JP7354962B2 - Inverter control device and program - Google Patents

Description

The present invention relates to an inverter control device and a program that are applied to a system including a multiphase rotating electrical machine and an inverter electrically connected to armature windings forming the rotating electrical machine.

This type of control device performs switching control of switches of each phase that constitute an inverter in order to control the drive of a rotating electric machine by passing a current through an armature winding. Here, a surge voltage is generated as the drive state of the switch is changed.

As a control device for reducing surge voltage, Patent Document 1 discloses a device that detects a current value flowing through an armature winding and changes a switching speed in switching control based on the detected current value. There is. Specifically, the control device reduces the switching speed for three phases when the detected current value is small. This suppresses an increase in switching loss of the inverter while reducing the recovery surge voltage that occurs when the switch is turned on.

JP2015-65742A

Although the control device described in Patent Document 1 reduces the surge voltage, it reduces the switching speed of all three phases, resulting in a large increase in switching loss. In addition, the control device described in Patent Document 1 requires processing to change the switching speed based on the detected value of the current flowing through the armature winding, which complicates the configuration of the control device and increases the cost of the control device. There are growing concerns. In addition, when it is necessary to adjust the switching speed based on the detected value of the current flowing through the armature winding, if the processing capacity of the control device is insufficient, the controllability regarding the drive of the rotating electrical machine will deteriorate. There are also concerns.

A main object of the present invention is to provide an inverter control device and program that can reduce surge voltages generated when switching drive states of switches while suppressing an increase in switching loss while having a simple configuration. .

The present invention provides a multiphase rotating electric machine,
An inverter control device applied to a system including an inverter electrically connected to an armature winding that constitutes the rotating electric machine,
a control unit that performs switching control of switches of each phase forming the inverter in order to perform drive control of the rotating electric machine;
A reduction unit that performs a speed reduction process to reduce the switching speed in the switching control of some of the phases from the switching speed in the switching control of the remaining phases,
The reduction unit sequentially switches the phase whose switching speed is to be reduced among the phases at regular intervals.

In the present invention, switching control of the switches of each phase is performed in order to perform drive control of the rotating electric machine. Here, in order to reduce the surge voltage, it is conceivable to reduce the switching speed in the switching control each time the drive state of the switch of each phase is changed. However, in this case, switching loss will increase significantly.

Therefore, in the present invention, the switching speed in the switching control of some of the phases is made lower than the switching speed in the switching control of the remaining phases. Thereby, surge voltage can be reduced while suppressing an increase in switching loss. Furthermore, in the present invention, among the phases, the phase whose switching speed is reduced is sequentially switched every prescribed period. Therefore, there is no need to use the detected value of the current flowing through the armature winding to change the switching speed, and the configuration can be simplified.

According to the present invention described above, although the configuration is simple, surge voltage can be reduced while suppressing an increase in switching loss.

FIG. 1 is an overall configuration diagram of a control system according to a first embodiment. FIG. 2 is a block diagram showing processing of a microcomputer. A diagram showing a drive circuit. Flowchart showing the procedure of speed reduction processing. FIG. 6 is a diagram illustrating a process of sequentially switching phases that reduce switching speed. FIG. 3 is a diagram showing that two-phase surge voltages are superimposed within the rotating electrical machine. 7 is a flowchart showing the procedure of speed reduction processing according to the second embodiment. FIG. 7 is a block diagram showing processing of a microcomputer according to a third embodiment. The figure which shows an example of a pulse pattern. FIG. 3 is a diagram showing a method of generating a drive signal based on a pulse pattern.

<First embodiment>
DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a control device according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the control system includes a rotating electrical machine 10 and an inverter 20. In this embodiment, the rotating electrical machine 10 is a brushless synchronous machine, for example, a permanent magnet synchronous machine. The rotating electrical machine 10 includes U, V, and W phase windings 11U, 11V, and 11W, which are armature windings.

The rotating electric machine 10 is connected to a battery 30 as a DC power source via an inverter 20. The inverter 20 includes a series connection body of upper arm switches SUH, SVH, SWH and lower arm switches SUL, SVL, SWL. The connection point of the U-phase upper and lower arm switches SUH and SUL is connected to the U-phase terminal 21U of the inverter 20, the U-phase conductive member 22U, and the U-phase terminal 12U of the rotating electric machine 10, and the One end is connected. The connection point of the V-phase upper and lower arm switches SVH and SVL is connected to the V-phase winding 11V via the V-phase terminal 21V of the inverter 20, the V-phase conductive member 22V, and the V-phase terminal 12V of the rotating electric machine 10. One end is connected. The connection point of the W-phase upper and lower arm switches SWH, SWL is connected to the W-phase terminal 21W of the inverter 20, the W-phase conductive member 22W, and the W-phase terminal 12W of the rotating electric machine 10, and the W-phase winding 11W is connected to the connection point of the W-phase upper and lower arm switches SWH, SWL. One end is connected. The second ends of the U, V, and W phase windings 11U, 11V, and 11W are connected at the neutral point. In this embodiment, the U, V, and W phase windings 11U, 11V, and 11W are shifted from each other by 120 degrees in electrical angle. Note that the conductive members 22U, 22V, and 22W of each phase are, for example, cables or bus bars.

In this embodiment, voltage-controlled semiconductor switching elements are used as each of the switches SUH, SUL, SVH, SVL, SWH, and SWL, and more specifically, N-channel MOSFETs are used. Each switch SUH, SUL, SVH, SVL, SWH, SWL has a built-in body diode.

