Rotating electric machine control system

Abstract

A rotating electric machine control system (100) that controls an alternating-current rotating electric machine (80) in which two coil groups (8) of an N phase are arranged in the same stator core includes a first inverter (51), a second inverter (52), and an inverter control device (10) that individually controls the two inverters (50) in such a manner that currents of different phases flow through the two coil groups (8), respectively. The inverter control device (10) stops the second inverter (52) and switch-controls the first inverter (51) to convert electric power between direct current and alternating current of the N phase, or switch-controls the two inverters (50) to convert electric power between direct current and alternating current of 2N phases. Switching elements (5) that constitute the first inverter (51) have a shorter transition time between an off state and an on state and less switching loss than switching elements (5) that constitute the second inverter (52).

Description

TECHNICAL FIELD

[0001] The present application relates to a rotating electric machine control system that takes as a control target a rotating electric machine of alternating current that has a plurality of coil groups. BACKGROUND

[0002] In Japanese Patent Application Publication No. 2018-130007, a rotating electric machine control device (10) is disclosed that controls a rotating electric machine (80) that has stator windings (180, 280) of a plurality of systems as a plurality of coil groups (in the background art, the reference numerals in parentheses are those of the reference document). The rotating electric machine control device (10) controls in a manner in which phase currents that are 30 degrees out of phase are passed through the stator windings (180, 280) of the two systems (referred to as "phase difference current passing"). When phase difference current passing is performed, the output torque is improved compared to when phase difference current passing is not performed, and the torque pulsation of harmonics is also reduced, and noise, vibration is also alleviated.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENTS

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-130007 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, although not explicitly stated in the document, in the case of performing such phase difference current passing, the stator windings of each coil group are arranged adjacent to each other. Therefore, the mutual inductance between the adjacent stator windings cannot be ignored. Also, in association with this mutual inductance, the influence of the interline electromotive force between the adjacent stator windings also becomes large. In particular, in the case where the switching frequency of the inverter is low, the iron loss of the rotating electric machine increases due to both the low frequency current harmonics (for example, 5th order harmonics, 7th order harmonics) and the harmonics of the switching frequency, thereby reducing the system efficiency. For example, it is also considered to cope by increasing the switching frequency of the inverter, but it is necessary to use a switching device that can correspond to a higher switching frequency, and there is a possibility of increasing the system cost.

[0008] In view of the above background, in a system that takes as a control target a rotating electric machine of alternating current that has two coil groups, it is desirable to suppress an increase in system cost and improve system efficiency.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] In view of the above-described rotating electric machine control system, as one mode, a control system for an alternating-current rotating electric machine in which N-phase (N is a natural number) first coil groups and N-phase second coil groups are arranged in the same stator core, includes: a first inverter connected to a direct-current power supply and the first coil groups, which converts electric power between direct current and N-phase alternating current; a second inverter connected to the direct-current power supply and the second coil groups, which converts electric power between direct current and N-phase alternating current; and an inverter control device that generates switching control signals for individually controlling the first inverter and the second inverter, and controls the first inverter and the second inverter in such a manner that currents of different phases flow through the first coil groups and the second coil groups, respectively. The inverter control device is a device that stops the second inverter and switching-controls the first inverter to convert electric power between direct current and N-phase alternating current, or a device that switching-controls both the first inverter and the second inverter to convert electric power between direct current and 2N-phase alternating current. Switching elements that constitute the first inverter have a shorter transition time between an off state and an on state, and a smaller switching loss, than switching elements that constitute the second inverter.

[0011] One of the advantages of the rotating electric machine having two coil groups is that, by including two inverters corresponding to the two coil groups, it is possible to reduce the load on each inverter and to flow a larger alternating current, thereby increasing the torque of the rotating electric machine. However, depending on the required torque, it is also possible to cause the rotating electric machine to output the required torque by an alternating current that can be handled by one inverter. In the case where the second inverter is stopped and the first inverter is switching-controlled, since no current is supplied from the second inverter to the second coil groups, the iron loss due to mutual inductance between the first coil groups and the second coil groups is also suppressed. On the other hand, for example, in the case where the required torque is high and an alternating current that can be handled by both inverters is required, it is possible to cause a 2N-phase alternating current to flow through the rotating electric machine, and thus it is possible to increase the output torque compared to the case where an N-phase alternating current flows through the rotating electric machine. That is, according to the present structure, it is possible to switch the control mode between control using one inverter and control using both inverters as needed. In this case, the first inverter that operates individually always operates, but the second inverter is sometimes stopped. If the switching elements that constitute the first inverter, which has a higher operating rate, are switching elements that have a smaller switching loss than the switching elements that constitute the second inverter, it is possible to reduce the overall system loss. Generally, since such switching elements that have a small switching loss are expensive, by using switching elements that have a small switching loss only in the first inverter, which is one of the two inverters, it is possible to suppress an increase in the overall system cost. That is, according to the present structure, in a system in which an alternating-current rotating electric machine having two coil groups is the control target, it is possible to suppress an increase in the system cost and to improve the system efficiency.

[0012] Further features and advantages of the rotating electric machine control system will become apparent from the following description of an embodiment with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a block diagram showing an example of a rotating electric machine control system.

[0014] Figure 2 is a diagram showing an example of a configuration of a first coil group and a second coil group.

[0015] Figure 3 is a diagram comparing 6-phase AC and 3-phase AC in a current-torque characteristic.

[0016] Figure 4 is a diagram comparing 6-phase AC and 3-phase AC in a speed-torque characteristic.

[0017] Figure 5 is a diagram showing a distribution of harmonic components of a magnetomotive force.

[0018] Figure 6 is a diagram showing a ratio of a harmonic component to a primary component of a back electromotive force.

[0019] Figure 7 is a waveform diagram showing an example of a back electromotive force of 6-phase AC.

[0020] Figure 8 is a waveform diagram showing an example of a back electromotive force of 3-phase AC.

[0021] Figure 9 is a waveform diagram showing an example of a current waveform of 6-phase AC.

[0022] Figure 10 is a waveform diagram showing an example of a current waveform of 6-phase AC.

[0023] Figure 11 is a waveform diagram showing an example of a current waveform of 6-phase AC.

[0024] Figure 12 is a waveform diagram showing an example of a current waveform of 3-phase AC based on one coil group.

[0025] Figure 13 is a waveform diagram showing an example of a current waveform of 3-phase AC based on one coil group.

[0026] Figure 14 is a speed-torque diagram of a rotating electric machine.

[0027] Figure 15 is an explanatory diagram showing a relationship between a dq-axis orthogonal vector coordinate system and a 3-phase coordinate system.

[0028] Figure 16 is a graph showing an operation point of a rotating electric machine in a dq orthogonal coordinate system.

[0029] Figure 17 is a block diagram of a rotating electric machine control system provided with an inverter of a comparative example.

[0030] Figure 18 is a block diagram of a rotating electric machine control system provided with an inverter of a comparative example.

[0031] Figure 19 is a block diagram showing an example of an inverter control device.

[0032] Figure 20 is a block diagram showing a comparative example of a rotating electric machine control system.

[0033] Figure 21 is a graph showing the configuration of a first coil group and a second coil group of a comparative example. DETAILED DESCRIPTION

[0034] Hereinafter, an embodiment of a rotating electric machine control system will be described based on the drawings. The rotating electric machine control system drives controls a rotating electric machine, for example, as a driving power source of a vehicle. Figure 1 is a block diagram schematically showing the system structure of a rotating electric machine control system 100. The rotating electric machine control system 100 is an alternating current rotating electric machine 80 provided with two (a first coil group 81 and a second coil group 82) N-phase (N is a natural number) coil groups 8 as a control object. The two coil groups 8 are coil groups 8 of the same specifications (the same structure and the same electrical specifications), and in the present embodiment, are both 3-phase (N = 3) coil groups 8.

[0035] The rotating electric machine 80, which is a driving object of the rotating electric machine control system 100, is a permanent magnet type rotating electric machine (PMSM: Permanent Magnet Synchronous Motor) having a stator 80s (refer to Figure 2 , Figure 15 ) in which two coil groups 8 are arranged in the same stator core and a rotor 80r (refer to Figure 15 ) in which a permanent magnet 80m is arranged in a rotor core. In the present embodiment, as shown in Figure 1 , the first coil group 81 and the second coil group 82 are each composed of 3-phase stator coils (U-phase coil 8u, V-phase coil 8v, W-phase coil 8w) in a star connection (Y-connection) in which the neutral points NP are short-circuited. Note that the rotating electric machine 80 can function as a motor and as a generator.

