JP7631745B2 - Inverter control device, program - Google Patents

Description

The present invention relates to an inverter control device and a program .

As described in Patent Document 1, a system equipped with a rotating electric machine and an inverter is known. The rotating electric machine has a rotor with a permanent magnet and a stator with coils of multiple phases, and serves as a power source for running a vehicle. The inverter has upper and lower arm switches for each phase, and electrically connects the power storage unit and the coils. The upper and lower arm switches are switches with external diodes connected in inverse parallel, or switches with built-in parasitic diodes. An inverter control device applied to this system controls the switching of the upper and lower arm switches.

JP 2017-112680 A

When the drive wheels of the vehicle rotate as the vehicle moves, the rotor rotates and a back electromotive force is generated in the coil by the magnetic flux of the permanent magnet. As the rotor rotates faster, the back electromotive force increases. As a result, even if the upper and lower arm switches are all turned off, current flows from the coil through the diode to the storage unit, and the voltage of the storage unit may become excessively high. In this case, problems such as the failure of the storage unit may occur. Also, for example, charging of the storage unit can be avoided by switching the system main relay (SMR) to OFF. However, in this case, the back electromotive force is applied as is to the inverter and other devices connected in parallel with the inverter. In this case, if the back electromotive force exceeds the withstand voltage of those components, those components may fail.

This problem can occur, for example, when the vehicle is towed by another vehicle. When the towed vehicle's traveling speed increases, the rotor's rotation speed also increases, and the back electromotive force increases. As a result, the voltage of the storage unit can become excessively high.

Patent Document 1 describes a method in which a permanent magnet is heated by alternately switching the d-axis current between positive and negative, and then the d-axis current is made to flow in the negative direction, thereby irreversibly demagnetizing the permanent magnet. This reduces the back electromotive force. However, this method requires complex control of the d-axis current.

The above-mentioned problems can occur not only in vehicles, but also in any moving object equipped with a rotating electric machine as a power source for movement.

The present invention has been made in consideration of the above circumstances, and has as its main object to provide an inverter control device and a program capable of demagnetizing a permanent magnet in a simple manner.

The present invention includes a power storage unit and
a rotating electric machine including a rotor having a permanent magnet and a stator having coils for multiple phases, the rotating electric machine serving as a power source for moving a moving body;
an inverter having upper and lower arm switches with diodes connected in anti-parallel, electrically connecting the power storage unit and the coil;
An inverter control device applied to a system including:
a necessity determination unit that determines whether demagnetization of the permanent magnet is necessary;
When the necessity determination unit determines that demagnetization is necessary, one of the upper and lower arm switches is turned ON for all phases and the other arm switch is turned OFF for all phases, thereby executing short-circuit control to flow a return current through a closed circuit including the arm switch that is turned ON and the coil, and after executing the short-circuit control, performs cut-off control to prevent the return current from flowing.

In the present invention, when the necessity determination unit determines that demagnetization of the permanent magnet is necessary, the cutoff control unit executes short-circuit control. This causes a return current to flow through the closed circuit that includes the arm switch and coil that are turned on.

When short circuit control is executed, the operating point specified by the d- and q-axis current values in the dq coordinate system eventually converges to a final destination position where the q-axis current value is zero and the d-axis current value is a predetermined negative value. In this case, the operating point does not move linearly from the operating point at the start of short circuit control to the final destination position, but moves toward the final destination position by tracing a spiral trajectory centered on the final destination position. In the process of moving toward the final destination position, the d-axis current intermittently increases in the negative direction. By utilizing this d-axis current, the permanent magnet can be demagnetized.

However, if short circuit control continues to be executed, the return current continues to flow. In this case, the d-axis current continues to flow, and there is a risk that the permanent magnet will be demagnetized excessively. In addition, current will continue to flow to the arm switch that is turned on by the short circuit control, and there is a risk that the arm switch through which current continues to flow will break down.

Therefore, in the present invention, after short-circuit control is performed to pass a return current for demagnetization, cut-off control is performed to stop the return current from flowing. This makes it possible to prevent the permanent magnet from being demagnetized too much or to prevent the arm switch from breaking down when it is turned on.

According to the present invention described above, it is possible to demagnetize permanent magnets while suppressing the occurrence of failures in inverters, etc., through simple controls such as short circuit control and cutoff control.

1 is an overall configuration diagram of an in-vehicle control system according to a first embodiment. FIG. 2 is a diagram showing an inverter, a rotating electric machine, and their peripheral configuration. FIG. 2 is a functional block diagram of an inverter control device. FIG. 13 is a diagram showing changes in d- and q-axis current values when three-phase short-circuit control is continued. FIG. 2 is a diagram showing a necessity determination unit, a demagnetization execution unit, and their peripheral configurations. 4 is a flowchart showing a procedure of demagnetization control. FIG. 13 is a diagram showing changes in d- and q-axis current values when demagnetization control is executed. 5 is a time chart showing transition of duration of three-phase short circuit control and shutdown control. FIG. 11 is a diagram showing the relationship between magnet temperature and the duration of three-phase short circuit control according to the second embodiment. 13 is a flowchart showing a procedure of demagnetization control according to a third embodiment. 13 is a flowchart showing a procedure of demagnetization control according to a fourth embodiment. 13 is a flowchart showing a procedure of demagnetization control according to a fifth embodiment. 13 is a flowchart showing a procedure of demagnetization control according to a sixth embodiment. FIG. 13 is a diagram showing an inverter, a rotating electric machine, and their peripheral configuration according to another embodiment.

First Embodiment
A first embodiment of a control device according to the present invention will now be described with reference to the drawings. The control device according to the present embodiment configures a control system together with a rotating electric machine as a driving power source, and the control system is mounted on a vehicle.

As shown in FIG. 1, the vehicle 10 has left and right front wheels 11a, left and right rear wheels 11b, and a high-voltage battery 20. The high-voltage battery 20 is, for example, a lithium-ion battery or a nickel-metal hydride battery. In the following description, the front wheels 11a and rear wheels 11b may be simply referred to as drive wheels 11.

The control system mounted on the vehicle 10 includes a rotating electric machine 30, an inverter 40 that electrically connects the high-voltage battery 20 and the rotating electric machine 30, an inverter control device 50 that controls the inverter 40, and a host control device 80 (see FIG. 2). In this embodiment, the rotating electric machine 30 is an on-board motor. The control system also includes two sets of rotating electric machines 30 and inverters 40. Of the two sets of rotating electric machines 30 and inverters 40, one set constitutes a power system for applying driving force to the front wheels 11a, and the other set constitutes a power system for applying driving force to the rear wheels 11b. In this embodiment, the rotating electric machine 30 is a synchronous machine, more specifically, a permanent magnet synchronous machine. In this embodiment, the configurations of the two sets of rotating electric machines 30 and inverters 40 are basically the same. For this reason, one of the two sets will be mainly described below.

Figure 2 shows the electrical configuration of the rotating electric machine 30 and the inverter 40.

The rotating electric machine 30 includes a stator 32 and a rotor 33. The rotating shaft of the rotor 33 is connected to the drive wheels 11 via a transmission and a shaft 12 (not shown). The stator 32 is provided with a three-phase coil 31. The rotor 33 is provided with a permanent magnet 34.

