JP7541477B2 - Rotating electric machine control device, program, and rotating electric machine control method - Google Patents

Description

The present invention relates to a control device for a rotating electric machine , a program, and a control method for a rotating electric machine .

Conventionally, a rotating electric machine system including a rotating electric machine having an open winding is known (for example, Patent Document 1). In this rotating electric machine system, a first inverter is connected to the first end of each phase winding constituting the rotating electric machine, and a second inverter is connected to the second end. In addition, the high potential side of the first inverter and the high potential side of the second inverter are connected by a high potential side connection line, and the low potential side of the first inverter and the low potential side of the second inverter are connected by a low potential side connection line. In the above-mentioned rotating electric machine system, when driving the rotating electric machine, H-bridge driving can be performed to perform switching driving on the upper and lower arm switches of each inverter.

In H-bridge driving, switching is performed in one of the first and second inverters, and in the other inverter, one of the upper and lower arm switches is turned off and the other arm switch is turned on. The inverter that performs switching driving is switched every predetermined period. Therefore, for example, if the period in which the first inverter performs switching driving is longer than the period in which the second inverter performs switching driving, switching loss is concentrated in the upper and lower arm switches of the first inverter, and the temperature of these switches rises excessively. In the technology described in Patent Document 1, the first and second inverters are driven by drive signals with the same amplitude but reversed polarity. This prevents switching loss from concentrating in one of the first and second inverters.

JP 2017-93077 A

A bootstrap circuit is known as a circuit for driving the upper arm switches of the first and second inverters. In a bootstrap circuit, when a lower arm switch is turned on, a bootstrap capacitor in the bootstrap circuit provided corresponding to the upper arm switch is charged. The charge stored in the bootstrap capacitor then turns on the upper arm switch.

In H-bridge drive, in inverters that do not perform switching drive, the upper arm switch may be kept on. In this case, if the upper arm switch is kept on for a long period of time, the bootstrap capacitor may discharge, causing the voltage of the bootstrap capacitor to drop, making it impossible to keep the upper arm switch on. As a result, there is a concern that the first and second inverters may not be able to continue operating.

The present invention has been made in consideration of the above-mentioned circumstances, and its object is to provide a control device , program, and control method for a rotating electric machine that can properly continue to drive the first and second inverters.

The means for solving the above problem is a control device for a rotating electric machine applied to a rotating electric machine system including a rotating electric machine having a multi-phase winding, a first inverter having upper arm switches and lower arm switches connected in series for each phase, the connection point between the upper arm switches and the lower arm switches being connected to a first end of both ends of the winding for each phase, a second inverter having upper arm switches and lower arm switches connected in series for each phase, the connection point between the upper arm switches and the lower arm switches being connected to a second end of both ends of the winding for each phase, a high-potential side connection line connecting the high-potential side of the first inverter and the high-potential side of the second inverter, and a low-potential side connection line connecting the low-potential side of the first inverter and the low-potential side of the second inverter, the rotating electric machine system including a first bootstrap circuit having a first bootstrap capacitor that generates a voltage for turning on the upper arm switches of the first inverter, and a second bootstrap circuit having a first bootstrap capacitor that generates a voltage for turning on the upper arm switches of the second inverter. and a second bootstrap circuit having a bootstrap capacitor. The control unit switches between an upper arm on fixing operation in which, in one of the first and second inverters, the upper arm switch is kept on and the lower arm switch is kept off, and in the other inverter, switching drive of the upper and lower arm switches is performed, and a lower arm on fixing operation in which, in the one inverter, switching drive of the upper and lower arm switches is performed, and in the other inverter, the upper arm switch is kept off and the lower arm switch is kept on. The control unit switches from the upper arm on fixing operation to the lower arm on fixing operation.

In a rotating electric machine system including a rotating electric machine having an open winding, when the rotating electric machine is driven using a first inverter and a second inverter, an upper arm fixed on operation is performed. In the upper arm fixed on operation, the upper arm switch of one of the first and second inverters (hereinafter, the target inverter) is kept on. Therefore, if the operating period of the upper arm fixed on operation is prolonged, there is a concern that the upper arm switch of the target inverter may not be kept on due to the discharge of the bootstrap capacitor of the bootstrap circuit corresponding to the target inverter.

In this regard, in the above configuration, the upper arm on-fixed operation and the lower arm on-fixed operation are switched. In the lower arm on-fixed operation, the upper and lower arm switches in the target inverter are switched to charge the bootstrap capacitor corresponding to the target inverter. Therefore, when the voltage of the corresponding capacitor acquired during the upper arm on-fixed operation is lower than the voltage threshold, the upper arm on-fixed operation is switched to the lower arm on-fixed operation to suppress excessive discharge of the corresponding capacitor. Furthermore, in the upper arm on-fixed operation and the lower arm on-fixed operation, the polarity of the phase voltage applied to the windings of each phase of the rotating electric machine is the same. Therefore, by switching the upper arm on-fixed operation to the lower arm on-fixed operation, the controllability of the rotating electric machine associated with the switching is suppressed, and the first and second inverters can be appropriately continued to be driven.

FIG. 1 is an overall configuration diagram of a rotating electric machine system. FIG. 4 is a diagram showing a circuit configuration of a first drive circuit. 11A to 11C are diagrams showing battery voltage application states to a U-phase winding in the first to fourth operations. 5 is a flowchart of a switching control process according to the first embodiment. 4 is a time chart showing an example of a switching control process. 4 is a time chart showing the transition of the states of the switches of the first and second inverters; FIG. 2 is a diagram showing a circuit configuration of a signal generating circuit. FIG. 4 is a diagram showing a process of generating a first control signal and a second control signal. FIG. 4 is a diagram showing a process of switching between a first control signal and a second control signal. 10 is a flowchart of a switching control process according to the second embodiment. 13 is a flowchart of a switching control process according to the third embodiment. 13 is a flowchart of a switching control process according to the fourth embodiment. FIG. 13 is a graph showing the relationship between the temperature of the lower arm switch and the reference charging period.

First Embodiment
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment in which a control device for a rotating electric machine according to the present invention is applied to an in-vehicle rotating electric machine system 100 will be described below with reference to the drawings.

As shown in FIG. 1, the rotating electric machine system 100 according to this embodiment includes a rotating electric machine 10, a first inverter 20, a second inverter 30, and a control device 50 that controls the rotating electric machine 10.

The rotating electric machine 10 has the functions of regenerative power generation and power driving, and is specifically an MG (Motor Generator). The rotating electric machine 10 inputs and outputs electric power to and from the battery 40. During power driving, the rotating electric machine 10 provides propulsive force to the vehicle using electric power supplied from the battery 40, and during regeneration, the rotating electric machine 10 generates electric power using the deceleration energy of the vehicle and outputs the electric power to the battery 40, which is a DC power source.

The rotating electric machine 10 has an open-type three-phase winding 11. The winding 11 includes U-, V-, and W-phase windings 11U, 11V, and 11W. The rotor of the rotating electric machine 10 is connected to the driving wheels of the vehicle so as to transmit power. The rotating electric machine 10 is, for example, a synchronous machine.

The windings 11 of each phase of the rotating electric machine 10 are connected to the battery 40 via the first and second inverters 20 and 30. The battery 40 is a rechargeable storage battery, specifically, a battery pack in which multiple lithium ion storage batteries are connected in series. Note that the battery 40 may be another type of storage battery.

The first and second inverters 20, 30 convert the DC power input from the battery 40 into AC power and output it to the rotating electric machine 10. In this embodiment, the first and second inverters 20, 30 are three-phase. The first and second inverters 20, 30 each have three phases of upper arm switches and lower arm switches connected in series as switching elements.