[0036] The rotating electric machine control system 100 includes two inverters 50 connected to a direct current power supply 41 and each coil group 8 to convert electric power between direct current and N-phase alternating current. In the present embodiment, as shown inFigure 1 As shown, the rotary electric machine control system 100 includes a first inverter 51 connected to the direct current power supply 41 and the first coil group 81 to convert electric power between direct current and N-phase (in this case, 3-phase) alternating current, and a second inverter 52 connected to the direct current power supply 41 and the second coil group 82 to convert electric power between direct current and N-phase (in this case, 3-phase) alternating current. That is, the rotary electric machine control system 100 has two inverters 50 corresponding to the two coil groups 8. As shown in FIG. 1, the first inverter 51 and the second inverter 52 are connected to the direct current power supply 41 via a direct current bus 43. As shown in FIG. 1, the first inverter 51 and the second inverter 52 are connected to the coil groups 8 via a bus bar 44. As shown in FIG. 1, the first inverter 51 and the second inverter 52 are connected to the direct current power supply 41 via a direct current bus 43. As shown in FIG. 1, the first inverter 51 and the second inverter 52 are connected to the coil groups 8 via a bus bar 44. Figure 1 As shown, the first inverter 51 and the second inverter 52 are inverters 50 of different specifications (same circuit structure, different electrical specifications). Note that, as described later, each inverter 50 is switch-controlled at different timings so that electric currents of different phases flow through the first coil group 81 and the second coil group 82, respectively. Therefore, by the two inverters 50, electric power is converted between direct current and 2N-phase (in this case, 6-phase) alternating current between the direct current power supply 41 and the rotary electric machine 80.

[0037] The direct current power supply 41 is constituted by, for example, a secondary battery (battery) such as a lithium ion battery, which can be charged, a double layer capacitor, or the like. In the case where the rotary electric machine 80 is a driving power source of a vehicle, the direct current power supply 41 is a direct current power supply of large voltage and large capacity, and the rated power supply voltage is, for example, 200 to 400 V. On the direct current side of the inverter 50, a smoothing capacitor (direct current link capacitor 42) that smoothes the voltage (direct current link voltage "Vdc") between the positive electrode and the negative electrode is included.

[0038] Each inverter 50 is constituted to have a plurality of switching devices 5. In each switching device 5, the direction from the negative electrode toward the positive electrode (the direction from the lower stage side toward the upper stage side) is taken as the forward direction, and a freewheeling diode 5D is included in parallel. In the switching device 5, a power semiconductor device such as an Insulated Gate Bipolar Transistor (Si-IGBT) using silicon (Si) as a base material, a Metal Oxide Semiconductor Field Effect Transistor (Si-MOSFET), a Silicon Carbide-Metal Oxide Semiconductor FET (SiC-MOSFET) using silicon carbide (SiC) as a base material, a Silicon Carbide-Static Induction Transistor (SiC-SIT), a SiC-IGBT, and a Gallium Nitride-MOSFET (GaN-MOSFET) using gallium nitride (GaN) as a base material is used. In the case where the switching device 5 is a power semiconductor device using SiC as a base material, the withstand voltage of the switching device 5 is higher than that of a power semiconductor device using Si as a base material. Therefore, the switching device 5 can be used in a higher voltage range than the switching device 5 using Si as a base material. In the case where the switching device 5 is a power semiconductor device using GaN as a base material, the withstand voltage of the switching device 5 is higher than that of a power semiconductor device using SiC as a base material. Therefore, the switching device 5 can be used in a higher voltage range than the switching device 5 using SiC as a base material. Figure 1As the switching device 5, a Si-IGBT is used in the second inverter 52, and a SiC-MOSFET, which has a shorter transition time between the off state and the on state than the switching device (Si-IGBT) of the second inverter and has small switching loss, is used in the first inverter 51.

[0039] In the past, as the switching device 5 of the inverter 50, a Si-IGBT using silicon (Si) as a base material has been widely used. In recent years, as a base material of a MOSFET and an IGBT for electric power, a semiconductor material such as silicon carbide (SiC) and gallium nitride (GaN) has also been put into practical use. The semiconductor material such as SiC and GaN has higher basic performance as a raw material of a semiconductor material than Si, and, for example, has a wider band gap (wide band gap semiconductor) and a higher dielectric breakdown strength than Si. Since the dielectric breakdown strength is high, in a high-voltage power device (power switching device) using SiC and GaN as a base material, the film thickness of a drift layer can be made thinner than that of a device using Si as a base material. Since the resistance component of the high-voltage power device is mostly due to the thickness of the drift layer, in the high-voltage power device using SiC and GaN as a base material, a device having a very low on-resistance per unit area can be realized compared to a device using Si as a base material.

[0040] In the high-voltage power device using Si as a base material, in order to improve the increase in on-resistance with high-voltage, an IGBT (Si-IGBT) having a structure of a minority carrier device, i.e., a bipolar transistor, has become mainstream. The IGBT is a switching device having a FET structure in an input stage and a bipolar transistor structure in an output stage on one semiconductor device. However, the IGBT has large switching loss, for example, when compared to a MOSFET, and is affected by heat generated thereby, so there is a limit to switching at a high frequency. In the high-voltage power device using SiC and GaN as a base material, as described above, since the drift layer can be made thin, it is a high-speed device structure, and even in a majority carrier device, i.e., a MOSFET structure, the increase in on-resistance with high-voltage can be suppressed. That is, the high-voltage power device using SiC and GaN as a base material can realize high-voltage, low on-resistance, and high-frequency operation.

[0041] For example, compared to the Si-IGBT, the SiC-MOSFET can perform a higher-speed switching and can be used at a higher switching frequency. In addition, reduction in loss of the inverter 50 can also be expected. However, SiC and GaN are more expensive than Si, so the cost of the inverter 50 and the rotating electric machine control system 100 including the inverter 50 can increase.

[0042] Each inverter 50 includes multiple (three in this case) arms of AC single-phase quantity formed by series circuits of upper-side switching devices 5H and lower-side switching devices 5L. In this embodiment, each series circuit (arm) corresponds to a bridge circuit for each stator coil (8u, 8v, 8w) corresponding to the U-phase, V-phase, and W-phase of each coil group 8. The midpoint of the arm, i.e., the connection point between the upper-side switching device 5H and the lower-side switching device 5L, is connected to the stator coil (8u, 8v, 8w) corresponding to the U-phase, V-phase, and W-phase of each coil group 8.

[0043] like Figure 1 As shown, each inverter 50 is controlled by an inverter drive unit 30. The inverter drive unit 30 includes an inverter control unit 10 (CTRL) and a drive circuit 20 (DRV). See detailed description for reference. Figure 19 As described later, the inverter control device 10 includes a first control unit 10a for controlling the first inverter 51 and a second control unit 10b for controlling the second inverter 52, which independently generate switching control signals for the first inverter 51 and the second inverter 52, respectively, to control the first inverter 51 and the second inverter 52. Furthermore, a first drive circuit 21 is provided corresponding to the first inverter 51 and the first control unit 10a, and a second drive circuit 22 is provided corresponding to the second inverter 52 and the second control unit 10b.

[0044] The inverter control unit 10 is constructed with a processor such as a microcomputer as its core component. For example, the inverter control unit 10 is based on a target torque (torque command T) of the rotating motor 80 provided as a request signal from a higher-level control device, such as a vehicle control device (not shown) or other control devices. ＊ :Reference Figure 19 The inverter 50 controls the rotating motor 80 via current feedback control using vector control. Figure 15 As shown, in vector control, the coordinates of the actual current (Iu, Iv, Iw) flowing through the rotating motor are converted into vector components (Id, Iq) of the direction of the magnetic field (magnetic flux) generated by the permanent magnet 80m positioned on the rotor 80r, i.e., the d-axis, and the direction orthogonal to the d-axis (the direction of electrical angle advancement of π / 2 relative to the direction of the magnetic field), for feedback control. It should be noted that "Ia" indicates the resultant current of the vector synthesis. (Refer to...) Figure 19 As will be described later, in the dq-axis orthogonal vector coordinate system, the inverter drive unit 30 (inverter control unit 10) operates according to the torque command T based on the rotating motor 80. ＊ Current command (I ＊ The deviation between the actual current and the feedback control of the rotary motor 80 is used.