The inverter 20 is equipped with a capacitor 23 on its input side for smoothing the input voltage of the inverter 20. A positive terminal of a battery 30 is connected to a high potential terminal of the capacitor 23, and a negative terminal of the battery 30 is connected to a low potential terminal of the capacitor 23. The high potential side terminal of the capacitor 23 is connected to the drain, which is the high potential side terminal of the upper arm switches SUH to SWH. The sources, which are the low potential side terminals of the lower arm switches SUL to SWL, are connected to the low potential side terminal of the capacitor 23. Note that the capacitor 23 may be provided outside the inverter 20.

The control system includes a voltage sensor 40, a current sensor 41, a rotation angle sensor 42, a temperature sensor 43, and an air pressure sensor 44. Voltage sensor 40 detects the power supply voltage, which is the terminal voltage of capacitor 23 . The current sensor 41 detects at least two phase currents among the phase currents flowing through the rotating electrical machine 10 . The rotation angle sensor 42 is composed of, for example, a resolver or a Hall element, and detects the electrical angle of a rotor that constitutes the rotating electric machine 10.

Temperature sensor 43 detects the temperatures of rotating electrical machine 10 and inverter 20 . The temperature of the rotating electric machine 10 is, for example, the temperature of the windings 11U to 11W. Further, the temperature of the inverter 20 is, for example, the temperature of the upper and lower arm switches.

The atmospheric pressure sensor 44 detects the atmospheric pressure in the installation environment of the rotating electric machine 10 and the inverter 20. The detected values of each sensor 40 to 44 are input to a microcomputer 50 included in the control system.

The microcomputer 50 functions as a "control device" and performs switching control of the switches SUH to SWL constituting the inverter 20 in order to feedback control the control amount of the rotating electric machine 10 to a command value. In this embodiment, the controlled amount is torque. The microcomputer 50 sends drive signals corresponding to the upper and lower arm switches to drive signals provided separately for the upper and lower arm switches in order to alternately turn on the upper and lower arm switches with a dead time DT in between. Output to circuit Dr. The drive signal takes either an on command or an off command.

Next, torque control of the rotating electrical machine 10 executed by the microcomputer 50 will be described using FIG. 2. In this embodiment, current feedback control is performed as torque control.

The two-phase converter 51 converts U in the three-phase fixed coordinate system based on the phase current detected by the current sensor 41 (hereinafter referred to as phase current detection value) and the electrical angle θe detected by the rotation angle sensor 42. The V and W phase currents are converted into a d-axis current Idr and a q-axis current Iqr in a two-phase rotating coordinate system (dq coordinate system).

The command current setting unit 52 sets d- and q-axis command currents Id* and Iq* based on the torque command value Trq*. The d and q-axis command currents Id* and Iq* may be calculated by, for example, minimum current maximum torque control (MTPA).

The d-axis deviation calculation unit 53 calculates the d-axis current deviation ΔId as a value obtained by subtracting the d-axis current Idr from the d-axis command current Id*. The q-axis deviation calculation unit 54 calculates the q-axis current deviation ΔIq as a value obtained by subtracting the q-axis current Iqr from the q-axis command current Iq*.

The d-axis command voltage calculation unit 55 calculates the d-axis command voltage Vd* as a manipulated variable for feedback-controlling the d-axis current Idr to the d-axis command current Id* based on the d-axis current deviation ΔId. The q-axis command voltage calculation unit 56 calculates the q-axis command voltage Vq* as a manipulated variable for feedback-controlling the q-axis current Iqr to the q-axis command current Iq* based on the q-axis current deviation ΔIq. Note that the feedback control used in the d-axis command voltage calculation section 55 and the q-axis command voltage calculation section 56 may be proportional-integral control, for example.

The three-phase conversion unit 57 converts the d- and q-axis command voltages Vd* and Vq* in the two-phase rotating coordinate system into the three-phase fixed coordinate system based on the d- and q-axis command voltages Vd* and Vq* and the electrical angle θe. Convert to U, V, W phase command voltages VU*, VV*, VW* at. In this embodiment, the U, V, and W phase command voltages VU*, VV*, and VW* have sinusoidal waveforms whose phases are shifted by 120 degrees in electrical angle.

The signal generation unit 58 generates each drive signal GUH, based on the U, V, W phase command voltages VU*, VV*, VW* and the power supply voltage detected by the voltage sensor 40 (hereinafter referred to as power supply voltage detection value Vdc). Generate GVH, GWH, GUL, GVL, and GWL. Specifically, the signal generation unit 58 generates the U, V, W phase normalization command by dividing the U, V, W phase command voltages VU*, VV*, VW* by 1/2 of the power supply voltage detection value Vdc. Calculate voltages VUS, VVS, and VWS. The signal generation unit 58 generates U-phase upper and lower arm drive signals by PWM control based on magnitude comparison between the U, V, and W-phase normalized command voltages VUS, VVS, and VWS and a carrier signal Sc common to these command voltages. It generates GUH, GUL, V-phase upper and lower arm drive signals GVH, GVL, and W-phase upper and lower arm drive signals GWH, GWL. In this embodiment, the carrier signal Sc is a triangular wave signal with equal rising speed and falling speed. The signal generation unit 58 outputs the generated U-phase upper and lower arm drive signals GUH and GUL to the drive circuit Dr of the U-phase upper and lower arm switches SUH and SUL, and outputs the generated V-phase upper and lower arm drive signals GVH and Output GVL to the drive circuit Dr of the V-phase upper and lower arm switches SVH and SVL, and output the generated W-phase upper and lower arm drive signals GWH and GWL to the drive circuit Dr of the W-phase upper and lower arm switches SWH and SWL. do. Note that in this embodiment, the control cycle of the microcomputer 50 is sufficiently shorter than the cycle of the carrier signal Sc. In addition, in this embodiment, a two-phase conversion section 51, a command current setting section 52, d- and q-axis deviation calculation sections 53 and 54, d and q-axis command voltage calculation sections 55 and 56, a three-phase conversion section 57, and a signal generation section The section 58 corresponds to a "control section".

