Motor control device

Abstract

To improve magnet temperature estimation accuracy by correcting the current dependency of a magnetic flux fluctuation amount caused by a temperature change during magnet temperature estimation.SOLUTION: A motor control unit 10 comprises a magnet temperature estimation unit 40 that inputs a q-axis voltage command value calculated on the basis of one of a motor rotation speed command value and a torque command value, an electric angular speed, and a d-axis current detection value and a q-axis current detection value calculated on the basis of a current detection value, and estimates the temperature of a permanent magnet. The magnet temperature estimation unit 40 is provided with: a d-axis magnetic flux fluctuation amount calculation unit 41 that inputs the q-axis voltage command value, the electric angular speed, the d-axis current detection value, and the q-axis current detection value, and calculates a d-axis magnetic flux fluctuation amount; a d-axis magnetic flux fluctuation amount correction unit 42 that calculates a corrected d-axis magnetic flux fluctuation amount after correction of the d-axis magnetic flux fluctuation amount; a magnet magnetic flux reference value calculation unit 43 that calculates a magnet magnetic flux reference value; and a magnet temperature calculation unit 44 that calculates a magnet temperature estimation value of the permanent magnet on the basis of the corrected d-axis magnetic flux fluctuation amount and the magnet magnetic flux reference value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] As a technique for estimating the magnet temperature of a motor, the techniques described in Patent Documents 1 and 2, for example, have been proposed.

[0003] Patent Document 1 discloses a driving device for a permanent magnet synchronous motor that estimates the amount of fluctuation in magnet magnetic flux between different times based on a voltage command value and outputs a magnet temperature fluctuation amount estimate value corresponding to the amount of magnet magnetic flux fluctuation.

[0004] Furthermore, Patent Document 2 discloses a method for estimating the magnet temperature of a motor, which changes a target current value, calculates the magnet flux based on the d-axis magnetic flux linkage, and estimates the magnet temperature according to the calculated magnet flux. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-2949 [Patent Document 2] Patent Publication No. 2021-16226 Summary of the Invention [Problem to be solved by the invention]

[0006] The technology described in Patent Document 1 aims to accurately estimate magnet flux or magnet temperature, eliminating the influence of constant errors between individual motors due to manufacturing variations, etc. Patent Document 1 discloses a drive device for a permanent magnet synchronous motor that includes a method for calculating a d-axis flux error from the difference between a q-axis voltage command value and a reference q-axis voltage calculated based on constants used in control, calculates a d-axis flux error φ0_err at a reference temperature, calculates a d-axis flux error φ1_err when the magnet temperature changes from the reference temperature, calculates the amount of magnet flux fluctuation from the difference between φ0_err and φ1_err, and outputs a magnet temperature fluctuation amount estimate value corresponding to the amount of magnet flux fluctuation.

[0007] In Patent Document 1, the amount of fluctuation in the d-axis magnetic flux calculated from the difference between φ0_err and φ1_err when there are certain d-axis and q-axis currents is used as the amount of magnet flux fluctuation as is. Because the amount of fluctuation in the d-axis magnetic flux and magnet flux due to changes in magnet temperature has current dependency, meaning that it differs depending on the d-axis and q-axis currents, estimations when the d-axis and q-axis currents are non-zero will produce errors in the estimated value of the amount of fluctuation in the magnet flux, and errors will also occur in the estimated magnet temperature value, so there is room for improvement.

[0008] Patent Document 2 discloses a method for estimating the magnet temperature of a motor, which determines the d-axis magnetic flux before and after changing a target current, calculates the magnet magnetic flux based on each d-axis magnetic flux, and estimates the magnet temperature according to the calculated magnet magnetic flux. In Patent Document 2, when estimating the magnet temperature from the magnet magnetic flux, a table showing the correspondence between the magnet magnetic flux, d-axis current, and q-axis current parameters and the magnet temperature is used, and the current dependency of the magnetic flux fluctuation amount due to temperature change is also taken into consideration when estimating the magnet temperature, but because a table with three input parameters is used, the number of table data becomes large, and the measurement work time for creating the table and the processing load for referencing the table are large, leaving room for improvement.

