Rotating electric machine drive device and rotating electric machine drive method

Abstract

To provide a driving device of a rotary electric machine capable of suppressing temperature rise of a permanent magnet while keeping torque.SOLUTION: A driving device 1 of a rotary electric machine 10 having a stator provided with a stator winding, and a rotor provided with a permanent magnet comprises: a power conversion circuit 3 that outputs a phase current to a stator winding; and a controller 5 for controlling the power conversion circuit. When a phase voltage peak value with respect to a voltage of DC power is defined as a modulation rate, if a temperature of the permanent magnet is higher than a predetermined first threshold temperature and the modulation rate is larger than a predetermined threshold value, the controller reduces a current amplitude and a current lead angle of the phase current, and if a temperature of the permanent magnet is higher than the first threshold temperature and the modulation rate is smaller than the threshold value, the controller increases the current amplitude and the current lead angle of the phase current.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present application relates to a driving device for a rotating electric machine and a driving method for a rotating electric machine. [Background technology]

[0002] In a rotating electric machine having a permanent magnet, torque decreases when the temperature of the permanent magnet rises and demagnetization occurs. Control methods for preventing this demagnetization include a control method for suppressing the current of the rotating electric machine depending on the temperature of the permanent magnet of the rotating electric machine and a control method for changing the carrier frequency. For example, a technology has been disclosed that determines whether the current flowing through the stator winding is an overcurrent depending on the estimated temperature of the permanent magnet, and limits the current based on the determination result (see, for example, Patent Document 1). Also disclosed is a technology that synchronously controls the carrier frequency when the temperature of the permanent magnet exceeds a predetermined threshold (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-114167 [Patent Document 2] Japanese Patent Application Laid-Open No. 2019-170098 Summary of the Invention [Problem to be solved by the invention]

[0004] However, conventional control technologies for rotating electric machines do not identify the factors that cause the temperature of permanent magnets to rise, and therefore cannot control the permanent magnets to minimize demagnetization depending on the operating state, resulting in the problem that it is not possible to suppress the temperature rise of the permanent magnets while maintaining torque.

[0005] The present application has been made to solve the above-mentioned problems, and has an object to provide a driving device for a rotating electric machine that can suppress a temperature rise in a permanent magnet while maintaining torque. [Means for solving the problem]

[0006] The driving device for a rotating electric machine of the present application is a driving device for a rotating electric machine having a stator with a stator winding of three or more phases and a rotor with a permanent magnet, and includes a power conversion circuit that converts DC power input from a power source and outputs phase current to the stator winding, and a control unit that controls the power conversion circuit. A threshold value is set in advance for the modulation factor when the phase voltage peak value relative to the voltage of the DC power is defined as the modulation factor. The control unit decreases the current amplitude and current advance angle of the phase current output from the power conversion circuit when the temperature of the permanent magnet is higher than a predetermined first threshold temperature and the modulation factor is greater than the threshold value, and increases the current amplitude and current advance angle of the phase current output from the power conversion circuit when the temperature of the permanent magnet is higher than the first threshold temperature and the modulation factor is smaller than the threshold value. [Effects of the Invention]

[0007] In the driving device for the rotating electric machine of the present application, the control unit reduces the current amplitude and current advance angle of the phase current output from the power conversion circuit when the temperature of the permanent magnet is higher than a predetermined first threshold temperature and the modulation rate is greater than the threshold, and increases the current amplitude and current advance angle of the phase current output from the power conversion circuit when the temperature of the permanent magnet is higher than the first threshold temperature and the modulation rate is smaller than the threshold, thereby making it possible to suppress temperature rise of the permanent magnet while maintaining torque. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram of a driving device for a rotating electric machine according to a first embodiment. [Figure 2] 1 is a cross-sectional view of a rotating electric machine according to a first embodiment. [Figure 3] FIG. 2 is a block diagram of a control unit according to the first embodiment. [Figure 4] 4 is a schematic diagram showing a modulation factor defined by a comparison between a triangular wave and a sine wave in the first embodiment. FIG. [Figure 5] 4 is a schematic diagram of a rectangular wave phase voltage output by comparing a triangular wave with a sine wave in the first embodiment. FIG. [Figure 6] FIG. 3 is a diagram illustrating definitions of a current amplitude and a current lead angle according to the first embodiment. [Figure 7] FIG. 4 is a characteristic diagram showing the relationship between the modulation factor and the harmonic voltage relative to the DC bus voltage in the first embodiment. [Figure 8] FIG. 4 is a characteristic diagram showing the relationship between modulation rate and eddy current loss of a permanent magnet in the first embodiment. [Figure 9] 4 is a characteristic diagram showing the relationship between the current advance angle and the current amplitude in the rotary electric machine according to the first embodiment. FIG. [Figure 10] FIG. 10 is a diagram showing when the modulation factor in the relationship between rotation speed and torque changes to 0.6 in the first embodiment. [Figure 11] 5 is a diagram illustrating control of current amplitude and current advance angle when the modulation factor is reduced in the first embodiment. FIG. [Figure 12] 5 is a diagram illustrating control of current amplitude and current advance angle when the modulation factor is increased in the first embodiment. FIG. [Figure 13] 5 is a flowchart showing a driving method in the driving device for the rotary electric machine according to the first embodiment. [Figure 14] FIG. 10 is a block diagram of a control unit according to a second embodiment. [Figure 15] 10 is a flowchart showing a driving method in the driving device for the rotary electric machine according to the second embodiment. [Figure 16] 10 is a schematic diagram showing control of current amplitude and current advance angle in a driving device for a rotary electric machine according to a second embodiment. FIG. [Figure 17] 10 is a schematic diagram showing control of current amplitude and current advance angle in a driving device for a rotary electric machine according to a second embodiment. FIG. [Figure 18] FIG. 10 is a characteristic diagram showing changes in the temperature of a permanent magnet in the driving device for a rotary electric machine according to the second embodiment. [Figure 19] FIG. 11 is a characteristic diagram showing the relationship between the modulation factor and the harmonic voltage relative to the DC bus voltage in the third embodiment. [Figure 20]FIG. 11 is a diagram showing the carrier frequency required to eliminate eddy current loss in the permanent magnet versus the thickness of the permanent magnet in the third embodiment. [Figure 21] 2 is a diagram showing a hardware configuration for realizing a control unit of a driving device for a rotating electric machine according to first to third embodiments. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed description of a driving device for a rotating electric machine according to an embodiment of the present invention will now be given with reference to the accompanying drawings. It should be noted that the same reference numerals in the various drawings indicate the same or corresponding parts.

[0010] Embodiment 1 FIG. 1 is a configuration diagram of a driving device for a rotating electric machine according to a first embodiment. The driving device 1 for a rotating electric machine according to this embodiment is provided between a DC power supply 90 and a rotating electric machine 10. The DC power supply 90 is a secondary battery that can be charged and discharged. The driving device 1 is connected to the DC power supply 90 via a power switch 70 and input terminals 11 through DC buses 1a and 1b, and is connected to the rotating electric machine 10 via an AC bus 2a through output terminals 12. The driving device 1 exchanges driving power and regenerative power with the rotating electric machine 10.

