3-level inverter and program

Abstract

To provide a three-level inverter and a program that can reduce unbalance in recovery current.SOLUTION: The three-level inverter includes: a high potential side conductive member that electrically connects respective upper arm switches SUH1 to SWH2 and a positive electrode side bus bar 31; a low potential side conductive member that electrically connects respective lower arm switches SUL1 to SWL2 and a negative electrode side bus bar 32; and an intermediate conductive member. The intermediate conductive member electrically connects the respective upper arm switches SUH1 to SWH2, the respective lower arm switches SUL1 to SWL2, and middle switches SQU1 to SQW2. Each upper arm path is configured such that impedance of an electric path from a connection point of the high potential side conductive member with the positive electrode side bus bar to the middle switches SQU1 to SQW2 via upper arm diodes DUH1 to DWH2 and the intermediate conductive member, which is an upper arm path corresponding to each of the upper arm diodes DUH1 to DWH2, is equivalent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a three-level inverter and a program. [Background technology]

[0002] Conventionally, as described in Patent Document 1, an inverter including two semiconductor switches (specifically, IGBTs) connected in parallel has been known. Specifically, this inverter includes a gate drive circuit for driving the two switches, a comparator, an AND circuit, and a transformer. When the two switches are driven by the gate drive circuit, the differential value of the collector current flowing through the switch with a higher temperature is detected by the comparator, and the primary winding of the transformer is driven via the AND circuit. As a result, an induced voltage is generated in the secondary winding, which is a winding constituting the transformer and connected between the gates of the two switches, and the gate voltage of the switch with a higher temperature increases. As a result, the imbalance of the collector currents flowing through the two switches is suppressed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-15910 Summary of the Invention [Problem to be solved by the invention]

[0004] A three-level inverter is also known as an inverter. The three-level inverter includes a plurality of series-connected units of upper and lower arm switches in each phase, and the series-connected units are connected in parallel in each phase. The three-level inverter includes upper arm diodes connected in anti-parallel to each upper arm switch, lower arm diodes connected in anti-parallel to each lower arm switch, and middle switches provided corresponding to each phase.

[0005] In each phase and arm of a three-level inverter, an imbalance in the recovery current flowing through each diode can occur. Therefore, a configuration that can suppress the imbalance in the recovery current is desired.

[0006] A main object of the present invention is to provide a three-level inverter and a program that can suppress the imbalance of recovery currents. [Means for solving the problem]

[0007] The present invention provides a three-level inverter having a plurality of series-connected bodies of upper and lower arm switches in each phase, and the series-connected bodies in each phase are connected in parallel, an upper arm diode connected in anti-parallel to each of the upper arm switches; a lower arm diode connected in anti-parallel to each of the lower arm switches; A middle switch provided corresponding to each phase; a high-potential side conductive member provided corresponding to each phase and electrically connecting a high-potential side terminal of each upper arm switch to a positive side bus; a low-potential side conductive member provided corresponding to each phase and electrically connecting a low-potential side terminal of each lower arm switch to a negative-pole side bus; an intermediate conductive member provided corresponding to each phase, electrically connecting a low potential side terminal of each of the upper arm switches and a high potential side terminal of each of the lower arm switches to a first end of the middle switch; Equipped with an electrical path extending from a connection portion of the high potential side conductive member with the positive side bus bar to the middle switch via the upper arm diodes and the intermediate conductive member, the upper arm paths being configured such that impedances of the upper arm paths corresponding to the upper arm diodes are equal to each other; An electrical path extends from the connection point of the low potential side conductive member with the negative side busbar through the lower arm diodes and the intermediate conductive member to the middle switch, and each lower arm path is configured so that the impedance of the lower arm path corresponding to each lower arm diode is equivalent.

[0008] According to the present invention, in which the impedances of the upper arm paths are configured to be equal and the impedances of the lower arm paths are configured to be equal, the imbalance in recovery current can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an overall configuration diagram of a control system according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing the electrical connections of a U-phase circuit. [Figure 3] FIG. [Figure 4] FIG. 1 is a plan view of each module. [Figure 5] 1 is a diagram showing switching modes. [Figure 6] FIG. 10 is a diagram showing an unbalanced state of recovery current. [Figure 7] FIG. 10 is a diagram showing an unbalanced state of recovery current. [Figure 8] 4 is a time chart showing an example of gate voltage oscillation suppression control. [Figure 9] FIG. 4 is a diagram showing a current flow state during oscillation suppression control. [Figure 10] FIG. 4 is a diagram showing a current flow state during oscillation suppression control. [Figure 11] FIG. 4 is a diagram showing a current flow state during oscillation suppression control. [Figure 12] FIG. 4 is a diagram showing a current flow state during oscillation suppression control. [Figure 13] FIG. 4 is a diagram showing a current flow state during oscillation suppression control. [Figure 14] FIG. 4 is a diagram showing a current flow state during oscillation suppression control. [Figure 15] FIG. 4 is a diagram showing a current flow state during oscillation suppression control. [Figure 16] 5 is a time chart showing switching control of an inverter according to a comparative example. [Figure 17] FIG. 10 is a diagram showing a current flow state according to a comparative example. [Figure 18]FIG. 10 is a diagram showing a current flow state according to a comparative example. [Figure 19] FIG. 10 is a diagram showing a current flow state according to a comparative example. [Figure 20] FIG. 10 is a diagram showing a current flow state according to a comparative example. [Figure 21] 10 is a flowchart showing a procedure for controlling gate voltage oscillation suppression. [Figure 22] 10 is a flowchart showing a procedure for gate voltage oscillation suppression control according to the second embodiment. [Figure 23] FIG. 11 is a diagram showing electrical connections of a U-phase circuit according to a third embodiment. [Figure 24] 10 is a flowchart showing a procedure for controlling gate voltage oscillation suppression. DETAILED DESCRIPTION OF THE INVENTION

[0010] Several embodiments will be described with reference to the drawings. In several embodiments, functionally and / or structurally corresponding and / or associated parts may be assigned the same reference numerals or reference numerals that differ in the hundredth or higher digit. For corresponding and / or associated parts, reference may be made to the descriptions of other embodiments.

[0011] First Embodiment A first embodiment of a three-level inverter according to the present invention will be described below with reference to the drawings. In this embodiment, a control system including a three-level inverter is installed in an electrically powered vehicle such as an electric vehicle or a hybrid vehicle.

[0012] As shown in FIG. 1, the control system includes a rotating electric machine 10, a storage battery 20 which is a DC power supply, and an inverter 30. The rotating electric machine 10 is an on-vehicle main engine and includes a rotor (not shown). Power can be transmitted between the rotor and the drive wheels of the vehicle. The rotating electric machine 10 of this embodiment is a three-phase synchronous machine and includes a star-connected U-phase winding 11U, a V-phase winding 11V, and a W-phase winding 11W as stator windings. The phase windings 11U, 11V, and 11W are arranged with an offset of 120° in electrical angle. The rotating electric machine 10 is, for example, a permanent magnet synchronous machine.

[0013] The storage battery 20 is electrically connected to the respective phase windings 11U, 11V, and 11W of the rotating electrical machine 10 via an inverter 30. The storage battery 20 is, for example, a battery pack including a series connection of battery cells. The storage battery 20 is, for example, a rechargeable secondary battery such as a lithium ion battery.

