3-level inverter control device, program, and 3-level inverter control method

Abstract

To provide a control device and a program for a 3-level inverter, which can enhance controllability of a voltage of a power storage unit.SOLUTION: A control device 40 is applied to a system provided with first and second capacitors 21 and 22, a rotary electric machine 10, and an inverter 30. The control device 40 comprises: a selection unit that selects a drive pattern combining driving states of switches SUH-SWL and QU-QW on the basis of an instruction voltage; and a control unit that performs switching control on the basis of the drive pattern. The two different driving states in which three line voltages are equal and the directions of current flowing through a neutral point O are opposite to each other are set as specific driving states. The selection unit selects the drive pattern so as to generate a period of each specific driving state within one switching period on the basis of the instruction voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] A control device that turns on and off a switch of a three-level inverter is known in the art. This control device turns on and off the switch by space vector modulation control.

[0003] A first power storage unit and a second power storage unit are connected in series to the DC side of the three-level inverter. The control device performs switching control so that the voltage of the first power storage unit and the voltage of the second power storage unit are within a predetermined range. This prevents an overvoltage from being applied to the switch. An example of such a control device is the control device disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-37592 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a concern that the controllability of the voltage of each power storage unit may decrease due to a long fluctuation period in the voltage of the first power storage unit and the voltage of the second power storage unit.

[0006] The present invention has been made in consideration of the above circumstances, and a main object of the present invention is to provide a control device and program for a three-level inverter that can improve controllability of the voltage of a power storage unit. [Means for solving the problem]

[0007] The present invention relates to a first power storage unit and a second power storage unit connected in series; A rotating electric machine having three phase windings; a three-level inverter having three-phase switches connecting the windings of each phase in the rotating electric machine 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, a selection unit that selects a drive pattern, which is a combination of drive states of the switches of each phase in one switching period, based on a command voltage for controlling a control amount of the rotating electric machine to a command value; A switch control unit that performs switching control of the switch based on the selected drive pattern, Two different driving states in which the three line voltages of the winding are equal and the directions of the currents flowing through the neutral point are opposite to each other are defined as specific driving states; The selection unit selects the drive pattern based on the command voltage so that a period during which each of the specific drive states occurs within one switching period.

[0008] According to the present invention, a drive pattern, which is a combination of the drive states of the switches of each phase in one switching period, is selected based on the command voltage. Here, the drive pattern is selected based on the command voltage so that a period in which each specific drive state occurs within one switching period. Then, switching control of the switches is performed based on the selected drive pattern. In this case, the voltages of the power storage units change in the opposite directions to each other during a period in a switching period in which one of the specific drive states occurs and a period in a switching period in which the other drive state occurs. Therefore, compared with a case in which only a period in which one of the specific drive states occurs within a switching period, the voltage of each power storage unit can be changed at short intervals, and the change period of the voltage of each power storage unit can be shortened. As a result, the controllability of the voltage of each power storage unit can be improved. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a configuration diagram of a motor control system according to a first embodiment. [Diagram 2] FIG. 4 is a functional block diagram of a process performed by a control device. [Diagram 3] Diagram showing vector space. [Figure 4] FIG. 1 is a diagram used to explain voltage vectors. [Diagram 5] FIG. 13 is a diagram showing a current path during a period in which the switch is in a driving state HMM. [Figure 6] FIG. 13 is a diagram showing a current path during a period when the switch is in a drive state MLL. [Figure 7] FIG. 4 is a diagram showing an example of a drive pattern of a switch. [Figure 8] 4 is a flowchart showing a control process performed by the control device. [Figure 9] FIG. 4 is a diagram used to explain a specific range and a voltage control range. [Figure 10] 4 is a time chart showing an example of switching control. [Figure 11] FIG. 11 is a configuration diagram of a motor control system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First Embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a control device according to the present invention will now be described with reference to the drawings. In this embodiment, the control device is mounted on an electrically powered vehicle such as an electric vehicle or a hybrid vehicle.

[0011] As shown in Fig. 1, the motor control system includes a rotating electric machine 10, a battery 20, an inverter 30, and a control device 40. The rotating electric machine 10 is an in-vehicle main engine capable of transmitting power to drive wheels (not shown). In this embodiment, the rotating electric machine 10 is a three-phase synchronous machine, and includes a U-phase winding 11U, a V-phase winding 11V, and a W-phase winding 11W that are star-connected as stator windings. The phase windings 11U, 11V, and 11W are arranged with a 120° electrical angle offset. The rotating electric machine 10 is, for example, a permanent magnet synchronous machine.

[0012] The battery 20 is electrically connected to the rotating electric machine 10 via the inverter 30. In this embodiment, the battery 20 is, for example, a battery pack configured as a series connection of battery cells serving as single cells. As the battery cells, for example, secondary batteries such as lithium ion batteries can be used. The terminal voltage of the battery 20 is, for example, 100 V or more.

[0013] The inverter 30 is a power conversion circuit that converts DC power supplied from the battery 20 into three-phase AC power by switching operation and supplies the converted AC power to the rotating electric machine 10. A first capacitor 21 and a second capacitor 22 are provided on the battery 20 side of the inverter 30 as a power storage unit. The first capacitor 21 and the second capacitor 22 are connected in series. The 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.

[0014] 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. A voltage-controlled semiconductor switching element, specifically an IGBT, is used as each of the switches SUH to SWL. Therefore, the high potential side terminal of each of the switches SUH to SWL is a collector, and the low potential side terminal is an emitter. The switches SUH, SVH, SWH, SUL, SVL, SWL are connected in inverse parallel to corresponding freewheel diodes DUH, DVH, DWH, DUL, DVL, DWL.

[0015] The emitter of the U-phase upper arm switch SUH is connected to the collector of the U-phase lower arm switch SUL. The 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. The 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. The 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. The second ends of the respective phase windings 11U, 11V, 11W are connected to each other.

[0016] The collectors of each of the upper arm switches SUH to SWH are connected by a positive bus bar 31 such as a bus bar. The positive bus bar 31 is connected to the positive terminal of the 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 neutral point O. The emitters of each of the lower arm switches SUL to SWL are connected by a negative bus bar 32 such as a bus bar. The negative bus bar 32 is connected to the negative terminal of the battery 20 and a second end of the second capacitor 22.

[0017] The inverter 30 includes clamp switches QU, QV, and QW that conduct and cut off current in both directions. In this embodiment, voltage-controlled semiconductor switching elements, specifically IGBTs, are used as the switches that make up the clamp switches QU to QW. Each switch that makes up the clamp switches QU to QW has a corresponding freewheel diode DU, DV, or DW.

[0018] Specifically, taking the U phase as an example, the two switches constituting the U-phase clamp switch QU have their emitters connected to each other. Of the switches constituting the U-phase clamp switch QU, one collector is connected to the connection point between the U-phase upper arm switch SUH and the U-phase lower arm switch SUL, and the other collector is connected to the neutral point O. Note that the U-, V-, and W-phase clamp switches QU to QW allow bidirectional current flow when turned on, and block bidirectional current flow when turned off. The U-, V-, and W-phase clamp switches QU to QW may be configured with their collectors connected to each other. Reverse blocking IGBTs (RB-IGBTs) may be used as the U-, V-, and W-phase clamp switches QU to QW.

[0019] The motor control system includes a first voltage sensor 41, a second voltage sensor 42, a phase current sensor 43, and a rotation angle sensor 44. The first voltage sensor 41 detects the voltage of the first capacitor 21. The second voltage sensor 42 detects the 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. Note that it is sufficient for the phase current sensor 43 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 detection values ​​of the sensors 41 to 44 are input to the control device 40.

[0020] The control device 40 is mainly composed of a microcomputer having a CPU and various memories. The functions provided by the microcomputer 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 is provided by an electronic circuit that is hardware, it can be provided by a digital circuit including a large number of logic circuits, or by an analog circuit. For example, the microcomputer executes a program stored in a non-transitory tangible storage medium as a storage unit provided in the microcomputer. The program includes, for example, a program of a process shown in FIG. 8, etc. The program is executed to execute a method corresponding to the program. The storage unit is, for example, a non-volatile memory. The program stored in the storage unit can be downloaded and updated via a communication network such as the Internet, for example, OTA (Over The Air), etc.

[0021] The control device 40 controls the control amount of the rotating electric machine 10 to a command value, and performs switching control to turn on and off each of the switches SUH-SWL, QU-QW of the inverter 30. Here, the switching control of the control device 40 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.

[0022] The control device 40 includes a command current setting unit 50. The command current setting unit 50 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 50 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.

[0023] The control device 40 includes a two-phase conversion unit 51. The two-phase conversion unit 51 converts the U-, V-, and W-phase currents in a 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 U-, V-, and W-phase currents flowing through the respective phase windings 11U, 11V, and 11W and the electrical angle θe of the rotating electric machine 10. The two-phase conversion unit 51 can use detection values ​​of the phase current sensor 43 as the respective phase currents, and can use detection values ​​of the rotation angle sensor 44 as the electrical angle θe.

[0024] The control device 40 includes a d-axis deviation calculation unit 52a and a q-axis deviation calculation unit 52b. The d-axis deviation calculation unit 52a calculates a 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 52b calculates a q-axis current deviation ΔIq by subtracting the q-axis current Iqr from the q-axis command current Iq*.