[0011] Fig. 2 is a cross-sectional view of a rotating electric machine according to this embodiment. Fig. 2 is a cross-sectional view of a plane perpendicular to the rotation axis of the rotating electric machine. The rotating electric machine 10 is composed of an annular stator 20 and a cylindrical rotor 40 arranged on the inner periphery of the stator 20 with a gap therebetween. A rotating shaft 50 is fixed to the center of the rotor 40. The rotor 40 is rotatably supported relative to the stator 20 via the rotating shaft 50.

[0012] The stator 20 is made up of a stator core 21 and a stator winding 22. The stator core 21 is made up of an annular core back 23 and teeth 24 protruding inward from the core back 23. Thirty-six teeth 24 are arranged at equal intervals in the circumferential direction, with slots formed between adjacent teeth 24. The stator winding 22 is wound around the teeth 24 by utilizing the slots. The rotating electric machine 10 of this embodiment is a three-phase rotating electric machine, and the stator winding 22 is wound using a distributed winding method with three phases, U-phase, V-phase, and W-phase windings.

[0013] The rotor 40 is composed of a rotor core 41 and permanent magnets 42. The rotor core 41 has magnet insertion holes 43, and the permanent magnets 42 are embedded in the magnet insertion holes 43 and fixed to the rotor core 41. In the rotor 40, four permanent magnets are arranged in two layers in a V shape facing outward in the circumferential direction to form one magnetic pole. The rotor 40 of the rotating electric machine of this embodiment is composed of six poles.

[0014] As shown in FIG. 2, in the rotating electric machine 10, the direction of the center of the magnetic flux generated by one magnetic pole of the rotor 40 is the d-axis, and the direction electrically perpendicular to this d-axis is the q-axis. In the rotating electric machine 10 of this embodiment, one magnetic pole is configured with two layers, so the salient pole ratio, which is the difference between the d-axis inductance and the q-axis inductance, is improved. This increases the reluctance torque, improving the torque of the rotating electric machine 10. On the other hand, if the permanent magnets 42 are arranged in two or more layers, the fluctuation in inductance when the rotor 40 rotates becomes larger, and the eddy current generated in the permanent magnets 42 increases. This causes the temperature of the permanent magnets 42 to rise.

[0015] The drive device 1 includes a capacitor 2, a power conversion circuit 3, a current detection unit 4, a control unit 5, and a voltage detection unit 6. The capacitor 2 is connected between DC buses 1a and 1b, and has functions such as suppressing pulsation in the DC bus voltage, improving the drive capability of the AC power of the drive device 1 by reducing the power supply impedance of the drive device 1, and absorbing surge voltages input from the outside. The voltage detection unit 6 detects the voltage between the DC buses 1a and 1b as the DC bus voltage.

[0016] The power conversion circuit 3 is an inverter circuit in which six switching elements are connected in a full bridge configuration. As shown in FIG. 1 , two switching elements 31 and 32, two switching elements 33 and 34, and two switching elements 35 and 36 are connected in series with each other, and these series connections are connected in parallel between DC buses 1a and 1b. The midpoint between switching elements 31 and 32 outputs a signal to a U-phase stator winding of the rotating electric machine 10. The midpoint between switching elements 33 and 34 outputs a signal to a V-phase stator winding of the rotating electric machine 10. The midpoint between switching elements 35 and 36 outputs a signal to a W-phase stator winding of the rotating electric machine 10. The AC bus 2a is formed by three electric paths connected to the U-phase, V-phase, and W-phase stator windings. The switching elements 31, 33, and 35 connected to the DC bus 1a are referred to as upper-stage switching elements, and the switching elements 32, 34, and 36 connected to the DC bus 1b are referred to as lower-stage switching elements.

[0017] The switching elements 31 to 36 are, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) as shown in Fig. 1. For example, IGBTs (Insulated Gate Bipolar Transistors) other than MOSFETs may also be used for the switching elements 31 to 36. As shown in Fig. 1, a free wheel diode (FWD) is provided in parallel with each MOSFET of the switching elements 31 to 36, with the forward direction being the direction from the negative side to the positive side of the DC power supply 90, i.e., the direction from the lower side to the upper side.

[0018] The current detection unit 4 detects the currents flowing through the three AC buses 2a, converts the currents into voltages, and outputs current information for the rotating electric machine to the control unit 5. As shown in FIG. 1, the current detection unit 4 has shunt resistors 4a connected in series to each AC bus 2a, and detects the current flowing through each AC bus 2a using these shunt resistors 4a. The current detection unit 4 may also use a current sensor that uses a magnetic sensor such as a Hall element. The currents flowing through each AC bus 2a are currents flowing through the U-phase, V-phase, and W-phase of the stator winding, and the current detection unit 4 detects the U-phase current, V-phase current, and W-phase current.

[0019] The power switch 70 controls the exchange of power between the DC power supply 90 and the drive device 1. The power switch 70 is normally in a closed state. The power switch 70 is controlled to an open state by a higher-level system when, for example, the voltage of the DC power supply 90 exceeds a set value during regenerative operation of the rotating electric machine 10, when the voltage of the DC power supply 90 falls below a set value due to consumption of the DC power supply 90, or when the current flowing through the DC power supply 90 exceeds a set value. Here, the higher-level system is, for example, an ECU (Electronic Control Unit) of the vehicle when the rotating electric machine is used as a device in the drive system of a vehicle. The power switch 70 may be configured to be controlled by the control unit 5 of the drive device 1.

[0020] The rotating electric machine 10 is equipped with a rotation angle sensor 60 and a temperature detection unit 80. The rotation angle sensor 60 detects the rotation angle of the rotor 40 and outputs rotation angle information to the control unit 5. The temperature detection unit 80 detects the temperature of the permanent magnet 42 and outputs temperature information to the control unit 5. The rotation angle sensor 60 can be a resolver, an encoder, a magnetic sensor, or the like. The temperature of the permanent magnet can be detected using a thermocouple, for example. If a thermocouple is attached to the rotor, a slip ring can be used. If a slip ring is not used, the temperature of the permanent magnet can be detected by acquiring the thermocouple signal as a radio wave signal. When the temperature of the permanent magnet changes, the magnetic force of the permanent magnet changes, and therefore the induced voltage of the rotating electric machine also changes. It is also possible to estimate the temperature of the permanent magnet from the induced voltage of the rotating electric machine by storing the correspondence between the induced voltage of the rotating electric machine and the temperature of the permanent magnet in advance.

[0021] 3 is a block diagram of the control unit according to this embodiment. As shown in FIG. 3, the control unit 5 according to this embodiment is made up of a current command generating unit 51, a three-phase to two-phase converting unit 52, a current control unit 53, a two-phase to three-phase converting unit 54, and a PWM (Pulse Width Modulation) signal generating unit 55.

[0022] The current command generating unit 51 receives a torque command T rq * and the permanent magnet temperature T output from the temperature detection unit 80 mag The current command generating unit 51 receives the d-axis current command value I d * and the q-axis current command value I q * where the d-axis current command value I d * is the current that controls the magnetic flux generated on the d-axis, and the q-axis current command value I q * is a current that controls the magnetic flux generated on the q axis. The current command generator 51 generates the d-axis current command value I d * and the q-axis current command value I q *is output to the current control unit 53.