[0014] The inverter 30 converts DC power supplied from the storage battery 20 into three-phase AC power using switching control, and supplies the converted AC power to the respective phase windings 11U, 11V, and 11W. The inverter 30 is a three-level inverter and includes a first capacitor 21 and a second capacitor 22. The first capacitor 21 and the second capacitor 22 are connected in series. The storage battery 20 is connected in parallel to the series connection of the first and second capacitors 21 and 22. In this embodiment, the capacitance of the first capacitor 21 and the capacitance of the second capacitor 22 are set to the same value.

[0015] The inverter 30 includes upper and lower arm switches for three phases. In this embodiment, each arm switch is configured with a parallel connection of multiple semiconductor switching elements, specifically, a parallel connection of two semiconductor switching elements. The semiconductor switching elements in this embodiment are IGBTs.

[0016] U-phase first and second upper-arm switches SUH1 and SUH2 and U-phase first and second lower-arm switches SUL1 and SUL2 are provided as U-phase upper and lower-arm switches. U-phase first and second upper-arm diodes DUH1 and DUH2, which are freewheel diodes, are connected in anti-parallel to the U-phase first and second upper-arm switches SUH1 and SUH2. U-phase first and second lower-arm diodes DUL1 and DUL2 are connected in anti-parallel to the U-phase first and second lower-arm switches SUL1 and SUL2.

[0017] The V-phase upper and lower arm switches include V-phase first and second upper arm switches SVH1 and SVH2 and V-phase first and second lower arm switches SVL1 and SVL2. V-phase first and second upper arm diodes DVH1 and DVH2 are connected in anti-parallel to the V-phase first and second upper arm switches SVH1 and SVH2. V-phase first and second lower arm diodes DVL1 and DVL2 are connected in anti-parallel to the V-phase first and second lower arm switches SVL1 and SVL2.

[0018] The W-phase upper and lower arm switches include W-phase first and second upper arm switches SWH1 and SWH2 and W-phase first and second lower arm switches SWL1 and SWL2. W-phase first and second upper arm diodes DWH1 and DWH2 are connected in anti-parallel to the W-phase first and second upper arm switches SWH1 and SWH2. W-phase first and second lower arm diodes DWL1 and DWL2 are connected in anti-parallel to the W-phase first and second lower arm switches SWL1 and SWL2.

[0019] The electrical connections between the inverter 30, the storage battery 20, and the rotating electrical machine 10 will be described using the U-phase as an example. A positive bus 31, which is a conductive member such as a bus bar, is connected to the collectors, which are the high-potential side terminals, of the U-phase first and second upper arm switches SUH1 and SUH2. The positive bus 31 is connected to the positive terminal of the storage battery 20 and a first end of the first capacitor 21. A second end of the first capacitor 21 is connected to a first end of the second capacitor 22. A negative bus 32, which is a conductive member such as a bus bar, is connected to the emitters, which are the low-potential side terminals, of the U-phase first and second lower arm switches SUL1 and SUL2. The negative bus 32 is connected to the negative terminal of the storage battery 20 and a second end of the second capacitor 22.

[0020] A first end of a U-phase winding 11U is connected to the emitters of the U-phase first and second upper arm switches SUH1, SUH2 and the collectors of the U-phase first and second lower arm switches SUL1, SUL2. Second ends of the phase windings 11U, 11V, 11W are connected to each other at the neutral point.

[0021] The inverter 30 includes three-phase middle switches that conduct and cut off current in both directions. In this embodiment, each middle switch is made up of two semiconductor switching elements, and the semiconductor switching elements are IGBTs.

[0022] U-phase first and second switches SQU1 and SQU2 are provided as U-phase middle switches. U-phase first and second diodes DQU1 and DQU2, which are freewheel diodes, are connected in anti-parallel to the U-phase first and second switches SQU1 and SQU2. V-phase first and second switches SQV1 and SQV2 are provided as V-phase middle switches. V-phase first and second diodes DQV1 and DQV2 are connected in anti-parallel to the V-phase first and second switches SQV1 and SQV2. W-phase first and second switches SQW1 and SQW2 are provided as W-phase middle switches. W-phase first and second diodes DQW1 and DQW2 are connected in anti-parallel to the W-phase first and second switches SQW1 and SQW2.

[0023] To explain the electrical connections of the middle switches using the U phase as an example, the emitters of the U-phase first and second switches SQU1 and SQU2 are connected to each other. The collector of the U-phase first switch SQU1 is connected to a second end of the first capacitor 21 and a second end of the second capacitor 22. The emitter of the U-phase second switch SQU2 is connected to the emitters of the U-phase first and second upper arm switches SUH1 and SUH2 and the collectors of the U-phase first and second lower arm switches SUL1 and SUL2.

[0024] The control system includes a current sensor 40 and a rotation angle sensor 41. The current sensor 40 detects the phase currents flowing through the phase windings 11U, 11V, and 11W. The rotation angle sensor 41 is, for example, a resolver, and detects the rotation angle (specifically, the electrical angle) of the rotating electric machine 10. The detection values ​​of the sensors 40 and 41 are input to a control device 50 included in the control system.

[0025] The control device 50 is mainly composed of a microcomputer 51, which includes a CPU. The functions provided by the microcomputer 51 can be provided by software recorded in a physical memory device and a computer executing the software, by software alone, by hardware alone, or a combination thereof. For example, if the microcomputer 51 is provided by a hardware electronic circuit, the function can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcomputer 51 executes a program stored in a non-transitory tangible storage medium serving as a storage unit of the microcomputer 51. The program includes, for example, a program for processing shown in FIG. 21 (described later). Execution of a program installed in the control device 50 executes a method corresponding to the program. The storage unit is, for example, a non-volatile memory. Note that the program stored in the storage unit can be downloaded and updated via a communication network such as the Internet, for example, via OTA (Over The Air) or the like.

[0026] The control device 50 generates drive signals for the switches SUH1-SWL2, SQU1-SQW2 of the inverter 30 so as to control the control variable of the rotating electrical machine 10 to a command value. The drive signals consist of an ON command and an OFF command. The control device 50 turns on and off the switches SUH1-SWL2, SQU1-SQW2 based on the generated drive signals. In this embodiment, the control variable is torque, and the command value is a command torque Trq*.

[0027] In this embodiment, the inverter 30 is configured with a switch module. Hereinafter, the U phase will be described as an example with reference to Figs.

[0028] The circuit constituting the U phase of the inverter 30 is composed of three switch modules, specifically, first and second modules M1 and M2 (corresponding to "upper and lower arm modules") and an intermediate module MM. Each of the modules M1, M2, and MM has a case 60, which houses semiconductor switching elements and freewheel diodes. The case 60 has a flat rectangular parallelepiped shape. In this embodiment, the cases 60 of the modules M1, M2, and MM have the same shape.

[0029] The case 60 of the first module M1 accommodates a U-phase first upper arm switch SUH1, a U-phase first upper arm diode DUH1, a U-phase first lower arm switch SUL1, and a U-phase first lower arm diode DUL1. The collector of the U-phase first upper arm switch SUH1 is connected to a high-potential side external terminal CP provided in the case 60 of the first module M1. The emitter of the U-phase first lower arm switch SUL1 is connected to a low-potential side external terminal CN provided in the case 60 of the first module M1. The emitter of the U-phase first upper arm switch SUH1 and the collector of the U-phase first lower arm switch SUL1 are connected to an intermediate external terminal CO provided in the case 60 of the first module M1.