[0025] The control device 40 includes a d-axis command voltage calculation unit 53a and a q-axis command voltage calculation unit 53b. The d-axis command voltage calculation unit 53a 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 53b 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 53a and the q-axis command voltage calculation unit 53b may be, for example, proportional-integral control.

[0026] The control device 40 includes a fixed coordinate conversion unit 54. The fixed coordinate conversion unit 54 converts the d- and q-axis command voltages Vd and Vq in the two-phase rotating coordinate system into α- and β-axis command voltages Vα and Vβ in the two-phase fixed coordinate system based on the d- and q-axis command voltages Vd and Vq and the electrical angle θe output from the d- and q-axis command voltage calculation units 53a and 53b. The fixed coordinate conversion unit 54 can use the detection value of the rotation angle sensor 44 as the electrical angle θe.

[0027] The control device 40 includes a modulation unit 55. The modulation unit 55 sets a voltage vector determined by α, β-axis command voltages Vα, Vβ as a command voltage vector Vαβ for controlling the control amount of the rotary electric machine 10 to a command value, and specifies a sector in which the command voltage vector Vαβ exists and an existence area within the sector. The sectors divide a vector space in which the command voltage vector Vαβ can exist into six with respect to the deflection angle of the command voltage vector Vαβ. The deflection angle of the command voltage vector Vαβ is an angle between the command voltage vector Vαβ and the U-phase axis, and is specifically an electrical angle θe. The sign of the electrical angle θe is positive in the leftward (counterclockwise) direction. FIG. 3 shows first to sixth sectors that divide the vector space into six. In the vector space, the U-, V-, and W-phase axes are arranged with an electrical angle shift of 120° each. Each sector is an area sandwiched between two-phase axes having an electrical angle difference of 60° from each other. In FIG. 3, the area indicating the first sector is dot-hatched.

[0028] The first to sixth sectors are further divided into four existence regions. In detail, the end point of the sector on the axis line with the smaller deflection angle among the two phase axes dividing each sector is defined as the first end point, the end point of the sector on the axis line with the larger deflection angle is defined as the second end point, 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 with the first end point, the first intermediate point, and the intermediate end point as vertices. 4 shows the first to fourth regions R1 to R4 as the existence region, taking the first sector as an example. In the first sector, the first end point is "HLL", the second end point is "HHL", the first intermediate points are "MLL" and "HMM", the second intermediate points are "MML" and "HHM", and the intermediate end point is "HML".

[0029] The modulation unit 55 specifies the sector in which the command voltage vector Vαβ exists based on the electrical angle θe. For example, when 0°≦θe<60°, the modulation unit 55 specifies that the command voltage vector Vαβ exists in the first sector. The modulation unit 55 also specifies the existence region of the command voltage vector Vαβ based on the magnitude of the command voltage vector Vαβ and the angle in the sector. For example, the modulation unit 55 specifies in which of the first to fourth regions R1 to R4 in each sector the command voltage vector Vαβ exists, using information (specifically, map information or formula information) in which the magnitude of the command voltage vector Vαβ and the angle in the sector correspond to the first to fourth regions R1 to R4 as existence regions. The angle in the sector is calculated from the electrical angle θe and the sector number.

[0030] The modulation unit 55 determines the drive state of each of the switches SUH-SWL, QU-QW each time based on the sector and existence region of the identified command voltage vector Vαβ. The drive states of each of the switches SUH-SWL, QU-QW that can be realized by the inverter 30 are determined as shown in FIG.

[0031] The driving state of each switch SUH-SWL, QU-QW is represented by a set of phase voltages, and each phase voltage is represented by three levels H, M, and L. A phase voltage of level H is a voltage output in a target phase when the upper arm switches SUH, SVH, and SWH are turned on and the lower arm switches SUL, SVL, and SWL and the clamp switches QU, QV, and QW are turned off. A phase voltage of level M is a voltage output in a target phase when the clamp switches QU, QV, and QW are turned on and the upper arm switches SUH, SVH, and SWH and the lower arm switches SUL, SVL, and SWL are turned off. A phase voltage of level L is a voltage output in a target phase when the lower arm switches SUL, SVL, and SWL are turned on and the upper arm switches SUH, SVH, SWH and the clamp switches QU, QV, and QW are turned off.

[0032] For example, the drive state HML indicates that the U-phase voltage is at level H, the V-phase voltage is at level M, and the W-phase voltage is at level L. In the drive state HML, the U-phase upper arm switch SUH, the V-phase clamp switch QV, and the W-phase lower arm switch SWL are turned on, while the V- and W-phase upper arm switches SVH and SWH, the U- and W-phase clamp switches QU and QW, and the U- and V-phase lower arm switches SUL and SVL are turned off.

[0033] In addition, if the voltage of battery 20 is VH and the potential of neutral point O is the reference potential (0V), the phase voltage of level H is "VH / 2", the phase voltage of level M is "0", and the phase voltage of level L is "-VH / 2".

[0034] At the origin of the vector space, the switches SUH-SWL, QU-QW are in the drive states HHH, MMM, or LLL, regardless of the sector. In other words, at the origin, the switches SUH-SWL, QU-QW are in the drive states in which the windings 11U-11W of each phase are connected to the first end of the first capacitor 21, the neutral point O, or the second end of the second capacitor 22. In this embodiment, the drive states HHH, MMM, and LLL are referred to as zero-voltage drive states.

[0035] As shown in Fig. 3 and Fig. 4, the two different drive states MML, HHM of the switches SUH-SWL, QU-QW are located at the same position in the vector space. In these two drive states MML, HHM, the three line voltages (specifically, the UV phase voltage, the VW phase voltage, and the WU phase voltage) of the windings 11U-11W are equivalent. Note that the line voltages applied to the windings 11U-11W in the two drive states MML, HHM may vary as the voltages of the first and second capacitors 21, 22 vary, but when the voltages of the first and second capacitors 21, 22 are within a predetermined range, the line voltages applied in the two drive states MML, HHM are equivalent. The predetermined range of the voltages in the first and second capacitors 21, 22 is determined in consideration of, for example, the controllability of the rotating electric machine 10 and the reliability of the switches SUH-SWL, QU-QW, etc. Similarly, the two different drive states MLL, HMM of each of the switches SUH to SWL, QU to QW are at the same position in the vector space, and in these two drive states MLL, HMM, the line voltages are equivalent.

[0036] 5 and 6 show examples of current paths during periods when the two different drive states HMM and MLL are in effect. Here, the current paths are shown when the voltages of the first and second capacitors 21 and 22 are higher than the UV-phase voltage and the WU-phase voltage. In this case, in each drive state HMM and MLL, a U-phase current flows from the U-phase switches SUH, SUL, and QU side toward the U-phase winding 11U, and a V-phase current flows from the V-phase winding 11V and W-phase winding 11W toward the V-phase switches SVH, SVL, QV, SWH, SWL, and QW side. As shown in FIG. 5, during periods when the switches SUH to SWL, QU to QW are in the drive state HMM, a current flows into the neutral point O. As shown in FIG. 6, during periods when the switches SUH to SWL, QU to QW are in the drive state MLL, a current flows out of the neutral point O. That is, in each period when the switches SUH-SWL, QU-QW are in the driving states HMM, MLL, the direction of the current flowing through the neutral point O is opposite to each other. Similarly, in each period when the switches SUH-SWL, QU-QW are in the driving states MML, HHM, the direction of the current flowing through the neutral point O is opposite to each other.

[0037] That is, in the two different drive states MML, HHM and drive states MLL, HMM of the switches SUH to SWL and QU to QW, the line voltages are equivalent and the directions of the currents flowing to the neutral point O are opposite to each other. In this embodiment, the drive states MML, HHM and drive states MLL, HMM of the switches SUH to SWL and QU to QW are referred to as specific drive states. In addition, the drive states LML, MHM, drive states LMM, MHH, drive states LLM, MMH, and drive states MLM, HMH also fall under the category of specific drive states.

[0038] The modulation unit 55 decomposes the command voltage vector Vαβ into a plurality of voltage vectors. At this time, the command voltage vector Vαβ is decomposed into voltage vectors corresponding to the vertices of the existence region of the command voltage vector Vαβ. The modulation unit 55 calculates a period during which the switches SUH-SWL, QU-QW are in a drive state corresponding to the voltage vector in one switching period based on the magnitude of the decomposed voltage vector. Here, one switching period is a period during which the voltage vector output each time for a predetermined time width is averaged. The modulation unit 55 generates a drive command to turn on and off each of the switches SUH-SWL, QU-QW so that the drive state of each of the switches SUH-SWL, QU-QW is the calculated period in one switching period. Each of the switches SUH-SWL, QU-QW is driven based on the drive command, and an average voltage vector averaged over one switching period is output.

