Control device for rotary electric machine, control program for rotary electric machine, and rotary electric machine system

Abstract

In a rotary electric machine (40), a high-frequency voltage is applied to a stator winding (52), whereby a voltage is induced in a field winding (70) and a field current flows. A control device (30) comprises: a switch control unit that performs switching control on an inverter (20) to apply, to the stator winding, a composite voltage of a high-frequency voltage and a fundamental wave voltage; an excitation reduction unit that performs excitation reduction control for reducing, lower than the present level, an excitation voltage component that causes a field current to flow to the field winding, among voltage components included in the composite voltage; a field weakening unit that performs field weakening control for adjusting the phase of a fundamental wave current flowing through the stator winding by means of the fundamental wave voltage so as to generate a magnetic flux in a direction reverse from that of a magnetic flux generated by the field winding; and a control change unit that performs change between execution and non-execution of the excitation reduction control and the field weakening control in accordance with an operation region of the rotary electric machine such that an output voltage of the inverter is suppressed.

Description

Rotating electric machine control device, rotating electric machine control program, and rotating electric machine system CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-001148 filed on January 9, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a control device for a rotating electric machine.

[0003] For example, a rotating electric machine system is known that includes a first power converter that supplies current to the stator winding of a synchronous motor and a second power converter that supplies field current to the field winding of a rotor (see Patent Document 1). In the rotating electric machine system described in Patent Document 1, when the output voltage of the first power converter exceeds a voltage limit value under high load, the magnetic flux command value of the field winding is reduced. This reduces the field current command value, reduces the magnetic flux of the field winding, and keeps the output voltage of the first power converter at the voltage limit value.

[0004] Japanese Patent Application Publication No. 5-30774

[0005] There is a self-excited field winding type rotating electric machine in which a high-frequency excitation voltage is applied to a stator winding to induce a voltage in the field winding, causing a field current to flow. In a self-excited field winding type rotating electric machine, the magnetic flux of the field winding can be reduced by reducing the excitation voltage component of the voltage applied to the stator winding (hereinafter referred to as "excitation reduction control"). The magnetic flux of the field winding can also be substantially reduced by passing a negative d-axis current through the stator winding to generate a magnetic flux in the opposite direction to the magnetic flux generated by the field winding (hereinafter referred to as "field weakening control").

[0006] Here, the present inventors have noticed that when a rotating electric machine outputs the same torque under excitation reduction control and field weakening control, the relationship between the output voltage of the power converter (inverter) under excitation reduction control and the output voltage of the power converter under field weakening control changes depending on the operating range of the rotating electric machine.

[0007] The present disclosure has been made to solve the above-mentioned problems, and its main purpose is to suppress the output voltage of an inverter by selectively using excitation reduction control and field weakening control in a control device for a rotating electric machine that is capable of performing excitation reduction control and field weakening control.

[0008] A first means for solving the above problem is a control device for a rotating electric machine applied to a rotating electric machine system including: a rotating electric machine having a stator including a stator winding and a rotor including a field winding; and an inverter electrically connected to the stator winding, wherein the rotating electric machine is configured so that a high frequency voltage is applied to the stator winding to induce a voltage in the field winding and cause a field current to flow, the control device comprising: a switch control unit that performs switching control of the inverter so as to apply to the stator winding a composite voltage of the high frequency voltage and a fundamental voltage having a frequency different from the high frequency voltage; an excitation reducing unit that performs excitation reducing control to reduce, from the current level, an excitation voltage component that is a component that causes the field current to flow in the field winding among voltage components included in the composite voltage; and a field weakening unit that performs field weakening control to adjust the phase of the fundamental current flowing in the stator winding by the fundamental voltage so as to generate a magnetic flux in the opposite direction to the magnetic flux generated by the field winding. and a control change unit that changes whether or not the excitation reduction control by the excitation reduction unit and the field weakening control by the field weakening unit are performed depending on the operating region of the rotating electric machine so that the output voltage of the inverter is suppressed.

[0009] According to the above configuration, the rotating electric machine is configured so that a high-frequency voltage is applied to the stator winding to induce a voltage in the field winding, causing a field current to flow. Furthermore, the switch control unit controls the switching of the inverter so that a high-frequency voltage having a frequency higher than the fundamental voltage is applied to the stator winding in addition to a fundamental voltage intended to generate torque in the rotating electric machine. This eliminates the need for a power converter other than the inverter for applying a field current to the field winding, thereby simplifying the rotating electric machine system.

[0010] The excitation reduction unit performs excitation reduction control to reduce, from the current level, an excitation voltage component, which is a component that causes the field current to flow through the field winding, among the voltage components included in the composite voltage. Therefore, when it is necessary to suppress the inverter output voltage, the excitation reduction unit performs excitation reduction control to suppress the inverter output voltage. Furthermore, the field weakening unit performs field weakening control to adjust the phase of the fundamental wave current flowing through the stator winding so as to generate a magnetic flux in the opposite direction to the magnetic flux generated by the field winding. Therefore, when it is necessary to suppress the inverter output voltage, the field weakening unit performs field weakening control to suppress the inverter output voltage.

[0011] The present inventors have noted that when a rotating electric machine outputs the same torque under excitation reduction control and field weakening control, which of the inverter output voltage during excitation reduction control and field weakening control is higher varies depending on the operating range of the rotating electric machine. For example, in a high load range of the rotating electric machine, when a rotating electric machine outputs the same torque under excitation reduction control and field weakening control, the inverter output voltage during field weakening control is lower than the inverter output voltage during excitation reduction control. Then, depending on the operating range of the rotating electric machine, the control change unit changes whether or not to perform the excitation reduction control by the excitation reduction unit and the field weakening control by the field weakening unit so as to suppress the inverter output voltage. Therefore, excitation reduction control and field weakening control can be selectively used depending on the operating range of the rotating electric machine, thereby suppressing the inverter output voltage.

[0012] The second means is a control program for a rotating electric machine applied to a rotating electric machine system including: a rotating electric machine having a stator including a stator winding and a rotor including a field winding; and an inverter electrically connected to the stator winding, wherein the rotating electric machine is configured so that a voltage is induced in the field winding by applying a high-frequency voltage to the stator winding, causing a field current to flow; a process of performing switching control of the inverter so as to apply to the stator winding a composite voltage of the high-frequency voltage and a fundamental voltage having a frequency different from the high-frequency voltage; a process of performing excitation reduction control to reduce, from the current level, an excitation voltage component which is a component that causes the field current to flow in the field winding among voltage components included in the composite voltage; a process of performing field weakening control to adjust the phase of the fundamental current flowing in the stator winding by the fundamental voltage so as to generate a magnetic flux in the opposite direction to the magnetic flux generated by the field winding; and a process of changing whether or not to perform the excitation reduction control and the field weakening control according to an operating region of the rotating electric machine so as to suppress the output voltage of the inverter. is executed by a computer.

[0013] According to the above configuration, by causing a computer to execute a control program for a rotating electrical machine, it is possible to achieve the same effects as those of the first means.

[0014] The third means is a rotating electric machine system comprising: a rotating electric machine having a stator including a stator winding and a rotor including a field winding; an inverter electrically connected to the stator winding; and a control device for the rotating electric machine, wherein the rotating electric machine is configured such that a high frequency voltage is applied to the stator winding to induce a voltage in the field winding and cause a field current to flow, and the control device comprises: a switch control unit that performs switching control of the inverter so as to apply to the stator winding a composite voltage of the high frequency voltage and a fundamental voltage having a frequency different from the high frequency voltage; an excitation reduction unit that performs excitation reduction control to reduce, from the current level, an excitation voltage component that is a component that causes the field current to flow in the field winding among voltage components included in the composite voltage; and a field weakening unit that performs field weakening control to adjust the phase of the fundamental current flowing in the stator winding by the fundamental voltage so as to generate a magnetic flux in the opposite direction to the magnetic flux generated by the field winding. and a control change unit that changes whether or not the excitation reduction control by the excitation reduction unit and the field weakening control by the field weakening unit are performed depending on the operating region of the rotating electric machine so that the output voltage of the inverter is suppressed.

[0015] According to the above configuration, in the control system for a rotating electrical machine, the same effects as those of the first means can be achieved.

