JP2022037658A - Power conversion apparatus - Google Patents

Abstract

To provide a power conversion apparatus capable of suppressing heating with occurrence of abnormality relating to a power conversion unit.SOLUTION: A control device performs inverter control processing while defining an inverter as a controlled object. In the inverter control processing, in a case where a motor rotation number Nm achieves a rotation threshold Nb and a motor temperature Tm is higher than a temperature threshold Tb on a situation that inverter abnormality occurs, the control device proceeds to a step S106 and performs target time processing. In the target time processing, a target time TDasc is set in accordance with the motor rotation number Nm and the motor temperature Tm. After delay until a delay time TD achieves the target time TDasc in a step S107, ASC is executed in a step S108. By executing the ASC, in the inverter, one of IGBT of an upper arm and IGBT of a lower arm is switched to an ON state regarding all a plurality of upper/lower arm circuits.SELECTED DRAWING: Figure 7

Description

The disclosure herein relates to a power converter.

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 an arm circuit provided for each of the three phases. In these arm circuits, the switching element on the power supply line side and the switching element on the ground 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 to each other, and the switching elements on the ground line side in each arm circuit are connected in parallel to each other.

When a short circuit occurs in the switching element in the inverter, the control device properly uses 1-phase short-circuit control and 3-phase on control according to the rotation speed of the motor. The one-phase short-circuit control is a process of turning on a switching element connected in series with a switching element in which a short circuit has occurred. The three-phase on control is a process of turning on all switching elements connected in parallel to the switching element in which a short circuit has occurred. The control device performs, for example, one-phase short-circuit control when the rotation speed of the motor is in the low rotation speed range, and performs three-phase on control when the rotation speed of the motor is in the high rotation speed range.

Japanese Unexamined Patent Publication No. 2009-195026

In Patent Document 1, since the control device properly uses one-phase short-circuit control and three-phase on-control according to the rotation speed of the motor, in a situation where the rotation speed of the motor is in the high rotation speed range, it is prompt after a short circuit of the switching element occurs. Three-phase on control will be performed. In the inverter, the three-phase on-control is performed so that the current flows through all the switching elements connected in parallel to each other including the switching element in which the short circuit occurs. In this state, if the counter electromotive force of the motor is increased to some extent due to the fact that the rotation speed of the motor is in the high rotation speed range, the current flowing through the switching element becomes large, and the heat generated by the switching element or the like increases. There is concern that the inverter will generate heat. For example, when increasing the output of a motor, it is considered that the counter electromotive force of the motor increases and the inverter tends to generate heat.

A main object of the present disclosure is to provide a power conversion device capable of suppressing heat generation due to an abnormality in a power conversion unit.

The plurality of aspects disclosed herein employ different technical means to achieve their respective objectives. Further, the scope of claims and the reference numerals in parentheses described in this section are examples showing the correspondence with the specific means described in the embodiment described later as one embodiment, and limit the technical scope. is not it.

In order to achieve the above objectives, one aspect disclosed is:
A power conversion device (13) that converts the power supplied from the power supply unit (11) to the motor (12) from direct current to alternating current by the power conversion unit (30).
When an abnormality occurs in the power conversion unit, the power conversion unit is connected to the upper arm switch (32a) on the high potential side and the lower arm switch on the low potential side for all of the plurality of arm circuits (31) connected in parallel to each other. A state transition unit (S108) that shifts to a target state in which one of (32b) is turned on and the other is turned off.
A delay unit (S107) that delays the transition of the power conversion unit to the target state by the state transition unit by at least the target time (TDasc) from the occurrence of an abnormality in the power conversion unit.
It is a power conversion device equipped with.

Regarding the power conversion device, the finding that irreversible demagnetization of the permanent magnet is likely to occur in the motor when the power conversion unit is in the target state and the d-axis current becomes large on the negative side was obtained by tests and the like. .. In addition to this finding, if the elapsed time until the power conversion unit is switched to the target state after the occurrence of an abnormality in the power conversion unit is long to some extent, the d-axis current after switching the power conversion unit to the target state becomes large on the negative side. The finding that it is easy was obtained by tests and the like.

With respect to these findings, according to the above aspect, the power conversion unit shifts to the target state when the target time elapses after the abnormality occurs in the power conversion unit. Therefore, the d-axis current after the power conversion unit shifts to the target state tends to increase to the negative side, and the permanent magnet tends to be irreversibly demagnetized accordingly. When the permanent magnet is irreversibly demagnetized, the counter electromotive force of the motor is reduced, so that the current flowing through the power conversion unit in the target state is too large and the upper arm switch and lower arm switch are less likely to generate heat. .. Therefore, it is possible to suppress heat generation due to the occurrence of an abnormality in the power conversion unit.

The figure which shows the structure of the drive system in 1st Embodiment. A block diagram showing the electrical configuration of the control unit. The figure which shows the time change of the d-axis current and each phase current before and after ASC. The figure which shows the back electromotive force of a motor before and after ASC. The figure which shows the relationship between the back electromotive force of a motor, d-axis current, and each phase current after ASC execution. The figure which shows the relationship between the electromotive force of a motor, the d-axis current, and a motor temperature after ASC execution. The flowchart which shows the procedure of the inverter control processing. A flowchart showing the procedure of target time processing. The figure which shows the relationship between the deviation time and d-axis current after ASC execution in 2nd Embodiment. The flowchart which shows the procedure of the inverter control processing.

Hereinafter, a plurality of embodiments for carrying out the present disclosure will be described with reference to the drawings. In each form, the same reference numerals may be given to the parts corresponding to the matters described in the preceding forms, and duplicate explanations may be omitted. When only a part of the configuration is described in each form, other forms described above can be applied to the other parts of the configuration. Not only the combinations of the parts that clearly indicate that they can be combined in each embodiment, but also the parts of the embodiments that are not explicitly combined if there is no problem in the combination. It is also possible.

<First Embodiment>
The drive system 10 shown in FIG. 1 is mounted on a vehicle such as an electric vehicle (EV), a hybrid vehicle (HV), or a fuel cell vehicle. The drive system 10 includes 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.

The battery 11 is a DC voltage source composed of a rechargeable and dischargeable secondary battery, and corresponds to a power supply unit that supplies electric power to the motor 12 via a power conversion device 13. The secondary battery is, for example, a lithium ion battery or a nickel hydrogen battery. The battery 11 supplies a high voltage (for example, several 100V) to the inverter 30.

The motor 12 is a three-phase alternating current type rotary electric machine. The motor 12 has a U phase, a V phase, and a W phase as three phases. The motor 12 functions as an electric motor that is a traveling drive source of the vehicle. The motor 12 functions as a generator during regeneration. The motor 12 has a winding 12a forming an armature and a permanent magnet 12b forming a field magnet. In this motor 12, a rotor is configured to include a permanent magnet 12b, and a stator is configured to include a winding 12a. The motor 12 can also be referred to as a motor generator or an electric motor.

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

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 power line on the high potential side and an N line 26 which is a power line on the low potential side. 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. Further, 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 a bus bar or the like.

In the power conversion device 13, a switch 22 is provided between the smoothing capacitor 21 and the battery 11. The switch 22 is formed by a switch, a relay, or the like that can shift between an open state and a closed state, and is provided in each of the P line 25 and the N line 26. In the P line 25, a switch 22 is provided between the positive electrode of the battery 11 and the positive electrode of the smoothing capacitor 21, and in the N line 26, the switch 22 is provided between the negative electrode of the battery 11 and the negative electrode of the smoothing capacitor 21. Is provided. When the switch 22 is closed, the battery 11 is electrically connected to the smoothing capacitor 21 and the inverter 30. When the switch 22 is opened, the battery 11 is electrically cut off from the smoothing capacitor 21 and the inverter 30.

