Power conversion device and power conversion system

Abstract

To provide a power conversion device and a power conversion system capable of properly managing the braking strength against motor rotation.SOLUTION: A control device performs inverter control processing with an inverter as a control target. In the inverter control process, a duty ratio D is set according to a motor speed Nm in step S104 when an inverter abnormality occurs. In step S105, an intermittent ASC is performed according to the duty ratio D. In the intermittent ASC, the inverter is intermittently and repeatedly shifted to an ASC state and an all-off state. The ASC state of the inverter is a state in which one of upper and lower arm switches is driven on for all three phases and the other is driven off for all three phases. The all-off state is a state in which all arm switches of the inverter are driven off.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] TECHNICAL FIELD The disclosure herein relates to power conversion devices and systems. [Background technology]

[0002] Patent Document 1 discloses a vehicle equipped with an inverter that converts DC power into AC power and supplies it to a three-phase motor, and a control device that controls the inverter. The inverter has arm circuits provided for each of the three phases. In these arm circuits, the switching elements on the power supply line side and the switching elements on the earth line side are connected in series with each other. The switching elements on the power supply line side in each arm circuit are connected in parallel with each other, and the switching elements on the earth line side in each arm circuit are connected in parallel with each other.

[0003] The control device performs three-phase ON control when a short circuit occurs in a switching element of the inverter. The three-phase ON control is a process of turning on all switching elements connected in parallel to the short-circuited switching element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-195026 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the above-mentioned Patent Document 1, when the control device performs three-phase ON control, the current flowing through the motor is likely to generate a braking torque that brakes the rotation of the motor. Therefore, if the current flowing through the motor is relatively large, there is a concern that the braking torque will become too large and the braking of the motor rotation will become too strong. For example, it is thought that increasing the output of the motor will increase the current flowing through the motor, making it easier for the braking of the motor rotation to become strong.

[0006] A main object of the present disclosure is to provide a power conversion device and a power conversion system that can appropriately manage the strength of braking applied to the rotation of a motor. [Means for solving the problem]

[0007] The various aspects disclosed in this specification employ different technical means to achieve their respective objectives. The reference symbols in parentheses in the claims and in this section are merely examples showing the corresponding relationship with the specific means described in the embodiments described below as one aspect, and do not limit the technical scope.

[0008] In order to achieve the above object, one disclosed embodiment comprises: A power conversion device (13) that converts electric power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), In the power conversion unit, when one of the upper arm switch (32a) on the high potential side and the lower arm switch (32b) on the low potential side of all of the multiple arm circuits (31) connected in parallel to each other is turned on and the other is turned off, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether or not an abnormality has occurred in a power conversion unit; When the abnormality determination unit determines that an abnormality has occurred, the power conversion unit is intermittently and repeatedly shifted to a one-side on state. The power converter outputs a command to A one-side ON interruption unit (S105) that performs an interruption process; a duty setting unit (S104) that variably sets a ratio of a time during which the power conversion unit is in a half-on state per unit time as a duty ratio (D); Equipped with 、 The half-on intermittent part performs intermittent processing according to the duty ratio, The duty setting unit sets the duty ratio to a smaller value as the motor rotation speed (Nm) becomes smaller. It is a power conversion device. One disclosed embodiment is A power conversion device (13) that converts electric power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), In the power conversion unit, when one of the upper arm switch (32a) on the high potential side and the lower arm switch (32b) on the low potential side of all of the multiple arm circuits (31) connected in parallel to each other is turned on and the other is turned off, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether or not an abnormality has occurred in a power conversion unit; a one-side ON interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly switch the power conversion unit to a one-side ON state when the abnormality determination unit determines that an abnormality has occurred; Equipped with The half-on intermittent unit is a power conversion device that, as an intermittent process, intermittently repeats a half-on state at a period corresponding to the carrier period (P) of the carrier wave. One disclosed embodiment is A power conversion device (13) that converts electric power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), In the power conversion unit, when one of the upper arm switch (32a) on the high potential side and the lower arm switch (32b) on the low potential side of all of the multiple arm circuits (31) connected in parallel to each other is turned on and the other is turned off, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether or not an abnormality has occurred in a power conversion unit; a single-on interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly transition the power conversion unit to a single-on state when the abnormality determination unit determines that an abnormality has occurred and the motor rotation speed (Nm) is equal to or lower than a predetermined interruption threshold value (N1); a one-on holding unit (S106) that transitions the power conversion unit to a one-on state and holds the state when the abnormality determination unit determines that an abnormality has occurred and the rotation speed is not equal to or less than an intermittence threshold; The power conversion device is provided with: One disclosed embodiment is A power conversion device (13) that converts electric power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), In the power conversion unit, when one of the upper arm switch (32a) on the high potential side and the lower arm switch (32b) on the low potential side of all of the multiple arm circuits (31) connected in parallel to each other is turned on and the other is turned off, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether or not an abnormality has occurred in a power conversion unit; a one-side ON interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly switch the power conversion unit to a one-side ON state when the abnormality determination unit determines that an abnormality has occurred; an all-off unit (S202, S303, S402, S404) that switches the power conversion unit to an all-off state in which both the upper arm switches and the lower arm switches are turned off for all of the multiple arm circuits when the abnormality determination unit determines that an abnormality has occurred, according to the rotation speed; Equipped with All off parts are The power conversion device is provided with a small side off section (S202, S402) that performs full off when the rotation speed is equal to or less than a small side threshold (N2) that is smaller than the intermittent threshold. One disclosed embodiment is A power conversion device (13) that converts electric power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), In the power conversion unit, when one of the upper arm switch (32a) on the high potential side and the lower arm switch (32b) on the low potential side of all of the multiple arm circuits (31) connected in parallel to each other is turned on and the other is turned off, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether or not an abnormality has occurred in a power conversion unit; a one-side ON interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly switch the power conversion unit to a one-side ON state when the abnormality determination unit determines that an abnormality has occurred; an all-off unit (S202, S303, S402, S404) that switches the power conversion unit to an all-off state in which both the upper arm switches and the lower arm switches are turned off for all of the multiple arm circuits when the abnormality determination unit determines that an abnormality has occurred, according to the rotation speed; Equipped with All off parts are The power conversion device is provided with a large side off unit (S303, S404) that performs full off when the rotation speed is equal to or less than a large side threshold (N3) that is larger than the intermittent threshold.

[0009] Through testing and other efforts, it has been discovered that when a power conversion device has a power conversion unit that repeatedly transitions to a single-on state, the braking torque generated by the motor is more likely to be reduced than when the power conversion unit is maintained in a single-on state.

[0010] In response to this finding, according to the first aspect, when an abnormality occurs in the power conversion unit, an intermittent process is performed to repeatedly switch the power conversion unit to a one-side on state. In this case, the braking torque generated in the motor is easily reduced, so that it is possible to prevent the braking force applied to the motor rotation from becoming too strong. Therefore, when an abnormality occurs in the power conversion unit, it is possible to appropriately manage the strength of the braking force applied to the motor rotation.

[0011] One disclosed embodiment is A power conversion system (50) for converting power supplied from a power source unit (11) to a plurality of motors (12) from direct current to alternating current for each motor by a plurality of power conversion units (30, 301, 302), In the power conversion unit, when one of the upper arm switch (32a) on the high potential side and the lower arm switch (32b) on the low potential side of all of the multiple arm circuits (31) connected in parallel to each other is turned on and the other is turned off, this is referred to as a one-on state. An abnormality determination unit (S501) that determines whether or not an abnormality has occurred for each of the plurality of power conversion units; an order setting unit (S506) that, when it is determined by the abnormality determination unit that an abnormality has occurred in at least one power conversion unit, sets an order in which at least two target conversion units (301, 302) are to be shifted to a one-on state, with at least two power conversion units including the power conversion unit determined to have an abnormality as the at least two target conversion units; a target interruption unit (S507) that performs an interruption process for repeatedly switching the power conversion units to a single-on state intermittently on at least two target conversion units in parallel by repeatedly switching at least two target conversion units to a single-on state in an order set by the order setting unit; The power conversion system includes:

[0012] According to the above aspect, when an abnormality occurs in a power conversion unit, intermittent processing is performed on at least two target conversion units including the power conversion unit in which the abnormality occurs. Therefore, for each of these target conversion units, the strength of the braking force applied to the rotation of the motor can be appropriately managed, as in the first aspect. Note that the motor to which power is supplied from the target conversion unit is called the target motor.

[0013] Unlike the above embodiment, for example, a configuration is assumed in which the intermittent processing is performed separately for at least two target conversion units, not in parallel. In this configuration, at least two target motors include a motor in a state where the strength of braking for rotation is managed by the intermittent processing, and a motor in a state where the strength of braking is not managed by the intermittent processing. For this reason, there is a concern that the rotation balance of at least two target motors will be poor.

[0014] In contrast, according to the above aspect, the intermittent processing is performed in parallel for at least two target conversion units. Therefore, for each of the at least two target motors, the strength of the braking for the rotation of the target motor can be managed in parallel by the intermittent processing. Therefore, the rotation balance of the at least two target motors can be improved.

[0015] In addition, when the intermittent process is performed on the target conversion unit, the braking torque of the target motor is likely to increase or decrease according to the repetition of the one-on state due to the target conversion unit intermittently and repeatedly transitioning to the one-on state. In other words, the target motor is likely to generate torque ripple. Unlike the above-mentioned embodiment, for example, in a configuration in which at least two target conversion units simultaneously transition to the one-on state, there is a concern that the torque ripple generated in each of the at least two target motors will be synchronously amplified.