[0016] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is an overall configuration diagram of a rotating electrical machine system, Fig. 2 is a diagram showing an inverter and its peripheral configuration, Fig. 3 is a cross-sectional view of a rotor and a stator, Fig. 4 is a diagram showing an electric circuit provided in the rotor, Fig. 5 is a block diagram of torque control processing by a control device, Fig. 6 is a diagram showing fundamental wave currents and high frequency currents (harmonic currents), Fig. 7 is a diagram showing an operating region of a rotating electrical machine, Fig. 8 is a block diagram showing calculation processing of a d-axis high frequency command current by a control device, Fig. 9 is a flowchart showing the procedure for calculation processing of the d-axis high frequency command current, and Fig. 10 is a diagram showing voltage during excitation reduction control and field weakening control. FIG. 11 is a block diagram showing the calculation process of the d-axis high-frequency command current according to the second embodiment, FIG. 12 is a block diagram of the torque control process according to the third embodiment, FIG. 13 is a block diagram showing the calculation process of the inductance reducing current, FIG. 14 is a flowchart showing the procedure of the calculation process of the inductance reducing current, FIG. 15 is a diagram showing an example of changing the voltage difference between the voltage during excitation reducing control and the voltage during field weakening control, FIG. 16 is a diagram showing an example of changing the phase of the fundamental wave current and the high-frequency current, and FIG. 17 is a diagram showing the relationship between the phase of the output voltage vector and the excitation voltage.

[0017] Several embodiments will be described with reference to the drawings. In several embodiments, functionally and / or structurally corresponding and / or associated parts may be designated by the same reference numerals or reference numerals with different hundreds digits. For corresponding and / or associated parts, reference may be made to the descriptions of other embodiments.

[0018] A first embodiment of a rotating electric machine system and a control device for a rotating electric machine according to the present disclosure will now be described with reference to the drawings. The rotating electric machine system is mounted on, for example, a vehicle. The rotating electric machine is a power source for running the vehicle.

[0019] 1 , a rotating electric machine system 90 includes a DC power supply 10, an inverter 20, a control device 30, and a rotating electric machine 40. The rotating electric machine 40 is a self-excited field winding type synchronous machine. For example, the rotating electric machine 40, the inverter 20, and the control device 30 may be included to form an electromechanical integrated drive device, or the rotating electric machine 40, the inverter 20, and the control device 30 may each be formed by a separate component.

[0020] The rotating electric machine 40 includes a housing 41, and a stator 50 and a rotor 60 housed in the housing 41. The rotating electric machine 40 of this embodiment is an inner rotor type rotating electric machine in which the rotor 60 is disposed radially inside the stator 50.

[0021] The stator 50 includes a stator core 51 and a stator winding 52. The stator winding 52 is made of, for example, copper wire, and includes U-, V-, and W-phase windings 52U, 52V, and 52W that are arranged with an electrical angle offset of 120° from one another (see FIG. 3 ).

[0022] The rotor 60 includes a rotor core 61 and a field winding 70. The field winding 70 is made of, for example, aluminum wire, copper wire, or CNT (carbon nanotube). A rotating shaft 32 is inserted through the center hole of the rotor core 61. The rotating shaft 32 is rotatably supported by the housing 41 via a bearing 42.

[0023] As shown in FIG. 2 , the inverter 20 (power converter) includes a series connection of U-, V-, and W-phase upper-arm switches SUp, SVp, and SWp and U-, V-, and W-phase lower-arm switches SUn, SVn, and SWn. First ends (one ends) of U-, V-, and W-phase windings 52U, 52V, and 52W are connected to the connection points between the U-, V-, and W-phase upper-arm switches SUp, SVp, and SWp and the U-, V-, and W-phase lower-arm switches SUn, SVn, and SWn. Second ends (the other ends) of the U-, V-, and W-phase windings 52U, 52V, and 52W are connected to the neutral point. That is, in this embodiment, the U-, V-, and W-phase windings 52U, 52V, and 52W are star-connected. Note that, in this embodiment, each of the switches SUp to SWn is an IGBT. A freewheel diode is connected in antiparallel to each of the switches SUp to SWn.

[0024] The collectors of the U-, V-, and W-phase upper-arm switches SUp, SVp, and SWp are connected to a positive terminal of a DC power supply 10. The emitters of the U-, V-, and W-phase lower-arm switches SUn, SVn, and SWn are connected to a negative terminal of the DC power supply 10. A smoothing capacitor 11 is connected in parallel to the DC power supply 10.

[0025] Next, the stator 50 and the rotor 60 will be described with reference to FIG.

[0026] The stator 50 and the rotor 60 are both arranged coaxially with the rotating shaft 32 (specifically, with the central axis of rotation O as a common axis). In the following description, the direction in which the rotating shaft 32 extends is referred to as the axial direction, the direction extending radially from the center of the rotating shaft 32 is referred to as the radial direction, and the direction extending circumferentially around the rotating shaft 32 is referred to as the circumferential direction.

[0027] The stator 50 is made of laminated steel plates made of a soft magnetic material and has an annular back yoke 51a and a plurality of teeth 51b protruding radially inward from the back yoke 51a. A plurality of slots 54 are formed between adjacent teeth 51b and aligned in the circumferential direction. The stator winding 52 is formed by accommodating the phase windings of each phase in each slot 54 in a predetermined order.

[0028] The rotor 60 is made of a soft magnetic material, such as laminated steel plates. The rotor 60 has a cylindrical rotor core 61 and a plurality of main poles 62 that protrude radially outward from the rotor core 61. In this embodiment, eight main poles 62 are provided at equal intervals in the circumferential direction.

[0029] The field winding 70 includes a first winding portion 71a and a second winding portion 71b. In each main pole portion 62, the first winding portion 71a is wound radially outward, and the second winding portion 71b is wound radially inward relative to the first winding portion 71a. In each main pole portion 62, the winding directions of the first winding portion 71a and the second winding portion 71b are the same. Furthermore, of circumferentially adjacent main pole portions 62, the winding directions of the winding portions 71a, 71b wound around one are opposite to the winding directions of the winding portions 71a, 71b wound around the other. Therefore, the magnetization directions of circumferentially adjacent main pole portions 62 are opposite to each other.

[0030] Fig. 4 shows an electrical circuit on the rotor 60 side, which includes winding portions 71a and 71b wound around a common main pole portion 62. The first winding portion 71a shown in Fig. 4 is a series connection of the first winding portions 71a wound around each main pole portion 62, and the second winding portion 71b shown in Fig. 4 is a series connection of the second winding portions 71b wound around each main pole portion 62.

[0031] The rotor 60 is provided with a diode 80 as a rectifying element and a capacitor 81. The diode 80 is electrically connected in parallel to the series connection of the first winding portion 71a and the second winding portion 71b. More specifically, a first end of the first winding portion 71a is connected to the cathode of the diode 80, and a first end of the second winding portion 71b is connected to the second end of the first winding portion 71a. An anode of the diode 80 is connected to the second end of the second winding portion 71b. A capacitor 81 is electrically connected in parallel to the second winding portion 71b. In FIG. 4 , L1 represents the inductance of the first winding portion 71a, L2 represents the inductance of the second winding portion 71b, and C represents the capacitance of the capacitor 81.

[0032] In this embodiment, a series resonant circuit is configured including the first winding portion 71a and the capacitor 81, and a parallel resonant circuit is configured including the second winding portion 71b and the capacitor 81. In Fig. 4, f1 indicates a first resonant frequency which is the resonant frequency of the series resonant circuit, and f2 indicates a second resonant frequency which is the resonant frequency of the parallel resonant circuit.

[0033] Alternatively, the anode of the diode 80 may be connected to the first end of the first winding portion 71a, and the cathode of the diode 80 may be connected to the second end of the second winding portion 71b.

[0034] Returning to the explanation of FIG. 2 , the rotating electric machine system 90 includes a current sensor 21, an angle sensor 22, and a voltage sensor 23. The current sensor 21 detects at least two phases of the phase currents flowing through the rotating electric machine 40. The angle sensor 22 detects the rotation angle (electrical angle) of the rotor 60. In this embodiment, the voltage sensor 23 includes a sensor that detects the voltage of the DC power supply 10 and a sensor that detects the output voltage (phase voltage) of each phase of the inverter 20. The detected values ​​of the sensors 21 to 23 are input to the control device 30.

[0035] The control device 30 (a control device for a rotating electric machine) is an electronic control unit (EC) primarily composed of a microcomputer 31. The microcomputer 31 includes a central processing unit (CPU). The functions provided by the microcomputer 31 can be provided by software stored in a physical memory device and a computer executing the software, software alone, hardware alone, or a combination thereof. For example, if the microcomputer 31 is provided by a hardware electronic circuit, the function can be provided by a digital circuit including multiple logic circuits or an analog circuit. For example, the microcomputer 31 executes a program stored in a non-transitory tangible storage medium (NSS) that serves as its own storage unit. The program (control program) includes, for example, the processing programs shown in Figures 5, 7, and 8 (described below). A method corresponding to the program is executed by executing a set of instructions constituting the program. The storage unit is, for example, a non-volatile memory. The program stored in the storage unit can be updated via a communication network such as the Internet, for example, via OTA (Over the Air).

