JP7632197B2 - INVERTER CONTROL DEVICE, PROGRAM, AND INVERTER CONTROL METHOD - Google Patents

Description

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

Conventionally, as described in, for example, Patent Document 1, there is known an inverter control device that is applied to a control system that includes a rotating electric machine having a stator winding and an inverter electrically connected to the stator winding.

Japanese Patent Application Publication No. 3-198601

In the high-speed rotation region of the rotating electric machine, a field-weakening control may be performed in which a field-weakening current is passed through the stator winding. In this case, the magnitude of the current vector passed through the stator winding to generate a predetermined torque in the rotating electric machine is larger than when field-weakening control is not performed. For this reason, when field-weakening control is performed, the inverter and the rotating electric machine generate more heat than when field-weakening control is not performed, and at least one of the inverter and the rotating electric machine may become overheated.

To prevent at least one of the inverter and the rotating electric machine from overheating, it is possible to reduce the command torque of the rotating electric machine. However, in this case, there is a concern that the rotating electric machine may not be able to continue to be driven properly.

The main object of the present invention is to provide an inverter control device , a program , and an inverter control method that can prevent the inverter and the rotating electric machine from becoming overheated while suppressing a torque decrease in the rotating electric machine or maintaining the torque.

The present invention relates to an inverter control device that is applied to a control system that includes a rotating electric machine having a stator winding and an inverter electrically connected to the stator winding, and includes a switch control unit that executes switching control of the inverter based on a comparison of the magnitude between a command voltage of the stator winding and a carrier signal, and an acquisition unit that acquires the temperature of at least one of the inverter and the rotating electric machine. When the switching control is executed while a field-weakening current is passed through the stator winding, the switch control unit reduces the frequency of the carrier signal and decreases the field-weakening current when it is determined that the acquired temperature exceeds a temperature threshold value.

In the present invention, when switching control is being performed while a field-weakening current is flowing through the stator winding, if it is determined that the temperature acquired by the acquisition unit exceeds the temperature threshold, the frequency of the carrier signal is reduced. This reduces the number of switching operations per unit time, thereby increasing the voltage utilization rate of the inverter and suppressing the amount of heat generated by the inverter and rotating electric machine.

By increasing the voltage utilization rate, the rotating electric machine has more torque. Therefore, in the present invention, the field weakening current is reduced. This reduces the magnitude of the current vector flowing through the stator winding, suppresses the amount of heat generated by the inverter and the rotating electric machine, and prevents the inverter and the rotating electric machine from overheating. In this case, the torque reduction caused by the reduction in the field weakening current can be suppressed by improving the voltage utilization rate, and the torque reduction caused by the reduction in the field weakening current can be compensated for by improving the voltage utilization rate.

According to the present invention described above, it is possible to prevent the inverter and the rotating electric machine from overheating while suppressing the torque drop of the rotating electric machine or maintaining the torque.

FIG. 1 is an overall configuration diagram of a control system according to a first embodiment. FIG. 4 is a functional block diagram of torque control executed by the control device. 5 is a diagram showing changes in a command voltage and a carrier signal in switching control. FIG. 4 is a flowchart showing a procedure for overheat protection control. FIG. 4 is a diagram showing a method for setting the frequency of a carrier signal. FIG. 4 is a diagram showing a method for setting a field-weakening current. 5 is a time chart showing an example of a case where overheat protection control is performed. FIG. 11 is a diagram showing a method for setting the frequency of a carrier signal according to a modified example of the first embodiment. 10 is a flowchart showing a processing procedure of overheat protection control according to a second embodiment. 13 is a flowchart showing a processing procedure of overheat protection control according to a third embodiment. 11 is a flowchart showing the procedure of a loss comparison process.

First Embodiment
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a control device according to the present invention will now be described with reference to the drawings. In this embodiment, a control system including a control device is mounted on a vehicle such as an electric vehicle.

As shown in FIG. 1, the vehicle 10 is equipped with a rotating electric machine 20. The rotating electric machine 20 is a three-phase synchronous machine equipped with star-connected stator windings 21 for each phase. The stator windings 21 for each phase are arranged offset by 120° in electrical angle. The rotating electric machine 20 of this embodiment is a permanent magnet synchronous machine equipped with permanent magnets as field poles in the rotor 22.

The rotating electric machine 20 is an in-vehicle main engine, and its rotor 22 is capable of transmitting power to the drive wheels 11 of the vehicle 10. The torque generated by the rotating electric machine 20 functioning as an electric motor is transmitted from the rotor 22 to the drive wheels 11. This causes the drive wheels 11 to rotate. The rotating electric machine 20 may be an in-wheel motor that is integrally provided on the wheels of the vehicle 10, or a so-called on-board motor that is provided on the body of the vehicle 10.