[0023] As will be described later, in the driving device for a rotating electric machine according to this embodiment, the current amplitude and current lead angle are controlled in accordance with the modulation rate when the permanent magnet temperature is higher than a threshold temperature. The d-axis current and the q-axis current can be calculated from the current amplitude and the current lead angle. The current command generating unit 51 may have multiple current command maps for torque commands that are created in advance using actual measurements or simulations.

[0024] The three-phase to two-phase conversion unit 52 receives the U-phase current I detected by the current detection unit 4. u , V phase current I v and W-phase current I w and an electrical angle θ, which is the rotation angle of the rotating electric machine 10 detected by the rotation angle sensor 60. e The three-phase to two-phase conversion unit 52 receives the electrical angle θ e Using the three-phase to two-phase coordinate transformation, the U-phase current I u , V phase current I v and W-phase current I w The d-axis current detection value I d and q-axis current detection value I q The three-phase to two-phase conversion unit 52 converts the d-axis current detection value I d and q-axis current detection value I q is output to the current control unit 53.

[0025] The current control unit 53 receives the d-axis current command value I d * and the q-axis current command value I q * is input, and the d-axis current detection value I d and q-axis current detection value I q The current control unit 53 receives the d-axis current command value I d * and d-axis current detection value I d and the d-axis current deviation obtained from the difference between the q * and the q-axis current detection value I qThe q-axis current deviation is calculated from the difference between the q-axis current and the d-axis voltage command value V d * and the q-axis voltage command value V q * The current control unit 53 calculates the d-axis voltage command value V d * and the q-axis voltage command value V q * to the two-phase to three-phase conversion unit 54.

[0026] The two-phase to three-phase conversion unit 54 receives the d-axis voltage command value V d * and the q-axis voltage command value V q * The two-phase to three-phase converter 54 receives the d-axis voltage command value V d * and the q-axis voltage command value V q * Based on the three-phase voltage command value in the stationary coordinate system, V u * , V v * , V w * The two-phase to three-phase conversion unit 54 converts the three-phase voltage command value, V u * , V v * , V w * to the PWM signal generating unit 55.

[0027] The PWM signal generating unit 55 receives the three-phase voltage command value, V u * , V v * , V w * is input, and the DC bus voltage V is output from the voltage detector 6. pn The PWM signal generator 55 receives the three-phase voltage command value, V u * , V v * , V w * and DC bus voltage V pnBased on this, the PWM signal generating unit 55 calculates on / off control signals UH, UL, VH, VL, WH, and WL for each switching element of the power conversion circuit 3. The PWM signal generating unit 55 outputs the on / off control signals UH, UL, VH, VL, WH, and WL obtained through the calculation to each switching element of the power conversion circuit 3.

[0028] The switching elements 31 to 36 of the power conversion circuit 3 are turned on and off by on / off control signals UH, UL, VH, VL, WH, and WL from the control unit 5. The driving device 1 for a rotating electric machine configured in this manner converts DC power input from a DC power supply 90 into AC power and supplies it to the rotating electric machine 10, and also charges the DC power supply 90 with regenerative power generated when the rotating electric machine 10 is in a regenerative operating state.

[0029] 4 is a schematic diagram showing the modulation factor defined by comparing a triangular wave with a sine wave in this embodiment. The difference between the maximum and minimum values ​​of the triangular wave is the DC bus voltage V pn and the amplitude, which is the difference from 0V, is V pn / 2. On the other hand, the sine wave is the phase voltage of the rotating electric machine. Here, the modulation factor is defined as the peak value of the phase voltage of the rotating electric machine relative to the amplitude of the triangular wave. In other words, modulation factor = peak value of the phase voltage of the rotating electric machine / (V pn / 2). To prevent the peak value of the phase voltage of the rotating electric machine from exceeding the voltage of the DC power supply, the modulation factor must be 1 or less, but there is no problem if the modulation factor is 1 or more. If the modulation factor is 1 or more, the on period in the on / off control of the switching elements becomes longer. As a result, the effective value of the voltage supplied to the rotating electric machine increases, and the output of the rotating electric machine increases. Furthermore, the sine wave is not limited to the fundamental wave only, but also includes cases where a third harmonic is superimposed.

[0030] FIG. 5 is a schematic diagram of a square wave phase voltage output by comparing a triangular wave with a sine wave. The square wave phase voltage is output by comparing the triangular wave with the sine wave in FIG. 4. When the triangular wave is larger than the sine wave, it is −V pn / 2 is output, and V is output when the triangle wave is smaller than the sine wave. pn Therefore, the difference between the maximum and minimum values ​​of the square wave phase voltage is Vpn and the DC bus voltage V pn In PWM signal generation, the effective value of the output voltage changes by adjusting the pulse width of the square wave. Note that the frequency of one period of the triangular wave is called the carrier frequency f c The carrier frequency is a frequency higher than the frequency of the sine wave. For example, if the maximum rotation speed of the rotating electric machine is 20,000 rpm, the number of poles of the rotating electric machine in this embodiment is six, so the maximum frequency of the sine wave is 1 kHz, and a carrier frequency of 1 kHz or higher is selected. Although it is possible to drive the rotating electric machine with the same frequency as the carrier frequency, the harmonic components contained in the phase current of the rotating electric machine are reduced if the carrier frequency is sufficiently higher than the frequency of the sine wave. In the case of a drive unit used in an electric vehicle, the frequency of the sine wave is about several Hz to 1 kHz, and the carrier frequency is about 1 kHz to 10 kHz. However, as will be described later, if silicon carbide (SiC) semiconductor switching elements are used as switching elements constituting the power conversion circuit, the carrier frequency can be increased to 10 kHz or higher. In addition, if the DC bus voltage V pn is also the output voltage of the DC power supply 90. For example, when the driving device for the rotating electric machine of this embodiment is used in an electric vehicle, the DC bus voltage V pn is the DC voltage of the battery, which is approximately 12V to 48V if the battery is a lead-acid battery, and approximately 200V to 400V if the battery is a nickel-metal hydride battery, lithium-ion battery, etc.

[0031] FIG. 6 is a diagram showing the definitions of current amplitude and current lead angle. a is the d-axis current i d vector and q-axis current i q The vector sum of the vectors of the phase currents is i e Then, i e is i a The value is obtained by dividing the magnitude of by √3. That is, i e =√(i d 2 +i q 2) / √3. The current amplitude is the effective value of the phase current i e The current advance angle β is defined as i a The q-axis current i q is defined as the advance angle relative to

[0032] Figure 7 shows the relationship between the modulation rate and the DC bus voltage V pn 5 is a characteristic diagram showing the relationship between the harmonic voltage and the carrier frequency f. When the waveform of the square wave phase voltage shown in FIG. 5 is decomposed into orders by Fourier transform, the square wave phase voltage contains harmonic components other than the fundamental wave. The harmonics of the waveform of the square wave phase voltage obtained by comparing it with a sine wave and a triangular wave include c If the fundamental frequency of a sine wave is f, the harmonics contained in the waveform of a square wave phase voltage include the sideband components of f c ±2f, 2f c ±f, 3f c ±2f, 4f c The magnitude of the harmonic components is calculated using the Bessel function, and for any modulation rate, 2f c The ±f component becomes larger. Figure 7 shows the 2f c ±f component DC bus voltage V pn The modulation ratio is at its maximum when it is around 0.6.