The switch 22 is basically closed when the vehicle switch such as the ignition switch is on, and is open when the vehicle switch is off. For example, when the vehicle is in a traveling state, the switch 22 is basically in a closed state. The switch 22 can be referred to as a system main relay. Further, regarding the switch 22, the closed state may be referred to as a conduction state, and the open state may be referred to as a cutoff state. Further, when the switch 22 is in the closed state, the battery 11 and the smoothing capacitor 21 are in a conductive state, and when the switch 22 is in the open state, the continuity between the battery 11 and the smoothing capacitor 21 is cut off. It is in a state.

In the present embodiment, the switch 22 is included in the power conversion device 13, but the switch 22 may not be included in the power conversion device 13. For example, the switch 22 may be provided between the power conversion device 13 and the battery 11. Further, the switch 22 may be provided only on the P line 25. That is, the switch 22 may be provided at least on the P line 25 out of the P line 25 and the N line 26.

The power conversion device 13 is provided with a voltage sensor (not shown). Examples of the voltage sensor include a voltage sensor that detects the voltage of the battery 11 and a voltage sensor that detects the voltage of the smoothing capacitor 21.

The inverter 30 is a DC-AC conversion circuit. The inverter 30 is configured to include an upper and lower arm circuit 31 for three phases. The upper and lower arm circuit 31 may be referred to as a leg. The upper and lower arm circuit 31 has an upper arm 31a and a lower arm 31b, respectively. 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. The connection point between the upper arm 31a and the lower arm 31b is connected to the winding 12a of the corresponding phase in the motor 12 via the output line 27. The upper and lower 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. In the power conversion device 13, the output line 27 is formed by a bus bar or the like.

The arms 31a and 31b have n-channel type IGBTs 32a and 32b which are switching elements and diodes 33a and 33b for reflux, respectively. Hereinafter, the diodes 33a and 33b will be referred to as FWD33a and 33b. The IGBT 32a and FWD33a are included in the upper arm 31a, and the IGBT 32b and FWD33b are included in the lower arm 31b. The FWD 33a and 33b are connected to the IGBTs 32a and 32b in antiparallel. In the upper arm 31a, the collector of the IGBT 32a is connected to the P line 25. In the lower arm 31b, the emitter of the IGBT 32b is connected to the N line 26. Then, the emitter of the IGBT 32a in the upper arm 31a and the collector of the IGBT 32b in the lower arm 31b are connected to each other. The anodes of the FWD 33a, 33b are connected to the emitters of the corresponding IGBTs 32a, 32b, and the cathode is connected to the collector.

The inverter 30 is composed of a semiconductor device (not shown). Semiconductor devices are sometimes referred to as semiconductor modules. The semiconductor device has a plurality of semiconductor elements. In a semiconductor element, the element is formed on a semiconductor substrate made of silicon (Si), a wide bandgap semiconductor having a wider bandgap than silicon, or the like. A semiconductor element is a semiconductor chip on which the element is formed. Wide bandgap semiconductors are, for example, silicon carbide (SiC), gallium nitride (GaN), gallium oxide (Ga2O3), and diamond.

In the present embodiment, one semiconductor element is formed with an IGBT and an FWD constituting one arm. That is, RC (Reverse Conducting) -IGBT is formed. The semiconductor device has six semiconductor elements constituting each arm. The upper and lower arm circuits 31 correspond to the arm circuit, the IGBT 32a of the upper arm 31a corresponds to the upper arm switch, and the IGBT 32b of the lower arm 31b corresponds to the lower arm switch.

The inverter 30 converts the DC voltage into an AC voltage according to the switching control by the control device 40, and outputs the DC voltage to the motor 12. As a result, the motor 12 operates so as to generate a predetermined rotational torque. That is, the inverter 30 converts the DC power from the battery 11 into three-phase AC power, which corresponds to a power conversion unit. The inverter 30 converts the AC voltage generated by the motor 12 by receiving the rotational force from the drive wheels into a DC voltage according to the switching control by the control device 40 during the regenerative braking of the vehicle, and outputs the AC voltage to the P line 25. In this way, the inverter 30 performs bidirectional power conversion between the battery 11 and the motor 12.

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

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 a signal input from various sensors such as a rotation sensor 29, and responds to the drive command. Let the IGBTs 32a and 32b perform on drive and off drive. The control device 40 corresponds to a power conversion control device. The IGBTs 32a and 32b can be switched between an on state and an off state, and are shifted to the on state with the on drive and to the off state with the off drive.

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.

The current sensor 28 is a current detection unit that detects the current flowing through the motor 12. The current sensor 28 outputs a detection signal corresponding to the current flowing through each of the three-phase windings 12a to the control device 40. The current sensor 28 of the present embodiment is provided for the winding 12a by being provided for the output line 27, and detects the current flowing through the output line 27 to detect the current flowing through the winding 12a. To detect. The current sensor 28 discretely samples the current flowing through the winding 12a at a predetermined sampling cycle, and outputs the discrete signal as a detection signal. The current flowing through the winding 12a can also be referred to as an armature current.

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 includes, for example, an encoder, a resolver, and the like.

The control device 40 shown in FIG. 2 performs vector control of the motor 12 via the inverter 30. In the vector control, the three-phase AC coordinates indicated by the U phase, the V phase, and the W phase are converted into the dq coordinates indicated by the d-axis and the q-axis. The dq coordinates are, for example, rotation coordinates defined by these d-axis and q-axis, with the direction from the S pole to the N pole of the rotor as the d-axis and the direction orthogonal to the d-axis as the q-axis.

The control device 40 has a command unit 41, a three-phase 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 three-phase conversion unit 46 as functional blocks. .. These functional blocks may be configured in terms of hardware by at least one IC or the like, or may be executed by a combination of software execution by a processor and hardware.

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

The motor rotation speed Nm detected by the rotation sensor 29 is input to the three-phase two-phase conversion unit 42. The 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 rotation speed of the motor 12 per unit time, and is a value indicating the rotation speed.

The three-phase two-phase conversion unit 42 converts the U-phase current Iu, V-phase current Iv, and W-phase current Iw of the three-phase AC coordinate system into dq coordinates, and the d-axis current Id and q-axis current of the dq coordinate system. Calculate Iq. 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 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 two-phase conversion unit 42 converts each phase current Iu, Iv, Iw into dq coordinates with reference to the motor rotation speed Nm, and calculates 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 the d-axis subtraction unit 43.

The three-phase two-phase conversion unit 42 corresponds to the coordinate conversion unit. Further, the d-axis current Id and the q-axis current Iq can also be referred to as an actual d-axis current or an actual q-axis current, assuming that they are actual currents obtained by converting the detected values of the phase currents Iu, Iv, and Iw into coordinates. Further, the d-axis current Id may be referred to as a field current, and the q-axis current may be referred to as a drive current.

The command unit 41 sets the values to be targeted for each of the d-axis current Id and the q-axis current Iq as the d-axis current command value Id * and the q-axis current command value Iq *. As for the command values Id * and Iq * set by the command unit 41, the d-axis current command value Id * is input to the d-axis subtraction unit 43, and the q-axis current command value Iq * is input to the q-axis subtraction unit 44. .. A torque command value is input to the command unit 41 as a signal from the host ECU as the rotational torque to be generated by the motor 12. The command unit 41 sets the command values Id * and Iq * according to the torque command value when the power is supplied from the battery 11 to the motor 12.