[0030] The case 60 of the second module M2 accommodates a U-phase second upper-arm switch SUH2, a U-phase second upper-arm diode DUH2, a U-phase second lower-arm switch SUL2, and a U-phase second lower-arm diode DUL2. In this embodiment, the second module M2 and the first module M1 have the same configuration. Therefore, a detailed description of the interior of the second module M2 will be omitted.

[0031] In this embodiment, the first and second modules M1 and M2 have the same specifications. Therefore, the internal configuration of the first module M1 and the internal configuration of the second module M2 are the same. Specifically, the specifications of the switches SUH1, SUL1, SUH2, and SUL2 housed in the first and second modules M1 and M2 are the same, and the specifications of the diodes DUH1, DUL1, DUH2, and DUL2 are also the same. Therefore, the threshold voltages Vth of the switches SUH1, SUL1, SUH2, and SUL2 are designed to be the same, and the rated currents of the switches SUH1, SUL1, SUH2, and SUL2 are designed to be the same. Furthermore, the reverse recovery times of the diodes DUH1, DUL1, DUH2, and DUL2 are designed to be the same, and the on-resistances of the diodes DUH1, DUL1, DUH2, and DUL2 are also designed to be the same.

[0032] The case 60 of the intermediate module MM accommodates U-phase first and second switches SQU1 and SQU2 and U-phase first and second diodes DQU1 and DQU2. The collector of the U-phase first switch SQU1 is connected to a neutral terminal CM2 provided in the case 60 of the intermediate module MM. The collector of the U-phase second switch SQU2 is connected to an intermediate terminal CM1 provided in the case 60 of the intermediate module MM.

[0033] As shown in Figures 3 and 4, the case 60 of each module M1, M2, MM has a pair of main boards 61 facing each other in the thickness direction (X direction) and a terminal mounting surface 62 connecting the ends of each main board 61. The modules M1, M2, MM are arranged side by side in the thickness direction with their main boards 61 facing each other. The terminal mounting surfaces 62 of each module M1, M2, MM face a common specific direction (Z direction) perpendicular to the X direction. The middle module MM is sandwiched between the first module M1 and the second module M2.

[0034] In the first and second modules M1 and M2, a high-potential side external terminal CP, a low-potential side external terminal CN, and an intermediate external terminal CO are arranged side by side in the Y direction, which is perpendicular to the X and Z directions, on the terminal installation surface 62 of the case 60. In the intermediate module MM, a neutral terminal CM2 and an intermediate terminal CM1 are arranged side by side in the Y direction on the terminal installation surface 62 of the case 60. In each of the modules M1, M2, and MM, the high-potential side external terminal CP and the neutral terminal CM2 are arranged side by side in the X direction, and the intermediate external terminal CO and the intermediate terminal CM1 are also arranged side by side in the X direction. Furthermore, in the first and second modules M1 and M2, the low-potential side external terminals CN are arranged side by side in the X direction.

[0035] As shown in FIGS. 2 and 4, the high-potential-side external terminal CP of the first module M1 and the high-potential-side external terminal CP of the second module M2 are connected by a high-potential-side bus bar 72 (corresponding to a "high-potential-side conductive member"). As shown in FIG. 4, the high-potential-side bus bar 72 has a shape symmetrical with respect to a reference axis BL passing through the center of the case 60 of the intermediate module MM in the thickness direction when viewed from the front of the terminal installation surface 62. More specifically, the high-potential-side bus bar 72 has two terminal connection portions 72a, a first connection portion 72b, and a second connection portion 72c. When viewed from the front of the terminal installation surface 62, the first connection portion 72b extends in the X direction. The terminal connection portion 72a extends in the Y direction from both longitudinal ends of the first connection portion 72b. One of the two terminal connection portions 72a is connected to the high-potential-side external terminal CP of the first module M1, and the other is connected to the high-potential-side external terminal CP of the second module M2. The second connection portion 72c extends from the longitudinal center of the first connection portion 72b in the opposite direction to the direction in which the terminal connection portion 72a extends relative to the first connection portion 72b. The second connection portion 72c is connected to the positive bus 31.

[0036] The high-potential side external terminals CP of the first and second modules M1, M2 and the intermediate terminal CM1 of the intermediate module MM are connected by an intermediate bus bar 70 (corresponding to an "intermediate conductive member"). As shown in FIG. 4, the intermediate bus bar 70 has a shape symmetrical with respect to the reference axis line BL when viewed from the front of the terminal installation surface 62. More specifically, the intermediate bus bar 70 has a first connection portion 70a and a second connection portion 70b. The first connection portion 70a extends in the X direction. The second connection portion 70b extends from the longitudinal center of the first connection portion 70a in the opposite direction to the high-potential side bus bar 72 in the Y direction. The second connection portion 70b is connected to the neutral terminal CM2 of the intermediate module MM and a first end of the winding of the rotating electric machine 10.

[0037] The symmetrical structure of the high-potential side bus bar 72, the identical specifications of the first and second modules M1, M2, and the symmetrical structure of the intermediate bus bar 70 contribute to equalizing the impedances of the first and second upper arm paths. The first upper arm path is an electrical path that runs from the second connection portion 72c via the first connection portion 72b, the high-potential side external terminal CP of the first module M1, the U-phase first upper-arm diode DUH1, the intermediate external terminal CO of the first module M1, the first connection portion 70a, and the second connection portion 70b to the intermediate terminal CM1 of the intermediate module MM, and is an electrical path that corresponds to the U-phase first upper-arm diode DUH1. The second upper arm path is an electrical path that extends from the second connection part 72c through the first connection part 72b, the high potential side external terminal CP of the second module M2, the U-phase second upper arm diode DUH2, the intermediate external terminal CO of the second module M2, the first connection part 70a, and the second connection part 70b to the intermediate terminal CM1 of the intermediate module MM, and corresponds to the U-phase second upper arm diode DUH2. Note that the impedances of the first and second upper arm paths are equivalent when, for example, the difference between the impedances of the first and second upper arm paths is within 20% of the larger impedance of the first and second upper arm paths, preferably when the difference is within 15% of the larger impedance of the first and second upper arm paths, and more preferably when the difference is within 5% of the larger impedance of the first and second upper arm paths.

[0038] The low potential side external terminal CN of the first module M1 and the low potential side external terminal CN of the second module M2 are connected by a low potential side bus bar 71 (corresponding to a "low potential side conductive member"). As shown in FIG. 4, the low potential side bus bar 71 has a shape symmetrical with respect to the reference axis line BL when viewed from the front of the terminal installation surface 62, and extends in the X direction. The center portion of the low potential side bus bar 71 in the X direction is connected to the negative side bus bar 32.

[0039] The symmetrical structure of the low-potential side busbar 71, the identical specifications of the first and second modules M1, M2, and the symmetrical structure of the intermediate busbar 70 contribute to equalizing the impedances of the first and second lower arm paths. The first lower arm path is an electrical path that runs from the center of the low-potential side busbar 71 in the X direction to the intermediate terminal CM1 of the intermediate module MM, via the low-potential side external terminal CN of the first module M1, the U-phase first lower arm diode DUL1, the intermediate external terminal CO of the first module M1, the first connecting portion 70a, and the second connecting portion 70b, and corresponds to the U-phase first lower arm diode DUL1. The second lower arm path is an electrical path that extends from the center of the low potential side bus bar 71 in the X direction to the intermediate terminal CM1 of the intermediate module MM via the low potential side external terminal CN of the second module M2, the U-phase second lower arm diode DUL2, the intermediate external terminal CO of the second module M2, the first connecting portion 70a, and the second connecting portion 70b, and corresponds to the U-phase second lower arm diode DUL2. Note that the impedances of the first and second lower arm paths are equivalent when, for example, the difference between the impedances of the first and second lower arm paths is within 20% of the larger impedance of the first and second lower arm paths, preferably when the difference is within 15% of the larger impedance of the first and second lower arm paths, and more preferably when the difference is within 5% of the larger impedance of the first and second lower arm paths.