[0016] In contrast, according to the above embodiment, when the intermittent processing for at least two target conversion units is performed in parallel, these target conversion units are switched to a one-on state in sequence. In this configuration, even if torque ripple occurs in each of the at least two target motors, these torque ripples are unlikely to be synchronized. Therefore, after improving the rotation balance of the at least two target motors, the torque ripples generated in each of these target motors can be managed comprehensively. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a diagram showing the configuration of a drive system according to the first embodiment. [Diagram 2] FIG. 2 is a block diagram showing the electrical configuration of a control device. [Diagram 3] FIG. 13 is a diagram showing a change in braking torque when an inverter abnormality occurs. [Figure 4] 4 is a flowchart showing a procedure of an inverter control process. [Diagram 5] FIG. 4 is a diagram showing the relationship between a carrier wave and a duty ratio. [Figure 6] 10 is a flowchart showing a procedure of an inverter control process in a second embodiment. [Figure 7] FIG. 13 is a diagram showing a change in braking torque when an inverter abnormality occurs. [Figure 8] 10 is a flowchart showing a procedure of an inverter control process in a third embodiment. [Figure 9] FIG. 13 is a diagram showing a change in braking torque when an inverter abnormality occurs. [Figure 10] 13 is a flowchart showing a procedure of an inverter control process in a fourth embodiment. [Figure 11] FIG. 13 is a diagram showing the configuration of a drive system according to a fifth embodiment. [Figure 12] 4 is a flowchart showing a procedure of an inverter control process. [Figure 13] FIG. 13 is a diagram showing the state of a target inverter when an inverter abnormality occurs. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Hereinafter, a number of embodiments for carrying out the present disclosure will be described with reference to the drawings. In each embodiment, the same reference numerals may be used to designate parts corresponding to matters described in the preceding embodiment, and duplicated descriptions may be omitted. In each embodiment, when only a part of the configuration is described, other embodiments described previously may be applied to other parts of the configuration. In addition to combinations of parts that are specifically indicated as being possible in each embodiment, it is also possible to partially combine embodiments even if not indicated, as long as there is no particular problem with the combination.

[0019] First Embodiment 1 is mounted on a vehicle such as an electric vehicle (EV), a hybrid vehicle (HV), a fuel cell vehicle, etc. The drive system 10 has a battery 11, a motor 12, and a power conversion device 13. The drive system 10 is a system that drives the motor 12 to drive the drive wheels of the vehicle.

[0020] The battery 11 is a DC voltage source constituted by a chargeable and dischargeable secondary battery, and corresponds to a power supply unit that supplies power to the motor 12 via the power conversion device 13. The secondary battery is, for example, a lithium ion battery or a nickel metal hydride battery. The battery 11 supplies a high voltage (for example, several hundreds of volts) to the inverter 30.

[0021] The motor 12 is a multi-phase AC motor, for example a three-phase AC rotating electric machine. The motor 12 has three phases: U-phase, V-phase, and W-phase. The motor 12 functions as an electric motor that is a driving source for running the vehicle. The motor 12 functions as a generator during regeneration. The motor 12 has windings 12a that form an armature, and permanent magnets that form a field magnet. In this motor 12, a rotor is formed including the permanent magnets, and a stator is formed including the windings 12a. The motor 12, which is a three-phase motor, has three-phase windings 12a. The motor 12 is sometimes called a motor generator or an electric motor.

[0022] 1 performs power conversion between a battery 11 and a motor 12. The power conversion device 13 includes a smoothing capacitor 21, an inverter 30, and a control device 40.

[0023] The smoothing capacitor 21 smoothes the DC voltage supplied from the battery 11. The smoothing capacitor 21 is connected to a P line 25, which is a high-potential power line, and an N line 26, which is a low-potential power line. The P line 25 is connected to the positive electrode of the battery 11, and the N line 26 is connected to the negative electrode of the battery 11. The positive electrode of the smoothing capacitor 21 is connected to the P line 25 between the battery 11 and the inverter 30. The negative electrode of the smoothing capacitor 21 is connected to the N line 26 between the battery 11 and the inverter 30. The smoothing capacitor 21 is connected in parallel to the battery 11. In the power conversion device 13, the P line 25 and the N line 26 are formed by bus bars or the like.

[0024] In the power conversion device 13, a switch 22 is provided between the battery 11 and the smoothing capacitor 21. The switch 22 connects the battery 11 and the inverter 30 so that electricity can be conducted between them. The switch 22 is a system main relay, and is provided on at least one of the P line 25 and the N line 26. When the switch 22 is in a closed state, power is supplied from the battery 11 to the inverter 30 and the motor 12. When the switch 22 is in an open state, the power supply from the battery 11 to the inverter 30 and the motor 12 is cut off.

[0025] The inverter 30 performs power conversion to convert the power supplied from the battery 11 to the motor 12 from DC to AC. The inverter 30 is a three-phase inverter, and performs power conversion for each of the three phases. The inverter 30 corresponds to a power conversion unit. The inverter 30 converts DC voltage to AC voltage in response to switching control by the control device 40, and outputs the voltage to the motor 12. The motor 12 operates to generate a predetermined rotational torque in response to the AC voltage from the inverter 30. During regenerative braking of the vehicle, the inverter 30 converts the AC voltage generated by the motor 12 upon receiving rotational force from the drive wheels into DC voltage in response to switching control by the control device 40, and outputs the voltage to the battery 11. The inverter 30 performs bidirectional power conversion between the battery 11 and the motor 12.

[0026] The inverter 30 is a DC-AC conversion circuit. The inverter 30 is configured to include arm circuits 31 for three phases. The arm circuits 31 are sometimes referred to as legs. Each arm circuit 31 has an upper arm 31a and a lower arm 31b. The upper arm 31a and the lower arm 31b are connected in series between the P line 25 and the N line 26, with the upper arm 31a on the P line 25 side. A connection point between the upper arm 31a and the lower arm 31b is connected to a winding of a corresponding phase in the motor 12 via an output line 27. The arm circuits 31 and the output line 27 are provided for each of the U phase, V phase, and W phase of the motor 12. The inverter 30 has three upper arms 31a and three lower arms 31b.

[0027] The arms 31a and 31b have arm switches 32a and 32b and diodes 33a and 33b. The upper arm 31a has one upper arm switch 32a and one upper diode 33a. The lower arm 31b has one lower arm switch 32b and one lower diode 33b.

[0028] The arm switches 32a and 32b are formed of switching elements such as semiconductor elements. The switching elements are transistors having gates, and are formed of, for example, IGBTs or MOSFETs. In this embodiment, the arm switches 32a and 32b are formed of, for example, n-channel IGBTs. The diodes 33a and 33b are reflux diodes, and are connected in inverse parallel to the arm switches 32a and 32b.

[0029] In the upper arm 31a, the collector of the upper arm switch 32a is connected to the P line 25. In the lower arm 31b, the emitter of the lower arm switch 32b is connected to the N line 26. The emitter of the upper arm switch 32a and the collector of the lower arm switch 32b are connected to each other. The anodes of the diodes 33a and 33b are connected to the emitters of the corresponding arm switches 32a and 32b, and the cathodes are connected to the collectors.

[0030] The control device 40 is, for example, an ECU, and controls the driving of the inverter 30. ECU is an abbreviation for Electronic Control Unit. The control device 40 is mainly composed of, for example, a microcomputer (hereinafter, referred to as a microcomputer) equipped with a processor, a memory, an I / O, and a bus connecting these. The control device 40 executes various processes related to the driving of the inverter 30 by executing a control program stored in the memory. The memory referred to here is a non-transitory tangible storage medium that non-temporarily stores programs and data that can be read by a computer. The non-transitory tangible storage medium is realized by a semiconductor memory, a magnetic disk, or the like.

[0031] The control device 40 generates a drive command using a signal input from a higher-level ECU such as an integrated ECU mounted on the vehicle and signals input from various sensors such as the rotation sensor 29. The control device 40 then causes the arm switches 32a, 32b to perform on-drive or off-drive in response to the drive command. The arm switches 32a, 32b can transition between an on state and an off state, transitioning to the on state in response to on-drive and transitioning to the off state in response to off-drive. For the arm switches 32a, 32b, the on state corresponds to a closed state, and the off state corresponds to an open state.

[0032] A current sensor 28 and a rotation sensor 29 are electrically connected to the control device 40 as various sensors. These sensors 28 and 29 are included in the drive system 10. Of these sensors 28 and 29, the current sensor 28 is included in the power conversion device 13.

[0033] Current sensor 28 is a current detection unit that detects the current flowing through motor 12. Current sensor 28 outputs a detection signal corresponding to the current flowing through each of the three-phase windings 12a to control device 40. Current sensor 28 is provided, for example, for at least one of output lines 27. Current sensor 28 detects the current flowing through winding 12a by detecting the current flowing through output line 27. Current sensor 28 discretely samples the current flowing through winding 12a at a predetermined sampling period, and outputs a discrete signal as a detection signal. The current flowing through winding 12a is sometimes referred to as an armature current.

[0034] The rotation sensor 29 is provided in the motor 12 and is a rotation detection unit that detects the rotation speed of the motor 12. The rotation sensor 29 outputs a detection signal corresponding to the rotation speed of the motor 12 to the control device 40. The rotation sensor 29 is configured to include, for example, an encoder, a resolver, etc.

[0035] The control device 40 shown in Fig. 2 performs vector control of the motor 12 via the inverter 30. In vector control, a three-phase AC coordinate represented by the U-phase, V-phase, and W-phase is converted into a dq coordinate represented by the d-axis and q-axis. The dq coordinate is a rotational coordinate defined by the d-axis and the q-axis, for example, where the direction from the south pole to the north pole of the rotor is the d-axis and the direction perpendicular to the d-axis is the q-axis.

[0036] The control device 40 has, as functional blocks, a current command unit 41, a three-phase to two-phase conversion unit 42, a d-axis subtraction unit 43, a q-axis subtraction unit 44, a current control unit 45, and a two-phase to three-phase conversion unit 46. These functional blocks may be configured as hardware using at least one IC or the like, or may be executed by a combination of software execution by a processor and hardware.

[0037] The three-phase to two-phase conversion unit 42 receives the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw detected by the current sensor 28. These phase currents Iu, Iv, and Iw are detection values ​​of currents that actually flow through the windings 12a of each phase in the motor 12. The control device 40 has a current acquisition unit that acquires the phase currents Iu, Iv, and Iw using the detection signal from the current sensor 28. This current acquisition unit may be included in the three-phase to two-phase conversion unit 42.

[0038] The motor rotation speed Nm detected by the rotation sensor 29 is input to the three-phase to two-phase conversion unit 42. This motor rotation speed Nm is a detected value indicating the actual rotation speed of the motor 12. The motor rotation speed Nm is, for example, the number of rotations of the motor 12 per unit time, and is a value indicating the rotation speed.