[0039] For example, as shown in FIG. 4, when the command voltage vector Vαβ is determined to exist in the first region R1 of the first sector, the command voltage vector Vαβ is decomposed into voltage vectors V1 and V2 corresponding to the driving states MLL, HMM and the driving states MML, HHM. V1 is a vector obtained by multiplying the voltage vector corresponding to the driving states MLL, HMM by ta (0 < ta < 1), and V2 is a vector obtained by multiplying the voltage vector corresponding to the driving states MML, HHM by tb (0 < tb < 1). In this case, if one switching period is TS, the period during which each switch SUH~SWL, QU~QW is in the driving state MLL or HMM is ta×TS, and the period during which each switch SUH~SWL, QU~QW is in the driving state MML, HHM is tb×TS. The period other than the periods ta×TS and tb×TS within one switching period is the period during which each switch SUH~SWL, QU~QW is in the driving state HHH, MMM or LLL.

[0040] Note that when the command voltage vector Vαβ is determined to exist in the second region R2 of the first sector, the command voltage vector Vαβ is decomposed into voltage vectors corresponding to the driving states MLL, HMM, the driving states MML, HHM and the driving state HML. When the command voltage vector Vαβ is determined to exist in the third region R3 of the first sector, the command voltage vector Vαβ is decomposed into voltage vectors corresponding to the driving states MML, HHM, the driving state HML and the driving state HHL. When the command voltage vector Vαβ is determined to exist in the fourth region R4 of the first sector, the command voltage vector Vαβ is decomposed into voltage vectors corresponding to the driving states MLL, HMM, the driving state HML and the driving state HLL. Then, based on the magnitudes of the voltage vectors into which the command voltage vector Vαβ is decomposed, the periods of the driving states corresponding to the respective voltage vectors are calculated.

[0041] When the command voltage vector Vαβ is determined to be present in the second to sixth sectors, the same process as that for the first sector is performed. For example, when the command voltage vector Vαβ is determined to be present in the first region R1 of the second sector, the command voltage vector Vαβ is decomposed into voltage vectors corresponding to the driving states HHH, MMM, LLL, MML, HHM, and LML, MHM. Based on the magnitude of the decomposed voltage vector, the periods during which the driving states HHH, MMM, LLL, MML, HHM, and LML, MHM are set to the driving states corresponding to the voltage vector are calculated.

[0042] In switching control, the modulation unit 55 controls the voltages of the first and second capacitors 21, 22 so that the voltages of the first and second capacitors 21, 22 are within a predetermined range. For example, the modulation unit 55 turns on and off the switches SUH to SWL, QU to QW so that the first and second capacitors 21, 22 are charged and discharged.

[0043] However, since the fluctuation period of the voltages of the first and second capacitors 21 and 22 is long, there is a concern that the controllability of the voltages of the first and second capacitors 21 and 22 may decrease.

[0044] For example, switching control may be performed such that the driving states of the switches SUH-SWL, QU-QW change in the order of HHH→HHM→HMM→MMM during the first half of two switching periods, and the driving states of the switches SUH-SWL, QU-QW change in the order of MMM→MML→MLL→LLL during the second half of two switching periods. Assuming that the voltage of each of the capacitors 21, 22 is higher than each interphase voltage, the direction of the current flowing through the neutral point O is reversed in each of the driving states HHM, MML and each of the driving states HMM, MLL, as in the case described above in FIG. 5 and FIG. 6. In the driving pattern of the switching control described above, the second capacitor 22 is charged in the first half of the switching period and discharged in the second half of the switching period. Also, the first capacitor 21 is discharged in the first half of the switching period and charged in the second half of the switching period. That is, each of the capacitors 21, 22 is charged and discharged only once during two switching periods. In this case, the number of times the voltage of each of the capacitors 21, 22 fluctuates per change in the driving state of each of the switches SUH to SWL, QU to QW decreases, and there is a concern that the controllability of the voltages of the first and second capacitors 21, 22 may decrease.

[0045] Therefore, the modulation unit 55 selects a drive pattern that is a combination of the drive states of the switches SUH-SWL, QU-QW in one switching period based on the command voltage vector Vαβ. At this time, the modulation unit 55 selects the drive pattern based on the command voltage vector Vαβ so that a period during which each of the switches SUH-SWL, QU-QW is in a specific drive state occurs within one switching period. The modulation unit 55 performs switching control of each of the switches SUH-SWL, QU-QW based on the selected drive pattern.

[0046] Fig. 7 shows an example of a drive pattern selected by the modulation unit 55 having the above-mentioned characteristics. Here, the first sector will be described as an example. As in the drive pattern shown in Fig. 7, the modulation unit 55 can select a drive pattern such that each specific drive state HMM, MLL or HHM, MML appears before the drive state of each switch SUH-SWL, QU-QW changes three times.

[0047] When the modulation unit 55 determines that the command voltage vector Vαβ is present in the first region R1 of the first sector, it turns on and off each of the switches SUH-SWL, QU-QW in one of modes A-D in the drive pattern shown in the column for the first region R1 in FIG. 7. In modes A and B in the first region R1, the drive states HMM, MMM, MML, and MLL are combined. In modes A and B in the first region R1, the transition order of the drive states of the switches SUH-SWL, QU-QW is different from each other, but at the beginning and end of the switching period, there are periods in which the switches SUH-SWL, QU-QW are in the specific drive states HMM, MLL. In modes C and D in the first region R1, the drive states HHM, HMM, MMM, and MML are combined. In modes C and D of the first region R1, although the transition orders of the drive states of the switches SUH to SWL and QU to QW are different, there are periods at the beginning and end of the switching period when the switches SUH to SWL and QU to QW are in the specific drive states HHM and MML.

[0048] When the command voltage vector Vαβ is in the first region R1 of each sector, each of the modes A to D of the drive pattern does not include the drive states HHH and LLL, but includes the drive state MMM. That is, the modulation unit 55 selects the drive pattern so as to include the drive state MMM in which each of the windings 11U to 11W is connected to the neutral point O among the zero voltage drive states.

[0049] When the modulation unit 55 determines that the command voltage vector Vαβ exists in the second region R2 of the first sector, it turns on and off each of the switches SUH-SWL, QU-QW in one of modes A-D in the drive pattern shown in the column for the second region R2 in FIG. 7. In modes A and B in the second region R2, HMM, HML, MML, and MLL are combined. In modes A and B in the second region R2, the transition order of the drive states of the switches SUH-SWL, QU-QW is different from each other, but at the beginning and end of the switching period, there are periods in which the switches SUH-SWL, QU-QW are in the specific drive states HMM, MLL. In modes C and D in the second region R2, HHM, HMM, HML, and MML are combined. In modes C and D of the second region R2, the transition order of the drive states of the switches SUH to SWL, QU to QW changes, but there are periods at the beginning and end of the switching period when the switches SUH to SWL, QU to QW are in the specific drive states HHM, MML.

[0050] When the modulation unit 55 determines that the command voltage vector Vαβ is present in the third region R3 of the first sector, it turns on and off each of the switches SUH-SWL, QU-QW in one of modes A-D in the drive pattern shown in the column for the third region R3 in FIG. 7. In modes A and B in the third region R3, the drive states HHM, HHL, HML, and MML are combined. In modes A and B in the third region R3, the transition order of the drive states of the switches SUH-SWL, QU-QW is different from each other, but at the beginning and end of the switching period, there are periods in which the switches SUH-SWL, QU-QW are in the specific drive states HHM and MML. In the third region R3, mode C has the same drive pattern as mode A, and mode D has the same drive pattern as mode B.

[0051] When the modulation unit 55 determines that the command voltage vector Vαβ is present in the fourth region R4 of the first sector, it turns on and off each of the switches SUH-SWL, QU-QW in one of modes A-D in the drive pattern shown in the column for the fourth region R4 in FIG. 7. In modes A and B in the fourth region R4, the drive states HMM, HML, HLL, and MLL are combined. In modes A and B in the fourth region R4, the transition order of the drive states of the switches SUH-SWL, QU-QW is different from each other, but at the beginning and end of the switching period, there are periods in which the switches SUH-SWL, QU-QW are in the specific drive states HMM and MLL. In the fourth region R4, mode C has the same drive pattern as mode A, and mode D has the same drive pattern as mode B.

[0052] When the sector and the existence region in which the command voltage vector Vαβ exists are the same as those in the previous switching cycle, the modulation unit 55 alternately selects the drive pattern modes A and B, or alternately selects the drive pattern modes C and D. In other words, the modulation unit 55 selects the drive pattern such that the first drive state and the last drive state in one switching cycle are each specific drive state, and the specific drive state that appears first in this switching cycle and the specific drive state that appears last in the previous switching cycle are the same drive state.

[0053] The above-mentioned drive pattern selection process can also be applied to the case where the command voltage vector Vαβ exists in the second to sixth sectors. For example, when the above-mentioned drive pattern selection process is applied to the second sector, the drive pattern selected by the modulation unit 55 is as follows. In mode A of the drive pattern in the first region R1 of the second sector, the drive states MML, MMM, MHM, and HHM appear in this order, in mode B, HHM, MHM, MMM, and MML appear in this order, in mode C, the drive states LML, MML, MMM, and MHM appear in this order, and in mode D, the drive states MHM, MMM, MML, and LML appear in this order. In mode A of the drive pattern in the second region R2 of the second sector, the drive states MML, MHL, MHM, and HHM appear in this order, in mode B the drive states HHM, MHM, MHL, and MML appear in this order, in mode C the drive states LML, MML, MHL, and MHM appear in this order, and in mode D the drive states MHM, MHL, MML, and LML appear in this order.