The inverter 40 has three phases of series connections of upper arm switches SWp and lower arm switches SWn. In this embodiment, each switch SWp, SWn is a voltage-controlled semiconductor switching element, more specifically an IGBT. Upper and lower arm diodes Dp, Dn, which are freewheel diodes, are connected in inverse parallel to the upper and lower arm switches SWp, SWp.

In each phase, the first end of the coil 31 is connected to the emitter, which is the low potential terminal of the upper arm switch SWp, and the collector, which is the high potential terminal of the lower arm switch SWn, via a conductive member Lm such as a bus bar. The second end of the coil 31 of each phase is connected at the neutral point. In other words, the coils 31 of each phase are star-connected. The coils 31 of each phase are arranged with a 120° electrical angle offset from each other.

The collector of the upper arm switch SWp of each phase is connected to a first terminal of a first cutoff switch SWRp via a high potential side path Lp. The emitter of the lower arm switch SWn of each phase is connected to a first terminal of a second cutoff switch SWRn via a low potential side path Ln. The second terminal of the first cutoff switch SWRp is connected to the positive terminal of the high voltage battery 20, and the second terminal of the second cutoff switch SWRn is connected to the negative terminal of the high voltage battery 20. In this embodiment, each cutoff switch SWRp, SWRn is a relay (specifically, for example, a system main relay). Each cutoff switch SWRp, SWRn is operated by the inverter control device 50 or the upper control device 80.

The control system includes a smoothing capacitor 41 and an on-board electrical device 42. The smoothing capacitor 41 connects the high-potential side path Lp and the low-potential side path Ln. The electrical device 42 is connected to the high-potential side path Lp and the low-potential side path Ln. The electrical device 42 includes, for example, at least one of an electric compressor and a DC-DC converter. The electric compressor constitutes an interior air conditioner and is driven by power supplied from the high-voltage battery 20 to circulate the refrigerant of the on-board refrigeration cycle. The DC-DC converter steps down the output voltage of the high-voltage battery 20 and supplies it to the on-board low-voltage load. The low-voltage load includes a low-voltage battery (not shown). The low-voltage battery is a secondary battery whose output voltage (for example, rated voltage) is lower than the output voltage (rated voltage) of the high-voltage battery 20, for example, a lead-acid battery.

When each of the cutoff switches SMRp, SMRn is ON, the high-voltage battery 20 and the smoothing capacitor 41 become the power storage unit for the inverter 40 and the electrical equipment 42. On the other hand, when each of the cutoff switches SMRp, SMRn is OFF, the high-voltage battery 20 and the smoothing capacitor 41, of which the smoothing capacitor 41 becomes the power storage unit for the inverter 40 and the electrical equipment 42.

The control system includes a phase current detection unit 43, an angle detection unit 44, and a voltage detection unit 45. The phase current detection unit 43 detects at least two phases of the currents flowing through the rotating electric machine 30. The angle detection unit 44 detects the electrical angle of the rotor 33 and is, for example, a resolver. The voltage detection unit 45 detects the voltage between the terminals of the smoothing capacitor 41.

The control system includes a first temperature detection unit 46 and a second temperature detection unit 47. The first temperature detection unit 46 detects the temperature of the diodes Dp, Dn and the switches SWp, SWn that constitute the inverter 40. The second temperature detection unit 47 detects the temperature of the permanent magnet 34.

The control system includes a DC current detection unit 48. The DC current detection unit 48 detects the current flowing through the high potential side path Lp. The detection values of each of the detection units 43 to 48 are input to the inverter control device 50.

The inverter control device 50 is an ECU (electronic control unit) having a CPU, RAM, ROM, etc. The inverter control device 50 performs power running control. Power running control is switching control of the upper and lower arm switches SWp, SWn to convert the DC power output from the high-voltage battery 20 into AC power and supply it to the coil 31. When this control is performed, the rotating electric machine 30 functions as an electric motor and generates power running torque (>0). The inverter control device 50 also performs regenerative drive control. Regenerative drive control is switching control of the upper and lower arm switches SWp, SWn to convert the AC power generated by the rotating electric machine 30 into DC power and supply it to the high-voltage battery 20. When this control is performed, the rotating electric machine 30 functions as a generator and generates regenerative torque (<0).

Figure 3 is a block diagram of the process executed by the inverter control device 50. In the inverter control device 50, the torque command unit 51 calculates the torque command value Trq* by receiving a command from the upper control device 80. The current command unit 52 calculates the d-axis current command value Id* and the q-axis current command value Iq* based on the calculated torque command value Trq*.

The dq conversion unit 53 calculates the d-axis current value Idr and the q-axis current value Iqr in the dq coordinate system based on the phase current detected by the phase current detection unit 43 and the electrical angle θe detected by the angle detection unit 44.

The deviation calculation unit 54 calculates the d-axis current deviation ΔId, which is the difference between the d-axis current command value Id* and the d-axis current value Idr, and the q-axis current deviation ΔIq, which is the difference between the q-axis current command value Iq* and the q-axis current value Iqr.

The feedback control unit 55 calculates a d-axis voltage command value Vd* as an operation amount for feedback-controlling the d-axis current deviation ΔId to 0, and calculates a q-axis voltage command value Vq* as an operation amount for feedback-controlling the q-axis current deviation ΔIq to 0. The feedback control is, for example, proportional-integral control.

The modulator 56 calculates the U-, V-, and W-phase voltage command values Vu*, Vv*, and Vw* based on the d- and q-axis voltage command values Vd* and Vq*, the electrical angle θe, and the power supply voltage Vb, which is the terminal voltage of the smoothing capacitor 41 detected by the voltage detection unit 45. In more detail, taking the U-phase as an example, the modulator 56 generates a U-phase drive signal to be supplied to the gates of the upper and lower arm switches SWp and SWn of the U-phase based on a comparison of the magnitude between a signal obtained by normalizing the U-phase voltage command value Vu* with the power supply voltage Vb and a carrier signal such as a triangular wave signal. Similarly, the modulator 56 generates a V-phase drive signal to be supplied to the gates of the upper and lower arm switches SWp and SWn of the V-phase, and a W-phase drive signal to be supplied to the gates of the upper and lower arm switches SWp and SWn of the W-phase. Each drive signal is an OFF command to instruct the switch to be OFF or an ON command to instruct the switch to be ON. The drive signals are supplied to the gates of the upper and lower arm switches SWp and SWn, controlling the switching of the upper and lower arm switches SWp and SWn for each phase.

The inverter control device 50 is provided with a necessity determination unit 57 and a demagnetization execution unit 58. The reasons for providing the necessity determination unit 57 and the demagnetization execution unit 58 are explained below.

There are cases where the vehicle 10 is unable to move on its own due to, for example, a malfunction. In this case, the vehicle 10 may be towed by another vehicle (e.g., a tow truck) with both the front wheels 11a and the rear wheels 11b in contact with the road surface, or with one of the front wheels 11a and the rear wheels 11b lifted and the other in contact with the road surface. In this case, the drive wheels 11 of the vehicle 10 rotate as the other vehicle moves. As the wheels rotate, the rotor 33 rotates, and a back electromotive force is generated in the three-phase coil 31 by the magnetic flux of the permanent magnet 34.