The vehicle 10 includes an inverter 30, a capacitor 31, and a storage battery 12, which is a DC power source. The inverter 30 includes three phases of a series connection of an upper arm switch SWH and a lower arm switch SWL. In this embodiment, each switch SWH, SWL is a voltage-controlled semiconductor switching element, specifically an IGBT. Therefore, the high-potential terminal of each switch SWH, SWL is a collector, and the low-potential terminal is an emitter. Freewheel diodes DH, DL are connected in inverse parallel to each switch SWH, SWL.

In each phase, the first end of the stator winding 21 is connected to the emitter of the upper arm switch SWH and the collector of the lower arm switch SWL. The second ends of the stator windings 21 of each phase are connected to each other at the neutral point. In this embodiment, the stator windings 21 of each phase are set to have the same number of turns.

The collector of the upper arm switch SWH of each phase and the positive terminal of the storage battery 12 are connected by a positive side bus Lp. The emitter of the lower arm switch SWL of each phase and the negative terminal of the storage battery 12 are connected by a negative side bus Ln. The positive side bus Lp and the negative side bus Ln are connected by a capacitor 31. The capacitor 31 may be built into the inverter 30 or may be provided outside the inverter 30.

The storage battery 12 is, for example, a battery pack, and the terminal voltage of the storage battery 12 is, for example, several hundred volts. The storage battery 12 is, for example, a secondary battery such as a lithium ion battery or a nickel-metal hydride battery.

The vehicle 10 is equipped with a current sensor 32, a voltage sensor 33, a rotation angle sensor 34, a motor temperature sensor 35, an inverter temperature sensor 36, and a control device 37. The current sensor 32 detects the current flowing through the stator windings 21 of at least two of the phases. The voltage sensor 33 detects the terminal voltage of the capacitor 31 as the power supply voltage Vdc. The rotation angle sensor 34 is, for example, a resolver, and detects the rotation angle (specifically, the electrical angle) of the rotor 22. The motor temperature sensor 35 is, for example, a thermistor, and detects the temperature of the rotating electric machine 20 (for example, the temperature of the stator windings 21) as the motor temperature Tmgd. The inverter temperature sensor 36 is, for example, a thermistor or a temperature-sensitive diode, and detects the temperature of the inverter 30 (for example, the temperature of the upper and lower arm switches SWH and SWL) as the inverter temperature Tinvd. The detection values of the sensors 32 to 36 are input to the control device 37.

The control device 37 is mainly composed of a microcomputer 37a, which is equipped with a CPU. The functions provided by the microcomputer 37a can be provided by software recorded in a physical memory device and a computer that executes the software, by software alone, by hardware alone, or by a combination of these. For example, when the microcomputer 37a is provided by an electronic circuit that is hardware, it can be provided by a digital circuit including a large number of logic circuits, or an analog circuit. For example, the microcomputer 37a executes a program stored in a non-transitory tangible storage medium as a storage unit provided in the microcomputer 37a. The program includes, for example, a program for the process shown in FIG. 4. When the program is executed, a method corresponding to the program is executed. The storage unit is, for example, a non-volatile memory. Note that the program stored in the storage unit can be updated, for example, via a network such as the Internet.

The control device 37 receives the command torque Trq*. The control device 37 performs switching control of the switches SWH and SWL that constitute the inverter 30 to control the torque of the rotating electric machine 20 to the received command torque Trq*. In each phase, the upper arm switch SWH and the lower arm switch SWL are alternately turned on with a dead time therebetween.

Next, the torque control of the rotating electric machine 20 executed by the control device 37 will be described with reference to FIG. 2. In the example shown in FIG. 2, current feedback control is performed as the torque control. Note that torque feedback control may be performed instead of current feedback control.

The command current setting unit 40 sets the d-axis and q-axis command currents Id* and Iq* based on the command torque Trq*, the rotation speed Nm of the rotor 22, and the frequency fr of the carrier signal Sig (described later). The d-axis and q-axis command currents Id* and Iq* may be calculated, for example, by minimum current maximum torque control (MTPA). The command current setting unit 40 may set the d-axis and q-axis command currents Id* and Iq* based on map information or formula information that correlates the command torque Trq*, the rotation speed Nm of the rotor 22, the frequency fr of the carrier signal Sig, and the d-axis and q-axis command currents Id* and Iq*. The rotation speed Nm of the rotor 22 may be calculated, for example, based on the detection value of the rotation angle sensor 34.

The two-phase conversion unit 41 converts the U-, V-, and W-phase currents in the three-phase fixed coordinate system into a d-axis current Idr and a q-axis current Iqr in a two-phase rotating coordinate system (dq coordinate system) based on the detection value of the current sensor 32 and the electrical angle θe detected by the rotation angle sensor 34.

The d-axis deviation calculation unit 42 calculates the d-axis current deviation ΔId by subtracting the d-axis current Idr from the d-axis command current Id*. The q-axis deviation calculation unit 43 calculates the q-axis current deviation ΔIq by subtracting the q-axis current Iqr from the q-axis command current Iq*.