[0033] Fig. 8 is a characteristic diagram showing the relationship between the modulation factor and the eddy current loss of the permanent magnet. The frequency component of the harmonic voltage included in the waveform of the rectangular wave phase voltage is 2f c Since ±f is dominant, 2f is the frequency component of the harmonic voltage relative to the modulation rate. c Let us focus on ±f. The current flowing through a rotating electric machine is the value obtained by dividing the applied voltage by the resistance of the stator winding of the rotating electric machine. Therefore, if the voltage applied to the rotating electric machine contains harmonic components, the current flowing through the rotating electric machine will also contain harmonic frequency components that are the same as the voltage. The magnetic flux generated by the stator winding of a rotating electric machine is calculated by the product of the inductance of the rotating electric machine and the current, so the harmonic components of the magnetic flux generated from the stator winding of the rotating electric machine will also be the same as the harmonic components of the voltage. In other words, the harmonic components of the magnetic flux generated from the stator winding of a rotating electric machine also have a frequency of 2f cIn a synchronous rotating electric machine with a permanent magnet embedded in the rotor, the rotor rotates in sync with the fundamental wave component of the magnetic flux generated from the stator winding, so the loss in the rotor's permanent magnet caused by the fundamental wave component of the magnetic flux generated from the stator winding is minimal.

[0034] The loss of the rotor's permanent magnet is dominated by eddy current loss, which occurs due to the time variation of the magnetic flux that interlinks with the rotor's permanent magnet. The eddy current loss of the rotor's permanent magnet is generated by the harmonic components of the magnetic flux that are not synchronized with the rotor's rotation speed. Since the eddy current loss of the permanent magnet is generated by the square of the time derivative of the magnetic flux, the frequency components of the eddy current loss of the permanent magnet differ from the frequency components of the magnetic flux generated from the stator winding of the rotating electric machine. When the frequency of the harmonic components of the magnetic flux generated from the stator winding of the rotating electric machine is 2f c ±f, the frequency component of the eddy current loss of the permanent magnet is 2f c , 4f c The eddy current loss of the permanent magnet is 2f c The components are the fundamental frequency f of the magnetic flux and the harmonic frequency 2f c It is calculated by multiplying and adding up the trigonometric functions of ±f. On the other hand, the eddy current loss of the permanent magnet is 4f c The components are harmonic frequencies of the magnetic flux, 2f c +f and 2f c It is calculated by multiplying and adding with -f.

[0035] The eddy current loss of a permanent magnet is calculated by the square of the time derivative of the magnetic flux, so the higher the frequency of the high frequency magnetic flux, the greater the effect on the eddy current loss of the permanent magnet. Therefore, the eddy current loss of a permanent magnet is calculated by the square of the time derivative of the magnetic flux. c 4F than ingredients c The 4f component is the dominant component in eddy current loss. Figure 8 shows the 4f component of eddy current loss in a permanent magnet versus modulation factor. cThis is a characteristic diagram showing the components. The temperature of the permanent magnet rises due to eddy current loss, so in order to reduce the temperature of the permanent magnet, it is necessary to reduce the eddy current loss. Here, since eddy current loss changes depending on the modulation rate as shown in Figure 8, in order to reduce the temperature of the permanent magnet when its temperature is higher than the threshold temperature, it is necessary to control the current amplitude and current advance angle depending on the modulation rate. In other words, by controlling the current amplitude and current advance angle depending on the modulation rate so that eddy current loss is reduced, it is possible to reduce the temperature of the permanent magnet.

[0036] As shown in Figure 8, the eddy current loss of the permanent magnet is maximum when the modulation factor is near 0.6, and decreases as the modulation factor decreases when the modulation factor is smaller than 0.6, and decreases as the modulation factor increases when the modulation factor is greater than 0.6. Here, the modulation factor of 0.6 at which the eddy current loss is maximum is defined as the threshold. Therefore, in order to reduce the eddy current loss, the current amplitude and current advance angle should be controlled so that the modulation factor becomes smaller when the modulation factor is smaller than the threshold, and so that the modulation factor becomes larger when the modulation factor is greater than the threshold.

[0037] There are several methods for generating PWM rectangular wave phase voltages, in addition to the method of generating a rectangular wave phase voltage by comparing a triangular wave with a sine wave. For example, there are methods that use a sawtooth wave instead of a triangular wave, and methods that use a waveform with a superimposed third-order harmonic component instead of a sine wave. In all of these methods, the proportion of harmonic voltage supplied to the rotating electric machine changes depending on the modulation factor. Therefore, a modulation factor threshold is set corresponding to each method, and the current amplitude and current advance angle are controlled according to that threshold.

[0038] FIG. 9 is a characteristic diagram showing the relationship between the current advance angle and current amplitude for obtaining the same torque in the rotating electric machine according to this embodiment. FIG. 9 shows the characteristics of the rotating electric machine shown in FIG. 2, in which the stator winding is a distributed winding type and permanent magnets are embedded in the rotor. In a rotating electric machine with this type, reluctance torque is dominant over magnetic torque, so the current amplitude for obtaining the same torque is minimum when the current advance angle is in the range of 40 to 50 degrees. In a rotating electric machine with a concentrated winding type stator winding, magnetic torque is dominant, so the current advance angle at which the current amplitude for obtaining the same torque is minimum is smaller than in a rotating electric machine with distributed winding. Furthermore, in a surface permanent magnet type rotating electric machine in which permanent magnets are attached to the surface of the rotor, only magnetic torque is present, so the current advance angle at which the current amplitude for obtaining the same torque is minimum is 0 degrees. In either type of rotating electric machine, when controlling the current amplitude and current advance angle according to the modulation rate, by controlling the current amplitude and current advance angle while maintaining the same torque as shown in Figure 9, it is possible to suppress the temperature rise of the permanent magnet while maintaining the torque.

[0039] FIG. 10 is a diagram showing the change in modulation factor at 0.6 in the relationship between rotation speed and torque. In FIG. 10, the horizontal axis represents rotation speed, and the vertical axis represents torque. The solid line in FIG. 10 indicates the relationship between rotation speed and torque at which maximum output is obtained when the modulation factor is 1. Assuming that the rotating electric machine of this embodiment is used as the main rotating electric machine of an electric vehicle, the rotation speed and torque are used over a wide range. In this case, it is necessary to understand the modulation factor in the relationship between rotation speed and torque. As explained in the definition in FIG. 4, the modulation factor is defined by the phase voltage peak value of the rotating electric machine relative to the amplitude of the triangular wave. Here, the higher the phase voltage peak value, the greater the induced voltage generated in the rotating electric machine. Therefore, as the rotation speed increases, the modulation factor also increases. Furthermore, as torque increases, the current flowing through the rotating electric machine increases, which increases the voltage generated in the rotating electric machine and also increases the modulation factor. As shown in FIG. 8, the tendency of the eddy current loss of the permanent magnet changes when the modulation factor reaches 0.6. The line for a modulation rate of 0.6 in the characteristics of rotation speed and torque is shown by a broken line in FIG.

