JP7639626B2 - Inverter control device and program - Google Patents

Description

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

Conventionally, as described in, for example, Patent Document 1, an inverter control device is known 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 amount of heat generated by the inverter and the rotating electric machine is greater 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 objective of the present invention is to provide an inverter control device and program that can prevent the inverter and the rotating electric machine from overheating while suppressing torque reduction or maintaining the torque of the rotating electric machine.

The present invention relates to a rotating electric machine having a stator winding,
an inverter electrically connected to the stator winding;
An inverter control device applied to a control system including:
a switch control unit that executes a sine wave PWM control, which is a switching control of the inverter that changes the phase voltage applied to the stator winding into a PWM voltage waveform;
an acquisition unit that acquires a temperature of at least one of the inverter and the rotating electric machine;
Equipped with
When the switch control unit determines that the acquired temperature exceeds a temperature threshold value while executing the sinusoidal PWM control while flowing a field-weakening current through the stator winding, it switches from the sinusoidal PWM control to overmodulation PWM control, which is the switching control that converts the phase voltage applied to the stator winding into a PWM voltage waveform having a higher modulation rate than the PWM waveform voltage by the sinusoidal PWM control, and reduces the field-weakening current.

In the present invention, when sine wave PWM 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 sine wave PWM control is switched to overmodulation PWM control. This increases the modulation rate of the PWM waveform voltage, and thus increases the voltage utilization rate of the inverter.

By increasing the voltage utilization rate, the rotating electric machine has more torque. Therefore, in the present invention, in addition to switching to overmodulation PWM control, the field weakening current is reduced to reduce the magnitude of the current vector flowing through the stator winding. The reduction in the field weakening current reduces the temperature of the inverter and the rotating electric machine. 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. FIG. 4 is a diagram showing changes in a command voltage and a carrier signal in sine wave PWM control. 5 is a diagram showing changes in a command voltage and a carrier signal in overmodulation PWM control. FIG. 4 is a flowchart showing a procedure for overheat protection control. FIG. 13 is a diagram showing a method for setting an increase rate. 5 is a time chart showing an example of a manner in which a field-weakening current is reduced; FIG. 11 is a diagram showing a method for setting an increase rate according to a modified example of the first embodiment. 10 is a flowchart showing a procedure of overheat protection control according to a second embodiment. 13 is a flowchart showing a procedure of overheat protection control according to a third embodiment. 4 is a flowchart showing a procedure of overmodulation processing.

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 has 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, programs for the processes shown in Figures 2 and 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, the power supply voltage Vdc detected by the voltage sensor 33, and the increase rate RTr 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 in which the command torque Trq*, the rotation speed Nm of the rotor 22, and "Vdc x RTr" are associated with 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 command current setting unit 40 sets the d-axis command current Id* such that the field weakening current becomes smaller as "Vdc x RTr" becomes higher. For example, when the sign of the field weakening current is negative, the command current setting unit 40 reduces the absolute value of the d-axis command current Id* as "Vdc x RTr" becomes higher.

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 limiter unit 46 calculates the voltage vector Vvtr to be applied to the stator winding 21 based on the d-axis and q-axis command voltages Vd and Vq. If the magnitude of the calculated voltage vector Vvtr is greater than the limit value "C x RTr", the limiter unit 46 sets the magnitude of the voltage vector Vvtr to the same value as the limit value "C x RTr" without changing the voltage phase δ of the voltage vector Vvtr. The limit value is the product of the reference value C and the increase rate RTr. The increase rate RTr is a value equal to or greater than 1, and is basically set to 1. Note that Vvtc shown in FIG. 2 indicates a voltage vector limited by the limit value "C x RTr" and the magnitude of which is set to the same value as the limit value.

In this embodiment, three-phase modulation is performed, so the reference value C is expressed by the following equation (eq1). In other words, the reference value C depends on the power supply voltage Vdc.

ちなみに、２相変調又は空間ベクトル変調（ＳＶＭ）が行われる場合、基準値Ｃは下式（ｅｑ２）にて表される。

Incidentally, when two-phase modulation or space vector modulation (SVM) is performed, the reference value C is expressed by the following equation (eq2).

