Control device for three-level inverter and program

Abstract

To provide a control device for a three-level inverter capable of suppressing the occurrence of a situation where a load is concentrated on a specific switch.SOLUTION: A control device 50 is applied to a system comprising first and second power storage sections 21 and 22, a rotary electric machine 10 and a three-level inverter 30 and performs switching control of switches SUH-SWL and QU1-QW2. The control device 50 comprises: a setting section which sets a drive pattern consisting of a combination of drive states of the switches SUH-SWL and QU1-QW2 and appearance periods of the drive states on the basis of a command voltage for controlling a control amount of the rotary electric machine 10 into a command value; and a control section which performs the switching control on the basis of the set drive pattern and the set appearance periods of the drive states. The setting section sets the drive pattern so as to include at least two of three different zero voltage drive states. The control section adjusts the appearance period of each zero voltage drive state included in the drive pattern during the switching control.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a control device and a program for a three-level inverter. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a three-level inverter is known that includes two capacitors connected in series and switches electrically connected to an armature winding of a rotating electric machine and each of the capacitors (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-98540 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to prevent a decrease in the reliability of the switches provided corresponding to each phase, it is desirable to prevent the occurrence of a situation in which the load is concentrated on a specific switch among the switches.

[0005] A main object of the present disclosure is to provide a control device and program for a three-level inverter that can suppress the occurrence of a situation in which a load is concentrated on a specific switch. [Means for solving the problem]

[0006] The present disclosure relates to a first power storage unit and a second power storage unit connected in series; A rotating electric machine having three-phase armature windings; a three-level inverter having a switch for electrically connecting the armature winding in each phase to any of a positive electrode side of the first power storage unit, a neutral point between the negative electrode side of the first power storage unit and the positive electrode side of the second power storage unit, and a negative electrode side of the second power storage unit, the three-level inverter control device performing switching control of each of the switches, a setting unit that sets a drive pattern including a combination of drive states of the switches and an appearance period of each of the drive states based on a command voltage for controlling a control amount of the rotary electric machine to a command value; a control unit that performs the switching control based on the set drive pattern and the appearance period of each of the drive states, three different drive states in which the armature winding of each phase is electrically connected to the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit are defined as zero-voltage drive states; the setting unit sets the drive pattern so as to include at least two of the zero voltage drive states; In the switching control, the control unit adjusts an appearance period of each of the zero voltage drive states included in the drive pattern.

[0007] A drive pattern consisting of a combination of drive states of each switch and the appearance period of each drive state are set based on a command voltage for controlling the control amount of the rotating electric machine to a command value. Then, switching control of each switch is performed based on the set drive pattern and the appearance period of each drive state. In this case, the load may be concentrated on a specific switch among the switches. In this regard, a three-level inverter can output three different zero voltage drive states. In each zero voltage drive state, the current path is different, and the switch in which conduction loss occurs is different.

[0008] Therefore, in the present disclosure, in the switching control of each switch, the appearance period of each zero voltage drive state included in the drive pattern is adjusted. In this case, it is possible to control the loss occurring in each switch within an adjustable range of the appearance period of each zero voltage drive state. This makes it possible to perform switching control so as to avoid the loss occurring in a concentrated manner in a specific switch among the switches. Therefore, it is possible to suppress the occurrence of a situation in which the load is concentrated on a specific switch. [Brief description of the drawings]

[0009] [Figure 1] 1 is an overall configuration diagram of a control system according to a first embodiment. [Diagram 2] FIG. 4 is a functional block diagram of a torque control process executed by the control device. [Diagram 3] Diagram showing vector space. [Figure 4] A diagram showing the first sector. [Diagram 5] 4 is a time chart for explaining a process performed by an adjustment unit. [Figure 6] 4 is a time chart for explaining a process performed by an adjustment unit. [Figure 7] 4 is a flowchart showing a control process performed by the control device. [Figure 8] 5 is a time chart showing switching control of a comparative example. [Figure 9] 4 is a time chart showing an example of switching control. [Figure 10] FIG. 4 is a diagram for explaining the switching mode of each switch of a U phase. [Figure 11] FIG. 4 is a diagram for explaining the switching mode of each switch of a U phase. [Figure 12] FIG. 4 is a diagram for explaining the switching mode of each switch of a U phase. [Figure 13] FIG. 4 is a diagram for explaining the switching mode of each switch of a U phase. [Figure 14] 10 is a time chart for explaining a process performed by an adjustment unit according to a second embodiment. [Figure 15]4 is a flowchart showing a control process performed by the control device. [Figure 16] A diagram showing the power loss generated in each switch of the U phase. [Figure 17] 10 is a flowchart showing a procedure of a control process performed by a control device according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 given the same reference numerals or reference numerals with different digits of 100 or more. For corresponding and / or associated parts, the description of other embodiments may be referred to.

[0011] First Embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a control device according to the present disclosure will now be described with reference to the drawings. In this embodiment, the control device is mounted on an electrically powered vehicle such as an electric vehicle or a hybrid vehicle.

[0012] As shown in Fig. 1, the vehicle-mounted system includes a rotating electric machine 10, a storage battery 20, and an inverter 30. The rotating electric machine 10 is a vehicle-mounted main engine and is capable of transmitting power to driving wheels (not shown). The rotating electric machine 10 of this embodiment is a three-phase synchronous machine and includes armature windings, that is, a U-phase winding 11U, a V-phase winding 11V, and a W-phase winding 11W. The phase windings 11U, 11V, and 11W are star-connected. The phase windings 11U, 11V, and 11W are arranged with a 120° electrical angle difference between them. The rotating electric machine 10 is, for example, a permanent magnet synchronous machine.

[0013] The storage battery 20 is electrically connected to the rotating electric machine 10 via the inverter 30. The storage battery 20 is, for example, a battery pack including a series connection of battery cells. The storage battery 20 is a chargeable and dischargeable secondary battery, for example, a lithium ion battery or a nickel metal hydride battery.

[0014] The inverter 30 is a power conversion circuit that converts DC power supplied from the storage battery 20 into three-phase AC power by switching control and supplies the converted AC power to the rotating electric machine 10. The system includes a first capacitor 21 as a first power storage unit and a second capacitor 22 as a second power storage unit on the input side of the inverter 30. 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. The first capacitor 21 and the second capacitor 22 may be provided outside the inverter 30 or may be built into the inverter 30.

[0015] The inverter 30 is a T-type three-level inverter and includes three phases of series-connected upper arm switches SUH, SVH, SWH and lower arm switches SUL, SVL, SWL. Each switch SUH to SWL is a voltage-controlled semiconductor switching element, specifically an IGBT. In each switch SUH to SWL, the high potential side terminal is the collector and the low potential side terminal is the emitter. Freewheel diodes DUH, DVH, DWH, DUL, DVL, DWL are connected in inverse parallel to each switch SUH, SVH, SWH, SUL, SVL, SWL.

[0016] The emitter of the U-phase upper arm switch SUH is connected to the collector of the U-phase lower arm switch SUL. A connection point between the U-phase upper arm switch SUH and the U-phase lower arm switch SUL is connected to a first end of the U-phase winding 11U. The emitter of the V-phase upper arm switch SVH is connected to the collector of the V-phase lower arm switch SVL. A connection point between the V-phase upper arm switch SVH and the V-phase lower arm switch SVL is connected to a first end of the V-phase winding 11V. The emitter of the W-phase upper arm switch SWH is connected to the collector of the W-phase lower arm switch SWL. A connection point between the W-phase upper arm switch SWH and the W-phase lower arm switch SWL is connected to a first end of the W-phase winding 11W. Second ends of the respective phase windings 11U, 11V, 11W are connected to each other at the motor neutral point.