[0045] like Figure 1As shown, the actual current flowing through the rotary electric machine 80 (coil group 8) is detected by two current sensors 6 (SEN-I), and the detection result is acquired by the inverter control device 10. In the present embodiment, a first current sensor 61 that detects the alternating current flowing through each phase of the first coil group 81 and a second current sensor 62 that detects the alternating current flowing through each phase of the second coil group 82 are included. In the present embodiment, the first current sensor 61 and the second current sensor 62 are provided on the same substrate 6a, and the detection result is acquired by the inverter control device 10. Figure 1 In the present embodiment, a method in which the current sensor 6 detects the alternating current of all phases is shown, but for example in the case of 3-phase alternating current, 3-phase balance, the sum of the instantaneous values of which is zero, so it is also possible to detect the current of only 2 phases and the remaining 1 phase is acquired by the inverter control device 10 by calculation.

[0046] In addition, as shown in FIG. 1, the rotor 80r of the rotary electric machine 80 is provided with a permanent magnet 80m, and the magnetic pole position (electrical angle θ: refer to FIG. 2) of the rotor 80r at each timing, the rotational speed (angular velocity ω: refer to FIG. 3) of the rotor 80r, and the like are detected by a rotary sensor 7 (SEN-R) such as a resolver, and the detection result is acquired by the inverter control device 10. Figure 1 Figure 15 Figure 19 , the magnetic pole position (electrical angle θ: refer to FIG. 2) of the rotor 80r at each timing, the rotational speed (angular velocity ω: refer to FIG. 3) of the rotor 80r, and the like are detected by a rotary sensor 7 (SEN-R) such as a resolver, and the detection result is acquired by the inverter control device 10. The inverter control device 10 uses the detection results of the current sensor 6 and the rotary sensor 7 to perform current feedback control. Figure 19

[0047] The control terminal of each switching device 5 (for example, the gate terminal of an IGBT, an FET) constituting the inverter 50 is connected to the inverter control device 10 via a drive circuit 20, and each switching device 5 is individually switched and controlled. The inverter control device 10 that generates the switching control signal is configured with a microcomputer or the like as a core as described above, and the operating voltage thereof is, for example, 5 V, 3.3 V, 2.5 V, or the like. On the other hand, as described above, the inverter 50 is connected to a DC power supply 41 of which the rated power supply voltage is, for example, 200 to 400 V, and it is necessary to input a drive signal of, for example, 15 to 20 V to the control terminal of the switching device 5. The drive circuit 20 individually increases the drive capability (for example, the voltage amplitude, the output current, or the like that makes the circuit of the subsequent stage operate) of the switching control signal generated by the inverter control device 10 and relays it to the inverter 50.

[0048] Figure 2 An example of the arrangement of the stator coils (81u, 81v, 81w) of the first coil group 81 and the stator coils (82u, 82v, 82w) of the second coil group 82 that are wound on the slots 8s formed in the stator 80s of the rotary electric machine 80 is shown. This corresponds to 6 phases (2N phases) of alternating current as described above. As shown in FIG. 4, the stator coils of the first coil group 81 and the stator coils of the second coil group 82 are arranged in the slots 8s of the stator 80s in a manner that the phases of the first coil group 81 and the phases of the second coil group 82 are alternately arranged. Figure 2 ​​​As shown, the stator coils are arranged in the following repeating order: first U-phase coil 81u of the first coil group 81, second U-phase coil 82u of the second coil group 82, first V-phase coil 81v of the first coil group 81, second V-phase coil 82v of the second coil group 82, first W-phase coil 81w of the first coil group 81, and second W-phase coil 82w of the second coil group 82. Since the stator coils of the first coil group 81 (first system) and the stator coils of the second coil group 82 (second system) are adjacent, mutual inductance exists between the systems.

[0049] The coils of the first coil group 81 in phase are arranged with an electrical angle separation of 180 degrees. Similarly, the coils of the second coil group 82 in phase are also arranged with an electrical angle separation of 180 degrees. The first coil group 81 and the second coil group 82 are arranged with an electrical angle separation of 30 degrees. For example, the first U-phase coil 81u and the second U-phase coil 82u, the first V-phase coil 81v and the second V-phase coil 82v, and the first W-phase coil 81w and the second W-phase coil 82w are each arranged with an electrical angle separation of 30 degrees. The inverter control device 10 generates switching control signals to control the first inverter 51 and the second inverter 52 separately, so that currents of different phases flow through the first coil group 81 and the second coil group 82.

[0050] Figure 20 It shows relative to Figure 1 Comparative example of a rotating electric motor control system 100, Figure 21 It shows as relative to Figure 2 A comparative example of stator coil configuration. For example... Figure 20 As shown, each inverter 50 is switched on and off at the same timing, converting power between the DC power supply 41 and the rotating motor 80, and between DC and N-phase (here, 3-phase) AC. Figure 21 As shown, the first coil group 81 groups the first U-phase coil 81u, two first V-phase coils 81v, two first W-phase coils 81w, and the first U-phase coil 81u together, repeating this configuration four times. Next, the second coil group 82 groups the second U-phase coil 82u, two second V-phase coils 82v, two second W-phase coils 82w, and the second U-phase coil 82u together, repeating this configuration four times in the same way. In this configuration, the stator coils of the first coil group 81 (first system) and the stator coils of the second coil group 82 (second system) are not adjacent except for a portion of the U-phase coil, thus resulting in almost no mutual inductance between the systems.

[0051] exist Figure 20 and Figure 21In the comparative example shown, currents of the same phase flow through the in-phase coils of the first coil group 81 and the second coil group 82. For example, the first U-phase coils 81u and the second U-phase coils 82u are arranged at an electrical angle of 180 degrees apart, but since currents of the same phase flow through the first U-phase coils 81u and the second U-phase coils 82u, as a result, the in-phase coils of the first coil group 81 and the in-phase coils of the second coil group 82 are arranged at an electrical angle of 150 degrees apart. Also, for example, currents of the same phase flow through the first U-phase coils 81u and the second U-phase coils 82u, so the first coil group 81 and the second coil group 82 are arranged at the same electrical angle.

[0052] As shown in Figure 3 the case where 6-phase AC is made to flow through the rotating electric machine 80 to drive, even if the currents are the same in terms of effective value, a larger torque is output compared to the case where 3-phase AC is made to flow to drive. According to experiments and simulations by the inventor, it was found that in 6-phase AC, the torque on the side where the current is large increases by about 4% compared to 3-phase AC. In the relationship between the torque and the rotational speed, as shown in Figure 4 it was found that in the region where the rotational speed is relatively low, the torque in 6-phase AC increases by about 2% compared to 3-phase AC, and becomes high efficiency. As the rotational speed becomes higher, the torque of 3-phase AC becomes larger, but the difference in torque is smaller compared to the region where the rotational speed is low. Note that, referring to Figures 6-8 As described later, the torque of 6-phase AC becomes smaller in the region where the rotational speed is high is related to the back electromotive force.

[0053] Figure 5 The distribution of the harmonic components of the magnetomotive force is shown. Based on the magnetomotive force of 6-phase AC, the 5th and 7th harmonic components are fewer compared to the magnetomotive force based on 3-phase AC. Due to this, the iron loss is reduced.

[0054] On the other hand, referring to Figure 2 As described above, in the case where the rotating electric machine 80 is driven by 6-phase AC, the stator coils of the first coil group 81 and the stator coils of the second coil group 82 through which currents of different phases flow are adjacent. Therefore, in the case where the rotating electric machine 80 is driven by 6-phase AC, the influence of the interline back electromotive force becomes larger compared to the case where the rotating electric machine 80 is driven by 3-phase AC. Figure 6 The ratio of the harmonic components to the primary component of the interline back electromotive force is shown. It was found that in the case where the rotating electric machine 80 is driven by 6-phase AC, the 5th and 7th harmonic components are larger compared to the case where the rotating electric machine 80 is driven by 3-phase AC.