[0040] In this embodiment, no external terminals are provided between the intermediate terminal CM1 and the neutral terminal CM2 on the terminal installation surface 62 of the intermediate module MM. This reduces the density of the external terminals when three modules M1, M2, and MM are assembled in each phase, thereby improving heat dissipation.

[0041] The control device 50 includes a drive circuit 52 (see FIG. 6). The drive circuits 52 are provided individually corresponding to the switches SUH1 to SWL2 included in the inverter 30, for example.

[0042] When the drive circuit 52 determines that the input drive signal is an ON command, it supplies a charging current to the gate of the switch corresponding to it. As a result, the gate voltage of the switch becomes equal to or greater than the threshold voltage Vth, and the switch is turned ON. On the other hand, when the drive circuit 52 determines that the drive signal is an OFF command, it flows a discharging current from the gate of the switch corresponding to it to the ground terminal. As a result, the gate voltage of the switch becomes less than the threshold voltage Vth, and the switch is turned OFF.

[0043] Next, three levels of voltage that can be output from the inverter 30 will be described with reference to Fig. 5. In the following, the U phase will be described as an example.

[0044] The inverter 30 can output three voltage levels: H, M, and L. When the L level voltage is set to 0, the H level voltage is equivalent to the terminal voltage of the series connection of the first and second capacitors 21 and 22, and the M level voltage is equivalent to the terminal voltage of the second capacitor 22.

[0045] When outputting an H-level voltage, the control device 50 turns on the U-phase first and second upper arm switches SUH1 and SUH2 and turns off the U-phase first and second lower arm switches SUL1 and SUL2. The control device 50 also turns on the U-phase first switch SQU1 and turns off the U-phase second switch SQU2. The U-phase second switch SQU2 is turned off to prevent a short circuit across the first capacitor 21 via the U-phase first and second upper arm switches SUH1 and SUH2, the U-phase second switch SQU2, and the U-phase first diode DQU1. Hereinafter, the switching mode when outputting an H-level voltage may be referred to as an H-level mode.

[0046] When outputting an M-level voltage, the control device 50 turns off the U-phase first and second upper arm switches SUH1, SUH2 and the U-phase first and second lower arm switches SUL1, SUL2. The control device 50 also turns on the U-phase first and second switches SQU1, SQU2. Hereinafter, the switching mode when outputting an M-level voltage may be referred to as an M-level mode.

[0047] When switching from one of the H level mode and the M level mode to the other, the control device 50 intervenes in the HM dead time mode. The HM dead time mode is a switching mode in which the U-phase first and second upper arm switches SUH1 and SUH2, the U-phase first and second lower arm switches SUL1 and SUL2, and the U-phase second switch SQU2 are turned off, and the U-phase first switch SQU1 is turned on.

[0048] When outputting an L-level voltage, the control device 50 turns off the U-phase first and second upper-arm switches SUH1 and SUH2 and turns on the U-phase first and second lower-arm switches SUL1 and SUL2. The control device 50 also turns off the U-phase first switch SQU1 and turns on the U-phase second switch SQU2. The U-phase first switch SQU1 is turned off to prevent a short circuit across the second capacitor 22 via the U-phase first and second lower-arm switches SUL1 and SUL2, the U-phase second switch SQU2, and the U-phase first diode DQU1. Hereinafter, the switching mode when outputting an L-level voltage may be referred to as an L-level mode.

[0049] When switching from one of the M level mode and the L level mode to the other, the control device 50 intervenes in the ML dead time mode. The ML dead time mode is a switching mode in which the U-phase first and second upper arm switches SUH1 and SUH2, the U-phase first and second lower arm switches SUL1 and SUL2, and the U-phase first switch SQU1 are turned off, and the U-phase second switch SQU2 is turned on.

[0050] When switching from one of the H level mode and the L level mode to the other, the control device 50 intervenes in the HL dead time mode. The HL dead time mode is a switching mode that turns off the U-phase first and second upper arm switches SUH1, SUH2, the U-phase first and second lower arm switches SUL1, SUL2, and the U-phase first and second switches SQU1, SQU2.

[0051] However, in each phase, an imbalance in the recovery currents flowing through the freewheel diodes of the switches connected in parallel can occur. In this case, the gate voltages of the switches oscillate, potentially causing the switches to fail. Below, we will explain the U-phase upper arm as an example, using Figures 6 and 7. Figures 6 and 7 show the current flow immediately after switching from the L level mode to the H level mode via the HL dead time mode when current flows from the inverter 30 side to the winding side.

[0052] A ground terminal GND1 of the drive circuit 52 electrically connected to the gate of the U-phase first upper arm switch SUH1 is connected to the first upper arm path, for example, between the emitter of the U-phase first upper arm switch SUH1 and the intermediate external terminal CO of the first module M1. Furthermore, a ground terminal GND2 of the drive circuit 52 electrically connected to the gate of the U-phase second upper arm switch SUH2 is connected to the second upper arm path, for example, between the emitter of the U-phase second upper arm switch SUH2 and the intermediate external terminal CO of the second module M2.

[0053] 6, R1 and L1 schematically represent the resistance and inductance components present in the electrical path from the emitter of the U-phase first upper arm switch SUH1 to the ground terminal GND1 in the first upper arm path, and R2 and L2 schematically represent the resistance and inductance components present in the electrical path from the emitter of the U-phase second upper arm switch SUH2 to the ground terminal GND2 in the second upper arm path. ΔV1 represents a voltage difference (hereinafter referred to as the first voltage difference) in the electrical path from the emitter of the U-phase first upper arm switch SUH1 to the ground terminal GND1 in the first upper arm path, and ΔV2 represents a voltage difference (hereinafter referred to as the second voltage difference) in the electrical path from the emitter of the U-phase second upper arm switch SUH2 to the ground terminal GND2 in the second upper arm path.

[0054] An imbalance in the recovery currents flowing through the U-phase first upper-arm diode DUH1 and the U-phase second upper-arm diode DUH2 occurs due to variations in the threshold voltages Vth of the U-phase first and second upper-arm switches SUH1 and SUH2, variations in the decrease speed dif / dt of the forward currents of the U-phase first and second lower-arm diodes DUL1 and DUL2 when switching from the L level mode to the HL dead time mode, and variations in the forward voltages of the U-phase first and second lower-arm diodes DUL1 and DUL2. In the example shown in Fig. 6, the recovery current flowing through the U-phase first upper-arm diode DUH1 is smaller than the recovery current flowing through the U-phase second upper-arm diode DUH2, and the first voltage difference ΔV1 is smaller than the second voltage difference ΔV2.

[0055] In this case, of the switches SUH1, SUH2, the gate voltage of the U-phase first upper-arm switch SUH1, which has the smaller voltage difference, becomes higher than the gate voltage of the U-phase second upper-arm switch SUH2, which has the larger voltage difference. As a result, the on-resistance of the U-phase first upper-arm switch SUH1 becomes smaller than the on-resistance of the U-phase second upper-arm switch SUH2, and now, as shown in Figure 7, the recovery current flowing through the U-phase first upper-arm diode DUH1 becomes larger than the recovery current flowing through the U-phase second upper-arm diode DUH2. As a result, the second voltage difference ΔV2 becomes smaller than the first voltage difference ΔV1.