The first inverter 20 is configured by connecting in parallel a series connection of upper arm switches 22 (22A, 22B, 22C) which are high-potential side switching elements, and lower arm switches 23 (23A, 23B, 23C) which are low-potential side switching elements. A first end of the winding 11 of the corresponding phase of the rotating electric machine 10 is connected to the connection point between the upper arm switch 22 and the lower arm switch 23 of each phase. In this embodiment, voltage-controlled semiconductor switching elements, more specifically, N-channel MOSFETs, are used as the switches 22 and 23. A body diode 24 is built into each switch 22 and 23.

The first inverter 20 also includes a first temperature sensor 25 and a first drive circuit 26. The first temperature sensor 25 detects the temperatures of the switches 22 and 23. Hereinafter, the temperature of the upper arm switch 22 detected by the first temperature sensor 25 is referred to as TU1, and the temperature of the lower arm switch 23 detected by the first temperature sensor 25 is referred to as TD1. In this embodiment, the first temperature sensor 25 is a temperature-sensitive diode, and the switches 22 and 23 and the first temperature sensor 25 are integrated as a semiconductor module. The first temperature sensor 25 may be a thermistor or a water temperature sensor that detects the temperature of the cooling water that cools the switches 22 and 23. The same applies to the second temperature sensor 35 described later.

The first drive circuit 26 drives the upper arm switch 22 and the lower arm switch 23 of each phase in the first inverter 20 based on the first drive signal SG1 output from the control device 50. FIG. 2(A) shows the circuit configuration of the first drive circuit 26. The first drive circuit 26 includes a first bootstrap circuit GB1, a first upper arm drive circuit GH1 that drives the upper arm switch 22, and a first lower arm drive circuit GL1 that drives the lower arm switch 23.

The first bootstrap circuit GB1 uses the charge stored in the first bootstrap capacitor CA1 to generate a voltage for turning on the upper arm switch 22. The first electrode of the first bootstrap capacitor CA1 is connected to the high-voltage terminal of the DC voltage source BA via the bootstrap diode DA and resistor RA, and the second electrode of the first bootstrap capacitor CA1 is connected to the connection point between the upper arm switch 22 and the lower arm switch 23 of the corresponding phase. The low-voltage terminal of the DC voltage source BA is connected to the low-voltage main terminal of the lower arm switch 23.

In the first bootstrap circuit GB1, during the on-period when the lower arm switch 23 is on, the first bootstrap capacitor CA1 is charged by the DC voltage source BA via the bootstrap diode DA and resistor RA. The first upper arm drive circuit GH1 is connected to the first and second electrodes of the bootstrap capacitor CA, and during the off-period when the lower arm switch 23 is off, turns on the upper arm switch 22 using the charge stored in the bootstrap capacitor CA. In other words, the first bootstrap capacitor CA1 generates a voltage for turning on the upper arm switch 22 using the stored charge, and the first upper arm drive circuit GH1 turns on the upper arm switch 22 using the voltage generated by the bootstrap capacitor CA. The first lower arm drive circuit GL1 is connected to the high voltage terminal and low voltage terminal of the DC voltage source BA, and turns on the lower arm switch 23 using the output voltage (e.g., rated voltage) of the DC voltage source BA.

The second inverter 30 is configured by connecting in parallel a series connection of upper arm switches 32 (32A, 32B, 32C) which are high-potential side switching elements, and lower arm switches 33 (33A, 33B, 33C) which are low-potential side switching elements. The second end of the winding 11 of the corresponding phase of the rotating electric machine 10 is connected to the connection point between the upper arm switch 32 and the lower arm switch 33 of each phase. In this embodiment, voltage-controlled semiconductor switching elements, more specifically, N-channel MOSFETs, are used as the switches 32 and 33. Each switch 32 and 33 has a built-in body diode 24.

The second inverter 30 also includes a second temperature sensor 35 and a second drive circuit 36. The second temperature sensor 35 detects the temperatures of the switches 32, 33. Hereinafter, the temperature of the upper arm switch 32 detected by the second temperature sensor 35 is referred to as TU2, and the temperature of the lower arm switch 33 detected by the second temperature sensor 35 is referred to as TD2. In this embodiment, the second temperature sensor 35 is a temperature-sensitive diode, and the switches 32, 33 and the second temperature sensor 35 are integrated as a semiconductor module.

The second drive circuit 36 drives the upper arm switch 32 and the lower arm switch 33 of each phase in the second inverter 30 based on the second drive signal SG2 output from the control device 50. FIG. 2(B) shows the circuit configuration of the second drive circuit 36. The second drive circuit 36 includes a second bootstrap circuit GB2, a second upper arm drive circuit GH2 that drives the upper arm switch 32, and a second lower arm drive circuit GL2 that drives the lower arm switch 33.

The second bootstrap circuit GB2 uses the charge stored in the second bootstrap capacitor CA2 to generate a voltage for turning on the upper arm switch 32. Note that the circuit configuration of the second bootstrap circuit GB2 is the same as the circuit configuration of the first bootstrap circuit GB1, and therefore a duplicated description will be omitted.

The high potential side of the battery 40, the high potential side of the first inverter 20, and the high potential side of the second inverter 30 are connected by a high potential side connection line LE such as a bus bar. The low potential side of the battery 40, the low potential side of the first inverter 20, and the low potential side of the second inverter 30 are connected by a low potential side connection line LG such as a bus bar. The high potential side connection line LE and the low potential side connection line LG are also connected by a capacitor 41. The capacitor 41 connects between the high potential side connection line LE and the low potential side connection line LG on the battery 40 side of the first inverter 20.

The rotating electric machine system 100 includes a first voltage sensor 51 that detects the power supply voltage of the battery 40, a current sensor 52 that detects the phase current flowing through the windings 11 of each phase of the rotating electric machine 10, and an angle sensor 53 (e.g., a resolver) that detects the rotation angle of the rotating electric machine 10. The rotating electric machine system 100 also includes a second voltage sensor 54 that detects a first capacitor voltage, which is the terminal voltage of the first bootstrap capacitor CA1, and a third voltage sensor 55 that detects a second capacitor voltage, which is the terminal voltage of the second bootstrap capacitor CA2. The detection values of the sensors 51 to 55 are input to the control device 50. The control device 50 controls the first inverter 20 and the second inverter 30 based on the input detection values to control the control amount of the rotating electric machine 10 to its command value. The control amount is, for example, torque.

Specifically, in controlling the first inverter 20, the control device 50 outputs a first drive signal SG1 corresponding to each switch 22, 23 to alternately turn on the upper arm switch 22 and the lower arm switch 23 with dead time in between. The first drive signal SG1 is either an ON command to switch on each switch 22, 23 or an OFF command to switch off each switch 22, 23. In the first drive circuit 26, the first bootstrap capacitor CA1 is charged during an ON period in which the lower arm switch 23 is turned on by the first drive signal SG1 of an ON command. The first upper arm drive circuit GH1 outputs a gate drive signal to the gate of the upper arm switch 22 using the charge accumulated in the first bootstrap capacitor CA1 during an OFF period in which the lower arm switch 23 is turned off by the first drive signal SG1 of an OFF command. As a result, the gate voltage of the upper arm switch 22 becomes equal to or higher than the threshold voltage Vth, and the upper arm switch 22 is turned on.

In addition, in controlling the second inverter 30, the control device 50 outputs a second drive signal SG2 corresponding to each switch 32, 33 so as to alternately turn on the upper arm switch 32 and the lower arm switch 33 with dead time in between. The second drive signal SG2 is either an ON command to switch on each switch 32, 33 or an OFF command to switch off each switch 32, 33. In the second drive circuit 36, the second bootstrap capacitor CA2 is charged during an ON period in which the lower arm switch 33 is turned on by the second drive signal SG2 of an ON command. The second upper arm drive circuit GH2 outputs a gate drive signal to the gate of the upper arm switch 32 using the charge stored in the second bootstrap capacitor CA2 during an OFF period in which the lower arm switch 33 is turned off by the second drive signal SG2 of an OFF command. This turns on the upper arm switch 32.