[0055] Figure 7 The waveform chart of FIG. 8 shows an example of the back electromotive force in the case where the rotating electric machine 80 is driven by 6-phase AC, Figure 8The waveform chart shows an example of back electromotive force in the case where the rotary electric machine 80 is driven by 3-phase AC. In the case where the rotary electric machine 80 is driven by 6-phase AC, the distortion of the waveform of the back electromotive force becomes larger than in the case where the rotary electric machine 80 is driven by 3-phase AC due to the 5th harmonic component and the 7th harmonic component as described above. As described above, in the structure of the stator coil in the present embodiment, the stator coil of the first coil group 81 (first system) and the stator coil of the second coil group 82 (second system) are adjacent, and thus there is mutual inductance between the systems. This mutual inductance is one cause of the distortion of the waveform of the back electromotive force. This distortion is a harmonic component, and is a cause of electromagnetic noise and audible noise.

[0056] The following formula (1) represents a 3-phase voltage equation of the first coil group 81, and formula (2) represents a 3-phase voltage equation of the second coil group 82. In addition, the following formula (3) represents a 2-phase voltage equation of the first coil group 81, and formula (4) represents a 2-phase voltage equation of the second coil group 82. In the formulas, the subscripts of "u, v, w" represent the U phase, the V phase, and the W phase, respectively, the subscripts of "d, q" represent the d axis and the q axis, respectively, and the subscript of "a" represents the entirety of the first coil group 81 and the second coil group 82 (synthesis of 3 phases) respectively. "R" is a resistance component of the coil group 8, "L" is a self-inductance of the stator coil (8u, 8v, 8w) of each phase, "M" is mutual inductance, "EMF" is an electromotive force coefficient (torque coefficient). "p" is a differential operator. f

[0057] [Formula 1]

[0058]

[0059] [Formula 2]

[0060]

[0061] [Formula 3]

[0062]

[0063] [Formula 4]

[0064]

[0065] Detailed description Figure 19 As described later, the inverter control device 10 performs current feedback control to switch control the inverter 50 on the basis of the voltage equations of the above formulas (1) to (4). Figure 9 An example of a 6-phase current waveform generated by the control of the inverter control device 10 is shown. In the current feedback control, if the inverter control device 10 (the current control section 12 described later (see FIG. 2)) is improved, the waveform of the back electromotive force becomes more distorted, and the waveform of the current becomes more distorted. Figure 19 ​If the gain in the feedback control is increased by raising the cutoff frequency, the target (command) is theoretically reached quickly. However, in the case where there are disturbance factors against the feedback loop caused by mutual inductance and the like, if the feedback gain is increased by raising the cutoff frequency, there is a case where the control does not converge and current control cannot be performed. Figure 10 The waveform shown indicates a state where the control does not converge.

[0066] This can be improved by raising the modulation frequency (carrier frequency) of the inverter control device 10 (the modulation section 14 (refer to Figure 19 ) to be described later). For example, if the modulation frequency is raised in a state where the feedback gain is increased by raising the cutoff frequency (a state like the waveform of the output Figure 10 , the control converges, and the alternating current waveform stabilizes as shown in the waveform. Figure 11 Compared with the waveform of the output Figure 9 where the cutoff frequency is low and the feedback gain is also low, the waveform of the output Figure 11 where the modulation frequency is high has less distortion. The modulation frequency of the waveform of the output Figure 9 and Figure 10 is about twice as high as that of the waveform of the output Figure 11 .

[0067] That is, by modulating at a higher modulation frequency, an alternating current with less distortion can be caused to flow through the coil set 8. However, in order to switch control the inverter 50 using the switching control signal modulated at a high modulation frequency, it is necessary to configure the inverter 50 using switching devices 5 corresponding to switching at a high frequency. For example, in the manner shown in Figure 1 , SiC-MOSFETs are used as the switching devices 5 configuring the first inverter 51, but as shown in the waveform of the comparative example, Figure 17 if SiC-MOSFETs are also used as the switching devices 5 configuring the second inverter 52, it is possible to correspond to a high modulation frequency. However, as described above, since the unit price of the switching devices 5 such as SiC-MOSFETs is high, the cost of the rotating electric machine control system 100 increases.

[0068] In addition, referring to Figure 7 and Figure 8 As described above, the distortion of the counter electromotive force of the 3-phase alternating current is smaller than that of the 6-phase alternating current, and thus the distortion of the alternating current waveform is also smaller. Therefore, if only one inverter 50 is used and a 3-phase alternating current is passed through only one coil set 8, even if the cutoff frequency is raised and the feedback gain is increased and the modulation frequency is maintained, it is possible to perform control as Figure 12As shown, this causes the feedback control to converge. However, since the current flowing through the first coil group 81 and the second coil group 82 flows through only one coil group 8 (e.g., only the first coil group 81), the effective value of the AC current becomes twice. Therefore, this control method can be selected when the required torque of the rotating motor 80 is small, and the AC current that can be corresponding to one coil group 8 and one inverter 50 is sufficient. That is, if we consider that the effective value of the AC current flowing through one coil group 8 becomes twice, then as long as it is the operating region of the rotating motor 80 where the effective value of the AC current is relatively low, the distortion of the AC current waveform can be reduced by using one coil group 8 to carry three-phase AC current.

[0069] Here, when the modulation frequency is further increased, such as Figure 13 As shown, the distortion of the alternating current is further reduced. That is, if only one inverter 50 is used, and only one coil group 8 is supplied with three-phase alternating current, increasing the modulation frequency will result in increased feedback gain even if the cutoff frequency is increased. Figure 13 As shown, this causes the feedback control to converge. In this case, the modulation frequency can be sufficiently increased using only one inverter 50. Therefore, as... Figure 1 As shown, if Si-IGBTs are used only as the switching device 5 of the first inverter 51, and Si-IGBTs are used as the switching device 5 of the second inverter 52, the cost increase can be suppressed. That is, as in the comparative example... Figure 17 As shown, compared with using SiC-MOSFETs as the switching devices 5 for both the first inverter 51 and the second inverter 52, the cost of the inverter 50 can be reduced.

[0070] In this configuration, the inverter control device 10 stops the second inverter 52 and switches the first inverter 51, thereby converting power between DC and N-phase (3-phase) AC, or switches both the first inverter 51 and the second inverter 52, thereby converting power between DC and 2N-phase (6-phase) AC. Furthermore, the inverter control device 10 preferably switches the first inverter 51 at a first switching frequency and switches the second inverter 52 at a second switching frequency lower than the first switching frequency. Figure 11 and Figure 13 The comparison shows that waveform distortion is... Figure 13 Less common in the middle. That is, as in the comparative example. Figure 17As shown, in the case where the first inverter 51 is configured of SiC-MOSFET and the second inverter 52 is configured of Si-IGBT and the second inverter 52 is stopped and the first inverter 51 is driven by the signal modulated at the high modulation frequency, as compared with the case where both the first inverter 51 and the second inverter 52 are configured of SiC-MOSFET and driven by the signal modulated at the high modulation frequency, the cost is low and the distortion of the waveform is also suppressed.

[0071] Further, with reference to Figure 12 As described above, if only one inverter 50 is used and 3-phase alternating current is passed through only one coil set 8, even if the modulation frequency is not increased, the feedback control can be converged in a state where the cutoff frequency is increased and the feedback gain is increased. That is, as in the comparative example Figure 18 As shown, even in the case where both the first inverter 51 and the second inverter 52 are configured of Si-IGBT, the distortion of the waveform can be somewhat reduced. However, in Figure 12 and Figure 13 As is clear from the comparison between

[0072] Further, for example, in the rotary electric machine 80 that is a drive power source of a vehicle, driving based on various torques is required in starting, acceleration, climbing, cruising, and the like. In particular, in starting, acceleration, climbing, and the like, a relatively large torque is required. The operation region of the rotary electric machine 80 can be set in correspondence with various operating conditions, but the operation region of high frequency is not an operation region where such a large torque is required. Rather, it is an operation region of low torque and low speed or intermediate speed. Here, for example, as shown in Figure 14 As shown in the drawing, in the operation region of the rotary electric machine 80, a first region R1 of relatively low torque and intermediate speed, and a second region R2 of higher torque than the first region R1 are set.