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. These d-axis current deviation and q-axis current deviation are input to the current control unit 45.

The current control unit 45 calculates the d-axis voltage command value Vd * and the q-axis voltage command value Vq * so that the d-axis current deviation and the q-axis current deviation become zero for the dq coordinate system. The current control unit 45 performs feedback control 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 *, and performs a d-axis voltage command. The value Vd * and the q-axis voltage command value Vq * are calculated. The current control unit 45 performs, for example, PI control as feedback control. The d-axis voltage command value Vd * and the q-axis voltage command value Vq * are input to the two-phase three-phase conversion unit 46.

The two-phase three-phase conversion unit 46 converts the d-axis voltage command value Vd * and the q-axis voltage command value Vq * of the dq coordinate system into three-phase AC coordinates, and U-phase voltage command value Vu of the three-phase coordinate system. *, V-phase voltage command value Vv * and W-phase voltage command value Vw * are calculated. These voltage command values Vu *, Vv *, and Vw * are voltage values to be output to each of the three-phase windings 12a, 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 control device 40 has a PWM signal generation unit (not shown) as a functional block. The PWM signal generation unit uses the voltage command values Vu *, Vv *, and Vw * to generate PWM signals for driving the IGBTs 32a and 32b. The control device 40 causes the IGBTs 32a and 32b to be driven on and off in response to the PWM signal, so that the voltage corresponding to the voltage command values Vu *, Vv *, Vw * is U-phase, V-phase, and W-phase. It is applied to each winding 12a of.

In the drive system 10, when an inverter abnormality, which is an abnormality of the inverter 30, occurs while the motor 12 is driven and rotated by power supply from the battery 11 when the vehicle is running, it is secondary to the inverter abnormality. There is concern that anomalies will occur. For example, as an inverter abnormality, there is a short-circuit abnormality in which the IGBTs 32a and 32b as switching elements are short-circuited. Here, a situation in which the IGBTs 32a and 32b unintentionally shift to the on state and a situation in which the IGBTs 32a and 32b are unintentionally held in the on state are referred to as a short-circuit abnormality. When a short-circuit abnormality occurs in the IGBTs 32a and 32b, a control failure occurs in which the power conversion device 13 does not operate as instructed by the control device 40, such as the IGBTs 32a and 32b ordered by the control device 40 to be off-driven are not driven off. Is a concern. When a control failure occurs, a secondary abnormality such as an overvoltage of auxiliary equipment such as a voltage sensor or a smoothing capacitor 21 due to the counter electromotive force of the motor 12 or an overcurrent flowing through the inverter 30 occurs in the drive system. It is considered that it is likely to occur at 10.

On the other hand, the control device 40 performs an active short circuit with respect to the inverter 30 when an inverter abnormality occurs. Hereinafter, the active short circuit will be referred to as ASC. ASC is realized by the control device 40 driving one of the IGBT 32a of the upper arm 31a and the IGBT 32b of the lower arm 31b on for all three phases and the other off driving for all three phases. When 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 the target state.

Regarding ASC, it was found by tests and simulations that irreversible demagnetization of the permanent magnet 12b is likely to occur in the motor 12 when the inverter 30 is in the ASC state and the d-axis current is large on the Id side. .. Further, it has been found that if the elapsed time until the inverter 30 is switched to the ASC state after the occurrence of the inverter abnormality is long to some extent, the d-axis current Id after the inverter 30 is switched to the ASC state tends to increase to the negative side. Obtained by simulation or the like. These findings will be described with reference to FIGS. 3 to 6.

First, irreversible demagnetization will be described. In FIG. 3, the inverter 30 is normally driven from the timing t1 to just before the timing t2. Then, an inverter abnormality occurs at the timing t2, and the control device 40 starts ASC with the occurrence of the inverter abnormality. When the period from the occurrence of the inverter abnormality to the start of ASC is referred to as the delay time TD, the delay time TD is sufficiently smaller than, for example, the period of timings t1 to t2. Therefore, the delay time TD is not shown in FIG. The d-axis current Id has a negative value before and after the inverter abnormality occurs.

At the timing t2, the inverter 30 switches to the ASC state, and the d-axis current Id momentarily increases to the negative side. The d-axis current Id further decreases sharply from a negative value smaller than zero, and the absolute value of the d-axis current Id rapidly increases to reach the maximum value Idmax. With respect to the d-axis current Id, the amplitude also rapidly increases with the rapid increase in the absolute value, and then the amplitude gradually decreases.

At the timing t3, the amplitude of the d-axis current Id decreases and the d-axis current Id almost converges to the steady value. The d-axis current Id at the timing t3 is larger on the zero side than the d-axis current Id at the timing t1 in which the inverter abnormality does not occur. In this case, the absolute value of the d-axis current Id decreases by the difference ΔId before and after ASC.

Each phase current Iu, Iv, Iw momentarily increases to the positive side or the negative side at the timing t2. After that, the amplitudes of the respective phase currents Iu, Iv, and Iw gradually decrease in the same manner as the d-axis current Id, and the decrease in the amplitudes almost converges at the timing t3. For each phase current Iu, Iv, Iw, the amplitude at the timing t3 is smaller than the amplitude at the timing t1 where the inverter abnormality does not occur. In this case, the amplitudes of the respective phase currents Iu, Iv, and Iw decrease by the difference ΔI before and after the ASC. In addition, each phase current Iu, Iv, Iw can also be referred to as a three-phase current.

In this way, the reason why the absolute value of the d-axis current Id and the amplitudes of the phase currents Iu, Iv, and Iw decrease after the start of ASC is that the d-axis current Id increases to the negative side due to the execution of ASC. This is because a demagnetizing field is applied to the permanent magnet 12b of the above, and demagnetization of the permanent magnet 12b occurs. When the maximum value Idmax at which the absolute value of the d-axis current Id has reached is sufficiently large, the demagnetizing field applied to the permanent magnet 12b becomes sufficiently strong, and the demagnetization generated by the permanent magnet 12b is irreversible irreversible demagnetization. It is thought that it is easy to become.

Due to the irreversible demagnetization of the permanent magnet 12b caused by the execution of ASC, as shown in FIG. 4, the back electromotive force BEMF of the motor 12 is after the start of ASC as compared with the timing t1 in which the inverter abnormality does not occur. The amplitude is smaller at the timing t3 of. In FIG. 4, the horizontal axis shows the electric angle θ, and the vertical axis shows the back electromotive force BEMF of the motor 12.

Next, the relationship between the delay time TD and the d-axis current Id will be described. In FIG. 5, the absolute value [A] of the maximum value Idmax of the d-axis current Id and the effective value [Arms] of the phase currents Iu, Iv, and Iw at the timing t3 after the start of ASC are on the vertical axis. The delay time TD is on the horizontal axis. As shown in FIG. 5, the longer the delay time TD, the larger the maximum value Idmax of the d-axis current Id. On the other hand, each phase current Iu, Iv, Iw has a substantially constant value regardless of the delay time TD. This is because as the delay time TD is longer, the d-axis current Id increases rapidly with the execution of ASC, and irreversible demagnetization of the permanent magnet 12b is likely to occur, while the increase of each phase current Iu, Iv, Iw occurs. It shows that it is difficult.