[0036] The control device 30 generates drive signals that turn on and off each of the switches SUp to SWn that constitute the inverter 20. Specifically, the control device 30 generates drive signals that turn on and off each of the arm switches SUp to SWn and supplies the generated drive signals to the gates of each of the arm switches SUp to SWn in order to convert the DC power output from the DC power supply 10 into AC power and supply the AC power to the U-, V-, and W-phase windings 52U, 52V, and 52W. As a result, the upper arm switches and the lower arm switches in each phase are alternately turned on with dead times therebetween.

[0037] The control device 30 turns on and off the switches SUp to SWn so as to pass a combined current of a fundamental current and a harmonic current (specifically, a harmonic excitation current) having a frequency higher than that of the fundamental current through the phase windings 52U, 52V, and 52W. The fundamental current is a current that mainly serves to generate torque in the rotary electric machine 40. The harmonic current is a current that mainly serves to excite the field winding 70 and induce a field current in the field winding 70. The phase currents flowing through the phase windings 52U, 52V, and 52W are shifted by 120 electrical degrees.

[0038] The torque control of the rotary electric machine 40 executed by the control device 30 will be described with reference to FIG.

[0039] The two-phase conversion unit 100 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 detection value of the current sensor 21 and the electrical angle θe detected by the angle sensor 22.

[0040] The command current calculation unit 101 calculates a d-axis base command current Idbref and a q-axis command current Iqref based on the command torque Tref. The d-axis base command current Idbref and the q-axis command current Iqref are command values ​​of DC components corresponding to the fundamental wave current. The command current calculation unit 101 may calculate the d-axis base command current Idbref and the q-axis command current Iqref based on, for example, map information in which the command torque Tref, the d-axis base command current Idbref, and the q-axis command current Iqref are correlated, and the input command torque Tref. The field weakening control command from the field weakening unit 201 to the command current calculation unit 101 will be described later.

[0041] The excitation current calculation unit 102 calculates the d-axis high-frequency command current Idhref. The d-axis high-frequency command current Idhref is a command value of an AC component corresponding to a harmonic current that excites the field winding 70, and in this embodiment is expressed by the following equation (eq1): In the following equation (eq1), Idamp is the amplitude of the d-axis high-frequency command current Idhref, and fh is the fluctuating frequency of the d-axis high-frequency command current Idhref. Note that the excitation current calculation unit 102 may calculate the amplitude Idamp of the d-axis high-frequency command current Idhref so that the amplitude of the harmonic current is, for example, 3% or more of the amplitude of the fundamental current.

[0042] The superimposing unit 103 calculates the d-axis command current Idref by adding the d-axis high-frequency command current Idhref to the d-axis basic command current Idbref.

[0043] The d-axis deviation calculation unit 104 calculates the d-axis current deviation ΔId by subtracting the d-axis current Idr from the d-axis command current Idref. The q-axis deviation calculation unit 105 calculates the q-axis current deviation ΔIq by subtracting the q-axis current Iqr from the q-axis command current Iqref.

[0044] The d-axis current control unit 106 calculates a d-axis voltage command value Vdref 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 Idref. The q-axis current control unit 107 calculates a q-axis voltage command value Vqref 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 Iqref. In this embodiment, the feedback control of each of the current control units 106 and 107 is proportional-integral control.

[0045] A three-phase converter 108 converts the d- and q-axis voltage command values ​​Vdref and Vqref in the two-phase rotating coordinate system into U-, V-, and W-phase voltage command values ​​VUref, VVref, and VWref in the three-phase fixed coordinate system based on the d- and q-axis voltage command values ​​Vdref and Vqref and the electrical angle θe. The U-, V-, and W-phase voltage command values ​​VUref, VVref, and VWref have waveforms with phases shifted by 120 degrees in electrical angle. The frequencies of harmonic components included in the U-, V-, and W-phase voltage command values ​​VUref, VVref, and VWref are set to frequencies near the first resonance frequency f1. The U-, V-, and W-phase voltage command values ​​VUref, VVref, and VWref are composite voltages of a fundamental voltage corresponding to the fundamental current and a harmonic voltage corresponding to the harmonic current.

[0046] Based on the U-, V-, and W-phase voltage command values ​​VUref, VVref, and VWref, the signal generating unit 109 generates drive signals GUH to GWL for the upper and lower arm switches SUp to SWn in the U-, V-, and W-phases to pass the above-mentioned composite current through the stator winding 52. The generated drive signals GUH to GWL are input to the gates of the respective switches, thereby performing switching control of the inverter 20. In this embodiment, the signal generating unit 109 corresponds to a "switch control unit."

[0047] As a result of the switching control of the inverter 20, a composite current consisting of a fundamental current (see FIG. 6( a)) and a harmonic current (see the solid line in FIG. 6( b)) superimposed on it flows through each of the phase windings 52U, 52V, and 52W. The harmonic currents flowing through the stator winding 52 cause a field current to flow through the field winding 70. FIG. 6( a) shows the progression of the fundamental current over one electrical angle period. The dashed-dotted line in FIG. 6( b) shows the envelope of the harmonic current. The envelope of the harmonic current has the same period as the fundamental current. The phase of the harmonic current relative to the fundamental current is the phase that allows the harmonic current to flow most efficiently through the field winding 70 (the phase in which the field current is maximized when compared with high-frequency currents of the same magnitude). The values ​​on the vertical axis in FIG. 6 indicate the relative relationship between the wave magnitudes shown in FIGS. 6( a) and 6(b).

[0048] 7, the operating region of the rotating electric machine 40 is represented by the command torque Tref and the electrical angular velocity ωe of the rotor 60 (or the rotational speed of the rotor 60). The operating region is divided into a sinusoidal PWM control region, an overmodulation control region, and a square wave control region. The overmodulation control region is adjacent to the high-speed side of the sinusoidal PWM control region.

[0049] When the control device 30 determines that the electrical angular velocity ωe calculated based on the electrical angle θe is less than the first speed threshold ωth1, it performs sinusoidal PWM control. The sinusoidal PWM control is switching control of the upper and lower arm switches to make each phase voltage applied to the stator winding 52 have a PWM voltage waveform when the peak value of each phase voltage applied to the stator winding 52 is equal to or less than the terminal voltage of the DC power supply 10. The first speed threshold ωth1 decreases as the command torque Tref increases.

[0050] When the control device 30 determines that the electrical angular velocity ωe is equal to or greater than the first speed threshold ωth1 and less than the second speed threshold ωth2, it performs overmodulation control. The overmodulation control is switching control of the upper and lower arm switches to change each phase voltage applied to the stator windings 52 into a PWM voltage waveform with a higher modulation factor than the PWM voltage waveform obtained by sinusoidal PWM control when the peak value of the phase voltage applied to the stator windings 52 exceeds the terminal voltage of the DC power supply 10. The second speed threshold ωth2 decreases as the command torque Tref increases.

[0051] In addition, the control device 30 may determine whether the current operating point is in the overmodulation control region or the square wave control region based on the magnitude of the output voltage vector of the inverter 20, rather than using the first speed threshold ωth1 and the second speed threshold ωth2 as described above.

[0052] When the control device 30 determines that the operating point is in the overmodulation control region or the square wave control region (when the rotational speed of the rotor 60 of the rotating electric machine 40 is higher than a predetermined rotational speed), it performs excitation reduction control to reduce the excitation voltage component, which is a component that causes a field current to flow through the field winding 70. The excitation reduction control is control that reduces the magnetic flux generated by the field winding 70 of the rotor 60 to be less than the current magnetic flux. The excitation reduction control will be described below using the block diagram of the excitation current calculation unit 102 shown in FIG.

[0053] The excitation current calculation unit 102 functions as an "excitation reduction unit" and includes a voltage amplitude calculation unit 110, a voltage deviation calculation unit 111, and a feedback control unit 112. The voltage amplitude calculation unit 110 calculates a voltage amplitude Vom, which is the magnitude of the output voltage vector of the inverter 20 in a two-phase rotating coordinate system, based on the d-axis voltage command value Vdref calculated by the d-axis current control unit 106 and the q-axis voltage command value Vqref calculated by the q-axis current control unit 107. More specifically, the voltage amplitude calculation unit 110 calculates the voltage amplitude Vom based on the following equation (eq2):

[0054] The voltage deviation calculation unit 111 calculates the voltage deviation ΔV by subtracting the limit value Vlim from the calculated voltage amplitude Vom. The limit value Vlim (voltage limit value) is a value that is set to prevent the induced voltage generated in the stator winding 52 from becoming equal to or higher than the terminal voltage of the DC power supply 10. For example, the voltage deviation calculation unit 111 may set the limit value Vlim higher as the terminal voltage of the DC power supply 10 detected by the voltage sensor 23 (hereinafter referred to as the power supply voltage Vdc) becomes higher.