When the vehicle 10 is towed, the shutoff switches SWRp, SMRn are normally turned OFF, and the inverter 40 executes shutdown control in which the upper and lower arm switches SWp, SWn of all phases are turned OFF. In this case, if the back electromotive force exceeds the terminal voltage of the smoothing capacitor 41, current flows from each coil 31 to the smoothing capacitor 41 via the inverter 40, and the terminal voltage of the smoothing capacitor 41 increases. As a result, if the back electromotive force exceeds the withstand voltage of at least one of the diodes Dp, Dn, the upper and lower arm switches SWp, SWn, the smoothing capacitor 41, and the electrical equipment 42, that equipment may break down.

In particular, when the traveling speed of other vehicles is high or when the permanent magnets 34 have a high magnetic flux density in order to increase the torque of the rotating electric machine 30, the back electromotive voltage is likely to be high, and the above-mentioned failures are likely to occur. Specific examples of rotating electric machines with increased torque include those with a slotless structure that has an intrinsic coercive force of 400 kA/m or more and a permanent magnet with a residual magnetic flux density of 1.0 T or more, as described in JP 2019-106866 A.

Even when the vehicle 10 is not being towed, if one of the two rotating electric machines 30 cannot be powered, the same problem can occur when the vehicle 10 continues to travel by powering the other machine.

To address such problems, the demagnetization execution unit 58 performs demagnetization control to irreversibly demagnetize the permanent magnet 34 as necessary to reduce the back electromotive voltage. Hereinafter, irreversible demagnetization may be referred to simply as demagnetization. Demagnetization control includes three-phase short circuit control and shutdown control, which corresponds to cutoff control. The three-phase short circuit control of this embodiment is control that turns on the lower arm switches SWn of all phases and turns off the upper arm switches SWp of all phases. The three-phase short circuit control is also called ASC (Active Short Circuit) control.

In demagnetization control, shutdown control is executed after three-phase short circuit control is executed. The reason for this is explained below.

Figure 4 is a diagram of the dq coordinate system showing the transition of the d-axis and q-axis current values Id and Iq when three-phase short circuit control is continued. Hereinafter, the position specified by the d-axis and q-axis current values Id and Iq in the dq coordinate system of current values will be referred to as the operating point OP. In addition, in this embodiment, the sign of the d-axis current Id is positive when performing field strengthening, and the sign of the d-axis current Id is negative when performing field weakening. In addition, the sign of the q-axis current Iq is positive when powering torque is generated in the first rotation direction of the rotor 33 by powering drive control, and the sign of the q-axis current Iq is negative when regenerative torque is generated in the second rotation direction opposite to the first rotation direction by regenerative drive control.

When three-phase short circuit control is executed, a return current flows through the inverter 40 and the coil 31. In this case, as shown in FIG. 4, the operating point OP eventually converges to a final arrival position M where the q-axis current value Iq is 0 and the d-axis current value Id is a negative predetermined value. This predetermined value is, for example, a value when the magnetic flux of the permanent magnet 34 is equal to the magnetic flux generated in the coil 31 by the d-axis current value Id and in a direction that cancels out the magnetic flux.

The operating point OP does not move in a straight line from the starting position Ps where the three-phase short circuit control is started to the final destination position M, but moves in a clockwise spiral trajectory from the final destination position M toward the final destination position M. In the example shown in FIG. 4, the trajectory of the operating point OP from the starting position Ps toward the final destination position M exists in the second and third quadrants and in the d-axis region sandwiched between the second and third quadrants in the dq coordinate system of the current value. The second quadrant is the region where the q-axis current value Iq is positive and the d-axis current value Id is negative, and the third quadrant is the region where both the d-axis and q-axis current values Id and Iq are negative.

As the operating point OP moves toward the final destination position M, the d-axis current intermittently increases in the negative direction. This d-axis current can be used to demagnetize the permanent magnet 34. However, if the three-phase short circuit control continues to be executed, the return current continues to flow. In this case, the d-axis current continues to flow, which may cause the permanent magnet 34 to be demagnetized too much, or current may flow through the lower arm switch SWn that is turned on by the three-phase short circuit control, causing the lower arm switch SWn to break down.

Therefore, in this embodiment, after the three-phase short circuit control is performed, the shutdown control is performed. This prevents the return current from flowing.

Figure 5 is a block diagram showing the necessity determination unit 57, the demagnetization execution unit 58, and their peripheral configuration.

The host control device 80 determines whether or not an abnormality has occurred in the vehicle 10. For example, when the host control device 80 determines that any of the following conditions (A1) to (A3) is satisfied, it determines that an abnormality has occurred in the vehicle 10.

(A1) A condition that the vehicle 10 has collided and the airbag has been activated (A2) A condition that the vehicle 10 is towed by another vehicle (A3) A condition that an abnormality has occurred in the control system Abnormalities in the control system include at least one abnormality in each rotating electric machine 30 and each inverter 40, and at least one abnormality in each detection unit 43 to 48. Abnormalities in the inverter 40 include a short circuit failure or an open circuit failure in the upper and lower arm switches SWp, SWn.

When the upper level control device 80 determines that an abnormality has occurred in the vehicle 10, the inverter control device 50 is configured so that the drive signal for each phase output from the modulator 56 becomes an OFF command. This configuration can be realized, for example, by the upper level control device 80 instructing the torque command unit 51 to stop calculating the torque command value Trq*.

In addition, if the upper control device 80 determines that an abnormality has occurred in the vehicle 10, it sends an abnormality notification signal to the necessity determination unit 57.

When the necessity determination unit 57 receives an abnormality notification signal from the upper control device 80, it determines whether there is an abnormality in the configuration of the inverter 40 and the inverter control device 50 that is necessary for executing three-phase short-circuit control and shutdown control. In this embodiment, this abnormality includes the following abnormalities (B1) to (B4).

(B1) An abnormality that makes it impossible to switch the switching state of the lower arm switch SWn. (B2) A short circuit failure of the upper arm switch SWp. (B3) An abnormality in the function of generating drive signals for each phase for executing the three-phase short circuit control and the shutdown control in the inverter control device 50, and in the function of transmitting the generated drive signals to the gates of each switch SWp, SWn. (B4) An abnormality in at least one of the detection units (specifically, the DC current detection unit 48, the voltage detection unit 45, and the first temperature detection unit 46) that detect values used in step S12 described later. When it is determined that there is no abnormality in the configuration required for executing the three-phase short circuit control and the shutdown control, the necessity determination unit 57 determines whether or not demagnetization of the permanent magnet 34 is necessary. In this embodiment, the necessity determination unit 57 determines that demagnetization is necessary when any of the first to third conditions is satisfied, and determines that demagnetization is unnecessary when none of the first to third conditions is satisfied.

The first condition is that the DC current value Ip detected by the DC current detection unit 48 is smaller than the current threshold value Ith. In this embodiment, the sign of the DC current value Ip when it flows through the high potential side path Lp from the high voltage battery 20 side to the inverter 40 side is set to be positive. In addition, the current threshold value Ith is set to 0 or a value slightly smaller than 0.