In this embodiment, the process shown in FIG. 2 is executed, for example, when the operating point of the rotating electrical machine 10 is included in the sine wave PWM control region or the overmodulation control region. Sine wave PWM control is used to make each phase voltage applied to the armature winding into a PWM voltage waveform when the peak value of each phase voltage applied to the armature winding is equal to or lower than the terminal voltage of the battery 30. This is switching control for the upper and lower arm switches. Sine wave PWM control includes three-phase modulation or two-phase modulation. In addition, overmodulation control is such that when the peak value of each phase voltage applied to the armature winding exceeds the terminal voltage of the battery 30, each phase voltage applied to the armature winding is controlled by sine wave PWM control. This is switching control of the upper and lower arm switches to create a PWM voltage waveform with a higher modulation rate than the PWM voltage waveform.

The microcomputer 50 includes a speed calculation section 59 and a speed command section 70. The speed calculation unit 59 calculates the electrical angular frequency ωe of the rotating electrical machine 10 based on the electrical angle θe.

The speed command unit 70 includes the electrical angular frequency ωe, the torque command value Trq*, the atmospheric pressure detected by the atmospheric pressure sensor 44 (hereinafter referred to as the detected atmospheric pressure value Pr), and the temperature detected by the temperature sensor 43 (hereinafter referred to as the temperature detected value). value TDr) is input. The speed command unit 70 outputs a U-phase speed command SPU to the U-phase upper and lower arm drive circuit Dr, outputs a V-phase speed command SPV to the V-phase upper and lower arm drive circuit Dr, A W-phase speed command SPW is output to the drive circuit Dr of the W-phase upper and lower arms.

Next, the drive circuit Dr will be explained using FIG. 3. The drive circuits Dr for the upper and lower arms of this embodiment basically have the same configuration. For convenience, in FIG. 3, the switches constituting the inverter 20 are indicated by SW, the drive signal input from the signal generation section 58 to the drive circuit Dr is indicated by GIN, and the drive signal input from the speed command section 70 to the drive circuit Dr is indicated by GIN. The speed command is indicated by SV.

The drive circuit Dr includes a constant voltage power supply 60, a charging switch 61, and a charging resistor 62. A gate of a switch SW is connected to the constant voltage power supply 60 via a charging switch 61 and a charging resistor 62. The output voltage (for example, 15V) of the constant voltage power supply 60 becomes the gate power supply voltage supplied to the gate of the switch SW.

The drive circuit Dr includes a first discharge resistor 63A, a first discharge switch 64A, a second discharge resistor 63B, and a second discharge switch 64B. The source of the switch SW as a ground portion is connected to the gate of the switch SW via the first discharge resistor 63A and the first discharge switch 64A. Furthermore, the source of the switch SW is connected to the gate of the switch SW via the second discharge resistor 63B and the second discharge switch 64B. The resistance value RA of the first discharge resistor 63A is larger than the resistance value RB of the second discharge resistor 63B.

The drive circuit Dr includes a drive section 65. The drive section 65 acquires the drive signal GIN output from the signal generation section 58. The drive unit 65 performs charging processing when the acquired drive signal GIN is an ON command. The charging process is a process of turning on the charging switch 61 and turning off the first discharge switch 64A and the second discharge switch 64B. According to the charging process, the gate voltage of the switch SW becomes equal to or higher than the threshold voltage Vth, and the switch SW is turned on.

The drive unit 65 performs a discharge process when the acquired drive signal GIN is an off command. In this embodiment, the discharge treatment is either a low-speed discharge treatment or a high-speed discharge treatment. The drive unit 65 performs a low-speed discharge process when the acquired speed command SV is a low-speed switching command. The low-speed discharge process is a process in which the charging switch 61 and the second discharge switch 64B are turned off, and the first discharge switch 64A is turned on. According to the slow discharge process, the gate voltage of the switch SW becomes less than the threshold voltage Vth, and the switch SW is turned off.

The drive unit 65 performs a high-speed discharge process when the acquired speed command SV is a high-speed switching command. The high-speed discharge process is a process in which the charging switch 61 and the first discharge switch 64A are turned off, and the second discharge switch 64B is turned on. According to the high-speed discharge process, the discharge rate of the gate charge of the switch SW is higher than that of the low-speed discharge process, and the switching speed when switching the switch SW to the OFF state is higher than that of the low-speed discharge process.

The speed command unit 70 performs a speed reduction process of outputting speed commands for some of the three phases as low-speed switching commands and outputting speed commands for the remaining phases as high-speed switching commands. This process is a process for suppressing an increase in the switching loss of the inverter 20 and reducing the surge voltage that occurs when the switch SW is turned off.

In other words, due to resonance and reflection caused by the inductance and capacitance of the inverter 20, each phase winding 11U to 11W, and each phase conductive member 22U to 22W, a surge voltage is generated as the drive state of the switch SW is changed, and the rotating electric machine 10 as an overvoltage. In particular, the surge voltage that occurs when the switch SW is switched to the off state tends to be larger than the recovery surge voltage that occurs when the switch SW is switched to the on state. Furthermore, when the driving states of the two phases are continuously switched, surge voltages generated as the driving states of the two phases are switched are superimposed. The superimposed surge voltage has a large voltage value. Therefore, if a surge voltage occurs between adjacent windings in the rotating electrical machine 10 or between the windings and the ground, partial discharge may occur between them, which may lead to deterioration of the rotating electrical machine 10.