[0040] In FIG. 10 , the modulation factor is defined as 1 on the maximum output line where the maximum output is obtained, and therefore the line where the modulation factor is 0.6 is located on the lower rotation speed side than the maximum output line. Note that the maximum output can be improved by setting the modulation factor to 1 or more. In the driving device for a rotating electric machine of this embodiment, the current amplitude and current advance angle are controlled so that the modulation factor becomes smaller in the operating region of the rotation speed and torque where the modulation factor is smaller than 0.6 shown in FIG. 10 , and the current amplitude and current advance angle are controlled so that the modulation factor becomes larger in the operating region of the rotation speed and torque where the modulation factor is larger than 0.6. Therefore, the driving device for a rotating electric machine of this embodiment is applicable not only to operating points with a specific rotation speed and torque but also to operating points with a wide range of rotation speeds and torques, and is capable of reducing eddy current loss in the permanent magnets at a wide range of operating points.

[0041] FIG. 11 is a diagram showing the control of the current amplitude and current advance angle when the modulation factor is reduced in this embodiment. FIG. 12 is a diagram showing the control of the current amplitude and current advance angle when the modulation factor is increased in this embodiment. In FIGS. 11 and 12, the solid lines indicate the current amplitude at which the same torque is obtained for each current advance angle. In normal control of a rotating electric machine, the current advance angle is used in a range equal to or greater than the current advance angle at which the current amplitude required to obtain the same torque is minimized. In other words, increasing the current advance angle alleviates magnetic saturation and reduces iron loss in the rotating electric machine, so the current advance angle is used in a range equal to or greater than the current advance angle at which the current amplitude required to obtain the same torque is minimized. Here, increasing the current advance angle has the effect of weakening the magnetic flux generated by the permanent magnet.

[0042] Because the phase voltage peak value of a rotating electric machine depends on the product of the magnetic flux and rotational angular velocity of the rotating electric machine, increasing the current advance angle reduces the magnetic flux of the rotating electric machine, thereby reducing the phase voltage peak value of the rotating electric machine, and therefore the modulation factor decreases. On the other hand, decreasing the current advance angle increases the magnetic flux of the rotating electric machine, thereby increasing the phase voltage peak value of the rotating electric machine, and therefore the modulation factor increases. Therefore, to reduce the modulation factor while maintaining the same torque, it is sufficient to control the current amplitude and current advance angle to increase, as shown in FIG. 11. On the other hand, to increase the modulation factor while maintaining the same torque, it is sufficient to control the current amplitude and current advance angle to decrease, as shown in FIG. 12.

[0043] FIG. 13 is a flowchart illustrating a driving method for the driving device for a rotating electric machine according to this embodiment. In step S01, the control unit 5 of the driving device 1 determines whether the temperature of the permanent magnet input from the temperature detection unit 80 is higher than a first threshold temperature. The first threshold temperature is set to a temperature lower than the temperature at which demagnetization of the permanent magnet occurs. The coercive force, which indicates the demagnetization resistance of a permanent magnet, differs depending on the magnetic material, so the first threshold temperature is set individually for each magnetic material. For example, if the permanent magnet is a neodymium magnet, the Curie temperature is approximately 300°C. However, in a rotating electric machine, a magnetic field opposite to the magnetization direction is applied to the permanent magnet, so demagnetization occurs at approximately 200°C. Since the first threshold temperature is set to a temperature lower than the temperature at which demagnetization occurs, for example, the first threshold temperature is set to 150°C for a neodymium magnet. If it is determined in step S01 that the temperature of the permanent magnet is equal to or lower than the first threshold temperature (NO), the control unit 5 proceeds to step S02 and drives the rotating electric machine under normal control. Here, normal control refers to, for example, a method of controlling the current amplitude and current advance angle so as to maximize the overall efficiency of the power conversion circuit and the rotating electric machine. Furthermore, if a speed reducer (not shown) is connected to the rotating electric machine, normal control also includes a method of controlling the current amplitude and current advance angle so as to maximize the overall efficiency of the power conversion circuit, the rotating electric machine, and the speed reducer. The output shaft of the rotating electric machine is connected to the input shaft of the speed reducer, and amplified torque and reduced rotation speed are output from the output shaft of the speed reducer based on the reduction ratio. The input and output shafts of the speed reducer may be coaxial or parallel.

[0044] If it is determined in step S01 that the temperature of the permanent magnet is higher than the first threshold temperature (YES), the control unit 5 proceeds to step S03. In step S03, the control unit 5 determines whether the modulation rate is lower than the threshold. If it is determined in step S03 that the modulation rate is lower than the threshold (YES), the control unit 5 proceeds to step S04, where it controls the current amplitude and current control to increase. If it is determined in step S03 that the modulation rate is equal to or higher than the threshold (NO), the control unit 5 proceeds to step S05, where it controls the current amplitude and current control to decrease.

[0045] Here, the control of the current amplitude and the current advance angle in steps S02, S04, and S05 is specifically performed by storing individual current command maps corresponding to steps S02, S04, and S05 in the current command generating unit 51 of the control unit 5, and generating the d-axis current command value I d * and the q-axis current command value I q * Generate.

[0046] The driving device for a rotating electric machine according to this embodiment is a driving device for a rotating electric machine having a stator with three or more phase stator windings and a rotor with permanent magnets, and includes a power conversion circuit that converts DC power input from a power source and outputs phase currents to the stator windings, and a control unit that controls the power conversion circuit. A threshold value is set in advance for the modulation factor when the phase voltage peak value relative to the voltage of the DC power is defined as the modulation factor. The control unit decreases the current amplitude and current advance angle of the phase currents output from the power conversion circuit when the temperature of the permanent magnets is higher than a predetermined first threshold temperature and the modulation factor is greater than the threshold value, and increases the current amplitude and current advance angle of the phase currents output from the power conversion circuit when the temperature of the permanent magnets is higher than the predetermined first threshold temperature and the modulation factor is smaller than the threshold value. The driving device for a rotating electric machine configured in this way can suppress temperature rise of the permanent magnets while maintaining torque. Furthermore, suppressing temperature rise of the permanent magnets makes it possible to reduce the content of rare earth elements such as dysprosium and terbium that are added to the permanent magnets to prevent demagnetization at high temperatures, thereby reducing the cost of the rotating electric machine.

[0047] Embodiment 2 The driving device for a rotating electric machine according to the second embodiment is the driving device described in the first embodiment, in which the temperature of the stator winding of the rotating electric machine is input to the control unit. When the temperature of the stator winding rises, the withstand voltage decreases due to damage to the insulating coating, and the efficiency of the rotating electric machine decreases due to heat loss (copper loss). Therefore, it is necessary to suppress the temperature rise of the stator winding as well.

[0048] The configuration of the rotating electric machine drive device 1 of this embodiment is the same as the configuration of the rotating electric machine drive device shown in FIG. 1 of the first embodiment. However, the temperature detection unit 80 can detect the temperature of the stator winding in addition to the temperature of the permanent magnet. The temperature of the stator winding can be detected using a temperature detector such as a thermistor or a thermocouple. The temperature of the stator winding may also be calculated by thermal calculation using a thermal circuit and the loss of the rotating electric machine without using a temperature detector.