[0054] In mode A of the drive pattern in the third region R3 of the second sector, the drive states LML, LHL, MHL, and MHM appear in this order, and in mode B, the drive states MHM, MHL, LHL, and LML appear in this order, mode C is the same as mode A, and mode D is the same as mode B. In mode A of the drive pattern in the fourth region R4 of the second sector, the drive states MML, MHL, HHL, and HHM appear in this order, and in mode B, the drive states HHM, HHL, MHL, and MML appear in this order, mode C is the same as mode A, and mode D is the same as mode B.

[0055] Based on the command voltage vector Vαβ and the current flowing through each of the windings 11U-11W, the modulation unit 55 selects, from among the modes included in the selected drive pattern, a mode in which the amount of change in the accumulated charge of the first capacitor 21 and the amount of change in the accumulated charge of the second capacitor 22 due to a specific phase current, which is a current flowing through a specific phase, is larger. Here, the specific phase is a phase in which the level of the phase voltage in each specific drive state is different from the other phases. The specific phase current is a current flowing through a specific phase during a period in which each of the switches SUH-SWL, QU-QW is in each specific drive state. The modulation unit 55 can use a detection value of the phase current sensor 43 as the current flowing through each of the windings 11U-11W.

[0056] In detail, a case where the command voltage vector Vαβ is determined to be present in the first region R1 of the first sector will be described as an example. The specific phase during the period when each specific drive state HMM, MLL is the U phase, and the specific phase current is the U phase current flowing during the period when each specific drive state HMM, MLL is. Also, the specific phase during the period when each specific drive state HHM, MML is the W phase, and the specific phase current is the W phase current flowing during the period when each specific drive state HHM, MML is. Each specific drive state HMM, MLL is a drive state used in modes A, B, and each specific drive state HHM, MML is a drive state used in modes C, D. That is, the drive pattern in the first region R1 of the first sector includes two modes (e.g., modes A, C and modes B, D) that can be selected for the same command voltage vector Vαβ, and each mode has a different specific phase during the period when each specific drive state is set. In this case, the modulation unit 55 compares the amount of change in the stored charge of each capacitor 21, 22 caused by the flow of a U-phase current during the period in which each specific driving state is set to HMM, MLL with the amount of change in the stored charge of each capacitor 21, 22 caused by the flow of a W-phase current during the period in which each specific driving state is set to HHM, MML.

[0057] The amount of change in the accumulated charge of each capacitor 21, 22 caused by the flow of the U-phase current during the period when each specific drive state HMM, MLL is, for example, |IU|×ta×TS. The amount of change in the accumulated charge of each capacitor 21, 22 caused by the flow of the W-phase current during the period when each specific drive state HHM, MML is, for example, |IW|×tb×TS. Here, |IU|, |IW| indicate the magnitude of the U-phase current, W-phase current, and TS indicates the length of one switching period. As described above in FIG. 4, the coefficients ta, tb multiply the voltage vectors V1, V2 by a constant. In this case, ta×TS corresponds to the total period when each switch SUH-SWL, QU-QW is in the specific drive state MLL, HMM, and tb×TS corresponds to the total period when each switch SUH-SWL, QU-QW is in the specific drive state MML, HHM.

[0058] When the modulation unit 55 determines that |IU|×ta×TS>|IW|×tb×TS, it selects one of the drive pattern modes A and B. On the other hand, when the modulation unit 55 determines that |IU|×ta×TS≦|IW|×tb×TS, it selects one of the drive pattern modes C and D.

[0059] Note that even when the modulation unit 55 determines that the command voltage vector Vαβ is in the second region R2 of the first sector, it can select the drive pattern modes A and B or the drive pattern modes C and D in accordance with a comparison of the amount of change in the accumulated charge of each capacitor 21, 22 due to the specific phase current. When the modulation unit 55 determines that the command voltage vector Vαβ is in the third and fourth regions R3 and R4 of the first sector, the drive pattern modes A and C and modes B and D are the same, so it is not necessary to perform the above-mentioned processing.

[0060] The above-mentioned mode selection process for the drive patterns of the switches SUH to SWL and QU to QW is also applicable to the case where the command voltage vector Vαβ exists in the second to sixth sectors.

[0061] Specifically, when the command voltage vector Vαβ is in the fourth sector, the mode of the drive pattern is selected as follows. The specific phase during the period of each specific drive state LMM, MHH is the U phase, and the specific phase current is the U phase current flowing during the period of each specific drive state LMM, MHH. The specific phase during the period of each specific drive state LLM, MMH is the W phase, and the specific phase current is the W phase current flowing during the period of each specific drive state LLM, MMH. In this case, the modulation unit 55 compares the amount of change in the accumulated charge of each capacitor 21, 22 caused by the U phase current flowing during the period of each specific drive state LMM, MHH with the amount of change in the accumulated charge of each capacitor 21, 22 caused by the W phase current flowing during the period of each specific drive state LLM, MMH. The modulation unit 55 selects the mode of the drive pattern according to the comparison result. Specifically, the modulation unit 55 selects whether the specific drive states LMM, MHH on the U-phase side or the specific drive states LLM, MMH on the W-phase side are to appear within one switching period.

[0062] When the command voltage vector Vαβ is in the second or fifth sector, the mode of the drive pattern is selected as follows. The specific phase during the period of each specific drive state LML, MHM or MLM, HMH is the V phase, and the specific phase current is the V phase current flowing during the period of each specific drive state LML, MHM or MLM, HMH. In this case, the modulation unit 55 compares the amount of change in the accumulated charge of each capacitor 21, 22 caused by the flow of the V phase current during the period of each specific drive state LML, MHM or MLM, HMH with the amount of change in the accumulated charge of each capacitor 21, 22 caused by the flow of the W phase current during the period of each specific drive state MML, HHM or LLM, MMH. The modulation unit 55 selects the mode of the drive pattern according to the comparison result. Specifically, the modulation unit 55 selects whether the specific drive states LML, MHM or MLM, HMH on the V-phase side or the specific drive states MML, HHM or LLM, MMH on the W-phase side are to appear within one switching period.

[0063] When the command voltage vector Vαβ is in the third or sixth sector, the mode of the drive pattern is selected as follows. The modulation unit 55 compares the amount of change in the accumulated charge of each of the capacitors 21 and 22 caused by the U-phase current flowing during the period of each specific drive state LMM, MHH, or MLL, HMM with the amount of change in the accumulated charge of each of the capacitors 21 and 22 caused by the V-phase current flowing during the period of each specific drive state LML, MHM, or MLM, HMH. The modulation unit 55 selects the mode of the drive pattern according to the comparison result. Specifically, the modulation unit 55 selects which of the specific drive states LMM, MHH, MLL, HMM on the U-phase side and the specific drive states LML, MHM, MLM, HMH on the V-phase side is to appear within one switching period.

[0064] The modulation unit 55 adjusts the ratio of the appearance period of each specific drive state to the total appearance period of two different specific drive states included in the drive pattern in one switching cycle based on the adjustment coefficient k. Here, the modulation unit 55 adjusts the value of the adjustment coefficient k based on the command voltage vector Vαβ and the voltages of the capacitors 21, 22. The modulation unit 55 can use the detection value of the first voltage sensor 41 as the voltage of the first capacitor 21, and can use the detection value of the second voltage sensor 42 as the voltage of the second capacitor 22.

[0065] Specifically, a case will be described as an example in which the command voltage vector Vαβ is specified to be in the first region R1 of the first sector, and each switch SUH-SWL, QU-QW is driven in mode A of the drive pattern. In this case, the modulation unit 55 sets the period during which each switch SUH-SWL, QU-QW is in the specific drive state HMM to (1-k)×ta×TS, sets the period during which each switch is in the specific drive state MLL to k×ta×TS, and adjusts the value of the adjustment coefficient k (0≦k≦1). Note that ta×TS is the total period during which each switch SUH-SWL, QU-QW is in the specific drive state MLL, HMM.

[0066] In this embodiment, the value of the adjustment coefficient k is adjusted so as to reduce the voltage fluctuation amplitude ΔV of each of the capacitors 21, 22 in one switching period. For example, the voltage fluctuation amplitude ΔV of each of the capacitors 21, 22 in one switching period is expressed by the following formula (e1).

[0067]

number

[0068] For example, the modulation unit 55 adjusts the adjustment coefficient k so that the voltage fluctuation amplitude ΔV of each of the capacitors 21, 22 in one switching period becomes 0. If ΔV=0 in the above equation (e1), the adjustment coefficient k is expressed by the following equation (e2).

[0069]

number

[0070] The above-mentioned adjustment process using the adjustment coefficient k is applicable not only to the case where the command voltage vector Vαβ is in the first region R1 of the first sector, but also to the case where the command voltage vector Vαβ is in the first region R1 of the second to sixth sectors. The adjustment process using the adjustment coefficient k is also applicable to the case where the command voltage vector Vαβ is in the second to fourth regions R2 to R4 of the first to sixth sectors. In this case, the appearance periods of two different specific driving states that appear within one switching period can be adjusted by considering the voltage fluctuation amplitude ΔV according to the sector and the existence region in which the command voltage vector Vαβ exists.

