Motor control method and motor control device

Abstract

According to the present invention, when there is, in a second coordinate space having the rotation speed and the torque of a motor 009 as the coordinate axes, a specific region 113 in which the temperature of a magnet of the motor 009 is higher than the temperature of a coil of the motor 009 and the temperature difference between the magnet and the coil is equal to or higher than a prescribed value, when temperature characteristics, in which the temperature difference between the magnet and the coil becomes smaller as the distance from an efficient operation line 114 increases, are exhibited in a first coordinate space, and furthermore when a coordinate position indicating a rotation speed N and a torque instruction value T* in the second coordinate space is included in the specific region 113, then a motion point 116 is moved to a retreating position 117 which is on an equal torque line 115 coinciding the motion point 116 and which is distanced from the efficient operation line 114.

Description

[Technical Field]

[0001] The present invention relates to a motor control method and a motor control device. [Background technology]

[0002] JP2019-134630A discloses a technology for generating a d-axis current command value and a q-axis current command value based on a torque command value, and setting the d-axis current command value and the q-axis current command value so that they overlap with an efficient operation line, which is the locus of the d-axis current and the q-axis current that maximizes the output efficiency of the motor torque in a coordinate space whose coordinate axes are the d-axis current and the q-axis current. Summary of the Invention

[0003] However, in a permanent magnet embedded motor with a small number of axial divisions of the magnet, when the voltage of the DC power supply that supplies power to the motor via an inverter becomes high, the carrier loss that occurs in the magnet increases, causing a phenomenon in which the temperature of the magnet becomes significantly higher than the temperature of the motor's coil in a specific rotation speed / torque range. Therefore, when attempting to protect the magnet from heat based on the coil temperature, it is necessary to set the upper coil temperature limit lower by the amount of the temperature difference between the magnet and coil that occurs due to this phenomenon, which causes a problem of a corresponding decrease in the motor's continuous performance (maximum torque-rotation speed characteristics in the range where torque is not limited).

[0004] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a motor control method and a motor control device that provide heat protection for the motor magnet based on the coil temperature and reduce degradation of the motor's continuous performance.

[0005] According to one aspect of the present invention, there is provided a motor control method for generating d-axis and q-axis current command values ​​for controlling an interior permanent magnet motor based on a torque command value, and generating the d-axis and q-axis current command values ​​in a first coordinate space having the d-axis and q-axis currents as coordinate axes so that the operating point of the d-axis and q-axis current command values ​​overlaps with an efficient operation line that represents the locus of the d-axis and q-axis currents at which the motor's torque output efficiency is maximized. In this control method, when a specific region exists in a second coordinate space having the motor's rotation speed and torque as coordinate axes, where the temperature of the motor's magnet is higher than the temperature of the motor's coil and the temperature difference between the magnet and the coil is equal to or greater than a predetermined value, and the first coordinate space has a temperature characteristic in which the temperature difference between the magnet and the coil decreases with increasing distance from the efficient operation line, and when a coordinate position in the second coordinate space that represents the rotation speed and the torque command value is included in the specific region, the operating point is moved to a retracted position on the iso-torque line that overlaps with the operating point and is away from the efficient operation line. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram of a motor control device to which the motor control method of this embodiment is applied. [Figure 2] FIG. 2 is a diagram for explaining eddy current loss that occurs in a magnet embedded in a rotor of a motor. [Figure 3] FIG. 3 is a diagram showing the relationship between the battery voltage and the carrier loss appearing in the three-phase current when the three-phase current is output from the battery to the motor via the inverter. [Figure 4] FIG. 4 is a diagram showing the distribution of the temperature difference obtained by subtracting the coil temperature from the magnet temperature when the battery voltage is low, in a coordinate space with the rotation speed and torque as coordinate axes, and the heat resistance upper limit line indicating the torque that converges to the magnet's heat resistance upper limit temperature when the battery voltage is low. [Figure 5] FIG. 5 is a diagram showing the transition of the coil temperature and the magnet temperature over time when the battery voltage is low and torque limitation is performed on the motor based on the coil temperature. [Figure 6]Figure 6 is a diagram showing, in a coordinate space with rotation speed and torque as coordinate axes, the distribution of the temperature difference obtained by subtracting the coil temperature from the magnet temperature when the battery voltage is high, a heat resistance upper limit line indicating the torque that converges to the magnet's heat resistance upper limit temperature, and a specific region that appears when the battery voltage is high, which includes the boundary of the heat resistance upper limit line and a region where the torque is higher than the heat resistance upper limit line, and where the temperature difference obtained by subtracting the coil temperature from the magnet temperature is equal to or greater than a predetermined temperature difference. [Figure 7] FIG. 7 is a diagram showing the transition of the coil temperature and the magnet temperature over time when the battery voltage is high and torque limitation is performed on the motor based on the coil temperature. [Figure 8] FIG. 8 is a diagram showing the continuous performance of the motor (maximum allowable torque-speed characteristics within the range where torque is not limited), and shows continuous performance curve A (dashed line) when the battery voltage is low, continuous performance curve B (dashed line) when the battery voltage is high and torque is limited by setting the upper coil temperature limit without considering the specific region (FIG. 6), and continuous performance curve C (solid line) when the battery voltage is high and the upper coil temperature limit is lowered to effectively limit torque even when the rotation speed and torque command value are within the specific region (FIG. 6). [Figure 9] Figure 9 shows, in a coordinate space with the d-axis current and q-axis current as coordinate axes, the efficient operation line that represents the locus of the d-axis current and q-axis current at which the motor's torque output efficiency is maximized, the equal torque line where the torque is constant, and the distribution of the temperature difference obtained by subtracting the coil temperature from the magnet temperature when the battery voltage is high. [Figure 10]FIG. 10 is a diagram showing the continuous performance of the motor (maximum allowable torque-rotation speed characteristics within a range where torque is not limited), and shows a continuous performance curve E (broken line) when the coil upper limit temperature is lowered to effectively limit torque even when the battery voltage is high and the rotation speed and torque command value are within the specific region (FIG. 6), and a continuous performance curve F (solid line) when the d-axis current command value and q-axis current command value are changed as shown in FIG. 9 when the battery voltage is high and the rotation speed and torque command value are within the specific region (FIG. 6). [Figure 11] FIG. 11 is a diagram showing a case where the d-axis current command value and the q-axis current command value are gradually changed from time t1 to time t2. [Figure 12] FIG. 12 shows a control flow of the motor control device of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] [Basic configuration of this embodiment] 1 is a schematic diagram of a control device for a motor 009 to which a control method for a motor 009 according to this embodiment is applied. The control device for a motor 009 according to the present invention is applicable to an electric vehicle equipped with an electric motor (motor 009) that functions as part or all of the vehicle's drive source. Electric vehicles include not only electric vehicles, but also hybrid vehicles and fuel cell vehicles.