Here, in order to reduce the surge voltage, it is also possible to reduce the switching speed of the switch SW every time the drive state is changed. However, in this case, switching loss will increase significantly. Therefore, in this embodiment, the speed command unit 70 performs the speed reduction process described above. This reduces the surge voltage that occurs when the switch SW is turned off while suppressing an increase in switching loss.

Next, the procedure of the speed reduction process executed by the speed command section 70 will be explained using FIG. 4. This process is repeatedly executed at a predetermined control cycle.

In step S10, it is determined whether all of the first to sixth conditions are satisfied. The first condition is that the torque command value Trq* (corresponding to the "current parameter") is greater than the torque threshold value Trqth. The second condition is that the electrical angular frequency ωe is higher than the high-speed threshold ωHth. The first and second conditions are conditions for determining whether the situation is such that the surge voltage generated when the switch SW is switched to the off state increases.

The third condition is that the electrical angular frequency ωe is lower than the low speed threshold ωLth (<ωHth). In this embodiment, the low speed threshold value ωLth is set to a value that allows it to be determined that the rotation of the rotor constituting the rotating electric machine 10 has stopped. Despite the torque control of the rotating electric machine 10 being performed, a situation where the rotation of the rotor is stopped or on the verge of stopping due to motor lock etc. is a situation where a large current flows through the armature winding. . The third condition is also a condition for determining whether the situation is such that the surge voltage generated as the switch SW is switched to the off state increases.

The fourth condition is that the detected atmospheric pressure value Pr is lower than the atmospheric pressure threshold Pth. Note that the atmospheric pressure threshold Pth may be set, for example, to a value less than 1 atmosphere (eg, 0.6 to 0.7 atmosphere). The fifth condition is that the detected temperature value TDr is higher than the high temperature side threshold value THth. The temperature detection value TDr used in the fifth condition is the temperature detection value TDr of either the rotating electric machine 10 or the inverter 20. The fourth and fifth conditions are conditions for determining whether or not the dielectric strength between the armature windings forming the rotating electric machine 10 is decreasing.

The sixth condition is that the temperature detection value TDr is lower than the low temperature side threshold value TLth (<THth). The low temperature side threshold TLth is set to a value that allows it to be determined that the environment in which the control system is placed is a low temperature environment. The temperature detection value TDr used in the sixth condition is the temperature detection value TDr of the inverter 20. The sixth condition is a condition for determining whether the situation is such that the surge voltage generated due to switching of the switch SW to the OFF state is increasing.

If it is determined in step S10 that at least one of the first to sixth conditions is not satisfied, it is determined that the execution condition for the speed reduction process is not satisfied, and the process proceeds to step S11. In step S11, the U, V, and W phase speed commands SPU, SPV, and SPW are converted into high-speed switching commands and output.

On the other hand, if it is determined in step S10 that all of the first to sixth conditions are satisfied, it is determined that the conditions for executing the speed reduction process are satisfied, and the process proceeds to step S12. In step S12, the speed commands for any two of the three phases are output as low-speed switching commands, and the speed commands for the remaining one phase are output as high-speed switching commands. In addition, in this embodiment, the process of step S12 corresponds to a "lowering part".

The process of step S12 will be explained using FIG. 5. In FIG. 5, H indicates a high-speed switching command, and L indicates a low-speed switching command. TA in FIG. 5 indicates a predetermined period. Although the predetermined period TA appears repeatedly, only one predetermined period TA is shown in FIG. In this embodiment, a period obtained by equally dividing the predetermined period TA by the number of phases "3" is set as the specified period TB. For example, the prescribed period TB is set to a predetermined fixed value. The speed command unit 70 sequentially switches the phase to be used as the low-speed switching command among the three phases every specified period TB so that the low-speed switching command appears twice in each phase in each predetermined period TA. Specifically, the speed command unit 70 includes a counting unit (specifically, a timer) that counts the elapsed time since the phase for the low-speed switching command is switched, and the counted elapsed time reaches the specified period TB. Each time, the phase to be used as the low-speed switching command is switched among the three phases.

Switching losses based on low-speed switching commands are larger than switching losses based on high-speed switching commands. Further, switching control based on a low-speed switching command and switching control based on a high-speed switching command have different degrees of distortion in the phase current waveform, which affects torque controllability. For this reason, according to a configuration in which the phases that receive the low-speed switching command are sequentially switched, it is possible to equalize the degree of distortion of the waveform of each phase current as much as possible while preventing heat generation from being concentrated in the switch SW of a specific phase among the three phases. This can prevent deterioration in torque controllability.

Incidentally, the specified period TB is, for example, one period of the carrier signal Sc (that is, one switching period of the switch SW), one period of the normalized command voltages VUS, VVS, VWS, one period of the phase voltage, and one period of the line voltage. It is sufficient that the period is set to a period shorter than one period of the phase current. Thereby, for example, it is possible to suppress noise in a new frequency band that may occur due to phase switching that reduces the switching speed.

The speed reduction process can reduce the surge voltage in which two phases are superimposed. In FIG. 6, voltages between the drain and source of the switch SW in two phases are indicated by VA and VB, and surge voltages generated within the rotating electric machine 10 due to VA and VB are indicated by VC and VD. Further, the surge voltage in which VC and VD are superimposed is indicated by VE. FIG. 8(a) shows the voltage transition in a comparative example in which the three-phase speed command is the high-speed switching command, and FIG. 8(b) shows the voltage transition in the present embodiment. In the example shown in FIG. 8(b), the switching speed of the phase corresponding to VB is reduced. As a result, the peak value of the superimposed surge voltage of this embodiment is reduced by ΔVS compared to the peak value of the superimposed surge voltage of the comparative example.