[0017] The collectors of each of the upper arm switches SUH to SWH are connected by a positive bus bar 31 which is a conductive member such as a bus bar. The positive bus bar 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 via a capacitor neutral point O. The emitters of each of the lower arm switches SUL to SWL are connected by a negative bus bar 32 which is a conductive member such as a bus bar. The negative bus bar 32 is connected to the negative terminal of the storage battery 20 and a second end of the second capacitor 22.

[0018] The inverter 30 includes middle switches QU1, QU2, QV1, QV2, QW1, and QW2 for three phases, which conduct and cut off current in both directions. In this embodiment, the middle switches QU1, QU2, QV1, QV2, QW1, and QW2 are voltage-controlled semiconductor switching elements, specifically IGBTs.

[0019] Specifically, taking the U-phase as an example, the emitters of the U-phase first middle switch QU1 and the U-phase second middle switch QU2 are connected to each other. The collector of the U-phase second middle switch QU2 is connected to the connection point between the U-phase upper arm switch SUH and the U-phase lower arm switch SUL. The collector of the U-phase first middle switch QU1 is connected to the capacitor neutral point O.

[0020] In each phase, the first diodes DU1, DV1, DW1 as freewheel diodes are connected in anti-parallel to the first middle switches QU1, QV1, QW1, and in each phase, the second diodes DU2, DV2, DW2 as freewheel diodes are connected in anti-parallel to the second middle switches QU2, QV2, QW2,.

[0021] The motor control system includes a first voltage sensor 41, a second voltage sensor 42, a phase current sensor 43, a rotation angle sensor 44, and a temperature sensor 45. The first voltage sensor 41 detects the terminal voltage of the first capacitor 21. The second voltage sensor 42 detects the terminal voltage of the second capacitor 22. The phase current sensor 43 detects the U, V, and W phase currents flowing through the respective phase windings 11U, 11V, and 11W. The phase current sensor 43 only needs to detect at least two of the three phase currents. The rotation angle sensor 44 is, for example, a resolver, and detects the electrical angle of the rotating electric machine 10. The temperature sensor 45 detects the temperature of the inverter 30. For example, the temperature sensor 45 detects at least one of the temperature of the cooling water that cools the inverter 30 and the temperature of each of the switches SUH to SWL, QU1 to QW2. The detection values ​​of the sensors 41 to 45 are input to a control device 50 provided in the system.

[0022] The control device 50 is an electronic control unit mainly composed of a microcomputer 51. The microcomputer 51 includes a CPU (Central Processing Unit). The functions provided by the microcomputer 51 can be provided by software recorded in a substantial memory device and a computer that executes the software, by software alone, by hardware alone, or by a combination of these. For example, when the microcomputer 51 is provided by an electronic circuit that is hardware, the functions can be provided by a digital circuit including a large number of logic circuits, or by an analog circuit. For example, the microcomputer 51 executes a program stored in a non-transitory tangible storage medium as a storage unit provided in the microcomputer 51. The program includes, for example, programs for processing shown in Figs. 7, 15, 17, etc., which will be described later. A method corresponding to the program is executed by executing a set of instructions that constitute the program. The storage unit is, for example, a non-volatile memory. The program stored in the storage unit can be updated via a communication network such as the Internet, for example, OTA (Over The Air), etc.

[0023] The control device 50 controls the control amount of the rotating electric machine 10 to a command value, and performs switching control of the switches SUH-SWL, QU1-QW2 of the inverter 30. The switching control of the control device 50 will be described with reference to Fig. 2. In the example shown in Fig. 2, current feedback control is performed in the switching control. The control amount is the torque of the rotating electric machine 10, and the command value is a command torque Trq* input from a higher-level control device.

[0024] In the control device 50, the command current setting unit 60 sets the d-axis and q-axis command currents Id* and Iq* based on the command torque Trq*. For example, the command current setting unit 60 may set the d-axis and q-axis command currents Id* and Iq* based on map information or formula information in which the command torque Trq* and the d-axis and q-axis command currents Id* and Iq* are associated with each other.

[0025] The two-phase conversion unit 61 converts the U-, V-, and W-phase currents in the three-phase fixed coordinate system into a d-axis current Idr and a q-axis current Iqr in a two-phase rotating coordinate system (dq coordinate system) based on the detection value of the phase current sensor 43 and the electrical angle θe detected by the rotation angle sensor 44.

[0026] The d-axis deviation calculation unit 62a calculates the d-axis current deviation ΔId by subtracting the d-axis current Idr from the d-axis command current Id*. The q-axis deviation calculation unit 62b calculates the q-axis current deviation ΔIq by subtracting the q-axis current Iqr from the q-axis command current Iq*.

[0027] The d-axis command voltage calculation unit 63a calculates a d-axis command voltage Vd based on the d-axis current deviation ΔId as a manipulated variable for feedback-controlling the d-axis current Idr to the d-axis command current Id*. The q-axis command voltage calculation unit 63b calculates a q-axis command voltage Vq based on the q-axis current deviation ΔIq as a manipulated variable for feedback-controlling the q-axis current Iqr to the q-axis command current Iq*. The feedback control used by the d-axis command voltage calculation unit 63a and the q-axis command voltage calculation unit 63b may be, for example, proportional-integral control.

[0028] The fixed coordinate conversion unit 64 receives the d, q-axis command voltages Vd, Vq output from the d, q-axis command voltage calculation units 63a, 63b and the electrical angle θe detected by the rotation angle sensor 44. The fixed coordinate conversion unit 64 converts the d, q-axis command voltages Vd, Vq in the two-phase rotating coordinate system into α, β-axis command voltages Vα, Vβ in the two-phase fixed coordinate system based on the d, q-axis command voltages Vd, Vq and the electrical angle θe.

[0029] The modulator 65 calculates a command voltage vector Vαβ determined by the α-axis and β-axis command voltages Vα and Vβ. The command voltage vector Vαβ is a voltage vector for controlling the control amount of the rotary electric machine 10 to a command value.

[0030] The modulation unit 65 specifies a sector in which the tip of the command voltage vector Vαβ extending from the origin in the vector space exists. The sectors divide the vector space in which the command voltage vector Vαβ can exist into six sectors in terms of the deflection angle of the command voltage vector Vαβ. The deflection angle of the command voltage vector Vαβ is the angle between the command voltage vector Vαβ and the U-phase axis, and is specifically the electrical angle θe. The sign of the electrical angle θe is positive in the leftward (counterclockwise) direction. FIG. 3 shows the first to sixth sectors that divide the vector space into six sectors. In the vector space, the axes of the U, V, and W phases are arranged with an electrical angle shift of 120° each. Each sector is an area sandwiched between the axes of two phases that have an electrical angle difference of 60° from each other. In FIG. 3, the range indicating the first sector is hatched.

[0031] The first to sixth sectors are further divided into four regions. In detail, the end point of the sector on the first axis L1, which has a smaller deflection angle among the two-phase axes dividing each sector, is defined as the first end point, and the end point of the sector on the second axis L2, which has a larger deflection angle, is defined as the second end point. Also, the midpoint between the origin and the first end point of the vector space is defined as the first intermediate point, the midpoint between the origin and the second end point is defined as the second intermediate point, and the midpoint between the first end point and the second end point is defined as the intermediate end point. In this case, the first region R1 is a region surrounded by a triangle with the origin, the first intermediate point, and the second intermediate point as vertices. The second region R2 is a region surrounded by a triangle with the first intermediate point, the second intermediate point, and the intermediate end point as vertices. The third region R3 is a region surrounded by a triangle with the second end point, the second intermediate point, and the intermediate end point as vertices. The fourth region R4 is a region surrounded by a triangle having vertices at the first end point, the first intermediate point, and the intermediate end point. Note that in Fig. 4, the first to fourth regions R1 to R4 are shown using the first sector as an example.