[0008] The motor 009 is an embedded permanent magnet motor (IPM motor) with a magnet embedded in the rotor. A temperature sensor 011 (thermistor) is attached to the coil wound around the stator of the motor 009.

[0009] The current command value generator 001 generates a torque command value T * , and the d-axis current command value Id based on the DC voltage Vdc of the battery 006 detected by the voltage sensor 007. * , and the q-axis current command value Iq * Calculate.

[0010] The current command value generator 001 also receives the temperature detected by the temperature sensor 011, the rotation speed N of the motor 009, and the torque command value T * Based on this, torque limit (for example, Id * ) 2 +(Iq * ) 2 (suppressing the value of

[0011] Since the magnet is embedded inside the rotor, it is difficult to measure the temperature directly. Therefore, the coil temperature when the magnet temperature is at the heat-resistant upper limit temperature 112 (Figs. 5 and 7) is set as the coil upper limit temperature 111 (Figs. 5 and 7), and torque is limited so that the coil temperature does not exceed the coil upper limit temperature 111 (Figs. 5 and 7).

[0012] The current vector controller 002 calculates the d-axis current command value Id * , q-axis current command value Iq * , and the d-axis voltage command value Vd based on the d-axis current value Id and the q-axis current value Iq calculated by the two-phase converter 011. * , q-axis voltage command value Vq * Calculate.

[0013] The two-phase converter 012 calculates a d-axis current value Id and a q-axis current value Iq based on the output currents iu, iv, and iw from the inverter 005 detected by the current sensor 008 .

[0014] The three-phase converter 003 outputs the d-axis voltage command value Vd * , q-axis voltage command value Vq * , and the three-phase voltage command value (Vu * ,Vv * ,Vw * )

[0015] The PWM converter 004 generates a voltage command value (Vu * ,Vv * ,Vw *) to a PWM signal (Duu * ,Dul * ,Dvu * ,Dvl * ,Dwu * ,Dwl * )

[0016] Inverter 005 generates a PWM signal (Duu * ,Dul * ,Dvu * ,Dvl * ,Dwu * ,Dwl * ) is used to convert the DC voltage Vdc of the battery 006 into three-phase AC voltages Vu, Vv, and Vw, which are output to the motor 009. The motor control device performs current feedback control of the motor 009 with the above configuration.

[0017] The rotation speed calculator 013 calculates the electrical angular velocity ω by differentiating the electrical angle θ with respect to time, and calculates the rotation speed N by N=60ω / (2π·p) using the number of pole pairs p of the motor 009.

[0018] [Eddy current loss and carrier loss] Fig. 2 is a diagram for explaining eddy current loss Pn that occurs in a magnet embedded in the rotor of the motor 009. Fig. 3 is a diagram showing the relationship between the voltage of the battery 006 and the carrier loss that appears in the three-phase current when the three-phase current is output from the battery 006 to the motor 009 via the inverter 005.

[0019] As shown in Figure 2, if a magnet embedded in the rotor of motor 009 with an axial length of L is divided into n pieces in the axial direction of the rotor, the eddy current loss Pn [J / s] generated in the magnet is expressed as the sum of the eddy current losses generated in each divided magnet, as shown in equation (1) below.

[0020]

number

[0021] Here, w is the width of the magnet, d is the thickness of the magnet, B is the density of the magnetic flux passing through the magnet in the thickness direction, f is the carrier frequency of the PWM signal, ρ is the magnetic permeability of the magnet, and K is a constant. In equation (1), as the number of n is made smaller, the value of Pn increases, reaching a maximum when n = 1. Therefore, the fewer the number of divisions in the axial direction of the magnet, the greater the eddy current loss Pn. Also, the higher the carrier frequency, the greater the eddy current loss Pn. This eddy current loss Pn is converted into heat in the magnet, so the greater the eddy current loss Pn, the higher the temperature of the magnet will be compared to the temperature of the coil.