Subsequently, the relationship between the back electromotive force BEMF of the motor 12 and the motor temperature Tm, which is the temperature of the motor 12, will be described. In the motor 12, if the motor temperature Tm is different, the back electromotive force BEMF is also different. In this embodiment, the permanent magnet 12b of the motor 12 is formed of a neodymium magnet. Neodymium magnets are a type of rare earth magnets and have the property that the lower the temperature, the stronger the magnetic force. In the motor 12, the lower the motor temperature Tm, the larger the back electromotive force BEMF tends to be.

As shown in FIG. 6, in the motor 12, the relationship between the maximum value Idmax of the d-axis current Id and the back electromotive force BEMF of the motor 12 differs depending on the motor temperature Tm. In FIG. 6, on the horizontal axis, the maximum value Idmax of the d-axis current Id is shown on the horizontal axis as a negative value instead of an absolute value. The vertical axis shows the back electromotive force BEMF of the motor 12 after the irreversible demagnetization of the permanent magnet 12b by the ASC occurs. That is, the vertical axis shows the back electromotive force BEMF at the timing t3. FIG. 6 shows the relationship between the maximum value Idmax and the back electromotive force BEMF for each of the cases where the motor temperature Tm is the first temperature Tm1, the second temperature Tm2, and the third temperature Tm3. Among these temperatures Tm1, Tm2, and Tm3, the first temperature Tm1 is the highest temperature, and the third temperature Tm3 is the lowest temperature.

In the motor 12, regardless of whether the motor temperature Tm is at any of the temperatures Tm1, Tm2, and Tm3, when the maximum value Idmax of the d-axis current Id increases to the negative side, the back electromotive force BEMF after irreversible demagnetization decreases. On the other hand, the lower the motor temperature Tm, the less likely it is that the permanent magnet 12b is demagnetized. Therefore, the lower the motor temperature Tm, the more irreversible demagnetization even if the maximum value Idmax of the d-axis current Id is increased to the negative side. Later back electromotive force BEMF is unlikely to decrease.

Next, the relationship between the back electromotive force BEMF of the motor 12 and the motor rotation speed Nm will be described. In the motor 12, if the motor rotation speed Nm is different, the back electromotive force BEMF is also different. The larger the motor rotation speed Nm, the larger the back electromotive force BEMF, and the motor rotation speed Nm and the motor rotation speed Nm are in a proportional relationship. Further, the relationship between the maximum value Idmax of the d-axis current Id and the back electromotive force BEMF differs depending on the motor rotation speed Nm. For example, similarly to the motor temperature Tm, when the maximum value Idmax of the d-axis current Id increases to the negative side regardless of the motor rotation speed Nm, the back electromotive force BEMF after irreversible demagnetization decreases. Further, the larger the motor rotation speed Nm, the larger the back electromotive force BEMF. Therefore, in order to increase the amount of reduction in the back electromotive force BEMF, it is necessary to increase the maximum value Idmax of the d-axis current Id to the negative side as the motor rotation speed Nm increases.

The control device 40 performs ASC so that the back electromotive force BEMF is reduced when an inverter abnormality occurs. The control device 40 performs a process for performing ASC in the inverter control process for performing drive control of the inverter 30. This inverter control process will be described with reference to the flowchart of FIG. 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.

In FIG. 7, in step S101, it is determined whether or not the motor temperature Tm is equal to or less than a predetermined temperature threshold value Tb. The temperature threshold value Tb is information acquired by a test, simulation, or the like, and is stored in a storage unit of the control device 40. As described in the explanation of FIG. 6, in order to generate irreversible demagnetization of the permanent magnet 12b and reduce the back electromotive force BEMF, it is necessary to increase the maximum value Idmax of the d-axis current Id as the motor temperature Tm is lower. There is. Therefore, if the motor temperature Tm is too low, the permanent magnet 12b is not irreversibly demagnetized even if the maximum value Idmax of the d-axis current Id is increased to exceed the upper limit value, and the back electromotive force BEMF is sufficiently reduced. There is a possibility that it cannot be said. The upper limit of the maximum value Idmax for the d-axis current Id is a value set according to the rated value of the inverter 30 or the like.

Therefore, in this step S101, for the motor temperature Tm, a value at which irreversible demagnetization of the permanent magnet 12b occurs is set as the temperature threshold value Tb within a range in which the maximum value Idmax of the d-axis current Id does not exceed the upper limit value. When the motor temperature Tm is equal to or less than the temperature threshold value Tb, the process proceeds to step S110, assuming that the motor rotation speed Nm is limited even in the normal state. In this case, even if ASC is performed due to the occurrence of an inverter abnormality, the motor temperature Tm is so low that the permanent magnet 12b is not irreversibly demagnetized.

In step S110, the motor limiting process is performed. In this motor limiting process, the motor rotation speed Nm is limited so that the back electromotive force BEMF of the motor 12 is equal to or less than a predetermined reverse threshold value BEMFb [V] (not shown). For example, the lower the current motor temperature Tm, the smaller the target value of the motor rotation speed Nm is set. Then, the command unit 41 sets the d-axis current command value Id * and the q-axis current command value Iq * according to the target value of the motor rotation speed Nm in addition to the torque command value. By performing vector control of the motor 12 according to these current command values Id * and Iq *, the motor rotation speed Nm is limited.

The reverse threshold value BEMFb of the back electromotive force BEMF is the upper limit value of the voltage applied to the inverter 30. As described above, the upper limit of the voltage applied to the inverter 30 is the withstand voltage value of the inverter 30, and the withstand voltage value is set to the withstand voltage value of the component or device having the lowest withstand voltage value in the inverter 30. There is. The inverse threshold value BEMFb is information acquired by a test, simulation, or the like, and is stored in a storage unit of the control device 40.

On the other hand, when the motor temperature Tm is larger than the temperature threshold value Tb, it is highly possible that the back electromotive force BEMF of the motor 12 can be reduced by performing ASC, and the process proceeds to step S102. In step S102, it is determined whether or not an inverter abnormality has occurred. Here, it is determined whether or not the ON drive and the OFF drive of the IGBTs 32a and 32b are normally performed according to the drive command from the control device 40 to the inverter 30. 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 IGBTs 32a and 32b is determined using the comparison result. If it is determined that a short-circuit abnormality has occurred in the IGBTs 32a and 32b, it is assumed that an inverter abnormality has occurred, and the process proceeds to step S103.

In step S103, the motor rotation speed Nm is acquired by using the detection signal of the rotation sensor 29. In step S104, it is determined whether or not the motor rotation speed Nm is equal to or higher than a predetermined rotation threshold value Nb. The rotation threshold value Nb is information acquired by a test, simulation, or the like, and is stored in a storage unit such as a memory in the control device 40. The rotation threshold Nb is limited so that the back electromotive force BEMF of the motor 12 is limited to, for example, a value corresponding to the maximum allowable voltage and the rated voltage of the smoothing capacitor 21 and a value corresponding to the upper limit value of the voltage applied to the inverter 30. It is set. The upper limit of the voltage applied to the inverter 30 is set according to, for example, the rated value of the inverter 30 or the maximum allowable voltage.

The upper limit of the voltage applied to the inverter 30 can also be referred to as the withstand voltage value of the inverter 30. As the withstand voltage value of the inverter 30, the withstand voltage value of the component or device having the lowest withstand voltage value in the inverter 30 is set. For example, if the component having the lowest withstand voltage value in the inverter 30 is the IGBT 32a, 32b, the withstand voltage value is set according to the rated value of the IGBT 32a, 32b and the maximum allowable voltage.