[0032] Returning to the previous explanation of FIG. 2, for example, when 0°≦θe<60°, the modulation unit 65 determines that the tip of the command voltage vector Vαβ is present in the first sector.

[0033] The modulator 65 identifies a sub-region in which the tip of the command voltage vector Vαβ exists among the first to fourth regions R1 to R4 constituting the identified sector, based on the magnitude of the command voltage vector Vαβ and the in-sector angle α. The in-sector angle α is the angle between the first axis L1 extending from the origin to the first end point in the target sector and the command voltage vector Vαβ.

[0034] The modulation unit 65 selects the drive states of the switches SUH-SWL, QU1-QW2 based on the identified sector and the sub-area within that sector. As the drive states of the switches SUH-SWL, QU1-QW2, drive states corresponding to the three vertices that make up the sub-area are selected.

[0035] As shown in FIG. 4, in the first sector, the first endpoint is "HLL", the second endpoint is "HHL", the first intermediate points are "MLL" and "HMM", the second intermediate points are "HHM" and "MML", and the intermediate endpoint is "HML".

[0036] The symbols such as "HML" mentioned above represent the output voltage level of each phase by three voltage levels H, M, L, which correspond to the driving states of each switch SUH to SWL, QU1 to QW2.

[0037] A level H phase voltage is output by electrically connecting the winding of a target phase to the first end of the first capacitor 21. In this case, in the target phase, the upper arm switch is turned on and the lower arm switch is turned off. Also, in the target phase, the first middle switch is turned on and the second middle switch is turned off. When a level H phase voltage is output, the second middle switch in the target phase is turned off in order to prevent both ends of the first capacitor 21 from being short-circuited via the upper arm switch, the second middle switch, and the first diode.

[0038] A phase voltage of level M is output by electrically connecting the winding of the target phase to the capacitor neutral point O. In this case, in the target phase, the first middle switch and the second middle switch are turned on, and the upper and lower arm switches are turned off.

[0039] A level L phase voltage is output by electrically connecting the winding of a target phase to the second end of the second capacitor 22. In this case, in the target phase, the lower arm switch is turned on and the upper arm switch is turned off. In addition, in the target phase, the second middle switch is turned on and the first middle switch is turned off. When a level L phase voltage is output, the first middle switch in the target phase is turned off in order to prevent both ends of the second capacitor 22 from being short-circuited via the lower arm switch, the first middle switch, and the second diode.

[0040] In addition, if the voltage of the storage battery 20 is Vdc and the second end side of the second capacitor 22 is at the reference potential (0 V), the phase voltage of level H is "Vdc", the phase voltage of level M is "Vdc / 2", and the phase voltage of level L is "0".

[0041] For example, "HML" is a driving state of the switches SUH-SWL, QU1-QW2 in which the U-phase voltage is level H, the V-phase voltage is level M, and the W-phase voltage is level L. In the driving state HML, the U-phase upper arm switch SUH, the U-phase first middle switch QU1, the V-phase first middle switch QV1, the V-phase second middle switch QV2, the W-phase lower arm switch SWL, and the W-phase second middle switch QW2 are turned on, and the V- and W-phase upper arm switches SVH and SWH, the U-phase second middle switch QU2, the W-phase first middle switch QW1, and the U- and V-phase lower arm switches SUL and SVL are turned off.

[0042] "HHH" is a zero voltage drive state of the switches SUH-SWL, QU1-QW2 in which the output voltage levels of all three phases are H. In the zero voltage drive state HHH, the upper arm switches SUH, SVH, SWH and the first middle switches QU1, QV1, QW1 of each phase are turned on, while the lower arm switches SUL, SVL, SWL and the second middle switches QU2, QV2, QW2 of each phase are turned off. In this case, the windings 11U, 11V, 11W of each phase are electrically connected via the upper arm switches SUH, SVH, SWH of each phase.

[0043] "MMM" is a zero-voltage drive state of the switches SUH-SWL, QU1-QW2 in which the output voltage levels of all three phases are set to M. In the zero-voltage drive state MMM, the first middle switches QU1, QV1, QW1 and the second middle switches QU2, QV2, QW2 of each phase are turned on, and the upper arm switches SUH, SVH, SWH and the lower arm switches SUL, SVL, SWL of each phase are turned off. In this case, the windings 11U, 11V, 11W of each phase are electrically connected via the first middle switches QU1, QV1, QW1 of each phase and the second middle switches QU2, QV2, QW2 of each phase.

[0044] "LLL" is a zero voltage drive state of the switches SUH-SWL, QU1-QW2 in which the output voltage levels of all three phases are set to L. In the zero voltage drive state LLL, the lower arm switches SUL, SVL, SWL and the second middle switches QU2, QV2, QW2 of each phase are turned on, while the upper arm switches SUH, SVH, SWH and the first middle switches QU1, QV1, QW1 of each phase are turned off. In this case, the windings 11U, 11V, 11W of each phase are electrically connected via the lower arm switches SUL, SVL, SWL of each phase.

[0045] In this embodiment, among the drive states of the switches SUH to SWL and QU1 to QW2, drive states other than the zero voltage drive states HHH, MMM, and LLL are referred to as effective voltage drive states.

[0046] "MLL" and "HMM" are located at the same position in the vector space, and in these two effective voltage drive states, the line voltages applied to the windings 11U to 11W are equivalent. "MML" and "HHM", "LML" and "MHM", "LMM" and "MHH", "LLM" and "MMH", and "MLM" and "HMH" are also similar to "MLL" and "HMM". In this embodiment, "MLL", "MML", "LML", "LMM", "LLM", and "MLM" are referred to as Mid-Lo drive states, and "HMM", "HHM", "MHM", "MHH", "MMH", and "HMH" are referred to as Hi-Mid drive states.

[0047] In the switching control, the direction in which the voltage at the capacitor neutral point O changes is opposite between the period when the Mid-Lo driving state occurs and the period when the Hi-Mid driving state occurs. The modulation unit 65 acquires the detected voltage V1r of the first voltage sensor 41 and the detected voltage V2r of the second voltage sensor 42. In the switching control, the modulation unit 65 is capable of selecting either the Mid-Lo driving state or the Hi-Mid driving state based on the acquired detected voltages V1r, V2r so that the voltage at the capacitor neutral point O falls within a predetermined range.

[0048] The modulation unit 65 sets a drive pattern consisting of a combination of the drive states of the switches SUH-SWL, QU1-QW2 based on the identified sector and the sub-area within that sector. For example, when the modulation unit 65 identifies that the command voltage vector Vαβ exists in the first area R1 of the first sector, it sets a drive pattern for driving the switches SUH-SWL, QU1-QW2 in the order of MMM→MML→MLL→LLL→MLL→MML→MMM, or sets a drive pattern for driving the switches SUH-SWL, QU1-QW2 in the order of MMM→HMM→HHM→HHH→HHM→HMM→MMM.

[0049] When performing switching control with the set drive pattern, the modulation section 65 sets the period during which the drive state of each of the switches SUH to SWL and QU1 to QW2 appears.

[0050] Specifically, as shown in FIG. 4, the case where the command voltage vector Vαβ exists in the first region R1 of the first sector will be described. The modulation unit 65 decomposes the command voltage vector Vαβ into a first voltage vector Vt1 along the first axis L1 and a second voltage vector Vt2 along the second axis L2. The first voltage vector Vt1 is a vector obtained by multiplying the voltage vector corresponding to the first midpoint by ta (0 < ta < 1). The second voltage vector Vt2 is a vector obtained by multiplying the voltage vector corresponding to the second midpoint by tb (0 < tb < 1). The modulation unit 65 sets the appearance period of the driving state corresponding to the first midpoint to "ta × TS" and the appearance period of the driving state corresponding to the second midpoint to "tb × TS" in one control period. Here, TS is the length of one control period.