[0039] The three-phase to two-phase conversion unit 42 converts the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw of the three-phase AC coordinate system into a dq coordinate to calculate a d-axis current Id and a q-axis current Iq of the dq coordinate system. The d-axis current Id is a component in the d-axis direction in the dq coordinate, and the q-axis current Iq is a component in the q-axis direction in the dq coordinate. The three-phase to two-phase conversion unit 42 calculates the d-axis current Id and the q-axis current Iq using the motor rotation speed Nm in addition to the phase currents Iu, Iv, and Iw. For example, the three-phase to two-phase conversion unit 42 converts the phase currents Iu, Iv, and Iw into the dq coordinate based on the motor rotation speed Nm to calculate the d-axis current Id and the q-axis current Iq. The d-axis current Id and the q-axis current Iq are input to a d-axis subtraction unit 43.

[0040] The three-phase to two-phase conversion unit 42 corresponds to a coordinate conversion unit. The d-axis current Id and the q-axis current Iq are sometimes referred to as actual d-axis current and actual q-axis current, respectively, since they are actual currents obtained by performing coordinate conversion on the detected values ​​of the phase currents Iu, Iv, and Iw. Furthermore, the d-axis current Id is sometimes referred to as a field current, and the q-axis current is sometimes referred to as a drive current. The three-phase to two-phase conversion unit 42 is sometimes referred to as a uvw / dq conversion unit.

[0041] The current command unit 41 sets target values ​​for the d-axis current Id and the q-axis current Iq as a d-axis current command value Id* and a q-axis current command value Iq*, respectively. The command values ​​Id* and Iq* set by the current command unit 41 are input to a d-axis subtraction unit 43 as the d-axis current command value Id* and to a q-axis subtraction unit 44 as the q-axis current command value Iq*. A torque command value is input to the current command unit 41 as a signal from a higher-level ECU as the rotational torque to be generated by the motor 12. The current command unit 41 sets the command values ​​Id* and Iq* in accordance with the torque command value when, for example, power is supplied from the battery 11 to the motor 12.

[0042] The d-axis subtraction unit 43 calculates the deviation between the d-axis current command value Id* and the d-axis current Id as the d-axis current deviation. The q-axis subtraction unit 44 calculates the deviation between the q-axis current command value Iq* and the q-axis current Iq as the q-axis current deviation. The d-axis current deviation and the q-axis current deviation are input to the current control unit 45.

[0043] The current control unit 45 calculates a d-axis voltage command value Vd* and a q-axis voltage command value Vq* in the dq coordinate system so that the d-axis current deviation and the q-axis current deviation become zero. The current control unit 45 performs feedback control to calculate the d-axis voltage command value Vd* and the q-axis voltage command value Vq* so that the d-axis current Id matches the d-axis current command value Id* and the q-axis current Iq matches the q-axis current command value Iq*. The current control unit 45 performs, for example, PI control as the feedback control. The d-axis voltage command value Vd* and the q-axis voltage command value Vq* are input to a 2-phase to 3-phase conversion unit 46.

[0044] The two-phase to three-phase conversion unit 46 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* in the dq coordinate system into three-phase AC coordinates to calculate a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw* in the three-phase coordinate system. These voltage command values ​​Vu*, Vv*, and Vw* are voltage values ​​to be output to the three-phase windings 12a, respectively, and are information included in the drive command. A drive command including these voltage command values ​​Vu*, Vv*, and Vw* is input to the inverter 30. The two-phase to three-phase conversion unit 46 is sometimes referred to as a dq / uvw conversion unit.

[0045] The control device 40 has a drive command unit (not shown) as a functional block. The drive command unit generates a drive command according to the voltage command values ​​Vu*, Vv*, Vw*, and outputs a command signal including this drive command to the inverter 30. For example, the drive command unit compares the voltage command values ​​Vu*, Vv*, Vw* with a carrier, and generates a pulse-shaped drive command for each of the U-phase, V-phase, and W-phase. The carrier is a carrier wave such as a triangular wave, a sawtooth wave, or a rectangular wave. As a result, the arm switches 32a and 32b of the arm circuit 31 are turned on and off individually in each of the U-phase, V-phase, and W-phase.

[0046] In the drive system 10, when the motor 12 is driven and rotated by the power supply from the battery 11 during vehicle running or the like, if an inverter abnormality occurs in the inverter 30, there is a concern that a secondary abnormality will occur along with the inverter abnormality. For example, an inverter abnormality is a short circuit abnormality in which the arm switches 32a and 32b as switching elements are shorted. Here, a short circuit abnormality refers to a situation in which the arm switches 32a and 32b unintentionally transition to an on state or a situation in which the arm switches 32a and 32b are unintentionally held in an on state. When a short circuit abnormality occurs in the arm switches 32a and 32b, there is a concern that a control failure will occur in which the power conversion device 13 does not operate according to the command of the control device 40, such as the arm switches 32a and 32b not being driven off even though the control device 40 has commanded them to be driven off. If a control failure occurs, it is thought that secondary abnormalities will be more likely to occur in the drive system 10, such as overvoltage in auxiliary equipment such as a voltage sensor or the smoothing capacitor 21 due to the back electromotive force of the motor 12, or overvoltage or overcurrent in the inverter 30.

[0047] In response to this, the control device 40 performs active short circuiting on the inverter 30 when an inverter abnormality occurs. Hereinafter, active short circuiting is referred to as ASC. The control device 40 realizes ASC by turning on one of the upper arm switch 32a and the lower arm switch 32b for all three phases and turning off the other for all three phases. If the state of the inverter 30 when the control device 40 performs ASC is referred to as an ASC state, this ASC state corresponds to a one-on state.

[0048] If the ASC state is continuously maintained after inverter 30 has transitioned to the ASC state, a current due to the back electromotive force of motor 12 is unlikely to flow to smoothing capacitor 21. As a result, an overvoltage is unlikely to occur in smoothing capacitor 21, and smoothing capacitor 21 is likely to be discharged. On the other hand, if inverter 30 is continuously maintained in the ASC state, a braking torque T that brakes the rotation of motor 12 is likely to increase due to the current flowing through winding 12a. The larger the braking torque T, the stronger the braking of the rotation of motor 12. For this reason, it is considered that a sudden increase in braking torque T is likely to deteriorate the drivability of the vehicle.

[0049] As shown in FIG. 3, when the inverter 30 is held in the ASC state, the smaller the motor rotation speed Nm, the larger the holding torque T1 of the motor 12 tends to be. The holding torque T1 is the braking torque T when the inverter 30 is held in the ASC state, and is shown by a two-dot chain line in FIG. 3. The manner in which the holding torque T1 changes varies depending on the motor rotation speed Nm. For example, when the motor rotation speed Nm is greater than the rotation reference value N0, the holding torque T1 is almost zero regardless of the motor rotation speed Nm. When the motor rotation speed Nm is smaller than the rotation reference value N0, the holding torque T1 increases as the motor rotation speed Nm decreases. The rotation reference value N0 is a boundary value between a state in which the holding torque T1 occurs and a state in which it does not occur for the motor rotation speed Nm. The region in which the motor rotation speed Nm is smaller than the rotation reference value N0 is sometimes called a low rotation region.

[0050] The braking torque T is a torque in the opposite direction to the driving torque that drives the rotation of the motor 12. In FIG. 3, the braking torque T is illustrated with the opposite direction being positive. If the driving torque is a positive torque, then the braking torque T with a negative sign becomes a negative torque. In other words, the absolute value of the negative torque is the braking torque T.

[0051] When the inverter 30 is held in the ASC state, the d-axis current Id is likely to become a negative value. The smaller the motor rotation speed Nm, the more likely the d-axis current Id is to become a value closer to zero. The manner in which the d-axis current Id changes differs depending on the motor rotation speed Nm. For example, when the motor rotation speed Nm is greater than the rotation reference value N0, the d-axis current Id is at a substantially constant value. When the motor rotation speed Nm is smaller than the rotation reference value N0, the smaller the motor rotation speed Nm, the more likely the d-axis current Id is to become a value closer to zero.

[0052] In the d-axis current Id, when the inverter 30 is held in the ASC state, the relationship of Equation 1 shown in FIG. 3 is established on the condition that both the d-axis voltage Vd and the q-axis voltage Vq are zero. Equation 1 is a voltage equation for the motor 12. In Equation 1, R is the phase resistance value of the motor 12, Ld is the d-axis inductance value, Lq is the q-axis inductance value, φ is the magnetic flux density, and ω is the electrical angular velocity. Equation 1 indicates that the d-axis current Id changes as shown by the two-dot chain line in FIG. 3. Specifically, Equation 1 indicates that the absolute value of the d-axis current Id decreases as the motor rotation speed Nm decreases. Equation 1 also indicates that the absolute value of the d-axis current Id increases as the motor rotation speed Nm increases, and that the d-axis current Id approaches φ / Ld.

[0053] When the inverter 30 is held in the ASC state, the q-axis current Iq is more likely to have a larger negative value as the motor rotation speed Nm decreases. The manner in which the q-axis current Iq changes varies depending on the motor rotation speed Nm. For example, when the motor rotation speed Nm is greater than the rotation reference value N0, the q-axis current Iq is almost zero. When the motor rotation speed Nm is smaller than the rotation reference value N0, the q-axis current Iq has a larger negative value as the motor rotation speed Nm decreases. In other words, the absolute value of the q-axis current Iq increases as the motor rotation speed Nm decreases.

[0054] With respect to the q-axis current Iq, when the inverter 30 is held in the ASC state, the relationship of Equation 2 shown in FIG. 3 holds, provided that both the d-axis voltage Vd and the q-axis voltage Vq are zero. Like Equation 1, Equation 2 is a voltage equation for the motor 12. Equation 2 indicates that the q-axis current Iq changes as indicated by the two-dot chain line in FIG. 3. Specifically, it indicates that the smaller the motor rotation speed Nm, the larger the absolute value of the q-axis current Iq. Equation 2 also indicates that the higher the motor rotation speed Nm, the closer the q-axis current Iq becomes to zero, and that the q-axis current Iq asymptotically approaches zero.

[0055] When the inverter 30 is held in the ASC state, as described above, in a situation where the motor rotation speed Nm is smaller than the rotation reference value N0, the smaller the motor rotation speed Nm, the larger the value of the held torque T1. When the inverter 30 is held in the ASC state, the relationship of Equation 3 shown in FIG. 3 holds for the held torque T1. In Equation 3, P is the number of pole pairs of the motor 12. Equation 3 indicates that the held torque T1 is proportional to the q-axis current Iq. In other words, the larger the q-axis current Iq is on the negative side, the larger the held torque T1 becomes.