The first condition is a condition for determining whether the smoothing capacitor 41 is in a charging state. When the necessity determination unit 57 determines that the DC current value Ip is equal to or greater than the current threshold value Ith, it determines that the smoothing capacitor 41 is not in a charging state and that demagnetization is not required. On the other hand, when the necessity determination unit 57 determines that the DC current value Ip is smaller than the current threshold value Ith, it determines that the smoothing capacitor 41 is not in a charging state and that demagnetization is required. When the DC current value Ip is less than 0, the smoothing capacitor 41 is charged by the charging current caused by the back electromotive force, and the terminal-to-terminal voltage of the smoothing capacitor 41 rises. As a result, problems such as failure of the smoothing capacitor 41 and the electrical equipment 42 may occur. In order to address this problem, the first condition is set.

The second condition is that the power supply voltage Vb is higher than the voltage threshold Vth. For example, when each of the cutoff switches SMRp and SMRn is ON, the voltage threshold Vth is set to a value equal to or slightly lower than the lowest withstand voltage among the withstand voltages of the high-voltage battery 20, the smoothing capacitor 41, and the electrical equipment 42. For example, when each of the cutoff switches SMRp and SMRn is OFF, the voltage threshold Vth is set to a value equal to or slightly lower than the lowest withstand voltage among the withstand voltages of the smoothing capacitor 41 and the electrical equipment 42.

When the necessity determination unit 57 determines that the power supply voltage Vb is equal to or lower than the voltage threshold Vth, it determines that demagnetization is unnecessary. On the other hand, when the necessity determination unit 57 determines that the power supply voltage Vb is higher than the voltage threshold Vth, it determines that demagnetization is necessary. By setting the second condition, it is possible to determine that demagnetization is necessary before the power supply voltage Vb exceeds the withstand voltage of at least one of the high-voltage battery 20, the smoothing capacitor 41, and the electrical device 42.

The third condition is that the element temperature Tdr, which is the temperature detected by the first temperature detection unit 46, is higher than the temperature threshold value Tdth. The element temperature Tdr is, for example, the highest temperature (for example, the temperature of the diodes Dp and Dn) among the temperatures of the components detected by the first temperature detection unit 46. The third condition is a condition for suppressing the occurrence of a situation in which the components of the inverter 40 overheat and break down. When the necessity determination unit 57 determines that the element temperature Tdr is equal to or lower than the temperature threshold value Tdth, it determines that demagnetization is unnecessary. On the other hand, when the necessity determination unit 57 determines that the element temperature Tdr is higher than the temperature threshold value Tdth, it determines that demagnetization is necessary. By demagnetizing, the back electromotive force can be suppressed and the current flowing through the elements that constitute the inverter 40 can be reduced.

If the necessity determination unit 57 determines that demagnetization is unnecessary, it sets the logic of the demagnetization command to be output to the demagnetization execution unit 58 to L, and if it determines that demagnetization is necessary, it sets the logic of the demagnetization command to H.

The demagnetization execution unit 58 includes a shutdown determination unit 58a, a NOT circuit 58b, and an AND circuit 58c. The demagnetization command of the necessity determination unit 57 is input to the shutdown determination unit 58a. The shutdown determination unit 58a includes a timer that counts the elapsed time Ltr after the logic of the demagnetization command is switched to H. The shutdown determination unit 58a determines that execution of the shutdown control is unnecessary until the counted elapsed time Ltr reaches the determination time Lth, and determines that execution of the shutdown control is necessary when it is determined that the counted elapsed time Ltr has reached the determination time Lth. When the shutdown determination unit 58a determines that execution of the shutdown control is unnecessary, it sets the logic of the shutdown command to be output to the NOT circuit 58b to L. In this case, the logic of the output signal from the NOT circuit 58b to the AND circuit 58c becomes H. On the other hand, when the shutdown determination unit 58a determines that execution of the shutdown control is necessary, it sets the logic of the shutdown command to be output to the NOT circuit 58b to H. In this case, the logic of the output signal from NOT circuit 58b to AND circuit 58c becomes L.

When the logic of the output signal of the NOT circuit 58b is L, the AND circuit 58c sets the logic of the instruction signal Sig output to the modulator 56 to L, regardless of the logic of the demagnetization command. In this case, the drive signals output from the modulator 56 to the upper and lower arm switches SWp and SWn of each phase that constitute the inverter 40 are all set to OFF commands. As a result, shutdown control is executed.

When the logic of the output signal of the NOT circuit 58b and the demagnetization command are both H, the AND circuit 58c sets the logic of the instruction signal Sig output to the modulator 56 to H. In this case, the drive signal output from the modulator 56 to the lower arm switch SWn of each phase is set to an ON command, and the drive signal output from the modulator 56 to the upper arm switch SWp of each phase is set to an OFF command. As a result, three-phase short circuit control is executed.

Figure 6 is a flowchart showing the demagnetization control procedure.

In step S10, the host control device 80 determines whether an abnormality has occurred in the vehicle 10.

If the upper control device 80 determines that an abnormality has occurred in the vehicle 10, in step S11, the necessity determination unit 57 determines whether or not there is an abnormality in the configuration required to execute the three-phase short circuit control and the shutdown control.

If the necessity determination unit 57 determines that there is no abnormality in this configuration, it proceeds to step S12 and determines whether demagnetization of the permanent magnet 34 is necessary. In more detail, the necessity determination unit 57 determines that demagnetization is necessary if any of the first to third conditions described above is satisfied, and determines that demagnetization is not necessary if none of the first to third conditions is satisfied.

If the necessity determination unit 57 determines that none of the first to third conditions are met, it determines that demagnetization is unnecessary and sets the logic of the demagnetization command to L. Then, it ends the demagnetization control. On the other hand, if the necessity determination unit 57 determines that any of the first to third conditions are met, it determines that demagnetization is necessary.

In step S13, the necessity determination unit 57 sets the logic of the demagnetization command to H. Thereafter, the shutdown determination unit 58a sets the logic of the shutdown command output to the NOT circuit 58b to L until the elapsed time Ltr from when the logic of the demagnetization command was switched to H reaches the determination time Lth. As a result, the logic of the output signal from the NOT circuit 58b to the AND circuit 58c becomes H, and the logic of the instruction signal Sig output from the AND circuit 58c becomes H. As a result, three-phase short-circuit control is executed in the inverter 40.

If the shutdown determination unit 58a determines in step S14 that the elapsed time Ltr has reached the determination time Lth, the process proceeds to step S15, where the logic of the shutdown command output to the NOT circuit 58b is set to H. As a result, the logic of the output signal from the NOT circuit 58b to the AND circuit 58c becomes L, and the logic of the instruction signal Sig output from the AND circuit 58c becomes L. As a result, shutdown control is executed in the inverter 40.

In the process shown in FIG. 6, for example, when the host control device 80 determines that the vehicle 10 is being towed by another vehicle, it determines which of the front wheels 11a and the rear wheels 11b is rotating, for example based on the detection value of the angle detection unit 44. Here, of the two rotating electric machines 30, the rotating electric machine that applies driving torque to the rotating driving wheel 11 is set as the target rotating electric machine. The inverter control device 50 performs the process of steps S11 to S15 on the inverter of the two inverters 40 that is connected to the target rotating electric machine.