リミッタ部４６は、電圧ベクトルＶｖｔｒの大きさが制限値「Ｃ×ＲＴｒ」以下の場合、ｄ，ｑ軸指令電圧算出部４４，４５により算出されたｄ，ｑ軸指令電圧Ｖｄ，Ｖｑをそのまま３相変換部４７に出力する。一方、リミッタ部４６は、電圧ベクトルＶｖｔｒの大きさが制限値「Ｃ×ＲＴｒ」よりも大きい場合、制限された電圧ベクトルＶｖｔｃをｄ，ｑ軸指令電圧Ｖｄ，Ｖｑに変換して３相変換部４７に出力する。

When the magnitude of the voltage vector Vvtr is equal to or smaller than the limit value "C×RTr", the limiter unit 46 outputs the d- and q-axis command voltages Vd and Vq calculated by the d- and q-axis command voltage calculation units 44 and 45 as they are to the three-phase conversion unit 47. On the other hand, when the magnitude of the voltage vector Vvtr is greater than the limit value "C×RTr", the limiter unit 46 converts the limited voltage vector Vvtc into d- and q-axis command voltages Vd and Vq and outputs them to the three-phase conversion unit 47.

The three-phase conversion unit 47 converts the d- and q-axis command voltages Vd, 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, Vq and electrical angle θe output from the limiter unit 46. In this embodiment, the U-, V- and W-phase command voltages VU*, VV*, and VW* have sinusoidal waveforms with phases shifted by 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, GUL for the upper and lower arm switches SWH, 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.

The above-mentioned sine wave PWM control is the switching control of the inverter 30 when the amplitude of the normalized command voltage is equal to or less than the amplitude of the carrier signal Sig.

In this embodiment, when a field-weakening current is flowing through the stator winding 21, the control device 37 executes overheat protection control to switch the sine wave PWM control to overmodulation PWM control while reducing the field-weakening current in order to prevent the inverter 30 and the rotating electric machine 20 from overheating. Overmodulation PWM control is a switching control in which the amplitude of the normalized command voltage becomes larger than the amplitude of the carrier signal Sig, as shown in FIG. 4. The PWM voltage waveform applied to the stator winding 21 by overmodulation PWM control has a voltage waveform with a higher modulation rate than the PWM waveform voltage applied to the stator winding 21 by sine wave PWM control.

Next, the overheat protection control executed by the control device 37 will be described with reference to FIG. 5. The control process shown in FIG. 5 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 current control mode is overmodulation PWM control or sinusoidal PWM control.

If it is determined in step S12 that the current control mode is sinusoidal PWM control, 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 setting 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, where the control mode is changed to sine wave PWM control.

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 switched from sine wave PWM control to overmodulation PWM control. In this embodiment, as shown in FIG. 6, the higher the motor temperature Tmgd, the greater the increase rate RTr (>1). When the increase rate RTr exceeds 1, the limit value "C×RTr" in the limiter unit 46 shown in FIG. 2 becomes large. As a result, the magnitudes of the d-axis and q-axis command voltages Vd and Vq output from the limiter unit 46 to the three-phase conversion unit 47 increase, and the amplitude of the normalized command voltage becomes larger than the amplitude of the carrier signal Sig. This causes the control mode to be switched from sine wave PWM control to overmodulation PWM control.

In addition, when the increase rate RTr exceeds 1, "Vdc x RTr" input to the command current setting unit 40 becomes larger. As a result, the field weakening current determined by the command current setting unit 40 becomes smaller. In other words, the higher the motor temperature Tmgd, the greater the degree of reduction in the field weakening current when overheat protection control is executed, compared to the field weakening current when overheat protection control is not executed.

Figure 7 shows an example of how the field weakening current is reduced. Figure 7(a) shows the progression of the motor temperature Tmgd, and Figure 7(b) shows the progression of the 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 field weakening current. In the example shown in Figure 7, the rate of increase of the motor temperature Tmgd gradually decreases as the field weakening current is reduced.

In step S16, if the motor temperature Tmgd is equal to or higher than the upper limit temperature TAK, the increase rate RTr is set to the upper limit rate RTlim as shown in FIG. 6. In other words, the modulation rate of the PWM waveform voltage by the overmodulation PWM control is prevented from exceeding the upper limit modulation rate. The increase rate RTr is limited to the upper limit rate RTlim in order to avoid a significant decrease in the controllability of the phase current flowing through the stator winding 21 while avoiding an increase in losses due to an increase in the harmonic components contained in the phase current.