[0056] In contrast, it has been found through testing etc. that when ASC is performed intermittently and repeatedly, the braking torque T is more likely to be smaller than when ASC is performed continuously. According to this finding, intermittent ASC suppresses an increase in the braking torque T, particularly in the low rotation range of the motor 12.

[0057] Furthermore, it has been found through tests and the like that when ASC is performed intermittently and repeatedly, the braking torque T changes according to the duty ratio D of the ASC. According to this finding, the smaller the duty ratio D, the smaller the braking torque T tends to be. The duty ratio D is the proportion of time that ASC is performed per unit time.

[0058] Therefore, the control device 40 selectively performs ASC between a holding ASC and an intermittent ASC. Holding ASC means that ASC is performed continuously without a temporary stop. When holding ASC is performed, the inverter 30 is continuously held in the ASC state. Intermittent ASC means that ASC is repeatedly performed intermittently while repeatedly releasing the ASC temporarily. When intermittent ASC is performed, the inverter 30 intermittently and repeatedly transitions to the ASC state. In this case, the inverter 30 alternately and repeatedly transitions between the ASC state and the released state. The released state is a state in which the ASC state is released in the inverter 30.

[0059] In this embodiment, the fully off state is used as the released state. The fully off state refers to the state in which all the arm switches 32a, 32b of the inverter 30 are driven to be off, and the state of the inverter 30 when the control device 40 performs the fully off state is referred to as the fully off state. When the inverter 30 is in the fully off state, the current flowing through the winding 12a is likely to be interrupted. For this reason, the braking torque T of the motor 12 is reduced, and the motor 12 is likely to rotate by inertia. In the intermittent ASC, the control device 40 alternately repeats the ASC and the fully off state, and the inverter 30 alternately and repeatedly transitions between the ASC state and the fully off state. In the motor 12, the current flowing through the winding 12a is repeatedly temporarily interrupted.

[0060] When the maintained ASC, the intermittent ASC, and the all-off are shown in terms of the relationship between the ASC and the duty ratio D, the ASC when the duty ratio D is set to 1 is the maintained ASC. The ASC when the duty ratio D is set to zero is the all-off. The ASC when the duty ratio D is set to a value greater than zero and less than 1 is the intermittent ASC.

[0061] The control device 40 performs an inverter control process for controlling the inverter 30. The holding ASC and the intermittent ASC are performed by the inverter control process. The inverter control process will be described with reference to the flowchart of FIG. 4. The control device 40 repeatedly executes the inverter control process at a predetermined cycle. The control device 40 has a function of executing each step of the inverter control process.

[0062] 4, in step S101, it is determined whether or not an inverter abnormality has occurred. Here, it is determined whether or not there is an abnormality in the drive of the inverter 30 according to a drive command from the control device 40. For example, the detection signals of various sensors such as the current sensor 28 are compared with the drive command to the inverter 30, and the drive state of the inverter 30 is determined using the comparison result. Note that the function of the control device 40 that executes the process of step S101 corresponds to an abnormality determination unit.

[0063] If an inverter abnormality occurs, the process proceeds to step S102. In step S102, the motor rotation speed Nm is obtained using the detection signal of the rotation sensor 29.

[0064] In step S103, it is determined whether the motor rotation speed Nm is equal to or lower than a predetermined rotation threshold value N1. The rotation threshold value N1 is a value smaller than the rotation reference value N0. Here, the braking torque T generated by the motor 12 when the holding ASC is performed is set as the torque threshold value Ta. The torque threshold value Ta is a braking torque T that does not cause the braking of the rotation of the motor 12 to be too strong and does not cause the drivability of the vehicle to be too deteriorated. Using correlation information that the braking torque T increases as the motor rotation speed Nm decreases, a value corresponding to the torque threshold value Ta for the motor rotation speed Nm is calculated as the rotation threshold value N1. The rotation threshold value N1 is information acquired by a test, a simulation, or the like, and is stored in a storage unit such as a memory in the control device 40. The rotation threshold value N1 corresponds to the intermittent threshold value. The torque threshold value Ta may be referred to as an allowable torque.

[0065] If the motor rotation speed Nm is equal to or lower than the rotation threshold value N1, the process proceeds to step S104, where the duty ratio D is set. Here, the duty ratio D is variably set according to the motor rotation speed Nm. Specifically, the smaller the motor rotation speed Nm is, the smaller the duty ratio D is set. For example, the duty ratio D is calculated from the motor rotation speed Nm using correlation information indicating the correlation between the motor rotation speed Nm and the duty ratio D. This correlation information is, for example, a map or function as shown in FIG. 3, and is stored in the storage unit of the control device 40. In the map shown in FIG. 3, in the region where the motor rotation speed Nm is from zero to N1, the larger the motor rotation speed Nm is, the larger the duty ratio D is. Note that the function of the control device 40 that executes the process of step S104 corresponds to the duty setting unit.

[0066] In step S105, intermittent ASC is performed. Here, a drive command is generated according to the duty ratio D. The intermittent ASC corresponds to the intermittent processing. The function of the control device 40 that executes the processing of step S105 corresponds to a half-on intermittent section.

[0067] A carrier is used, for example, to generate the drive command. As shown in Fig. 5, the carrier is compared with a duty ratio D to generate a pulse-shaped drive command. This drive command is common to the U-phase, V-phase, and W-phase. The period of the drive command is the same as the carrier period P, which is the period of the carrier. In intermittent ASC, ASC and release are performed once each in one carrier period. In intermittent ASC, the period for repeating ASC is the same as the carrier period P. The repeating period of ASC is determined according to the carrier frequency.

[0068] For example, the period of the drive command Ca generated according to the duty ratio Da is the same as the period of the drive command Cb generated according to the duty ratio Db. The duty ratios Da and Db have different values. For example, the duration of one ASC in the intermittent ASC is longer for the drive command Cb than for the drive command Ca. Also, the duration of one all-off in the intermittent ASC is longer for the drive command Ca than for the drive command Cb.

[0069] For all of the U-phase, V-phase, and W-phase of the inverter 30, a drive command generated according to the duty ratio D is output to one of the arm switches 32a, 32b. To the other, a drive command is output to drive the arm switches 32a, 32b in the off state and maintain the arm switches in the off state. In this way, the inverter 30 executes intermittent ASC, which alternates between ASC and full off. In this intermittent ASC, the cycle in which ASC and full off are repeated is the same as the carrier cycle P.

[0070] In step S105, a drive command is generated according to the type of the inverter abnormality. For example, it is determined whether a short circuit abnormality or an open circuit abnormality has occurred in the arm switch 32a, 32b of the U-phase, V-phase, or W-phase in the inverter 30. For example, when an open circuit abnormality occurs in the upper arm switch 32a, a drive command is generated to hold all upper arm switches 32a, including the upper arm switch 32a in which the open circuit abnormality has occurred, in the off state. This drive command turns on and off the lower arm switches 32b of all three phases according to the duty ratio D.

[0071] In step S103, if the motor rotation speed Nm is not equal to or less than the rotation threshold value N1, the process proceeds to step S106. In step S106, the holding ASC is performed. Here, for all of the U-phase, V-phase, and W-phase, a drive command is generated to turn off one of the arm switches 32a and 32b and to keep it in the off state, and turn on the other one and to keep it in the on state. Then, this drive command is output to the inverter 30. In this manner, the holding ASC is performed by the inverter 30. In this step S106, a drive command is generated according to the state of the inverter abnormality, as in step S105. Note that the holding ASC can be performed by setting the duty ratio D of the ASC to 1. Also, the function of the control device 40 to execute the process of step S106 corresponds to a one-on holding unit.

[0072] In step S107, it is determined whether the vehicle has stopped. Here, it is determined whether a vehicle switch such as an ignition switch is on. If the vehicle switch is on, it is determined that the vehicle is not stopped and the process returns to step S102. In this case, the processes of steps S102 to S107 are repeated until the vehicle stops. If the vehicle has stopped, the process proceeds to step S108 and a termination process is performed. In this termination process, both arm switches 32a, 32b are switched to the off state for all of the U-phase, V-phase, and W-phase.

[0073] Next, the manner in which the braking torque T changes when an inverter abnormality occurs will be described with reference to FIG.

[0074] In FIG. 3, in a region where the motor rotation speed Nm is greater than the rotation threshold value N1, the holding ASC is performed. In this region, the braking torque T is small even if the intermittent ASC is not performed. The braking torque T is the same as the holding torque T1 due to the holding ASC being performed. In a region where the motor rotation speed Nm is greater than the rotation threshold value N1 and where the motor rotation speed Nm is greater than the rotation reference value N0, the braking torque T is almost zero. On the other hand, in a region where the motor rotation speed Nm is greater than the rotation threshold value N1 and equal to or less than the rotation reference value N0, the braking torque T is a value between zero and the torque threshold value Ta. When the holding ASC is performed, the duty ratio D of the ASC is set to 1.

[0075] In a region where the motor rotation speed Nm is equal to or lower than the rotation threshold value N1, intermittent ASC is performed. In this region, the closer the motor rotation speed Nm is to zero, the smaller the duty ratio D of the ASC is set to. If the braking torque T when intermittent ASC is performed is referred to as intermittent torque T2, in a region where the motor rotation speed Nm is equal to or lower than N1, the intermittent torque T2 is smaller than the holding torque T1. For example, while the holding torque T1 increases as the motor rotation speed Nm approaches zero, the intermittent torque T2 is maintained at approximately the same value as the torque threshold value Ta even when the motor rotation speed Nm approaches zero.

[0076] According to the present embodiment described so far, when an inverter abnormality occurs, intermittent ASC is performed. In this case, by utilizing the knowledge that the braking torque T of the motor 12 is reduced by the intermittent ASC, it is possible to prevent the braking applied to the rotation of the motor 12 from becoming too strong. Therefore, when an inverter abnormality occurs, it is possible to appropriately manage the strength of the braking applied to the rotation of the motor 12. In this case, it is possible to prevent a sudden increase in the braking torque T from deteriorating the drivability of the vehicle. In other words, since a sudden increase in the braking torque T is suppressed by the intermittent ASC, it is possible to improve the drivability of the vehicle.

[0077] Furthermore, for example, when the output of the motor 12 is increased, the flux linkage, which is the field flux generated in the motor 12, increases. As a result, the current flowing through the arm switches 32a and 32b due to the ASC increases in proportion to the flux linkage. In this case, there is a concern that the heat generated in the inverter 30 due to the current flowing through the arm switches 32a and 32b will become excessively large. As a result, the cooling of the inverter 30 will not be able to keep up with the heat generation, resulting in a "heat insufficient state."