[0071] 8 shows a procedure for the control process executed by the control device 40. This control process is repeatedly executed at a predetermined cycle.

[0072] In step S10, the command torque Trq* input from a higher-level 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 of the rotating electric machine 10 are acquired. In this embodiment, the detection value of the phase current sensor 43 is acquired as the phase current, the detection value of the first voltage sensor 41 is acquired as the voltage of the first capacitor 21, the detection value of the second voltage sensor 42 is acquired as the voltage of the second capacitor 22, and the detection value of the rotation angle sensor 44 is acquired as the electrical angle of the rotating electric machine 10.

[0073] Here, the conduction loss caused by the current flowing through each switch SUH-SWL, QU-QW may be larger in the drive state MMM than in the drive states HHH and LLL. In this embodiment, in the drive state MMM where each clamp switch QU-QW is on, a current flows through six IGBTs, and in the drive states HHH and LLL where each upper arm switch SUH-SWH or each lower arm switch SUL-SWL is on, a current flows through three IGBTs. In this case, when each switch SUH-SWL, QU-QW is set to the drive state MMM among the zero voltage drive states, there is a concern that the conduction loss in switching control will be large due to the large number of switches through which a current flows.

[0074] Therefore, in this embodiment, the switching control method is switched depending on the operating point of the rotating electrical machine 10.

[0075] In step S11, it is determined whether or not the operating point of the rotating electric machine 10 is within the voltage control range E2. The voltage control range E2 is a range that is set outside the specific range E1 in which the conduction loss caused by the conduction current of each of the switches SUH-SWL, QU-QW is equal to or greater than a predetermined allowable value, and is a range in which the voltage fluctuation amplitude of each of the capacitors 21, 22 is relatively large. If the determination in step S11 is negative, the process proceeds to step S17. On the other hand, if the determination in step S11 is positive, the process proceeds to step S12.

[0076] Specifically, as shown in FIG. 9, the operating point of the rotating electric machine 10 is determined by the torque and rotation speed of the rotating electric machine 10. The specific range E1 and the voltage control range E2 are ranges of the operating point of the rotating electric machine 10. The specific range E1 is a range in which the torque of the rotating electric machine 10 is a value ranging from a first torque value Tq1 to a maximum torque value Tqc that the rotating electric machine 10 can output, and the rotation speed of the rotating electric machine 10 is a value ranging from a lower limit value N0 set on the low rotation speed side to a first rotation speed value N1 higher than the lower limit value N0. The lower limit value N0 is, for example, 0. That is, the specific range E1 is set on the side where the modulation factor of the switching control is a low modulation factor. In the specific range E1, the conduction loss in the switching control may be large, and it is desirable to shorten the appearance period of the drive state MMM of each switch SUH to SWL, QU to QW.

[0077] The voltage control range E2 is a range in which the torque of the rotating electric machine 10 is a value between a second torque value Tq2 lower than the first torque value Tq1 and a maximum torque value Tqc, and the rotation speed of the rotating electric machine 10 is a value between a first rotation speed value N1 and a second rotation speed value N2. The second rotation speed value N2 is a value higher than the first rotation speed value N1 and lower than a predetermined rotation speed value Nc. The predetermined rotation speed value Nc is a value set on the low rotation speed side of a region in which the torque that the rotating electric machine 10 can output decreases as the rotation speed of the rotating electric machine 10 increases. In the voltage control range E2, the voltage fluctuation amplitude of each of the capacitors 21, 22 becomes relatively large, so it is desirable to improve the controllability of the voltage of each of the capacitors 21, 22.

[0078] Therefore, in this embodiment, if it is determined in step S11 that the operating point of the rotating electric machine 10 is within the voltage control range E2, the following processing of steps S12 to S16 is performed. Note that a command torque can be used as the torque for determining the operating point of the rotating electric machine 10, and a rotation speed calculated based on a detection value of the rotation angle sensor 44 can be used as the rotation speed. The processing of step S11 corresponds to a "determination unit."

[0079] In step S12, the command voltage vector Vαβ is calculated. In step S13, the sector in which the command voltage vector Vαβ exists and the area in the sector are identified. In steps S12 and S13, the control device 40 functions as the command current setting unit 50, the two-phase conversion unit 51, the d, q-axis deviation calculation units 52a, 52b, the d, q-axis command voltage calculation units 53a, 53b, the fixed coordinate conversion unit 54, and the modulation unit 55 described in FIG. 2 above.

[0080] In step S14, a drive pattern is selected based on the command voltage vector Vαβ and the phase current. Based on the command voltage vector Vαβ, a drive pattern is selected so that a period in which two different specific drive states are set occurs within one switching period. Furthermore, in this embodiment, a drive pattern is selected so that the first drive state and the last drive state in one switching period are each specific drive state, and the specific drive state that appears first in this switching period and the specific drive state that appears last in the previous switching period are the same drive state. Also, a drive state MMM is selected in a period in which the drive states of the switches SUH to SWL, QU to QW are zero voltage drive states. Based on the command voltage vector Vαβ and the phase current, a mode in which the amount of change in the accumulated charge of the first and second capacitors 21 and 22 due to the specific phase current is larger is selected from the two modes included in the selected drive pattern. The process of step S14 corresponds to a "selection unit."

[0081] In step S15, an adjustment coefficient k is calculated. In this embodiment, the adjustment coefficient k is adjusted so that the voltage fluctuation amplitude ΔV of each of the capacitors 21 and 22 in one switching period becomes 0 or a minimum. The process of step S15 corresponds to an "adjustment unit."

[0082] In step S16, switching control is performed based on the drive patterns and modes of the switches SUH to SWL and QU to QW determined by the processes in steps S12 to S15.

[0083] In step S17, normal control is performed. In normal control, unlike the selection process of the drive pattern in step S14, it is not necessary to select a drive pattern so that a period in which two different specific drive states occur within one switching cycle. In addition, in normal control, when it is determined that the command voltage vector Vαβ exists in the first region R1 of each sector, it is not necessary to select a drive pattern so that the drive state of each switch SUH to SWL, QU to QW is limited to the drive state MMM among the zero voltage drive states. In this case, in normal control, switching control is performed so that the period in which each switch SUH to SWL, QU to QW is in the zero voltage drive state is shortened compared to the case where a positive determination is made in step S11. For example, in normal control, the drive state of each switch SUH to SWL, QU to QW changes in the order of HHH → HHM → HMM → MMM or MMM → MML → MLL → LLL during one switching cycle. Note that the processes in steps S16 and S17 correspond to a "switch control unit".

[0084] Fig. 10 shows an example comparing the switching control according to this embodiment with the switching control of the comparative example. In Fig. 10, (a) shows the transition of the phase current, and (b) shows the transition of the voltage of each of the capacitors 21 and 22. In Fig. 10(b), the solid line shows the transition of the voltage of the first capacitor 21, and the dashed line shows the transition of the voltage of the second capacitor 22. Here, normal control is performed as the comparative example. Note that in Figs. 10(a) and (b), the scales of the vertical and horizontal axes in each graph of this embodiment and the comparative example are the same.

[0085] In this embodiment, the processing of steps S12 to S16 is performed, thereby shortening the charge / discharge cycle (i.e., fluctuation cycle) of each of the capacitors 21, 22 compared to the comparative example. As a result, in this embodiment, the fluctuation amplitude V0-p of the voltage of each of the capacitors 21, 22 is reduced compared to the comparative example. SC1 shown in FIG. 10(b) indicates the charge / discharge cycle of each of the capacitors 21, 22 in the comparative example, and SC2 indicates the charge / discharge cycle of each of the capacitors 21, 22 in this embodiment. In the example shown in FIG. 10, by performing the switching control according to this embodiment, the charge / discharge cycle of each of the capacitors 21, 22 can be shortened to half that of the comparative example, and the fluctuation amplitude V0-p of the voltage of each of the capacitors 21, 22 can be reduced to 40% of that of the comparative example.

[0086] According to the present embodiment described above in detail, the following effects can be obtained.

[0087] Based on the command voltage vector Vαβ, a drive pattern is selected which is a combination of the drive states of the switches SUH to SWL, QU to QW. Here, based on the command voltage vector Vαβ, a drive pattern is selected so that a period in which the switches are in two different specific drive states occurs within one switching period. Then, based on the selected drive pattern, switching control of the switches SUH to SWL, QU to QW is performed. In this case, the voltages of the capacitors 21, 22 change in the opposite directions to each other during a period in one switching period in which the switches SUH to SWL, QU to QW are in one of the specific drive states and during a period in one switching period in which the switches are in the other drive state. Therefore, compared to a case in which only a period in which the switches are in one of the two different specific drive states occurs within one switching period, the voltages of the capacitors 21, 22 can be varied at short intervals, and the variation period of the voltages of the capacitors 21, 22 can be shortened. As a result, the controllability of the voltages of the capacitors 21, 22 can be improved.

[0088] Based on the adjustment coefficient k, the ratio of the appearance period of each specific drive state to the total appearance period of each specific drive state included in the drive pattern in one switching cycle is adjusted. This makes it possible to adjust the amount of change when the voltages of the capacitors 21 and 22 change in the opposite directions. Therefore, the voltages of the capacitors 21 and 22 can be accurately controlled. As a result, the controllability of the voltages of the capacitors 21 and 22 can be accurately improved.