For example, when the host control device 80 determines that at least one abnormality has occurred in each rotating electric machine 30 and each inverter 40, or at least one abnormality has occurred in each detection unit 43-48, it selects one of the two rotating electric machines 30 that can apply drive torque to the drive wheels 11. The inverter control device 50 performs the processes of steps S11-S15 for the inverter connected to the selected rotating electric machine out of the two inverters 40, and performs power drive control or regenerative drive control for the remaining inverter. This allows the vehicle 10 to continue traveling as long as possible.

Next, an example of how demagnetization control is executed will be described. Here, we will explain a case where an abnormality occurs in the vehicle 10 and the vehicle 10 is towed by another vehicle.

First, the host controller 80 determines that an abnormality has occurred in the vehicle 10. As a result, the host controller 80 stops issuing commands to the torque command unit 51, and shutdown control is performed in the inverter 40.

The upper control device 80 sends an abnormality notification signal to the necessity determination unit 57. This causes the necessity determination unit 57 to start determining whether demagnetization is necessary. Before the vehicle 10 is towed, the drive wheels 11 in contact with the road surface are not rotating, so no back electromotive force is generated in the coil 31. Therefore, the necessity determination unit 57 determines that the DC current value Ip is equal to or greater than the current threshold Ith, and sets the logic of the demagnetization command to L. In this case, the logic of the instruction signal Sig output from the AND circuit 58c becomes L. As a result, the execution of the shutdown control is maintained.

After that, the vehicle 10 is towed, and the drive wheels 11 in contact with the road surface rotate. As a result, a back electromotive force is generated in the coil 31, and when the back electromotive force exceeds the terminal voltage of the smoothing capacitor 41, current flows from the inverter 40 side to the smoothing capacitor 41 side, and the DC current value Ip becomes a negative value. When the DC current value Ip falls below the current threshold Ith, the necessity determination unit 57 switches the logic of the demagnetization command to H. The logic of the instruction signal Sig is maintained at L until the elapsed time Ltr after the logic of the demagnetization command is switched to H reaches the judgment time Lth. After that, when the elapsed time Ltr reaches the judgment time Lth, the logic of the instruction signal Sig is switched to H. As a result, three-phase short circuit control is started. As a result, as shown in FIG. 7, the operating point OP starts to move in a spiral from the start position Ps, as in the case of FIG. 4. The q-axis current value Iq that specifies the start position Ps is a negative value because the back electromotive force exceeds the terminal voltage of the smoothing capacitor 41, causing the smoothing capacitor 41 to be in a charged state. In the example shown in FIG. 7, the start position Ps is in the third quadrant where the d-axis and q-axis current values Id and Iq are negative, but the start position Ps is not necessarily in the third quadrant.

After that, the elapsed time Ltr reaches the judgment time Lth, and therefore the process of step S15 starts shutdown control at the first operating point P1. Then, a positive judgment is made in step S10, a negative judgment is made in step S11, and further, it is determined in step S12 that the first condition is satisfied. Therefore, the process of step S13 starts three-phase short circuit control again at the second operating point P2, and then the shutdown control starts again at the third operating point P3.

Then, three-phase short circuit control is started at the fourth operating point P4, and then shutdown control is started at the fifth operating point P5. Then, a negative determination is made in step S12, and the demagnetization control ends at the sixth operating point P6.

In the example shown in FIG. 7, three-phase short circuit control and shutdown control are repeated. The more times these controls are repeated, the smaller the absolute value of the negative d-axis current Id becomes at the end timing of the three-phase short circuit control.

In the example shown in FIG. 7, the trajectory of the operating point OP in the demagnetization control falls within the third quadrant. However, in this embodiment, since switching from three-phase short circuit control to shutdown control is performed based on the elapsed time Ltr, the trajectory of the operating point OP may not fall within the third quadrant, but may fall within the second quadrant. Even in this case, the permanent magnet 34 can be demagnetized by the negative d-axis current.

In addition, when three-phase short circuit control and shutdown control are repeated in the demagnetization control, as shown in FIG. 8, the judgment time Lth compared with the elapsed time Ltr may be set shorter than the previous judgment time Lth. In this case, the duration of the three-phase short circuit control becomes shorter than the previous duration of the three-phase short circuit control. Each time the three-phase short circuit control is performed, the magnetic flux density of the permanent magnet 34 decreases. Therefore, by gradually shortening the duration, it is possible to suitably prevent the permanent magnet 34 from being demagnetized excessively. Note that, although FIG. 8 shows an example in which the duration Lsdn of the shutdown control is also gradually shortened, the duration Lsdn of each time may be constant.

According to the present embodiment described above, it is possible to irreversibly demagnetize the permanent magnet 34 while suppressing the occurrence of failures in the inverter 40, etc., through simple controls such as three-phase short circuit control and shutdown control.

If it is determined that the DC current value Ip is smaller than the current threshold Ith, it is determined that demagnetization of the permanent magnet 34 is necessary. Therefore, the permanent magnet 34 can be demagnetized before the terminal voltage of the smoothing capacitor 41 rises excessively or the high-voltage battery 20 becomes overcharged.

When it is determined that the power supply voltage Vb is higher than the voltage threshold Vth, it is determined that demagnetization of the permanent magnet 34 is necessary. Therefore, it is possible to know that demagnetization is necessary before the withstand voltage of at least one of the high-voltage battery 20, the smoothing capacitor 41, the electrical equipment 42, and the inverter 40 is exceeded. This makes it possible to protect the high-voltage battery 20, the smoothing capacitor 41, the electrical equipment 42, and the inverter 40.

If it is determined that the element temperature Tdr is higher than the temperature threshold value Tdth, it is determined that demagnetization of the permanent magnet 34 is necessary. This makes it possible to protect the components of the inverter 40.

When it is determined that the elapsed time Ltr since the start of the three-phase short circuit control has reached the determination time Lth, the three-phase short circuit control is switched to the shutdown control. With this configuration, unlike a determination method that uses the electrical angle θe to determine the start timing of the shutdown control, even if an abnormality occurs that makes it impossible to grasp the electrical angle θe due to a failure of the angle detection unit 44, the start timing of the shutdown control can be properly determined.

After the three-phase short circuit control and the shutdown control are performed, it is determined again whether or not demagnetization of the permanent magnet 34 is necessary. Then, the three-phase short circuit control and the shutdown control are repeated until it is determined that demagnetization is not necessary. As a result, even if it is difficult to accurately determine the extent to which the permanent magnet 34 needs to be demagnetized, the permanent magnet 34 can be demagnetized as accurately as possible until the magnetic flux density of the permanent magnet 34 reaches the desired density.

In addition, according to this embodiment, since the shutdown control is executed in the demagnetization control, it is possible to prevent the permanent magnet 34 from being demagnetized too much, and also to prevent the components of the coil 31 and the inverter 40 from becoming overheated. Therefore, the rotating electric machine 30 and the inverter 40 after being demagnetized can be sold in the aftermarket as relatively good quality second-hand goods.