The control device 50 further acquires the operating state of the rotating electric machine 10 based on the input detection value. The operating state of the rotating electric machine 10 is, for example, a high-speed rotation state or a low-speed rotation state. Then, based on the acquired operating state, the control device 50 generates a first drive signal SG1 and a second drive signal SG2.

For example, when the rotating electric machine 10 is in a high-speed rotating state, the first inverter 20 and the second inverter 30 are H-bridge driven. In H-bridge driving, one of the first inverter 20 and the second inverter 30 is controlled by PWM driving as a switching drive. PWM driving is a drive that controls the state of each switch based on a comparison of the magnitude between a voltage command value V*, which is a target value of the output voltage to the rotating electric machine 10, and a carrier signal SD, such as a triangular wave signal. The method of generating the drive signal for each switch based on the voltage command value V* and the carrier signal SD will be described later with reference to FIG. 7. In the other inverter, one of the upper arm switches and the lower arm switches is fixed on, and the other switch is fixed off.

In H-bridge drive, the first and second operations are performed alternately. FIG. 3 illustrates the manner in which the battery voltage is applied to the U-phase winding 11U in the first and second operations. Note that the manner in which the battery voltage is applied to the V-phase winding 11V and the W-phase winding 11W is the same as the manner in which the battery voltage is applied to the U-phase winding 11U, and therefore a description thereof will be omitted.

As shown in FIG. 3, in the first operation, the upper and lower arm switches 22A, 23A of the first inverter 20 are PWM-driven, and the upper arm switch 32A of the second inverter 30 is controlled to be turned on and the lower arm switch 33A to be turned off. As a result, a phase voltage of a polarity in which the second inverter 30 is at a high potential and the first inverter 20 is at a low potential is applied to the U-phase winding 11U of the rotating electric machine 10.

In the second operation, the upper and lower arm switches 32A, 33A of the second inverter 30 are PWM-driven, and the upper arm switch 22A of the first inverter 20 is controlled to be turned on and the lower arm switch 23A is controlled to be turned off. As a result, a phase voltage of a polarity in which the first inverter 20 side is at a high potential and the second inverter 30 side is at a low potential is applied to the U-phase winding 11U of the rotating electric machine 10. Therefore, by alternately performing the first operation and the second operation, an AC current flows in the windings 11 of each phase of the rotating electric machine 10. Hereinafter, the control in which the first operation and the second operation are alternately performed is referred to as the first AC control. In this embodiment, the first operation and the second operation correspond to the "upper arm on fixed operation".

In the first and second operations, in the inverters where PWM driving is not performed, the upper arm switches 22A, 32A are turned on and the lower arm switches 23A, 33A are turned off. As a result, the period during which the upper arm switches 22A, 32A are turned on is extended, and the first and second capacitor voltages VC1, VC2 are lowered below the threshold voltage Vth for turning on the upper arm switches 22A, 32A of the first and second inverters 20, 30 due to the discharge of the first and second bootstrap capacitors CA1, CA2. In this case, it is possible that the upper arm switches 22A, 32A cannot be kept on, and there is a concern that the first and second inverters 20, 30 cannot continue to be driven.

Therefore, in this embodiment, in addition to the first AC control, a second AC control is performed in the H-bridge drive, in which the third operation and the fourth operation are alternately performed. FIG. 3 illustrates the battery voltage application to the U-phase winding 11U in the third and fourth operations. Note that the battery voltage application to the V-phase winding 11V and the W-phase winding 11W is the same as the battery voltage application to the U-phase winding 11U, and a description thereof will be omitted.

As shown in FIG. 3, in the third operation, the upper and lower arm switches 22A, 23A of the first inverter 20 are PWM-driven, and the upper arm switch 32A of the second inverter 30 is controlled to be turned off and the lower arm switch 33A is controlled to be turned on. As a result, a phase voltage of a polarity in which the first inverter 20 side is at a high potential and the second inverter 30 side is at a low potential is applied to the U-phase winding 11U of the rotating electric machine 10.

In the fourth operation, the upper and lower arm switches 32A, 33A of the second inverter 30 are PWM driven, and the upper arm switch 22A of the first inverter 20 is controlled to be turned off and the lower arm switch 23A is controlled to be turned on. As a result, a phase voltage of a polarity in which the second inverter 30 side is at a high potential and the first inverter 20 side is at a high potential is applied to the U-phase winding 11U of the rotating electric machine 10. Therefore, by alternately performing the third operation and the fourth operation, an AC current flows through the windings 11 of each phase of the rotating electric machine 10. In this embodiment, the third operation and the fourth operation correspond to a "lower arm on fixed operation".

In this embodiment, the control device 50 acquires the first and second capacitor voltages VC1 and VC2 during the first AC control, and performs a switching control process to switch the first AC control to the second AC control when either one of these voltages VC1 and VC2 is lower than the first voltage threshold VDth. The first voltage threshold VDth is set to a voltage higher than the threshold voltage Vth of the upper arm switches 22 and 32 and lower than the output voltage of the DC voltage source BA.

Figure 4 shows a flowchart of the switching control process of this embodiment. The control device 50 repeatedly performs the switching control process at predetermined intervals during the power running operation or regenerative operation of the rotating electric machine 10.

When the switching control process is started, first in step S11, it is determined whether it is the first control period in which the rotating electric machine 10 is subjected to the first AC control. In this embodiment, the first AC control and the second AC control are switched and performed every predetermined control period, and if it is the first control period, a positive determination is made in step S11 and the process proceeds to step S12. On the other hand, if it is the second control period, a negative determination is made in step S11 and the process proceeds to step S33.

In step S12, it is determined whether the first flag F1 is on. The first flag F1 is turned on when the first capacitor voltage VC1 of the first bootstrap capacitor CA1 becomes lower than the first voltage threshold VDth, and is turned off when the first capacitor voltage VC1 becomes higher than the second voltage threshold VUth after the first flag F1 is turned on. The second voltage threshold VUth is set to a voltage higher than the first voltage threshold VDth and lower than the output voltage of the DC voltage source BA. If the determination in step S12 is positive, the process proceeds to step S30. On the other hand, if the determination in step S12 is negative, the process proceeds to step S13.

In step S13, it is determined whether the second flag F2 is on. The second flag F2 is turned on when the second capacitor voltage VC2 of the second bootstrap capacitor CA2 becomes lower than the first voltage threshold VDth, and is turned off when the second capacitor voltage VC2 becomes higher than the second voltage threshold VUth after the second flag F2 is turned on. If the determination in step S13 is positive, the process proceeds to step S34. On the other hand, if the determination in step S13 is negative, the process proceeds to step S14.

In step S14, the first and second capacitor voltages VC1 and VC2 are acquired. In the following step S15, it is determined whether or not the first capacitor voltage VC1 acquired in step S14 is lower than the first voltage threshold VDth. If a positive determination is made in step S15, the first flag F1 is switched on in step S16, and the process proceeds to step S20. On the other hand, if a negative determination is made in step S15, the process proceeds to step S17. Note that in this embodiment, the process of step S14 corresponds to the "voltage acquisition unit."

In step S17, it is determined whether the second capacitor voltage VC2 acquired in step S14 is lower than the first voltage threshold VDth. If the determination in step S17 is positive, the second flag F2 is switched on in step S18, and the process proceeds to step S20. On the other hand, if the determination in step S17 is negative, the first AC control is performed in step S19, and the switching control process is terminated.

In step S20, the AC control of the rotating electric machine 10 is switched to the second AC control. In the following step S21, the second AC control is implemented, and the switching control process is terminated.