If the motor rotation speed Nm does not reach the rotation threshold Nb, it is unlikely that an overvoltage of the auxiliary equipment or the smoothing capacitor 21 or an overcurrent of the inverter 30 will occur, and the inverter control process is terminated as it is. When the motor rotation speed Nm reaches the rotation threshold value Nb, it is considered that an overvoltage of the auxiliary equipment and the smoothing capacitor 21 and an overcurrent of the inverter 30 may occur, and the process proceeds to step S105.

In step S105, the motor temperature Tm is acquired. In this acquisition process, the motor temperature Tm is acquired as a detection value by using the signals input from the host ECU and various sensors. In this embodiment, it is assumed that the motor temperature Tm and the permanent magnet 12b are substantially the same.

In step S106, the target time processing for setting the target time TDasc for the delay time TD as the target value when the ASC is executed is performed. The target time processing in step S106 will be described with reference to the flowchart of FIG.

In FIG. 8, in step S201, the target value BEMFasc is acquired for the back electromotive force BEMF of the motor 12 as the target value when the ASC is executed. The target value BEMFasc is information acquired by a test, a simulation, or the like, and is stored in a storage unit of the control device 40. Regarding the back electromotive force BEMF, for example, a value corresponding to the maximum allowable voltage and the rated voltage of the smoothing capacitor 21 and a value corresponding to the upper limit value of the voltage applied to the inverter 30 are set as the target value BEMFasc. In this step S201, the target value BEMFasc is read from the storage unit of the control device 40 and acquired. The target value BEMFasc may be variably set to the motor rotation speed Nm or the motor temperature Tm.

In step S202, the first target time TDasc1 is calculated using the motor temperature Tm for the target time TDasc of the delay time TD. The first target time TDasc1 is a target time calculated using the finding that the target time TDasc should be lengthened as the motor temperature Tm is lowered in order to reduce the back electromotive force BEMF. Here, first, the target maximum value Idmax1 of the d-axis current Id is calculated from the target value BEMFasc of the counter electromotive force BEMF and the motor temperature Tm using the temperature correlation information. The temperature correlation information is correlation information showing the correlation between the motor temperature Tm, the back electromotive force BEMF, and the maximum value Idmax of the d-axis current Id, and is stored in the storage unit of the control device 40 as, for example, a map or a function. For example, when the information shown in FIG. 6 is used as the temperature correlation information, if the motor temperature Tm is the second temperature Tm2, the maximum value Idmax of the d-axis current Id intersects the target value BEMFasc on the graph of the second temperature Tm2. The value to be calculated is calculated as the target maximum value Idmax1.

Next, the first target time TDasc1 is calculated from the target maximum value Idmax1 of the d-axis current Id using the time correlation information. The time correlation information is correlation information showing the correlation between the maximum value Idmax of the d-axis current Id and the delay time TD, and is stored in the storage unit of the control device 40 as, for example, a map or a function. For example, when the information shown in FIG. 5 is used as the time correlation information, the value crossing the target maximum value Idmax1 on the flag indicating the maximum value Idmax of the d-axis current Id is calculated as the first target time TDasc1 for the delay time TD. ..

In step S203, the second target time TDasc2 is calculated using the motor rotation speed Nm for the target time TDasc of the delay time TD. The second target time TDasc2 is a target time calculated using the finding that the target time TDasc should be lengthened as the motor rotation speed Nm is larger in order to reduce the back electromotive force BEMF. Here, first, the target maximum value Idmax2 (not shown) of the d-axis current Id is calculated from the target value BEMFasc of the counter electromotive force BEMF and the motor rotation speed Nm using the rotation correlation information. The rotation correlation information is correlation information showing the correlation between the motor rotation speed Nm, the back electromotive force BEMF, and the maximum value Idmax of the d-axis current Id, and is stored in the storage unit of the control device 40 as, for example, a map or a function. ..

Next, the second target time TDasc2 is calculated from the target maximum value Idmax2 of the d-axis current Id using the time correlation information. Here, the second target time TDasc2 is calculated in the same manner as the first target time TDasc1 by using the time correlation information used for calculating the first target time TDasc1.

In step S204, the target time TDasc is calculated according to the first target time TDasc1 calculated from the motor temperature Tm and the second target time TDasc2 calculated from the motor rotation speed Nm. For example, the average value of the first target time TDasc1 and the second target time TDasc2 is calculated, and this average value is set in the target time TDasc. If the first target time TDasc1 and the second target time TDasc2 are used, any method may be adopted for calculating the target time TDasc.

The function of executing the process of step S202 in the control device 40 corresponds to the temperature setting unit, and the function of executing the process of step S203 corresponds to the rotation setting unit. Further, the function of executing the processing of steps S202, S203, and S204 corresponds to the target setting unit.

After the end of step S204, it is assumed that step S106 shown in FIG. 7 is completed, and the process proceeds to step S107. In step S107, it is determined whether or not the delay time TD has reached the target time TDasc. Then, the process of step S107 is repeated until the delay time TD reaches the target time TDasc. When the delay time TD reaches the target time TDasc, the process proceeds to step S108. In this inverter control process, the elapsed time from the timing at which the occurrence of the inverter abnormality is determined in the process in step S101 is measured as the delay time TD.

In step S108, ASC is executed to shift the inverter 30 to the ASC state. Here, one of the IGBT 32a of the upper arm 31a and the IGBT 32b of the lower arm 31b is driven on for all three phases, and the other is driven off for all three phases. In this case, for one of the IGBTs 32a and 32b, the timing for switching to the on state is aligned by the upper and lower arm circuits 31 of all three phases. For the other, the timing of switching to the off state is aligned with the upper and lower arm circuits 31 of all three phases. Further, the timing of switching one of the IGBTs 32a and 32b to the on state and the timing of switching the other to the off state are also arranged.

It should be noted that "aligning" includes that the states of a plurality of IGBTs 32a and 32b can be switched at once, that the switching timings of the plurality of IGBTs 32a and 32b are simultaneous, and that the switching timings are slightly different. There is.

Further, in this step S108, it is determined which of the IGBTs 32a and 32b the short-circuit abnormality has occurred. If only one of the upper arm 31a and the lower arm 31b contains the IGBT in which the short-circuit abnormality has occurred among all the IGBTs 32a and 32b, the rest of the arms 31a and 31b containing the IGBT. Drive all IGBTs on. Then, all the IGBTs that do not include the IGBT are driven off. For example, when a short-circuit abnormality occurs in the IGBT 32a of the upper arm 31a for the U phase, the IGBT 32a of the upper arm 31a is switched to the ON state for the V phase and the W phase. Then, the IGBT 32b of the lower arm 31b is switched to the off state for all three phases.

In step S109, the termination process is performed. In the termination process, it is determined whether or not the back electromotive force BEMF of the motor 12 has decreased to an allowable range with respect to the target value BEMFasc due to the execution of ASC. For example, it is determined whether or not the magnitude of the amplitude of the d-axis current Id after executing ASC is smaller than the predetermined amplitude threshold value, and the difference ΔI before and after ASC is predetermined for each phase current Iu, Iv, Iw. It is determined whether or not the difference is smaller than the difference threshold. Then, when the amplitude of the d-axis current Id becomes smaller than the amplitude threshold value and the difference ΔI becomes smaller than the difference threshold value, it is determined that the back electromotive force BEMF has decreased to an allowable range. At the timing t3 shown in FIG. 3, the d-axis current Id is smaller than the amplitude threshold value, and the d-axis current Id and the phase currents Iu, Iv, and Iw are in a state of converging to a steady value.