<Modification of the First Embodiment>
In step S12 of FIG. 6, the first condition may be that the sign of the DC current value Ip is negative. In more detail, when the necessity determination unit 57 determines that the sign of the DC current value Ip is positive, it determines that the smoothing capacitor 41 is not in a charged state and determines that demagnetization is not necessary. Then, the necessity determination unit 57 sets the logic of the demagnetization command to L. On the other hand, when the necessity determination unit 57 determines that the sign of the DC current value Ip is negative, it determines that the smoothing capacitor 41 is in a charged state and determines that demagnetization is necessary. Then, the necessity determination unit 57 sets the logic of the demagnetization command to H. When the sign of the DC current value Ip is negative, it is considered that a current flows through the high potential side path Lp in a direction in which the smoothing capacitor 41 is charged.

- In step S12 of FIG. 6, the first condition may be that the q-axis current value Iqr calculated by the dq conversion unit 53 is smaller than the q-axis current threshold Iqth. In more detail, when the necessity determination unit 57 determines that the q-axis current value Iqr is equal to or greater than the q-axis current threshold Iqth, it determines that the smoothing capacitor 41 is not in a charged state and that demagnetization is not required. On the other hand, when the necessity determination unit 57 determines that the q-axis current value Iqr is smaller than the q-axis current threshold Iqth, it determines that the smoothing capacitor 41 is in a charged state and that demagnetization is required.

The q-axis current threshold Iqth is set to 0 or a value slightly smaller than 0. Therefore, when the q-axis current value Iqr is smaller than the q-axis current threshold Iqth, it is considered that the smoothing capacitor 41 is being charged.

Incidentally, in this case, it is necessary to use the electrical angle θe to calculate the q-axis current value Iqr. For this reason, in step S11, it is sufficient that the abnormality in the configuration required to execute the three-phase short circuit control and shutdown control includes an abnormality in which the electrical angle θe and the phase current detection values cannot be obtained. An abnormality in which the electrical angle θe cannot be obtained includes an abnormality in the angle detection unit 44. An abnormality in which the phase current detection values cannot be obtained includes an abnormality in the phase current detection unit 43.

In addition to the q-axis current value Iqr, the d- and q-axis current values Idr and Iqr may be used. In this case, the necessity determination unit 57 may determine that the smoothing capacitor 41 is in a charged state, for example, when it determines that the torque of the rotating electric machine 30 determined from the d- and q-axis current values Idr and Iqr is a regenerative torque (<0).

The current value for determining whether the smoothing capacitor 41 is in a charging state is not limited to the current value in a rotating coordinate system (dq coordinate system), but may be the current value in a fixed coordinate system (UVW coordinate system) (e.g., the detection value of the phase current detection unit 43). In addition, the line voltage or phase voltage of the coil 31 may be used instead of the current value.

- In step S12 of FIG. 6, the first condition may be that the back electromotive voltage Vm generated in the coil 31 is higher than the electromotive voltage threshold Vα. The electromotive voltage threshold Vα is set to a value lower than the power supply voltage Vb, for example. When the necessity determination unit 57 determines that the back electromotive voltage Vm is equal to or lower than the electromotive voltage threshold Vα, it determines that the smoothing capacitor 41 is not in a charged state and that demagnetization is not required. On the other hand, when the necessity determination unit 57 determines that the back electromotive voltage Vm is higher than the electromotive voltage threshold Vα, it determines that the smoothing capacitor 41 is in a charged state and that demagnetization is required. Note that the necessity determination unit 57 may calculate the back electromotive voltage Vm based on, for example, the electrical angular velocity ωe of the rotor 33. In this case, the necessity determination unit 57 may calculate the electrical angular velocity ωe based on the electrical angle θe.

In this way, when the back electromotive voltage Vm is higher than the electromotive voltage threshold Vα, the back electromotive voltage becomes higher than the actual terminal voltage of the smoothing capacitor 41, and it is highly likely that the smoothing capacitor 41 is being charged.

- In step S12 of FIG. 6, a fourth condition may be added that the absolute value of the DC current value Ip is higher than the allowable current value (>0). In this case, the necessity determination unit 57 determines that demagnetization is necessary if any of the first to fourth conditions is met, and determines that demagnetization is not necessary if none of the first to fourth conditions is met.

Second Embodiment
The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the inverter control device 50 sets the determination time Lth used in step S14 in Fig. 6 to be longer as the magnet temperature Tmag detected by the second temperature detection unit 47 decreases, as shown in Fig. 9. This setting is based on the fact that the lower the temperature of the permanent magnet 34, the higher the magnetic flux density of the permanent magnet 34 becomes, and the greater the degree of demagnetization becomes necessary.

The inverter control device 50 may use the estimated temperature value of the permanent magnet 34 instead of the detection value of the first temperature detection unit 46 to set the judgment time Lth.

Third Embodiment
The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the first condition is changed to a condition related to the electrical angular velocity ωe, as shown in Fig. 10. In Fig. 10, the same processes as those shown in Fig. 6 are denoted by the same reference numerals for convenience.

In step S16, the first condition is that the electrical angular velocity ωe is higher than the speed threshold ωth. This condition is for determining whether the smoothing capacitor 41 is in a charging state. The speed threshold ωth may be set to an electrical angular velocity at which the back electromotive voltage of the coil 31 is higher than the lower limit of the possible terminal voltage range of the normal high-voltage battery 20 when the temperature of the permanent magnet 34 is at the lower limit of the possible temperature range (e.g., -40°C).

When the necessity determination unit 57 determines that the electrical angular velocity ωe is equal to or less than the speed threshold value ωth, it determines that demagnetization is unnecessary. On the other hand, when the necessity determination unit 57 determines that the electrical angular velocity ωe is higher than the speed threshold value ωth, it determines that demagnetization is necessary. Note that, for example, the mechanical angular velocity of the rotor 33 may be used instead of the electrical angular velocity ωe.

Fourth Embodiment
The fourth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the first condition is changed to a condition related to the magnet temperature Tmag, as shown in Fig. 11. In Fig. 11, the same processes as those shown in Fig. 6 are denoted by the same reference numerals for convenience.

In step S17, the first condition is that the magnet temperature Tmag is lower than the magnet threshold value Tgth. This condition is for determining whether the smoothing capacitor 41 is in a charged state. The magnet threshold value Tgth may be set to the temperature of the permanent magnet 34 at which the back electromotive force of the coil 31 becomes higher than the lower limit of the terminal voltage range that a normal high-voltage battery 20 can have when the rotation speed of the rotor 33 is at the upper limit (maximum rotation speed) of the possible speed range.

When the necessity determination unit 57 determines that the magnet temperature Tmag is equal to or higher than the magnet threshold value Tgth, it determines that demagnetization is unnecessary. On the other hand, when the necessity determination unit 57 determines that the magnet temperature Tmag is lower than the magnet threshold value Tgth, it determines that demagnetization is necessary.

In addition, the inverter control device 50 may use the estimated temperature value of the permanent magnet 34 instead of the detection value of the first temperature detection unit 46 as the temperature to be compared with the magnet threshold value Tgth.