Meanwhile, in step S30, the first capacitor voltage VC1 is acquired. In the following step S31, it is determined whether or not the first capacitor voltage VC1 acquired in step S30 is higher than the second voltage threshold VUth. If the determination in step S31 is positive, the first flag F1 is switched off in step S32, and the process proceeds to step S37. On the other hand, if the determination in step S31 is negative, the second AC control is implemented in step S33, and the switching control process is terminated.

In addition, in step S34, the second capacitor voltage VC2 is acquired. In the following step S35, it is determined whether the second capacitor voltage VC2 acquired in step S34 is higher than the second voltage threshold VUth. If the determination in step S35 is positive, the second flag F2 is switched off in step S36, and the process proceeds to step S37. On the other hand, if the determination in step S35 is negative, the second AC control is performed in step S33, and the switching control process is terminated.

In step S37, the AC control of the rotating electric machine 10 is switched to the first AC control. In the following step S38, the first AC control is performed, and the switching control process ends. In this embodiment, the processes of steps S20 and S37 correspond to the "control unit."

Next, FIG. 5 shows an example of the switching control process. FIG. 5 shows the transition of the charge/discharge state of the first bootstrap capacitor CA1 during the first control period. In FIG. 5, (A) shows the transition of the charge/discharge state of the first bootstrap capacitor CA1, (B) shows the transition of the AC control of the rotating electric machine 10, and (C) shows the transition of the first flag F1.

As shown in FIG. 5, during the second control period up to time t1, the first bootstrap capacitor CA1 is charged by the third and fourth operations, and the first flag F1 is turned off.

When the first control period is entered at time t1, the AC control of the rotating electric machine 10 is switched from the second AC control to the first AC control. As a result, the first bootstrap capacitor CA1 is discharged by the second operation, and the first capacitor voltage VC1 drops. Note that in the first AC control, the first bootstrap capacitor CA1 is charged by the first operation, but since the amount of discharge by the second operation is greater than the amount of charge by the first operation, the first bootstrap capacitor CA1 is in a discharged state.

Then, when the first capacitor voltage VC1 falls below the first voltage threshold VDth at time t2, the first flag F1 is turned on, and the AC control of the rotating electric machine 10 is switched from the first AC control to the second AC control. In other words, the second AC control is performed during the first control period.

In the second AC control, the first bootstrap capacitor CA1 is charged by the third and fourth operations. Then, when the first capacitor voltage VC1 becomes higher than the second voltage threshold VUth at a later time t3, the first flag F1 is turned off, and the AC control of the rotating electric machine 10 is switched from the second AC control to the first AC control. In other words, the AC control of the rotating electric machine 10, which was temporarily in the second AC control during the first control period, returns to the first AC control.

When the first control period ends at time t4, the AC control of the rotating electric machine 10 switches from the first AC control to the second AC control.

Next, Fig. 6 shows the transition of the states of the switches 22, 23, 32, and 33 of the first and second inverters 20 and 30 in the first AC control and the second AC control. In Fig. 6, (A) shows the transition of the phase voltage applied to the winding 11 of each phase, (B) shows the transition of the drive state of the upper arm switch 22, (C) shows the transition of the drive state of the lower arm switch 23, (D) shows the transition of the drive state of the upper arm switch 32, and (E) shows the transition of the drive state of the lower arm switch 33.

As shown in FIG. 6, in the first control period in which the first AC control is performed, the first operation and the second operation are alternately performed N1 times. N1 times is an integer equal to or greater than 2.

In the first and second operations, the upper arm switch 22 of the first inverter 20 is controlled by a first control signal SC1. In a first operation period in which the first operation is performed, the first control signal SC1 is switched between a state in which an ON command is output (hereinafter, ON output state) and a state in which an OFF command is output (hereinafter, OFF output state), and is maintained in the ON output state in a second operation period in which the second operation is performed. In addition, the lower arm switch 23 of the first inverter 20 is controlled by a first inverted signal SR1 that inverts the ON output state and the OFF output state of the first control signal SC1. In other words, in the first and second operations, the first drive signal SG1 is constituted by the first control signal SC1 and the first inverted signal SR1.

The upper arm switch 32 of the second inverter 30 is controlled by a second control signal SC2. The second control signal SC2 is maintained in an on output state during the first operation period, and is switched between an on output state and an off output state during the second operation period. The lower arm switch 33 of the second inverter 30 is controlled by a second inverted signal SR2 that inverts the on output state and the off output state of the second control signal SC2. That is, in the first operation and the second operation, the second drive signal SG2 is constituted by the second control signal SC2 and the second inverted signal SR2.

During the second control period in which the second AC control is performed, the third operation and the fourth operation are alternately performed N2 times. N2 times is an integer equal to or greater than 2. The first to fourth operations are alternately performed by switching between the first AC control and the second AC control. Note that the number of repetitions N2 may be equal to or different from the number of repetitions N1.

In the third and fourth operations, the upper arm switch 22 of the first inverter 20 is controlled by the second inversion signal SR2, and the lower arm switch 23 of the first inverter 20 is controlled by the second control signal SC2. In other words, in the third and fourth operations, the first drive signal SG1 is composed of the second inversion signal SR2 and the second control signal SC2.

The upper arm switch 32 of the second inverter 30 is controlled by the first inversion signal SR1, and the lower arm switch 33 of the second inverter 30 is controlled by the first control signal SC1. In other words, in the third and fourth operations, the second drive signal SG2 is constituted by the first inversion signal SR1 and the first control signal SC1.

In other words, in this embodiment, the control signals SC1, SC2 and inverted signals SR1, SR2 input to each inverter 20, 30 are switched between the first AC control and the second AC control. Also, in each inverter 20, 30, the types of signals input to the upper arm switches 22, 32 and the lower arm switches 23, 33 are switched. This allows the states of the switches 22, 23, 32, 33 of the first and second inverters 20, 30 to be controlled using the same control signals SC1, SC2.

Next, a method for generating the first control signal SC1 and the second control signal SC2 will be described with reference to Figures 7 and 8. Figure 7 shows the circuit configuration of a signal generation circuit 60 that generates the first control signal SC1 and the second control signal SC2. The signal generation circuit 60 is provided in the control device 50.

Figure 8 shows the first control signal SC1 and the second control signal SC2 for one phase. As shown in Figure 8, the first control signal SC1 and the second control signal SC2 are generated based on the voltage command value V* and the carrier signal SD. The phase of the voltage command value V* in each phase is shifted by 120° in electrical angle, and a common carrier signal SD is used for each phase. Note that the carrier signal SD as the carrier wave in this embodiment is a triangular wave signal with an amplitude of VA and a center voltage of zero.

As shown in FIG. 7, the first adder circuit 61 acquires the voltage command value V* and adds VA, which is the amplitude of the carrier signal SD, to the acquired voltage command value V*. The first adder circuit 61 outputs the first voltage command value V1* after the addition to the non-inverting input terminal 62A of the first operational amplifier 62. As shown in FIG. 8(C), the first voltage command value V1* becomes a signal whose center voltage is VA.

The carrier signal SD is input to the inverting input terminal 62B of the first operational amplifier 62. The first operational amplifier 62 outputs from the output terminal 62C a first control signal SC1 that is an ON command when the first voltage command value V1* is greater than the carrier signal SD and is an OFF command when the first voltage command value V1* is less than the carrier signal SD.

The second adder circuit 63 also acquires the voltage command value V* and adds -VA to the acquired voltage command value V*. The second adder circuit 63 outputs the second voltage command value V2* after the addition to the negative input terminal 64B of the second operational amplifier 64. As shown in FIG. 8 (D), the second voltage command value V2* becomes a signal whose center voltage is -VA.

The carrier signal SD is input to the positive input terminal 64A of the second operational amplifier 64. The second operational amplifier 64 outputs from the output terminal 64C a second control signal SC2 that is an ON command when the carrier signal SD is greater than the second voltage command value V2* and is an OFF command when the carrier signal SD is less than the second voltage command value V2*.