Returning to the explanation of FIG. 5, after the processing of step S16 is completed, if it is determined in step S12 that the current control mode is overmodulation PWM control, 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 a value obtained by subtracting the first predetermined temperature ΔT1 from the first protection start threshold TAH. 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.

Incidentally, when the motor temperature Tmgd decreases, the increase rate RTr decreases. In this case, for example, as shown in FIG. 6, if the increase rate RTr is 1 at the time when the motor temperature Tmgd decreases and reaches the first protection release threshold TAL, the decrease in the increase rate RTr associated with the decrease in the motor temperature Tmgd can be freely determined in the hatched area in FIG. 6.

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, where the increase rate RTr is set to 1. This switches the control mode from overmodulation PWM control to sine wave PWM control, and the degree of decrease in the field weakening current becomes 0. 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 sine wave PWM control and overmodulation PWM control (so-called hunting).

When the current control mode is sinusoidal PWM control, if it is determined in step S14 that the inverter temperature Tinvd has exceeded the second protection start threshold TBH, the inverter 30 may be overheated, so the process proceeds to step S19. In step S19, the same process as that in step S16 is performed. In detail, as shown in FIG. 6, the higher the inverter temperature Tinvd, the more the increase rate RTr (>1) is increased. When the increase rate RTr exceeds 1, the limit value "C×RTr" in the limiter unit 46 shown in FIG. 2 becomes large. As a result, the magnitudes of the d-axis and q-axis command voltages Vd and Vq output from the limiter unit 46 to the three-phase conversion unit 47 increase, and the amplitude of the standardized command voltage becomes larger than the amplitude of the carrier signal Sig. This switches the control mode from sinusoidal PWM control to overmodulation PWM control.

In addition, when the increase rate RTr exceeds 1, "Vdc x RTr" input to the command current setting unit 40 becomes larger. As a result, the field weakening current becomes smaller. In other words, the higher the inverter temperature Tinvd, the greater the degree of reduction in the field weakening current when overheat protection control is executed compared to the field weakening current when overheat protection control is not executed.

In step S19, if the inverter temperature Tinvd is equal to or higher than the upper limit temperature TBK, the increase rate RTr is set to the upper limit rate RTlim, as shown in FIG. 6. In other words, the modulation rate of the PWM waveform voltage by the overmodulation PWM control is prevented from exceeding the upper limit modulation rate. 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.

Returning to the explanation of FIG. 5, after the processing of step S19, if it is determined in step S12 that the current control mode is overmodulation PWM control, 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.

Incidentally, when the inverter temperature Tinvd drops, the increase rate RTr is reduced. In this case, for example, as shown in FIG. 6, if the increase rate RTr is 1 at the time when the inverter temperature Tinvd drops to the second protection release threshold TBL, the decrease in the increase rate RTr associated with the decrease in the inverter temperature Tinvd can be freely determined in the hatched area in FIG. 6.

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, where the increase rate RTr is set to 1. This switches the control mode from overmodulation PWM control to sine wave PWM control, and the degree of decrease in the field weakening current becomes 0.

Incidentally, the processing in steps S12 to S18 corresponds to the "switch control unit."

As described above, in this embodiment, when sine wave PWM control is being performed while a field weakening current is flowing through the stator winding 21, the control device 37 performs overheat protection control when 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. In more detail, the control device 37 switches from sine wave PWM control to overmodulation PWM control. This increases the modulation rate of the PWM waveform voltage applied to the stator winding 21, and thus increases the voltage utilization rate of the inverter 30.

The control device 37 also reduces the field weakening current. Even when the field weakening current is reduced, the torque reduction that accompanies the reduction in the field weakening current can be suppressed by improving the voltage utilization rate, or the torque can be maintained at the same level. This makes it possible to prevent the inverter 30 and the rotating electric machine 20 from overheating while suppressing the torque reduction of the rotating electric machine 20 or maintaining the torque.