Fifth Embodiment
The fifth embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the condition for switching from the three-phase short circuit control to the shutdown control is changed as shown in Fig. 12. In Fig. 12, the same processes as those shown in Fig. 6 are denoted by the same reference numerals for convenience.

In step S18, the necessity determination unit 57 sets the logic of the demagnetization command to H. Thereafter, the shutdown determination unit 58a acquires the d-axis current value Idr and determines whether the acquired d-axis current value Idr is a negative value and whether the absolute value of the d-axis current value Idr exceeds the d-axis current threshold value Idth (>0). If the shutdown determination unit 58a makes a positive determination in step S18, it switches the logic of the shutdown command output to the NOT circuit 58b from H to L. This causes the shutdown control to be executed in step S15.

According to the present embodiment described above, the d-axis current required to demagnetize the permanent magnet 34 can be grasped, so that the permanent magnet 34 can be appropriately demagnetized.

In addition, the d-axis current threshold Idth may be reduced each time the three-phase short circuit control and shutdown control are repeated in the demagnetization control.

Sixth Embodiment
The sixth embodiment will be described below with reference to the drawings, focusing on the differences from the fifth embodiment. In this embodiment, the condition for switching from the three-phase short circuit control to the shutdown control is changed as shown in Fig. 13. In Fig. 13, the same processes as those shown in Fig. 6 are denoted by the same reference numerals for convenience.

In step S19, the necessity determination unit 57 sets the logic of the demagnetization command to H. Thereafter, the shutdown determination unit 58a acquires the q-axis current value Iqr and determines whether the acquired q-axis current value Iqr has switched from a negative value to a positive value. If the shutdown determination unit 58a makes a positive determination in step S19, it determines that the rotating electric machine 30 has switched from a power generation state to a power running state, and switches the logic of the shutdown command output to the NOT circuit 58b from H to L. This causes the shutdown control to be executed in step S15.

According to the present embodiment described above, demagnetization control can be performed only during periods when an increase in the terminal voltage of the smoothing capacitor 41 is expected.

<Other embodiments>
Each of the above embodiments may be modified as follows.

- Three-phase short circuit control may be control that turns on the upper arm switches SWp of all phases and turns off the lower arm switches SWn of all phases.

- As shown in FIG. 14, in each phase, a connection switch SWφ may be provided between the connection point of the upper and lower arm switches SWp, SWn and the first end of the coil 31. In this case, in step S15 of FIG. 6, the inverter control device 50 may execute control to turn off the connection switch SWφ of each phase (corresponding to "shutdown control") instead of the shutdown control.

- Demagnetization control is not limited to irreversible demagnetization of the permanent magnet 34. For example, in demagnetization control, a negative d-axis current that can reversibly demagnetize the permanent magnet 34 may be passed.

- The switches that make up the inverter are not limited to IGBTs, but may be, for example, N-channel MOSFETs with built-in body diodes.

- The rotating electric machine and inverter are not limited to three-phase machines, but may be two-phase machines or four or more phase machines. Also, the rotating electric machine is not limited to an on-board motor, but may be an in-wheel motor built into the wheel.

- The vehicle is not limited to being a four-wheel drive vehicle, and may be one in which, for example, either the front wheels 11a or the rear wheels 11b are the drive wheels.

- The moving body on which the control system is mounted is not limited to a vehicle, but may be, for example, an aircraft or a ship. For example, if the moving body is an aircraft, the rotating electric machine that constitutes the control system serves as the power source for the aircraft's flight. Also, for example, if the moving body is a ship, the rotating electric machine that constitutes the control system serves as the power source for the ship's navigation.

The control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more dedicated computers configured by combining a processor and memory programmed to execute one or more functions with a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transient tangible recording medium as instructions executed by the computer.

10...vehicle, 20...high voltage battery, 30...rotating electric machine, 40...inverter, 50...inverter control device, 57...necessity determination unit, 58...demagnetization execution unit, SWp, SWn...upper and lower arm switches.

Claims (16)