[0009] An object of the present invention is to provide a motor control device that improves the accuracy of magnet temperature estimation by correcting the current dependency of magnetic flux fluctuations due to temperature changes when estimating magnet temperature. [Means for solving the problem]

[0010] In order to achieve the above object, the motor control device of the present invention is a motor control device including a control unit that controls a motor having a permanent magnet, wherein the control unit inputs a q-axis voltage value calculated based on either a rotation speed command value of the motor or a torque command value of the motor, or calculated based on a voltage detection value of the motor, an electrical angular velocity calculated based on the electrical angle of the motor, and a d-axis current value and a q-axis current value calculated based on the voltage detection value of the motor or the current detection value of the motor, or based on command values, and estimates a temperature of the permanent magnet; The magnet temperature estimation unit is characterized by comprising: a d-axis magnetic flux fluctuation amount calculation unit that receives as input the q-axis voltage value, the electrical angular velocity, the d-axis current value, and the q-axis current value and calculates a d-axis magnetic flux fluctuation amount which is the difference between the d-axis magnetic flux and a d-axis magnetic flux reference value; a d-axis magnetic flux fluctuation amount correction unit that calculates a corrected d-axis magnetic flux fluctuation amount by correcting the d-axis magnetic flux fluctuation amount based on the d-axis current value and the q-axis current value; a magnet flux reference value calculation unit that calculates a magnet temperature estimation value of the permanent magnet based on the corrected d-axis magnetic flux fluctuation amount and the magnet magnetic flux reference value. [Effects of the Invention]

[0011] According to the present invention, the accuracy of magnet temperature estimation can be improved by correcting the current dependency of the magnetic flux fluctuation amount due to temperature changes when estimating the magnet temperature.

[0012] Problems, configurations, and effects other than those described above will become clear from the following description of the embodiments. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic configuration diagram of a motor control device 100 according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing a schematic diagram of the structure of a PM motor 20. [Figure 3] 10 is a diagram showing the relationship between the rotor position θd and the phase of each winding 25 of the stator 21. FIG. [Figure 4] 2 is a block diagram showing the configuration of an inverter 30 and a current detection unit 50. FIG. [Figure 5] 10A and 10B are diagrams illustrating an AC voltage command value and a triangular wave carrier signal for generating a drive signal. [Figure 6] FIG. 2 is a diagram illustrating an example of the configuration of a voltage command value calculation unit 12. [Figure 7] FIG. 10 is a diagram showing the relationship between the d-axis current and the d-axis magnetic flux at a certain q-axis current. [Figure 8] FIG. 4 is a control block diagram of a magnet temperature estimation unit 40. [Figure 9] FIG. 1 is a block diagram including a voltage sensor 70 that measures the output voltage of an inverter 30. [Figure 10] FIG. 4 is a control block diagram of a d-axis magnetic flux fluctuation amount calculation unit 41. [Figure 11] 10 is a diagram showing an example of the relationship between the d-axis current value Id and the q-axis current value Iq and the d-axis magnetic flux reference value Ψd_std, which is stored in the d-axis magnetic flux reference value calculation unit 412 as a table or a formula. FIG. [Figure 12] FIG. 10 is a diagram illustrating an example of the relationship between the q-axis current value Iq and the magnet magnetic flux reference value Ψd0_std. [Figure 13] FIG. 4 is a control block diagram of a d-axis magnetic flux fluctuation amount corrector 42. [Figure 14] FIG. 10 is a diagram showing an example of the relationship between the d-axis current value Id and the q-axis current value Iq and the correction coefficient K, which is stored in the correction coefficient calculation unit 421 as a table or a formula. [Figure 15] FIG. 4 is a control block diagram of a magnet temperature calculation unit 44. [Figure 16] FIG. 10 is a diagram showing an example of the relationship between the magnetic flux change ratio KΨ and the magnet temperature estimated value Tm_est, which is stored in the magnet temperature conversion unit 441 as a table or a formula. [Figure 17] FIG. 10 is a control block diagram showing an example of the configuration of a magnet temperature estimator when a d-axis magnetic flux fluctuation amount corrector is not provided and the magnet magnetic flux reference value is set as a constant. [Figure 18] FIG. 10 is a diagram showing an example of the magnet temperature estimation error of the magnet temperature estimator when a d-axis magnetic flux fluctuation amount corrector is not provided and the magnet magnetic flux reference value is set as a constant. [Figure 19] FIG. 10 is a control block diagram showing an example of the configuration of a magnet temperature estimation unit when a d-axis magnetic flux fluctuation amount correction unit is not provided. [Figure 20] FIG. 10 is a diagram showing an example of a magnet temperature estimation error of the magnet temperature estimator when a d-axis magnetic flux fluctuation amount corrector is not provided. [Figure 21] FIG. 10 is a diagram illustrating an example of a magnet temperature estimation error of the magnet temperature estimator. [Figure 22] FIG. 4 is a control block diagram showing a modified example of the first embodiment. [Figure 23] FIG. 10 is a block diagram showing the configuration of a control unit 10a according to a second embodiment of the present invention. [Figure 24] 2 is a diagram illustrating an example of the configuration of a torque command value limiting unit 16, a d-axis current command value limiting unit 17, and a q-axis current command value limiting unit 18. FIG. [Figure 25] FIG. 10 is a block diagram showing the configuration of a control unit 10b according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, in which like reference numerals denote like elements and the same description will not be repeated.