In addition, as the conditions for starting overheat protection, 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 increase rate RTr and the degree of decrease in the field weakening current 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 increase rate RTr and the degree of decrease in the field weakening current are set based on the motor temperature Tmgd, not on the inverter temperature Tinvd. This allows appropriate overheat protection to be performed for the inverter 30 and the rotating electric machine 20, which have different allowable upper limit temperatures.

While overmodulation PWM control can improve the voltage utilization rate, it also increases the noise and vibration of the rotating electric machine 20. For this reason, it is desirable to avoid it as much as possible during normal times when there is no risk of overheating. However, in this embodiment, overmodulation PWM control is executed 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 to continue running the vehicle 10 as much as possible while avoiding overheating abnormalities.

<Modification of the First Embodiment>
The control device 37 may set the upper limit ratio RTlim to a larger value as the electrical angular speed ωe of the rotating electric machine 20 increases.

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 first protection start threshold TAH should be 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 increase rate RTr using the method shown in FIG. 8 instead of the method shown in FIG. 6. 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 increases the increase rate RTr in a stepwise manner from 1 to the upper limit rate RTlim. 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 increase rate RTr is set to the upper limit rate RTlim, the control device 37 decreases the increase rate RTr in a stepwise manner from the upper limit rate RTlim to 1.

Next, regarding the overheat protection of the inverter 30, when the control device 37 determines that the inverter temperature Tinvd has exceeded the second protection start threshold TBH, it increases the increase rate RTr in a stepwise manner from 1 to the upper limit rate RTlim. On the other hand, when the control device 37 determines that the inverter temperature Tinvd has become equal to or lower than the second protection release threshold TBL in a case where the increase rate RTr is set to the upper limit rate RTlim, it decreases the increase rate RTr in a stepwise manner from the upper limit rate RTlim to 1.

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 control process 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 current control mode is overmodulation PWM control or sinusoidal PWM control.

If it is determined in step S22 that the current control mode is sine wave PWM control, 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 sine wave PWM control.

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 switched from sine wave PWM control to overmodulation PWM control. The process of step S25 is the same as step S16 in FIG. 5. The process of step S25 switches the control mode from sine wave PWM control to overmodulation PWM control, and also reduces the field weakening current.

After the processing of step S25, if it is determined in step S22 that the current control mode is overmodulation PWM control, 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. 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, where the increase rate RTr is set to 1. This switches the control mode from overmodulation PWM control to sine wave PWM control, and the degree of decrease in the field weakening current becomes 0. According to the present embodiment described above, it is possible to simplify the overheat protection control while preventing the rotating electric 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, the method of setting the increase rate RTr in the overheat protection control is changed.

Figure 10 shows the procedure for overheat protection control in this embodiment. The control process 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 5 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 overmodulation processing is performed. The overmodulation processing is described below with reference to FIG. 11.

In step S40, the amount of reduction in the field-weakening current that would occur if the increase rate RTr were increased 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 increase rate RTr has been increased 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 increase in the modulation rate is calculated. The loss increase Wh is mainly the increase in iron loss and harmonic copper loss due to the increase in the modulation rate.

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 increase rate RTr is increased by a predetermined amount. This increases the magnitude of the d-axis and q-axis command voltages Vd and Vq input from the limiter unit 46 to the three-phase conversion unit 47, and also reduces the field weakening current set in the command current setting unit 40.

On the other hand, if the result of step S42 is negative, the process proceeds to step S44, where the increase in the increase rate RTr is stopped. In other words, the increase rate RTr is maintained at the increase rate RTr set in the previous control cycle. This stops the decrease in the field weakening current and the increase in the modulation rate of the PWM waveform voltage by the overmodulation PWM control.

In the overmodulation process, even if a positive determination is made in step S42, if the increase rate RTr reaches the upper limit rate RTlim, the increase in the increase rate RTr may be stopped.