[0051] The modulation unit 65 sets the remaining period Tz (= TS - ta × TS - tb × TS) obtained by subtracting "ta × TS" and "tb × TS" from the length TS of one control period as the appearance period of the zero voltage driving state. The remaining period Tz is the total period of the appearance periods of the respective zero voltage driving states HHH, MMM, and LLL in one control period. Note that a period twice the length TS of one control period corresponds to one switching period Tsw of each switch SUH to SWL, QU1 to QW2.

[0052] For example, when the modulation unit 65 sets a driving pattern including the driving states MML, MLL, MMM, and LLL, the appearance period of the driving state MLL is set to "ta × TS", and the appearance period of the driving state MML is set to "tb × TS". Then, the modulation unit 65 sets the appearance period of the zero voltage driving state LLL to "TL" and the appearance period of the zero voltage driving state MMM to "TM". In this case, the total period "TM + TL" of the appearance periods of the respective zero voltage driving states MMM and LLL is the remaining period Tz.

[0053] Also, for example, when the modulation unit 65 sets a drive pattern including the drive states HMM, HHM, HHH, and MMM, it sets the appearance period of the drive state HMM to "ta x TS" and the appearance period of the drive state HHM to "tb x TS". Then, the modulation unit 65 sets the appearance period of the zero voltage drive state HHH to "TH" and the appearance period of the zero voltage drive state MMM to "TM". In this case, the total appearance period of the zero voltage drive states HHH and MMM, "TH + TM", is the remaining period Tz.

[0054] Switching control is performed based on the drive pattern set by the modulation unit 65 and the appearance period of each drive state, so that the torque of the rotary electric machine 10 is controlled to the command torque Trq*.

[0055] Incidentally, there is a concern that during switching control, the load may be concentrated on a specific switch among the switches SUH to SWL and QU1 to QW2.

[0056] Specifically, during switching control when the tip of the command voltage vector Vαβ is in the first region of each sector, the appearance period TM of the zero voltage driving state MMM may be longer than the appearance periods TH, TL of the other zero voltage driving states HHH, LLL. For example, in a situation where the running load is small, such as a situation where the vehicle speed is low and the torque of the rotating electric machine 10 is low, the appearance period TM of the zero voltage driving state MMM is likely to be longer than the appearance periods TH, TL of the other zero voltage driving states HHH, LLL. In this case, there is a concern that the load will be concentrated on each of the middle switches QU1 to QW2 due to the large conduction loss of each of the middle switches QU1 to QW2 among the switches SUH to SWL and QU1 to QW2.

[0057] Here, the three-level inverter can output three different zero-voltage drive states HHH, MMM, and LLL. In each of the zero-voltage drive states HHH, MMM, and LLL, the current path is different and the switch in which the conduction loss occurs is different.

[0058] Therefore, the control device 50 includes an adjustment unit 66. In the switching control of the switches SUH-SWL, QU1-QW2, the adjustment unit 66 adjusts the appearance period of each of the zero voltage driving states HHH, MMM, and LLL included in the drive pattern. In this embodiment, the adjustment unit 66 adjusts the appearance period of each of the zero voltage driving states HHH, MMM, and LLL included in the drive pattern so that the appearance period of the zero voltage driving state MMM included in the drive pattern is shorter than the appearance period TM set by the modulation unit 65. It should be noted that the zero voltage driving state MMM corresponds to a "specific driving state."

[0059] The process performed by the adjustment unit 66 will be described below with reference to Fig. 5 and Fig. 6. Fig. 5 and Fig. 6 show an example of the transition of each phase voltage for two control cycles. In Fig. 5 and Fig. 6, (a) shows the transition of the U-phase voltage level, (b) shows the transition of the V-phase voltage level, and (c) shows the transition of the W-phase voltage level.

[0060] In FIG. 5, the switches SUH to SWL and QU1 to QW2 are driven in the order of MMM→MML→MLL→LLL→MLL→MML→MMM.

[0061] The adjustment unit 66 shortens the appearance period of the zero voltage driving state MMM by subtracting a predetermined adjustment period k from the appearance period TM of the zero voltage driving state MMM set by the modulation unit 65. The adjustment unit 66 extends the appearance period of the zero voltage driving state LLL by adding a predetermined adjustment period k to the appearance period TL of the zero voltage driving state LLL set by the modulation unit 65. That is, the adjustment unit 66 adjusts the appearance period of the zero voltage driving state MMM to "TM-k" and adjusts the appearance period of the zero voltage driving state LLL to "TL+k" in one control cycle. This shortens the appearance period of the zero voltage driving state MMM without changing the total period (that is, the remaining period Tz) of the appearance periods of the zero voltage driving states MMM and LLL in one control cycle.

[0062] In FIG. 6, the switches SUH to SWL and QU1 to QW2 are driven in the order of MMM→HMM→HHM→HHH→HHM→HMM→MMM.

[0063] The adjustment unit 66 shortens the appearance period of the zero voltage driving state MMM by subtracting a predetermined adjustment period k from the appearance period TM of the zero voltage driving state MMM set by the modulation unit 65. The adjustment unit 66 extends the appearance period of the zero voltage driving state HHH by adding a predetermined adjustment period k to the appearance period TH of the zero voltage driving state HHH set by the modulation unit 65. In other words, the adjustment unit 66 adjusts the appearance period of the zero voltage driving state MMM to "TM-k" and adjusts the appearance period of the zero voltage driving state HHH to "TH+k". This shortens the appearance period of the zero voltage driving state MMM without changing the total appearance period of the zero voltage driving states HHH and MMM in one control cycle.

[0064] 7 shows a procedure for the control process executed by the control device 50. This control process is repeatedly executed at a predetermined cycle.

[0065] In step S10, the command torque Trq* input from the upper control device, the phase currents flowing through the respective phase windings 11U to 11W, the voltages of the first and second capacitors 21, 22, and the electrical angle θe of the rotating electric machine 10 are acquired. The detection value of the phase current sensor 43 can be used as the phase current. The detection voltage V1r of the first voltage sensor 41 can be used as the voltage of the first capacitor 21, and the detection voltage V2r of the second voltage sensor 42 can be used as the voltage of the second capacitor 22. The detection value of the rotation angle sensor 44 can be used as the electrical angle θe of the rotating electric machine 10.

[0066] In step S11, a command voltage vector Vαβ is calculated based on the acquired command torque Trq*, phase current, and electrical angle θe. In step S12, a sector in which the command voltage vector Vαβ exists and a sub-area within the sector are identified. In steps S11 and S12, the control device 50 functions as the command current setting unit 60, the two-phase conversion unit 61, the deviation calculation units 62a and 62b, the command voltage calculation units 63a and 63b, the fixed coordinate conversion unit 64, and the modulation unit 65 described above in FIG. 2.

[0067] In step S13, a drive pattern consisting of a combination of the drive states of the switches SUH to SWL, QU1 to QW2 is set based on the identified sector and the sub-area in the sector and the acquired detection voltages V1r, V2r. Here, a drive pattern for two control periods is set so as to include two different zero voltage drive states. In this case, a drive pattern is set so as to include at least one of the zero voltage drive state MMM and the remaining zero voltage drive states HHH and LLL. Then, the appearance period of each drive state included in the set drive pattern is set. In this case, the appearance period of each effective voltage drive state in one control period is set based on the length of the voltage vector obtained by decomposing the command voltage vector Vαβ. The remaining period Tz obtained by subtracting the appearance period of each effective voltage drive state from the length TS of one control period is set as the total period of the appearance periods TH, TM, and TL of the zero voltage drive states HHH, MMM, and LLL. The process of step S13 corresponds to the "setting unit".

[0068] In step S14, the appearance period of the zero voltage drive state included in the drive pattern is adjusted. In this embodiment, the appearance period of the zero voltage drive state MMM in one control cycle is adjusted so as to be shorter than the period set by the process in step S13.