Therefore, the first control signal SC1 is maintained in the ON output state in the half cycle in which the first voltage command value V1* is greater than the central voltage VA, and is switched between the ON output state and the OFF output state in the half cycle in which the first voltage command value V1* is less than the central voltage VA. The period in which the first control signal SC1 is maintained in the ON output state corresponds to the second operation period in the first control period, and corresponds to the third operation period in the second control period. The period in which the first control signal SC1 is switched between the ON output state and the OFF output state corresponds to the first operation period in the first control period, and corresponds to the fourth operation period in the second control period.

The second control signal SC2 is switched between the ON output state and the OFF output state in a half cycle in which the second voltage command value V2* is greater than the central voltage -VA, and is maintained in the ON output state in a half cycle in which the second voltage command value V2* is smaller than the central voltage -VA. In other words, the first control signal SC1 and the second control signal SC2 have different periods in which the ON output state and the OFF output state are switched and periods in which the ON output state is maintained. The period in which the second control signal SC2 is switched between the ON output state and the OFF output state corresponds to the second operation period in the first control period and corresponds to the third operation period in the second control period. The period in which the second control signal SC2 is maintained in the ON output state corresponds to the first operation period in the first control period and corresponds to the fourth operation period in the second control period.

When the first AC control and the second AC control are switched by switching the control period, the control signals SC1, SC2 and the inverted signals SR1, SR2 input to each inverter 20, 30 are switched. In this case, a predetermined switching period is required to switch between the first AC control and the second AC control, and the operation of the inverters 20, 30 is stopped during this switching period. On the other hand, when switching between the first AC control and the second AC control during the first control period, the operation of the inverters 20, 30 cannot be stopped throughout the switching period.

Therefore, in this embodiment, when the first AC control and the second AC control are switched during the first control period, the value to be added to the voltage command value V* is switched in the first and second adder circuits 61 and 63. Figure 9 shows the changes in the first and second voltage command values V1* and V2* when the first AC control and the second AC control are switched during the first control period.

9, in the first control period from time t1 to time t4, the AC control of the rotating electric machine 10 is switched from the first AC control to the second AC control at time t2. In this case, in the first adder circuit 61, the value added to the voltage command value V* is switched from VA to -VA. As a result, as shown in FIG. 9(C), the first voltage command value V1* is switched from a signal whose center voltage is VA to a signal whose center voltage is -VA. Also, in the second adder circuit 63, the value added to the voltage command value V* is switched from -VA to VA. As a result, as shown in FIG. 9(D), the second voltage command value V2* is switched from a signal whose center voltage is -VA to a signal whose center voltage is VA. As a result, the first control signal SC1 is switched to the second inverted signal SR2 in the absence of the above switching, and the second control signal SC2 is switched to the first inverted signal SR1 in the absence of the above switching. Therefore, the fourth operation is performed during the first operation period in the first AC control, and the third operation is performed during the second operation period in the first AC control.

Also, at time t3, the AC control of the rotating electric machine 10 is switched from the second AC control to the first AC control. In this case, in the first adder circuit 61, the value added to the voltage command value V* is switched from -VA to VA. Also, in the second adder circuit 63, the value added to the voltage command value V* is switched from VA to -VA. As a result, the first operation is performed during the first operation period in the first AC control, and the second operation is performed during the second operation period in the first AC control.

The present embodiment described above provides the following advantages:

- In this embodiment, the first capacitor voltage VC1 of the first bootstrap capacitor CA1 is acquired during the second operation of the first AC control, and when the acquired first capacitor voltage VC1 is lower than the first voltage threshold VDth, the first AC control is switched to the second AC control, and the second operation is switched to the third operation. In the third operation, the upper and lower arm switches 22, 23 in the first inverter 20 are PWM-driven to charge the first bootstrap capacitor CA1. Therefore, excessive discharge of the first bootstrap capacitor CA1 can be suppressed. In addition, the polarity of the phase voltage applied to the windings 11 of each phase of the rotating electric machine 10 is the same in the second operation and the third operation. Therefore, by switching from the second operation to the third operation, the controllability of the rotating electric machine 10 due to the switching is suppressed from decreasing, and the first and second inverters 20, 30 can be appropriately continued to be driven.

In addition, during the first operation of the first AC control, the second capacitor voltage VC2 of the second bootstrap capacitor CA2 is acquired, and when the acquired second capacitor voltage VC2 is lower than the first voltage threshold VDth, the first AC control is switched to the second AC control, and the first operation is switched to the fourth operation. In the fourth operation, the upper and lower arm switches 32, 33 in the second inverter 30 are PWM-driven to charge the second bootstrap capacitor CA2. Therefore, excessive discharge of the second bootstrap capacitor CA2 can be suppressed. In addition, in the first operation and the fourth operation, the polarity of the phase voltage applied to the winding 11 of each phase of the rotating electric machine 10 is the same. Therefore, by switching the first operation to the fourth operation, the controllability of the rotating electric machine 10 caused by the switching is suppressed, and the first and second inverters 20, 30 can be appropriately continued to be driven.

- In this embodiment, the first to fourth operations are switched. The inverters on which PWM driving is performed are different between the first and third operations and the second and fourth operations. In addition, the switches fixed to ON in the inverters on which PWM driving is not performed are different between the first and second operations and the third and fourth operations. Therefore, by switching between these operations, it is possible to prevent losses from being concentrated in a specific switch due to PWM driving and fixing to ON. In other words, it is possible to equalize the heat generation in each switch 22, 23, 32, and 33, and to prevent an excessive rise in temperature in a specific switch. In addition, in this embodiment, when the first and second operations cannot be continued due to the discharge of the first and second bootstrap capacitors CA1 and CA2, it is possible to properly continue driving the first and second inverters 20 and 30 by switching to the third and fourth operations while preventing an excessive rise in temperature in a specific switch.

- In this embodiment, if the first and second operations cannot be continued during the first control period due to the discharge of the first and second bootstrap capacitors CA1 and CA2, the operation is switched to the third and fourth operations. This allows the first and second inverters 20 and 30 to continue to be driven properly, so when the first and second operations are switched to the third and fourth operations, it is possible to maintain the third and fourth operations until the end of the first control period. In this case, the operating period of the first and second operations is shortened while the operating period of the third and fourth operations is increased, which raises concerns that the temperature of a particular switch may rise excessively.

In this respect, in the present embodiment, when the second operation is switched to the third operation by discharging the first bootstrap capacitor CA1, the first capacitor voltage VC1 of the first bootstrap capacitor CA1 after switching is obtained, and when the acquired first capacitor voltage VC1 is higher than the second voltage threshold VUth, the third operation is switched to the second operation. Also, when the first operation is switched to the fourth operation by discharging the second bootstrap capacitor CA2, the second capacitor voltage VC2 of the second bootstrap capacitor CA2 after switching is obtained, and when the acquired second capacitor voltage VC2 is higher than the second voltage threshold VUth, the fourth operation is switched to the first operation. This suppresses imbalance between the operation periods of the first and second operations and the operation periods of the third and fourth operations, and can suppress excessive temperature rise in a specific switch.

- When switching between the first to fourth operations, losses may increase due to specific switching. Specifically, the specific switching may be, for example, switching the switch to be kept on from the upper arm switches 22, 32 to the lower arm switches 23, 33. It is desirable to keep the number of specific switching operations small.

In this respect, in the present embodiment, in the first AC control, the first operation and the second operation are alternately performed, and the switches that are maintained on are limited to the upper arm switches 22 and 32. In the second AC control, the third operation and the fourth operation are alternately performed, and the switches that are maintained on are limited to the lower arm switches 23 and 33. Therefore, during the period in which the first AC control and the second AC control are performed, no specific switching is performed, and the generated loss can be suppressed. In addition, in the present embodiment, when the first and second operations are switched to the third and fourth operations during the first control period, the first AC control is switched to the second AC control. As a result, even in the second AC control after the switch, no specific switching is performed, and the generated loss can be suppressed.