[0055] The feedback control unit 112 calculates a deviation amount Xh, which is a manipulated variable for feedback-controlling the calculated voltage deviation ΔV to 0. In this embodiment, the feedback control used by the feedback control unit 112 is proportional-integral control.

[0056] The excitation current calculation unit 102 includes an excitation parameter calculation unit 113. The excitation parameter calculation unit 113 calculates the amplitude Idamp and fluctuation frequency fh of the d-axis high-frequency command current Idhref based on the calculated deviation amount Xh. The excitation parameter calculation unit 113 reduces the excitation voltage component of the field winding 70 among the voltage components included in the composite voltage by decreasing the amplitude Idamp and decreasing the fluctuation frequency fh. This reduces the magnetic flux generated in the rotor 60, thereby performing excitation reduction control. Below, we will explain why the excitation voltage component can be reduced by decreasing the amplitude Idamp and decreasing the fluctuation frequency fh.

[0057] The voltage equations of the motor in a two-phase rotating coordinate system are shown in the following equations (eq3) and (eq4): In the following equations (eq3) and (eq4), R is the resistance value of the stator winding 52, Ld and Lq are the d-axis and q-axis inductances, and φ is the effective value of the interlinkage magnetic flux of the stator winding 52.

[0058]

[0059] Substituting "Id=Idbref+Idhref" into the above equations (eq3) and (eq4), the following equations (eq5) and (eq6) are derived.

[0060]

[0061] In the above equations (eq5) and (eq6), the terms enclosed in curly brackets on the right-hand sides are excitation voltage components. Therefore, the excitation voltage components increase as the amplitude Idamp of the d-axis high-frequency command current Idhref increases, and as the fluctuation frequency fh increases. The larger the excitation voltage component, the larger the field current flowing through the field winding 70, and therefore the larger the magnetic flux generated by the field winding 70.

[0062] First, the method of calculating the fluctuation frequency fh will be described. When the deviation amount Xh is equal to or less than 0, the excitation parameter calculation unit 113 sets the fluctuation frequency fh to the first frequency fa. When the deviation amount Xh is greater than 0 and less than the first threshold value Xth1, the excitation parameter calculation unit 113 sets the fluctuation frequency fh to a frequency that is less than the first frequency fa and higher than the second frequency fb (<fa), and that decreases as the deviation amount Xh increases. When the deviation amount Xh is equal to or greater than the first threshold value Xth1, the excitation parameter calculation unit 113 sets the fluctuation frequency fh to the second frequency fb. That is, when the deviation amount Xh increases, the excitation parameter calculation unit 113 reduces the fluctuation frequency fh of the d-axis high-frequency command current Idhref below the current fluctuation frequency fh.

[0063] Next, the method of calculating the amplitude Idamp will be described. When the deviation amount Xh is equal to or less than the first threshold value Xth1, the excitation parameter calculation unit 113 sets the amplitude Idamp to the first amplitude Ia. When the deviation amount Xh is greater than the first threshold value Xth1 and less than the second threshold value Xth2 (>Xth1), the excitation parameter calculation unit 113 sets the amplitude Idamp to an amplitude that is less than the first amplitude Ia and greater than the second amplitude Ib (<Ia), and that decreases as the deviation amount Xh increases. When the deviation amount Xh is equal to or greater than the second threshold value Xth2, the excitation parameter calculation unit 113 sets the amplitude Idamp to the second amplitude Ib. That is, when the deviation amount Xh increases, the excitation parameter calculation unit 113 reduces the amplitude Idamp of the d-axis high-frequency command current Idhref from the current amplitude Idamp.

[0064] Reducing the amplitude Idamp increases the amount of torque reduction of the rotary electric machine 40. For this reason, in this embodiment, the deviation amount Xh at which the fluctuation frequency fh starts to decrease is set to be smaller than the deviation amount Xh at which the amplitude Idamp starts to decrease. As a result, the magnetic flux of the rotor 60 is reduced by the process of reducing the fluctuation frequency fh prior to the process of reducing the amplitude Idamp. As a result, the field current can be reduced while suppressing torque reduction.

[0065] In particular, in this embodiment, the amplitude Idamp starts to decrease when the deviation Xh exceeds a first threshold Xth1, which is the deviation Xh at which the decrease in the fluctuation frequency fh is completed. In other words, the process of decreasing the amplitude Idamp starts when the deviation Xh does not become equal to or less than 0 even after the process of decreasing the fluctuation frequency fh. This makes it possible to reduce the field current while suitably suppressing a decrease in torque.

[0066] In this way, the d-axis high-frequency command current Idhref is adjusted in the excitation current calculation section 102, and the excitation voltage component is reduced (adjusted).

[0067] 9 shows a flowchart of the excitation reduction control process executed by the control device 30. This process is executed repeatedly at a predetermined control period, for example.

[0068] In step S10, the voltage amplitude calculation unit 110 calculates the voltage amplitude Vom based on the d-axis and q-axis voltage command values ​​Vdref and Vqref.

[0069] In step S11, the voltage deviation calculation unit 111 calculates the voltage deviation ΔV based on the calculated voltage amplitude Vom.

[0070] In step S12, the feedback control unit 112 calculates the deviation amount Xh based on the calculated voltage deviation ΔV.

[0071] In step S13, the excitation parameter calculation unit 113 calculates the fluctuation frequency fh and amplitude Idamp of the d-axis high-frequency command current Idhref based on the calculated deviation amount Xh.

[0072] In step S14, the d-axis high-frequency command current Idhref determined from the calculated fluctuation frequency fh and amplitude Idamp is calculated, and the calculated d-axis high-frequency command current Idhref is output to the superimposing unit 103. Thereafter, this series of processes is temporarily ended.

[0073] 5 , the control device 30 also includes a field-weakening unit 201. When the voltage amplitude Vom is greater than the limit value Vlim (or when the rotational speed of the rotor 60 is higher than a predetermined rotational speed), the field-weakening unit 201 executes field-weakening control by passing a negative d-axis current through the stator winding 52 so that the stator winding 52 generates a magnetic flux opposite in direction to the magnetic flux generated by the field winding 70. Specifically, the field-weakening unit 201 transmits a field-weakening control command to the command current calculation unit 101, causing the command current calculation unit 101 to calculate a d-axis basic command current Idbref so that a negative d-axis current flows through the stator winding 52. As a result, the phase of the fundamental wave current flowing through the stator winding 52 is adjusted by the fundamental wave voltage, and the stator winding 52 generates a magnetic flux opposite in direction to the magnetic flux generated by the field winding 70. The predetermined rotation speed is a rotation speed at which the voltage amplitude Vom becomes larger than the limit value Vlim, and can be obtained in advance based on an experiment or the like.

[0074] The control device 30 includes a control change unit 209. The control change unit 209 changes whether or not to execute the excitation reduction control by the excitation current calculation unit 102 and the field weakening control by the field weakening unit 201, depending on the operating region of the rotating electric machine 40, so as to suppress the output voltage of the inverter 20. In this embodiment, the control change unit 209 executes only one of the excitation reduction control by the excitation current calculation unit 102 and the field weakening control by the field weakening unit 201.

[0075] 10 is a diagram showing the voltage difference between the voltage during excitation reduction control and the voltage during field weakening control. The voltage difference is the voltage difference obtained by subtracting the output voltage (voltage amplitude Vom) of the inverter 20 during field weakening control from the output voltage (voltage amplitude Vom) of the inverter 20 during excitation reduction control when the rotating electric machine 40 outputs the same torque at the same rotational speed during excitation reduction control and field weakening control. The voltage difference between the output voltage during excitation reduction control and the output voltage during field weakening control is calculated using only the DC component (fundamental wave voltage) of the output voltage. Note that the magnitude of the voltage difference varies slightly depending on the rotational speed of the rotating electric machine 40, but the effect of the rotational speed is small.

[0076] In the rotating electric machine 40 of this embodiment, in the high torque region (high load region), the output voltage during field weakening control is lower than the output voltage during excitation reduction control, and the voltage difference is a positive value. That is, in the high torque region, when the rotating electric machine 40 outputs the same torque through excitation reduction control and field weakening control, performing field weakening control is advantageous because it can lower the output voltage. On the other hand, in the low torque region (low load region), when the rotating electric machine 40 outputs the same torque through excitation reduction control and field weakening control, if the output voltage (fundamental wave voltage) is greater than a predetermined value (threshold value), the output voltage during field weakening control is lower than the output voltage during excitation reduction control, and if the output voltage is less than the predetermined value, the output voltage during excitation reduction control is lower than the output voltage during field weakening control. Generally, in the low torque region, the output voltage is often lower than the predetermined value. Therefore, when the rotating electric machine 40 outputs the same torque through excitation reduction control and field weakening control, the output voltage during excitation reduction control is lower than the output voltage during field weakening control. Therefore, in the low torque region, when the rotating electric machine 40 outputs the same torque with excitation reduction control and field weakening control, it can be said that performing excitation reduction control is advantageous because it can lower the output voltage.