The d-axis command voltage calculation unit 44 calculates a d-axis command voltage Vd based on the d-axis current deviation ΔId as a manipulated variable for feedback-controlling the d-axis current Idr to the d-axis command current Id*. The q-axis command voltage calculation unit 45 calculates a q-axis command voltage Vq based on the q-axis current deviation ΔIq as a manipulated variable for feedback-controlling the q-axis current Iqr to the q-axis command current Iq*. The feedback control used by the d-axis command voltage calculation unit 44 and the q-axis command voltage calculation unit 45 may be, for example, proportional-integral control.

The three-phase conversion unit 47 converts the d- and q-axis command voltages Vd and Vq in the two-phase rotating coordinate system into U-, V- and W-phase command voltages VU*, VV* and VW* in the three-phase fixed coordinate system based on the d- and q-axis command voltages Vd and Vq and the electrical angle θe output from the d- and q-axis command voltage calculation units 44 and 45. In this embodiment, the U-, V- and W-phase command voltages VU*, VV* and VW* have sinusoidal waveforms with a phase shift of 120° in electrical angle.

The signal generating unit 48 generates the drive signals GUH, GUL for the upper and lower arm switches SWH, SWL of the U phase, the drive signals GVH, GVL for the upper and lower arm switches SWH, SWL of the V phase, and the drive signals GWH, GWL for the upper and lower arm switches SWH, SWL of the W phase by three-phase modulation based on the U-, V-, and W-phase command voltages VU*, VV*, and VW* and the power supply voltage Vdc. In more detail, taking the U phase as an example, the signal generating unit 48 calculates the U-phase normalized command voltage VUS by dividing the U-phase command voltage VU* by 1/2 the power supply voltage Vdc. As shown in FIG. 3, the signal generating unit 48 calculates the U-phase PWM signal GU* based on a comparison of the magnitude between the U-phase normalized command voltage VUS and the carrier signal Sig. The signal generating unit 48 generates the upper and lower arm drive signals GUH and GUL for the upper and lower arm switches SWH and SWL of the U phase based on the U phase PWM signal GU* and the logical inversion signal of the U phase PWM signal GU*. Note that FIG. 3 shows the transition of the carrier signal Sig etc. over a period of 180 electrical degrees.

The signal generating unit 48 outputs the generated U-phase upper and lower arm drive signals GUH, GUL to the gates of the U-phase upper and lower arm switches SWH, SWL, outputs the generated V-phase upper and lower arm drive signals GVH, GVL to the gates of the V-phase upper and lower arm switches SWH, SWL, and outputs the generated W-phase upper and lower arm drive signals GWH, GWL to the gates of the W-phase upper and lower arm switches SWH, SWL. This allows sine wave PWM control to be performed as switching control for the inverter 30. The control period of the control device 37 is sufficiently shorter than the period of the carrier signal Sig. In addition, the carrier signal Sig in this embodiment is a triangular wave signal with equal rising and falling speeds.

In this embodiment, when a field-weakening current is flowing through the stator winding 21, the control device 37 executes overheat protection control to reduce the field-weakening current while lowering the frequency fr of the carrier signal Sig in order to prevent the inverter 30 and the rotating electric machine 20 from overheating.

Next, the overheat protection control executed by the control device 37 will be described with reference to FIG. 4. The overheat protection control shown in FIG. 4 is executed repeatedly at a predetermined control period, for example.

In step S10, it is determined whether field weakening control, which passes a field weakening current through the stator winding 21, is being performed.

If it is determined in step S10 that field-weakening control is being performed, the process proceeds to step S11, where the motor temperature Tmgd (corresponding to the "first temperature") detected by the motor temperature sensor 35 and the inverter temperature Tinvd (corresponding to the "second temperature") detected by the inverter temperature sensor 36 are acquired. In this embodiment, the allowable upper limit temperature of the inverter 30 is higher than the allowable upper limit temperature of the rotating electric machine 20. The process of step S11 corresponds to the "acquisition unit."

In step S12, it is determined whether the control mode is the overheat protection mode, which is either the normal mode or the overheat protection mode described below. In the normal mode, sine wave PWM control is performed while the frequency fr of the carrier signal Sig is set to a predetermined frequency fc. The predetermined frequency fc is set based on the characteristics of the rotating electric machine 20 and the operating conditions of the rotating electric machine 20, and is set to 15 kHz in this embodiment.

If it is determined in step S12 that the normal mode is selected, the process proceeds to step S13, where it is determined whether the motor temperature Tmgd has exceeded the first protection start threshold TAH (e.g., 140°C). The first protection start threshold TAH corresponds to the "first temperature threshold" and may be set to a value lower than the allowable upper limit temperature of the rotating electric machine 20.

If it is determined in step S13 that the motor temperature Tmgd is equal to or lower than the first protection start threshold TAH, the process proceeds to step S14, where it is determined whether the inverter temperature Tinvd has exceeded the second protection start threshold TBH. In this embodiment, the second protection start threshold TBH is set higher than the first protection start threshold TAH. This is because the allowable upper limit temperature of the inverter 30 is higher than the allowable upper limit temperature of the rotating electric machine 20. The second protection start threshold TBH corresponds to the "second temperature threshold" and may be set to a value lower than the allowable upper limit temperature of the inverter 30.