- In this embodiment, when switching between the first AC control and the second AC control during the first control period, the first and second adder circuits 61, 63 switch the value to be added to the voltage command value V*. This allows the AC control of the rotating electric machine 10 to be switched earlier than when switching the control signals SC1, SC2 and the inverted signals SR1, SR2 input to each inverter 20, 30, and allows the first and second inverters 20, 30 to continue to be driven appropriately during the first control period.

Second Embodiment
The second embodiment will be described below with reference to Fig. 10, focusing on the differences from the first embodiment. The present embodiment differs from the first embodiment in that temperatures TD1, TD2 of the lower arm switches 23, 33 in the first and second inverters 20, 30 are further used to determine whether to switch from the first AC control to the second AC control.

Figure 10 shows a flowchart of the switching control process of this embodiment. Note that in Figure 10, the same processes as those shown in Figure 4 above are given the same step numbers for convenience, and the explanation is omitted.

As shown in FIG. 10, in the setting process of this embodiment, if a positive determination is made in step S15, then in step S40, the temperature TD2 of the lower arm switch 33 in the second inverter 30 is acquired. In the following step S41, it is determined whether the temperature TD2 acquired in step S40 is lower than the temperature threshold value Tth. The temperature threshold value Tth is the upper operating temperature limit of the lower arm switches 23, 33. If a positive determination is made in step S41, then the process proceeds to step S16.

If the determination in step S41 is negative, the process proceeds to step S19. That is, if the first capacitor voltage VC1 acquired in step S14 is lower than the first voltage threshold VDth and the temperature TD2 acquired in step S40 is higher than the temperature threshold Tth, the control switches to the second AC control. On the other hand, if the first capacitor voltage VC1 acquired in step S14 is lower than the first voltage threshold VDth but the temperature TD2 acquired in step S40 is higher than the temperature threshold Tth, the control continues with the first AC control without switching to the second AC control.

If the determination in step S17 is affirmative, then in step S42, the temperature TD1 of the lower arm switch 23 in the first inverter 20 is acquired. In the following step S43, it is determined whether the temperature TD1 acquired in step S42 is lower than the temperature threshold value Tth. If the determination in step S43 is affirmative, then the process proceeds to step S18. In this embodiment, the temperatures TD1 and TD2 correspond to "temperature parameters."

If the determination in step S43 is negative, the process proceeds to step S19. That is, if the second capacitor voltage VC2 acquired in step S14 is lower than the first voltage threshold VDth and the temperature TD1 acquired in step S43 is higher than the temperature threshold Tth, the process switches to the second AC control. On the other hand, if the second capacitor voltage VC2 acquired in step S14 is lower than the first voltage threshold VDth but the temperature TD1 acquired in step S42 is higher than the temperature threshold Tth, the process continues with the first AC control without switching to the second AC control.

The present embodiment described above provides the following advantages:

In the third operation, the lower arm switch 33 is maintained on, so the temperature TD2 of the lower arm switch 33 rises. In the fourth operation, the lower arm switch 23 is maintained on, so the temperature TD1 of the lower arm switch 23 rises due to the passage of current. Therefore, if the first AC control is switched to the second AC control even when the temperatures TD1 and TD2 of the lower arm switches 23 and 33 are high, there is a concern that the temperatures TD1 and TD2 of the lower arm switches 23 and 33 will rise excessively during the second AC control.

In this regard, in this embodiment, it is determined whether to switch from the first AC control to the second AC control based on the temperatures TD1, TD2 of the lower arm switches 23, 33 in the first and second inverters 20, 30. If the temperatures TD1, TD2 of the lower arm switches 23, 33 are higher than the temperature threshold value Tth, the first AC control is not switched to the second AC control even if the first and second capacitor voltages VC1, VC2 are lower than the first voltage threshold value VDth. This makes it possible to prevent the temperatures TD1, TD2 of the lower arm switches 23, 33 from rising excessively.

Third Embodiment
The third embodiment will be described below, focusing on the differences from the first embodiment, with reference to Fig. 11. This embodiment differs from the first embodiment in that, in the switching control process, when the first AC control is switched to the second AC control during the first control period, an elapsed time t from the switching to the second AC control is obtained, and the second AC control is switched to the first AC control based on this elapsed time t.

Figure 11 shows a flowchart of the switching control process of this embodiment. Note that in Figure 11, the same processes as those shown in Figure 4 above are given the same step numbers for convenience, and the explanation is omitted.

As shown in FIG. 11, in the setting process of this embodiment, if a positive determination is made in step S12, the elapsed time t is acquired in step S50, and the process proceeds to step S51. The elapsed time t is the time elapsed since the AC control of the rotating electric machine 10 was switched from the first AC control to the second AC control in step S20. In step S51, it is determined whether the elapsed time t acquired in step S50 is longer than the first charging reference period. The first charging reference period is a period for charging the first capacitor voltage VC1 of the first bootstrap capacitor CA1 from the first voltage threshold VDth to the second voltage threshold VUth by the third and fourth operations. In this embodiment, the first charging reference period is set to a constant value in advance.

If the determination in step S51 is positive, the first flag F1 is switched off in step S32, and the process proceeds to step S37. On the other hand, if the determination in step S51 is negative, the second AC control is performed in step S33, and the switching control process ends.

If the determination in step S13 is affirmative, then in step S52, the elapsed time t is acquired, and the process proceeds to step S53. In step S53, it is determined whether the elapsed time t acquired in step S52 is longer than the second charging reference period. The second charging reference period is a period for charging the second capacitor voltage VC2 of the second bootstrap capacitor CA2 from the first voltage threshold VDth to the second voltage threshold VUth by the third and fourth operations. In this embodiment, the second charging reference period is set to a constant value in advance. Note that the second charging reference period may be equal to or different from the first charging reference period. In this embodiment, the processes in steps S50 and S52 correspond to an "elapsed time acquisition unit."

If the determination in step S53 is positive, the second flag F2 is switched off in step S36, and the process proceeds to step S37. On the other hand, if the determination in step S53 is negative, the second AC control is performed in step S33, and the switching control process ends.

According to the present embodiment described above in detail, when the first AC control is switched to the second AC control during the first control period, the elapsed time t of the second AC control is acquired. Then, when this elapsed time t is longer than the first and second charging reference periods, the second AC control is switched to the first AC control. As a result, in the second AC control after switching, it is not necessary to acquire the first capacitor voltage VC1 of the first bootstrap capacitor CA1 or the second capacitor voltage VC2 of the second bootstrap capacitor CA2, and the processing required to switch from the second AC control to the first AC control can be simplified.

Fourth Embodiment
The fourth embodiment will be described below with reference to Figures 12 and 13, focusing on the differences from the third embodiment. The present embodiment differs from the third embodiment in that the first and second charge reference periods are set based on temperatures TD1 and TD2 of the lower arm switches 23 and 33 in the first and second inverters 20 and 30.

Figure 12 shows a flowchart of the switching control process of this embodiment. Note that in Figure 12, the same processes as those shown in Figure 11 above are given the same step numbers for convenience, and descriptions are omitted.

As shown in FIG. 12, in the setting process of this embodiment, the elapsed time t is acquired in step S50, and then the temperature TD2 of the lower arm switch 33 in the second inverter 30 is acquired in step S60. In the following step S61, the first charging reference period is set based on the temperature TD2 acquired in step S60 and the first map MP1, and the process proceeds to step S51.