A power storage unit (20, 41);
a rotating electric machine (30) including a rotor (33) having a permanent magnet (34) and a stator (32) having a multi-phase coil (31), and serving as a power source for moving a moving body (10);
an inverter (40) having upper and lower arm switches (SWp, SWn) with diodes (Dp, Dn) connected in inverse parallel, electrically connecting the power storage unit and the coil;
In an inverter control device (50) applied to a system including:
a necessity determination unit (57) for determining whether demagnetization of the permanent magnet is necessary;
a demagnetization execution unit (58) that, when it is determined by the necessity determination unit that demagnetization is necessary, executes short-circuit control to flow a return current through a closed circuit including the arm switch (SWn) that has been turned ON and the coil by turning off all phases of the other arm switch (SWp) of the upper and lower arm switches, and performs cut-off control to prevent the return current from flowing after the short-circuit control is executed ;
The necessity determination unit determines whether or not demagnetization is necessary again after the short circuit control and the cut-off control are executed by the demagnetization execution unit,
The demagnetization execution unit repeats execution of the short-circuit control and the cut-off control until the necessity determination unit determines that demagnetization is unnecessary . A power storage unit (20, 41);
a rotating electric machine (30) including a rotor (33) having a permanent magnet (34) and a stator (32) having a multi-phase coil (31), and serving as a power source for moving a moving body (10);
an inverter (40) having upper and lower arm switches (SWp, SWn) with diodes (Dp, Dn) connected in inverse parallel, electrically connecting the power storage unit and the coil;
In an inverter control device (50) applied to a system including:
a necessity determination unit (57) for determining whether demagnetization of the permanent magnet is necessary;
a demagnetization execution unit (58) that, when it is determined by the necessity determination unit that demagnetization is necessary, executes short-circuit control to flow a return current through a closed circuit including the arm switch (SWn) that has been turned ON and the coil by turning off all phases of the other arm switch (SWp) of the upper and lower arm switches, and performs cut-off control to prevent the return current from flowing after the short-circuit control is executed ;
The demagnetization execution unit starts the cut-off control when it determines that a d-axis current (Idr) for field weakening exceeds a d-axis current threshold (Idth) after starting the short-circuit control . A power storage unit (20, 41);
a rotating electric machine (30) including a rotor (33) having a permanent magnet (34) and a stator (32) having a multi-phase coil (31), and serving as a power source for moving a moving body (10);
an inverter (40) having upper and lower arm switches (SWp, SWn) with diodes (Dp, Dn) connected in inverse parallel, electrically connecting the power storage unit and the coil;
In an inverter control device (50) applied to a system including:
a necessity determination unit (57) for determining whether demagnetization of the permanent magnet is necessary;
a demagnetization execution unit (58) that, when it is determined by the necessity determination unit that demagnetization is necessary, executes short-circuit control to flow a return current through a closed circuit including the arm switch (SWn) that has been turned ON and the coil by turning off all phases of the other arm switch (SWp) of the upper and lower arm switches, and performs cut-off control to prevent the return current from flowing after the short-circuit control is executed ;
The demagnetization execution unit starts the cutoff control when it determines that the rotating electric machine has switched from a power generation state to a power running state after starting the short circuit control . 4. The inverter control device according to claim 1, wherein the demagnetization execution unit sets a duration (Lth) of the short circuit control to be shorter than a duration of a previous short circuit control. A power storage unit (20, 41);
a rotating electric machine (30) including a rotor (33) having a permanent magnet (34) and a stator (32) having a multi-phase coil (31), and serving as a power source for moving a moving body (10);
an inverter (40) having upper and lower arm switches (SWp, SWn) with diodes (Dp, Dn) connected in inverse parallel, electrically connecting the power storage unit and the coil;
In an inverter control device (50) applied to a system including:
a necessity determination unit (57) for determining whether demagnetization of the permanent magnet is necessary;
a demagnetization execution unit (58) that, when it is determined by the necessity determination unit that demagnetization is necessary, executes short-circuit control to flow a return current through a closed circuit including the arm switch (SWn) that has been turned ON and the coil by turning off all phases of the other arm switch (SWp) of the upper and lower arm switches, and performs cut-off control to prevent the return current from flowing after the short-circuit control is executed ;
The demagnetization execution unit extends the duration (Lth) of the short circuit control as the temperature (Tmag) of the permanent magnet decreases . 6. The inverter control device according to claim 1 , wherein the necessity determination unit determines that demagnetization is necessary when it is determined that the voltage (Vb) of the power storage unit has exceeded a voltage threshold ( Vth ) that is lower than a withstand voltage of the power storage unit. The inverter control device according to claim 1 , wherein the necessity determining unit determines that demagnetization is necessary on condition that it is determined that the power storage unit is in a charged state. 8. The inverter control device according to claim 7, wherein the necessity determination unit determines whether the power storage unit is in a charged state, based on a direct current (Ip) flowing between the power storage unit and the inverter, a back electromotive force (Vm) output from the coil via the inverter, a rotational speed (ωe) of the rotor, or a temperature ( Tmag ) of the permanent magnet. The inverter control device according to any one of claims 1 to 8 , wherein the necessity determination unit determines that demagnetization is necessary when a temperature (Tdr) of the diode, the upper arm switch, or the lower arm switch is higher than a temperature threshold (Tdth). The inverter control device according to any one of claims 1 to 9, wherein the necessity determining unit determines whether or not demagnetization is necessary on condition that a command to determine demagnetization of the permanent magnet is received from a host control device ( 80 ) provided outside the inverter control device. 6. The inverter control device according to claim 1, wherein the demagnetization execution unit starts the cutoff control when it is determined that an elapsed time (Ltr) from the start of the short circuit control has reached a judgment time (Lth). The inverter control device according to any one of claims 1 to 11 , wherein the cutoff control is a control for turning off the upper and lower arm switches of all phases. A power storage unit (20, 41);
a rotating electric machine (30) including a rotor (33) having a permanent magnet (34) and a stator (32) having a multi-phase coil (31), and serving as a power source for moving a moving body (10);
an inverter (40) having upper and lower arm switches (SWp, SWn) with diodes (Dp, Dn) connected in inverse parallel, electrically connecting the power storage unit and the coil;
An inverter control device (50);
In a program applied to a system comprising:
The inverter control device includes:
a necessity determination process for determining whether demagnetization of the permanent magnet is necessary;
when it is determined by the necessity determination process that demagnetization is necessary, one of the upper and lower arm switches (SWn) is turned ON for all phases and the other arm switch (SWp) is turned OFF for all phases, thereby executing a short-circuit control for flowing a return current through a closed circuit including the arm switch that is turned ON and the coil, and after the short-circuit control is executed, a demagnetization execution process is executed to perform a cut-off control for preventing the return current from flowing,
In the necessity determination process, it is determined whether or not demagnetization is necessary again after the short circuit control and the cut-off control are executed by the demagnetization execution process,
a program for repeating execution of the short circuit control and the cut-off control in the demagnetization execution process until it is determined by the necessity determination process that demagnetization is unnecessary; A power storage unit (20, 41);
a rotating electric machine (30) including a rotor (33) having a permanent magnet (34) and a stator (32) having a multi-phase coil (31), and serving as a power source for moving a moving body (10);
an inverter (40) having upper and lower arm switches (SWp, SWn) with diodes (Dp, Dn) connected in inverse parallel, electrically connecting the power storage unit and the coil;
An inverter control device (50);
In a program applied to a system comprising:
The inverter control device includes:
a necessity determination process for determining whether demagnetization of the permanent magnet is necessary;
when it is determined by the necessity determination process that demagnetization is necessary, one of the upper and lower arm switches (SWn) is turned ON for all phases and the other arm switch (SWp) is turned OFF for all phases, thereby executing a short-circuit control for flowing a return current through a closed circuit including the arm switch that is turned ON and the coil, and after the short-circuit control is executed, a demagnetization execution process is executed to perform a cut-off control for preventing the return current from flowing,
a program for starting the cut-off control when it is determined in the demagnetization execution process that a d-axis current (Idr) for field weakening exceeds a d-axis current threshold (Idth) after starting the short circuit control. A power storage unit (20, 41);
a rotating electric machine (30) including a rotor (33) having a permanent magnet (34) and a stator (32) having a multi-phase coil (31), and serving as a power source for moving a moving body (10);
an inverter (40) having upper and lower arm switches (SWp, SWn) with diodes (Dp, Dn) connected in inverse parallel, electrically connecting the power storage unit and the coil;
An inverter control device (50);
In a program applied to a system comprising:
The inverter control device includes:
a necessity determination process for determining whether demagnetization of the permanent magnet is necessary;
when it is determined by the necessity determination process that demagnetization is necessary, one of the upper and lower arm switches (SWn) is turned ON for all phases and the other arm switch (SWp) is turned OFF for all phases, thereby executing a short-circuit control for flowing a return current through a closed circuit including the arm switch that is turned ON and the coil, and after the short-circuit control is executed, a demagnetization execution process is executed to perform a cut-off control for preventing the return current from flowing,
a program for starting the cutoff control when it is determined that the rotating electric machine has switched from a power generation state to a power running state after starting the short circuit control in the demagnetization execution process; A power storage unit (20, 41);
a rotating electric machine (30) including a rotor (33) having a permanent magnet (34) and a stator (32) having a multi-phase coil (31), and serving as a power source for moving a moving body (10);
an inverter (40) having upper and lower arm switches (SWp, SWn) with diodes (Dp, Dn) connected in inverse parallel, electrically connecting the power storage unit and the coil;
An inverter control device (50);
In a program applied to a system comprising:
The inverter control device includes:
a necessity determination process for determining whether demagnetization of the permanent magnet is necessary;
when it is determined by the necessity determination process that demagnetization is necessary, one of the upper and lower arm switches (SWn) is turned ON for all phases and the other arm switch (SWp) is turned OFF for all phases, thereby executing a short-circuit control for flowing a return current through a closed circuit including the arm switch that is turned ON and the coil, and after the short-circuit control is executed, a demagnetization execution process is executed to perform a cut-off control for preventing the return current from flowing,
A program in which, in the demagnetization execution process, the lower the temperature (Tmag) of the permanent magnet, the longer the duration (Lth) of the short circuit control.

Images