[0056] In this case, of the switches SUH1, SUH2, the gate voltage of the U-phase second upper arm switch SUH2, which has the smaller voltage difference, becomes higher than the gate voltage of the U-phase first upper arm switch SUH1, which has the larger voltage difference. As a result, the on-resistance of the U-phase second upper arm switch SUH2 becomes smaller than the on-resistance of the U-phase first upper arm switch SUH1, and the recovery current flowing through the U-phase second upper arm diode DUH2 becomes larger than the recovery current flowing through the U-phase first upper arm diode DUH1.

[0057] If this phenomenon is repeated, the gate voltage of each switch SUH1, SUH2 will oscillate. If gate voltage oscillation occurs, the gate voltage may exceed the upper limit of the allowable gate voltage, which may cause failure of switches SUH1, SUH2.

[0058] Therefore, in this embodiment, the characteristic structure of the inverter 30 and the characteristic control of the inverter 30 are used to suppress the occurrence of oscillation of the gate voltage and to suppress the imbalance of the recovery current.

[0059] The characteristic structure is a structure in which the inductances of the first upper arm path and the second upper arm path are made equal, and the inductances of the first lower arm path and the second lower arm path are made equal.

[0060] The characteristic control is oscillation suppression control, which will be described below. When the control device 50 determines that the magnitude of the phase current detected by the current sensor 40 in each phase exceeds the threshold current Ith, it performs oscillation suppression control. When the control device 50 determines that the magnitude of the phase current is less than the threshold current Ith, it performs normal switching control of the inverter 30. The reason why the magnitude of the phase current must exceed the threshold current Ith is that oscillation suppression control is performed only in situations where the degree of imbalance in the recovery current becomes large and gate voltage oscillation is likely to occur. Below, with reference to Figures 8 to 15, an example will be described in which the magnitude of the U-phase current of the U, V, and W phases exceeds the threshold current Ith, and oscillation suppression control is performed for the U-phase.

[0061] 8 shows the transitions of phase currents IU, IV, IW flowing through U-, V-, and W-phase windings 11U, 11V, and 11W, and the transitions of the switching modes of the U-, V-, and W-phases. Phase currents IU, IV, and IW are considered positive when they flow from inverter 30 toward the windings.

[0062] 8, the control device 50 switches to the M level mode at time t1, and switches to the H level mode at time t2. When switching from the L level mode to the H level mode, the control device 50 prohibits the execution of the HL dead time mode and intervenes the M level mode.

[0063] Fig. 9 shows the current flow state when the L level mode is being executed before time t1, and Fig. 10 shows the current flow state when the L level mode is switched to the ML dead time mode just before time t1.

[0064] Subsequently, at time t1, the mode is switched from the ML dead time mode to the M level mode. As a result, as shown in FIG. 11 , a reverse voltage is applied to the U-phase first and second lower-arm diodes DUL1 and DUL2, and then a recovery current flows through the U-phase first and second lower-arm diodes DUL1 and DUL2. In this case, the recovery current flows only through the lower arm of the upper and lower arms. Therefore, the path including the U-phase first and second upper-arm diodes DUH1 and DUH2 and the high-potential side bus bar 72 can be excluded from the recovery current flow path. As a result, factors that cause impedance variations in the two paths through which the recovery current flows can be reduced, and the recovery current imbalance can be suppressed. This suppresses gate voltage oscillation.

[0065] Fig. 12 shows the current flow when the M level mode is being executed before time t3. Fig. 13 shows the current flow when the M level mode is switched to the HM dead time mode just before time t3. The execution period of the HM dead time mode is preferably set to a period equal to or longer than the reverse recovery time of the upper and lower arm diodes DUH1, DUH2, DUL1, and DUL2.

[0066] Subsequently, at time t3, the HM dead time mode is switched to the H level mode. As a result, as shown in FIG. 14, a reverse voltage is applied to the U-phase first and second upper-arm diodes DUH1 and DUH2, and then a recovery current flows through the U-phase first and second upper-arm diodes DUH1 and DUH2. In this case, the recovery current flows only through the upper arm of the upper and lower arms. Therefore, the path including the U-phase first and second lower-arm diodes DUL1 and DUL2 and the low-potential side bus bar 71 can be excluded from the recovery current flow path. As a result, factors that cause impedance variations between the two paths through which the recovery current flows can be reduced, and the recovery current imbalance can be suppressed. This suppresses gate voltage oscillation. Note that FIG. 15 shows the current flow path after recovery is completed immediately after time t3.

[0067] In contrast, when switching from the L level mode to the H level mode, if a comparative example is adopted in which the HL dead time mode is executed and the M level mode is not interposed, the unbalance of the recovery current becomes larger than in this embodiment. Hereinafter, the comparative example will be described with reference to Figures 16 to 20.

[0068] As shown in FIG. 16, the control device of the comparative example switches the U phase from the L level mode to the H level mode at time t1, and switches the V phase from the L level mode to the H level mode at time t2.

[0069] Fig. 17 shows the current flow state when the L level mode is being executed before time t1, and Fig. 18 shows the current flow state when the L level mode is switched to the HL dead time mode just before time t1.

[0070] Thereafter, at time t1, the mode is switched from the HL dead time mode to the H level mode. As a result, as shown in FIG. 19, a recovery current flows through the U-phase first and second upper-arm diodes DUH1 and DUH2 and the U-phase first and second lower-arm diodes DUL1 and DUL2. In this case, the recovery current flow path includes both the upper and lower arm paths. As a result, it is not possible to reduce the factors that cause impedance variations in the two paths through which the recovery current flows. Note that FIG. 20 shows the current flow path after recovery is completed immediately after time t1.

[0071] 21 shows a flowchart of the switching control of the inverter 30 executed by the control device 50. This control is executed for each phase.

[0072] In step S10, it is determined whether the magnitude of the phase current detected by the current sensor 40 exceeds the threshold current Ith.

[0073] If the determination in step S10 is negative, the process proceeds to step S11, where normal switching control is performed on the inverter 30. On the other hand, if the determination in step S10 is positive, the process proceeds to step S12, where oscillation suppression control described with reference to Figs. 8 to 15 is performed.

[0074] As described above, in this embodiment, when switching from the L level mode to the H level mode, the M level mode is temporarily inserted. Specifically, when switching from the L level mode to the H level mode, the control device 50 prohibits execution of the HL dead time mode and switches from the L level mode to the H level mode via the ML dead time mode, M level mode, and HM dead time mode. This suppresses imbalance in the recovery current, and ultimately suppresses oscillation of the gate voltage.

[0075] 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 execution conditions of oscillation suppression control are changed as shown in Fig. 22. More specifically, in step S13, it is determined whether the command torque Trq* exceeds the torque threshold value Trqth. If the determination in step S13 is affirmative, the process proceeds to step S12, where oscillation suppression control is performed.

[0076] According to the present embodiment described above, when the command torque Trq* exceeds the torque threshold Trqth, the oscillation suppression control is executed regardless of the magnitude of the phase current in each phase, thereby achieving the same effects as those of the first embodiment.