[0069] For example, when the command voltage vector Vαβ is in the first region R1 of each sector, a drive pattern including the Mid-Lo drive state and each of the zero voltage drive states MMM and LLL is set. Then, in one control cycle, the appearance period of the zero voltage drive state MMM is set to TM, and the appearance period of the zero voltage drive state LLL is set to TL. In this case, the appearance period of each of the zero voltage drive states MMM and LLL is adjusted so that the appearance period of the zero voltage drive state MMM is "TM-k" and the appearance period of the zero voltage drive state LLL is "TL+k".

[0070] Also, for example, when the command voltage vector Vαβ is in the first region R1 of each sector, a drive pattern including the Hi-Mid drive state and each of the zero voltage drive states HHH and MMM is set. Then, in one control cycle, the appearance period of the zero voltage drive state MMM is set to TM, and the appearance period of the zero voltage drive state HHH is set to TH. In this case, the appearance period of each of the zero voltage drive states HHH and MMM is adjusted so that the appearance period TM of the zero voltage drive state MMM is set to "TM-k" and the appearance period TH of the zero voltage drive state HHH is set to "TH+k". Note that a predetermined value can be used as the adjustment period k.

[0071] When it is determined that the command voltage vector Vαβ exists in the second to fourth regions R2 to R4 of each sector, the process of step S14 does not have to be performed.

[0072] In step S16, switching control is performed based on the drive patterns of the switches SUH-SWL and QU1-QW2 set in steps S10-S14 and the appearance periods of each drive state. The processes in steps S14 and S15 correspond to a "control unit."

[0073] Next, the operation and effect will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is a comparative example in which the process of step S14 is not performed in the switching control of each switch SUH-SWL, QU1-QW2, and Fig. 9 is an example of the switching control of each switch SUH-SWL, QU1-QW2 according to this embodiment. Fig. 8 and Fig. 9 show the transition of each phase voltage.

[0074] 8, the conduction loss of each of the middle switches QU1 to QW2 may be large due to the long appearance period TM of the zero voltage drive state MMM. In this case, there is a concern that the load may be concentrated on each of the middle switches QU1 to QW2.

[0075] Therefore, in this embodiment, in the switching control of each switch SUH-SWL, QU1-QW2, the appearance period of each zero voltage drive state HHH, MMM, LLL included in the drive pattern is adjusted. In this case, it is possible to control the conduction loss occurring in each switch SUH-SWL, QU1-QW2 within an adjustable range of the appearance period of each zero voltage drive state HHH, MMM, LLL. Therefore, it is possible to suppress the occurrence of a situation in which the load is concentrated on each middle switch QU1-QW2.

[0076] In the control example of Fig. 9, the appearance period of each of the zero voltage driving states HHH and MMM is adjusted so that the appearance period of the zero voltage driving state MMM is shortened by the adjustment period k from the appearance period TM of the comparative example. In this case, the conduction loss of each of the middle switches QU1 to QW2 is reduced compared to the comparative example. This makes it possible to avoid the occurrence of losses concentrated in each of the middle switches QU1 to QW2, and to appropriately suppress the occurrence of a situation in which the load is concentrated on each of the middle switches QU1 to QW2.

[0077] The appearance period of the zero voltage driving state HHH is extended by the amount of the shortened appearance period of the zero voltage driving state MMM. This makes it possible to shorten the appearance period of the zero voltage driving state MMM without changing the total appearance period of the zero voltage driving states HHH and MMM.

[0078] <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 adjustment unit 66 adjusts the appearance period of the zero voltage drive states HHH, MMM, and LLL, taking into consideration the difference in switching loss that occurs during switching control of each of the switches SUH to SWL, and QU1 to QW2.

[0079] In a state in which a current flows in each phase from a first end of the winding, which is connected to the switch of the inverter 30, to a second end of the winding, which is connected to the motor neutral point, the upper arm switches SUH, SVH, SWH and the first middle switches QU1, QV1, QW1 are switched in a hard switching manner. The lower arm switches SUL, SVL, SWL and the second middle switches QU2, QV2, QW2 are switched in a soft switching manner. In this case, the switching loss of the upper arm switches SUH, SVH, SWH and the first middle switches QU1, QV1, QW1 is greater than the switching loss of the lower arm switches SUL, SVL, SWL and the second middle switches QU2, QV2, QW2.

[0080] On the other hand, in a state where a current flows from the second end to the first end of the winding in each phase, the upper arm switches SUH, SVH, SWH and the first middle switches QU1, QV1, QW1 are switched in a soft switching manner. Also, the lower arm switches SUL, SVL, SWL and the second middle switches QU2, QV2, QW2 are switched in a hard switching manner. In this case, the switching loss of the lower arm switches SUL, SVL, SWL and the second middle switches QU2, QV2, QW2 is greater than the switching loss of the upper arm switches SUH, SVH, SWH and the first middle switches QU1, QV1, QW1.

[0081] 10 to 13, it will be explained that the switching mode of each switch SUH, QU1 is hard switching and the switching mode of each switch SUL, QU2 is soft switching, using as an example a situation in which a current flows from the first end to the second end of U-phase winding 11U. In Figures 10 to 13, the solid line indicates the current path before the dead time, the dashed line indicates the current path during the dead time, and the dashed dotted line indicates the current path after the dead time.

[0082] FIG. 10 shows the current path when the U-phase voltage changes from level H to level M. In this case, a current flows through the U-phase upper arm switch SUH before the dead time when the U-phase upper arm switch SUH and the U-phase second middle switch QU2 are turned off. As a result, when the U-phase upper arm switch SUH is turned off and the collector-emitter voltage of the U-phase upper arm switch SUH starts to rise, a turn-off loss occurs. During the dead time, the U-phase second diode DU2 is conductive. As a result, the U-phase second middle switch QU2 is turned on with the collector-emitter voltage of the U-phase second middle switch QU2 reduced to near zero. This suppresses the occurrence of turn-on loss in the U-phase second middle switch QU2.

[0083] FIG. 11 shows a current path when the U-phase voltage changes from level M to level H. In this case, a current flows through the U-phase second middle switch QU2 before the dead time when the U-phase upper arm switch SUH and the U-phase second middle switch QU2 are turned off. During the dead time, the U-phase second diode DU2 is conductive. As a result, the U-phase second middle switch QU2 is turned off in a state where the collector-emitter voltage of the U-phase second middle switch QU2 is reduced to near zero. Therefore, the occurrence of turn-off loss in the U-phase second middle switch QU2 is suppressed. During the dead time, the collector-emitter voltage in the off state is applied to the U-phase upper arm switch SUH. As a result, when the U-phase upper arm switch SUH is turned on and a current starts to flow through the U-phase upper arm switch SUH, a turn-on loss occurs.

[0084] That is, in the situation shown in FIG. 10 and FIG. 11, the switching mode of the U-phase upper arm switch SUH is hard switching, and the switching mode of the U-phase second middle switch QU2 is soft switching.

[0085] FIG. 12 shows a current path when the U-phase voltage changes from level M to level L. In this case, a current flows through the U-phase first middle switch QU1 before the dead time when the U-phase first middle switch QU1 and the U-phase lower arm switch SUL are turned off. As a result, when the U-phase first middle switch QU1 is turned off and the collector-emitter voltage of the U-phase first middle switch QU1 starts to rise, a turn-off loss occurs. During the dead time, the U-phase lower arm diode DUL is conductive. As a result, the U-phase lower arm switch SUL is turned on with the collector-emitter voltage of the U-phase lower arm switch SUL reduced to near zero. This suppresses the occurrence of a turn-on loss in the U-phase lower arm switch SUL.