According to this embodiment described in detail above, the following effects can be obtained.

Among the three phases, speed commands for some of the phases are set as low-speed switching commands, and speed commands for the remaining phases are set as high-speed switching commands. Thereby, it is possible to reduce the superimposed surge voltage while suppressing an increase in switching loss. Further, among the three phases, the phase designated as a low-speed switching command is sequentially switched every prescribed period TB. Therefore, there is no need to use the detected value of the current flowing through the armature winding to change the switching speed, and the configuration of the microcomputer 50 and the like can be simplified. According to the present embodiment described above, although the configuration is simple, it is possible to reduce the superimposed surge voltage while suppressing an increase in switching loss. Thereby, the cost of the microcomputer 50 can be reduced.

Among the three phases, two phases are designated as low-speed switching commands. Therefore, the effect of reducing superimposed surge voltage can be enhanced. Furthermore, since the switching speed is reduced when switching to the off state where surge voltage tends to increase, the effect of reducing superimposed surge voltage can be further enhanced.

A period obtained by equally dividing the predetermined period TA by the number of phases "3" is set as the specified period TB. Then, the phase to be used as the low-speed switching command among the three phases is sequentially switched every prescribed period TB so that the low-speed switching command appears twice in each phase in each predetermined period TA. Thereby, it is possible to prevent heat generation from being biased toward the switch SW of a specific phase among the three phases, and to equalize the degree of distortion of the waveform of each phase current as much as possible, thereby preventing a decrease in torque controllability.

When it is determined that the electrical angular frequency ωe is higher than the high-speed side threshold value ωHth, the speed reduction process is performed. A situation where the electrical angular frequency ωe is higher than the high-speed side threshold value ωHth is a situation where the output of the rotating electric machine 10 becomes large, and therefore the surge voltage tends to become large. According to the configuration in which the speed reduction process is performed only in situations where surge voltage is likely to increase, it is possible to suppress increase in switching loss while suppressing surge voltage.

When it is determined that the electrical angular frequency ωe is lower than the low speed threshold ωLth, the speed reduction process is performed. In a situation where the electrical angular frequency ωe is lower than the low-speed threshold ωLth, there is a high possibility that the current flowing through the rotating electrical machine 10 is increasing, and there is a high possibility that the surge voltage is increasing. According to the configuration in which the speed reduction process is performed only in situations where surge voltage is likely to increase, it is possible to suppress increase in switching loss while suppressing surge voltage.

When it is determined that the torque command value Trq* is larger than the torque threshold value Trqth, the speed reduction process is performed. A situation in which the torque command value Trq* is larger than the torque threshold value Trqth is a situation in which the current flowing through the inverter 20 and the rotating electric machine 10 becomes large, so that the surge voltage tends to become large. According to the configuration in which the speed reduction process is performed only in situations where surge voltage is likely to increase, it is possible to suppress increase in switching loss while suppressing surge voltage.

When it is determined that the detected temperature value TDr is higher than the high temperature side threshold value THth, the speed reduction process is performed. A situation where the temperature detection value TDr is higher than the high temperature side threshold value THth is a situation where the dielectric strength of the rotating electrical machine 10 becomes low. Since the speed reduction process is performed only in such a situation, it is possible to suppress an increase in switching loss while suppressing a surge voltage.

When it is determined that the temperature detection value TDr is lower than the low temperature side threshold value TLth, the speed reduction process is performed. In a situation where the temperature detection value TDr is lower than the low temperature side threshold value TLth, the surge voltage tends to increase. Since the speed reduction process is performed only in such a situation, it is possible to suppress an increase in switching loss while suppressing a surge voltage.

When it is determined that the detected atmospheric pressure value Pr is lower than the atmospheric pressure threshold Pth, the speed reduction process is performed. A situation in which the detected atmospheric pressure value Pr is lower than the atmospheric pressure threshold value Pth is a situation in which the dielectric strength of the rotating electric machine 10 becomes low. Since the speed reduction process is performed only in such a situation, it is possible to suppress an increase in switching loss while suppressing a surge voltage.

<Modified example of the first embodiment>
- In step S12 of FIG. 4, the speed commands for each phase may be sequentially switched every prescribed period TB so that each phase is given a low-speed switching command once in a predetermined period TA. In this case, in each specified period TB, speed commands for two of the three phases are set as high-speed switching commands, and speed commands for the remaining one phase are set as low-speed switching commands.

- The predetermined period TA may not be equally divided by the number of phases, and the periods in which the predetermined period TA is divided by the number of phases may be different from each other.

- The driving circuit Dr may be able to change the switching speed when switching the switch SW to the OFF state not in two steps but in three or more steps, or in a continuous manner. In this case, in step S12, in each specified period TB, the speed commands of the remaining two phases are set to each other on the condition that the speed command of any one of the three phases is set to the lowest switching speed. Different switching speeds may be commanded. For example, in the case of a drive circuit Dr whose switching speed can be changed in three stages, in each specified period TB, the speed command for one of the three phases is set to a low switching speed, and the speed commands for the remaining two phases are set to a low switching speed. It may also be a high-speed switching command.

- In the second and third conditions of step S10 in FIG. 4, the mechanical angular frequency or rotational speed of the rotating electric machine 10 may be used instead of the electrical angular frequency ωe.