[0089] Based on the command voltage vector Vαβ and the phase current, a mode in which the amount of change in the accumulated charge of the first and second capacitors 21, 22 due to the specific phase current is larger is selected from among the modes included in the selected drive pattern. Then, switching control is performed based on the selected drive pattern and mode. In this case, the amount of change in the voltage of each capacitor 21, 22 within a switching period can be reduced compared to when a mode in which the amount of change in the accumulated charge of the first and second capacitors 21, 22 due to the specific phase current is smaller is selected from among the modes included in the selected drive pattern.

[0090] A drive pattern is selected so that two different specific drive states appear within one switching period before the drive states of the switches SUH-SWL, QU-QW change three times. In this case, the number of times the voltage of each of the capacitors 21, 22 changes per number of changes in the drive state of each of the switches SUH-SWL, QU-QW can be increased compared to a case in which the drive states of the switches SUH-SWL, QU-QW change four or more times before two different specific drive states appear. This makes it possible to appropriately shorten the period in which the voltage of each of the capacitors 21, 22 changes.

[0091] The drive pattern is selected so that the first and last drive states in one switching cycle are two different specific drive states, and the specific drive state of each switch SUH-SWL, QU-QW that appears first in the current switching cycle is the same as the specific drive state of each switch SUH-SWL, QU-QW that appears last in the previous switching cycle. This makes it possible to prevent unnecessary switching from being performed in successive switching cycles. As a result, it is possible to realize switching control that is suitable for reducing switching loss.

[0092] In the first region R1 of the first to sixth sectors, the drive state of each of the switches SUH to SWL, QU to QW may be set to a zero voltage drive state. In this case, during the transition from the first specific drive state to the last specific drive state in one switching period, each of the switches SUH to SWL, QU to QW is set to the zero voltage drive state. At this time, it is desirable to suppress unnecessary switching.

[0093] In this regard, the drive patterns in the first region R1 of the first to sixth sectors are determined to include the drive state MMM of the zero voltage drive state. In this case, it is possible to suppress unnecessary switching within one switching period compared to when the drive states of the switches SUH to SWL, QU to QW are set to the drive states HHH, LLL of the zero voltage drive state. As a result, it is possible to realize switching control suitable for reducing switching loss.

[0094] It is determined whether the operating point of the rotating electric machine 10 is within the voltage control range E2. If it is determined that the operating point of the rotating electric machine 10 is within the voltage control range E2, switching control is performed to improve the controllability of the voltage in each of the capacitors 21, 22, and the driving states of the switches SUH-SWL, QU-QW are set to the driving state MMM among the zero voltage driving states. On the other hand, if it is determined that the operating point of the rotating electric machine 10 is outside the voltage control range E2, normal control is performed.

[0095] In normal control, the zero voltage drive state is not limited to the drive state MMM, and each of the switches SUH-SWL, QU-QW may be in the drive state HHH, LLL. In this case, the period during which each of the switches SUH-SWL, QU-QW is in the drive state MMM can be shortened compared to when the operating point of the rotating electric machine 10 is within the voltage control range E2. As a result, in a situation in which the conduction loss in the switching control may be large, the conduction loss is reduced during the period during which each of the switches SUH-SWL, QU-QW is in the zero voltage drive state. Therefore, it is possible to improve the controllability of the voltage of each of the capacitors 21, 22 while suppressing the conduction loss in the switching control from increasing.

[0096] <Second embodiment> Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the configuration of the inverter is changed.

[0097] As shown in FIG. 11, the inverter 30 is a three-level inverter of a neutral point clamp type. The inverter 30 includes U-phase first to fourth switches Su1 to Su4, V-phase first to fourth switches Sv1 to Sv4, W-phase first to fourth switches Sw1 to Sw4, and first to sixth clamp diodes Dc1 to Dc6. In this embodiment, a voltage-controlled semiconductor switching element is used as each of the switches Su1 to Su4, Sv1 to Sv4, and Sw1 to Sw4, and more specifically, an IGBT is used. In this case, the high potential side terminals of the switches Su1 to Su4, Sv1 to Sv4, and Sw1 to Sw4 are collectors, and the low potential side terminals are emitters. In FIG. 11, the same components as those shown in FIG. 1 are denoted by the same reference numerals for convenience.

[0098] The U-phase first to fourth switches Su1 to Su4 are connected in series with their emitters and collectors connected. The collector of the U-phase first switch Su1 is connected to the positive terminal of the battery 20 via a positive bus 31, and the emitter of the U-phase fourth switch Su4 is connected to the negative terminal of the battery 20 via a negative bus 32. The U-phase input terminal of the rotating electric machine 10 is connected to the connection point between the U-phase second switch Su2 and the U-phase third switch Su3. The cathode of the first clamp diode Dc1 is connected to the connection point between the U-phase first switch Su1 and the U-phase second switch Su2, and the cathode of the second clamp diode Dc2 is connected to the anode of the first clamp diode Dc1. The anode of the second clamp diode Dc2 is connected to the connection point between the U-phase third switch Su3 and the U-phase fourth switch Su4. Freewheel diodes Du1, Du2, Du3, and Du4 are connected in inverse parallel to the U-phase switches Su1, Su2, Su3, and Su4, respectively.

[0099] The V-phase first to fourth switches Sv1 to Sv4 are connected in series with their emitters and collectors connected. The collector of the V-phase first switch Sv1 is connected to the positive terminal of the battery 20 via the positive bus 31, and the emitter of the V-phase fourth switch Sv4 is connected to the negative terminal of the battery 20 via the negative bus 32. The V-phase input terminal of the rotating electric machine 10 is connected to the connection point between the V-phase second switch Sv2 and the V-phase third switch Sv3. The cathode of the third clamp diode Dc3 is connected to the connection point between the V-phase first switch Sv1 and the V-phase second switch Sv2, and the cathode of the fourth clamp diode Dc4 is connected to the anode of the third clamp diode Dc3. The anode of the fourth clamp diode Dc4 is connected to the connection point between the V-phase third switch Sv3 and the V-phase fourth switch Sv4. Freewheel diodes Dv1, Dv2, Dv3, and Dv4 are connected in inverse parallel to the V-phase switches Sv1, Sv2, Sv3, and Sv4, respectively.

[0100] The W-phase first to fourth switches Sw1 to Sw4 are connected in series with their emitters and collectors connected. The collector of the W-phase first switch Sw1 is connected to the positive terminal of the battery 20 via the positive bus 31, and the emitter of the W-phase fourth switch Sw4 is connected to the negative terminal of the battery 20 via the negative bus 32. The W-phase input terminal of the rotating electric machine 10 is connected to the connection point between the W-phase second switch Sw2 and the W-phase third switch Sw3. The cathode of the fifth clamp diode Dc5 is connected to the connection point between the W-phase first switch Sw1 and the W-phase second switch Sw2, and the cathode of the sixth clamp diode Dc6 is connected to the anode of the fifth clamp diode Dc5. The connection point between the W-phase third switch Sw3 and the W-phase fourth switch Sw4 is connected to the anode of the sixth clamp diode Dc6. Freewheel diodes Dw1, Dw2, Dw3, and Dw4 are connected in inverse parallel to the W-phase switches Sw1, Sw2, Sw3, and Sw4, respectively.

[0101] A neutral point O is connected to the connection point of the first clamp diode Dc1 and the second clamp diode Dc2, the connection point of the third clamp diode Dc3 and the fourth clamp diode Dc4, and the connection point of the fifth clamp diode Dc5 and the sixth clamp diode Dc6.

[0102] In the neutral point clamp inverter 30, the drive states of the switches Su1 to Sw4 are determined as follows: A phase voltage of level H is output in a target phase by turning on the first and second switches Su1, Su2, Sv1, Sv2, Sw1, and Sw2 and turning off the third and fourth switches Su3, Su4, Sv3, Sv4, Sw3, and Sw4. A phase voltage of level M is output in a target phase by turning on the second and third switches Su2, Su3, Sv2, Sv3, Sw2, and Sw3 and turning off the first and fourth switches Su1, Su4, Sv1, Sv4, Sw1, and Sw4. A level L phase voltage is output in the target phase by turning on the third and fourth switches Su3, Su4, Sv3, Sv4, Sw3, and Sw4 and turning off the first and second switches Su1, Su2, Sv1, Sv2, Sw1, and Sw2.

[0103] For example, during the period in which each switch Su1 to Sw4 is in the driving state HML, the U-phase first and second switches Su1, Su2, the V-phase second and third switches Sv2, Sv3, and the W-phase third and fourth switches Sw3, Sw4 are turned on, while the U-phase third and fourth switches Su3, Su4, the V-phase first and fourth switches Sv1, Sv4, and the W-phase first and second switches Sw1, Sw2 are turned off.

[0104] Even in the case of the neutral point clamped inverter 30 described above, the processes of steps S10 to S17 shown in FIG.