[0077] <Third embodiment> The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the control system is provided with individual current sensors that detect the collector current flowing through each switch. As an example of the individual current sensors, FIG. 23 shows a first current sensor 42 that detects the collector current flowing through the U-phase first upper arm switch SUH1 and a second current sensor 43 that detects the collector current flowing through the U-phase second upper arm switch SUH2. The detection values ​​of each current sensor 42, 43 are input to a control device 50.

[0078] In this embodiment, the execution conditions for oscillation suppression control are changed as shown in Fig. 24. More specifically, in step S14, a current difference ΔI, which is the difference between the collector current detected by the first current sensor 42 and the collector current detected by the second current sensor 43, is calculated. Then, it is determined whether the calculated current difference ΔI exceeds a predetermined current difference Iα (for example, 50 A). If the determination in step S14 is positive, the process proceeds to step S12, and oscillation suppression control is performed.

[0079] As with the upper arm, individual current sensors may also be provided for the U-phase first and second lower arm switches SUL1, SUL2, and the process shown in FIG. 24 may be executed.

[0080] According to the present embodiment described above, it is possible to accurately grasp the situation in which the degree of unbalance in the recovery currents becomes large and execute oscillation suppression control.

[0081] <Other embodiments> The above-described embodiments may be modified as follows.

[0082] 23 , one of the first and second current sensors 42, 43 serving as individual current sensors may be provided, for example, at a position on the intermediate bus bar 70 where it can detect the phase current flowing through the winding. In this case, the collector current flowing through the U-phase first and second upper arm switches SUH1, SUH2 that is not provided with an individual current sensor may be calculated based on the detection values ​​of the first and second current sensors 42, 43.

[0083] The positions of the U-phase first switch SQU1 and the U-phase second switch SQU2 may be reversed. The same applies to the V- and W-phase middle switches.

[0084] The semiconductor switching elements constituting the inverter are not limited to IGBTs, but may be, for example, N-channel MOSFETs with body diodes. In this case, the high-potential terminal of the semiconductor switching element is the drain, and the low-potential terminal is the source. In this case, the middle switch of each phase may be composed of two N-channel MOSFETs with their sources or drains connected to each other.

[0085] The three-level inverter may employ either the characteristic structure that equalizes the impedance of each arm path or the characteristic oscillation suppression control, without employing both.

[0086] The number of parallel-connected switches for each phase and each arm is not limited to two, but may be three or more.

[0087] The rotating electrical machine is not limited to a star-connected one, but may be a delta-connected one.

[0088] The inverter, the rotating electric machine, and the control device may be mounted on a moving body such as an aircraft, a ship, etc., and not limited to a vehicle.

[0089] The control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control unit and the method described herein may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described herein may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

[0090] The following describes characteristic configurations extracted from the above-described embodiments. [Configuration 1] A three-level inverter (30) including a plurality of series-connected bodies of upper and lower arm switches (SUH1 to SWL2) in each phase, each series-connected body being connected in parallel in each phase, upper arm diodes (DUH1 to DWH2) connected in anti-parallel to the upper arm switches; Lower arm diodes (DUL1 to DWL2) connected in anti-parallel to the lower arm switches; Middle switches (SQU1 to SQW2) provided for each phase, a high-potential side conductive member (72) provided corresponding to each phase and electrically connecting a high-potential side terminal of each upper arm switch to a positive bus (31); a low-potential side conductive member (71) provided corresponding to each phase and electrically connecting a low-potential side terminal of each lower arm switch to a negative-pole side bus (32); an intermediate conductive member (70) provided corresponding to each phase and electrically connecting a low potential side terminal of each of the upper arm switches and a high potential side terminal of each of the lower arm switches to a first end of the middle switch; Equipped with an electrical path extending from a connection portion (72c) of the high potential side conductive member with the positive side bus bar to the middle switch via the upper arm diodes and the intermediate conductive member, the upper arm paths being configured such that impedances of the upper arm paths corresponding to the upper arm diodes are equal to each other; a three-level inverter, wherein an electrical path extends from a connection portion of the low potential side conductive member with the negative side bus bar through the lower arm diodes and the intermediate conductive member to the middle switch, and the lower arm paths are configured so that the impedances of the lower arm paths corresponding to the lower arm diodes are equivalent. [Configuration 2] The three-level inverter according to configuration 1, wherein for each series connection of the upper and lower arm switches, the series connection, the upper arm diode connected in anti-parallel to the upper arm switch included in the series connection, and the lower arm diode connected in anti-parallel to the lower arm switch included in the series connection are housed in a case (60) and integrated together to form an upper and lower arm module (M1, M2). [Configuration 3] the middle switch includes a first switch (SQU1), a first diode (DQU1) connected in anti-parallel to the first switch, a second switch (SQU2) connected in series to the first switch, and a second diode (DQU2) connected in anti-parallel to the second switch; The three-level inverter according to configuration 2, wherein the first switch, the first diode, the second switch, and the second diode are housed and integrated in a case (60) to form an intermediate module (MM). [Configuration 4] Each phase is provided with two series-connected upper and lower arm switches, The cases of the upper and lower arm modules and the intermediate module are flat rectangular parallelepiped-shaped, The upper and lower arm modules are modules of the same specifications, In each phase, the upper and lower arm modules and the intermediate module are arranged side by side in the thickness direction of the case, In each phase, the intermediate module is disposed in a state sandwiched between the upper and lower arm modules, In each phase, the terminal installation surfaces (62) of the cases of the upper and lower arm modules and the intermediate module face a common specific direction, The terminal installation surface of each of the upper and lower arm modules is provided with a high-potential side external terminal (CP) electrically connected to the high-potential side terminal of the upper arm switch, a low-potential side external terminal (CN) electrically connected to the low-potential side terminal of the lower arm switch, and an intermediate external terminal (CO) electrically connected to the low-potential side terminal of the upper arm switch and the high-potential side terminal of the lower arm switch, the intermediate module is provided with an intermediate terminal (CM2) to which one end of the second switch is electrically connected, In each phase, the intermediate external terminals of the upper and lower arm modules and the intermediate terminals of the intermediate module are arranged side by side in the thickness direction of the case, In each phase, the high-potential side external terminals of the upper and lower arm modules are arranged side by side in the thickness direction of the case, In each phase, the low potential side external terminals of the upper and lower arm modules are arranged side by side in the thickness direction of the case, the high-potential side conductive member electrically connects the high-potential side external terminals of the upper and lower arm modules; the low-potential side conductive member electrically connects the low-potential side external terminals of the upper and lower arm modules; the intermediate conductive member electrically connects the intermediate external terminals of the upper and lower arm modules and the intermediate terminals of the intermediate module; The three-level inverter described in configuration 3, wherein the high-potential side conductive member, the low-potential side conductive member, and the intermediate conductive member are symmetrical with respect to a reference axis (BL) passing through the center of the thickness direction of the case of the intermediate module when viewed from the front of the terminal installation surface. [Configuration 5] the middle switch includes a first switch (SQU1), a first diode (DQU1) connected in anti-parallel to the first switch, a second switch (SQU2) connected in series to the first switch, and a second diode (DQU2) connected in anti-parallel to the second switch; a control device (50) that switches between an H level mode, which is a switching mode in which the upper arm switch is turned on and the lower arm switch is turned off to output an H level voltage, an M level mode, which is a switching mode in which the first and second switches are turned on and the upper and lower arm switches are turned off to output an M level voltage, and an L level mode, which is a switching mode in which the lower arm switch is turned on and the upper arm switch is turned off to output an L level voltage; 5. The three-level inverter according to any one of configurations 1 to 4, wherein the control device performs oscillation suppression control by interposing the M level mode when switching from the L level mode to the H level mode. [Configuration 6] the oscillation suppression control is a control for prohibiting execution of an HL dead time mode, which is a switching mode for turning off the upper and lower arm switches and the middle switch, and for switching from the L level mode to the H level mode via the M level mode and the HM dead time mode, the HM dead time mode is a switching mode in which the upper and lower arm switches and the second switch are turned off and the first switch is turned on; 6. The three-level inverter according to configuration 5, wherein an execution period of the HM dead time mode is set to a period equal to or longer than a reverse recovery time of the upper arm diode and the lower arm diode. [Configuration 7] the control device executes the oscillation suppression control on the condition that a specific condition is satisfied, The specific conditions are: The condition that the magnitude of the output current of the three-level inverter exceeds a threshold current (Ith); a condition that the magnitude of the command torque of the rotating electric machine electrically connected to the three-level inverter exceeds a torque threshold value (Trqth); A condition in which the difference in magnitude of the current flowing between the high potential side terminal and the low potential side terminal of each of the upper arm switches connected in parallel exceeds a predetermined current difference, or The condition that the difference in the magnitude of the current flowing between the high potential side terminal and the low potential side terminal of each of the lower arm switches connected in parallel exceeds a predetermined current difference. 7. The three-level inverter of configuration 5 or 6, [Configuration 8] a first capacitor (21) electrically connecting a second end of the middle switch in each phase to the positive bus; a second capacitor (22) electrically connecting a second end of the middle switch in each phase to the negative bus; 8. The three-level inverter according to any one of configurations 1 to 7, comprising: [Configuration 9] A three-level inverter (30) including a plurality of series-connected bodies of upper and lower arm switches (SUH1 to SWL2) in each phase, each series-connected body being connected in parallel in each phase, upper arm diodes (DUH1 to DWH2) connected in anti-parallel to the upper arm switches; Lower arm diodes (DUL1 to DWL2) connected in anti-parallel to the lower arm switches; Middle switches (SQU1 to SQW2) provided for each phase, a high-potential side conductive member (72) provided corresponding to each phase and electrically connecting a high-potential side terminal of each upper arm switch to a positive bus (31); a low-potential side conductive member (71) provided corresponding to each phase and electrically connecting a low-potential side terminal of each lower arm switch to a negative-pole side bus (32); an intermediate conductive member (70) provided corresponding to each phase and electrically connecting a low potential side terminal of each of the upper arm switches and a high potential side terminal of each of the lower arm switches to a first end of the middle switch; a control device (50); Equipped with the middle switch includes a first switch (SQU1), a first diode (DQU1) connected in anti-parallel to the first switch, a second switch (SQU2) connected in series to the first switch, and a second diode (DQU2) connected in anti-parallel to the second switch; The control device an H level mode, which is a switching mode in which the upper arm switch is turned on and the lower arm switch is turned off to output an H level voltage; an M level mode, which is a switching mode in which the first and second switches are turned on and the upper and lower arm switches are turned off to output an M level voltage; and an L level mode, which is a switching mode in which the lower arm switch is turned on and the upper arm switch is turned off to output an L level voltage; A three-level inverter that performs oscillation suppression control by interposing the M level mode when switching from the L level mode to the H level mode. [Configuration 10] A program applied to a three-level inverter (30) including a plurality of series-connected bodies of upper and lower arm switches (SUH1 to SWL2) in each phase, and in which the series-connected bodies are connected in parallel in each phase, The three-level inverter is upper arm diodes (DUH1 to DWH2) connected in anti-parallel to the upper arm switches; Lower arm diodes (DUL1 to DWL2) connected in anti-parallel to the lower arm switches; Middle switches (SQU1 to SQW2) provided for each phase, a high-potential side conductive member (72) provided corresponding to each phase and electrically connecting a high-potential side terminal of each upper arm switch to a positive bus (31); a low-potential side conductive member (71) provided corresponding to each phase and electrically connecting a low-potential side terminal of each lower arm switch to a negative-pole side bus (32); an intermediate conductive member (70) provided corresponding to each phase and electrically connecting a low potential side terminal of each of the upper arm switches and a high potential side terminal of each of the lower arm switches to a first end of the middle switch; a control device (50); Equipped with the middle switch includes a first switch (SQU1), a first diode (DQU1) connected in anti-parallel to the first switch, a second switch (SQU2) connected in series to the first switch, and a second diode (DQU2) connected in anti-parallel to the second switch; causing the control device to execute a process of switching between an H level mode, which is a switching mode in which the upper arm switch is turned on and the lower arm switch is turned off to output an H level voltage; an M level mode, which is a switching mode in which the first and second switches are turned on and the upper and lower arm switches are turned off to output an M level voltage; and an L level mode, which is a switching mode in which the lower arm switch is turned on and the upper arm switch is turned off to output an L level voltage; a program that causes the control device to execute oscillation suppression control that intervenes in the M level mode when switching from the L level mode to the H level mode; [Explanation of symbols]

