped when an ignition off is detected, and a main relay is turned off and a voltage output of a main battery is cut. Then, a voltage charged at a DC link capacitor is forcibly discharged once the main relay is completely turned off. A voltage of the main battery is then compared to an input voltage of the inverter, and a determination is made based off of this comparison whether the main relay is fused. [SUMMARY OF INVENTION] When the motor is rotating, a back EMF is generated in proportion to the rotation speed of the motor. Therefore, to bring the path voltage near the target voltage by controlling the inverter, it is necessary to control the inverter to cancel the back EMF of the motor. As a result, configuration of the device and control procedure of the inverter become more complicated. Therefore, a technology that can properly diagnose an on-failure state of the power switch without changing the path voltage by inverter control is desired. The present disclosure was made to solve the above problem, the purpose of which is to provide a diagnostic device and program that can properly diagnose an on-failure state of a power switch. This object is solved by a diagnostic device as set out in claim 1 as well as by a program as set out in claim 9. Advantageous developments are defined in the dependent claims. The first means to solve the above problem applies to a diagnostic device applicable to a power supply system,