[0105] In the neutral point clamped inverter 30, when the switches Su1 to Sw4 are in the drive state MMM, the six IGBTs are turned on and the six clamp diodes are turned on. When the switches Su1 to Sw4 are in the drive states HHH and LLL, the six IGBTs are turned on. In this case, depending on the conduction loss of the clamp diodes, even in this embodiment, the conduction loss in the switching control may increase due to the switches Su1 to Sw4 being in the drive state MMM during the period when the zero voltage drive state is set. Therefore, in step S11 of FIG. 8, the switching control method is switched based on the drive state of the rotating electric machine 10, thereby suppressing the conduction loss in the switching control from increasing and improving the controllability of the voltage of each of the capacitors 21 and 22.

[0106] <Other embodiments> The above embodiment may be modified as follows.

[0107] The modulation unit 55 may adjust the ratio of the appearance period of each specific drive state to the total appearance period of each specific drive state included in the drive pattern based on at least one of the voltage of the first capacitor 21 and the voltage of the second capacitor 22 instead of the adjustment coefficient k. For example, when the command voltage vector Vαβ is specified to be present in the first region R1 of the first sector and the switches SUH-SWL, QU-QW are driven in mode A of the drive pattern, the modulation unit 55 may lengthen the period during which the switches SUH-SWL, QU-QW are in the drive state HMM and shorten the period during which the switches are in the drive state MLL as the detected voltage of the first capacitor 21 is higher. Also, for example, the modulation unit 55 may lengthen the period during which the switches SUH-SWL, QU-QW are in the drive state MLL and shorten the period during which the switches are in the drive state HMM as the detected voltage of the second capacitor 22 is higher.

[0108] In this embodiment as well, the ratio of the period during which each of the switches SUH to SWL, QU to QW is driven in two different specific drive states can be adjusted, and the voltage of each of the capacitors 21, 22 can be accurately controlled.

[0109] 8, the drive pattern described in step S14 may be selected instead of the drive pattern of normal control. However, in step S17 of this embodiment, a drive pattern is selected so that the drive states of the switches SUH to SWL, QU to QW are in the drive state HHH or LLL during the period in which they are in the zero voltage drive state. This makes it possible to shorten the period in which the switches SUH to SWL, QU to QW are in the drive state MMM, compared to when the drive pattern described in step S14 is used.

[0110] 8, instead of determining whether the operating point of the rotating electric machine 10 is within the voltage control range E2, it may be determined whether it is within the specific range E1. In this case, if the determination in step S11 is negative, the process proceeds to step S12. On the other hand, if the determination in step S11 is positive, the process proceeds to step S17.

[0111] 8 may not be performed. That is, the processes of steps S12 to S16 may be performed without switching the switching control method according to the operating point of the rotating electric machine 10.

[0112] 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.

[0113] The power storage unit connected to the inverter is not limited to a capacitor, and may be a rechargeable battery.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] Characteristic configurations extracted from the above-described embodiments will be described below. [Configuration 1] a first power storage unit (21) and a second power storage unit (22) connected in series; A rotating electric machine (10) having three phase windings (11U to 11W); a three-level inverter (30) having three-phase switches (SUH to SWL, QU to QW, Su1 to Sw4) connecting the windings of each phase in the rotating electric machine 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, a selection unit that selects a drive pattern, which is a combination of drive states of the switches of each phase in one switching period, based on a command voltage for controlling a control amount of the rotating electric machine to a command value; A switch control unit that performs switching control of the switch based on the selected drive pattern, Two different driving states in which the three line voltages of the winding are equal and the directions of the currents flowing through the neutral point are opposite to each other are defined as specific driving states; The control device for a three-level inverter, wherein the selection unit selects the drive pattern based on the command voltage so that a period during which each of the specific drive states occurs within one switching period. [Configuration 2] The control device for a three-level inverter according to configuration 1, further comprising an adjustment unit that adjusts a ratio of an appearance period of each of the specific drive states included in the drive pattern in one switching period to a total appearance period of each of the specific drive states included in the drive pattern in one switching period, based on at least one of a voltage of the first storage unit and a voltage of the second storage unit. [Configuration 3] a phase having a connection point between the winding and any one of the positive electrode side of the first power storage unit, the neutral point, and the negative electrode side of the second power storage unit in each of the specific driving states that is different from other phases is defined as a specific phase; the drive pattern includes two modes selectable for the same command voltage, the specific phases during which the specific drive states are respectively different from each other; a current flowing through the specific phase during a period in which each of the specific drive states is set is defined as a specific phase current; The control device for a three-level inverter according to configuration 1 or 2, wherein the selection unit selects, from among the modes included in the selected drive pattern, a mode in which an amount of change in the stored charge of the first storage unit and an amount of change in the stored charge of the second storage unit due to the specific phase current are larger, based on the command voltage and the current flowing through the winding of each phase. [Configuration 4] 4. The three-level inverter control device according to any one of configurations 1 to 3, wherein the selection unit selects the drive pattern such that each of the specific drive states appears within three changes of the drive state. [Configuration 5] The control device for a three-level inverter according to any one of configurations 1 to 4, wherein the selection unit selects the drive pattern such that the first drive state and the last drive state in the one switching period are the specific drive states, and the specific drive state that appears first in the current one switching period and the specific drive state that appears last in the previous one switching period are the same drive state. [Configuration 6] the driving state in which the winding of each phase is 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 is defined as a zero voltage driving state; The control device for a three-level inverter according to configuration 5, wherein the selection unit selects the drive pattern so as to include, among the zero voltage drive states, a drive state in which the winding of each phase and the neutral point are connected. [Configuration 7] in the three-level inverter, a conduction loss caused by a current flowing through each switch is larger when the winding of each phase is connected to the neutral point by the switch than when the positive electrode side of the first power storage unit or the negative electrode side of the second power storage unit is connected to the winding of each phase by the switch, a determination unit that determines whether or not an operating point of the rotating electric machine is within a specific range in which a conduction loss caused by a current flowing through the switch is equal to or greater than a tolerable value; The control device for a three-level inverter according to configuration 6, wherein the switch control unit performs the switching control such that, when it is determined that the voltage is within the specific range, a period during which the winding of each phase and the neutral point are connected is shortened during a period during which the switch is in the zero voltage drive state, compared to a case where it is determined that the voltage is outside the specific range. [Explanation of symbols]

[0118] 10... rotating electric machine, 11U, 11V, 11W... U-, V-, and W-phase windings, 21, 22... first and second capacitors, 30... inverter, 40... 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 windings (11U to 11W); a three-level inverter (30) having three-phase switches (SUH to SWL, QU to QW, Su1 to Sw4) connecting the windings of each phase in the rotating electric machine 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, a selection unit that selects a drive pattern that is a combination of drive states of the switches of each phase in one switching period based on a command voltage vector for controlling a control amount of the rotary electric machine to a command value; A switch control unit that performs switching control of the switch based on the selected drive pattern, A vector space in which the command voltage vector exists is divided into six sectors with respect to the deflection angle of the command voltage vector, each of the sectors includes a first region and a second region; In each of the sectors, when an end point of the sector on one of the two-phase axes dividing the sector with the smaller deflection angle is defined as a first end point, an end point of the sector on one of the two-phase axes dividing the sector with the larger deflection angle is defined as a second end point, a midpoint between the origin of the vector space and the first end point is defined as a first intermediate point, a midpoint between the origin and the second end point is defined as a second intermediate point, and a midpoint between the first end point and the second end point is defined as an intermediate end point, the first region is defined as a region surrounded by a triangle with vertices at the origin, the first intermediate point, and the second region is defined as a region surrounded by a triangle with vertices at the first intermediate point, the second intermediate point, and the intermediate end point, two different driving states for outputting each phase voltage at the first intermediate point or the second intermediate point, in which three line voltages of the winding are equal and the directions of currents flowing through the neutral point are opposite to each other, are defined as specific driving states; The selection unit is the drive pattern being a combination of the drive states for outputting each phase voltage at the origin, the first intermediate point, and the second intermediate point when the command voltage vector is in the first region of any of the sectors, the drive pattern being selected such that a period during which each of the specific drive states occurs within one switching period; A control device for a three-level inverter, wherein the drive pattern is a combination of the drive states that output each phase voltage at the first intermediate point, the second intermediate point, and the intermediate end point when the command voltage vector is in the second region of any of the sectors, and the drive pattern is selected so that a period in which each of the specific drive states occurs within one switching period.

2. A first storage unit (21) and a second storage unit (22) connected in series; A rotating electric machine (10) having three phase windings (11U to 11W); a three-level inverter (30) having three-phase switches (SUH to SWL, QU to QW, Su1 to Sw4) connecting the windings of each phase in the rotating electric machine 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, a selection unit that selects a drive pattern that is a combination of drive states of the switches of each phase in one switching period based on a command voltage for controlling a control amount of the rotary electric machine to a command value; A switch control unit that performs switching control of the switch based on the selected drive pattern, Two different driving states in which three line voltages of the winding are equal and the directions of currents flowing through the neutral point are opposite to each other are defined as specific driving states, a specific phase is a phase in which a connection point between the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit and the winding is different from that between the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit, and the connection point ... and the winding. the drive pattern includes two modes selectable for the same command voltage, the specific phases during which the specific drive states are respectively different from each other; a current flowing through the specific phase during a period in which each of the specific drive states is set is defined as a specific phase current; The selection unit is selecting the drive pattern based on the command voltage so that a period during which each of the specific drive states occurs within one switching period; a control device for a three-level inverter that selects, from the modes included in the selected drive pattern, a mode in which a change in the stored charge of the first storage unit and a change in the stored charge of the second storage unit due to the specific phase current are larger, based on the command voltage and the current flowing through the winding of each phase.