[0077] Therefore, when suppressing the output voltage of the inverter 20, the control modifying unit 209 does not cause the excitation current calculating unit 102 to execute excitation reduction control, but instead causes the field weakening unit 201 to execute field weakening control, in the high load region of the rotating electric machine 40. When not executing excitation reduction control, the excitation current calculating unit 102 keeps the amplitude Idamp, fluctuation frequency fh, and phase of the d-axis high-frequency command current Idhref constant. Specifically, as shown in FIG. 8 , when the deviation amount Xh is 0 or less, the control modifying unit 209 sets the fluctuation frequency fh of the d-axis high-frequency command current Idhref to a first frequency fa, the amplitude Idamp to a first amplitude Ia, and the phase to a reference phase. Furthermore, when suppressing the output voltage of the inverter 20, the control modifying unit 209 does not cause the field weakening unit 201 to execute field weakening control, but instead causes the excitation current calculating unit 102 to execute excitation reduction control, in the low load region of the rotating electric machine 40.

[0078] The present embodiment described above in detail has the following advantages.

[0079] The rotating electric machine 40 is configured so that a voltage is induced in the field winding 70 by applying a high-frequency voltage to the stator winding 52, causing a field current to flow. Furthermore, the signal generating unit 109 controls the switching of the inverter 20 so that, in addition to the fundamental voltage intended to generate torque in the rotating electric machine 40, a high-frequency voltage having a higher frequency than the fundamental voltage is passed through the stator winding 52. This eliminates the need for an inverter (power converter) other than the inverter 20 for passing a field current through the field winding 70, thereby simplifying the rotating electric machine system 90.

[0080] The excitation current calculation unit 102 performs excitation reduction control to reduce, from the current level, the excitation voltage component, which is a component that causes a field current to flow through the field winding 70, among the voltage components included in the composite voltage. Therefore, when it is necessary to suppress the output voltage of the inverter 20, the excitation current calculation unit 102 performs excitation reduction control, thereby suppressing the output voltage of the inverter 20. Furthermore, the field weakening unit 201 performs field weakening control to adjust the phase of the fundamental wave current flowing through the stator winding 52 so as to generate a magnetic flux that is opposite in direction to the magnetic flux generated by the field winding 70. Therefore, when it is necessary to suppress the output voltage of the inverter 20, the field weakening unit 201 performs field weakening control, thereby suppressing the output voltage of the inverter 20.

[0081] In the high torque region (high load region) of the rotating electric machine 40, when the rotating electric machine 40 outputs the same torque through the excitation reduction control and the field weakening control, the output voltage of the inverter 20 during the field weakening control is lower than the output voltage of the inverter 20 during the excitation reduction control. Then, depending on the operating region of the rotating electric machine 40, the control change unit 209 changes whether or not to execute the excitation reduction control by the excitation current calculation unit 102 and the field weakening control by the field weakening unit 201 so as to suppress the output voltage of the inverter 20. Therefore, it is possible to selectively use the excitation reduction control and the field weakening control depending on the operating region of the rotating electric machine 40, and it is possible to suppress the output voltage of the inverter 20.

[0082] The rotating electric machine 40 has a characteristic that, when the rotating electric machine 40 outputs the same torque through excitation reduction control and field weakening control in a high torque region, the output voltage of the inverter 20 during field weakening control is lower than the output voltage of the inverter 20 during excitation reduction control. Therefore, when suppressing the output voltage of the inverter 20, the control change unit 209 does not cause the excitation current calculation unit 102 to execute excitation reduction control in the high torque region of the rotating electric machine 40, but instead causes the field weakening unit 201 to execute field weakening control. Therefore, it is possible to execute field weakening control that can further lower the output voltage of the inverter 20 in the high torque region in accordance with the characteristics of the rotating electric machine 40, and it is possible to suppress the output voltage of the inverter 20.

[0083] It can be said that the rotating electric machine 40 has a characteristic that, when the rotating electric machine 40 outputs the same torque under excitation reduction control and field weakening control in a low torque region, the output voltage of the inverter 20 under excitation reduction control is lower than the output voltage of the inverter 20 under field weakening control. Therefore, when suppressing the output voltage of the inverter 20, the control change unit 209 does not execute field weakening control by the field weakening unit 201 in the low torque region of the rotating electric machine 40, but executes excitation reduction control by the excitation current calculation unit 102. Therefore, excitation reduction control can be executed in accordance with the characteristics of the rotating electric machine 40, which can further lower the output voltage of the inverter 20 in the low torque region, and the output voltage of the inverter 20 can be suppressed.

[0084] The excitation voltage component of the composite voltage increases as the amplitude Idamp of the d-axis high-frequency current flowing through the stator winding 52 increases. Therefore, in the excitation reduction control, the excitation current calculation unit 102 reduces the excitation voltage component by decreasing the current amplitude Idamp of the d-axis high-frequency current flowing through the stator winding 52. With this configuration, the excitation voltage component can be reduced by utilizing the relationship between the amplitude Idamp of the d-axis high-frequency current flowing through the stator winding 52 and the excitation voltage component.

[0085] The excitation voltage component of the composite voltage increases as the fluctuation frequency fh of the d-axis high-frequency current flowing through the stator winding 52 increases. Therefore, in the excitation reduction control, the excitation current calculation unit 102 reduces the excitation voltage component by lowering the current fluctuation frequency fh of the d-axis high-frequency current flowing through the stator winding 52. With this configuration, it is possible to suppress the output voltage of the inverter 20 while suppressing a decrease in the output torque of the rotating electric machine 40, compared to a case in which the excitation voltage component is reduced by reducing the current amplitude Idamp of the d-axis high-frequency current flowing through the stator winding 52.

[0086] When excitation reduction control is not executed, the excitation current calculation unit 102 keeps constant the amplitude Idamp, the fluctuation frequency fh, and the phase of the d-axis high-frequency current that is passed through the stator winding 52. With this configuration, when excitation reduction control is not executed, the excitation voltage component can be kept constant.

[0087] When the output voltage of the inverter 20 is higher than the limit value Vlim, the control change unit 209 changes whether or not to execute the excitation reduction control by the excitation current calculation unit 102 and the field weakening control by the field weakening unit 201 in accordance with the operating region of the rotating electric machine 40 so as to suppress the output voltage of the inverter 20. With this configuration, it is possible to suppress the output voltage of the inverter 20 from becoming higher than the limit value Vlim.

[0088] Alternatively, when the rotation speed of the rotating electric machine 40 is higher than a predetermined rotation speed, the control change unit 209 changes whether or not to execute the excitation reduction control by the excitation current calculation unit 102 and the field weakening control by the field weakening unit 201, depending on the operating region of the rotating electric machine 40, so that the output voltage of the inverter 20 is suppressed. With this configuration, when the rotation speed of the rotating electric machine 40 is higher than the predetermined rotation speed, the output voltage of the inverter 20 can be suppressed, and the rotation speed of the rotating electric machine 40 can be increased above the predetermined rotation speed.

[0089] The excitation reduction control for reducing the magnetic flux of the rotor 60 in the high-speed region is performed by the control device 30, which also controls the torque of the rotating electric machine 40. Therefore, the excitation reduction control and the torque control can be achieved by common switching control of the inverter 20. This also contributes to the simplification of the rotating electric machine system 90. Furthermore, since the excitation voltage component is reduced by the switching control of the inverter 20, the output voltage of the inverter 20 can be quickly reduced.

[0090] Modification of First Embodiment The excitation parameter calculation unit 113 may vary only the fluctuation frequency fh of the fluctuation frequency fh and the amplitude Idamp based on the deviation amount Xh.

[0091] The excitation parameter calculation unit 113 may vary only the amplitude Idamp of the fluctuation frequency fh and the amplitude Idamp based on the deviation amount Xh. In this case, the excitation parameter calculation unit 113 may start to reduce the amplitude Idamp when the deviation amount Xh exceeds 0, similar to the reduction manner of the fluctuation frequency fh.

[0092] Second Embodiment A second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, the voltage amplitude Vom is calculated using U-, V-, and W-phase voltages VUr, VVr, and VWr detected by the voltage sensor 23, rather than the d- and q-axis voltage command values ​​Vdref and Vqref.

[0093] FIG. 11 is a block diagram of the excitation current calculation unit 102.