[0078] In contrast, according to this embodiment, when an inverter abnormality occurs and intermittent ASC is performed, the back electromotive force of the motor 12 is likely to be reduced together with the braking torque T. When the back electromotive force is reduced, the current flowing through the arm switches 32a and 32b is reduced, so that the heat generated by the inverter 30 is unlikely to be large. Therefore, it is possible to prevent the inverter 30 from entering a "non-thermal establishment state."

[0079] As described above, intermittent ASC can both appropriately manage the strength of braking applied to the rotation of motor 12 and suppress heat generation in inverter 30 in response to the occurrence of an inverter abnormality. However, intermittent ASC has a smaller deterrent effect on the flow of current through inverter 30 than holding ASC. In other words, when intermittent ASC is performed, the current flowing through inverter 30 is less likely to decrease compared to when holding ASC is performed. For this reason, intermittent ASC prioritizes managing the strength of braking applied to the rotation of motor 12 over suppressing heat generation in inverter 30.

[0080] If the voltage due to the counter electromotive force of the motor 12 is referred to as the counter electromotive voltage, the smaller the motor rotation speed Nm, the smaller the counter electromotive voltage. Furthermore, when the counter electromotive voltage is small, overvoltage and overcurrent of the inverter 30 and overvoltage of the smoothing capacitor 21 are less likely to occur. Therefore, when the motor rotation speed Nm is equal to or less than the rotation threshold value N1, and the counter electromotive force of the motor 12 is not likely to become large, even if intermittent ASC is performed, overvoltage of the smoothing capacitor 21 is less likely to occur, and overvoltage and overcurrent of the inverter 30 are less likely to occur. For this reason, intermittent ASC can suitably achieve both managing the strength of braking against the rotation of the motor 12 and suppressing heat generation of the inverter 30.

[0081] According to this embodiment, the duty ratio D is variably set during intermittent ASC. In this configuration, by utilizing the knowledge that the braking torque T changes according to the duty ratio D, the braking torque T can be appropriately managed by variably setting the duty ratio D. This makes it possible to prevent the braking torque T from becoming too large.

[0082] In the motor 12, the braking torque T is likely to increase as the motor rotation speed Nm decreases. In other words, the vehicle's drivability is likely to decrease as the motor rotation speed Nm decreases. In contrast, according to this embodiment, in the intermittent ASC, the duty ratio D is set to a smaller value as the motor rotation speed Nm decreases. In this configuration, by utilizing the knowledge that the braking torque T decreases as the duty ratio D decreases, for example, when the motor rotation speed Nm is in a low rotation range, the braking torque T is unlikely to become too large. Therefore, by reducing the duty ratio D, it is possible to suppress the decrease in the vehicle's drivability that accompanies the small motor rotation speed Nm.

[0083] According to the present embodiment, in the intermittent ASC, the ASC is intermittently repeated at a cycle corresponding to the carrier cycle P. In this manner, since the ASC cycle is set using the carrier, it is possible to suppress an increase in the processing load for setting the ASC cycle.

[0084] In intermittent ASC, if the ASC repetition period is too long, the number of ASCs per unit time becomes too small, making it easier for mechanical resonance to occur in the motor 12 or the vehicle body. In this case, there is a concern that an abnormality may occur in the drive system 10. In contrast, according to this embodiment, the ASC period in intermittent ASC is set according to the carrier frequency, so the number of ASC repetitions per unit time can be optimized. This makes it possible to prevent an abnormality from occurring in the drive system 10 due to the number of ASC repetitions.

[0085] According to this embodiment, intermittent ASC is performed when motor rotation speed Nm is equal to or lower than rotation threshold value N1. Therefore, intermittent ASC can prevent braking torque T from becoming too large when motor rotation speed Nm is equal to or lower than rotation threshold value N1. Moreover, assuming a case where holding ASC is performed regardless of motor rotation speed Nm, the value at which braking torque T becomes torque threshold value Ta for motor rotation speed Nm is set to rotation threshold value N1, so that braking torque T is prevented from becoming larger than torque threshold value Ta. Therefore, performing intermittent ASC when motor rotation speed Nm is equal to or lower than rotation threshold value N1 can prevent braking torque T from becoming so large that vehicle drivability is excessively deteriorated.

[0086] According to this embodiment, the holding ASC is performed when the motor rotation speed Nm is not equal to or less than the rotation threshold value N1. Therefore, in a situation where the braking torque T is not too large, that is, when the motor rotation speed Nm is greater than the rotation threshold value N1, it is possible to prioritize suppressing heat generation in the inverter 30 over managing the strength of braking applied to the rotation of the motor 12. As a result, when an inverter abnormality occurs, the holding ASC can suppress the occurrence of a secondary abnormality in the drive system 10.

[0087] <Second embodiment> In the first embodiment, the control device 40 selectively uses the intermittent ASC and the holding ASC in accordance with the motor rotation speed Nm. In contrast, in the second embodiment, the control device 40 selectively uses the intermittent ASC, the holding ASC, and all-off in accordance with the motor rotation speed Nm. The configuration, action, and effect not specifically described in this embodiment are the same as those in the first embodiment. In this embodiment, the differences from the first embodiment will be mainly described.

[0088] The control device 40 can perform all-off in addition to the intermittent ASC and the held ASC. All-off is a process used to temporarily cancel ASC in the intermittent ASC of the first embodiment. In this embodiment, the control device 40 performs all-off continuously, rather than performing all-off as part of the intermittent ASC. When the control device 40 performs all-off, the inverter 30 is continuously held in the all-off state. When the inverter 30 is in the all-off state, all the arm switches 32a, 32b are in the off state.

[0089] The control device 40 performs inverter control processing including all-off in addition to the intermittent ASC and the holding ASC. This inverter control processing will be described with reference to the flowchart of FIG.

[0090] 6, in steps S101 to S103, the same processes as those in the first embodiment are performed. In step S103, if the motor rotation speed Nm is equal to or less than the rotation threshold value N1, the process proceeds to step S201.

[0091] In step S201, it is determined whether the motor rotation speed Nm is equal to or greater than a predetermined low-side threshold value N2. The low-side threshold value N2 is a value smaller than the rotation threshold value N1. For the motor rotation speed Nm, a value at which an overvoltage or overcurrent of the inverter 30 is unlikely to occur when the inverter 30 is in a fully off state is set as the low-side threshold value N2. The low-side threshold value N2 is the largest value within a range at which an overvoltage or overcurrent of the inverter 30 does not occur for the motor rotation speed Nm. The low-side threshold value N2 is, for example, about half the value of the rotation threshold value N1. The low-side threshold value N2 is information acquired by a test, a simulation, or the like, and is stored in the storage unit of the control device 40.

[0092] If the motor speed Nm is not equal to or greater than the small side threshold N2, the motor speed Nm is determined to be smaller than the rotation threshold N1, and the process proceeds to step S202. In step S202, full OFF is performed. Here, a drive command is generated to drive both arm switches 32a and 32b off and to keep them in the off state for all of the U, V, and W phases. Then, this drive command is output to the inverter 30, causing the inverter 30 to execute full OFF. In addition, in this step S202, a drive command is generated according to the type of inverter abnormality, similar to steps S105 and S106 in the first embodiment. In addition, full OFF can be performed by setting the duty ratio D of the ASC to zero. In addition, the function of executing the process of step S202 in the control device 40 corresponds to the full OFF part and the small side OFF part.

[0093] On the other hand, in step S201, if the motor rotation speed Nm is equal to or greater than the small threshold value N2, the process proceeds to steps S104 and S105. In step S104, the duty ratio D is set, and in step S105, intermittent ASC is performed. After steps S105 and S202, the process proceeds to step S107, and the processes of steps S102 to S107, S201, and S202 are repeated until the vehicle stops.

[0094] Next, the manner in which the braking torque T changes when an inverter abnormality occurs will be described with reference to FIG.

[0095] 7, in a region where the motor rotation speed Nm is equal to or less than the rotation threshold value N1 and is greater than the small threshold value N2, the intermittent ASC is performed. In this region, even if the motor rotation speed Nm decreases toward the small threshold value N2, the intermittent torque T2 is maintained at approximately the same value as the torque threshold value Ta.

[0096] On the other hand, in the region where the motor rotation speed Nm is equal to or lower than the small side threshold value N2, full OFF is performed instead of intermittent ASC. If the braking torque T when full OFF is performed is referred to as full OFF torque T3, this full OFF torque T3 is almost zero regardless of the motor rotation speed Nm. This is because all arm switches 32a, 32b cut off the current supply to the winding 12a. When full OFF is performed, the duty ratio D of the ASC is set to zero.

[0097] In the drive system 10, the smaller the motor rotation speed Nm, the less likely an overvoltage or overcurrent of the inverter 30 or an overvoltage of the smoothing capacitor 21 occurs. In contrast, according to the present embodiment, when the motor rotation speed Nm is equal to or less than the small threshold N2, the full-off is performed. By setting the small threshold N2 to a sufficiently small value, even if the intermittent ASC or the holding ASC is not performed when the motor rotation speed Nm is equal to or less than the small threshold N2, an overvoltage or overcurrent of the inverter 30 or an overvoltage of the smoothing capacitor 21 is less likely to occur. Therefore, when the motor rotation speed Nm is equal to or less than the small threshold N2, it is possible to avoid the rotation of the motor 12 being forcibly braked by the intermittent ASC or the holding ASC in a situation where the inverter 30 is unlikely to generate heat. As a result, when an inverter abnormality occurs, the drivability of the vehicle can be improved in a situation where the motor rotation speed Nm is sufficiently small, such as equal to or less than the small threshold N2.

[0098] <Third embodiment> In the second embodiment, the control device 40 selectively uses the intermittent ASC, the holding ASC, and all OFF in accordance with the motor rotation speed Nm. In contrast, in the third embodiment, the control device 40 selectively uses the holding ASC and all OFF in accordance with the motor rotation speed Nm. The configuration, action, and effect not specifically described in this embodiment are the same as those in the first and second embodiments. In this embodiment, the differences from the first and second embodiments will be mainly described.

[0099] The control device 40 performs inverter control processing including holding ASC and all-off. This inverter control processing will be described with reference to the flowchart of FIG.