[0022] As shown in Figure 3 (left), when the voltage of the battery 006 that supplies power to the inverter 005 becomes high, the peak value of the high-frequency noise component caused by the PWM signal becomes higher than when the voltage is low (Figure 3 (right)). As this noise component becomes larger, the amplitude of the magnetic flux passing through the magnet also increases, resulting in an increase in the eddy current loss (carrier loss) mentioned above. The magnitude of this magnetic flux is calculated by the time derivative of the noise component (current).

[0023] The carrier loss is weighted relative to the eddy current loss Pn based on the rotation speed N and torque of the motor 009. In addition, from the viewpoint of the controllability and heat generation of the inverter 005, a high carrier frequency is applied in the low-to-medium speed and medium torque range, such as when the vehicle is traveling uphill or on a highway. Therefore, the temperature difference between the magnet and the coil caused by the carrier loss in such a range becomes significant.

[0024] From the above, carrier loss becomes significantly large when the magnet is not divided in the axial direction or the number of divisions in the axial direction of the magnet is small, the carrier frequency is high, the voltage of the battery 006 is high, and the vehicle is traveling in the low to medium speed and medium torque range.

[0025] [Temperature difference distribution between magnet and coil and torque limit in coordinate space with rotation speed N and torque of motor 009 as coordinate axes] Fig. 4 is a diagram showing the distribution of the temperature difference obtained by subtracting the coil temperature from the magnet temperature when the voltage of the battery 006 is low, in a coordinate space (second coordinate space) whose coordinate axes are the rotation speed N and torque, and a heat-resistant upper limit line 110 indicating the torque converging to the magnet's heat-resistant upper limit temperature 112 (Fig. 5) in a case where torque limitation is performed on the motor 009 based on the coil temperature, and when the voltage of the battery 006 is low, the diagram shows the transition of the coil temperature and the magnet temperature over time.

[0026] The inventors of the present application investigated the distribution of the temperature difference obtained by subtracting the temperature of the magnet from the temperature of the coil in a coordinate space with the rotation speed N of the motor 009 on the horizontal axis and the torque on the vertical axis, and obtained the distribution shown in FIG.

[0027] As shown in FIG. 4, the temperature difference distribution has a first region 101 in which the temperature difference obtained by subtracting the magnet temperature from the coil temperature is −40° C. to −30° C. in the region where the rotation speed N is medium and the torque is low.

[0028] The temperature difference distribution includes a second region 102 that is distributed to cover the outer periphery of the first region 101 and has a temperature difference of -30°C to -20°C, a third region 103 that is distributed to cover the outer periphery of the second region 102 and has a temperature difference of -20°C to -10°C, a fourth region 104 that is distributed to cover the outer periphery of the third region 103 and has a temperature difference of -10°C to 0°C, a fifth region 105 that is distributed to cover the outer periphery of the fourth region 104 and has a temperature difference of 0°C to +10°C, a sixth region 106 that is distributed to cover the outer periphery of the fifth region 105 and has a temperature difference of +10°C to +20°C, and a seventh region 107 that is distributed to cover the outer periphery of the sixth region 106 and has a temperature difference of +20°C to +30°C, with the maximum output line 109 as the boundary.

[0029] However, when the voltage of battery 006 is low, for the reasons mentioned above, the losses occurring in the magnet are small, and therefore the areas where the temperature difference is negative (first area 101, second area 102, third area 103, fourth area 104) are smaller than when the voltage of battery 006 is high, as described below.

[0030] Fig. 4 shows a heat resistance upper limit line 110 that represents the trajectory of rotation speed N and torque when the temperature of the magnet converges to its heat resistance upper limit temperature 112 (Fig. 5). Therefore, in the coordinate space shown in Fig. 4, torque limitation is not executed when the output (rotation speed N, torque) of motor 009 is at a position below heat resistance upper limit line 110, but torque limitation is executed when the output exceeds heat resistance upper limit line 110.

[0031] As shown in Figure 4, as the rotation speed goes from high to low, the heat resistance upper limit line 110 passes through the fourth region 104, the fifth region 105, the sixth region 106, the fifth region 105, the fourth region 104, the third region 103, the second region 102, the third region 103, the fourth region 104, the fifth region 105, and the sixth region 106 in that order.

[0032] Figure 5 shows the changes in the temperature of the magnet and the coil over time. The temperature of the magnet rises due to losses generated in the magnet, while the temperature of the coil rises due to the current (torque) flowing through the coil.

[0033] When the voltage of battery 006 is low, heat resistance upper limit line 110 passes through second region 102 as shown in Fig. 4, so for example, coil upper limit temperature 111 is set to a value 30°C lower than heat resistance upper limit temperature 112. As a result, even if the output (rotation speed N, torque) of motor 009 is included in second region 102 above heat resistance upper limit line 110, torque can be limited so that the temperature of the magnet does not exceed heat resistance upper limit temperature 112 as shown in Fig. 5.

[0034] Furthermore, as shown in FIG. 4, the portion where the heat resistance upper limit line 110 passes through the second region 102 is short, and the impact on the heat resistance protection of the magnet is small. Therefore, for example, by setting the coil upper limit temperature 111 to a value 20°C lower than the heat resistance upper limit temperature 112, the continuous performance of the motor 009 can be set to a higher level.

[0035] Figure 6 is a diagram showing, in a coordinate space (second coordinate space) with the rotation speed N and torque as coordinate axes, the distribution of the temperature difference obtained by subtracting the coil temperature from the magnet temperature when the voltage of battery 006 is high, a heat resistance upper limit line 110 indicating the torque converging to the magnet's heat resistance upper limit temperature 112 (Figure 7), and a specific region 113 that appears when the voltage of battery 006 is high, which includes the boundary of the heat resistance upper limit line 110 and an area where the torque is higher than the heat resistance upper limit line 110, and where the temperature difference obtained by subtracting the coil temperature from the magnet temperature is greater than a predetermined temperature difference.