[0094] In the excitation current calculation unit 102, the voltage calculation unit 114 calculates the d- and q-axis voltages Vdr, Vqr based on the U-, V-, and W-phase voltages VUr, VVr, and VWr detected by the voltage sensor 23 and the electrical angle θe. More specifically, the voltage calculation unit 114 calculates the d- and q-axis voltages Vdr, Vqr based on the following equations (eq7) and (eq8).

[0095]

[0096] The voltage amplitude calculation unit 115 calculates the voltage amplitude Vom based on the calculated d-axis and q-axis voltages Vdr and Vqr. More specifically, the voltage amplitude calculation unit 115 calculates the voltage amplitude Vom based on the following equation (eq9). The calculated voltage amplitude Vom is output to the voltage deviation calculation unit 111.

[0097] According to the present embodiment described above, it is possible to achieve effects similar to those of the first embodiment. Note that, similar to the modified example of the first embodiment, the excitation parameter calculation unit 113 may vary only one of the fluctuating frequency fh and the amplitude Idamp based on the deviation amount Xh.

[0098] Third Embodiment A third embodiment will now be described with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, a method is used in which the excitation voltage component of the field winding 70 is reduced by increasing the d-axis current flowing through the stator winding 52. The reason why this method can be used will be described.

[0099] When the d-axis current is increased, the d-axis inductance Ld decreases due to the effects of magnetic saturation. In the term enclosed in curly brackets on the right side of equation (eq5) above, the smaller the d-axis inductance Ld, the smaller the excitation voltage component. Therefore, by increasing the d-axis current, the excitation voltage component of the field winding 70 can be reduced.

[0100] FIG. 12 is a block diagram showing the torque control process executed by the control device 30.

[0101] The d-axis command calculation unit 125 calculates the d-axis basic command current Idbref based on the command torque Tref. For example, the d-axis command calculation unit 125 may calculate the d-axis basic command current Idbref based on map information in which the command torque Tref and the d-axis basic command current Idbref are correlated, and the input command torque Tref.

[0102] The inductance decreasing current calculation unit 130 functions as an "excitation decreasing unit" and calculates an inductance decreasing current IdL, which is a d-axis current to be superimposed on the d-axis basic command current Idbref, based on the calculated d-axis and q-axis voltage command values ​​Vdref and Vqref. The inductance decreasing current IdL has a DC component value.

[0103] The first adder 122 calculates the sum of the d-axis basic command current Idbref and the inductance decreasing current IdL.

[0104] The second adder 123 calculates the d-axis command current Idref by adding the d-axis high-frequency command current Idhref calculated by the excitation current calculation unit 102 to the sum calculated by the first adder 122. The calculated d-axis command current Idref is input to the d-axis deviation calculation unit 104.

[0105] The q-axis command calculation unit 124 calculates the q-axis command current Iqref based on the command torque Tref and the sum "Idbref+IdL" calculated by the first adder 122. The sum is used to calculate the q-axis command current Iqref because an appropriate q-axis current corresponding to the command torque Tref changes depending on the magnitude of the inductance decreasing current IdL. The q-axis command calculation unit 124 may calculate the q-axis command current Iqref based on, for example, map information in which the command torque Tref, the sum, and the q-axis command current Iqref are correlated, and the input command torque Tref and the sum. The calculated q-axis command current Iqref is input to the q-axis deviation calculation unit 105.

[0106] Next, the processing of the inductance decreasing current calculation unit 130 will be described with reference to FIG.

[0107] The inductance decreasing current calculation unit 130 includes a voltage amplitude calculation unit 131, a voltage deviation calculation unit 132, and a feedback control unit 133. The voltage amplitude calculation unit 131 calculates the voltage amplitude Vom based on the d-axis and q-axis voltage command values ​​Vdref and Vqref, similar to the voltage amplitude calculation unit 110 shown in FIG.

[0108] The voltage deviation calculation unit 132 calculates the voltage deviation ΔV by subtracting the limit value Vlim from the calculated voltage amplitude Vom.

[0109] The feedback control unit 133 calculates a deviation amount Xh, which is a manipulated variable for feedback-controlling the calculated voltage deviation ΔV to 0. In this embodiment, the feedback control used by the feedback control unit 133 is proportional-integral control.

[0110] The inductance decreasing current calculation unit 130 includes a current value calculation unit 134. The current value calculation unit 134 calculates the inductance decreasing current IdL based on the calculated deviation amount Xh. More specifically, when the deviation amount Xh is equal to or less than 0, the inductance decreasing current calculation unit 130 sets the inductance decreasing current IdL to 0.

[0111] When the deviation amount Xh is greater than 0 and less than the threshold value Xth, the current value calculation unit 134 sets the inductance decreasing current IdL to a value greater than 0 and less than the predetermined current IK (>0), and the larger the deviation amount Xh, the larger the value. When the deviation amount Xh is equal to or greater than the threshold value Xth, the current value calculation unit 134 sets the inductance decreasing current IdL to the predetermined current IK. In this way, the inductance decreasing current calculation unit 130 increases (adjusts) the inductance decreasing current IdL, and therefore decreases (adjusts) the excitation voltage component. That is, when the deviation amount Xh increases, the inductance decreasing current calculation unit 130 decreases the d-axis inductance Ld from the current d-axis inductance Ld.

[0112] 14 shows a flowchart of the excitation reduction control process executed by the control device 30. This process is executed repeatedly at a predetermined control period, for example.

[0113] In step S30, the voltage amplitude calculation unit 131 calculates the voltage amplitude Vom based on the d-axis and q-axis voltage command values ​​Vdref and Vqref.

[0114] In step S31, the voltage deviation calculation unit 132 calculates the voltage deviation ΔV based on the calculated voltage amplitude Vom.

[0115] In step S32, the feedback control unit 133 calculates the deviation amount Xh based on the calculated voltage deviation ΔV.

[0116] In step S33, the current value calculation unit 134 calculates the inductance decreasing current IdL based on the calculated deviation amount Xh.

[0117] In step S34, the calculated inductance decreasing current IdL is output to the first adder 122. After that, this series of processes is temporarily ended.

[0118] In this embodiment, when suppressing the output voltage of the inverter 20, the control change unit 209 causes the inductance decreasing current calculation unit 130 to execute excitation decreasing control instead of the excitation current calculation unit 102. That is, when suppressing the output voltage of the inverter 20, the control change unit 209 causes the inductance decreasing current calculation unit 130 to execute excitation decreasing control and causes the field weakening unit 201 to execute field weakening control in a high load region of the rotating electric machine 40. When not executing excitation decreasing control, the inductance decreasing current calculation unit 130 keeps the inductance decreasing current IdL constant. Specifically, as shown in FIG. 13 , when the deviation amount Xh is equal to or less than 0, the inductance decreasing current IdL is set to 0. Furthermore, when suppressing the output voltage of the inverter 20, the control change unit 209 causes the inductance decreasing current calculation unit 130 to execute excitation decreasing control in a low load region of the rotating electric machine 40 without executing field weakening control in the field weakening unit 201.

[0119] The excitation voltage component increases as the d-axis inductance Ld of the field winding 70 increases. Therefore, in the excitation reduction control, the inductance reduction current calculation unit 130 reduces the excitation voltage component by increasing the d-axis current flowing through the stator winding 52 from the current value and reducing the d-axis inductance Ld of the field winding 70 from the current value due to magnetic saturation. With this configuration, the excitation voltage component can be reduced by utilizing magnetic saturation.

[0120] The above-described embodiments can be modified as follows: The same parts as those in the above-described embodiments are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0121] 15 , when the rotating electric machine 40 outputs the same torque at the same rotational speed under the excitation reduction control and the field weakening control from the low torque region to the high torque region, the output voltage of the inverter 20 during the field weakening control may have a characteristic such that the output voltage of the inverter 20 during the field weakening control is lower than the output voltage of the inverter 20 during the excitation reduction control. In this case, when suppressing the output voltage of the inverter 20, the control change unit 209 does not cause the excitation current calculation unit 102 (or the inductance reduction current calculation unit 130) to execute the excitation reduction control in the low torque region of the rotating electric machine 40, but instead causes the field weakening unit 201 to execute the field weakening control. Therefore, it is possible to execute the field weakening control that can further lower the output voltage of the inverter 20 in the low torque region in accordance with the characteristics of the rotating electric machine 40, and it is possible to suppress the output voltage of the inverter 20.