- In step S10, all of the first to sixth conditions may not be used, and at least one condition among the first to sixth conditions may be used. Here, if some of the first to sixth conditions and multiple conditions are used, for example, the second and third conditions should not be combined by logical product (AND), so that there is a contradiction in the processing. The plurality of conditions may be appropriately combined by logical product or logical sum (OR) on the condition that the condition does not occur.

- In step S10, the first condition may be replaced with a condition that the magnitude of the current vector (corresponding to the "current parameter") is larger than a predetermined threshold value. Here, the magnitude Ir of the current vector is a value correlated with the torque command value Trq, and may be calculated by, for example, the following formula (eq1).

また、第１条件において用いられる値は、指令値に限らず、検出値であってもよい。例えば、第１条件を、相電流検出値に基づいて算出した相電流の実効値（「電流パラメータ」に相当）が所定実効値よりも大きいとの条件、又は相電流検出値に基づいて算出した相電流の振幅（「電流パラメータ」に相当）が所定振幅よりも大きいとの条件に置き換えてもよい。

Further, the value used in the first condition is not limited to the command value, but may be a detected value. For example, the first condition is a condition that the effective value of the phase current (corresponding to a "current parameter") calculated based on the detected phase current value is larger than a predetermined effective value, or the first condition is calculated based on the detected phase current value. The condition may be replaced by a condition that the amplitude of the phase current (corresponding to a "current parameter") is larger than a predetermined amplitude.

<Second embodiment>
The second embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the method of setting the prescribed period TB has been changed.

FIG. 7 shows the procedure of the speed reduction process executed by the speed command unit 70. This process is repeatedly executed at a predetermined control cycle. Note that in FIG. 7, the same processes as those shown in FIG. 4 are given the same reference numerals for convenience.

If an affirmative determination is made in step S10, the process advances to step S13. In step S13, the lower the electrical angular frequency ωe or the larger the torque command value Trq*, the shorter the specified period TB is set. For example, when the cycle of the carrier signal Sc does not change, the shorter the prescribed period TB, the fewer carrier signals Sc included in the prescribed period TB. After completing the process in step S13, the process advances to step S12.

By setting the specified period TB to be shorter as the electrical angular frequency ωe is lower, the degree of distortion in the waveform of each phase current is made as equal as possible while preventing heat generation from being biased toward the switch SW of a specific phase among the three phases. This can prevent deterioration in torque controllability.

Furthermore, the larger the torque command value Trq* is, the shorter the prescribed period TB is set, thereby preventing heat generation from being concentrated in the switch SW of a specific phase among the three phases.

<Modified example of second embodiment>
- In step S13 of FIG. 7, the mechanical angular frequency or rotational speed of the rotating electric machine 10 may be used instead of the electrical angular frequency ωe.

- Instead of setting the prescribed period TB to be shorter as the electrical angular frequency ωe is lower, the process of step S13 may be replaced with a process of switching the prescribed period TB in a binary manner. Specifically, when the electrical angular frequency ωe is higher than a predetermined frequency, the specified period TB is set to the first specified period, and when the electrical angular frequency ωe is less than or equal to the predetermined frequency, the specified period TB is set to be longer than the first specified period. It is sufficient to set the period to a shorter second specified period. Note that, similarly, the torque command value Trq* may also be switched in a binary manner.

<Third embodiment>
The third embodiment will be described below with reference to the drawings, focusing on the differences from the first and second embodiments. In this embodiment, instead of the drive signal generation method based on the carrier signal Sc, a drive signal generation method based on a pulse pattern is used.

FIG. 8 shows a block diagram of torque control processing according to this embodiment. In FIG. 8, the same components as those shown in FIG. 2 are given the same reference numerals for convenience.

The torque controller 71 determines the voltage phase δ, which is the phase of the voltage vector Vnvt in the dq coordinate system, and the command modulation rate Mr, based on the torque command value Trq*, the d- and q-axis currents Idr and Iqr, and the power supply voltage detection value Vdc. Calculate. The voltage vector Vnvt is defined by the d-axis voltage Vd, which is the d-axis component of the voltage vector in the dq coordinate system, and the q-axis voltage Vq, which is the q-axis component. The voltage phase δ is, for example, based on the positive direction of the d-axis, and the counterclockwise direction from this reference is defined as the positive direction.

The command modulation rate Mr is a value obtained by normalizing the voltage amplitude Vr, which is the magnitude of the voltage vector Vnvt, by the power supply voltage detection value Vdc. The voltage amplitude Vr is defined as the square root of the sum of the square value of the d-axis voltage Vd and the square value of the q-axis voltage Vq. The command modulation rate Mr may be calculated using the following formula (eq2), for example.

角度算出部７２は、電圧位相δに電気角θｅを加算した値として、固定座標系を基準とした電圧ベクトルＶｎｖｔの位相である実位相θｒを算出する。なお、固定座標系の基準としては、例えば固定座標系のＵ相を用いることができる。

The angle calculation unit 72 calculates the actual phase θr, which is the phase of the voltage vector Vnvt with respect to the fixed coordinate system, as a value obtained by adding the electrical angle θe to the voltage phase δ. Note that, as a reference for the fixed coordinate system, for example, the U phase of the fixed coordinate system can be used.

The pattern generation unit 73 generates a pulse pattern that is a command value of a switching pattern based on the electrical angular frequency ωe, the command modulation rate Mr, and the actual phase θr. The pulse pattern is stored in the pattern storage unit 74 as map information associated with the electrical angular frequency ωe and the command modulation rate Mr. The pattern storage unit 74 is a non-transitional tangible recording medium other than ROM (for example, a nonvolatile memory other than ROM). The pattern generation unit 73 selects a corresponding pulse pattern from among the stored pulse patterns based on the electrical angular frequency ωe and the command modulation rate Mr.