[0036] FIG. 7 is a diagram showing the transition of the coil temperature and the magnet temperature over time when the voltage of the battery 006 is high and torque limitation is performed on the motor 009 based on the coil temperature.

[0037] Figure 6 is similar to Figure 4, but the temperature difference distribution includes an eighth region 108 where the temperature difference obtained by subtracting the coil temperature from the magnet temperature is between -50°C and -40°C in the region where the rotation speed N is medium and the torque is low.

[0038] In addition, the temperature difference distribution includes a first region 101 that is distributed to cover the outer periphery of the eighth region 108 and has a temperature difference of -40°C to -30°C, a second region 102 that is distributed to cover the outer periphery of the first region 101 and has a temperature difference of -30°C to -20°C, and a third region 103 that is distributed to cover the outer periphery of the second region 102 and has a temperature difference of -20°C to -10°C.

[0039] Furthermore, the temperature difference distribution includes a fourth region 104 that is distributed to cover the outer periphery of the third region 103 and is in contact with the maximum output line 109, and has a temperature difference of -10°C to 0°C; a fifth region 105 that is distributed to cover the outer periphery of the fourth region 104 and is in contact with the maximum output line 109, and has a temperature difference of 0°C to +10°C; a sixth region 106 that is distributed to cover the outer periphery of the fifth region 105 and is in contact with the maximum output line 109, and has a temperature difference of +10°C to +20°C; and a seventh region 107 that is distributed to cover the outer periphery of the sixth region 106 and is in contact with the maximum output line 109, and has a temperature difference of +20°C to +30°C.

[0040] When the voltage of battery 006 is high, for the reasons mentioned above, the losses occurring in the magnet become large, and therefore the areas where the temperature difference is negative (8th area 108, 1st area 101, 2nd area 102, 3rd area 103, 4th area 104) become larger than when the voltage of battery 006 is low.

[0041] As shown in Figure 6, as the rotation speed goes from high to low, the heat resistance upper limit line 110 passes through the third region 103, the fourth region 104, the third region 103, the second region 102, the first region 101, the second region 102, the third region 103, the fourth region 104, and the fifth region 105 in that order.

[0042] As in the above, consider a case where the coil upper limit temperature 111 (solid line in Figure 7) is set to a value 30°C (or 20°C) lower than the heat-resistant upper limit temperature 112 (Figure 7), the voltage of the battery 006 is set to a high voltage, and the output (rotation speed N, torque) of the motor 009 is included in the first region 101 above the heat-resistant upper limit line 110. In this case, as shown in Figure 7, the temperature of the magnet exceeds the heat-resistant upper limit temperature 112, and heat protection of the magnet cannot be achieved.

[0043] 7, by setting the coil upper limit temperature 111 (dashed line) to an even lower value, for example, 40°C lower than the heat-resistant upper limit temperature 112, it is possible to limit the torque so that the magnet temperature does not exceed the heat-resistant upper limit temperature 112. However, in this case, as will be described later, the continuous performance of the motor 009 will be reduced, and the motor 009 will not be able to perform at its full potential.

[0044] Therefore, as shown in Figure 6, if there is a specific region 113 on the high torque side of the heat resistance upper limit line 110 within first region 101, and if the coil upper limit temperature 111 is set without considering the specific region 113, the magnet will exceed the heat resistance upper limit temperature 112 when the torque output (rotation speed N, torque) enters the specific region 113, making it difficult to protect the magnet from heat. Also, if the coil upper limit temperature 111 (Figure 7, dashed line) is set low in consideration of the specific region 113, it will be possible to protect the magnet from heat, but the continuous performance of motor 009 will decrease.

[0045] FIG. 8 is a diagram showing the continuous performance of the motor 009 (maximum permissible torque vs. rotation speed characteristics within the range where torque is not limited), and shows a continuous performance curve A (dash line) when the voltage of the battery 006 is low, a continuous performance curve B (dashed line) when the voltage of the DC power supply is high and torque is limited by setting the coil upper limit temperature 111 (FIG. 7) without considering the specific region 113 (FIG. 6), and a continuous performance curve C (dashed line) when the voltage of the DC power supply is high and torque is limited by setting the rotation speed N and torque command value T * 7 shows a continuous performance curve C (solid line) when the coil upper limit temperature 111 (FIG. 7) is lowered to effectively limit the torque even when the torque is included in the specific region 113 (FIG. 6).

[0046] FIG. 8 shows an upper limit line D (solid line) of torque for protecting the magnet from heat when the output (rotation speed N, torque) of the motor 009 is included in the specific region 113 shown in FIG.

[0047] When the voltage of the battery 006 is low (below a predetermined threshold voltage), the carrier loss generated in the magnet is small, so the coil upper limit temperature 111 (Figure 7) can be set without considering the upper limit line D shown in Figure 6, resulting in a continuous performance curve A shown in Figure 8.

[0048] Also, consider the case where carrier loss in the magnet is small even when the voltage of battery 006 is set to a high voltage (above a predetermined threshold voltage), as shown in Figure 8. In this case, there is no need to consider upper limit line D, and continuous performance curve B of motor 009 is improved over continuous performance curve A at low voltage, particularly at high rotation speeds.