[0049] 14 is a block diagram of a control unit according to this embodiment. As shown in FIG. 14, the control unit 5 of this embodiment is composed of a current command generating unit 51, a three-phase to two-phase converting unit 52, a current control unit 53, a two-phase to three-phase converting unit 54, and a PWM signal generating unit 55, similar to the control unit of the first embodiment. The current command generating unit 51 receives a torque command T rq * and the temperature T of the stator winding output from the temperature detection unit 80. col and the permanent magnet temperature T mag The current command generating unit 51 receives the d-axis current command value I d * and the q-axis current command value I q * Generate.

[0050] FIG. 15 is a flowchart showing a driving method for the driving device for a rotating electric machine according to this embodiment. In step S11, the control unit 5 of the driving device 1 determines whether the temperature of the stator winding input from the temperature detection unit 80 is higher than a second threshold temperature. The second threshold temperature is set based on the heat resistance temperature of the magnet wire used as the stator winding. The heat resistance temperature of the magnet wire depends on the heat resistance temperature of the insulating coating of the magnet wire. For example, if the insulating coating of the magnet wire is made of polyamideimide, the heat resistance temperature is approximately 200°C, so the second threshold temperature is set to, for example, 150°C. If it is determined in step S11 that the temperature of the stator winding is higher than the second threshold temperature (YES), the control unit 5 proceeds to step S12 and drives the rotating electric machine using minimum current control.

[0051] If it is determined in step S11 that the temperature of the stator winding is equal to or lower than the second threshold temperature (NO), the control unit 5 proceeds to step S13. In step S13, the control unit 5 determines whether the temperature of the permanent magnet is higher than the first threshold temperature. If it is determined in step S13 that the temperature of the permanent magnet is higher than the first threshold temperature (YES), the control unit 5 proceeds to step S14 and drives the rotating electric machine using magnet loss reduction control. If it is determined in step S13 that the temperature of the permanent magnet is equal to or lower than the first threshold temperature (NO), the control unit 5 proceeds to step S15 and drives the rotating electric machine using maximum efficiency control.

[0052] Here, the minimum current control, magnet loss reduction control, and maximum efficiency control will be described. The current command generation unit 51 of the control unit 5 stores individual current command maps corresponding to the respective controls, and the current command generation unit 51 generates a d-axis current command value I d * and the q-axis current command value I q *The individual current command maps corresponding to each control can be obtained by comprehensively analyzing the current amplitude and current lead angle using the finite element method (FEM: Field Element Method) analysis. Note that the current command map can also be obtained comprehensively by actually measuring the current amplitude and current lead angle without using FEM analysis.

[0053] The minimum current control is based on a minimum current command map that minimizes the current per torque. The minimum current command map for the minimum current control is a current command map that selects, through FEM analysis, a combination of current amplitude and current advance angle that minimizes the amplitude of the current supplied to the rotating electric machine to obtain the same torque. The maximum efficiency control is based on an efficiency-maximizing current command map that maximizes the efficiency of the rotating electric machine. The efficiency-maximizing current command map for the maximum efficiency control is a current command map that calculates the loss generated in the rotating electric machine through FEM analysis and selects a combination of current amplitude and current advance angle that maximizes the efficiency of the rotating electric machine. The magnet loss reduction control is based on a current command map that reduces the loss generated in the permanent magnet more than the maximum efficiency control. The magnet loss reduction control current command map is a current command map that calculates the modulation factor through FEM analysis and selects a combination of current amplitude and current advance angle that corresponds to the modulation factor that minimizes the loss of the permanent magnet. In other words, step S14 of the magnet loss reduction control corresponds to steps S03 to S05 in the first embodiment shown in FIG. 13.

[0054] In the driving device for a rotating electric machine according to this embodiment, minimum current control is performed when the temperature of the stator winding is higher than the second threshold temperature. By performing minimum current control, it is possible to minimize copper loss in the stator winding, thereby suppressing temperature increases in the stator winding. On the other hand, when the temperature of the stator winding is equal to or lower than the second threshold temperature, the process proceeds to a conditional branch that determines whether the temperature of the permanent magnet is higher than the first threshold temperature. When the temperature of the permanent magnet is higher than the first threshold temperature, magnet loss reduction control is performed. The magnet loss reduction control is a control method from steps S03 to S05 described in the first embodiment, and controls the current amplitude and current advance angle according to the modulation factor to reduce eddy currents in the magnet, thereby suppressing temperature increases of the permanent magnet while maintaining torque. When the temperature of the permanent magnet is equal to or lower than the first threshold temperature, maximum efficiency control is performed. In the driving device for a rotating electric machine according to this embodiment, the flowchart shown in FIG. 15 is performed at regular time intervals as the rotating electric machine is driven. Therefore, minimum current control, magnet loss reduction control, and maximum efficiency control are switched as needed in response to the temperatures of the stator winding and the permanent magnet.

[0055] FIG. 16 is a schematic diagram showing the control of the current amplitude and current advance angle when the modulation factor is reduced when transitioning from maximum efficiency control to magnet loss reduction control in the driving device for a rotating electric machine according to this embodiment. FIG. 17 is a schematic diagram showing the control of the current amplitude and current advance angle when the modulation factor is increased when transitioning from maximum efficiency control to magnet loss reduction control. The current advance angle under maximum efficiency control is larger than the current advance angle under minimum current control, which minimizes the current amplitude to obtain the same torque. Increasing the current advance angle reduces the magnetic flux generated in the permanent magnet, alleviating magnetic saturation and reducing the magnetic flux density of the rotating electric machine, thereby reducing iron loss. Therefore, the current advance angle under maximum efficiency control is larger than the current advance angle under minimum current control. Note that while FIGS. 16 and 17 show the relationship between the current amplitude and current advance angle under maximum efficiency control, magnet loss reduction control, and minimum current control as dots, the actual relationship between the current amplitude and current advance angle varies over a certain range.

[0056] When the current advance angle is increased, the magnetic flux of the rotating electric machine decreases, and the peak value of the phase voltage of the rotating electric machine decreases, resulting in a decrease in the modulation factor. When the current advance angle is decreased, the magnetic flux of the rotating electric machine increases, and the peak value of the phase voltage of the rotating electric machine increases, resulting in an increase in the modulation factor. Therefore, if the modulation factor needs to be reduced when transitioning from maximum efficiency control to magnet loss reduction control, it is sufficient to control the current amplitude and current advance angle to be increased, as shown in FIG. 16. On the other hand, if the modulation factor needs to be increased when transitioning from maximum efficiency control to magnet loss reduction control, it is sufficient to control the current amplitude and current advance angle to be decreased, as shown in FIG. 17.

[0057] FIG. 18 is a characteristic diagram showing the change in permanent magnet temperature due to switching from maximum efficiency control to magnet loss reduction control in the driving device for a rotating electric machine of this embodiment. In FIG. 18, the horizontal axis represents time and the vertical axis represents the temperature of the permanent magnet. FIG. 18 shows the change in temperature of the permanent magnet when switching to magnet loss reduction control is performed when the temperature of the permanent magnet reaches the first threshold temperature after maximum efficiency control has started. In FIG. 18, the solid line after control switching indicates the temperature of the permanent magnet when switching from maximum efficiency control to magnet loss reduction control is performed. For comparison, the dashed line after control switching in FIG. 18 indicates the temperature of the permanent magnet when maximum efficiency control is continued without switching from maximum efficiency control to magnet loss reduction control.