[0015] The various components of the present invention do not necessarily have to be independent entities, and it is acceptable for multiple components to be formed as a single member, for one component to be formed from multiple members, for one component to be part of another component, or for part of one component to overlap with part of another component, etc. [Example]

[0016] <Outline of motor control device configuration> 1 is a schematic diagram of a motor control device 100 according to a first embodiment of the present invention. The motor control device 100 includes a control unit 10, a PM motor 20, an inverter 30, a current detection means 50, and an angle sensor 60 such as a resolver or an encoder. Although not shown, a mechanism for mechanically or magnetically transmitting mechanical output is connected to the PM motor 20, and the motor control device 100 controls the rotation speed or torque of the PM motor 20 to a desired value.

[0017] In the following explanation, a PM motor 20, i.e., a permanent magnet synchronous motor (PMSM) having a permanent magnet, is used as an example of an electric motor, but the present invention is not limited to this. The present invention can be applied to any electric motor that has the characteristic that the magnetic flux of the permanent magnet changes depending on the temperature of the rotor.

[0018] The inverter 30 has a DC voltage source 120 (see FIG. 4) such as a battery and a bridge circuit made up of switching elements, and outputs a voltage by switching the switching elements in response to an input drive signal. Assuming that the switching operation of the switching elements switches ideally without delay, the voltage output from the inverter 30 will be a pulsed voltage. Using the well-known concept of pulse width modulation, the pulsed voltage can be regarded as an AC voltage.

[0019] In pulse width modulation, the cycle at which the switching element is turned on and off, i.e., the switching frequency, is generally set sufficiently high relative to the frequency of the equivalent AC voltage (which corresponds to the rotational frequency of the single-phase motor in this case). However, it is also possible to consider the fundamental wave component of the pulsed voltage. For example, when the switching frequency is close to the rotational frequency of the PM motor, such as approximately 1 to 3 times, it can be considered that the fundamental wave component of the pulsed voltage is applied to the PM motor 20. Therefore, in this specification, the following explanation will be given assuming that the output voltage of the inverter 30 has an AC waveform.

[0020] Rather than a DC voltage source, it may also be configured to convert an AC power source into DC power by means such as rectification. Alternatively, it may be configured to use a DC / DC converter that controls to a different voltage based on a DC voltage source of a certain voltage.

[0021] As a configuration example, the control unit 10 includes a current command value calculation unit 11, a voltage command value calculation unit 12, a PWM signal generation unit 14, a coordinate conversion unit 13, an angular velocity calculation unit 15, and a magnet temperature estimation unit 40.

[0022] The coordinate conversion unit 13 inputs the current detection value, which is the current information flowing through the PM motor 20 obtained by the current detection means 50, and the motor electrical angle detection value obtained by the angle sensor 60, and converts from the three-phase UVW axes to the dq axes, the definition of which will be described later, and outputs the d-axis current detection value (d-axis current value) and the q-axis current detection value (q-axis current value).

[0023] The angular velocity calculation unit 15 inputs the motor electrical angle detection value obtained by the angle sensor 60 and outputs the electrical angular velocity.

[0024] The current command value calculation unit 11 inputs the rotation speed command value or the torque command value and outputs the d-axis current command value and the q-axis current command value.

[0025] The voltage command value calculation unit 12 inputs the d-axis current command value, the q-axis current command value, the d-axis current detection value, the q-axis current detection value, and the electrical angular velocity, and based on these, generates the d-axis voltage command value and the q-axis voltage command value (q-axis voltage value).