If it is determined in step S14 that the inverter temperature Tinvd is equal to or lower than the second protection start threshold TBH, the process proceeds to step S15, and the control mode is changed to normal mode.

On the other hand, if it is determined in step S13 that the motor temperature Tmgd exceeds the first protection start threshold TAH, the rotating electric machine 20 may be overheated, so the process proceeds to step S16. In step S16, the control mode is set to the overheat protection mode. In the overheat protection mode, the frequency fr of the carrier signal Sig is reduced while performing sine wave PWM control. In this embodiment, as shown in FIG. 5, the higher the motor temperature Tmgd, the more the frequency fr of the carrier signal Sig is reduced. When the motor temperature Tmgd is equal to or higher than the upper limit temperature TAK, the frequency fr of the carrier signal Sig is prevented from falling below the lower limit frequency fL. The frequency fr of the carrier signal Sig is limited to the lower limit frequency fL in order to avoid an increase in loss due to a decrease in controllability of the phase current flowing through the stator winding 21 and a distortion of the waveform of the phase current.

When the motor temperature Tmgd decreases, the frequency fr of the carrier signal Sig is increased. In this case, for example, as shown in FIG. 5, if the frequency fr of the carrier signal Sig is a predetermined frequency fc at the time when the motor temperature Tmgd decreases and reaches the first protection release threshold TAL, the manner in which the frequency fr increases with the decrease in the motor temperature Tmgd can be freely determined in the hatched area in FIG. 5.

In the overheat protection mode, the field weakening current is reduced based on the reduced frequency fr of the carrier signal Sig. More specifically, the voltage utilization rate of the inverter 30 increases due to the reduction in the frequency fr of the carrier signal Sig, and the voltage applied to the stator winding 21 increases. In this case, a current can be passed through the stator winding 21 while reducing the field weakening current. Therefore, in the command current setting unit 40, as shown in FIG. 6, the d-axis command current Id* is set so that the field weakening current becomes smaller as the frequency fr of the reduced carrier signal Sig becomes lower. The map information or formula information relating the d-axis command current Id* and the frequency fr of the carrier signal Sig may be created for each operating condition determined by the torque and rotation speed Nm of the rotating electric machine 20, taking into consideration the expected reduction in the field weakening current due to the improvement in the voltage utilization rate caused by the reduction in the frequency fr of the carrier signal Sig.

Figure 7 shows an example of a case where overheat protection control is implemented. In Figure 7, (a) shows the change in motor temperature Tmgd, (b) shows the change in frequency fr of carrier signal Sig, and (c) shows the change in field weakening current. At time t1, the control device 37 determines that the motor temperature Tmgd has exceeded the first protection start threshold TAH. Therefore, the higher the motor temperature Tmgd, the more the control device 37 reduces the frequency fr of carrier signal Sig. Also, the lower the reduced frequency fr of carrier signal Sig, the more the control device 37 reduces the field weakening current. In the example shown in Figure 7, the frequency fr of carrier signal Sig is reduced and the field weakening current is reduced, so that the rate of increase of motor temperature Tmgd gradually decreases.

Returning to the explanation of FIG. 4, after the processing of step S16 is completed, if it is determined in step S12 that the control mode is the overheat protection mode, the process proceeds to step S17. In step S17, it is determined whether the motor temperature Tmgd has become equal to or lower than the first protection release threshold TAL (<TAH). In this embodiment, the first protection release threshold TAL is the first protection start threshold TAH minus the first predetermined temperature ΔT1. If it is determined in step S17 that the motor temperature Tmgd is higher than the first protection release threshold TAL, the process proceeds to step S16. On the other hand, if it is determined in step S17 that the motor temperature Tmgd has become equal to or lower than the first protection release threshold TAL, the process proceeds to step S18.

In step S18, it is determined whether the inverter temperature Tinvd has become equal to or lower than the second protection release threshold TBL (<TBH). In this embodiment, the second protection release threshold TBL is the second protection start threshold TBH minus the second predetermined temperature ΔT2. If it is determined in step S18 that the inverter temperature Tinvd has become equal to or lower than the second protection release threshold TBL, the process proceeds to step S15. This cancels the overheat protection mode and switches the control mode to the normal mode. The second predetermined temperature ΔT2 may be the same value as the first predetermined temperature ΔT1, or may be a different value.

By providing the processing of steps S17 and S18, it is possible to avoid a phenomenon in which the control mode alternates between the normal mode and the overheat protection mode (so-called hunting).