[0049] However, in reality, if the voltage of battery 006 is increased, the carrier loss generated in the magnet increases. In this case, it is not possible to set the maximum allowable torque above upper limit line D. Therefore, with conventional technology (JP2019-134630A, etc.), it is necessary to set the coil upper limit temperature 111 (Figure 7) low and shift the continuous performance curve C to the low torque side so that it does not exceed upper limit line D, as shown in Figure 8, and therefore it is not possible to obtain the expected continuous performance.

[0050] [Distribution of temperature difference between magnet and coil in coordinate space with d-axis current and q-axis current as coordinate axes] Figure 9 is a diagram showing an efficient operation line 114 representing the trajectory of the d-axis current and q-axis current at which the torque output efficiency of the motor 009 is maximized, an equal torque line 115 at which the torque is constant, and the distribution of the temperature difference obtained by subtracting the coil temperature from the magnet temperature when the voltage of the battery 006 is high, in a coordinate space (first coordinate space) with the d-axis current and q-axis current as coordinate axes.

[0051] 9 shows an efficient operation line 114, which is the locus of operating points 116 of the d-axis current and the q-axis current at which the torque output efficiency of the motor 009 is maximized (at which the current flowing through the motor 009 is minimized). The efficient operation line 114 varies depending on the DC voltage Vdc of the battery 006. The DC voltage Vdc of the battery 006 also increases as the state of charge (SOC) of the battery 006 increases.

[0052] The constant torque line 115 is a curve that is obtained when the d-axis current and the q-axis current are changed under the condition that the torque is constant. The constant torque line 115 is a curve that intersects the efficient operation line 114 almost perpendicularly.

[0053] When torque is not limited, the current command value generator 001 sets the torque command value T * and the d-axis current command value Id based on the DC voltage Vdc of the battery 006. * and q-axis current command value Iq * The operating point 116 is set at a position overlapping with the efficient operation line 114.

[0054] The inventors of the present application investigated the distribution of the temperature difference obtained by subtracting the temperature of the magnet from the temperature of the coil in a coordinate space (first coordinate space) with the horizontal axis representing the q-axis current and the vertical axis representing the d-axis current, and obtained the distribution shown in Figure 9.

[0055] As shown in Figure 9, the temperature difference distribution has an eighth region 108 where the temperature difference obtained by subtracting the coil temperature from the magnet temperature is -50°C to -40°C in the low region where both the d-axis current and the q-axis current include the origin of the coordinate space.

[0056] In addition, the temperature difference distribution includes a first region 101 that is distributed to cover the outer periphery of the eighth region 108 and has a temperature difference of -40°C to -30°C, a second region 102 that is distributed to cover the outer periphery of the first region 101 and has a temperature difference of -30°C to -20°C, and a third region 103 that is distributed to cover the outer periphery of the second region 102 and has a temperature difference of -20°C to -10°C.

[0057] Furthermore, the temperature difference distribution includes a fourth region 104 that is distributed to cover the outer periphery of the third region 103 and has a temperature difference of -10°C to 0°C, a fifth region 105 that is distributed to cover the outer periphery of the fourth region 104 and has a temperature difference of 0°C to +10°C, a sixth region 106 that is distributed to cover the outer periphery of the fifth region 105 and has a temperature difference of +10°C to +20°C, and a seventh region 107 that is distributed to cover the outer periphery of the sixth region 106 and has a temperature difference of +20°C to +30°C.

[0058] The efficient operation line 114 passes through the eighth region 108, the first region 101, the second region 102, the third region 103, the fourth region 104, and the fifth region 105 in this order from the left side of FIG.

[0059] The eighth region 108 shown in Fig. 9 corresponds to the eighth region 108 shown in Fig. 6. As shown in Fig. 6, the eighth region 108 is in a state where the torque is lower than the heat resistance upper limit line 110 regardless of the rotation speed N. Therefore, the output (rotation speed N, torque) of the motor 009 corresponding to the operating point 116 included in the eighth region 108 is not subject to torque limitation.

[0060] On the other hand, if the output (rotation speed N, torque) of motor 009 corresponds to an operating point 116 included in any of the first region 101, second region 102, third region 103, and fourth region 104, and the output is on the higher torque side than the heat resistance upper limit line 110 shown in Figure 6, then the output is subject to torque limitation.

[0061] In particular, the first region 101 shown in Fig. 9 corresponds to the first region 101 shown in Fig. 6. Therefore, the output (rotation speed N, torque) of the motor 009 corresponding to the operating point 116 included in the first region 101 is included in the specific region 113 shown in Fig. 6.

[0062] Therefore, in this embodiment, the operating point 116 included in the first region 101 is moved to a retreat position 117 on an equal torque line 115 passing through the operating point 116 and included in a region (second region 102 in FIG. 9) where the temperature difference is lower than that of the first region 101. At this time, the q-axis current command value Iq * is decreased, and the d-axis current command value Id* Increase the

[0063] This allows the temperature difference between the magnet and the coil to be reduced without changing the rotation speed N and torque, so that even when the output of motor 009 is within specific region 113 (Figure 6), the same torque limitation can be performed as when the output of motor 009 is within a region other than specific region 113.