[0100] In FIG. 8, in steps S101 and S102, the same processing as in the first embodiment is performed. After acquiring the motor rotation speed Nm in step S102, the process proceeds to step S301, where it is determined whether the motor rotation speed Nm is equal to or greater than the high threshold value N3. The high threshold value N3 is a value greater than both the rotation threshold value N1 and the rotation reference value N0. Regarding the motor rotation speed Nm, a value at which the retained torque T1 becomes zero when the inverter 30 is retained in the ASC state is set as the high threshold value N3. The high threshold value N3 is set to a value at which the difference between the high threshold value N3 and the rotation reference value N0 is smaller than the difference between the rotation reference value N0 and the rotation threshold value N1, for example.

[0101] If the motor speed Nm is equal to or greater than the large threshold value N3, the process proceeds to step S302, where the retained ASC is performed in the same manner as in step S106 of the first embodiment. On the other hand, if the motor speed Nm is not equal to or greater than the large threshold value N3, the process proceeds to step S303, where the full-off is performed in the same manner as in step S202 of the second embodiment. After step S302 or step S303, the process proceeds to step S107, where the processes of steps S102, S107, and S301 to S303 are repeated until the vehicle stops. The function of the control device 40 that performs the process of step S303 corresponds to the full-off section and the large-side off section.

[0102] Next, the manner in which the braking torque T changes when an inverter abnormality occurs will be described with reference to FIG.

[0103] As shown in FIG. 9, in the region where the motor rotation speed Nm is equal to or lower than the large threshold value N3, full-off is performed. In this region, the full-off torque T3 is almost zero regardless of the motor rotation speed Nm. When full-off is performed, the duty ratio D of the ASC is set to zero. On the other hand, in the region where the motor rotation speed Nm is greater than the large threshold value N3, the holding ASC is performed. In this region, the braking torque T is almost zero. When the holding ASC is performed, the duty ratio D is set to 1.

[0104] Assuming that a holding ASC is performed, in a region where the motor rotation speed Nm is greater than the rotation threshold value N1, the braking torque T is unlikely to become large. Furthermore, in a region where the motor rotation speed Nm is greater than a larger threshold value N3 that is greater than the rotation threshold value N1, the braking torque T is unlikely to become large. In other words, when holding ASC or intermittent ASC is performed, in a region where the motor rotation speed Nm is equal to or less than the larger threshold value N3, the braking torque T may be generated.

[0105] In contrast, according to this embodiment, the full-off is performed when the motor rotation speed Nm is equal to or lower than the large threshold value N3. That is, the full-off is performed in a region where the braking torque T may be generated when the holding ASC or the intermittent ASC is performed for the motor rotation speed Nm. This makes it possible to more reliably prevent the braking torque T from being generated when an inverter abnormality occurs. Therefore, it is possible to avoid a decrease in the drivability of the vehicle when an inverter abnormality occurs.

[0106] <Fourth embodiment> In the third embodiment, the full-off is performed when the motor rotation speed Nm is smaller than the large threshold value N3. In contrast, in the fourth embodiment, the full-off is performed when the motor rotation speed Nm is smaller than the small threshold value N2. The configurations, actions, and effects not specifically described in this embodiment are the same as those of the first to third embodiments. In this embodiment, the differences from the first to third embodiments will be mainly described.

[0107] The control device 40 performs a full-off when the motor rotation speed Nm is smaller than the large threshold value N3, as well as when the motor rotation speed Nm is smaller than the small threshold value N2. However, when the motor rotation speed Nm is smaller than the large threshold value N3, the full-off is performed when the condition that the motor rotation speed Nm is larger than the rotation threshold value N1 is satisfied. Also, when the motor rotation speed Nm is smaller than the small threshold value N2, the full-off is performed when the condition that the motor rotation speed Nm is equal to or smaller than the rotation threshold value N1 is satisfied.

[0108] The control device 40 performs inverter control processing, which will be described with reference to the flowchart of FIG.

[0109] In FIG. 10, in steps S101 to S103, the same processing as in the first embodiment is performed. In step S103, if the motor rotation speed Nm is equal to or less than the rotation threshold value N1, the process proceeds to step S401. In step S401, similar to step S201 in the second embodiment, it is determined whether the motor rotation speed Nm is equal to or greater than the small side threshold value N2. If the motor rotation speed Nm is not equal to or greater than the small side threshold value N2, the process proceeds to step S402, where all-off is performed, similar to step S202 in the second embodiment. On the other hand, if the motor rotation speed Nm is equal to or greater than the small side threshold value N2, the duty ratio D is set in step S104, and intermittent ASC is performed in step S105.

[0110] In the above step S103, if the motor rotation speed Nm is not equal to or less than the rotation threshold value N1, the process proceeds to step S403. In step S403, similar to step S301 in the above third embodiment, it is determined whether the motor rotation speed Nm is equal to or greater than the large threshold value N3. If the motor rotation speed Nm is not equal to or greater than the large threshold value N3, the process proceeds to step S404, where all-off is performed similar to step S402. On the other hand, if the motor rotation speed Nm is equal to or greater than the large threshold value N3, the process proceeds to step S106, where the holding ASC is performed.

[0111] After steps S402 and S404, the process proceeds to step S107, and steps S101 to S107 and S401 to S404 are repeated until the vehicle stops. Note that the function of the control device 40 that executes the process of step S402 corresponds to the full-off section and the small side-off section. The function of the control device 40 that executes the process of step S404 corresponds to the full-off section and the large side-off section.

[0112] <Fifth embodiment> In the first embodiment, the drive system 10 has one motor 12 and one power conversion device 13. In contrast, in the fifth embodiment, the drive system 10 has a plurality of motors 12 and a plurality of power conversion devices 13. The configurations, actions, and effects not specifically described in this embodiment are the same as those in the first embodiment. In this embodiment, the differences from the first embodiment will be mainly described.

[0113] 11 , the drive system 10 has x motors 12 and x power conversion devices 13. If one motor 12 and one power conversion device 13 connected to this motor 12 are considered as one pair, then the drive system 10 includes x pairs of motors 12 and power conversion devices 13. Each of the x power conversion devices 13 has an inverter 30. Therefore, the drive system 10 has x inverters 30.

[0114] 11, each of the x inverters 30 has three-phase arm circuits 31, similar to the first embodiment. Each of the arm circuits 31 has arms 31a and 31b, and each of the arms 31a and 31b has arm switches 32a and 32b.

[0115] In the drive system 10, the control device 40 is capable of individually controlling each of the x power conversion devices 13. Each of the x power conversion devices 13 is electrically connected to the control device 40. The drive system 10 has a power conversion system 50. The power conversion system 50 has the x power conversion devices 13 and the control device 40.

[0116] In a vehicle, one set of motor 12 and power conversion device 13 is provided for one drive wheel. For example, a vehicle has four drive wheels, and four sets of motor 12 and power conversion device 13 are provided on the vehicle. The control device 40 controls the four power conversion devices 13 individually to drive the four drive wheels individually. The drive wheels are objects to be driven that rotate as the motor 12 is driven.

[0117] The control device 40 performs inverter control processing on the x inverters 30 as control targets. This inverter control processing will be described with reference to the flowchart of FIG.

[0118] 12, in step S501, it is determined whether or not an inverter abnormality has occurred for each of the x inverters 30. For example, a determination process similar to step S101 in the first embodiment is performed for each of the x inverters 30. If an inverter abnormality has occurred in at least one of the x inverters 30, the process proceeds to step S502. Note that the function of the control device 40 that executes the process of step S501 corresponds to an abnormality determination unit.

[0119] In step S502, the motor rotation speed Nm is acquired for each of the x motors 12. For example, the same acquisition process as in step S102 in the first embodiment is performed for each of the x motors 12.

[0120] In step S503, at least two of the x inverters 30 are set as target inverters. The target inverters are inverters 30 that are targets of ASC such as intermittent ASC and holding ASC. The at least two target inverters include an inverter 30 in which an abnormality has occurred. For example, an even number of inverters 30 are set as target inverters. When there is an even number of inverters 30 in which an inverter abnormality has occurred, all of these inverters 30 are set as target inverters. When there is an odd number of inverters 30 in which an inverter abnormality has occurred, in addition to all of these inverters 30, one inverter 30 in which an inverter abnormality has not occurred is set as a target inverter. Therefore, in this step S503, at least two target inverters are set.

[0121] In step S504, it is determined whether the motor rotation speed Nm of the target motor is equal to or less than the rotation threshold value N1. The target motor is the motor 12 that is connected to the target inverter and is supplied with power from the target inverter. For example, a determination process similar to step S103 in the first embodiment is performed for each of at least two target motors. If the motor rotation speed Nm of at least one of the target motors is equal to or less than the rotation threshold value N1, it is determined that the motor rotation speed Nm of the target motor is equal to or less than the rotation threshold value N1, and the process proceeds to step S505. Note that power is supplied to the target motor from the target inverter.

[0122] In step S505, a duty ratio D is set for the target inverter. Here, the duty ratio D is set according to the motor rotation speed Nm of the target motor. For example, a common duty ratio D is set for at least two target inverters. First, the duty ratio D is calculated for each of the at least two target inverters according to the motor rotation speed Nm, and the average value of these duty ratios D is calculated. Then, this average value is set as the common duty ratio D for the at least two target inverters. The duty ratios D set for the at least two target inverters have the same value.

[0123] The setting range of the duty ratio D is limited according to the number of target inverters. For example, when there are two target inverters, the setting range of the duty ratio D is limited to a range greater than zero and equal to or less than 0.5. As described later, the ASC states of at least two target inverters are controlled so as not to overlap. Therefore, in order to prevent the ASC states of at least two target inverters from overlapping, it is necessary to limit the setting range of the duty ratio D.

[0124] In step S506, the order in which intermittent ASC is performed on the target inverters is set as the ASC order. For example, if there are two target inverters, one is set as the first inverter and the other is set as the second inverter. The function of the control device 40 that executes the process of step S506 corresponds to the order setting unit.

[0125] In step S507, intermittent ASC is performed on the target inverter. Here, intermittent ASC is performed so that the ASC for at least two target inverters does not overlap with each other. For example, intermittent ASC is performed so that at least two target inverters transition to the ASC state in order and the periods during which these target inverters transition to the ASC state do not overlap with each other.