When the control mode is the normal mode, if it is determined in step S14 that the inverter temperature Tinvd exceeds the second protection start threshold TBH, the inverter 30 may be overheated, so the process proceeds to step S19. In step S19, the control mode is set to the overheat protection mode, similar to the process in step S16. In detail, as shown in FIG. 5, the higher the inverter temperature Tinvd, the more the frequency fr of the carrier signal Sig is reduced. When the motor temperature Tmgd is equal to or higher than the upper limit temperature TAK, the frequency fr of the carrier signal Sig is prevented from falling below the lower limit frequency fL. Incidentally, the upper limit temperature TBK compared with the inverter temperature Tinvd is set higher than the upper limit temperature TAK compared with the motor temperature Tmgd, for example. Also, as shown in FIG. 6, the d-axis command current Id* is set so that the field weakening current becomes smaller as the reduced frequency fr of the carrier signal Sig becomes lower.

When the inverter temperature Tinvd drops, the frequency fr of the carrier signal Sig is increased. In this case, for example, as shown in FIG. 5, if the frequency fr of the carrier signal Sig is a predetermined frequency fc at the time when the inverter temperature Tinvd drops to the second protection release threshold TBL, the manner in which the frequency fr increases with the drop in the motor temperature Tmgd can be freely determined in the hatched region in FIG. 5.

Returning to the explanation of FIG. 4, after the processing of step S19, if it is determined in step S12 that the control mode is the overheat protection mode, the process proceeds to step S17. Note that in this embodiment, the control system is configured so that in a situation in which the processing of step S19 is performed, a positive determination is made in step S17. Thereafter, if a negative determination is made in step S18, the process proceeds to step S19.

On the other hand, if it is determined in step S18 that the inverter temperature Tinvd is equal to or lower than the second protection release threshold TBL, the process proceeds to step S15. This causes the overheat protection mode to be released and the control mode to be switched to the normal mode. The processes in steps S12 to S18 correspond to the "switch control unit."

The present embodiment described above provides the following advantages:

In this embodiment, when PWM control is being performed while a field-weakening current is flowing through the stator winding 21, if it is determined that either the condition that the motor temperature Tmgd exceeds the first protection start threshold TAH or the condition that the inverter temperature Tinvd exceeds the second protection start threshold TBH is satisfied, the control mode is switched to the overheat protection mode. More specifically, in the overheat protection mode, the frequency fr of the carrier signal Sig is reduced. This reduces the number of switching operations per unit time, and thus increases the voltage utilization rate of the inverter 30. As a result, the amount of heat generated by the inverter 30 and the rotating electric machine 20 is suppressed, and the inverter 30 and the rotating electric machine 20 can be prevented from overheating.

By increasing the voltage utilization rate, the rotating electric machine 20 has more torque. Therefore, in the overheat protection mode, the field weakening current is reduced. This reduces the magnitude of the current vector flowing through the stator winding 21, suppresses the amount of heat generated by the inverter 30 and the rotating electric machine 20, and prevents the inverter 30 and the rotating electric machine 20 from overheating.

According to the present embodiment described above, it is possible to prevent the inverter and the rotating electric machine 20 from overheating while suppressing the torque decrease of the rotating electric machine 20 or maintaining the torque.

In the overheat protection mode, the higher the motor temperature Tmgd and the inverter temperature Tinvd, the more the frequency fr of the carrier signal Sig is reduced. This allows overheat protection to be performed appropriately in response to changes in the motor temperature Tmgd and the inverter temperature Tinvd.

In the overheat protection mode, the lower the frequency fr of the reduced carrier signal Sig, the more the field weakening current is reduced. In other words, the absolute value of the d-axis command current Id* is reduced while taking into account the expected reduction in the field weakening current due to the improvement in the voltage utilization rate caused by the reduction in the frequency fr of the carrier signal Sig. This allows for appropriate overheat protection.

As the conditions for starting the overheat protection mode, a first condition that the inverter temperature Tinvd exceeds the second protection start threshold TBH and a second condition that the motor temperature Tmgd exceeds the first protection start threshold TAH are set. When the first condition is met, the frequency fr and the field weakening current of the carrier signal Sig are set based on the inverter temperature Tinvd, not on the motor temperature Tmgd. On the other hand, when the second condition is met, the frequency fr and the field weakening current of the carrier signal Sig are set based on the motor temperature Tmgd, not on the inverter temperature Tinvd. This allows proper overheat protection of the inverter 30 and the rotating electric machine 20, which have different allowable upper limit temperatures.

By reducing the frequency fr of the carrier signal Sig, the voltage utilization rate can be improved, but the controllability of the phase current flowing through the stator winding 21 decreases, and the waveform of the phase current becomes distorted, causing increased noise and vibration of the rotating electric machine 20. For this reason, it is desirable to avoid this as much as possible during normal times when there is no risk of overheating. However, in this embodiment, the overheat protection mode is set as a temporary measure when there is a risk of overheating. This makes it possible to suppress or compensate for the torque reduction that accompanies a decrease in the field weakening current, and allows the vehicle 10 to continue running as much as possible while avoiding overheating abnormalities.