[0122] As shown in FIG. 16 , before the excitation voltage component is reduced, the phase of the harmonic current, determined by the amplitudes of the d-axis component and q-axis component of the harmonic current relative to the phase of the fundamental current, is the phase at which the harmonic current can most efficiently cause the field current to flow through the field winding 70 (the phase at which the field current is maximized when compared with high-frequency currents of the same magnitude). Therefore, the field current can be reduced by changing the phase of the harmonic current relative to the fundamental current. That is, the magnitude of the excitation voltage component varies depending on the phase of the high-frequency current that flows through the stator winding 52 and causes the field current to flow through the field winding 70. Therefore, the excitation current calculation unit 102 reduces the excitation voltage component by adjusting the phase of the high-frequency current during excitation reduction control. With this configuration, the excitation voltage component can be reduced by utilizing the relationship between the phase of the high-frequency current that causes the field current to flow through the field winding 70 and the excitation voltage component.

[0123] As shown in FIG. 17 , the output voltage vector of the inverter 20 includes a base voltage and an excitation voltage required for excitation. The output voltage vector is limited by a limit value Vlim. The magnitude of the excitation voltage in the d-axis direction is greater than the magnitude of the excitation voltage in the q-axis direction. Therefore, when the output voltage vector is limited by the limit value Vlim, the excitation voltage increases as the phase of the output voltage vector approaches the d-axis. Therefore, as shown by the dashed line in FIG. 5 , the phase calculation unit 202 (excitation reduction unit) may reduce the excitation voltage component by moving the phase of the output voltage vector of the inverter 20 closer to the q-axis than it currently is during excitation reduction control. With this configuration, the excitation voltage component can be reduced by utilizing the relationship between the phase of the output voltage vector of the inverter 20 and the excitation voltage.

[0124] The rotating electric machine 40 of the first to third embodiments has a characteristic that, when the rotating electric machine 40 outputs the same torque in the excitation reduction control and the field weakening control in the low torque region, the output voltage of the inverter 20 in the field weakening control is lower than the output voltage of the inverter 20 in the excitation reduction control when the fundamental current is greater than the threshold value, and the output voltage of the inverter 20 in the excitation reduction control is lower than the output voltage of the inverter 20 in the field weakening control when the fundamental current is smaller than the threshold value. Therefore, when suppressing the output voltage of the inverter 20, the control change unit 209 may execute the excitation reduction control by the excitation current calculation unit 102 and the field weakening control by the field weakening unit 201 in the low torque region of the rotating electric machine 40. With this configuration, the output voltage of the inverter 20 can be stably suppressed even when the control that can further reduce the output voltage of the inverter 20 changes depending on the magnitude of the fundamental current. The control change unit 209 may cause the inductance decreasing current calculation unit 130 to execute excitation decreasing control instead of the excitation current calculation unit 102 .

[0125] The high-frequency current (specifically, high-frequency excitation current) passed through the stator winding 52 is not limited to a harmonic current whose fluctuating frequency is N times (N is an integer of 2 or more) the frequency of the fundamental wave current, but may be a current whose fluctuating frequency is not N times the frequency of the fundamental wave current.

[0126] The second winding portion 71b may be disposed closer to the stator 50 in the radial direction than the first winding portion 71a.

[0127] The capacitor 81 that constitutes the resonant circuit of the rotor 60 may be electrically connected in parallel to the first winding portion 71a instead of the second winding portion 71b.

[0128] The capacitor 81 does not have to be provided in the resonant circuit of the rotor 60 .

[0129] The rotating electric machine is not limited to an inner rotor type rotating electric machine, and may be an outer rotor type rotating electric machine. In this case, the main pole portion protrudes radially inward from the rotor core.

[0130] The rotating electric machine is not limited to a star-connected rotating electric machine, and may be a delta-connected rotating electric machine.

[0131] In the first embodiment, the stator core may not be provided with teeth.

[0132] The rotating electric machine is not limited to a rotating electric machine used as an in-vehicle main engine, but may be, for example, a rotating electric machine used as an ISG (Integrated Starter Generator) that is a motor and generator.

[0133] The moving body on which the rotating electric machine system 90 is mounted is not limited to a vehicle, but may be, for example, an aircraft or a ship. Furthermore, the rotating electric machine system 90 is not limited to a system mounted on a moving body, but may be a stationary system.

[0134] The control device 30 and the method described herein may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to execute one or more functions (instructions) embodied in a computer program. Alternatively, the control device 30 and the method described herein may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control device 30 and the method described herein may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to execute one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by a computer on a computer-readable non-transitory tangible storage medium.

[0135] The above-described embodiments and modifications may be combined within the scope of possible combinations.

[0136] The following describes characteristic configurations extracted from the above-described embodiments and modified examples. [Configuration 1] A control device (30) for a rotating electric machine applied to a rotating electric machine system (90) including: a rotating electric machine (40) having a stator (50) including a stator winding (52) and a rotor (60) including a field winding (70), and an inverter (20) electrically connected to the stator winding, wherein the rotating electric machine is configured so that a high-frequency voltage is applied to the stator winding to induce a voltage in the field winding and cause a field current to flow, a switch control unit (109) performing switching control of the inverter so as to apply to the stator winding a composite voltage of the high-frequency voltage and a fundamental voltage having a frequency different from the high-frequency voltage, and an excitation reduction unit (102, 130, 202) performing excitation reduction control to reduce, from a current level, an excitation voltage component, which is a component that causes the field current to flow in the field winding, among voltage components included in the composite voltage. a field weakening unit (201) that performs field weakening control by adjusting the phase of a fundamental wave current flowing through the stator winding using the fundamental wave voltage so as to generate a magnetic flux in an opposite direction to the magnetic flux generated by the field winding, and a control change unit (209) that changes whether or not to execute the excitation reduction control by the excitation reduction unit and the field weakening control by the field weakening unit according to an operating range of the rotating electric machine so as to suppress an output voltage of the inverter. [Configuration 2] The rotating electric machine has a characteristic that, when the rotating electric machine outputs the same torque under the excitation reduction control and the field weakening control in a high load range, the output voltage of the inverter during the field weakening control is lower than the output voltage of the inverter during the excitation reduction control, and the control change unit does not execute the excitation reduction control by the excitation reduction unit but executes the field weakening control by the field weakening unit in the high load range of the rotating electric machine when suppressing the output voltage of the inverter.[Configuration 3] The control device for a rotating electric machine according to Configuration 1 or 2, wherein, in a low load region, when the rotating electric machine outputs the same torque through the excitation reduction control and the field weakening control, the output voltage of the inverter during the excitation reduction control is lower than the output voltage of the inverter during the field weakening control, and when the control change unit suppresses the output voltage of the inverter, in the low load region of the rotating electric machine, the field weakening control is not performed by the field weakening unit, but the excitation reduction control is performed by the excitation reduction unit. [Configuration 4] The rotating electric machine has a characteristic that when the rotating electric machine outputs the same torque with the excitation reduction control and the field weakening control from a low load region to a high load region, the output voltage of the inverter during the field weakening control is lower than the output voltage of the inverter during the excitation reduction control, and the control change unit, when suppressing the output voltage of the inverter, does not cause the excitation reduction unit to execute the excitation reduction control in the low load region of the rotating electric machine, but causes the field weakening unit to execute the field weakening control. This is the control device for a rotating electric machine according to Configuration 1 or 2. [Configuration 5] The rotating electric machine has a characteristic such that, when the rotating electric machine outputs the same torque under the excitation reduction control and the field weakening control in a low load region, if the fundamental wave current is greater than a threshold value, the output voltage of the inverter under the excitation reduction control is lower than the output voltage of the inverter under the excitation reduction control, and if the fundamental wave current is less than the threshold value, the output voltage of the inverter under the excitation reduction control is lower than the output voltage of the inverter under the field weakening control, and the control change unit causes the excitation reduction unit to execute the excitation reduction control and the field weakening control in a low load region of the rotating electric machine when suppressing the output voltage of the inverter. [Configuration 6] The control device for a rotating electric machine according to any one of Configurations 1 to 5, wherein the excitation reduction unit (102) reduces the excitation voltage component by reducing the amplitude of a d-axis high frequency current flowing through the stator winding from a current amplitude in the excitation reduction control.[Configuration 7] The control device for a rotating electric machine according to any one of configurations 1 to 5, wherein the excitation reducer (102) reduces the excitation voltage component by lowering the frequency of a d-axis high-frequency current passed through the stator winding from a current value during the excitation reduce control. [Configuration 8] The control device for a rotating electric machine according to any one of configurations 1 to 5, wherein the excitation reducer (130) reduces the excitation voltage component by increasing the d-axis current passed through the stator winding from a current value and reducing the inductance of the field winding from a current value due to magnetic saturation during the excitation reduce control. [Configuration 9] The control device for a rotating electric machine according to any one of configurations 1 to 5, wherein the excitation reducer (102) reduces the excitation voltage component by adjusting the phase of a high-frequency current that flows through the stator winding to cause the field current to flow through the field winding so that a d-axis current component of the amplitude of the high-frequency current is reduced during the excitation reduce control. [Configuration 10] The control device for a rotating electric machine according to any one of configurations 1 to 5, wherein the excitation reducer (202) reduces the excitation voltage component by bringing the phase of the output voltage vector of the inverter closer to the q-axis than at present in the excitation reduce control. [Configuration 11] The control device for a rotating electric machine according to configurations 2 or 4, wherein the excitation reducer keeps constant the amplitude, frequency, and phase of the d-axis high-frequency current to be passed through the stator winding when the excitation reducer is not executing the excitation reduce control. [Configuration 12] The control device for a rotating electric machine according to any one of configurations 1 to 11, wherein the control changer changes whether or not to execute the excitation reduce control by the excitation reducer and the field weakening control by the field weakening unit in accordance with an operating region of the rotating electric machine so as to suppress the output voltage of the inverter when the output voltage of the inverter is higher than a voltage limit value. [Configuration 13] The control device for a rotating electric machine according to any one of Configurations 1 to 11, wherein the control change unit changes whether or not to perform the excitation reduction control by the excitation reduction unit and the field weakening control by the field weakening unit, depending on an operating region of the rotating electric machine, so that the output voltage of the inverter is suppressed when the rotation speed of the rotating electric machine is higher than a predetermined rotation speed.