[0026] The PWM signal generation unit 14 inputs the d-axis voltage command value and the q-axis voltage command value, and outputs a PWM signal that controls the on / off of the switching elements constituting the inverter 30 based on these.

[0027] In FIG. 1, the rotation speed command value and the torque command value are shown inside the control unit 10. However, for example, they may be obtained from a higher-level control system or other control systems not shown.

[0028] <Structural example of the PM motor 20> 2 is a diagram showing a schematic diagram of the structure of a PM motor 20. The PM motor 20 is composed of a stator 21 and a rotor 22 arranged on the inner periphery of the stator 21. The stator 21 has a plurality of stator poles 28, each having a winding (coil) 25 wound around a stator core (stator iron core) 26. The rotor 22 has a permanent magnet 27.

[0029] 2 shows an example in which the number of magnetic poles (also called the number of slots) of the stator 21 is six, and the number of magnetic poles of the rotor 22 is two. The numbers of magnetic poles of the stator 21 and the rotor 22 can be freely selected, and the stator 21 and the rotor 22 may have the same number of magnetic poles, or may have different numbers of magnetic poles. Furthermore, the connection of multiple windings may be either parallel or series. In this embodiment, the windings 25 of opposing stator poles 28 are connected in series to form one phase, and the PM motor 20 will be described as an example in which it is configured with three-phase windings.

[0030] When a current flows through the winding 25, the stator magnetic poles 28 generate magnetic poles in the same manner as electromagnets, and the polarity (north pole, south pole) can be changed depending on the direction of the current through the winding 25. In this embodiment, the rotation angle (rotational angle position) of the rotor 22 when a positive DC current flows through the winding 25 and the stator magnetic poles 28 become south poles, attracting the north poles of the permanent magnets 27 of the rotor 22, is defined as zero degrees. Note that, hereinafter, the rotational angle position of the rotor is referred to as rotor position θd. If there are multiple stator magnetic poles 28, one of them is defined as the reference position. In this embodiment, the winding 25 on the right side of FIG. 2 (the winding closest to the U-phase) will be described as the reference position. In this application, the counterclockwise rotation of the rotor 22 is defined as positive rotation.

[0031] The processing within motor control device 100 utilizes information about rotor position θd of rotor 22 of PM motor 20, and the following description will be given assuming that the position information is detected by a resolver, encoder, or the like as angle sensor 60. Naturally, the position information may be obtained by position sensorless control using position estimation means that outputs an estimated rotational angle position of PM motor 20 from the current flowing through and voltage applied to PM motor 20.

[0032] <Explanation of coordinate axes> Here, the definition of the coordinate axes will be explained. FIG. 3 shows the relationship between the rotor position θd and the phase of each winding 25 of the stator 21. The three-phase windings, UV and W, are arranged with an electrical angle difference of 120 degrees. The d-axis is defined as the direction of the main magnetic flux of the permanent magnet provided in the rotor 22, and the dq-axis is defined as the q-axis that is electrically 90 degrees (electrical angle 90 degrees) ahead of the d-axis in the direction of rotation. The dq-axis is a rotating coordinate system. The d-axis can also be defined as the rotational angle position at which the magnetic flux of the permanent magnet 27 that links with the reference winding 25 is at its maximum.

[0033] <Inverter 30> Next, the configuration of the inverter 30 and the current detection unit 50 will be described with reference to the block diagram shown in Fig. 4. Fig. 4 is a block diagram showing the configuration of the inverter 30 and the current detection unit 50.

[0034] 4, inverter 30 includes inverter module 131, DC voltage source 120, and gate driver circuit 123. Here, the output of DC voltage source 120 is assumed to be DC voltage Edc.

[0035] The inverter module 131 has switching elements 32a to 32f (for example, semiconductor switching elements such as IGBTs and MOS-FETs) and freewheeling diodes connected in parallel to the switching elements 32a to 32f. The switching elements 32a to 32f are collectively referred to as "switching elements 32."

[0036] A shunt resistor 135 is connected in series to the DC voltage source 120. This serves to protect the switching element 32 from excessive current flow.

[0037] Two sets of these switching elements 32 are connected in series to form upper and lower arms of each phase. In the example of Fig. 4, the upper and lower arms of the U phase are formed by switching elements 32a and 32b, the upper and lower arms of the V phase are formed by switching elements 32c and 32d, and the upper and lower arms of the W phase are formed by switching elements 32e and 32f. The connection points of the upper and lower arms of each phase are connected to the PM motor 20.