[0073] For example, in the operation region of the rotary electric machine 80 prescribed by the torque and the speed of the rotary electric machine 80, in the first region R1, the inverter control device 10 stops the second inverter 52 and switch-controls the first inverter 51, thereby converting electric power between direct current and N-phase (in this case, 3-phase) alternating current. On the other hand, in the second region R2 of higher torque than the first region R1, the inverter control device 10 switch-controls the first inverter 51 and the second inverter 52, thereby converting electric power between direct current and 2N-phase (in this case, 6-phase) alternating current.

[0074] Note that, here, use is made of, for example, Figure 14The operation region of the rotary electric machine 80 based on the torque and the rotational speed is shown, and a first region Rl and a second region R2 in the operation region are shown. However, the first region Rl and the second region R2 are not limited to this manner, and can be set based on, for example, the DC link voltage "Vdc" and the back electromotive force.

[0075] Of course, the operation point of the rotary electric machine 80 also shifts between the first region Rl and the second region R2. Therefore, the inverter control device 10 switches the control mode between a state in which the second inverter 52 is stopped and the first inverter 51 is switching controlled and a state in which the first inverter 51 and the second inverter 52 are switching controlled. Before and after the switching, the rotary electric machine 80 preferably outputs the same torque. For example, in a case where the operation region of the rotary electric machine 80 shifts from the first region Rl to the second region R2, the inverter control device 10 switching controls the first inverter 51 and the second inverter 52 in a manner in which the current flowing through the first coil group 81 is reduced and a current corresponding to the reduced current flows through the second coil group 82 while maintaining the output torque of the rotary electric machine 80.

[0076] Figure 16 The operation point of the rotary electric machine 80 based on the current (d-axis current, q-axis current) in the dq-axis orthogonal coordinate system is shown. Reference sign "L3" is a maximum efficiency line (3-phase maximum efficiency line) indicating a vector locus of an operation point at which the torque is output with the highest efficiency in a case where the first inverter 51 is switching controlled only and the rotary electric machine 80 is driven by 3-phase AC. Reference sign "L6" is a maximum efficiency line (6-phase maximum efficiency line) indicating a vector locus of an operation point of one inverter 5 at which the torque is output with the highest efficiency in a case where the first inverter 51 and the second inverter 52 are switching controlled and the rotary electric machine 80 is driven by 6-phase AC. Reference sign "LT" is a vector locus of an operation point at which the same torque is output, that is, an equal torque line.

[0077] In Figure 16In the middle, the operating point of the rotating electric machine 80 is shown as the first operating point Pl, and the case where the state of switching control of the first inverter 51 is shifted to the operating point of switching control of the first inverter 51 and the second inverter 52, i.e., the third operating point P3. The inverter control device 10 lowers the current flowing through the first coil set 81 in the direction of the arrow Yl along the 3-phase maximum torque line L3 while maintaining the output torque of the rotating electric machine 80. At the same time, the inverter control device 10 starts to flow a current corresponding to the lowered current into the second coil set 82. The current flowing into the second coil set 82 rises in the direction of the arrow Y2 along the 3-phase maximum torque line L3. That is, the operating point defined by the currents flowing through the first coil set 81 and the second coil set 82 approaches the second operating point P2 along the 3-phase maximum efficiency line L3. Since the two operating points are moved in the direction of the arrow Y3 along the 3-phase maximum torque line L3 from a position sandwiching one operating point (the second operating point P2), the operating points can be moved with high system efficiency.

[0078] If the operating points defined by the currents flowing through the first coil set 81 and the second coil set 82 both reach the second operating point P2, the inverter control device 10 moves the operating points along the constant torque line LT to the third operating point P3 located at the intersection between the constant torque line LT and the 6-phase maximum efficiency line L6. Since the operating points are moved along the constant torque line LT, no torque fluctuation occurs other than the error of control. Detailed explanation is omitted, but the case where the operating points are moved from the third operating point P3 to the first operating point Pl is the same. In this way, the inverter control device 10 can smoothly switch the control mode between the state where the second inverter 52 is stopped and the first inverter 51 is switching controlled and the state where the first inverter 51 and the second inverter 52 are switching controlled.

[0079] At the second operating point P2 and the third operating point P3, i.e., on the constant torque line LT, the effective values of the currents flowing through the first coil set 81 and the second coil set 82 are the same. That is, in the second region R2, the inverter control device 10 switching controls the first inverter 51 and the second inverter 52 in such a manner that the currents having the same effective value flow through the first coil set 81 and the second coil set 82.

[0080] It should be noted that the feedback gain in the first region R1 is preferably set to a higher value than the feedback gain in the second region R2. When two inverters 50 energize two coil groups 8, interference is easily generated due to the mutual inductance between the two coil groups 8, and the higher the feedback gain, the more difficult it is for the control to converge. On the other hand, when only one coil group 8 (first coil group 81) is energized through one inverter 50 (first inverter 51), there is almost no interference caused by the mutual inductance, thus it is easier to increase the feedback gain compared to the case where both coil groups 8 are energized. Furthermore, the higher the feedback gain, the shorter the convergence time. Therefore, in the feedback control of the first region R1, which has a high frequency within the operating range of the rotating motor 80, using a feedback gain value higher than that used in the feedback control of the second region R2 can improve system efficiency.

[0081] The inverter control device 10 will be described in detail below. For example... Figure 19 As shown, the inverter control device 10 has various functional units for current feedback control, and each functional unit is implemented by the cooperation between hardware such as a microcomputer and software (program).

[0082] In this embodiment, the inverter control device 10 includes a current command calculation unit 11, a current control unit 12, a voltage control unit 13, a modulation unit 14, and a 3-phase / 2-phase coordinate transformation unit 15. The inverter control device 10 includes a first control unit 10a that controls the first inverter 51 and a second control unit 10b that controls the second inverter 52. The current control unit 12, voltage control unit 13, modulation unit 14, and 3-phase / 2-phase coordinate transformation unit 15 each include a functional unit (first current control unit 12a, first voltage control unit 13a, first modulation unit 14a, and 3-phase / 2-phase first coordinate transformation unit 15a) included in the first control unit 10a and a functional unit (second current control unit 12b, second voltage control unit 13b, second modulation unit 14b, and 3-phase / 2-phase second coordinate transformation unit 15b) included in the second control unit 10b. Furthermore, the current command calculation unit 11 includes a unit for calculating torque command T... ＊ The first torque command T assigned to the first control unit 10a ＊ 1 and the second torque command T of the second control unit 10b ＊ The torque command allocation unit 110 (DIV) of 2, based on the first torque command T ＊ 1. Operation of the first current instruction I ＊ 1(First d-axis current command I) ＊ d1 First q-axis current command I ＊ q1 The first current command arithmetic unit 11a and the second torque command T ＊2 second current command I ＊ 2 (second d-axis current command I ＊ d2 , second q-axis current command I ＊ q2 ) of the second current command operation section 11b.

[0083] The inverter control device 10 switch-controls the first inverter 51 based on a deviation between a current command of the first coil group 81, i.e., a first current command (I ＊ ) set by the target torque (torque command T ＊ d1 , I ＊ q1 ) of the rotating electric machine 80 and a current (I d1 , I q1 ) flowing through the first coil group 81, and switch-controls the second inverter 52 based on a deviation between a current command of the second coil group 82, i.e., a second current command I ＊ 2 set by the target torque (torque command T ＊ ) of the rotating electric machine 80 and a current (I d2 , I q2 ) flowing through the second coil group 82, thereby current feedback-controls the rotating electric machine 80.

[0084] Hereinafter, first the first control section 10a is described, and then the second control section 10b is described, but since the first control section 10a and the second control section 10b are basically the same structure, there are cases where the description of the same part is appropriately omitted. The first current control section 12a operates a command of a voltage applied to the first coil group 81, i.e., a 2-phase voltage command (V ＊ d1 , V ＊ q1 ) based on a deviation between a 2-phase current command (I u1ph v1ph w1ph ) and a 2-phase actual current (I d1 , I q1 ) which is coordinate-converted from actual currents (U-phase current i ＊ d1 , V ＊ q1 ) of the rotating electric machine 80. The first current control section 12a includes a d-axis proportional integral control section 121 (PI), a q-axis proportional integral control section 122 (PI), a q-axis non-interference control section 123 (CRS), and a d-axis non-interference control section 124 (CRS).