For example, as shown in FIG. 9, the pulse pattern is defined over an electrical angle of 0 to 360 degrees. The pulse pattern is map information in which each of the on command and the off command is associated with the electrical angle θe. Incidentally, the pulse pattern may be associated with the voltage amplitude Vr instead of the command modulation rate Mr.

The pattern generation section 73 outputs the selected pulse pattern to the signal generation section 75 based on the input real phase θr. Here, the output pulse pattern of each phase is a signal in which the selected pulse pattern is shifted by 120 electrical degrees. In this embodiment, among the pulse patterns of each phase, the U-phase one is referred to as the U-phase PWM signal GU*, the V-phase pulse pattern is referred to as the V-phase PWM signal GV*, and the W-phase pulse pattern is referred to as the W-phase PWM signal. It is called GW*.

The signal generation unit 75 performs processing to separate the logic inversion timings of the U, V, and W phase PWM signals GU*, GV*, and GW* and their logic inversion signals by a dead time DT, so that each switch SUH, Drive signals GUH, GUL, GVH, GVL, GWH, and GWL of SUL, SVH, SVL, SWH, and SWL are generated. FIG. 10 shows a method of generating U-phase upper and lower arm drive signals GUH and GUL. 10(a) shows the transition of the U-phase PWM signal GU*, FIG. 10(b) shows the transition of the logic inversion signal of the U-phase PWM signal GU*, and FIGS. 10(c) and (d) show the transition of the U-phase PWM signal GU*. The transition of the upper and lower arm drive signals GUH and GUL is shown.

Note that in this embodiment, the two-phase conversion section 51, speed calculation section 59, torque controller 71, angle calculation section 72, pattern generation section 73, pattern storage section 74, and signal generation section 75 correspond to the "control section". .

The speed reduction process shown in FIG. 4 or FIG. 7 can also be applied to the configuration in which the pulse pattern described above is used.

<Other embodiments>
Note that each of the above embodiments may be modified and implemented as follows.

- In each of the above embodiments, the speed reduction process is executed when the switch SW is switched to the off state, but the speed reduction process is not limited to this, and the speed reduction process may be executed when the switch SW is switched to the on state. In this case, the switching speed for switching to the on state may be changed by changing the resistance value of the charging resistor 62, for example.

Furthermore, speed reduction processing may be executed upon each of switching to the off state and switching to the on state.

- The method of changing the switching speed is not limited to the method of changing the resistance value of the gate resistor connected to the gate of the switch SW. For example, if the drive circuit Dr has a configuration that can switch the ground potential, which is the discharge destination of the gate charge of the switch SW, to a potential lower than the source potential of the switch SW, the switching speed can be increased by lowering the ground potential. can do.

- The carrier signal is not limited to a triangular wave signal, but may be a sawtooth wave signal, for example.

- The switches constituting the inverter are not limited to N-channel MOSFETs, and may be, for example, IGBTs. In this case, the high potential side terminal of the switch becomes the collector, and the low potential side terminal becomes the emitter. Further, in this case, it is sufficient that a freewheeling diode is connected in antiparallel to the switch.

・Inverters are not limited to 3-phase ones.

- The control amount of the rotating electric machine is not limited to torque, but may be rotation speed, for example.

- The control unit and the method described in the present disclosure are implemented by a dedicated computer provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. May be realized. Alternatively, the controller and techniques described in this disclosure may be implemented by a dedicated computer provided by a processor configured with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be implemented using a combination of a processor and memory programmed to perform one or more functions and a processor configured by one or more hardware logic circuits. It may be implemented by one or more dedicated computers configured. The computer program may also be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

10... Rotating electric machine, 11U to 11W... U to W phase winding, 20... Inverter, 50... Microcomputer.

Claims (14)