[0038] The gate driver circuit 123 receives a pulsed drive signal (details of which will be described later) output by the PWM signal generating unit 14 shown in Fig. 1, and outputs drive signals 34a to 34f based on the received drive signal. A known technique can be used to generate the drive signals, an example of which is shown in Fig. 5.

[0039] Fig. 5 is a diagram showing AC voltage command values ​​and triangular wave carrier signals for generating drive signals. As shown in Fig. 5, the upper arm drive signal Gp and the lower arm drive signal Gn are generated based on the magnitude relationship between the triangular wave carrier signal and the voltage command values ​​of each phase.

[0040] In the inverter module 131, the switching of each switching element 32 is controlled based on these drive signals 34a to 34f.

[0041] Depending on the switching state of the upper and lower arms, the voltage of each phase of the inverter 30 is either a DC voltage Edc or zero voltage. In the inverter 30, switching is performed at a frequency that is sufficiently higher than the frequency of the AC voltage appearing at the PM motor 20, so the output voltage of each phase of the inverter 30 can be freely adjusted by changing the switching ratio (switching duty) of the upper and lower arms. In other words, a three-phase AC voltage of any frequency can be applied to the PM motor 20, thereby enabling variable speed drive and torque control of the PM motor 20.

[0042] <Current detection means 50> The current detection means 50 detects the currents flowing in the U-phase and W-phase among the three-phase alternating currents flowing from the inverter 30 to the PM motor 20, and outputs the results as alternating current detection values Iu and Iw. Of course, it is also possible to detect the alternating currents of all phases. However, according to Kirchhoff's first law, if two out of the three phases can be detected, the other one phase can be calculated from the two detected phases. A current detection means 50, such as a CT (current transformer), can be provided on the lower arm of the inverter module 131.

[0043] As the current detection means 50, for example, instead of a CT, a phase shunt current detection method can be adopted in which a shunt resistor is added to the lower arm of the inverter module 130, and the currents flowing in each phase of the inverter 30 are detected from the current flowing through the shunt resistor. Instead of or in addition to the current detection means 50, a single shunt current detection method can be adopted in which the current on the AC side of the inverter 30 is detected from the DC current flowing through the shunt resistor 135 added to the DC side of the inverter 30. The single shunt current detection method utilizes the fact that the current flowing through the shunt resistor 135 changes over time depending on the energization state of the switching element 32 constituting the inverter 30.

[0044] <Driving method of the PM motor 20> When driving a motor having a permanent magnet 27 on the rotor 22, if a magnetic flux by the winding 25 is generated at a position advanced by an electrical angle of 90 degrees in the rotational direction with respect to the magnetic flux by the permanent magnet 27, the maximum torque can be obtained with the minimum current. By driving in this way, not only can the miniaturization and weight reduction of the motor be achieved, but there is also an effect that the inverter 30 can be miniaturized.

[0045] The aforementioned d-axis and q-axis can also be described as the magnet flux axis and the winding flux axis, and it is particularly important to appropriately control the current on the q-axis. Separating the current flowing through the motor into a field component and a torque component on the rotating coordinate axis and controlling the voltage phase and magnitude to control the motor's rotational speed or torque is generally called vector control. Note that while control is performed on the dq-axis as a driving method for PM motors, known coordinate transformation techniques can be used to convert from the three-phase UVW axes to the dq-axis.

[0046] For example, the configuration and means described in Japanese Patent Laid-Open No. 2005-39912 are available as the voltage command value calculation unit 12. An example of the configuration of the voltage command value calculation unit 12 when this is used is shown in FIG.

[0047] In the voltage command value calculation unit 12 of FIG. 6, the d-axis and q-axis current command values ​​(Id * and Iq * ) and the electrical angular velocity ωe are input, and vector calculations are performed as in equations (1) and (2), to obtain the d-axis voltage command value Vd * and the q-axis voltage command value Vq * get. Vd * =R×Id ** -ωe×Lq×Iq ** _ fil …(1) Vq * =R×Iq ** +ωe×Ld×Id ** _ fil + ωe×Ke …(2) In equations (1) and (2), R is the winding resistance value per phase of the PM motor 20 (electric motor), Ld is the d-axis inductance, Lq is the q-axis inductance, and Ke is the induced voltage constant.