<Modification of the First Embodiment>
The allowable upper limit temperature of the rotating electric machine 20 may be higher than the allowable upper limit temperature of the inverter 30. In this case, it is sufficient that the first protection start threshold TAH is set higher than the second protection start threshold TBH.

- The first predetermined temperature ΔT1 may be set to 0. In this case, the first protection release threshold TAL and the first protection start threshold TAH will be the same value. Also, the second predetermined temperature ΔT2 may be set to 0. In this case, the second protection release threshold TBL and the second protection start threshold TBH will be the same value.

The control device 37 may set the frequency fr of the carrier signal Sig using the method shown in FIG. 8 instead of the method shown in FIG. 5. In more detail, in the case of overheat protection of the rotating electric machine 20, when the control device 37 determines that the motor temperature Tmgd has exceeded the first protection start threshold TAH, the control device 37 reduces the frequency fr of the carrier signal Sig in a stepwise manner from the predetermined frequency fc to the lower limit frequency fL. On the other hand, when the control device 37 determines that the motor temperature Tmgd has become equal to or lower than the first protection release threshold TAL in a case where the frequency fr of the carrier signal Sig is set to the lower limit frequency fL, the control device 37 increases the frequency fr of the carrier signal Sig in a stepwise manner from the lower limit frequency fL to the predetermined frequency fc.

Next, regarding the overheat protection of the inverter 30, when the control device 37 determines that the inverter temperature Tinvd exceeds the second protection start threshold TBH, it reduces the frequency fr of the carrier signal Sig in a stepwise manner from the predetermined frequency fc to the lower limit frequency fL. On the other hand, when the control device 37 determines that the inverter temperature Tinvd is equal to or lower than the second protection release threshold TBL in a case where the frequency fr of the carrier signal Sig is set to the lower limit frequency fL, it increases the frequency fr of the carrier signal Sig in a stepwise manner from the lower limit frequency fL to the predetermined frequency fc.

Second Embodiment
The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. The allowable upper limit temperature of the inverter 30 is higher than the allowable upper limit temperature of the rotating electric machine 20. Therefore, the inverter 30 has higher thermal reliability than the rotating electric machine 20. By executing the overheat protection control for the rotating electric machine 20, the heat generation of the inverter 30 is also suppressed, so it is considered that the inverter 30 can be protected from overheat. In view of this, in this embodiment, the overheat protection control shown in FIG. 9 is executed by the control device 37. The overheat protection control shown in FIG. 9 is executed repeatedly at a predetermined control period, for example. In this embodiment, the first protection start threshold TAH is referred to as the protection start threshold TAH, and the first protection release threshold TAL is referred to as the protection release threshold TAL.

In step S20, it is determined whether field weakening control is being performed.

If it is determined in step S20 that field weakening control is being performed, the process proceeds to step S21, where the motor temperature Tmgd is acquired. Note that the process of step S21 corresponds to the "acquisition unit."

In step S22, it is determined whether the control mode is the overheat protection mode out of the normal mode and the overheat protection mode.

If it is determined in step S22 that the control mode is normal mode, the process proceeds to step S23, where it is determined whether the motor temperature Tmgd has exceeded the protection start threshold TAH.

If it is determined in step S23 that the motor temperature Tmgd is equal to or lower than the protection start threshold TAH, the process proceeds to step S24, where the control mode is changed to normal mode.

On the other hand, if it is determined in step S23 that the motor temperature Tmgd has exceeded the protection start threshold TAH, the process proceeds to step S25, where the control mode is changed to the overheat protection mode. The process of step S25 is the same as that of step S16 in FIG. 4. The process of step S25 reduces the frequency fr of the carrier signal Sig, and also reduces the field weakening current.

After the processing of step S25, if it is determined in step S22 that the control mode is the overheat protection mode, the process proceeds to step S26. In step S26, it is determined whether the motor temperature Tmgd has become equal to or lower than the protection release threshold TAL. If it is determined in step S26 that the motor temperature Tmgd is higher than the protection release threshold TAL, the process proceeds to step S25. This causes the control mode to be changed to the overheat protection mode. On the other hand, if it is determined in step S26 that the motor temperature Tmgd has become equal to or lower than the protection release threshold TAL, the process proceeds to step S24. This causes the overheat protection mode to be released, and the control mode to be changed to the normal mode.

According to the present embodiment described above, it is possible to simplify the overheat protection control and prevent the rotating electrical machine 20 and the inverter 30 from becoming overheated.
<Modification of the second embodiment>
The allowable upper limit temperature of the rotating electric machine 20 may be higher than the allowable upper limit temperature of the inverter 30. In this case, the inverter temperature Tinvd may be used instead of the motor temperature Tmgd in the overheat protection control shown in Fig. 9. Also, in the overheat protection control shown in Fig. 9, TBH and TBL may be used as threshold values instead of TAH and TAL.

Third Embodiment
Hereinafter, the third embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, instead of the control mode being set to the overheat protection mode, a loss comparison process is performed.