[0086] FIG. 13 shows a current path when the U-phase voltage changes from level L to level M. In this case, a current flows through the U-phase lower arm switch SUL before the dead time when the U-phase first middle switch QU1 and the U-phase lower arm switch SUL are turned off. During the dead time, the U-phase lower arm diode DUL is conductive. As a result, the U-phase lower arm switch SUL is turned off in a state where the collector-emitter voltage of the U-phase lower arm switch SUL is reduced to approximately zero. Therefore, the occurrence of turn-off loss in the U-phase lower arm switch SUL is suppressed. During the dead time, the collector-emitter voltage in the off state is applied to the U-phase first middle switch QU1. As a result, when the U-phase first middle switch QU1 is turned on and a current starts to flow through the U-phase first middle switch QU1, a turn-on loss occurs.

[0087] That is, in the situation shown in FIG. 12 and FIG. 13, the switching mode of the U-phase first middle switch QU1 is hard switching, and the switching mode of the U-phase lower arm switch SUL is soft switching.

[0088] As described above, in each phase, depending on the direction of the current flowing through the winding, either the upper arm switch and the first middle switch or the lower arm switch and the second middle switch will be in the hard switching mode, and the other will be in the soft switching mode. In this case, it is considered that the switch in the soft switching mode among the upper arm switches SUH, SVH, SWH of each phase and the lower arm switches SUL, SVL, SWL of each phase has a margin for extending the period during which the zero voltage drive state appears, compared to the switch in the hard switching mode.

[0089] Therefore, in this embodiment, the adjustment unit 66 adjusts the appearance periods of each of the zero voltage driving states HHH, MMM, and LLL by making different the first adjustment period k1 for the zero voltage driving state HHH as the "first driving state" and the second adjustment period k2 for the zero voltage driving state LLL as the "second driving state".

[0090] The process performed by the adjustment unit will be specifically described with reference to Fig. 14. Fig. 14 shows a drive pattern for four control cycles. The appearance period of each of the zero voltage drive states HHH, MMM, and LLL is shown surrounded by a dashed line. Below each period of the zero voltage drive states HHH, MMM, and LLL, the appearance period after adjustment in this embodiment is shown in comparison with the appearance period after adjustment in the first embodiment.

[0091] In the first control period TS1 and the second control period TS2, a drive pattern including the Mid-Lo drive state and each of the zero voltage drive states MMM and LLL is set. In this case, the adjustment unit 66 shortens the appearance period TM of the zero voltage drive state MMM set by the modulation unit 65 by the second adjustment period k2, and extends the appearance period TL of the zero voltage drive state LLL set by the modulation unit 65 by the second adjustment period k2.

[0092] In the third control period TS3 and the fourth control period TS4, a drive pattern including the Hi-Mid drive state and each of the zero voltage drive states HHH and MMM is set. In this case, the adjustment unit 66 shortens the appearance period TM of the zero voltage drive state MMM set by the modulation unit 65 by the first adjustment period k1, and extends the appearance period TH of the zero voltage drive state HHH set by the modulation unit 65 by the first adjustment period k1.

[0093] In other words, the adjustment unit 66 shortens the appearance period of the zero voltage driving state MMM by "2×k1+2×k2" over four control cycles, and extends the total period of the appearance periods of the other zero voltage driving states HHH, LLL by "2×k1+2×k2".

[0094] The adjustment unit 66 determines the direction of each phase current. Here, in each phase, the direction in which the current flows from the first end to the second end of the winding is positive, and the direction in which the current flows from the second end to the first end of the winding is negative. When the adjustment unit 66 determines that the direction of the phase current in the phase in which the phase current is the largest among the phases is positive, the adjustment unit 66 sets the second adjustment period k2 to a period longer than the first adjustment period k1. On the other hand, when the adjustment unit 66 determines that the direction of the phase current in the phase in which the phase current is the largest among the phases is negative, the adjustment unit 66 sets the first adjustment period k1 to a period longer than the second adjustment period k2. As a result, the appearance periods of the zero voltage driving states HHH, MMM, and LLL are adjusted so that the first adjustment period k1 and the second adjustment period k2 are different from each other.

[0095] In this embodiment, in view of the fact that the switches whose switching mode is the soft switching mode have the margin for extending the appearance period of the zero voltage drive state, the adjustment unit 66 can lengthen the shortened period of the appearance period of the zero voltage drive state MMM compared to the first embodiment. That is, the adjustment unit 66 can adjust the appearance periods of the zero voltage drive states HHH, MMM, and LLL so that the total shortened period of the appearance period of the zero voltage drive state MMM in four control cycles (corresponding to 2×k1+2×k2) is longer than the first embodiment (corresponding to 4×k).

[0096] Fig. 15 shows the procedure of the control executed by the control device 50. This control is repeatedly executed at a predetermined cycle. In Fig. 15, the same processes as those shown in Fig. 7 are denoted by the same reference numerals for convenience.

[0097] In step S13, a drive pattern is set based on the identified sector and the sub-area within the sector. Here, drive patterns for four control periods are set so as to include each of the zero voltage drive states HHH, MMM, and LLL. Then, the process proceeds to step S20.

[0098] In step S20, the phase having the maximum phase current is identified based on the acquired phase current. In step S21, it is determined whether the direction of the current flowing through the identified phase is positive based on the acquired phase current. If the determination in step S21 is positive, the process proceeds to step S22. On the other hand, if the determination in step S21 is negative, the process proceeds to step S23.

[0099] In step S22, the second adjustment period k2 is set to a period longer than the first adjustment period k1. As the first and second adjustment periods k1 and k2, it is possible to use periods that are predetermined so that the second adjustment period k2 is longer than the first adjustment period k1.

[0100] In step S23, the first adjustment period k1 is set to a period longer than the second adjustment period k2. The first and second adjustment periods k1 and k2 may be predetermined so that the first adjustment period k1 is longer than the second adjustment period k2.

[0101] Fig. 16 shows a comparison of the power loss generated when switching control is performed between this embodiment (right bar graph) and the first embodiment (left bar graph). Fig. 16 compares the power loss generated in each of the U-phase switches SUH, SUL, QU1, and QU2 when a current flows from the first end to the second end of the U-phase winding 11U.

[0102] By shortening the duration of the zero voltage drive state MMM, the conduction loss of each of the middle switches QU1 and QU2 is reduced. Therefore, in the first embodiment, the power loss of the U-phase first middle switch QU1 is reduced to the same level as that of the U-phase upper arm switch SUH.

[0103] When a current flows from the first end to the second end of the U-phase winding 11U, the switching mode of the U-phase lower arm switch SUL becomes soft switching. In this case, the power loss generated in the U-phase lower arm switch SUL has a margin with respect to the reference value A. Note that the reference value A is a value used as a reference when considering the magnitude of the power loss generated when switching control is performed, and is, for example, a value smaller than the allowable power loss.

[0104] In the first embodiment, the conduction loss of each middle switch QU1, QU2 is reduced and the occurrence of a situation in which the load is concentrated on each middle switch QU1, QU2 is suppressed, but the loss generated in the U-phase first middle switch QU1 is higher than the reference value A. In addition, the loss generated in the U-phase upper arm switch SUH is higher than the reference value A.

[0105] 16, in consideration of the fact that the loss generated in the U-phase lower arm switch SUL has a margin with respect to the reference value A, the adjustment periods k1 and k2 are set so that the total shortened period of the zero voltage drive state MMM is longer than that in the first embodiment. In this case, the conduction loss of the U-phase first middle switch QU1 is reduced compared to the first embodiment. As a result, the loss generated in the U-phase first middle switch QU1 is set within the reference value A.