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

As described above, the control device 37 of this embodiment starts to increase the increase rate RTr when it determines that the motor temperature Tmgd has exceeded the first protection start threshold TAH, for example. This causes the field weakening current to start decreasing and the modulation rate to start increasing. The control device 37 determines whether the loss increase amount Wh has become equal to or greater than the loss reduction amount Wf for each control period. The control device 37 stops increasing the increase rate RTr in the control period in which it is determined that the loss increase amount Wh has become equal to or greater than the loss reduction amount Wf. 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 the detected values of the 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 (5)

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 executes a sine wave PWM control, which is a switching control of the inverter that changes the phase voltage applied to the stator winding into a PWM voltage waveform;
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
when it is determined that the acquired temperatures (Tmgd, Tinvd) exceed temperature threshold values (TAH, TBH) while the sine wave PWM control is being performed while a field weakening current is flowing through the stator winding, the control switches from the sine wave PWM control to overmodulation PWM control, which is the switching control that makes the phase voltage applied to the stator winding a PWM voltage waveform having a higher modulation rate than the PWM waveform voltage by the sine wave PWM control, starts to increase the modulation rate of the PWM waveform voltage by the overmodulation PWM control , and starts to decrease the field weakening current;
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 an increase in the modulation factor has become equal to or greater than a decrease (Wf) in loss due to a decrease in the field-weakening current, and stops the decrease in the field-weakening current and the increase in the modulation factor when it is determined that the increase has become equal to or greater than the decrease . 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 executes a sine wave PWM control, which is a switching control of the inverter that changes the phase voltage applied to the stator winding into a PWM voltage waveform;
an acquisition unit that acquires a first temperature (Tmgd) that is a lower allowable upper limit temperature of the inverter and the rotating electric machine, and a second temperature (Tinvd) that is a higher allowable upper limit temperature of the inverter and the rotating electric machine;
Equipped with
When the switch control unit determines that either of a condition that the acquired first temperature exceeds a first temperature threshold (TAH) and a condition that the acquired second temperature exceeds a second temperature threshold (TBH) higher than the first temperature threshold is satisfied while the sinusoidal PWM control is being executed while a field-weakening current is flowing through the stator winding, the switch control unit reduces the field-weakening current and switches from the sinusoidal PWM control to overmodulation PWM control, which is the switching control that makes the phase voltage applied to the stator winding a PWM voltage waveform having a higher modulation rate than the PWM waveform voltage by the sinusoidal PWM control . 3 . The inverter control device according to claim 1 , wherein the switch control unit prevents a modulation rate of the PWM waveform voltage by the overmodulation PWM control from exceeding an upper limit modulation rate. 4 . 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 a sinusoidal PWM control, which is a switching control of the inverter, for making the phase voltage applied to the stator winding into a PWM voltage waveform;
acquiring a temperature of at least one of the inverter and the rotating electric machine;
a process of switching from the sine wave PWM control to overmodulation PWM control, which is the switching control for making a phase voltage applied to the stator winding into a PWM voltage waveform having a higher modulation rate than the PWM waveform voltage by the sine wave PWM control, while flowing a field weakening current through the stator winding and starting to increase the modulation rate of the PWM waveform voltage by the overmodulation PWM control and start to decrease the field weakening current, when it is determined that the acquired temperatures (Tmgd, Tinvd) exceed temperature threshold values (TAH, TBH) while the sine wave PWM control is being performed;
a process of determining whether an increase (Wh) in loss generated in the inverter and the rotating electric machine due to an increase in the modulation factor is equal to or greater than a decrease (Wf) in the loss due to a decrease in the field-weakening current, and stopping the decrease in the field-weakening current and the increase in the modulation factor 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;
A computer (37a);
A program applied to a control system comprising:
The computer includes:
A process of executing a sinusoidal PWM control, which is a switching control of the inverter, for making the phase voltage applied to the stator winding into a PWM voltage waveform;
A process of acquiring a first temperature (Tmgd) which is a lower allowable upper limit temperature of the inverter and the rotating electric machine, and a second temperature (Tinvd) which is a higher allowable upper limit temperature of the inverter and the rotating electric machine;
a process of reducing the field weakening current and switching from the sine wave PWM control to overmodulation PWM control, which is the switching control that changes the phase voltage applied to the stator winding to a PWM voltage waveform having a higher modulation rate than the PWM waveform voltage by the sine wave PWM control, when it is determined that either one of the conditions that the acquired first temperature exceeds a first temperature threshold (TAH) and that the acquired second temperature exceeds a second temperature threshold (TBH) higher than the first temperature threshold is satisfied while the sine wave PWM control is being executed while a field weakening current is flowing through the stator winding;
A program to execute.

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