[0064] [Continuous performance of Motor 009] FIG. 10 is a diagram showing the continuous performance of the motor 009 (maximum allowable torque within the range not subject to torque limitation vs. rotation speed characteristics), and shows the characteristics when the voltage of the battery 006 is high and the rotation speed N and torque command value T * The continuous performance curve E (dashed line) shows the continuous performance when the coil upper limit temperature 111 (FIG. 7) is lowered to effectively limit the torque even when the voltage of the battery 006 is high and the rotation speed N and torque command value T * is included in the specific region 113 (FIG. 6), the d-axis current command value Id * and q-axis current command value Iq * The continuous performance curve F (solid line) is shown when is changed.

[0065] The continuous performance curve F (broken line) of the motor 009 shown in FIG. 10 is the same as the continuous performance curve C (solid line) of the motor 009 shown in FIG.

[0066] In the continuous performance curve F shown in Fig. 10, the coil upper limit temperature 111 is set higher than in the continuous performance curve E. Specifically, in Fig. 6, the coil upper limit temperature 111 (Fig. 7, solid line) is * Regardless of the coordinate position indicating the d-axis current command value Id, the coil temperature is set to a value that will keep the magnet temperature below the heat-resistant upper limit temperature 112 when torque limitation is executed when the coordinate position is not included in the specific region 113. Therefore, the continuous performance curve F has a higher allowable maximum torque overall than the continuous performance curve E. Also, in the rotation speed region 118 that corresponds to the specific region 113, as described above, the d-axis current command value Id* and q-axis current command value Iq * The operating point 116 of the motor 009 is moved in the direction that reduces the temperature difference between the magnet and the coil. This reduces the temperature difference between the magnet and the coil, protects the magnet from heat, and limits the torque while suppressing a decrease in the continuous performance of the motor 009.

[0067] The reason why the continuous performance curve F is close to the continuous performance curve E in the rotation speed range 118 corresponding to the specific region 113 is that, as described above, the operating point 116 is moved away from the efficient operation line 114 (FIG. 9), which increases the current value supplied to the motor 009, causing the coil temperature to rise accordingly, making it easier to reach the coil upper limit temperature 111 (FIG. 7, solid line).

[0068] [d-axis current command value Id * and q-axis current command value Iq * Time transition of Figure 11 shows the d-axis current command value Id * and q-axis current command value Iq * is gradually changed from time t1 to time t2. * and q-axis current command value Iq * When moving operating point 116 to retract position 117 away from efficient operation line 114 (FIG. 9), it is preferable to move it gradually along constant torque line 115 rather than instantaneously. In FIG. 11, operating point 116 is on efficient operation line 114 until time t1, but after time t1 it starts to move to retract position 117 and reaches retract position 117 at time t2. By gradually moving operating point 116 in this way, it is possible to suppress vibrations that would occur in motor 009 if it were moved instantaneously.

[0069] [Control Flow] FIG. 12 shows a control flow of the control device for the motor 009 of this embodiment.

[0070] In step S1, the current command value generator 001 determines whether the DC voltage Vdc has exceeded a predetermined threshold voltage (become the aforementioned "high voltage"), and if NO, proceeds to step S2, and if YES, proceeds to step S3.

[0071] In step S2, the current command value generator 001 generates a d-axis current command value Id based on the rotation speed N, the torque command value T*, and the DC voltage Vdc. * =Id1 * (N, T * , Vdc) and q-axis current command value Iq * =Iq1 * (N, T * , Vdc) where Id1 * and Iq1 * is a command value that causes an operating point 116 to be on an efficient operation line 114 shown in FIG. 9, and the efficient operation line 114 changes based on, for example, the DC voltage Vdc.

[0072] In step S2, the current command value generator 001 generates a d-axis current command value Id based on the rotation speed N, the torque command value T*, and the DC voltage Vdc. * =Id2 * (N, T * , Vdc) and q-axis current command value Iq * =Iq2 * (N, T * , Vdc) where Id2 * and Iq2 * is a command value that causes the operating point 116 to be on the efficient operation line 114 shown in FIG. 9, and the efficient operation line 114 changes based on, for example, the DC voltage Vdc. However, Id2 * and Iq2 * is the output of motor 009 (rotation speed N, torque command value T * ) is included in the specific region 113 shown in FIG. 6, the retreat position 117 (torque command value T * remains unchanged) becomes the operating point 116. Note that the specific region 113 occurs when the DC voltage Vdc is greater than a predetermined threshold voltage (FIG. 6), and the range of the specific region 113 expands in the rotation speed direction and torque direction as the value of the DC voltage Vdc increases.

[0073] [Effects of this embodiment] According to the control method for the motor 009 of this embodiment, the d-axis current command value Id * and q-axis current command value Iq * Torque command value T * and in a first coordinate space having the d-axis current and the q-axis current as coordinate axes, a d-axis current command value Id * and q-axis current command value Iq * The d-axis current command value Id is set so that the operating point 116 of the motor 009 overlaps with the efficiency operation line 114 that represents the locus of the d-axis current and the q-axis current at which the torque output efficiency of the motor 009 is maximized. * and q-axis current command value Iq * In a second coordinate space having coordinate axes of the rotation speed N and torque of the motor 009, there is a specific region 113 where the temperature of the magnet of the motor 009 is higher than the temperature of the coil of the motor 009 and the temperature difference between the magnet and the coil is equal to or greater than a predetermined value, and the motor has a temperature characteristic where the temperature difference between the magnet and the coil becomes smaller as the motor moves away from an efficient operation line 114 in the first coordinate space, and further, in the second coordinate space, there is a specific region 113 where the temperature of the magnet of the motor 009 is higher than the temperature of the coil of the motor 009 and the temperature difference between the magnet and the coil is equal to or greater than a predetermined value. * When the coordinate position indicating the above is included in the specific region 113, the operating point 116 is moved to a retreat position 117 on the equal torque line 115 overlapping with the operating point 116 and spaced apart from the efficient operation line 114.