[0091] 30... inverter, 50... control device, 70... intermediate bus bar, 71... low potential side bus bar, 72... high potential side bus bar, M1, M2... first and second modules, MM... intermediate module.

Claims

1. A three-level inverter (30) having a plurality of series-connected bodies of upper and lower arm switches (SUH1 to SWL2) in each phase, and the series-connected bodies in each phase connected in parallel, upper arm diodes (DUH1 to DWH2) connected in anti-parallel to the upper arm switches; Lower arm diodes (DUL1 to DWL2) connected in anti-parallel to the lower arm switches; Middle switches (SQU1 to SQW2) provided corresponding to each phase; a high-potential side conductive member (72) provided corresponding to each phase and electrically connecting a high-potential side terminal of each upper arm switch and a positive side bus (31); a low-potential side conductive member (71) provided corresponding to each phase and electrically connecting a low-potential side terminal of each lower arm switch to a negative side bus (32); an intermediate conductive member (70) provided corresponding to each phase and electrically connecting a low potential side terminal of each of the upper arm switches and a high potential side terminal of each of the lower arm switches to a first end of the middle switch; Equipped with an electrical path extending from a connection portion (72c) of the high potential side conductive member with the positive side bus bar to the middle switch via the upper arm diodes and the intermediate conductive member, the upper arm paths being configured such that impedances of the upper arm paths corresponding to the upper arm diodes are equal to each other; a three-level inverter, wherein an electrical path extends from a connection portion of the low potential side conductive member with the negative side bus bar through the lower arm diodes and the intermediate conductive member to the middle switch, and the lower arm paths are configured so that the impedances of the lower arm paths corresponding to the lower arm diodes are equivalent.

2. 2. The three-level inverter according to claim 1, wherein for each series-connected body of the upper and lower arm switches, the series-connected body, the upper arm diode connected in anti-parallel to the upper arm switch included in the series-connected body, and the lower arm diode connected in anti-parallel to the lower arm switch included in the series-connected body are housed in a case (60) and integrated together to form an upper and lower arm module (M1, M2).

3. The middle switch includes a first switch (SQU1), a first diode (DQU1) connected in anti-parallel to the first switch, a second switch (SQU2) connected in series to the first switch, and a second diode (DQU2) connected in anti-parallel to the second switch, 3. The three-level inverter according to claim 2, wherein the first switch, the first diode, the second switch, and the second diode are housed and integrated in a case (60) to form an intermediate module (MM).