[0085] The d-axis proportional integral control section 121 operates a d-axis current command (I ＊ ​​d1 ) and the d-axis current (I d1 ) to perform the operation shown in the following equation (5). The q-axis proportional integral control section 122 performs the operation shown in the following equation (6) based on the deviation between the q-axis current command (I ＊ q1 ) and the q-axis current (I q1 ). In the equations (5) and (6), "(P Id1 )" and "(P Iq1 )" are proportional gains, and are products of self-induction (L d1 or L q1 ) and a cutoff frequency in the d-axis and the q-axis, respectively. In addition, "(I Id1 )" and "(I Iq1 )" are products of the combined resistance value "Ra" of the first coil group 81, a control period [sec], and a cutoff frequency. In particular, in the case of switching control of only the first inverter 51, a short control period and a high cutoff frequency are preferably set. In the case of switching control of both the first inverter 51 and the second inverter 52, a low cutoff frequency is preferably set in order to suppress the influence of the interference voltage due to mutual induction. The high cutoff frequency is about 2 to 2.5 times the low cutoff frequency.

[0086] [Equation 5]

[0087]

[0088] [Equation 6]

[0089]

[0090] The q-axis non-interference control section 123 performs the operation shown in the following equation (7) based on the deviation between the d-axis current command (I ＊ d1 ) and the d-axis current (I d1 ). The d-axis non-interference control section 124 performs the operation shown in the following equation (8) based on the deviation between the q-axis current command (I ＊ q1 ) and the q-axis current (I q1 ). In the equation (7), "(I Idq1 )" is a product of the rotational speed (angular velocity ω), the d-axis self-induction L d1 , a control period [sec], and a cutoff frequency. In the equation (8), "(I Iqd1 )" is a product of the rotational speed (angular velocity ω), the q-axis self-induction L q1 , a control period [sec], and a cutoff frequency.

[0091] [Equation 7]

[0092]

[0093] [Equation 8]

[0094]

[0095] In addition, although Figure 19 Although not shown in the figure, the inverter control device 10 includes a feedforward calculation unit that calculates the d-axis feedforward value (V). d1 FF) and q-axis feedforward value (V q1 FF). Theoretically, the d-axis feedforward value (V d1 FF) and q-axis feedforward value (V q1 FF) is shown in equations (9) and (10) below.

[0096] [Equation 9]

[0097]

[0098] [Equation 10]

[0099]

[0100] However, regarding the differential terms of the third term in equation (9) and the fourth term in equation (10), since it is impossible to determine the current command (I... ＊ d1 I ＊ q1 Differentiate the terms and calculate the d-axis feedforward value (V) based on equations (11) and (12) below, in addition to these terms. d1 FF) and q-axis feedforward value (V q1 FF).

[0101] [Equation 11]

[0102]

[0103] [Equation 12]

[0104]

[0105] As shown in equation (13) below, the first current control unit 12a will use the calculation result (V) of the d-axis proportional-integral control unit 121. d1 The calculation results of the FB and d-axis non-interference control unit 124 (V) d1 cross) and the separately calculated d-axis feedforward value (V d1 The d-axis voltage command (V) is calculated by adding FF together. ＊ d1 Furthermore, as shown in equation (14) below, the first current control unit 12a will use the calculation result (V) of the q-axis proportional-integral control unit 122. q1FB) and an operation result (V q1 cross) and a separately operated q-axis feedforward value (V q1 FF) are added to operate a d-axis voltage command (V ＊ q1 ).

[0106] [Equation 13]

[0107]

[0108] [Equation 14]

[0109]

[0110] Note that the coordinate conversion from the actual currents (U-phase current i u1ph , V-phase current i v1ph , and W-phase current i w1ph ) of the 3 phases of the first coil set 81 to the actual currents (I d1 , I q1 ) of the 2 phases is performed by a 3-phase 2-phase first coordinate conversion section 15a. The 3-phase 2-phase first coordinate conversion section 15a performs coordinate conversion based on the rotational position (magnetic pole position, electrical angle θ) of the rotor 80r at each timing, i.e., the first electrical angle θ1 (= θ), which is detected by the rotational sensor 7 (SEN-R).

[0111] The first voltage control section 13a operates the voltage commands corresponding to the 3 phases of the first coil set 81 based on the 2-phase voltage commands (V ＊ d1 , V ＊ q1 ) of the dq-axis orthogonal vector coordinate system. The first voltage control section 13a includes a voltage operation section 131 that operates the 2-phase voltage based on the direct-current link voltage “Vdc” and a 2-phase 3-phase coordinate conversion section 132 that converts the 2-phase voltage to the voltage commands of the 3 phases.

[0112] The first modulation section 14a generates the switching control signals of the first inverter 51 based on the voltage commands of the respective 3 phases. Here, a manner in which the first modulation section 14a generates the switching control signals by pulse width modulation (PWM) based on carriers of the first switching frequency is shown. In the present embodiment, as shown in FIG. 1, the switching devices 5 of the first inverter 51 are SiC-MOSFETs, which are capable of switching based on a high switching frequency compared to Si-IGBTs. Therefore, the first switching frequency is preferably a frequency higher than the second switching frequency (for example, about 2 to 2.5 times). Figure 1

[0113] ​Next, the second control unit 10b will be described, but parts identical to those in the first control unit 10a will be omitted as appropriate. The second current control unit 12b is based on the two-phase current command (I ＊ d2 I ＊ q2 ) and the actual current of the rotating motor 80 (U-phase current i) u2ph Phase V current i v2ph Phase W current i w2ph The actual current (I) of the two phases undergoing coordinate transformation d2 I q2 The deviation between the two phases is used to calculate the voltage command applied to inverter 50, i.e., the voltage command for the two phases (V). ＊ d2 V ＊ q2 ).

[0114] like Figure 19 As shown, the second current control unit 12b also includes the same functional units as the first current control unit 12a. The d-axis proportional-integral control unit 121 is based on the d-axis current command (I... ＊ d2 ) and d-axis current (I d2 The q-axis proportional-integral control unit 122 performs the calculation as shown in equation (15) based on the deviation between the q-axis current command (I). ＊ q2 ) and q-axis current (I q2 The deviation between (P) and (15) is used to perform the operation as shown in equation (16) below. In equations (15) and (16), “(P)” Id2 " and "(P) Iq2 "This represents the proportional gain, which is the self-inductance (L) in each d-axis and q-axis." d2 or L q2 The product of (I) and the cutoff frequency. Additionally, "(I)" Id2 ” and “(I) Iq2 "Ra" is the product of the combined resistance value "Ra" of the second coil group 82, the control period [seconds], and the cutoff frequency.

[0115] [Equation 15]

[0116]

[0117] [Equation 16]

[0118]

[0119] The q-axis non-interference control unit 123 is based on the d-axis current command (I ＊ d2 ) and d-axis current (I d2The d-axis non-interference control unit 124 performs the calculation as shown in equation (17) based on the deviation between the d-axis and q-axis current commands (I). ＊ q2 ) and q-axis current (I q2 The deviation between (I) and (I) is used to perform the operation as shown in equation (18) below. In equation (17), “(I)” Idq2 "This refers to rotational speed (angular velocity ω) and d-axis self-inductance L." d2 The product of the control period [seconds] and the cutoff frequency, in equation (18), "(I) Iqd2 "This refers to the rotational speed (angular velocity ω) and the q-axis self-inductance L." q2 The product of the control period (seconds) and the cutoff frequency.

[0120] [Equation 17]

[0121]

[0122] [Equation 18]

[0123]

[0124] In addition, although Figure 19 Although not shown in the figure, the inverter control device 10 includes a feedforward calculation unit that calculates the d-axis feedforward value (V). d2 FF) and q-axis feedforward value (V q2 FF). Theoretically, the d-axis feedforward value (V d2 FF) and q-axis feedforward value (V q2 FF) is shown in equations (19) and (20) below.

[0125] [Equation 19]

[0126]

[0127] [Equation 20]

[0128]

[0129] However, for the differential terms of the third term in equation (19) and the fourth term in equation (20), since it is impossible to determine the current command (I) ＊ d2 I ＊ q2 Differentiate the terms and calculate the d-axis feedforward value (V) based on equations (21) and (22) below, in addition to these terms. d2 FF) and q-axis feedforward value (V q2 FF).