[0126] In this step S507, drive commands are individually generated for at least two target inverters according to the duty ratio D and the ASC order. For each target inverter, a drive command for the intermittent ASC is generated using a carrier, for example, as in step S105 of the first embodiment. In the individually generated drive commands, the cycles of the intermittent ASC for at least two target inverters are the same, and the phase difference between them is zero. For these drive commands, the phase of the drive command for the other target inverters is changed according to the number of target inverters, based on the drive command for one target inverter. For example, when there are two target inverters, the drive commands for these target inverters are changed so that the phase difference between the intermittent ASCs is 180 degrees. When there are three target inverters, the drive commands for these target inverters are changed so that the phase difference between the intermittent ASCs is 120 degrees.

[0127] For example, in Fig. 11 and Fig. 13, it is assumed that inverters 301 and 302 are set as target inverters among z inverters 30. Motors 121 and 122 connected to inverters 301 and 302 are the target motors. Power is supplied to the target motor from the target inverter. In this step S507, inverters 301 and 302 are made to perform intermittent ASC in parallel so that the ASC states of inverters 301 and 302 do not overlap with each other. Note that inverters 301 and 302, which are the target inverters, correspond to a target conversion unit. Also, a function of control device 40 that executes the process of step S507 corresponds to a target intermittent unit.

[0128] As shown in Fig. 13, regarding the intermittent ASC, a period during which the first inverter 301 is in the ASC state is referred to as a first period ASC1, and a period during which the second inverter 302 is in the ASC state is referred to as a second period ASC2. In this case, the intermittent ASC for the first inverter 301 and the intermittent ASC for the second inverter 302 are performed in parallel, while the first period ASC1 and the second period ASC2 are arranged in order so as not to overlap with each other. The control device 40 executes the ASC for the first inverter 301 and the ASC for the second inverter 302 in order at timings that do not overlap with each other. The ASC repetition period is the same for the intermittent ASC for the first inverter 301 and the intermittent ASC for the second inverter 302.

[0129] In step S504, if the motor speed Nm of the target motor is not equal to or less than the rotation threshold value N1, the holding ASC is executed, and the process proceeds to step S508. In step S508, the holding ASC is executed for the target inverter. Here, the holding ASC is executed for all of at least two target inverters. For each target inverter, a drive command for the holding ASC is generated and output, for example, similar to step S106 in the first embodiment.

[0130] In step S509, it is determined whether the vehicle has stopped, similarly to step S107 in the first embodiment. Then, the processes of steps S502 to S509 are repeated until the vehicle has stopped. If the vehicle has stopped, the process proceeds to step S510, where an end process is performed, similarly to step S108 in the first embodiment.

[0131] Next, the present embodiment will be described taking as an example a case in which inverters 301 and 302 out of the multiple inverters 30 in FIG. 11 and FIG. 13 are set as target inverters.

[0132] According to this embodiment, when inverters 301, 302 are set as target inverters due to the occurrence of an inverter abnormality, intermittent ASC is performed on these inverters 301, 302. Therefore, for each of motors 121, 122, which are the target motors, the strength of braking against the rotation can be appropriately managed, as in the first embodiment described above.

[0133] Unlike the present embodiment, for example, a configuration is assumed in which the intermittent ASC is not performed in parallel but separately for the inverters 301 and 302. In this configuration, one of the motors 121 and 122 is in a state in which the strength of braking for its rotation is managed by the intermittent ASC, and the other is in a state in which the strength of braking for its rotation is not managed by the intermittent ASC. For this reason, there is a concern that the balance of the rotation between the motors 121 and 122 will be poor. For example, a configuration is assumed in which the motor 121 drives one of two drive wheels in a vehicle, and the motor 122 drives the other. In this configuration, the braking for the rotation of one drive wheel is managed by the intermittent ASC, and the braking for the rotation of the other drive wheel is not managed by the intermittent ASC. In this case, the drivability and operability of the vehicle are likely to be reduced.

[0134] In contrast, according to the present embodiment, intermittent ASC is performed in parallel for each of the inverters 301, 302. Therefore, the strength of braking for the rotation of each of the motors 121, 122 can be managed in parallel by intermittent ASC. Therefore, the rotation balance of the motors 121, 122 can be improved.

[0135] Furthermore, when intermittent ASC is performed on each of the inverters 301, 302, the braking torque T of the motors 121, 122 is likely to increase or decrease in accordance with the repetition of the ASC state due to the inverters 301, 302 repeatedly transitioning to the ASC state intermittently. In other words, torque ripple is likely to occur in the motors 121, 122. Unlike this embodiment, in a configuration in which the inverters 301, 302 simultaneously transition to the ASC state, for example, there is a concern that the torque ripples generated in the motors 121, 122 will be synchronously amplified.

[0136] In contrast, according to the present embodiment, when intermittent ASC is performed in parallel on the inverters 301, 302, the inverters 301, 302 transition to the ASC state in sequence. In this configuration, even if torque ripple occurs in each of the motors 121, 122, these torque ripples are unlikely to be synchronized. Therefore, after improving the balance of the rotation of the motors 121, 122, the torque ripples generated in each of the motors 121, 122 can be managed comprehensively. In other words, when an inverter abnormality occurs, the torque ripples of the motors 121, 122 can be appropriately managed in the entire drive system 10.

[0137] According to this embodiment, the first period ASC1 during which the first inverter 301 is in the ASC state and the second period ASC2 during which the second inverter 302 is in the ASC state are shifted from each other. That is, the first period ASC1 and the second period ASC2 are arranged in order so as not to overlap each other. In this state, a state in which the rotation of one of the motors 121, 122 is braked and a state in which the rotation of the other is braked are repeated in order. Therefore, the rotation of one of the motors 121, 122 is braked almost continuously in the entire drive system 10. Therefore, the torque ripple can be reduced in the entire drive system 10.

[0138] In a vehicle, reducing the overall torque ripple for the two drive wheels improves drivability, and improving the rotational balance of the two drive wheels reduces vibrations and noise that occur when the rotational balance between the two drive wheels deteriorates.

[0139] <Other embodiments> The disclosure of this specification is not limited to the exemplified embodiments. The disclosure includes the exemplified embodiments and modifications by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of parts and elements shown in the embodiments, and can be implemented in various modifications. The disclosure can be implemented by various combinations. The disclosure can have additional parts that can be added to the embodiments. The disclosure includes those in which parts and elements of the embodiments are omitted. The disclosure includes the replacement or combination of parts and elements between one embodiment and another embodiment. The disclosed technical scope is not limited to the description of the embodiments. The disclosed technical scope is indicated by the description of the claims, and should be interpreted as including all modifications within the meaning and scope equivalent to the description of the claims.

[0140] In each of the above embodiments, the process of canceling ASC in intermittent ASC does not have to be full off. That is, when the control device 40 is performing intermittent ASC, the release state in which the ASC state of the inverter 30 is released does not have to be a full off state. For example, the process of canceling ASC in intermittent ASC may be a switching process for the inverter 30. That is, for intermittent ASC, the state in which the ASC state of the inverter 30 is released may be a control state in which switching control of the inverter 30 is performed by vector control.

[0141] In each of the above embodiments, the duty ratio D may be variably set according to a parameter different from the motor rotation speed Nm. For example, the duty ratio D may be variably set according to the temperature of the motor 12. Furthermore, the parameter used to variably set the duty ratio D does not have to be one. For example, the duty ratio D may be variably set according to both the motor rotation speed Nm and the motor temperature. Furthermore, the duty ratio D may be a fixed value rather than a variable value. That is, the duty ratio D may be set to a predetermined fixed value regardless of the motor rotation speed Nm.

[0142] In each of the above embodiments, a parameter other than the motor rotation speed Nm may be used as a parameter for determining whether or not to perform intermittent ASC. For example, the determination of whether or not to perform intermittent ASC may be made according to the motor temperature. Furthermore, the number of parameters for determining whether or not to perform intermittent ASC does not need to be one. For example, the determination of whether or not to perform intermittent ASC may be made according to both the motor rotation speed Nm and the motor temperature. Furthermore, when an inverter abnormality occurs, the control device 40 may perform only one of intermittent ASC, holding ASC, and all-off. For example, when an inverter abnormality occurs, the control device 40 may perform only intermittent ASC regardless of the motor rotation speed Nm, etc.

[0143] In the fifth embodiment, as long as at least two target inverters are switched to the ASC state in sequence during intermittent ASC, the periods during which these target inverters are in the ASC state may overlap with each other. For example, a configuration may be adopted in which the setting range of the duty ratio D is not limited by the number of target inverters. In this configuration, when there are two target inverters, the duty ratio D may be set to a value greater than 0.5.

[0144] In each of the above embodiments, the period of the drive command does not have to be the same as the carrier period P when performing intermittent ASC. For example, the time for performing one ASC and the time for performing one release are determined in advance. Then, the number of times ASC is performed consecutively and the number of times release is performed consecutively are set according to the duty ratio D, respectively. In this configuration, the number of ASCs and the number of releases change according to the duty ratio D, and as a result, the period of the drive command changes. Note that even if ASC and release are performed consecutively multiple times, the intermittent ASC is performed by alternating between ASC and release. Also, in the intermittent ASC, one of the duration of ASC and the duration of release may be set to a fixed time, and the other may be changed according to the duty ratio D.

[0145] In each of the above embodiments, the rotation threshold value N1 does not have to be a value smaller than the rotation reference value N0. Furthermore, the rotation threshold value N1 may be a value determined in advance regardless of the braking torque T when the holding ASC is performed. In the above third and fourth embodiments, the larger threshold value N3 may be a value smaller than the rotation reference value N0 as long as it is a value larger than the rotation threshold value N1.

[0146] In each of the above embodiments, current sensor 28 does not have to detect the current flowing through winding 12a for all three phases. For example, current sensor 28 may output detection signals for two of the three phases, a current calculation unit of control device 40 may calculate the phase currents for the two phases corresponding to the detection signals, and the phase current for the remaining phase may be estimated from the phase currents for the two phases.

[0147] In each of the above embodiments, the control device 40 is provided by a control system including at least one computer. The control system includes at least one processor (hardware processor) that is hardware. The hardware processor can be provided by the following (i), (ii), or (iii).

[0148] (i) A hardware processor may be a hardware logic circuit. In this case, the computer is provided by digital circuits including a number of programmed logic units (gate circuits). The digital circuits may include a memory that stores at least one of a program and data. The computer may be provided by analog circuits. The computer may be provided by a combination of digital and analog circuits.