Figure 10 shows the procedure for the overheat protection control of this embodiment. The overheat protection control shown in Figure 10 is repeatedly executed by the control device 37 at a predetermined control period, for example. Note that in Figure 10, the same processes as those shown in Figure 4 above are denoted by the same reference numerals for convenience.

If the determination in step S13 is positive, the process proceeds to step S30, where loss comparison processing is performed. The loss comparison processing is described below with reference to FIG. 11.

In step S40, the amount of reduction in the field-weakening current when the frequency fr of the carrier signal Sig is assumed to be reduced by a predetermined amount is calculated, and the amount of reduction in loss (hereinafter, loss reduction amount Wf) that occurs in the inverter 30 and the rotating electric machine 20 due to the reduction in the field-weakening current is calculated. The loss reduction amount Wf is mainly the amount of reduction in copper loss due to the reduction in the field-weakening current.

In step S41, assuming that the frequency fr of the carrier signal Sig is reduced by a predetermined amount, the increase in loss (hereinafter, loss increase Wh) that occurs in the inverter 30 and the rotating electric machine 20 due to the reduction in frequency fr is calculated. The loss increase Wh is mainly the increase in loss caused by the reduction in controllability of the phase current flowing through the stator winding 21 and the distortion of the phase current waveform due to the reduction in frequency fr.

In step S42, it is determined whether the loss reduction amount Wf exceeds the loss increase amount Wh. If the determination in step S42 is positive, the process proceeds to step S43, where the frequency fr of the carrier signal Sig is reduced by a predetermined amount. In addition, the absolute value of the d-axis command current Id* is reduced by the calculated reduction amount of the field weakening current.

On the other hand, if the result of step S42 is negative, the process proceeds to step S44, where the reduction in the frequency fr of the carrier signal Sig is stopped, and the reduction in the field weakening current is stopped. In other words, the frequency fr of the carrier signal Sig is maintained at the frequency fr of the carrier signal Sig set in the previous control cycle, and the field weakening current is maintained at the field weakening current set in the previous control cycle. This stops the reduction in the field weakening current and the reduction in the frequency fr of the carrier signal Sig.

In the loss comparison process, even if a positive judgment is made in step S42, if the frequency fr of the carrier signal Sig reaches the lower limit frequency fL, the reduction in the frequency fr of the carrier signal Sig may be stopped.

If the result of step S14 is affirmative, the process proceeds to step S31, where the loss comparison process shown in FIG. 11 is performed.

As described above, in this embodiment, for example, when it is determined that the motor temperature Tmgd exceeds the first protection start threshold TAH, the frequency fr of the carrier signal Sig begins to be reduced. As a result, the field weakening current begins to decrease, and the frequency fr of the carrier signal Sig begins to decrease. Whether the loss increase amount Wh has become equal to or greater than the loss reduction amount Wf is determined for each control cycle. In the control cycle in which it is determined that the loss increase amount Wh has become equal to or greater than the loss reduction amount Wf, the reduction in the frequency fr of the carrier signal Sig is stopped. This makes it possible to suppress the increase in losses occurring in the rotating electric machine 20 and the inverter 30 while preventing the rotating electric machine 20 and the inverter 30 from becoming overheated.

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

The temperatures of the rotating electric machine 20 and the inverter 30 used in the overheating protection control are not limited to values detected by temperature sensors, but may be values estimated by a temperature estimation unit provided in the control device 37.

- The semiconductor switches that make up the inverter are not limited to IGBTs, but may be, for example, N-channel MOSFETs with built-in body diodes. In this case, the high-potential terminal of the switch is the drain, and the low-potential terminal is the source.

- 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 motor serves as the flying power source for the aircraft, and if the moving body is a ship, the rotating electric motor serves as the navigation power source for the ship. In addition, the control system is not limited to a system mounted on a moving body, but may be a stationary system.

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...rotating electric machine, 30...inverter, 37...control device.

Claims (9)