[0058] As shown in FIG. 18 , if the rotating electric machine is started to operate under maximum efficiency control and the maximum efficiency control is continued even after the temperature of the permanent magnet reaches the first threshold temperature, the temperature of the permanent magnet exceeds the continuous drivability temperature. As a result, demagnetization occurs in the permanent magnet, reducing the torque of the rotating electric machine and making continuous operation difficult. In contrast, in the driving device for the rotating electric machine according to this embodiment, when the temperature of the permanent magnet reaches the first threshold temperature, the control switches from maximum efficiency control to magnet loss reduction control, thereby slowing the temperature rise of the permanent magnet. Therefore, the temperature of the permanent magnet does not exceed the continuous drivability temperature, allowing continuous operation. Thus, in the driving device for the rotating electric machine according to this embodiment, high-efficiency control is possible until the temperature of the permanent magnet reaches the first threshold temperature. After the temperature of the permanent magnet reaches the first threshold temperature, magnet loss reduction control can be used to extend the continuous operation time. Rotating electric machines used in electric vehicles, etc., are required to achieve both high-efficiency operation that improves power consumption and long-term continuous operation over a wide range of torque and rotation speed. The driving device for the rotating electric machine according to this embodiment can achieve both high-efficiency driving and an extended continuous driving time over a wide range of torque and rotation speed.

[0059] Embodiment 3 The driving device for a rotating electric machine according to embodiment 3 is similar to the driving device described in embodiment 1. In the driving device for a rotating electric machine according to this embodiment, the carrier frequency is limited, thereby making it possible to further improve the effect of reducing eddy current loss in the permanent magnets.

[0060] FIG. 19 shows the relationship between the modulation factor and the DC bus voltage V pn 19 is a characteristic diagram showing the relationship between the DC bus voltage V pn 2f for c ±f and 4f c As explained in the first embodiment, the amplitude of the harmonic voltage is 2f ±f. c ±f is dominant, but 4f c The ±f component also becomes larger in the range where the modulation rate is small. cTo reduce the eddy current loss of the permanent magnet for the modulation rate based only on the ±f component, 4f c The eddy current loss caused by the ±f component should be removed.

[0061] The eddy current loss of a permanent magnet depends on the carrier frequency and the thickness of the permanent magnet in the magnetization direction. Here, the high frequency components of the eddy current generated in the permanent magnet are concentrated only on the surface of the permanent magnet due to the skin effect, so by setting a carrier frequency determined according to the skin depth, it is possible to remove the high frequency components of the eddy current of the permanent magnet. When the frequency of the harmonic components of the magnetic flux generated from the stator winding of a rotating electric machine is 4f c ±f, the frequency at which the eddy current generated in the permanent magnet is significantly increased is 8f c The eddy current loss of the permanent magnet is 8f c The components are at 4f, the harmonic frequency of the magnetic flux. c +f and 4f c -f, which is the harmonic component contained in the square wave phase voltage. c The ±f component causes the 8f harmonic component of the eddy current loss of the permanent magnet. c The eddy current loss of the permanent magnet is 8f. c By setting the carrier frequency, which is determined according to the thickness in the magnetization direction of the permanent magnet and the skin depth, so that the eddy current loss of the permanent magnet can be removed, the effect of reducing the eddy current loss of the permanent magnet can be further obtained.

[0062] FIG. 20 shows the relationship between the eddy current loss of the permanent magnet and the thickness of the permanent magnet in the driving device for the rotating electric machine of this embodiment. c This figure shows the carrier frequency required to remove the component. c (unit: Hz), the thickness of the permanent magnet in the magnetization direction is W (unit: m), and the relative permeability of the permanent magnet is μ r The conductivity of the permanent magnet is σ (unit: S / m) and the vacuum permeability is μ0. The eddy current loss of the permanent magnet is 8f c To remove the component, the carrier frequency f c is determined so as to satisfy the following equation (1).

[0063] fc > 8 / (π×μ r ×μ0×σ×W 2 ) (1)

[0064] The line shown in Fig. 20 indicates the carrier frequency calculated on the right side of equation (1). In other words, by setting the carrier frequency higher than the line shown in Fig. 20, the eddy current loss of the permanent magnet can be reduced by 8f c It is possible to remove the eddy current loss of the permanent magnet. c When the component is removed, the eddy current loss in the permanent magnet is 2f of the square wave phase voltage c The eddy current loss due to the ±f component becomes dominant, making it easy to control the current amplitude and current advance angle according to the modulation factor. c By removing the component, it becomes possible to more effectively reduce the eddy current loss of the permanent magnet.

[0065] In the driving device for a rotating electric machine according to this embodiment, if silicon carbide (SiC) semiconductor switching elements are used as the switching elements constituting the power conversion circuit, it becomes possible to set the carrier frequency higher. Therefore, it becomes possible to obtain a more significant effect of reducing eddy current loss in the permanent magnets by controlling the current amplitude and current advance angle according to the modulation rate. It is also possible to apply a multilevel inverter to the power conversion circuit of the driving device for a rotating electric machine according to this embodiment. When a multilevel inverter is used in the power conversion circuit, harmonic components due to the carrier frequency are generated in the rectangular wave phase voltage according to the modulation rate. Therefore, by controlling the current amplitude and current advance angle according to the modulation rate, it becomes possible to suppress temperature rise in the permanent magnets.

[0066] The rotating electric machines described above may be cooled by a water-cooling system, in which the rotating electric machine is cooled with water, or an oil-cooling system, in which the rotating electric machine is cooled with oil. In a water-cooling system, the rotating electric machine is cooled by providing a water channel in a frame that fixes the stator of the rotating electric machine, resulting in a small cooling effect on the rotor's permanent magnets. In an oil-cooling system, the rotating electric machine is cooled by directly spraying oil onto the rotating electric machine, which allows for direct cooling of the rotor's permanent magnets. However, the oil is only sprayed onto the surface of the permanent magnets and does not penetrate to the axial center, resulting in temperature variations in the permanent magnets. By applying the drive devices for the rotating electric machines described in the first to third embodiments, it is possible to suppress temperature increases in the rotor's permanent magnets in both water-cooled and oil-cooled rotating electric machines.

[0067] The drive devices for the rotating electric machine described in the first to third embodiments can also be applied to vehicle drive devices for electric vehicles. When applied as a vehicle drive device, torque reduction due to prevention of demagnetization of the permanent magnets of the rotating electric machine does not occur, so it is possible to achieve continuous drive without reducing the acceleration of the vehicle.

[0068] The control unit 5 is configured with a processor 100 and a storage device 101, as shown in FIG. 21 , which illustrates an example of hardware. The storage device includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory, although not shown. Alternatively, a hard disk auxiliary storage device may be used instead of the flash memory. The processor 100 executes a program input from the storage device 101. In this case, the program is input to the processor 100 from the auxiliary storage device via the volatile storage device. The processor 100 may output data such as calculation results to the volatile storage device of the storage device 101, or may store the data in the auxiliary storage device via the volatile storage device.