a multiphase rotating electric machine (10);
An inverter control device (50) applied to a system including an inverter (20) electrically connected to armature windings (11U to 11W) constituting the rotating electric machine,
a control unit that performs switching control of switches (SUH to SWL) of each phase forming the inverter in order to perform drive control of the rotating electrical machine;
A reduction unit that performs a speed reduction process to reduce the switching speed in the switching control of some of the phases from the switching speed in the switching control of the remaining phases,
The lowering part is
Among each phase , the phase that reduces the switching speed is sequentially switched every specified period (TB) ,
An inverter control device that sets the prescribed period to be shorter when the rotational speed of the rotating electric machine is low than when the rotational speed is high . a multiphase rotating electric machine (10);
An inverter control device (50) applied to a system including an inverter (20) electrically connected to armature windings (11U to 11W) constituting the rotating electric machine,
a control unit that performs switching control of switches (SUH to SWL) of each phase forming the inverter in order to control the control amount of the rotating electric machine to a command value ;
A reduction unit that performs a speed reduction process to reduce the switching speed in the switching control of some of the phases from the switching speed in the switching control of the remaining phases,
The lowering part is
Among each phase , the phase that reduces the switching speed is sequentially switched every specified period (TB) ,
An inverter control device that sets the prescribed period to be shorter when a current parameter, which is either the command value or the current value flowing through the armature winding, is large than when the current parameter is small. a multiphase rotating electric machine (10);
An inverter control device (50) applied to a system including an inverter (20) electrically connected to armature windings (11U to 11W) constituting the rotating electric machine,
a control unit that performs switching control of switches (SUH to SWL) of each phase forming the inverter in order to perform drive control of the rotating electrical machine;
A reduction unit that performs a speed reduction process to reduce the switching speed in the switching control of some of the phases from the switching speed in the switching control of the remaining phases,
The lowering unit sequentially switches a phase whose switching speed is lowered among each phase every prescribed period (TB) ,
comprising a counting section that counts the elapsed time after the phase that reduces the switching speed is switched by the reducing section,
The reducing unit is an inverter control device that switches a phase of each phase whose switching speed is to be reduced every time the elapsed time counted by the counting unit reaches the specified period. a multiphase rotating electric machine (10);
An inverter control device (50) applied to a system including an inverter (20) electrically connected to armature windings (11U to 11W) constituting the rotating electric machine,
a control unit that performs switching control of switches (SUH to SWL) of each phase forming the inverter in order to perform drive control of the rotating electrical machine;
A speed reduction process is performed in which the switching speed in the switching control of some of the phases is lower than the switching speed in the switching control of the remaining phases , when the rotational speed of the rotating electric machine is lower than a low speed threshold. a lowering portion provided that the
The lowering unit is an inverter control device that sequentially switches the phase whose switching speed is to be lowered among each phase every prescribed period (TB). A period obtained by dividing a predetermined period (TA) by the number of phases is set as the specified period,
2. The reducing unit sequentially switches the phase in which the switching speed is to be reduced in each of the specified periods so that the period for instructing to reduce the switching speed appears the same number of times in each phase in each of the predetermined periods. 4. The inverter control device according to any one of items 4 to 4 . The inverter control device according to any one of claims 1 to 3 , wherein the reduction unit performs the speed reduction process on the condition that the rotation speed of the rotating electrical machine is higher than a high-speed threshold. The control unit performs the switching control in order to control the control amount of the rotating electric machine to a command value,
5. The speed reduction unit performs the speed reduction process on condition that a current parameter, which is either the command value or the current value flowing through the armature winding, is larger than a threshold value. 2. The inverter control device according to item 1. The system includes a temperature sensor (43) that detects the temperature of the rotating electric machine or the inverter,
The inverter control device according to any one of claims 1 to 7 , wherein the reducing unit performs the speed reducing process on the condition that the temperature detected by the temperature sensor is higher than a high temperature threshold. The system includes a temperature sensor (43) that detects the temperature of the inverter,
The inverter control device according to any one of claims 1 to 7 , wherein the reducing unit performs the speed reducing process on the condition that the temperature detected by the temperature sensor is lower than a low temperature threshold. The system includes an atmospheric pressure sensor (44) that detects atmospheric pressure;
The inverter control device according to any one of claims 1 to 9 , wherein the reduction unit performs the speed reduction process on the condition that the air pressure detected by the air pressure sensor is lower than an air pressure threshold. a multiphase rotating electric machine (10);
an inverter (20) electrically connected to armature windings (11U to 11W) constituting the rotating electrical machine;
In a program applied to a system comprising a computer (50),
to the computer;
A process of controlling switching of switches (SUH to SWL) of each phase forming the inverter in order to perform drive control of the rotating electrical machine;
performing a speed reduction process of lowering the switching speed in the switching control of some of the phases from the switching speed in the switching control of the remaining phases;
In the speed reduction process,
Among each phase, the phase that reduces the switching speed is sequentially switched every specified period (TB),
A program that sets the prescribed period to be shorter when the rotational speed of the rotating electric machine is low than when the rotational speed is high. a multiphase rotating electric machine (10);
an inverter (20) electrically connected to armature windings (11U to 11W) constituting the rotating electrical machine;
In a program applied to a system comprising a computer (50),
to the computer;
In order to control the control amount of the rotating electric machine to a command value, a process of controlling switching of switches (SUH to SWL) of each phase forming the inverter;
performing a speed reduction process of lowering the switching speed in the switching control of some of the phases from the switching speed in the switching control of the remaining phases;
In the speed reduction process,
Among each phase, the phase that reduces the switching speed is sequentially switched every specified period (TB),
When a current parameter, which is either the command value or the current value flowing through the armature winding, is large, the specified period is set to be shorter than when the current parameter is small. a multiphase rotating electric machine (10);
an inverter (20) electrically connected to armature windings (11U to 11W) constituting the rotating electrical machine;
In a program applied to a system comprising a computer (50),
to the computer;
A process of controlling switching of switches (SUH to SWL) of each phase forming the inverter in order to perform drive control of the rotating electrical machine;
performing a speed reduction process of lowering the switching speed in the switching control of some of the phases from the switching speed in the switching control of the remaining phases;
In the speed reduction process, the phase whose switching speed is to be reduced among each phase is sequentially switched every prescribed period (TB),
causing the computer to execute a process of counting the elapsed time since the phase that reduces the switching speed is switched by the speed reduction process,
In the speed reduction process, each time the counted elapsed time reaches the specified period, the program switches the phase whose switching speed is to be reduced among the phases. a multiphase rotating electric machine (10);
an inverter (20) electrically connected to armature windings (11U to 11W) constituting the rotating electrical machine;
In a program applied to a system comprising a computer (50),
to the computer;
A process of controlling switching of switches (SUH to SWL) of each phase forming the inverter in order to perform drive control of the rotating electrical machine;
A speed reduction process is performed in which the switching speed in the switching control of some of the phases is lower than the switching speed in the switching control of the remaining phases, when the rotational speed of the rotating electrical machine is lower than a low speed threshold. A process to be performed on the condition that
A program that, in the speed reduction process, sequentially switches the phase whose switching speed is to be reduced among each phase every prescribed period (TB).

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