[0149] (ii) The hardware processor may be at least one processor core that executes a program stored in at least one memory. In this case, the computer is provided with at least one memory and at least one processor core. The processor core is referred to as a CPU, for example. The memory is also referred to as a storage medium. The memory is a non-transitive and tangible storage medium that non-transiently stores "at least one of a program and data" that can be read by the processor.

[0150] (iii) A hardware processor may be a combination of (i) above and (ii) above, where (i) and (ii) are located on different chips or on a common chip.

[0151] That is, at least one of the means and functions provided by the control device 40 can be provided by hardware alone, software alone, or a combination thereof.

[0152] In each of the above embodiments, in the motor 12, the stator may be configured to include permanent magnets that form a field magnet, and the rotor may be configured to include windings 12a that form an armature.

[0153] In each of the above embodiments, the vehicle equipped with the power conversion device 13 includes a passenger car, a bus, a construction vehicle, an agricultural machine vehicle, etc. A vehicle is one type of moving body, and the moving body equipped with the power conversion device 13 includes a train, an airplane, a ship, etc., in addition to a vehicle. The power conversion device 13 includes an inverter device and a converter device. The converter device includes an AC input / DC output power supply device, a DC input / DC output power supply device, an AC input / AC output power supply device, etc.

[0154] For example, in the fifth embodiment, the power conversion system 50 may be mounted on a moving object having a plurality of drive targets. For example, the power conversion system 50 may be mounted on an airplane having a plurality of rotors. In this configuration, one set of motor 12 and inverter 30 is provided for one rotor that is a drive target. The control device 40 drives the plurality of rotors by controlling the plurality of inverters 30. [Explanation of symbols]

[0155] 11...battery as power supply unit, 12...motor, 13...power conversion device, 30...inverter as power conversion unit, 301...first inverter as power conversion unit and target conversion unit, 302...second inverter as power conversion unit and target conversion unit, 31...arm circuit, 32a...upper arm switch, 32b...lower arm switch, 50...power conversion system, D...duty ratio, Nm...motor rotation speed as rotation speed, N1...intermittent threshold Rotation threshold as a value, N2...small side threshold, N3...large side threshold, P...carrier period, S101...abnormality judgment unit, S104...duty setting unit, S105...one-side on intermittent unit, S106...one-side on holding unit, S202...all off unit and small side off unit, S303...all off unit and large side off unit, S402...all off unit and small side off unit, S404...all off unit and large side off unit, S501...abnormality judgment unit, S506...sequence setting unit, S507...target intermittent unit.

Claims

1. A power conversion device (13) that converts power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), Regarding the power conversion unit, when one of the upper arm switch (32 a) on the high potential side and the lower arm switch (32 b) on the low potential side is turned on and the other is turned off for all of the multiple arm circuits (31) connected in parallel with each other, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether an abnormality has occurred in the power conversion unit; a one-on interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly transition the power conversion unit to the one-on state when the abnormality determination unit determines that an abnormality has occurred; a duty setting unit (S104) that variably sets a ratio of a time during which the power conversion unit is in the one-side on state per unit time as a duty ratio (D); Equipped with the half-on interruption unit performs the interruption process in accordance with the duty ratio, The duty setting unit sets the duty ratio to a smaller value as the rotation speed (Nm) of the motor decreases.

2. The power conversion device according to claim 1 , wherein the one-on intermittent switching unit outputs, as the intermittent processing, a command to the power conversion unit to intermittently repeat the one-on state at a period corresponding to a carrier period (P) of a carrier wave.

3. A power conversion device (13) that converts power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), Regarding the power conversion unit, when one of the upper arm switch (32 a) on the high potential side and the lower arm switch (32 b) on the low potential side is turned on and the other is turned off for all of the multiple arm circuits (31) connected in parallel with each other, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether an abnormality has occurred in the power conversion unit; a one-on interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly transition the power conversion unit to the one-on state when the abnormality determination unit determines that an abnormality has occurred; Equipped with The single-on intermittent operation unit outputs, as the intermittent processing, a command to the power conversion unit to intermittently repeat the single-on state at a period corresponding to a carrier period (P) of a carrier wave.

4. The power conversion device according to any one of claims 1 to 3, wherein the one-side on interruption unit performs the interruption processing when the rotation speed (Nm) of the motor is equal to or lower than a predetermined interruption threshold (N1).

5. The power conversion device according to claim 4, further comprising a one-on holding unit (S106) that outputs a command to the power conversion device to transition and hold the power conversion unit in the one-on state when the abnormality determination unit determines that an abnormality has occurred and the rotation speed is not equal to or less than the intermittent threshold value.

6. A power conversion device (13) that converts power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), Regarding the power conversion unit, when one of the upper arm switch (32 a) on the high potential side and the lower arm switch (32 b) on the low potential side is turned on and the other is turned off for all of the multiple arm circuits (31) connected in parallel with each other, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether an abnormality has occurred in the power conversion unit; a single-on interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly transition the power conversion unit to the single-on state when the abnormality determination unit determines that an abnormality has occurred and the rotation speed (Nm) of the motor is equal to or lower than a predetermined interruption threshold value (N1); a one-on holding unit (S106) that outputs a command to the power conversion device to transition and hold the power conversion unit in the one-on state when the abnormality determination unit determines that an abnormality has occurred and the rotation speed is not equal to or less than the intermittence threshold; A power conversion device comprising:

7. A power conversion device as described in any one of claims 4 to 6, further comprising a full-off unit (S202, S303, S402, S404) that outputs a command to the power conversion device to perform a full-off operation in which the power conversion unit transitions to a full-off state in which both the upper arm switch and the lower arm switch are turned off for all of the multiple arm circuits when the abnormality determination unit determines that an abnormality has occurred, in accordance with the rotation speed.

8. The all-off portion is The power conversion device according to claim 7, further comprising a small side off unit (S202, S402) that outputs a command to the power conversion device to perform the full off when the rotation speed is equal to or less than a small side threshold (N2) that is smaller than the intermittent threshold.

9. A power conversion device (13) that converts power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), Regarding the power conversion unit, when one of the upper arm switch (32 a) on the high potential side and the lower arm switch (32 b) on the low potential side is turned on and the other is turned off for all of the multiple arm circuits (31) connected in parallel with each other, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether an abnormality has occurred in the power conversion unit; a single-on interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly transition the power conversion unit to the single-on state when the abnormality determination unit determines that an abnormality has occurred and the rotation speed (Nm) of the motor is equal to or lower than a predetermined interruption threshold value (N1); an all-off unit (S202, S303, S402, S404) that outputs a command to the power conversion device to perform all-off in which the power conversion unit transitions to an all-off state in which both the upper arm switch and the lower arm switch are turned off for all of the multiple arm circuits when the abnormality determination unit determines that an abnormality has occurred, in accordance with the rotation speed; Equipped with The all-off portion is A power conversion device comprising a small side off unit (S202, S402) that outputs a command to the power conversion device to perform the full off when the rotation speed is equal to or less than a small side threshold (N2) that is smaller than the intermittent threshold.

10. The all-off portion is A power conversion device according to any one of claims 7 to 9, further comprising a large side off unit (S303, S404) that outputs a command to the power conversion device to perform the full off when the rotation speed is equal to or less than a large side threshold (N3) that is greater than the intermittent threshold.

11. A power conversion device (13) that converts power supplied from a power source unit (11) to a motor (12) from direct current to alternating current by a power conversion unit (30), Regarding the power conversion unit, when one of the upper arm switch (32 a) on the high potential side and the lower arm switch (32 b) on the low potential side is turned on and the other is turned off for all of the multiple arm circuits (31) connected in parallel with each other, this is referred to as a one-on state. An abnormality determination unit (S101) that determines whether an abnormality has occurred in the power conversion unit; a single-on interruption unit (S105) that performs an interruption process to output a command to the power conversion unit to repeatedly transition the power conversion unit to the single-on state when the abnormality determination unit determines that an abnormality has occurred and the rotation speed (Nm) of the motor is equal to or lower than a predetermined interruption threshold value (N1); an all-off unit (S202, S303, S402, S404) that outputs a command to the power conversion device to perform all-off in which the power conversion unit transitions to an all-off state in which both the upper arm switch and the lower arm switch are turned off for all of the multiple arm circuits when the abnormality determination unit determines that an abnormality has occurred, in accordance with the rotation speed; Equipped with The all-off portion is A power conversion device comprising a large side off unit (S303, S404) that outputs a command to the power conversion device to perform the full off when the rotation speed is equal to or less than a large side threshold (N3) that is greater than the intermittent threshold.

12. A power conversion device as described in any one of claims 1 to 11, wherein the single-on interruption unit outputs a command to the power conversion device to repeatedly transition the power conversion unit alternately between the single-on state and a released state in which the single-on state is released as the interruption processing.

13. a duty setting unit (S104) that variably sets the ratio of the time during which the power conversion unit is in the one-side on state per unit time as a duty ratio (D); Equipped with The power conversion device according to claim 3 , wherein the half-on interruption unit performs the interruption process in accordance with the duty ratio.

14. A power conversion system (50) for converting power supplied from a power source unit (11) to a plurality of motors (12) from direct current to alternating current for each of the motors by a plurality of power conversion units (30, 301, 302), Regarding the power conversion unit, when one of the upper arm switch (32 a) on the high potential side and the lower arm switch (32 b) on the low potential side is turned on and the other is turned off for all of the multiple arm circuits (31) connected in parallel with each other, this is referred to as a one-on state. An abnormality determination unit (S501) that determines whether or not an abnormality has occurred for each of the plurality of power conversion units; an order setting unit (S506) that, when it is determined by the abnormality determination unit that an abnormality has occurred in at least one of the power conversion units, sets at least two power conversion units including the power conversion unit determined to have an abnormality as at least two target conversion units (301, 302) and sets an order in which the at least two target conversion units are to be shifted to the one-on state; A target intermittent unit (S507) that performs an intermittent process for at least two of the target conversion units in parallel, the intermittent process outputting a command to the power conversion unit to intermittently and repeatedly transition the power conversion unit to the one-on state by repeatedly transitioning at least two of the target conversion units to the one-on state in the order set by the order setting unit; A power conversion system comprising:

15. 15. The power conversion system according to claim 14, wherein the target interruption unit outputs a command to the power conversion unit to perform the interruption process in parallel for the at least two power conversion units so that periods during which the at least two power conversion units transition to the one-on state are shifted from each other.

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