[0074] With the above configuration, the rotation speed N and torque command value T * When the coordinate position indicating this is included in the specific region 113, the temperature difference between the magnet and the coil can be reduced by moving the operating point 116 away from the efficient operation line 114, so that the magnet can be protected from heat while suppressing a decrease in the continuous performance of the motor 009.

[0075] In this embodiment, torque limitation is performed by setting the upper limit temperature of the coil (coil upper limit temperature 111) so that the temperature of the magnet does not exceed the heat resistance upper limit temperature 112 of the magnet, and when a specific region 113 exists on the high torque side of the heat resistance upper limit line 110 which represents the trajectory of the rotation speed N and torque when the temperature of the magnet converges to the heat resistance upper limit temperature 112 in the second coordinate space, the upper limit temperature (coil upper limit temperature 111) is set to the temperature of the coil at which the temperature of the magnet will be equal to or lower than the heat resistance upper limit temperature 112 when torque limitation is performed when the coordinate position is not included in the specific region 113, regardless of the coordinate position.

[0076] By the above method, the upper limit temperature (coil upper limit temperature 111) is calculated in the second coordinate space in accordance with the rotation speed N and the torque command value T * When the coordinate position is not included in the specific region 113, the temperature can be set to a high temperature that can be set when torque limitation is performed, and when the coordinate position is included in the specific region 113, the temperature difference between the magnet and the coil can be reduced by moving the operating point 116 away from the efficient operation line 114, so that the magnet can be heat-resistant and protected while suppressing a decrease in the continuous performance of the motor 009.

[0077] In this embodiment, when the voltage of the DC power supply (battery 006) that supplies power to the motor 009 via the inverter 005 exceeds a predetermined threshold voltage (in the case of high voltage), a specific region 113 occurs and the specific region 113 changes based on the magnitude of the voltage of the DC power supply (battery 006).When the voltage of the DC power supply (battery 006) exceeds the threshold voltage (in the case of high voltage) and the coordinate position is included in the specific region 113, the operating point 116 is moved to the evacuation position 117.

[0078] By using the above method, when the voltage of the DC power supply (battery 006) exceeds the threshold voltage, the rotation speed N and the torque command value T * When the coordinate position of the DC power supply (battery 006) is included in a specific region 113 that changes based on the magnitude of the DC power supply (battery 006), the operating point 116 is moved to the retreat position 117. Therefore, even if the voltage of the DC power supply (battery 006) exceeds the threshold voltage, the rotation speed N and the torque command value T* When the coordinate position of the target object is no longer included in the specific area 113, there is no need to move the operating point 116 to the retreat position 117, and therefore the power consumption of the DC power supply (battery 006) can be reduced accordingly.

[0079] In this embodiment, when the operating point 116 is moved from the position where it overlaps with the efficient operation line 114 to the retreat position 117, the d-axis current command value Id * and the q-axis current command value Iq * Reduces.

[0080] By using the above method, the rotation speed N and the torque command value T * Even if the coordinate position is included in the specific area 113, the temperature difference between the magnet and the coil can be effectively reduced.

[0081] In this embodiment, when the operating point 116 is moved from the position where it overlaps with the efficient operation line 114 to the retreat position 117, the d-axis current command value Id * is gradually increased along the constant torque line 115 and the q-axis current command value Iq * is gradually decreased along the constant torque line 115.

[0082] By using the above method, the rotation speed N and the torque command value T * Even if the coordinate position is included in the specific area 113, the temperature difference between the magnet and the coil can be effectively reduced, and vibrations occurring in the motor 009 when the operating point 116 is moved to the retracted position 117 can be suppressed.

[0083] According to the control device for the motor 009 of this embodiment, the d-axis current command value Id * and q-axis current command value Iq * Torque command value T * and a temperature sensor 011 that measures the temperature of the coil of the motor 009, and the current control unit (current command value generator 001) generates a d-axis current command value Id *and q-axis current command value Iq * The d-axis current command value Id is set so that the operating point 116 of the motor 009 overlaps with the efficiency operation line 114 that represents the locus of the d-axis current and the q-axis current at which the torque output efficiency of the motor 009 is maximized. * and q-axis current command value Iq * a specific region 113 exists in which the temperature of the magnet of the motor 009 is higher than the temperature of the coil and the temperature difference between the magnet and the coil is equal to or greater than a predetermined value in a second coordinate space having coordinate axes of the rotation speed N and torque of the motor 009, and the motor 009 has a temperature characteristic in which the temperature difference between the magnet and the coil becomes smaller as the motor moves away from an efficient operation line 114 in the first coordinate space; and further, a specific region 113 exists in which the temperature difference between the magnet and the coil is equal to or greater than a predetermined value in a second coordinate space having coordinate axes of the rotation speed N and torque of the motor 009. * When the coordinate position indicating this is included in the specific region 113, the current control unit (current command value generator 001) moves the operating point 116 to a retreat position 117 on the equal torque line 115 that overlaps with the operating point 116 and is spaced apart from the efficient operation line 114.

[0084] With the above configuration, the rotation speed N and torque command value T * When the coordinate position indicating this is included in the specific region 113, the temperature difference between the magnet and the coil can be reduced by moving the operating point 116 away from the efficient operation line 114, so that the magnet can be protected from heat while suppressing a decrease in the continuous performance of the motor 009.