The first map MP1 is correlation information that associates the temperature TD2 in a predetermined temperature range with the first charging reference period. The first map MP1 is stored in a memory unit 70 (see FIG. 1) provided in the control device 50. As shown in FIG. 13, the first map MP1 is set so that the higher the temperature TD2, the shorter the first charging reference period. Therefore, when the temperature TD2 is high, the operating period of the third operation is shortened, and the rise in temperature TD2 is suppressed.

Furthermore, once the elapsed time t is acquired in step S52, the temperature TD1 of the lower arm switch 23 in the first inverter 20 is acquired in step S62. In the following step S63, a second charging reference period is set based on the temperature TD1 acquired in step S62 and the second map MP2, and the process proceeds to step S53.

The second map MP2 is correlation information that associates the temperature TD1 in a predetermined temperature range with the second charging reference period, and is stored in the memory unit 70. The second map MP2 may be equal to or different from the first map MP1. As shown in FIG. 13, the second map MP2 is set so that the higher the temperature TD1, the shorter the second charging reference period. Therefore, when the temperature TD1 is high, the operating period of the fourth operation is shortened, and the rise in temperature TD1 is suppressed.

The reference charging period in each map MP1, MP2 is set taking into consideration the temperature characteristics of the corresponding lower arm switch 23, 33. In this embodiment, a MOSFET is used as the lower arm switch 23, 33, and the drop voltage between the main terminals of the MOSFET has a positive temperature characteristic. In this embodiment, the reference charging period in each map MP1, MP2 is adjusted based on the positive temperature characteristic of the MOSFET.

The present embodiment described above provides the following advantages:

In the third operation, the lower arm switch 33 is maintained on, and the temperature TD2 of the lower arm switch 33 rises due to the passage of current. In the fourth operation, the lower arm switch 23 is maintained on, and the temperature TD1 of the lower arm switch 23 rises due to the passage of current. Therefore, when the first AC control is switched to the second AC control during the first control period, if the second AC control is performed over the predetermined first and second reference charging periods despite the temperatures TD1 and TD2 of the lower arm switches 23 and 33 being high, there is a concern that the temperatures TD1 and TD2 of the lower arm switches 23 and 33 will rise excessively during the first and second reference charging periods.

In this regard, in this embodiment, a first map MP1 in which temperature TD1 corresponds to the first charging reference period and a second map MP2 in which temperature TD2 corresponds to the second charging reference period are stored in the memory unit 70 of the control device 50. When the temperatures TD1, TD2 of the lower arm switches 23, 33 acquired during the period in which the second AC control is being performed are high, the first and second charging reference periods are set to be shorter based on the first and second maps MP1, MP2. This makes it possible to prevent the temperatures TD1, TD2 of the lower arm switches 23, 33 from rising excessively during the first and second charging reference periods.

Other Embodiments
The present invention is not limited to the above-described embodiment, and may be implemented as follows.

The rotating electric machine 10 is not limited to a three-phase machine, but may be a two-phase machine or a four-phase machine or more. The first inverter 20 and the second inverter 30 may be inverters having a series connection of upper and lower arm switches equal to the number of phases of the rotating electric machine 10.

- The switches provided in the first inverter 20 and the second inverter 30 are not limited to MOSFETs, but may be, for example, IGBTs. When the switches are IGBTs, freewheeling diodes are used as diodes reverse-connected to the switches. In addition, since the drop voltage between the main terminals of an IGBT has negative temperature characteristics, the charging reference period may be adjusted based on the negative temperature characteristics of the IGBT.

- In the above embodiment, an example was shown in which the first AC control and the second AC control were alternately switched between at each predetermined control period, but of the first AC control and the second AC control, the first AC control may be performed as a rule. In this case, the second AC control may be performed as an exception on the condition that the first and second capacitor voltages VC1 and VC2 of the first and second bootstrap capacitors CA1 and CA2 become lower than the first voltage threshold VDth in the first AC control. In this case, by setting the second control period based on the first control period until switching to the second AC control, the operation periods of the first and second operations and the operation periods of the third and fourth operations can be set in a balanced manner, and an excessive rise in temperature in a specific switch can be suppressed.

- In the above embodiment, the first and second capacitor voltages VC1, VC2 of the first and second bootstrap capacitors CA1, CA2 are acquired, and the first AC control is switched to the second AC control based on the acquired results. However, the manner of switching between the first AC control and the second AC control is not limited to this. For example, if the period until the first and second capacitor voltages VC1, VC2 become lower than the first voltage threshold VDth can be calculated in advance based on the operating period of the rotating electric machine 10 and the drop voltages of the switches 22, 23, 32, 33, etc., the first AC control may be switched to the second AC control based on that period.

The temperature of the switches of each inverter 20, 30 is not limited to the detection value of a temperature sensor, and may be, for example, an estimated temperature value of the switch. The estimated temperature value may be calculated based on the detection value of the current flowing through each switch, or the temperature of an element present near the switch, such as a body diode, may be detected and the switch temperature may be estimated based on that temperature.

- The rotating electric machine 10 is not limited to applications in vehicles, but may also be used in ships, aircraft, etc.

The control device and the method thereof 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 device and the method thereof 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 device and the method thereof 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... rotating electric machine, 11... winding, 20... first inverter, 22... upper arm switch, 23... lower arm switch, 26... first drive circuit, 30... second inverter, 32... upper arm switch, 33... lower arm switch, 36... second drive circuit, 50... control device, 100... rotating electric machine system, LE... high potential side connection line, LG... low potential side connection line.

Claims (13)