When the counter electromotive force BEMF drops to an allowable range, the ASC is terminated on the assumption that the counter electromotive force BEMF has dropped appropriately due to the execution of the ASC. Here, in the inverter 30, all the IGBTs 32a and 32b other than the IGBT in which the short-circuit abnormality has occurred are switched to the off state, and the inverter 30 is shifted to the end state. In the termination process, the switch 22 may be switched to the open state to stop the power supply from the battery 11 to the motor 12.

The function of executing the process of step S107 in the control device 40 corresponds to the delay unit, and the function of executing the process of step S108 corresponds to the state transition unit. The function of executing the process of step S109 corresponds to the end unit, and the function of executing the process of step S110 corresponds to the restriction unit.

Next, changes in the back electromotive force BEMF when the control device 40 performs ASC due to the occurrence of an inverter abnormality will be described with reference to FIGS. 3 and 4.

In FIG. 3, when an inverter abnormality occurs at the timing t2, when the delay time TD reaches the target time TDasc, the control device 40 starts ASC. The amplitude of the d-axis current Id temporarily increases with the start of the ASC, but at the timing t3, the steady-state d-axis current Id is smaller than the d-axis current Id at the timing t1. The amplitude of each phase current Iu, Iv, and Iw also increases temporarily, but the amplitude at the timing t3 in which the steady state is reached is smaller than the amplitude at the timing t1 where the inverter abnormality does not occur. As a result, as shown in FIG. 4, the counter electromotive force BEMF at the timing t3 when the inverter abnormality occurs is smaller than the counter electromotive force BEMF at the timing t1 where the inverter abnormality does not occur.

According to the present embodiment described so far, when an inverter abnormality occurs, the inverter 30 shifts to the ASC state when the delay time TD reaches the target time TDasc. Therefore, the d-axis current Id after the inverter 30 shifts to the ASC state tends to increase to the negative side, and accordingly, the permanent magnet 12b tends to be irreversibly demagnetized in the motor 12. When the permanent magnet 12b is irreversibly demagnetized, the back electromotive force BEMF of the motor 12 is reduced, so that the current flowing through the inverter 30 in the ASC state is too large and the IGBTs 32a, 32b and the like are less likely to generate heat. Therefore, it is possible to suppress heat generation due to the occurrence of an abnormality in the inverter 30.

According to the present embodiment, when the ASC is executed, the control device 40 aligns the timing of switching to the ON state for one of the IGBTs 32a and 32b in all of the plurality of upper and lower arm circuits 31. In this configuration, for example, when the plurality of IGBTs 32a are all switched to the ON state, the same drive command may be generated for all of these IGBTs 32a, so that the processing load of the control device 40 can be reduced. This effect can be similarly exerted when the plurality of IGBTs 32b are all switched to the on state.

When the control device 40 executes ASC, the timing of switching to the off state for one of the IGBTs 32a and 32b is aligned with all of the plurality of upper and lower arm circuits 31. In this configuration, for example, when the plurality of IGBTs 32a are all switched to the off state, the same drive command may be generated for all of these IGBTs 32a, so that the processing load of the control device 40 can be reduced. This effect can be similarly exerted when the plurality of IGBTs 32b are all switched to the off state.

When the motor temperature Tm is equal to or less than the temperature threshold Tb, even if the ASC of the inverter 30 is executed, the maximum value Idmax of the d-axis current Id is insufficient due to the fact that the motor temperature Tm is in the temperature range where the motor temperature Tm is too low. Therefore, there is a concern that irreversible demagnetization of the permanent magnet 12b does not occur. On the other hand, according to the present embodiment, when the motor temperature Tm is equal to or less than the temperature threshold value Tb, the motor rotation speed Nm is limited so that the back electromotive force BEMF is equal to or less than the reverse threshold value BEMFb. Therefore, it is possible to avoid that the maximum value Idmax of the d-axis current Id is insufficient and the permanent magnet 12b is not irreversibly demagnetized even though the ASC is executed. As a result, it is possible to prevent the inverter 30 from generating heat when the ASC is executed.

According to the present embodiment, when the motor temperature Tm is equal to or less than the temperature threshold value Tb, the motor rotation speed Nm is limited according to the motor temperature Tm. Therefore, in limiting the motor rotation speed Nm so that the back electromotive force BEMF is equal to or less than the reverse threshold BEMFb, the larger the motor rotation speed Nm, the larger the back electromotive force BEMF, and the lower the motor temperature Tm. You can take advantage of the relationship that the back electromotive force increases. Therefore, when the motor temperature Tm is equal to or less than the temperature threshold value Tb, the accuracy of limiting the motor rotation speed Nm can be improved.

According to the present embodiment, the reverse threshold value BEMFb of the back electromotive force BEMF is the withstand voltage value of the inverter 30. Therefore, when the motor temperature Tm is equal to or less than the temperature threshold value Tb, it is possible to more reliably suppress that an excessively large voltage for the inverter 30 is applied by the back electromotive force BEMF of the motor 12.

According to the present embodiment, after the inverter 30 shifts to the ASC state, all the IGBTs other than the IGBT in which the abnormality has occurred are switched to the off state, so that the inverter 30 shifts to the terminated state. Therefore, when the back electromotive force BEMF of the motor 12 is reduced by the execution of the ASC, the inverter 30 shifts to the terminated state and the motor 12 rotates by inertia. Therefore, even if an inverter abnormality occurs and ASC is executed, the vehicle can be safely evacuated by shifting the inverter 30 to the terminated state.

According to the present embodiment, the target time TDasc is set according to both the motor rotation speed Nm and the motor temperature Tm. Therefore, the target time TDasc can be set by using both the finding that the target time TDasc becomes longer as the motor rotation speed Nm is larger and the finding that the target time TDasc becomes longer as the motor temperature Tm is lower.

According to the present embodiment, the temperature correlation information is used for setting the target time TDasc, and the temperature correlation information includes the finding that the lower the motor temperature Tm, the longer the target time TDasc. Therefore, by utilizing this knowledge, the target time TDasc can be set accurately from the motor temperature Tm.

According to the present embodiment, the rotation correlation information is used for setting the target time TDasc, and the rotation correlation information includes the finding that the larger the motor rotation speed Nm is, the more the target time TDasc is. Therefore, by utilizing this knowledge, the target time TDasc can be set accurately from the motor rotation speed Nm.

<Second Embodiment>
In the first embodiment, when the ASC of the inverter 30 is executed, the timing for switching one of the IGBTs 32a and 32b to the ON state is aligned for the plurality of upper and lower arm circuits 31, but in the second embodiment, the timing is aligned. Not aligned. The configurations, actions, and effects not particularly 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.

Regarding ASC, if the timing of switching one of the IGBTs 32a and 32b to the on state is different between the upper and lower arm circuits 31 and the remaining upper and lower arm circuits 31, the d-axis current Id tends to increase to the negative side. Findings were obtained. This finding is a finding obtained by a test, a simulation, or the like, and this finding will be described with reference to FIG.

When executing the ASC, the control device 40 first switches one of the IGBTs 32a and 32b to the on state for the upper and lower arm circuits 31 of one of the plurality of upper and lower arm circuits 31, and then the remaining upper and lower arm circuits 31. Switch to the on state. In the present embodiment, the difference between the timing at which one upper / lower arm circuit 31 is switched to the on state and the timing at which the remaining upper / lower arm circuits 31 are switched to the on state is referred to as a shift time TS.