[0085] In this embodiment, torque limitation is performed by setting the coil upper limit temperature (coil upper limit temperature 111) so that the temperature of the magnet does not exceed the magnet's heat resistance upper limit temperature 112, and when a specific region 113 exists on the high torque side of the heat resistance upper limit line 110 which represents the trajectory of the rotation speed N and torque when the magnet temperature converges to the heat resistance upper limit temperature 112 in the second coordinate space, the current control unit (current command value generator 001) sets the upper limit temperature (coil upper limit temperature 111) to a temperature at which the magnet temperature will be equal to or lower than the heat resistance upper limit temperature 112 when torque limitation is performed when the coordinate position is not included in the specific region 113, regardless of the coordinate position.

[0086] With the above configuration, the upper limit temperature (coil upper limit temperature 111) is calculated based on the rotation speed N and torque command value T * When the coordinate position is not included in the specific region 113, the highest temperature that can be set is set when torque limitation is performed, and when the coordinate position is included in the specific region 113, the operating point 116 is moved away from the efficient operation line 114, thereby reducing the temperature difference between the magnet and the coil, and thereby making it possible to protect the magnet from heat while suppressing a decrease in the continuous performance of the motor 009.

[0087] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate.

Claims

1. A motor control method for controlling an interior permanent magnet motor, which generates a d-axis current command value and a q-axis current command value based on a torque command value, and generates the d-axis current command value and the q-axis current command value in a first coordinate space having the d-axis current and the q-axis current as coordinate axes, so that operating points of the d-axis current command value and the q-axis current command value overlap with an efficiency operation line representing loci of the d-axis current and the q-axis current at which torque output efficiency of the motor is maximized, When a specific region exists in a second coordinate space having coordinate axes of the rotation speed and the torque of the motor where the temperature of the magnet of the motor is higher than the temperature of the coil of the motor and the temperature difference between the magnet and the coil is equal to or greater than a predetermined value, and the motor has temperature characteristics where the temperature difference between the magnet and the coil becomes smaller as the motor moves away from the efficient operation line in the first coordinate space, and further when a coordinate position in the second coordinate space that indicates the rotation speed and the torque command value is included in the specific region, A motor control method for moving the operating point to a retreat position on an equal torque line that overlaps with the operating point and is spaced apart from the efficient operation line.

2. The torque is limited by setting an upper limit temperature of the coil so that the temperature of the magnet does not exceed the upper limit heat resistance temperature of the magnet, and when the specific region exists on the high torque side of the upper limit heat resistance line that represents the trajectory of the rotation speed and the torque when the temperature of the magnet converges to the upper limit heat resistance temperature in the second coordinate space, 2. The motor control method according to claim 1, wherein the upper limit temperature is set to the temperature of the coil at which the temperature of the magnet becomes equal to or lower than the upper heat resistance temperature when the torque limit is executed when the coordinate position is not included in the specific region, regardless of the coordinate position.

3. 2. A motor control method according to claim 1, wherein the specific region occurs when the voltage of a DC power supply that supplies power to the motor via an inverter exceeds a predetermined threshold voltage and the specific region changes based on the magnitude of the voltage of the DC power supply, and when the voltage of the DC power supply exceeds the threshold voltage and the coordinate position is included in the specific region, the operating point is moved to the evacuation position.

4. 2. The motor control method according to claim 1, wherein the d-axis current command value is increased and the q-axis current command value is decreased when the operating point is moved from the position overlapping with the efficient operation line to the evacuation position.

5. 2. The motor control method according to claim 1, wherein when the operating point is moved from a position overlapping with the efficient operation line to the evacuation position, the d-axis current command value is gradually increased along the equal torque line and the q-axis current command value is gradually decreased along the equal torque line.

6. a current control unit that generates a d-axis current command value and a q-axis current command value for controlling the embedded magnet motor based on a torque command value; a temperature sensor for measuring the temperature of the coil of the motor; a current control unit that generates, in a first coordinate space having a d-axis current and a q-axis current as coordinate axes, the d-axis current command value and the q-axis current command value so that operating points of the d-axis current command value and the q-axis current command value overlap with an efficiency operation line that represents loci of the d-axis current and the q-axis current at which torque output efficiency of the motor is maximized, When a specific region exists in a second coordinate space having coordinate axes of the rotation speed and the torque of the motor where the temperature of the magnet of the motor is higher than the temperature of the coil and the temperature difference between the magnet and the coil is equal to or greater than a predetermined value, and the motor has a temperature characteristic where the temperature difference between the magnet and the coil becomes smaller as the motor moves away from the efficient operation line in the first coordinate space, and further when a coordinate position in the second coordinate space that indicates the rotation speed and the torque command value is included in the specific region, The current control unit A motor control device that moves the operating point to a retracted position on an equal torque line that overlaps with the operating point and is spaced apart from the efficient operation line.

7. The torque is limited by setting an upper limit temperature of the coil so that the temperature of the magnet does not exceed the upper limit heat resistance temperature of the magnet, and when the specific region exists on the high torque side of the upper limit heat resistance line that represents the trajectory of the rotation speed and the torque when the temperature of the magnet converges to the upper limit heat resistance temperature in the second coordinate space, The current control unit 7. The motor control device according to claim 6, wherein the upper limit temperature is set to a temperature at which the temperature of the magnet is equal to or lower than the heat-resistant upper limit temperature when the torque limit is executed when the coordinate position is not included in the specific region, regardless of the coordinate position.

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