A rotating electric machine (10) having a multi-phase winding (11);
a first inverter (20) having an upper arm switch (22) and a lower arm switch (23) connected in series for each phase, the connection point between the upper arm switch and the lower arm switch being connected to a first end of both ends of the winding for each phase;
a second inverter (30) having an upper arm switch (32) and a lower arm switch (33) connected in series for each phase, the connection point between the upper arm switch and the lower arm switch being connected to a second end of both ends of the winding for each phase;
A high potential side connection line (LE) connecting the high potential side of the first inverter and the high potential side of the second inverter;
a low potential side connection line (LG) connecting the low potential side of the first inverter and the low potential side of the second inverter;
A control device (50) for a rotating electric machine applied to a rotating electric machine system (100) comprising:
The rotating electric machine system includes:
a first bootstrap circuit (26) having a first bootstrap capacitor for generating a voltage for turning on an upper arm switch of the first inverter;
a second bootstrap circuit (36) having a second bootstrap capacitor that generates a voltage for turning on an upper arm switch of the second inverter;
an upper-arm on fixing operation in which, in one of the first inverter and the second inverter, an upper-arm switch is kept on and a lower-arm switch is kept off, and in the other inverter, switching driving of the upper and lower arm switches is performed;
a control unit that switches between a lower arm on fixing operation in which the upper arm switch is kept off and the lower arm switch is kept on in the other inverter;
a voltage acquisition unit that acquires a voltage of one of the first bootstrap capacitor and the second bootstrap capacitor that corresponds to the one of the inverters,
The control unit switches the upper arm fixed on operation to the lower arm fixed on operation when the voltage of the bootstrap capacitor acquired during the upper arm fixed on operation is lower than a voltage threshold. The upper arm on fixing operation is
a first operation of maintaining an upper arm switch on and a lower arm switch off in the second inverter, and performing switching driving of the upper and lower arm switches in the first inverter;
a second operation of maintaining the upper arm switch on and the lower arm switch off in the first inverter, and performing switching driving of the upper and lower arm switches in the second inverter;
The lower arm on fixing operation is
a third operation of performing switching driving of upper and lower arm switches in the first inverter, and maintaining the upper arm switches off and the lower arm switches on in the second inverter;
a fourth operation of switching and driving upper and lower arm switches in the second inverter, and maintaining the upper arm switches off and the lower arm switches on in the first inverter;
The control unit switches between the first operation, the second operation, the third operation, and the fourth operation,
the voltage acquisition unit acquires a voltage of the first bootstrap capacitor included in the first bootstrap circuit;
The control device for a rotating electric machine according to claim 1 , wherein the control unit switches from the second operation to the third operation when a voltage of the first bootstrap capacitor acquired during the second operation is lower than the voltage threshold value. The control unit is
acquiring a temperature parameter which is either a temperature of a lower arm switch in the second inverter or a parameter correlated with the temperature;
3. The control device for a rotating electric machine according to claim 2, wherein, during the second operation, the second operation is switched to the third operation on condition that the acquired voltage of the first bootstrap capacitor is lower than the voltage threshold and the temperature indicated by the acquired temperature parameter is lower than a temperature threshold. the voltage threshold is a first voltage threshold;
4. The control device for a rotating electric machine according to claim 2, wherein after switching from the second operation to the third operation, the control unit switches from the third operation to the second operation when a voltage of the first bootstrap capacitor acquired during the third operation is higher than a second voltage threshold that is set higher than the first voltage threshold. an elapsed time acquisition unit that acquires an elapsed time since the third operation is switched to,
The control device for a rotating electric machine according to claim 2 , wherein the control unit switches from the third operation to the second operation when the acquired elapsed time is longer than a reference charging period. a storage unit (70) in which correlation information is stored in which a temperature parameter, which is either a temperature of a lower arm switch in the second inverter or a parameter correlated with the temperature, corresponds to the charging reference period;
The control unit is
Obtaining a temperature parameter of a lower arm switch of the second inverter;
setting the charging reference period based on a temperature parameter acquired during the second operation and the correlation information;
6. The control device for a rotating electric machine according to claim 5, wherein the correlation information is information in which the charging reference period is set shorter when the temperature indicated by the temperature parameter is high than when the temperature indicated by the temperature parameter is low. The upper arm on fixing operation is
a first operation of maintaining an upper arm switch on and a lower arm switch off in the second inverter, and performing switching driving of the upper and lower arm switches in the first inverter;
a second operation of maintaining the upper arm switch on and the lower arm switch off in the first inverter, and performing switching driving of the upper and lower arm switches in the second inverter;
The lower arm on fixing operation is
a third operation of performing switching driving of upper and lower arm switches in the first inverter, and maintaining the upper arm switches off and the lower arm switches on in the second inverter;
a fourth operation of switching and driving upper and lower arm switches in the second inverter, and maintaining the upper arm switches off and the lower arm switches on in the first inverter;
The control unit switches between the first operation, the second operation, the third operation, and the fourth operation,
the voltage acquisition unit acquires a voltage of the second bootstrap capacitor included in the second bootstrap circuit;
The control device for a rotating electric machine according to claim 1 , wherein the control unit switches from the first operation to the fourth operation when a voltage of the second bootstrap capacitor acquired during the first operation is lower than the voltage threshold value. The control unit is
acquiring a temperature parameter which is either a temperature of a lower arm switch in the first inverter or a parameter correlated with the temperature;
8. The control device for a rotating electric machine according to claim 7, wherein, during the first operation, the first operation is switched to the fourth operation on condition that the acquired voltage of the second bootstrap capacitor is lower than the voltage threshold and the temperature indicated by the acquired temperature parameter is lower than a temperature threshold. the voltage threshold is a first voltage threshold;
9. The control device for a rotating electric machine according to claim 7 or 8, wherein, after switching the first operation to the fourth operation, the control unit switches the fourth operation to the first operation when a voltage of the second bootstrap capacitor acquired during the fourth operation is higher than a second voltage threshold that is set higher than the first voltage threshold. an elapsed time acquisition unit that acquires an elapsed time since the fourth operation is switched to,
The control device for a rotating electric machine according to claim 7 , wherein the control unit switches from the fourth operation to the first operation when the acquired elapsed time is longer than a reference charging period. a storage unit (70) in which correlation information is stored in which a temperature parameter, which is either a temperature of a lower arm switch in the first inverter or a parameter correlated with the temperature, corresponds to the charging reference period;
The control unit is
Obtaining a temperature parameter of a lower arm switch in the first inverter;
setting the charging reference period based on a temperature parameter acquired during the first operation and the correlation information;
The control device for a rotating electric machine according to claim 10 , wherein the correlation information is information in which the charging reference period is set shorter when the temperature indicated by the temperature parameter is high than when the temperature indicated by the temperature parameter is low. A rotating electric machine (10) having a multi-phase winding (11);
a first inverter (20) having an upper arm switch (22) and a lower arm switch (23) connected in series for each phase, the connection point between the upper arm switch and the lower arm switch being connected to a first end of both ends of the winding of each phase;
a second inverter (30) having an upper arm switch (32) and a lower arm switch (33) connected in series for each phase, the connection point between the upper arm switch and the lower arm switch being connected to a second end of both ends of the winding for each phase;
A high potential side connection line (LE) connecting the high potential side of the first inverter and the high potential side of the second inverter;
a low potential side connection line (LG) connecting the low potential side of the first inverter and the low potential side of the second inverter;
A program applied to a rotating electric machine system (100) comprising:
The rotating electric machine system includes:
a first bootstrap circuit (26) having a first bootstrap capacitor for generating a voltage for turning on an upper arm switch of the first inverter;
a second bootstrap circuit (36) having a second bootstrap capacitor that generates a voltage for turning on an upper arm switch of the second inverter;
On the computer,
an upper-arm on fixing operation in which, in one of the first inverter and the second inverter, an upper-arm switch is kept on and a lower-arm switch is kept off, and in the other inverter, switching driving of the upper and lower arm switches is performed;
a control process in which, in one inverter, switching drive of upper and lower arm switches is performed, and, in the other inverter, a lower arm on fixing operation is performed in which the upper arm switch is kept off and the lower arm switch is kept on;
a voltage acquisition process of acquiring a voltage of one of the first bootstrap capacitor and the second bootstrap capacitor corresponding to the one inverter;
a program for switching, in the control processing, from the upper arm on fixing operation to the lower arm on fixing operation when the voltage of the bootstrap capacitor acquired during the upper arm on fixing operation is lower than a voltage threshold value. A rotating electric machine (10) having a multi-phase winding (11);
a first inverter (20) having an upper arm switch (22) and a lower arm switch (23) connected in series for each phase, the connection point between the upper arm switch and the lower arm switch being connected to a first end of both ends of the winding for each phase;
a second inverter (30) having an upper arm switch (32) and a lower arm switch (33) connected in series for each phase, the connection point between the upper arm switch and the lower arm switch being connected to a second end of both ends of the winding for each phase;
A high potential side connection line (LE) connecting the high potential side of the first inverter and the high potential side of the second inverter;
a low potential side connection line (LG) connecting the low potential side of the first inverter and the low potential side of the second inverter;
A method for controlling a rotating electric machine applied to a rotating electric machine system (100) comprising:
The rotating electric machine system includes:
a first bootstrap circuit (26) having a first bootstrap capacitor for generating a voltage for turning on an upper arm switch of the first inverter;
a second bootstrap circuit (36) having a second bootstrap capacitor that generates a voltage for turning on an upper arm switch of the second inverter;
an upper-arm on fixing operation in which, in one of the first inverter and the second inverter, an upper-arm switch is kept on and a lower-arm switch is kept off, and in the other inverter, switching driving of the upper and lower arm switches is performed;
a control step of switching between driving the upper and lower arm switches in the one inverter and a lower arm on fixing operation in the other inverter, in which the upper arm switch is kept off and the lower arm switch is kept on;
a voltage acquiring step of acquiring a voltage of one of the first bootstrap capacitor and the second bootstrap capacitor corresponding to the one inverter,
a control step of switching the upper arm fixed on operation to the lower arm fixed on operation when the voltage of the bootstrap capacitor acquired during the upper arm fixed on operation is lower than a voltage threshold value.

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