[0130] [Equation 21]

[0131]

[0132] [Equation 22]

[0133]

[0134] The second current control section 12b adds the operation result (V d2 FB) of the d-axis proportional integral control section 121, the operation result (V d2 cross) of the d-axis non-disturbance control section 124, and the separately operated d-axis feedforward value (V d2 FF) to operate the d-axis voltage command (V ＊ d2 ). In addition, as shown in the following Equation (24), the second current control section 12b adds the operation result (V q2 FB) of the q-axis proportional integral control section 122, the operation result (V q2 cross) of the q-axis non-disturbance control section 123, and the separately operated q-axis feedforward value (V q2 FF) to operate the d-axis voltage command (V ＊ q2 ).

[0135] [Equation 23]

[0136]

[0137] [Equation 24]

[0138] The coordinate conversion from the actual currents (U-phase current i u2ph , V-phase current i v2ph , W-phase current i w2ph ) of the 3 phases of the second coil set 82 to the actual currents (I d2 , I q2 ) of the 2 phases is performed by the 3-phase 2-phase second coordinate conversion section 15b. The 3-phase 2-phase second coordinate conversion section 15b performs coordinate conversion based on the rotational position (magnetic pole position, electrical angle θ) of the rotor 80r at each timing detected by the rotational sensor 7 (SEN-R). The coordinate conversion in the 3-phase 2-phase second coordinate conversion section 15b will be described later. Figure 2 As described above, the currents are controlled so as to flow through the first coil set 81 and the second coil set 82 with a phase difference of 30 degrees (π / 6). Therefore, the second electrical angle θ2 used in the coordinate conversion in the 3-phase 2-phase second coordinate conversion section 15b and the first electrical angle θ1 used in the coordinate conversion in the 3-phase 2-phase first coordinate conversion section 15a have a phase difference of 30 degrees (π / 6). The second electrical angle θ2 is "θ - π / 6" which is delayed by 30 degrees (π / 6) from the electrical angle θ detected by the rotational sensor 7.

[0139] The second voltage control section 13b operates a voltage command corresponding to the 3 phases of the second coil group 82, based on the 2-phase voltage command (V ＊ d1 , V ＊ q1 ), in the dq-axis orthogonal vector coordinate system. The second voltage control section 13b includes a voltage operation section 131 that operates a 2-phase voltage based on the DC link voltage "Vdc", and a 2-phase 3-phase coordinate conversion section 132 that converts the 2-phase voltage to a voltage command of 3 phases.

[0140] The second modulation section 14b generates a switching control signal of the second inverter 52, based on the voltage command of each of the 3 phases. Here, a manner in which the second modulation section 14b generates a switching control signal by pulse width modulation based on a carrier of the second switching frequency is shown.

[0141] In the present embodiment, as shown in Figure 1 , the switching device 5 of the first inverter 51 is a SiC-MOSFET, and is capable of switching at a high switching frequency compared to a Si-IGBT. Therefore, as described above, the first switching frequency is preferably a frequency higher than the second switching frequency (for example, about 2 to 2.5 times). In addition, the first inverter 51 is sometimes driven individually, in which case, refer to Figure 11 , Figure 13 As described above, it is preferable that the switching frequency be higher.

[0142] (Summary of Embodiment)

[0143] Hereinafter, a summary of the rotating electric machine control system (100) described in the above will be explained briefly.

[0144] As one mode, a rotating electric machine control system (100) of an alternating-current rotating electric machine (80) in which a first coil group (81) of N phases (N is a natural number) and a second coil group (82) of N phases are arranged in the same stator core, includes: a first inverter (51) connected to a direct-current power supply (41) and the first coil group (81) to convert electric power between direct current and alternating current of N phases; a second inverter (52) connected to the direct-current power supply (41) and the second coil group (82) to convert electric power between direct current and alternating current of N phases; and an inverter control device (10) that generates switching control signals to individually control the first inverter (51) and the second inverter (52) separately, and controls the first inverter (51) and the second inverter (52) in a manner that currents of different phases flow through the first coil group (81) and the second coil group (82) separately, the inverter control device (10) being a device that stops the second inverter (52) and switching controls the first inverter (51) to convert electric power between direct current and alternating current of N phases, or a device that switching controls both the first inverter (51) and the second inverter (52) to convert electric power between direct current and alternating current of 2N phases, a switching device (5) that constitutes the first inverter (51) having a shorter transition time between an off state and an on state and a smaller switching loss than a switching device that constitutes the second inverter (52).

[0145] One of the advantages of the rotary electric machine (80) having two coil groups (8) is that, by including two inverters (50) corresponding to the two coil groups (8), the load on the inverters (50) can be reduced and a larger AC current can flow, thereby increasing the torque of the rotary electric machine (80). However, depending on the required torque, the rotary electric machine (80) can output the required torque by the AC current corresponding to one inverter (50). In the case where the second inverter (52) is stopped and the first inverter (51) is switch-controlled, since no current is supplied from the second inverter (52) to the second coil group (82), the iron loss due to the mutual inductance between the first coil group (51) and the second coil group (52) is also suppressed. On the other hand, for example, in the case where the required torque is high and the AC current corresponding to both of the inverters (50) is required, the 2N-phase AC current can flow through the rotary electric machine (80), so the output torque can be increased compared to the case where the N-phase AC current flows through the rotary electric machine (80). That is, according to the present structure, the control mode can be switched between the control using one inverter (50) and the control using both of the inverters (50) as needed. In this case, the first inverter (51) alone is always operated, but the second inverter (52) is sometimes stopped. If the switching device (5) constituting the first inverter (51) having a higher operating rate is a device having a smaller switching loss than the switching device (5) constituting the second inverter (52), the overall system loss can be reduced. Since such a switching device (5) having a small switching loss is generally expensive, by using the switching device (5) having a small switching loss only in one of the two inverters (50), i.e., the first inverter (51), the increase in the overall system cost can be suppressed. That is, according to the present structure, in a system having the AC rotary electric machine (80) having two coil groups (8) as a control target, the increase in the system cost can be suppressed and the system efficiency can be improved.

[0146] Further, the inverter control device (10) preferably switch-controls the first inverter (51) at a first switching frequency and switch-controls the second inverter (52) at a second switching frequency lower than the first switching frequency.

[0147] Generally, a smaller distortion of the alternating current is obtained when the inverter (50) is switched at a higher switching frequency. Since this distortion is the cause of iron loss, vibration, and noise, it is desirable that the distortion of the alternating current be smaller. The switching device (5) that constitutes the first inverter (51) has a shorter transition time between the off state and the on state and a smaller switching loss than the switching device that constitutes the second inverter (52). Therefore, the switching device that constitutes the first inverter (51) can operate with high efficiency even at a higher switching frequency than the switching device that constitutes the second inverter (52). Therefore, by switching the first inverter (51) at a first switching frequency and switching the second inverter (52) at a second switching frequency that is lower than the first switching frequency, the system efficiency can be improved.

[0148] Further, it is preferable that, in the operation region of the rotary electric machine (80) defined by the torque and the rotational speed of the rotary electric machine (80), the inverter control device (10) stops the second inverter (52) and switches the first inverter (51) to convert electric power between the direct current and the N-phase alternating current in a first region (Rl), and switches the first inverter (51) and the second inverter (52) to convert electric power between the direct current and the 2N-phase alternating current in a second region (R2) that is located on the high torque side than the first region (Rl).

[0149] Generally, the region with the highest frequency within the operation region of the rotary electric machine (80) is generally a region on the relatively low torque side. As described above, one of the advantages of the rotary electric machine (80) provided with two coil sets (8) is that by including two inverters (50) corresponding to the two coil sets (8), the load of the inverters (50) is reduced and a larger alternating current flows so that the torque of the rotary electric machine (80) is increased. However, if it is on the relatively low torque side, the rotary electric machine (80) can output the required torque by the alternating current corresponding to one inverter (50). In the case where the second inverter (52) is stopped and the first inverter (51) is switch-controlled, since no current is supplied from the second inverter (52) to the second coil set (82), the iron loss due to the mutual inductance between the first coil set (81) and the second coil set (82) is also suppressed. According to the present structure, within the operation region of the rotary electric machine (80), in the region on the relatively low torque side, i.e., the first region (Rl), the inverter control device (10) stops the second inverter (52) and switch-controls the first inverter (51), so that the electric power is converted between the direct current and the alternating current of the N phase. That is, within the operation region of the rotary electric machine (80), since the iron loss in the first region (Rl) where the frequency is the highest is reduced, the system efficiency can be improved. In the second region (R2) on the relatively high torque side, since the inverter control device (10) switch-controls the first inverter (51) and the second inverter (52), so that the electric power is converted between the direct current and the alternating current of the 2N phase, the rotary electric machine (80) can output the required torque. In this case, the iron loss due to the mutual inductance occurs. However, since the operating frequency of the rotary electric machine (80) in the second region (R2) is lower than that in the first region (Rl), the effect of reducing the system efficiency is smaller than that in the first region (Rl).