[0069] Although the present application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are conceivable within the scope of the technology disclosed in the present specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment.

[0070] Various aspects of the present disclosure are summarized below as appendices.

[0071] (Appendix 1) A driving device for a rotating electric machine having a stator with three or more phases of stator windings and a rotor with a permanent magnet, a power conversion circuit that converts DC power input from a power source and outputs a phase current to the stator winding; and a control unit that controls the power conversion circuit, a threshold value is set in advance for a modulation factor when a phase voltage peak value with respect to the voltage of the DC power is set as the modulation factor; the control unit reduces the current amplitude and current advance angle of the phase current output from the power conversion circuit when the temperature of the permanent magnet is higher than a predetermined first threshold temperature and the modulation rate is larger than the threshold, and increases the current amplitude and current advance angle of the phase current output from the power conversion circuit when the temperature of the permanent magnet is higher than the first threshold temperature and the modulation rate is smaller than the threshold. (Appendix 2) 2. The driving device for a rotating electric machine according to claim 1, wherein the predetermined threshold value for the modulation factor is 0.6. (Appendix 3) The control unit stores an efficiency maximum current command map that maximizes the efficiency of the rotating electric machine and a minimum current command map that minimizes the current per torque of the rotating electric machine, and controls the rotating electric machine based on the minimum current command map when the temperature of the stator winding is higher than a predetermined second threshold temperature, and controls the rotating electric machine based on the efficiency maximum current command map when the temperature of the stator winding is equal to or lower than the second threshold temperature and the temperature of the permanent magnet is equal to or lower than the first threshold temperature. (Appendix 4) The control unit controls the power conversion circuit at a carrier frequency of f c (unit: Hz), the thickness of the permanent magnet in the magnetization direction is W (unit: m), and the relative permeability of the permanent magnet is μ r When the conductivity of the permanent magnet is σ (unit: S / m) and the vacuum permeability is μ0, the carrier frequency is f c > 8 / (π×μ r ×μ0×σ×W 2 ) 4. The driving device for a rotating electric machine according to claim 1, wherein the above is satisfied. (Appendix 5) 5. The driving device for a rotating electric machine according to any one of claims 1 to 4, wherein the power conversion circuit is an inverter circuit in which six semiconductor switching elements using silicon carbide are connected in a full bridge configuration. (Appendix 6) The rotating electric machine is characterized in that the rotating electric machine has a plurality of the permanent magnets arranged in two or more layers in a V shape facing outward in the circumferential direction to form one magnetic pole. (Appendix 7) A method for driving a rotating electric machine having a stator with three or more phase stator windings and a rotor with permanent magnets, the method converting DC power input from a power source and outputting phase currents to the stator windings, comprising: a threshold value is set in advance for a modulation factor when a phase voltage peak value with respect to the voltage of the DC power is set as the modulation factor; a current amplitude and a current advance angle of the phase current are decreased when the temperature of the permanent magnet is higher than a predetermined first threshold temperature and the modulation rate is larger than the threshold temperature, and the current amplitude and the current advance angle of the phase current are increased when the temperature of the permanent magnet is higher than the first threshold temperature and the modulation rate is smaller than the threshold temperature. [Explanation of symbols]

[0072] 1 drive device, 1a, 1b DC bus, 2 capacitor, 2a AC bus, 3 power conversion circuit, 4 current detection unit, 4a shunt resistor, 5 control unit, 6 voltage detection unit, 10 rotating electric machine, 11 input terminal, 12 output terminal, 20 stator, 21 stator core, 22 stator winding, 23 core back, 24 teeth, 31 to 36 switching elements, 40 rotor, 41 rotor core, 42 permanent magnet, 43 magnet insertion hole, 50 rotating shaft, 51 current command generation unit, 52 three-phase to two-phase conversion unit, 53 current control unit, 54 two-phase to three-phase conversion unit, 55 PWM signal generation unit, 60 rotation angle sensor, 70 power switch, 80 temperature detection unit, 90 DC power supply, 100 processor, 101 storage device.

Claims

1. A driving device for a rotating electric machine having a stator with three or more phases of stator windings and a rotor with a permanent magnet, a power conversion circuit that converts DC power input from a power source and outputs a phase current to the stator winding; and a control unit that controls the power conversion circuit, a threshold value is set in advance for a modulation factor when a phase voltage peak value with respect to the voltage of the DC power is set as the modulation factor; the control unit reduces the current amplitude and current advance angle of the phase current output from the power conversion circuit when the temperature of the permanent magnet is higher than a predetermined first threshold temperature and the modulation rate is larger than the threshold, and increases the current amplitude and current advance angle of the phase current output from the power conversion circuit when the temperature of the permanent magnet is higher than the first threshold temperature and the modulation rate is smaller than the threshold.

2. 2. The driving device for a rotating electric machine according to claim 1, wherein the predetermined threshold value for the modulation factor is 0.

6.

3. 3. The driving device for a rotating electric machine according to claim 1, wherein the control unit stores an efficiency maximum current command map that maximizes the efficiency of the rotating electric machine and a minimum current command map that minimizes the current per torque of the rotating electric machine, and controls the rotating electric machine based on the minimum current command map when the temperature of the stator winding is higher than a predetermined second threshold temperature, and controls the rotating electric machine based on the efficiency maximum current command map when the temperature of the stator winding is equal to or lower than the second threshold temperature and the temperature of the permanent magnet is equal to or lower than the first threshold temperature.

4. The control unit controls the power conversion circuit at a carrier frequency of f ｃ (unit: Hz), the thickness of the permanent magnet in the magnetization direction is W (unit: m), and the relative permeability of the permanent magnet is μ ｒ , the conductivity of the permanent magnet is σ (unit: S / m), and the vacuum permeability is μ ０ Then, the carrier frequency is f ｃ > 8 / (π×μ ｒ ×μ ０ ×σ×W ２ ) 3. The driving device for a rotating electric machine according to claim 1, wherein the following is satisfied:

5. 3. The driving device for a rotating electric machine according to claim 1, wherein the power conversion circuit is an inverter circuit in which six semiconductor switching elements made of silicon carbide are connected in a full bridge configuration.

6. The rotating electric machine drive device according to claim 1 or 2, characterized in that the rotating electric machine has a plurality of the permanent magnets arranged in two or more layers in a V shape facing outward in the circumferential direction to form one magnetic pole.

7. A method for driving a rotating electric machine having a stator with three or more phase stator windings and a rotor with permanent magnets, the method converting DC power input from a power source and outputting phase currents to the stator windings, comprising: a threshold value is set in advance for a modulation factor when a phase voltage peak value with respect to the voltage of the DC power is set as the modulation factor; a current amplitude and a current advance angle of the phase current are decreased when the temperature of the permanent magnet is higher than a predetermined first threshold temperature and the modulation rate is larger than the threshold temperature, and the current amplitude and the current advance angle of the phase current are increased when the temperature of the permanent magnet is higher than the first threshold temperature and the modulation rate is smaller than the threshold temperature.

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