In FIG. 9, the vertical axis is the maximum value Idmax of the d-axis current Id and the phase currents Iu, Iv, Iw as in FIG. 5, and the horizontal axis is the deviation time TS. As shown in FIG. 9, the longer the deviation time TS, the larger the maximum value Idmax of the d-axis current Id. On the other hand, each phase current Iu, Iv, Iw has a substantially constant value regardless of the deviation time TS. This is because the longer the deviation time TS, the more the d-axis current Id increases rapidly with the execution of ASC, and irreversible demagnetization of the permanent magnet 12b is likely to occur, while the increase of each phase current Iu, Iv, Iw occurs. It shows that it is difficult. Regarding the deviation time TS, it has been found that when the deviation time TS is generated during the execution of ASC, an unbalanced current is generated in the inverter 30 and the motor 12, and the d-axis current Id increases to the negative side due to this unbalanced current. Obtained by tests and the like.

The control device 40 sets the deviation time TS in the inverter control process, and executes ASC according to the deviation time. Here, the inverter control process of this embodiment will be described with reference to the flowchart of FIG.

In FIG. 10, in steps S101 to S107, the same processing as in the first embodiment is performed. If the motor temperature Tm is larger than the temperature threshold value Tb in step S107, the process proceeds to step S301. In step S301, the target deviation time TSasc is calculated for the deviation time TS as the target value when the ASC is executed. Here, first, the target value BEMFasc is acquired for the back electromotive force BEMF in the same manner as in step S201 of the first embodiment. Next, similarly to step S202 of the first embodiment, the target maximum value Idmax1 of the d-axis current Id is calculated from the target value BEMFasc of the counter electromotive force BEMF and the motor temperature Tm using the temperature correlation information. Further, using the rotation correlation information, the target maximum value Idmax2 of the d-axis current Id is calculated from the target value BEMFasc of the counter electromotive force BEMF and the motor rotation speed Nm. Then, the target maximum value Idmax0 is calculated using the target maximum values Idmax1 and Idmax2. For example, the average value of the target maximum values Idmax1 and Idmax2 is calculated, and this average value is set to the target maximum value Idmax0.

Then, the target deviation time TSasc is calculated from the target maximum value Idmax0 of the d-axis current Id using the deviation correlation information. The deviation correlation information is correlation information showing the correlation between the maximum value Idmax of the d-axis current Id and the deviation time TS, and is stored in the storage unit of the control device 40 as, for example, a map or a function. For example, when the information shown in FIG. 9 is used as the deviation correlation information, the value intersecting the target maximum value Idmax0 on the graph showing the maximum value Idmax of the d-axis current Id is calculated as the target deviation time TSasc for the deviation time TS.

After step S301, the process proceeds to step S108, and ASC is executed in the same manner as in the first embodiment. Here, first, one of the IGBTs 32a and 32b is switched to the ON state for one of the upper and lower arm circuits 31 among the plurality of upper and lower arm circuits 31. Then, the time elapsed after switching is measured as the shift time TS, and it is determined whether or not this shift time TS has reached the target shift time TSasc. Then, when the deviation time TS reaches the target deviation time TSasc, one of the IGBTs 32a and 32b is switched to the ON state for the remaining upper and lower arm circuits 31. Of the IGBTs 32a and 32b, the one that has not been switched to the on state switches to the off state at the same timing for all three-phase upper and lower arm circuits 31. Of the IGBTs 32a and 32b, the one that switches to the off state has the switching timing aligned with the one that switches to the on state when the shift time TS reaches the target shift time TSasc.

After step S108, the processes of steps S108 and S109 are executed in the same manner as in the first embodiment, and the inverter control process is terminated.

According to the present embodiment, when the control device 40 executes the ASC, the timing of switching to the ON state for one of the ASC 32a and 32b is set to the upper and lower arm circuit 31 of one of the plurality of upper and lower arm circuits 31 and the like. It is different from the upper and lower arm circuit 31 of. Therefore, if the timing of switching one of the ASCs 32a and 32b to the on state differs between one of the plurality of upper and lower arm circuits 31 and the rest, the d-axis current Id tends to increase to the negative side. It is possible to cause irreversible demagnetization of the permanent magnet 12b. As a result, the back electromotive force BEMF of the motor 12 can be reduced.

<Other embodiments>
The disclosure of this specification is not limited to the exemplified embodiments. Disclosures include exemplary embodiments and modifications by those skilled in the art based on them. For example, the disclosure is not limited to the combination of parts and elements shown in the embodiment, and can be variously modified and carried out. Disclosure can be carried out in various combinations. The disclosure can have additional parts that can be added to the embodiment. The disclosure includes the parts and elements of the embodiment omitted. Disclosures include replacements or combinations of parts, elements between one embodiment and another. The technical scope disclosed is not limited to the description of the embodiments. The technical scope disclosed is indicated by the description of the scope of claims and should be understood to include all modifications within the meaning and scope equivalent to the description of the scope of claims.

In each of the above embodiments, the permanent magnet 12b of the motor 12 may be formed of a magnet different from the neodymium magnet. For example, the permanent magnet 12b may be formed by a rare earth magnet such as a samarium cobalt magnet. Since the permanent magnet 12b formed by the rare earth magnet tends to have a stronger magnetic force as the temperature is lower, the lower the motor temperature Tm is, the lower the back electromotive force BEMF is for the ASC, as in the first embodiment. The finding that the target time TDasc should be lengthened is used.

Further, as for the temperature correlation information for setting the target time TDasc of the delay time TD and the target deviation time TSasc, it is preferable that different information is used depending on the characteristics of the magnet forming the permanent magnet 12b. For example, in a configuration in which the permanent magnet 12b is formed of a ferrite magnet, a finding different from the finding that the target time TDasc should be lengthened as the motor temperature Tm is lowered is used in order to reduce the back electromotive force BEMF.

In the first embodiment, the target time TDasc of the delay time TD for the ASC may be set according to only one of the motor rotation speed Nm and the motor temperature Tm. Further, the target time TDasc may be set according to the target value BEMFasc of the back electromotive force BEMF regardless of both the motor rotation speed Nm and the motor temperature Tm. Further, the target time TDasc may be set to a predetermined predetermined value. This specified value is, for example, a value stored in the storage unit of the control device 40.

In the second embodiment, regarding the execution of the ASC, two or more IGBTs may be switched to the ON state first among the IGBTs 32a and 32b. For example, one of the IGBTs 32a and 32b is first switched to the on state for two upper and lower arm circuits 31 among the plurality of upper and lower arm circuits 31, and then switched to the on state for the remaining one upper and lower arm circuit 31.

In the second embodiment, the timing of switching one of the IGBTs 32a and 32b to the ON state may be different for the plurality of upper and lower arm circuits 31 for the execution of the ASC. For example, one of the IGBTs 32a and 32b is first switched to the on state for one upper and lower arm circuit 31, and after the target deviation time TSasc has elapsed, the second upper and lower arm circuit 31 is switched to the on state. Then, after the target deviation time TSasc has elapsed, the third upper / lower arm circuit 31 is switched to the on state.

In the second embodiment, regarding the execution of ASC, the timing of switching the other of the IGBTs 32a and 32b to the off state may not be the same in the plurality of upper and lower arm circuits 31. That is, at least one of the plurality of upper and lower arm circuits 31 may be different from the rest.