[0106] In this embodiment, the adjustment periods k1 and k2 are set such that k1 < k2. In FIG. 16, the first adjustment period k1 is shorter than the adjustment period k of the first embodiment. As a result, the conduction loss of the U-phase upper arm switch SUH is reduced compared to the first embodiment. As a result, the loss generated in the U-phase upper arm switch SUH is within the reference value A. Also, although the second adjustment period k2 is longer than the adjustment period k of the first embodiment and the conduction loss of the U-phase lower arm switch SUL is increased compared to the first embodiment, it is within the reference value A.

[0107] According to the present embodiment described in detail above, in addition to shortening the appearance period of the zero voltage drive state MMM, the extension periods of the appearance periods of the remaining zero voltage drive states HHH and LLL are adjusted. Thereby, it is possible to realize switching control suitable for dispersing the conduction losses generated in each of the switches SUH to SWL and QU1 to QW2.

[0108] In the switching control, based on the currents flowing through the phase windings 11U, 11V, and 11W, either one of the extension periods in the zero voltage drive states HHH and LLL is made shorter than the other extension period. Thereby, in consideration of the difference in the switching losses generated during the switching control of each of the switches SUH to SWL and QU1 to QW2, it becomes possible to appropriately determine the extension periods of the zero voltage drive states HHH and LLL. Therefore, it is possible to realize switching control suitable for dispersing the conduction losses generated in each of the switches SUH to SWL and QU1 to QW2.

[0109] <Other Embodiments> Note that each of the above embodiments may be implemented with the following modifications.

[0110] In the first embodiment, the adjustment unit 66 may adjust the appearance period of each of the zero voltage driving states HHH, MMM, and LLL so as to shorten the appearance period of the other zero voltage driving states HHH and LLL, instead of shortening the appearance period of the zero voltage driving state MMM. In other words, one of the zero voltage driving states HHH and LLL may be set as a "specific driving state". In this case, for example, in step S14 of FIG. 7, the appearance period of each of the zero voltage driving states MMM and LLL may be adjusted so that the appearance period of the zero voltage driving state MMM is set to "TM+k" and the appearance period of the zero voltage driving state LLL is set to "TL-k". Also, for example, the appearance period of each of the zero voltage driving states HHH and MMM may be adjusted so that the appearance period TM of the zero voltage driving state MMM is set to "TM+k" and the appearance period TH of the zero voltage driving state HHH is set to "TH-k".

[0111] In the first embodiment, the adjustment unit 66 may select which of the appearance periods of the zero voltage drive states HHH, MMM, and LLL to shorten based on the temperatures of the switches SUH-SWL, QU1-QW2. To implement this, in step S14 of FIG. 7, the zero voltage drive state in which the switch with the highest temperature among the upper arm switches SUH-SWH, the middle switches QU1-QW2, and the lower arm switches SUL-SWL is turned on may be selected as the specific drive state. Then, the appearance period of the zero voltage drive states HHH, MMM, and LLL may be adjusted so that the appearance period of the selected specific drive state is shortened by the adjustment period k. The specific drive state can be selected using a temperature calculated based on the detection value of the temperature sensor 45.

[0112] According to this embodiment, in the switching control, the period during which the zero voltage drive state in which the switch with the highest temperature among the upper arm switches SUH to SWH, the middle switches QU1 to QW2, and the lower arm switches SUL to SWL is turned on is shortened. This makes it possible to appropriately reduce the conduction loss occurring in the switches with concentrated loads. Therefore, it is possible to perform switching control suitable for avoiding the occurrence of a situation in which the load is concentrated on a specific switch among the switches SUH to SWL, QU1 to QW2.

[0113] In the first and second embodiments, the modulation unit 65 may adjust the appearance period of each of the zero voltage drive states HHH, MMM, and LLL when setting the appearance period of the drive states of each of the switches SUH to SWL, QU1 to QW2. For example, the modulation unit 65 can set the appearance period of each drive state included in the drive pattern using correspondence information (specifically, map information or formula information) in which the command voltage vector Vαβ is associated with the appearance period of each of the switches SUH to SWL, QU1 to QW2. In this case, it is possible to use, as the correspondence information, information in which the appearance period of each of the zero voltage drive states HHH, MMM, and LLL is adjusted in consideration of the conduction loss occurring in each of the switches SUH to SWL, QU1 to QW2.

[0114] In this embodiment, the control device 50 does not need to include the adjustment unit 66. In addition, the process of step S14 in FIG.

[0115] In the first embodiment, the adjustment unit 66 is not limited to adjusting the appearance period of each of the zero voltage driving states HHH, MMM, and LLL using each predetermined adjustment period k, and may variably set the adjustment period k. For example, the adjustment unit 66 may set the adjustment period k longer in the phase in which the phase current has the largest magnitude among the phases when the phase current is large than when the phase current is small. The adjustment unit 66 can use the detection value of the phase current sensor 43 as each phase current.

[0116] Also, for example, when the temperature of each of the switches SUH-SWL, QU1-QW2 is high, the adjustment unit 66 may set the adjustment period k longer than when the temperature of each of the switches SUH-SWL, QU1-QW2 is low. The adjustment unit 66 can use the detection value of the temperature sensor 45 as the temperature of each of the switches SUH-SWL, QU1-QW2. Note that in the second embodiment, it is also possible to variably set each of the adjustment periods k1, k2 based on at least one of the phase currents and the temperatures of each of the switches SUH-SWL, QU1-QW2.

[0117] According to this embodiment, the appearance periods of the zero voltage drive states HHH, MMM, and LLL can be appropriately adjusted according to the loads on the switches SUH to SWL, and QU1 to QW2.

[0118] 7, it is possible to set the adjustment period k to the same length as the appearance period TM set by the process of step S13. In this case, the appearance period of the zero voltage driving state MMM in one control cycle is set to "0".

[0119] In step S14, when the appearance period of the zero voltage drive state MMM in one control cycle is adjusted to "0", the drive pattern may be adjusted so that an effective voltage drive state does not appear in which the phase voltage of at least one of the phases is set to level M. For example, when a command voltage vector exists in the first sector, the drive pattern and the appearance period of each drive state may be adjusted so that switching control is performed by each drive state HHL, HLL, HHH, and LLL.

[0120] 15, the total period of the adjustment periods k1 and k2 can be set to four times the appearance period TM set by the process of step S13. In this case, the appearance period of the zero voltage driving state MMM in four control cycles is set to "0".

[0121] In steps S22 and S23, when the occurrence period of the zero voltage drive state MMM in four control cycles is adjusted to "0", the drive pattern may be adjusted so that an effective voltage drive state in which the phase voltage of at least one of the phases is set to level M does not occur.

[0122] In the switching control of each of the switches SUH to SWL and QU1 to QW2, when a predetermined execution condition is met, the appearance period of each of the zero voltage drive states HHH, MMM, and LLL may be adjusted.

[0123] Specifically, the control device 50 may perform a control shown in Fig. 17 instead of the control shown in Fig. 7. In this control, after the process of step S10, the process proceeds to step S30.

[0124] In step S30, it is determined whether a predetermined execution condition is satisfied. The execution condition is a condition that makes it possible to know that the inverter 30 is in an overheated state. For example, the execution condition is a condition that a determination parameter value exceeds a threshold value. For example, the determination parameter value is a value calculated based on the command torque Trq*, the rotor rotation speed calculated based on the electrical angle θe, the detection value of the temperature sensor 45, etc.

[0125] If the determination in step S30 is affirmative, the process proceeds to step S11. On the other hand, if the determination in step S30 is negative, the process proceeds to step S31. In step S31, normal control is performed. In normal control, switching control is performed without adjusting the appearance periods of the zero voltage driving states HHH, MMM, and LLL by the adjustment unit 66.

[0126] In the second embodiment, the total shortened period of the appearance period of the zero voltage drive state MMM in four control cycles (corresponding to 2×k1+2×k2) does not need to be longer than that in the first embodiment (corresponding to 4×k). Even in this case, it is possible to adjust the extension period of the appearance period of each of the zero voltage drive states HHH and LLL.