A rotating electric machine (20) having a stator winding (21);
an inverter (30) electrically connected to the stator winding;
In an inverter control device (37) applied to a control system including:
a switch control unit that performs switching control of the inverter based on a comparison of the magnitude between the command voltage of the stator winding and a carrier signal;
an acquisition unit that acquires a temperature of at least one of the inverter and the rotating electric machine;
Equipped with
an inverter control device in which, when the switch control unit determines that the acquired temperatures (Tmgd, Tinvd) exceed temperature threshold values (TAH, TBH) while a field-weakening current is flowing through the stator winding, the switch control unit reduces a frequency of the carrier signal, and reduces the field -weakening current as the frequency of the carrier signal becomes lower . The inverter control device according to claim 1, wherein, when the switch control unit determines that the acquired temperature exceeds the temperature threshold, the higher the acquired temperature, the more the frequency of the carrier signal is reduced. The inverter control device according to claim 1 or 2 , wherein the switch control unit prevents the frequency of the carrier signal from falling below a lower limit frequency (fL). A rotating electric machine (20) having a stator winding (21);
an inverter (30) electrically connected to the stator winding;
In an inverter control device (37) applied to a control system including:
a switch control unit that performs switching control of the inverter based on a comparison of the magnitude between the command voltage of the stator winding and a carrier signal;
an acquisition unit that acquires a temperature of at least one of the inverter and the rotating electric machine;
Equipped with
The switch control unit is
In a case where the switching control is being performed while a field weakening current is flowing through the stator winding, when it is determined that the acquired temperatures (Tmgd, Tinvd) exceed temperature threshold values (TAH, TBH), the frequency of the carrier signal is started to be reduced and the field weakening current is started to be decreased;
An inverter control device that determines each time whether an increase (Wh) in loss generated in the inverter and the rotating electric machine due to a reduction in the frequency of the carrier signal has become equal to or greater than a decrease (Wf) in loss due to a reduction in the field-weakening current, and when it is determined that the increase has become equal to or greater than the decrease, stops the reduction in the frequency of the carrier signal and the reduction in the field-weakening current . the acquisition unit acquires a first temperature (Tmgd) that is a lower allowable upper limit temperature of the inverter or the rotating electric machine, and a second temperature (Tinvd) that is a higher allowable upper limit temperature of the inverter or the rotating electric machine,
the temperature thresholds are a first temperature threshold (TAH) and a second temperature threshold (TBH) higher than the first temperature threshold,
5. The inverter control device according to claim 1, wherein, when the switching control is being performed while a field-weakening current is flowing through the stator winding, when it is determined that either one of a condition that the acquired first temperature has exceeded the first temperature threshold value and a condition that the acquired second temperature has exceeded the second temperature threshold value is satisfied, the switch control unit reduces a frequency of the carrier signal and decreases the field-weakening current. A rotating electric machine (20) having a stator winding (21);
an inverter (30) electrically connected to the stator winding;
A computer (37a);
A program applied to a control system comprising:
The computer includes:
A process of executing switching control of the inverter based on a comparison of magnitude between the command voltage of the stator winding and a carrier signal;
acquiring a temperature of at least one of the inverter and the rotating electric machine;
a process of reducing a frequency of the carrier signal when it is determined that the acquired temperatures (Tmgd, Tinvd) exceed temperature threshold values (TAH, TBH) in a case where the switching control is being performed while a field weakening current is flowing through the stator winding, and reducing the field weakening current as the frequency of the carrier signal becomes lower ;
A program to execute. A rotating electric machine (20) having a stator winding (21);
an inverter (30) electrically connected to the stator winding;
A computer (37a);
A program applied to a control system comprising:
The computer includes:
A process of executing switching control of the inverter based on a comparison of magnitude between the command voltage of the stator winding and a carrier signal;
acquiring a temperature of at least one of the inverter and the rotating electric machine;
a process of starting to reduce a frequency of the carrier signal and starting to decrease the field weakening current when it is determined that the acquired temperatures (Tmgd, Tinvd) exceed temperature threshold values (TAH, TBH) in a case where the switching control is being performed while a field weakening current is flowing through the stator winding;
a process of determining whether an increase (Wh) in loss generated in the inverter and the rotating electric machine caused by reducing the frequency of the carrier signal is equal to or greater than a decrease (Wf) in the loss caused by reducing the field-weakening current, and stopping the reduction in the frequency of the carrier signal and the reduction in the field-weakening current when it is determined that the increase is equal to or greater than the decrease;
A program to execute. A rotating electric machine (20) having a stator winding (21);
an inverter (30) electrically connected to the stator winding;
An inverter control method applied to a control system including:
executing a switching control of the inverter based on a comparison of magnitude between the command voltage of the stator winding and a carrier signal;
acquiring a temperature of at least one of the inverter and the rotating electric machine;
a step of reducing a frequency of the carrier signal when it is determined that the acquired temperatures (Tmgd, Tinvd) exceed temperature threshold values (TAH, TBH) while a field-weakening current is flowing through the stator winding and reducing the field-weakening current as the frequency of the carrier signal decreases;
An inverter control method comprising: A rotating electric machine (20) having a stator winding (21);
an inverter (30) electrically connected to the stator winding;
An inverter control method applied to a control system including:
executing a switching control of the inverter based on a comparison of magnitude between the command voltage of the stator winding and a carrier signal;
acquiring a temperature of at least one of the inverter and the rotating electric machine;
a step of starting to reduce a frequency of the carrier signal and starting to decrease the field weakening current when it is determined that the acquired temperatures (Tmgd, Tinvd) exceed temperature threshold values (TAH, TBH) in a case where the switching control is being performed while a field weakening current is flowing through the stator winding;
determining whether an increase (Wh) in loss generated in the inverter and the rotating electric machine due to a reduction in the frequency of the carrier signal is equal to or greater than a decrease (Wf) in loss due to a reduction in the field-weakening current, and stopping the reduction in the frequency of the carrier signal and the reduction in the field-weakening current when it is determined that the increase is equal to or greater than the decrease;
An inverter control method comprising:

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