In the second embodiment, the target deviation time TSasc for the ASC may be set according to only one of the motor rotation speed Nm and the motor temperature Tm. Further, the target deviation time TSasc may be set according to the target value BEMFasc of the back electromotive force BEMF regardless of both the motor rotation speed Nm and the motor temperature Tm. Further, the target deviation time TSasc may be set to a predetermined predetermined value. This specified value is, for example, a value stored in the storage unit of the control device 40.

In the second embodiment, the target deviation time TSasc for the ASC may be set to compensate for the shortage when the reduction of the back electromotive force BEMF due to the delay of the ASC is insufficient. Further, the target time TDasc of the delay time TD for the ASC may be set so as to make up for the shortage when the reduction of the counter electromotive force BEMF due to the temporal shift of the on-drive is insufficient.

In the second embodiment, when the target deviation time TSasc is set for the execution of the ASC, it is not necessary to delay the switching to the on state for the IGBT that first switches to the on state among the IGBTs 32a and 32b. For example, in step S106, the target time TDasc of the delay time TD is set to zero. Further, in the inverter control process of FIG. 7, the processes of steps S106 and S107 may not be performed. In either case, the timing for turning on one of the IGBTs 32a and 32b differs between the upper and lower arm circuits 31 and the remaining upper and lower arm circuits 31, so that the d-axis current Id tends to increase rapidly to the negative side. You can make it.

In each of the above embodiments, if one of the IGBTs 32a and 32b is driven on by all of the plurality of upper and lower arm circuits 31 for the execution of the ASC, the other may not be driven off. In this way, if one of the IGBTs 32a and 32b is switched to the ON state in all of the plurality of upper and lower arm circuits 31, the d-axis current Id becomes larger on the negative side, and irreversible demagnetization of the permanent magnet 12b is likely to occur.

In each of the above embodiments, a temperature sensor for detecting the motor temperature Tm may be provided around the motor 12 or on the motor itself. For example, the temperature sensor is attached to the permanent magnet 12b of the motor 12. In this configuration, the temperature of the permanent magnet 12b can be directly detected as the motor temperature Tm by the detection signal of the temperature sensor. Further, the control device 40 may estimate and acquire the motor temperature Tm using each phase current Iu, Iv, Iw as a detected value, each phase voltage Vu, Vv, Vw, or the like. Further, the control device 40 may estimate and acquire the motor temperature Tm using the d-axis current Id, the q-axis current Iq, the d-axis voltage Vd, the q-axis voltage Vq, and the like.

In each of the above embodiments, the current sensor 28 does not have to detect the current flowing through the winding 12a for all three phases. For example, the current sensor 28 outputs a detection signal for two of the three phases, the current calculation unit of the control device 40 calculates each phase current for the two phases corresponding to the detection signal, and the remaining one phase for each phase current. May be estimated from the currents of each of the two phases.

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

(I) The hardware processor may be a hardware logic circuit. In this case, the computer is provided by a digital circuit containing a large number of programmed logic units (gate circuits). Digital circuits may include memory that stores at least one of a program and data. Computers may be provided by analog circuits. Computers may be provided by a combination of digital and analog circuits.

(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 by at least one memory and at least one processor core. The processor core is referred to as, for example, a CPU. Memory is also referred to as a storage medium. A memory is a non-transitional and substantive storage medium that non-temporarily stores "at least one of a program and data" that can be read by a processor.

(Iii) The hardware processor may be a combination of the above (i) and the above (ii). (I) and (ii) are arranged on different chips or on a common chip.

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

In each of the above embodiments, the switching element constituting the inverter 30 is not limited to the IGBT. That is, for example, a MOSFET or the like may be used as the upper arm switch or the lower arm switch.

In each of the above embodiments, the motor 12 may include a permanent magnet 12b forming a field magnet to form a stator, or may include a winding 12a forming an armature to form a rotor. good. Further, the motor 12 does not have to be a three-phase AC motor as long as it is a multi-phase AC motor. For example, as the motor 12, a two-phase AC motor or a four-phase or more AC motor may be used.

In each of the above embodiments, the vehicle on which the power conversion device 13 is mounted includes a passenger car, a bus, a construction work vehicle, an agricultural machine vehicle, and the like. Further, the vehicle is one of the moving bodies, and the moving body on which the power conversion device 13 is mounted includes a train, an airplane, and the like in addition to the vehicle. The power conversion device 13 includes an inverter device, a converter device, and the like. Examples of this converter device include a power supply device for AC input / DC output, a power supply device for DC input / DC output, and a power supply device for AC input / AC output.

11 ... Battery as power supply unit, 12 ... Motor, 13 ... Power conversion device, 30 ... Inverter as power conversion unit, 31 ... Upper and lower arm circuit as arm circuit, 32a ... IGBT as upper arm switch, 32b ... Lower arm IGBT as a switch, BEMF ... back electromotive force, BEMFb ... reverse threshold, TD ... delay time, TDasc ... target time, Nm ... motor rotation speed as rotation speed, Tb ... temperature threshold, Tm ... motor temperature as temperature, S107 ... Delay unit, S108 ... State transition unit, S109 ... End unit, S110 ... Restriction unit, S202 ... Target setting unit and temperature setting unit, S203 ... Target setting unit and rotation setting unit, S204 ... Target setting unit.

Claims (10)

A power conversion device (13) that converts the power supplied from the power supply unit (11) to the motor (12) from direct current to alternating current by the power conversion unit (30).
When an abnormality occurs in the power conversion unit, the power conversion unit is connected to the upper arm switch (32a) on the high potential side and the lower side on the low potential side for all of the plurality of arm circuits (31) connected in parallel to each other. A state transition unit (S108) that shifts to a target state in which one of the arm switches (32b) is turned on and the other is turned off.
A delay unit (S107) that delays the transition of the power conversion unit to the target state by the state transition unit by at least the target time (TDasc) from the occurrence of an abnormality in the power conversion unit.
A power converter equipped with. The state transition part is
The power conversion device according to claim 1, wherein the timing for switching to the on state of one of the upper arm switch and the lower arm switch is aligned by the plurality of arm circuits. The state transition part is
According to claim 1 or 2, the timing for switching one of the upper arm switch and the lower arm switch to the on state is different between at least one arm circuit of the plurality of arm circuits and the other arm circuit. The power converter described. When the temperature (Tm) of the motor is equal to or less than a predetermined temperature threshold (Tb), the counter electromotive force (BEMF) of the motor is equal to or less than the predetermined inverse threshold (BEMFb). The power conversion device according to any one of claims 1 to 3, further comprising a limiting unit (S110) for limiting the number of rotations (Nm). The power conversion device according to claim 4, wherein the limiting unit limits the rotation speed (Nm) of the motor according to the temperature (Tm) of the motor. The power conversion device according to claim 4 or 5, wherein the inverse threshold value is an upper limit value of a voltage applied to the power conversion unit. After the power conversion device shifts to the target state by the state transition unit, the termination unit shifts to the end state in which all of the plurality of arm circuits of both the upper arm switch and the lower arm switch are turned off (the end unit). S109) The power conversion device according to any one of claims 1 to 6, further comprising S109). 7. The power conversion device according to one. The target setting unit is
It has a rotation setting unit (S203) that uses rotation correlation information indicating the correlation between the rotation speed (Nm) of the motor and the delay time (TD) delayed from the occurrence of an abnormality in the power conversion unit to set the target time. The power conversion device according to claim 8. The target setting unit is
It has a temperature setting unit (S202) that uses temperature correlation information indicating the correlation between the temperature (Tm) of the motor and the delay time (TD) delayed from the occurrence of an abnormality in the power conversion unit to set the target time. The power conversion device according to claim 8 or 9.

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