3. 3. The control device for a three-level inverter according to claim 1 or 2, further comprising an adjustment unit that adjusts a ratio of an appearance period of each of the specific drive states to a total appearance period of each of the specific drive states included in the drive pattern in one switching period, based on at least one of a voltage of the first storage unit and a voltage of the second storage unit.

4. The control device for a three-level inverter according to claim 1 , wherein the selection unit selects the drive pattern such that each of the specific drive states appears before the drive state changes three times.

5. 3. The control device for a three-level inverter according to claim 1 or 2, wherein the selection unit selects the drive pattern such that the first drive state and the last drive state in one switching period are the specific drive states, and the specific drive state that appears first in the current switching period and the specific drive state that appears last in the previous switching period are the same drive state.

6. a driving state in which the winding of each phase is 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 is defined as a zero voltage driving state; The control device for a three-level inverter according to claim 5 , wherein the selection unit selects the drive pattern so as to include, among the zero voltage drive states, a drive state in which the winding of each phase and the neutral point are connected.

7. in the three-level inverter, a conduction loss caused by a current flowing through each switch is larger when the winding of each phase is connected to the neutral point by the switch than when the positive electrode side of the first storage unit or the negative electrode side of the second storage unit is connected to the winding of each phase by the switch, a determination unit that determines whether an operating point of the rotating electric machine is within a specific range in which a conduction loss caused by a current flowing through the switch is equal to or greater than a tolerable value; 7. The control device for a three-level inverter according to claim 6, wherein the switch control unit performs the switching control such that, when it is determined that the voltage is within the specific range, a period during which the winding of each phase and the neutral point are connected is shortened during a period during which the switch is in the zero voltage drive state compared to a case where it is determined that the voltage is outside the specific range.

8. A first storage unit (21) and a second storage unit (22) connected in series; A rotating electric machine (10) having three phase windings (11U to 11W); a three-level inverter (30) having three-phase switches (SUH to SWL, QU to QW, Su1 to Sw4) connecting the windings of each phase in the rotating electric machine to any of the positive electrode side of the first storage unit, the neutral point between the negative electrode side of the first storage unit and the positive electrode side of the second storage unit, and the negative electrode side of the second storage unit, the program being executed by a computer (40), a selection step of selecting a drive pattern which is a combination of drive states of the switches of each phase in one switching period based on a command voltage vector for controlling a control amount of the rotary electric machine to a command value; a control step of controlling switching of the switch based on the selected drive pattern; A vector space in which the command voltage vector exists is divided into six sectors with respect to the deflection angle of the command voltage vector, each of the sectors includes a first region and a second region; In each of the sectors, when an end point of the sector on one of the two-phase axes dividing the sector with the smaller deflection angle is defined as a first end point, an end point of the sector on one of the two-phase axes dividing the sector with the larger deflection angle is defined as a second end point, a midpoint between the origin of the vector space and the first end point is defined as a first intermediate point, a midpoint between the origin and the second end point is defined as a second intermediate point, and a midpoint between the first end point and the second end point is defined as an intermediate end point, the first region is defined as a region surrounded by a triangle with vertices at the origin, the first intermediate point, and the second region is defined as a region surrounded by a triangle with vertices at the first intermediate point, the second intermediate point, and the intermediate end point, two different driving states for outputting each phase voltage at the first intermediate point or the second intermediate point, in which three line voltages of the winding are equal and the directions of currents flowing through the neutral point are opposite to each other, are defined as specific driving states; In the selection step, the drive pattern being a combination of the drive states for outputting each phase voltage at the origin, the first intermediate point, and the second intermediate point when the command voltage vector is in the first region of any of the sectors, the drive pattern being selected such that a period during which each of the specific drive states occurs within one switching period; A program for selecting the drive pattern which is a combination of the drive states that output each phase voltage at the first intermediate point, the second intermediate point and the intermediate end point when the command voltage vector is in the second region of any of the sectors, and which selects the drive pattern such that a period in which each of the specific drive states occurs within one switching period.

9. A first storage unit (21) and a second storage unit (22) connected in series; A rotating electric machine (10) having three phase windings (11U to 11W); a three-level inverter (30) having three-phase switches (SUH to SWL, QU to QW, Su1 to Sw4) connecting the windings of each phase in the rotating electric machine to any of the positive electrode side of the first storage unit, the neutral point between the negative electrode side of the first storage unit and the positive electrode side of the second storage unit, and the negative electrode side of the second storage unit, the program being executed by a computer (40), a selection step of selecting a drive pattern which is a combination of drive states of the switches of each phase in one switching period based on a command voltage for controlling a control amount of the rotary electric machine to a command value; a control step of controlling switching of the switch based on the selected drive pattern; Two different driving states in which three line voltages of the winding are equal and the directions of currents flowing through the neutral point are opposite to each other are defined as specific driving states, a specific phase is a phase in which a connection point between the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit and the winding is different from that between the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit, and the connection point ... and the winding. the drive pattern includes two modes selectable for the same command voltage, the specific phases during which the specific drive states are respectively different from each other; a current flowing through the specific phase during a period in which each of the specific drive states is set is defined as a specific phase current; In the selection step, selecting the drive pattern based on the command voltage so that a period during which each of the specific drive states occurs within one switching period; a program for selecting, from among the modes included in the selected drive pattern, a mode in which a change in the stored charge of the first storage unit and a change in the stored charge of the second storage unit due to the specific phase current are larger, based on the command voltage and the current flowing through the winding of each phase.

10. A first storage unit (21) and a second storage unit (22) connected in series, A rotating electric machine (10) having three phase windings (11U to 11W); a three-level inverter (30) having three-phase switches (SUH to SWL, QU to QW, Su1 to Sw4) connecting the windings of each phase in the rotating electric machine 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, a selection step of selecting a drive pattern which is a combination of drive states of the switches of each phase in one switching period based on a command voltage vector for controlling a control amount of the rotating electric machine to a command value; A control step of performing switching control of the switch based on the selected drive pattern, A vector space in which the command voltage vector exists is divided into six sectors with respect to the deflection angle of the command voltage vector, each of the sectors includes a first region and a second region; In each of the sectors, when an end point of the sector on one of the two-phase axes dividing the sector with the smaller deflection angle is defined as a first end point, an end point of the sector on one of the two-phase axes dividing the sector with the larger deflection angle is defined as a second end point, a midpoint between the origin of the vector space and the first end point is defined as a first intermediate point, a midpoint between the origin and the second end point is defined as a second intermediate point, and a midpoint between the first end point and the second end point is defined as an intermediate end point, the first region is defined as a region surrounded by a triangle with vertices at the origin, the first intermediate point, and the second region is defined as a region surrounded by a triangle with vertices at the first intermediate point, the second intermediate point, and the intermediate end point, two different driving states for outputting each phase voltage at the first intermediate point or the second intermediate point, in which three line voltages of the winding are equal and the directions of currents flowing through the neutral point are opposite to each other, are defined as specific driving states; In the selection step, the drive pattern being a combination of the drive states for outputting each phase voltage at the origin, the first intermediate point, and the second intermediate point when the command voltage vector is in the first region of any of the sectors, the drive pattern being selected such that a period during which each of the specific drive states occurs within one switching period; a drive pattern that is a combination of drive states that output each phase voltage at the first intermediate point, the second intermediate point, and the intermediate end point when the command voltage vector is in the second region of any of the sectors, and the drive pattern is selected so that a period in which each of the specific drive states occurs within one switching period.

11. A first storage unit (21) and a second storage unit (22) connected in series, A rotating electric machine (10) having three phase windings (11U to 11W); a three-level inverter (30) having three-phase switches (SUH to SWL, QU to QW, Su1 to Sw4) connecting the windings of each phase in the rotating electric machine 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, a selection step of selecting a drive pattern which is a combination of drive states of the switches of each phase in one switching period based on a command voltage for controlling a control amount of the rotary electric machine to a command value; A control step of performing switching control of the switch based on the selected drive pattern, Two different driving states in which three line voltages of the winding are equal and the directions of currents flowing through the neutral point are opposite to each other are defined as specific driving states, a specific phase is a phase in which a connection point between the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit and the winding is different from that between the positive electrode side of the first power storage unit, the neutral point, or the negative electrode side of the second power storage unit, and the connection point ... and the winding. the drive pattern includes two modes selectable for the same command voltage, the specific phases during which the specific drive states are respectively different from each other; a current flowing through the specific phase during a period in which each of the specific drive states is set is defined as a specific phase current; In the selection step, selecting the drive pattern based on the command voltage so that a period during which each of the specific drive states occurs within one switching period; A control method for a three-level inverter, comprising: selecting, from among the modes included in the selected drive pattern, a mode in which a change in the stored charge of the first storage unit and a change in the stored charge of the second storage unit due to the specific phase current are larger, based on the command voltage and the current flowing through the winding of each phase.

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