4. Two series-connected upper and lower arm switches are provided in each phase, The cases of the upper and lower arm modules and the intermediate module are flat rectangular parallelepiped-shaped, The upper and lower arm modules are modules of the same specifications, In each phase, the upper and lower arm modules and the intermediate module are arranged side by side in the thickness direction of the case, In each phase, the intermediate module is disposed in a state sandwiched between the upper and lower arm modules, In each phase, the terminal installation surfaces (62) of the cases of the upper and lower arm modules and the intermediate module face a common specific direction, The terminal installation surface of each of the upper and lower arm modules is provided with a high-potential side external terminal (CP) electrically connected to the high-potential side terminal of the upper arm switch, a low-potential side external terminal (CN) electrically connected to the low-potential side terminal of the lower arm switch, and an intermediate external terminal (CO) electrically connected to the low-potential side terminal of the upper arm switch and the high-potential side terminal of the lower arm switch, the intermediate module is provided with an intermediate terminal (CM2) to which one end of the second switch is electrically connected; In each phase, the intermediate external terminals of the upper and lower arm modules and the intermediate terminals of the intermediate module are arranged side by side in the thickness direction of the case, In each phase, the high-potential side external terminals of the upper and lower arm modules are arranged side by side in the thickness direction of the case, In each phase, the low potential side external terminals of the upper and lower arm modules are arranged side by side in the thickness direction of the case, the high-potential side conductive member electrically connects the high-potential side external terminals of the upper and lower arm modules; the low-potential side conductive member electrically connects the low-potential side external terminals of the upper and lower arm modules; the intermediate conductive member electrically connects the intermediate external terminals of the upper and lower arm modules and the intermediate terminals of the intermediate module; 4. The three-level inverter according to claim 3, wherein the high-potential side conductive member, the low-potential side conductive member, and the intermediate conductive member are shaped symmetrically with respect to a reference axis (BL) passing through a center portion in a thickness direction of the case of the intermediate module when viewed from the front of the terminal installation surface.

5. The middle switch includes a first switch (SQU1), a first diode (DQU1) connected in anti-parallel to the first switch, a second switch (SQU2) connected in series to the first switch, and a second diode (DQU2) connected in anti-parallel to the second switch, a control device (50) that switches between an H level mode, which is a switching mode in which the upper arm switch is turned on and the lower arm switch is turned off to output an H level voltage, an M level mode, which is a switching mode in which the first and second switches are turned on and the upper and lower arm switches are turned off to output an M level voltage, and an L level mode, which is a switching mode in which the lower arm switch is turned on and the upper arm switch is turned off to output an L level voltage; The three-level inverter according to any one of claims 1 to 4, wherein the control device performs oscillation suppression control to intervene in the M level mode when switching from the L level mode to the H level mode.

6. the oscillation suppression control is a control for prohibiting execution of an H-L dead time mode, which is a switching mode for turning off the upper and lower arm switches and the middle switch, and for switching from the L level mode to the H level mode via the M level mode and the H-M dead time mode, the HM dead time mode is a switching mode in which the upper and lower arm switches and the second switch are turned off and the first switch is turned on; 6. The three-level inverter according to claim 5, wherein an execution period of the HM dead time mode is set to a period equal to or longer than a reverse recovery time of the upper arm diode and the lower arm diode.

7. the control device executes the oscillation suppression control on the condition that a specific condition is satisfied, The specific conditions are: The condition that the magnitude of the output current of the three-level inverter exceeds a threshold current (Ith); a condition that the magnitude of a command torque of a rotating electric machine electrically connected to the three-level inverter exceeds a torque threshold value (Trqth); The condition that the difference in magnitude of the current flowing between the high potential side terminal and the low potential side terminal of each of the upper arm switches connected in parallel exceeds a predetermined current difference (Iα), or The condition that the difference in the magnitude of the current flowing between the high potential side terminal and the low potential side terminal of each of the lower arm switches connected in parallel exceeds a predetermined current difference (Iα). The three-level inverter according to claim 5, wherein

8. a first capacitor (21) electrically connecting a second end of the middle switch in each phase to the positive bus; a second capacitor (22) electrically connecting a second end of the middle switch in each phase to the negative bus; The three-level inverter according to any one of claims 1 to 4, comprising:

9. A three-level inverter (30) having a plurality of series-connected bodies of upper and lower arm switches (SUH1 to SWL2) in each phase, and the series-connected bodies in each phase connected in parallel, upper arm diodes (DUH1 to DWH2) connected in anti-parallel to the upper arm switches; Lower arm diodes (DUL1 to DWL2) connected in anti-parallel to the lower arm switches; Middle switches (SQU1 to SQW2) provided corresponding to each phase; a high-potential side conductive member (72) provided corresponding to each phase and electrically connecting a high-potential side terminal of each upper arm switch and a positive side bus (31); a low-potential side conductive member (71) provided corresponding to each phase and electrically connecting a low-potential side terminal of each lower arm switch to a negative side bus (32); an intermediate conductive member (70) provided corresponding to each phase and electrically connecting a low potential side terminal of each of the upper arm switches and a high potential side terminal of each of the lower arm switches to a first end of the middle switch; A control device (50); Equipped with The middle switch includes a first switch (SQU1), a first diode (DQU1) connected in anti-parallel to the first switch, a second switch (SQU2) connected in series to the first switch, and a second diode (DQU2) connected in anti-parallel to the second switch, The control device an H level mode, which is a switching mode in which the upper arm switch is turned on and the lower arm switch is turned off to output an H level voltage; an M level mode, which is a switching mode in which the first and second switches are turned on and the upper and lower arm switches are turned off to output an M level voltage; and an L level mode, which is a switching mode in which the lower arm switch is turned on and the upper arm switch is turned off to output an L level voltage. A three-level inverter that performs oscillation suppression control by interposing the M level mode when switching from the L level mode to the H level mode.

10. A program applied to a three-level inverter (30) having a plurality of series-connected upper and lower arm switches (SUH1 to SWL2) in each phase, the series-connected switches being connected in parallel in each phase, The three-level inverter comprises: upper arm diodes (DUH1 to DWH2) connected in anti-parallel to the upper arm switches; Lower arm diodes (DUL1 to DWL2) connected in anti-parallel to the lower arm switches; Middle switches (SQU1 to SQW2) provided corresponding to each phase; a high-potential side conductive member (72) provided corresponding to each phase and electrically connecting a high-potential side terminal of each upper arm switch and a positive side bus (31); a low-potential side conductive member (71) provided corresponding to each phase and electrically connecting a low-potential side terminal of each lower arm switch to a negative side bus (32); an intermediate conductive member (70) provided corresponding to each phase and electrically connecting a low potential side terminal of each of the upper arm switches and a high potential side terminal of each of the lower arm switches to a first end of the middle switch; A control device (50); Equipped with The middle switch includes a first switch (SQU1), a first diode (DQU1) connected in anti-parallel to the first switch, a second switch (SQU2) connected in series to the first switch, and a second diode (DQU2) connected in anti-parallel to the second switch, causing the control device to execute a process of switching between an H level mode, which is a switching mode in which the upper arm switch is turned on and the lower arm switch is turned off to output an H level voltage; an M level mode, which is a switching mode in which the first and second switches are turned on and the upper and lower arm switches are turned off to output an M level voltage; and an L level mode, which is a switching mode in which the lower arm switch is turned on and the upper arm switch is turned off to output an L level voltage; a program that causes the control device to execute oscillation suppression control that causes the M level mode to be interposed when switching from the L level mode to the H level mode;

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