[0150] Here, the inverter control device (10) preferably controls the first inverter (51) and the second inverter (52) in such a manner that currents having a phase difference of (π / 2N) flow through the first coil set (81) and the second coil set (82).

[0151] According to this structure, the inverter control device (10) individually switch-controls the first inverter (51) and the second inverter (52), so that the electric power can be appropriately converted between the direct current and the alternating current of the 2N phase.

[0152] Further, the first region (Rl) and the second region (R2) are preferably set based on the torque and the rotational speed of the rotary electric machine (80), or based on the voltage on the direct current side of the first inverter (51) and the second inverter (52) and the counter electromotive force of the rotary electric machine (80).

[0153] The operation region of the rotary electric machine 80 can be defined by the relationship between torque and rotational speed, the relationship between the voltage on the DC side of the inverter 50 and the back electromotive force, and the like. Also, in such an operation region, an operation region in which the frequency of use is relatively high and an operation region in which the frequency of use is relatively low can be determined. Therefore, when the first region Rl and the second region R2 are set as described above, it is possible to appropriately select between a control mode in which both the first inverter 51 and the second inverter 52 are used to convert electric power and a control mode in which the second inverter 52 is stopped and only the first inverter 51 is used to convert electric power.

[0154] In addition, in a case where the operation region of the rotary electric machine 80 shifts from the first region Rl to the second region R2, the inverter control device 10 preferably switch-controls the first inverter 51 and the second inverter 52 in such a manner that the current flowing through the first coil group 81 is reduced and a current corresponding to the reduced current flows through the second coil group 82, while maintaining the output torque of the rotary electric machine 80.

[0155] In a case where the rotary electric machine 80 is controlled with energization in both coil groups 8 and a case where the rotary electric machine 80 is controlled with energization in only one coil group 8, the most suitable operation condition is of course different. Therefore, when switching the control mode from a state with energization in only one coil group 8 to a state with energization in both coil groups 8, it is necessary to change the operation condition of each inverter 50 even if the output torque is the same, and if the control mode is switched abruptly, there is a possibility that torque fluctuation will occur. According to the present structure, by controlling in such a manner that the difference in current flowing through both coil groups 8 is reduced, it is possible to smoothly switch the control mode.

[0156] In addition, the inverter control device 10 preferably switch-controls the first inverter 51 and the second inverter 52 in such a manner that currents having the same effective value flow through the first coil group 81 and the second coil group 82 in the second region R2.

[0157] According to this structure, since a stable 2N-phase AC can be obtained, it is possible to appropriately drive the rotary electric machine 80.

[0158] In addition, the inverter control device 10 is based on the current command for the first coil group 81, i.e., the first current command I ＊ , which is set by the target torque T ＊ d1 , I ＊ q1) and the current (I d1 , I q1 ) flowing through the second coil group (82) to switch control the second inverter (52), thereby current feedback controlling the rotating electric machine (80), the feedback gain in the first region (R1) is preferably set to a value higher than the feedback gain in the second region (R2). ＊ , I ＊ d2 , I ＊ q2 ) and the current (I d2 , I q2 ) flowing through the second coil group (82) to switch control the second inverter (52), thereby current feedback controlling the rotating electric machine (80), the feedback gain in the first region (R1) is preferably set to a value higher than the feedback gain in the second region (R2).

[0159] In the case where energization is performed in both coil groups (8) via two inverters (50), interference is easily generated due to the influence of mutual inductance between the two coil groups (8), and as the feedback gain becomes higher, control converges more difficultly. On the other hand, in the case where energization is performed in only one coil group (8) via one inverter (50), interference due to the influence of mutual inductance is less, and the feedback gain can be easily increased compared to the case where energization is performed in both coil groups (8). Also, as the feedback gain becomes higher, the convergence time becomes shorter. Therefore, in feedback control in the first region (R1) of high frequency within the operating region of the rotating electric machine (80), when using a feedback gain of a value higher than the feedback gain in feedback control in the second region (R2), it is possible to improve system efficiency.

[0160] Explanation of reference numerals

[0161] 5: Switching device

[0162] 10: Inverter control device

[0163] 41: DC power supply

[0164] 51: First inverter

[0165] 52: Second inverter

[0166] 80: Rotating electric machine

[0167] 81: First coil group

[0168] 82: Second coil group

[0169] 100: Rotating electric machine control system

[0170] I ＊ d1 , I＊ q1 : first current command

[0171] I ＊ d2 , I ＊ q2 : second current command

[0172] I d1 , I q1 : current flowing through the first coil group

[0173] I d2 , I q2 : current flowing through the second coil group

[0174] R1: first region

[0175] R2: second region

[0176] T ＊ : target torque

Claims

1. A rotating electric machine control system for controlling an alternating-current rotating electric machine in which N-phase first coil sets and N-phase second coil sets are arranged in the same stator core, wherein N is a natural number, The rotating electric machine control system includes: a first inverter connected to a direct-current power supply and the first coil group, which converts electric power between direct current and N-phase alternating current; a second inverter connected to the direct-current power supply and the second coil group, which converts electric power between direct current and N-phase alternating current; and an inverter control device that generates switching control signals for individually controlling the first inverter and the second inverter, and controls the first inverter and the second inverter in such a manner that currents of different phases flow through the first coil group and the second coil group, respectively, The inverter control device is a device that stops the second inverter and switching-controls the first inverter to convert electric power between direct current and N-phase alternating current, or a device that switching-controls both the first inverter and the second inverter to convert electric power between direct current and 2N-phase alternating current, Compared with switching devices constituting the second inverter, switching devices constituting the first inverter have a shorter transition time between an off state and an on state, and a smaller switching loss.

2. The rotating electric machine control system according to claim 1, wherein The inverter control device switching-controls the first inverter at a first switching frequency, and switching-controls the second inverter at a second switching frequency lower than the first switching frequency.

3. The rotating electric machine control system according to claim 2, wherein In a first region in an operation region of the rotating electric machine defined by torque and rotational speed of the rotating electric machine, the inverter control device stops the second inverter and switching-controls the first inverter to convert electric power between direct current and N-phase alternating current, In a second region in the operation region of the rotating electric machine, which is located on a high-torque side compared with the first region, the inverter control device switching-controls the first inverter and the second inverter to convert electric power between direct current and 2N-phase alternating current.

4. The rotating electric machine control system according to claim 3, wherein The inverter control device controls the first inverter and the second inverter in such a manner that currents of phases differing by (π / 2N) flow through the first coil group and the second coil group.

5. The rotating electric machine control system according to claim 4, wherein The first region and the second region are set based on torque and rotational speed of the rotating electric machine, or based on voltages of direct-current sides of the first inverter and the second inverter and a counter electromotive force of the rotating electric machine.

6. The rotating electric machine control system according to claim 5, wherein In a case where the operation region of the rotating electric machine shifts from the first region to the second region, the inverter control device switching-controls the first inverter and the second inverter in such a manner that a current flowing through the first coil group is reduced and a current corresponding to the reduced current flows through the second coil group, in a state where an output torque of the rotating electric machine is maintained.

7. The rotating electric machine control system according to claim 6, wherein In the second region, the inverter control device switch-controls the first inverter and the second inverter in such a manner that the same effective value of current flows through the first coil group and the second coil group.

8. The rotating electric machine control system according to any one of claims 3 to 7, wherein the inverter control device is a device that switch-controls the first inverter based on a deviation between a current command, which is a first current command, of the first coil group set in accordance with a target torque of the rotating electric machine and a current flowing through the first coil group, and switch-controls the second inverter based on a deviation between a current command, which is a second current command, of the second coil group set in accordance with the target torque of the rotating electric machine and a current flowing through the second coil group, thereby performing current feedback control of the rotating electric machine, the feedback gain in the first region is set to a value higher than the feedback gain in the second region.

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