[0127] The middle switches QU1 to QW2 of each phase may be configured with their collectors connected to each other. Taking the U phase as an example, the U-phase first middle switch QU1 and the U-phase second middle switch QU2 may be configured with their collectors connected to each other. The emitter of the U-phase second middle switch QU2 may be connected to a connection point between the U-phase upper arm switch SUH and the U-phase lower arm switch SUL. The emitter of the U-phase first middle switch QU1 may be connected to the capacitor neutral point O. In this case, the U-phase first and second diodes DU1 and DU2 are arranged to be conductive in the opposite direction to that in the first embodiment.

[0128] In this configuration, the U-phase upper arm switch SUH and the U-phase second middle switch QU2 are turned on, and the U-phase lower arm switch SUL and the U-phase first middle switch QU1 are turned off, so that the U-phase voltage is set to level H. Also, the U-phase lower arm switch SUL and the U-phase first middle switch QU1 are turned on, and the U-phase upper arm switch SUH and the U-phase second middle switch QU2 are turned off, so that the U-phase voltage is set to level L.

[0129] In this case, when a current flows from the first end to the second end of the winding in each phase, the upper arm switches SUH, SVH, SWH and the second middle switches QU2, QV2, QW2 are switched in a hard switching manner, and the lower arm switches SUL, SVL, SWL and the first middle switches QU1, QV1, QW1 are switched in a soft switching manner.

[0130] In addition, in a state in which a current flows from the second end to the first end of each phase, the upper arm switches SUH, SVH, SWH and the second middle switches QU2, QV2, QW2 are switched in a soft switching manner, and the lower arm switches SUL, SVL, SWL and the first middle switches QU1, QV1, QW1 are switched in a hard switching manner.

[0131] A reverse blocking IGBT (RB-IGBT) may be used as the middle switch for each phase.

[0132] The semiconductor switches constituting the inverter are not limited to IGBTs, but may be, for example, N-channel MOSFETs. In this case, the high-potential terminal of the switch is the drain, and the low-potential terminal is the source. Each switch also has a corresponding body diode.

[0133] The inverter is not limited to the inverter shown in FIG. 1, but may be another inverter such as a neutral point clamp type inverter.

[0134] The power storage unit connected to the inverter is not limited to a capacitor, and may be a rechargeable battery.

[0135] The rotating electric machine is not limited to one in which the windings of each phase are star-connected, and may be one in which the windings are delta-connected.

[0136] The inverter, the rotating electric machine, and the control device may be mounted on a moving object such as an aircraft or a ship, without being limited to a vehicle. If the moving object is an aircraft, the rotating electric machine serves as the power source for the aircraft to fly, and if the moving object is a ship, the rotating electric machine serves as the power source for the ship to navigate. Furthermore, the inverter, the rotating electric machine, and the control device may be mounted on a moving object such as an aircraft, without being limited to a vehicle.

[0137] The control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit and the method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and the method described in the present disclosure may be realized by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by the computer. [Explanation of symbols]

[0138] 10... rotating electric machine, 11U to 11W... each phase winding, 21, 22... first and second capacitors, 30... inverter, 50... control device.

Claims

1. A first storage unit (21) and a second storage unit (22) connected in series; A rotating electric machine (10) having three-phase armature windings (11U, 11V, 11W); a three-level inverter (30) having switches (SUH to SWL, QU1 to QW2) electrically connecting the armature winding in each phase to any of a positive electrode side of the first storage unit, a neutral point between the negative electrode side of the first storage unit and the positive electrode side of the second storage unit, and a negative electrode side of the second storage unit; a setting unit that sets a drive pattern including a combination of drive states of the switches and an appearance period of each of the drive states based on a command voltage for controlling a control amount of the rotary electric machine to a command value; a control unit that performs the switching control based on the set drive pattern and the appearance period of each of the drive states, three different drive states in which the armature winding of each phase is electrically connected to the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit are defined as zero-voltage drive states; the setting unit sets the drive pattern to include at least two of the zero voltage drive states; The control unit adjusts an appearance period of each of the zero voltage drive states included in the drive pattern in the switching control.

2. The control unit is 2. The control device for a three-level inverter according to claim 1, wherein, in the switching control, an appearance period of a specific drive state, which is any one of the zero voltage drive states included in the drive pattern, is adjusted so as to be shorter than a period set by a setting unit.

3. The three-level inverter includes the following switches: an upper arm switch (SUH, SVH, SWH) for electrically connecting the armature winding to a positive electrode side of the first power storage unit, in each phase; In each phase, a middle switch (QU1, QU2, QV1, QV2, QW1, QW2) electrically connects the armature winding to the neutral point; a lower arm switch (SUL, SVL, SWL) for electrically connecting the armature winding to a negative electrode side of the second power storage unit, 3. The control device for a three-level inverter according to claim 2, wherein the specific drive state is the zero voltage drive state in which the armature windings of each phase are electrically connected via the middle switches of each phase.

4. the setting unit sets the drive pattern to include three different zero voltage drive states; The control unit, in the switching control, The appearance period of the specific drive state is shortened compared to the case set by the setting unit, extending a total period of an appearance period of a first drive state, which is the zero-voltage drive state in which the armature windings of each phase are electrically connected via the upper arm switches of each phase, and an appearance period of a second drive state, which is the zero-voltage drive state in which the armature windings of each phase are electrically connected via the lower arm switches of each phase, by an amount corresponding to the shortening of the appearance period of the specific drive state; The control device for a three-level inverter according to claim 3, wherein the appearance period of each of the zero voltage drive states is adjusted so that an extension period of the appearance period of the first drive state and an extension period of the appearance period of the second drive state are different from each other.

5. 5. The control device for a three-level inverter according to claim 4, wherein, in the switching control, the control unit determines, based on the current flowing through each of the armature windings, which of the extension periods of the appearance period of the first drive state and the extension period of the appearance period of the second drive state to be made shorter than the other extension period.

6. The three-level inverter includes the following switches: an upper arm switch (SUH, SVH, SWH) for electrically connecting the armature winding to a positive electrode side of the first power storage unit, in each phase; In each phase, a middle switch (QU1, QU2, QV1, QV2, QW1, QW2) electrically connects the armature winding to the neutral point; a lower arm switch (SUL, SVL, SWL) for electrically connecting the armature winding to a negative electrode side of the second power storage unit, The control unit, in the switching control, selecting, as the specific driving state, the zero voltage driving state in which the switch having the highest temperature among the upper arm switch, the middle switch, and the lower arm switch is turned on; The control device for a three-level inverter according to claim 2 , further comprising: adjusting an appearance period of each of the zero voltage drive states so that the appearance period of the selected specific drive state is shorter than that set by a setting unit.

7. A first storage unit (21) and a second storage unit (22) connected in series; A rotating electric machine (10) having three-phase armature windings (11U, 11V, 11W); a three-level inverter (30) having switches (SUH to SWL, QU1 to QW2) for electrically connecting the armature winding to any one of a positive electrode side of the first storage unit, a neutral point between the negative electrode side of the first storage unit and the positive electrode side of the second storage unit, and a negative electrode side of the second storage unit, in each phase; A computer (51), A program for causing the computer to execute switching control of each of the switches, a setting step of setting a drive pattern including a combination of drive states of the switches and an appearance period of each of the drive states based on a command voltage for controlling a control amount of the rotary electric machine to a command value; a control step of performing the switching control based on the set drive pattern and the duration of each drive state; three different drive states in which the armature winding of each phase is electrically connected to the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit are defined as zero-voltage drive states; In the setting step, the drive pattern is set so as to include at least two of the zero voltage drive states; A program for adjusting, in the control step, an appearance period of each of the zero voltage drive states included in the drive pattern in the switching control.

Images