[0137] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A control device for a rotating electrical machine applied to a rotating electrical machine system (90) comprising: a rotating electrical machine (40) having a stator (50) including a stator winding (52) and a rotor (60) including a field winding (70); and an inverter (20) electrically connected to the stator winding, wherein the rotating electrical machine is configured such that a voltage is induced in the field winding and a field current flows when a high-frequency voltage is applied to the stator winding, the inverter having a switch control unit (109) that performs switching control to apply a combined voltage of the high-frequency voltage and a fundamental voltage having a frequency different from that of the high-frequency voltage to the stator winding, an excitation reduction unit (102, 130, 202) that performs excitation reduction control to reduce an excitation voltage component, which is a component for flowing the field current in the field winding, among voltage components included in the combined voltage, relative to the current level, and a field weakening unit (201) that performs field weakening control to adjust a phase of a fundamental current flowing through the stator winding by the fundamental voltage so as to generate a magnetic flux opposite to a magnetic flux generated by the field winding, and a control change unit (209) that changes whether to execute the excitation reduction control by the excitation reduction unit and the field weakening control by the field weakening unit according to an operating region of the rotating electrical machine so as to suppress an output voltage of the inverter.

2. The control device for a rotating electrical machine according to claim 1, wherein in a high-load region, when the rotating electrical machine outputs the same torque by the excitation reduction control and the field weakening control, the output voltage of the inverter during the field weakening control is lower than the output voltage of the inverter during the excitation reduction control, and the control change unit does not execute the excitation reduction control by the excitation reduction unit but executes the field weakening control by the field weakening unit in the high-load region of the rotating electrical machine when suppressing the output voltage of the inverter.

3. When the rotating electrical machine outputs the same torque by the field weakening control and the field reduction control in the low load region, the output voltage of the inverter during the field reduction control is lower than the output voltage of the inverter during the field weakening control. When suppressing the output voltage of the inverter, the control change unit causes the field reduction control by the field reduction unit to be executed without causing the field weakening control by the field weakening unit in the low load region of the rotating electrical machine. The control device for a rotating electrical machine according to claim 1 or 2.

4. When the rotating electrical machine outputs the same torque by the field reduction control and the field weakening control from the low load region to the high load region, the output voltage of the inverter during the field weakening control is lower than the output voltage of the inverter during the field reduction control. When suppressing the output voltage of the inverter, the control change unit causes the field weakening control by the field weakening unit to be executed without causing the field reduction control by the field reduction unit in the low load region of the rotating electrical machine. The control device for a rotating electrical machine according to claim 1 or 2.

5. When the rotating electrical machine outputs the same torque by the field reduction control and the field weakening control in the low load region, when the fundamental wave current is greater than the threshold value, the output voltage of the inverter during the field weakening control is lower than the output voltage of the inverter during the field reduction control, and when the fundamental wave current is less than the threshold value, the output voltage of the inverter during the field reduction control is lower than the output voltage of the inverter during the field weakening control. When suppressing the output voltage of the inverter, the control change unit causes the field reduction control by the field reduction unit and the field weakening control by the field weakening unit to be executed in the low load region of the rotating electrical machine. The control device for a rotating electrical machine according to claim 1 or 2.

6. The field reduction unit (102) reduces the field voltage component by reducing the amplitude of the d-axis high-frequency current flowing through the stator winding in the field reduction control compared to the present. The control device for a rotating electrical machine according to claim 1 or 2.

7. The field weakening unit (102) reduces the field voltage component by reducing the frequency of the d-axis high-frequency current flowing through the stator winding to be lower than the current value in the field weakening control, in the control device for a rotating electrical machine according to claim 1 or 2.

8. The field weakening unit (130) reduces the field voltage component by increasing the d-axis current flowing through the stator winding to be higher than the current value and reducing the inductance of the field winding due to magnetic saturation in the field weakening control, in the control device for a rotating electrical machine according to claim 1 or 2.

9. The field weakening unit (102) reduces the field voltage component by adjusting the phase of the high-frequency current flowing through the stator winding to flow the field current through the field winding so that the d-axis current component of the amplitude of the high-frequency current decreases in the field weakening control, in the control device for a rotating electrical machine according to claim 1 or 2.

10. The field weakening unit (202) reduces the field voltage component by making the phase of the output voltage vector of the inverter closer to the q-axis than the current value in the field weakening control, in the control device for a rotating electrical machine according to claim 1 or 2.

11. The field weakening unit keeps the amplitude, frequency, and phase of the d-axis high-frequency current flowing through the stator winding constant when the field weakening control is not executed, in the control device for a rotating electrical machine according to claim 2.

12. When the output voltage of the inverter is higher than the voltage limit value, the control change unit changes whether to execute the field weakening control by the field weakening unit and the field weakening control by the field weakening unit according to the operating region of the rotating electrical machine so that the output voltage of the inverter is suppressed, in the control device for a rotating electrical machine according to claim 1 or 2.

13. When the rotational speed of the rotating electrical machine is higher than a predetermined rotational speed, the control change unit changes whether to execute the field weakening control by the field weakening unit and the field weakening control by the field weakening unit according to the operating region of the rotating electrical machine so that the output voltage of the inverter is suppressed, in the control device for a rotating electrical machine according to claim 1 or 2.

14. A control program for a rotating electrical machine applied to a rotating electrical machine system (90) comprising: a rotating electrical machine (40) having a stator (50) including a stator winding (52) and a rotor (60) including a field winding (70); and an inverter (20) electrically connected to the stator winding, wherein the rotating electrical machine is configured such that a voltage is induced in the field winding and a field current flows when a high-frequency voltage is applied to the stator winding, the method comprising: a process of performing switching control of the inverter to apply a combined voltage of the high-frequency voltage and a fundamental voltage having a frequency different from that of the high-frequency voltage to the stator winding; a process of performing field reduction control for reducing a field voltage component, which is a component for flowing the field current in the field winding, among the voltage components included in the combined voltage, to be less than the current value; a process of performing field weakening control for adjusting a phase of a fundamental current flowing through the stator winding by the fundamental voltage so as to generate a magnetic flux opposite to a magnetic flux generated by the field winding; and a process of changing whether or not to execute the field reduction control and the field weakening control according to an operating region of the rotating electrical machine so that an output voltage of the inverter is suppressed, the control program causing a computer (30) to execute the processes.

15. A rotating electrical machine system (90) comprising a rotating electrical machine (40) having a stator (50) including a stator winding (52) and a rotor (60) including a field winding (70), an inverter (20) electrically connected to the stator winding, and a control device (30) for the rotating electrical machine, wherein the rotating electrical machine is configured such that a voltage is induced in the field winding and a field current flows when a high-frequency voltage is applied to the stator winding, and the control device includes a switch control unit (109) that performs switching control of the inverter so as to apply a combined voltage of the high-frequency voltage and a fundamental voltage having a frequency different from that of the high-frequency voltage to the stator winding, an excitation reduction unit (102, 130, 202) that performs excitation reduction control for reducing an excitation voltage component, which is a component for flowing the field current in the field winding, among the voltage components included in the combined voltage, from the current level, a field weakening unit (201) that performs field weakening control for adjusting the phase of a fundamental current flowing in the stator winding by the fundamental voltage so as to generate a magnetic flux opposite to the magnetic flux generated by the field winding, and a control change unit (209) that changes the execution of the excitation reduction control by the excitation reduction unit and the field weakening control by the field weakening unit according to the operating region of the rotating electrical machine so as to suppress the output voltage of the inverter.

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