[0048] In order to make the d-axis and q-axis currents flow as instructed, a d-axis current controller 114a and a q-axis current controller 114b are used in the circuit configuration of Fig. 6. In the d-axis current controller 114a of the circuit configuration of Fig. 6, a subtractor 91d subtracts the d-axis current command value Id *The proportional transformers 92c and 92d multiply the results of this subtraction by predetermined gains Kp_acrd and Ki_acrd, respectively. The integrator 94c multiplies the output result of the proportional transformer 92d, i.e., "Ki_acrd×(Id * The adder 90b adds the multiplication result of the proportional unit 92c and the integration result of the integrator 94c, and calculates the sum as the d-axis current command value Id ** Output as

[0049] Similarly, in the q-axis current controller 114b, a subtractor 91e calculates the q-axis current command value Iq * The proportional transformers 92e and 92f multiply the results of this subtraction by gains Kp_acrq and Ki_acrq, respectively. The integrator 94d multiplies the output result of the proportional transformer 92f, i.e., "Ki_acrq×(Iq * The adder 90c adds the multiplication result of the proportional unit 92e and the integration result of the integrator 94d, and converts the sum into the q-axis current command value Iq ** In this way, the d-axis current controller 14a and the q-axis current controller 14b each constitute a proportional-plus-integral calculator.

[0050] Id ** and Iq ** is multiplied by the winding resistance value R per phase of the PM motor 20 in multipliers 92g and 92i to obtain the first terms on the right-hand sides of equations (1) and (2).

[0051] The second term on the right side of equations (1) and (2) determines the d-axis and q-axis current command values ​​(Idf ** and Iqf**) are the q-axis and d-axis current command values ​​(Iq ** and Id ** ) is a value obtained by filtering using the filter circuits 98a and 98b in FIG. * * and Iqf **Multipliers 92h and 92j multiply this by the q-axis inductance Lq and the d-axis inductance Ld, respectively, and also by the electrical angular velocity ωe to obtain the second term on the right-hand side of equations (1) and (2). Furthermore, multiplier 92k multiplies the electrical angular velocity ωe by the d-axis inductance Ld to obtain the third term on the right-hand side of equation (2).

[0052] A subtractor 91f subtracts the output of the multiplier 92h from the output of the multiplier 92g to obtain a d-axis voltage command value Vd* of the equation (1). An adder 90d obtains the sum of the outputs of the multipliers 92i, 92j, and 92k to obtain a q-axis voltage command value Vq* of the equation (2).

[0053] 6 is characterized by the fact that a d-axis current controller 114a and a q-axis current controller 114b are connected in series to the voltage calculation in the voltage command value calculation unit 12, and that first-order lag filters (low-pass filters) 98a and 98b having a cutoff frequency equivalent to the electrical time constant of the motor are provided. These establish an inverse model of the motor, which has the effect of realizing ideal vector control even when there are restrictions on the calculation cycle of the control unit 10.

[0054] <Challenges for improving torque precision> The motor control device 100 controls the rotation speed or torque of the PM motor 20 to a desired value, but when driving a PM motor, if the temperature of the magnet changes, the magnetic flux changes depending on the temperature, so there is a problem that torque accuracy will deteriorate unless some kind of response is taken.

[0055] If the magnet temperature can be measured, it is possible to improve torque accuracy by adjusting the current command value based on the temperature. However, directly connecting a temperature sensor to the magnet inside the rotor is difficult due to durability and productivity issues. Therefore, estimating the magnet temperature is an effective solution. For example, the configurations and means for estimating magnet temperature are described in the aforementioned Patent Document 1 (JP 2021-2949 A) ​​and Patent Document 2 (JP 2021-16226 A).

[0056] As mentioned in the section on problems in Patent Document 1, the amount of magnetic flux fluctuation due to changes in magnet temperature has current dependency, meaning that it differs depending on the d-axis current and q-axis current. Therefore, when the d-axis current and q-axis current are non-zero, an error occurs in the estimated value of the amount of fluctuation in magnet magnetic flux, and an error also occurs in the estimated magnet temperature.

[0057] Furthermore, in Patent Document 2, when estimating magnet temperature from magnet magnetic flux, a table showing the correspondence between magnet temperature and parameters of magnet magnetic flux, d-axis current, and q-axis current is used, and the magnet temperature is estimated taking into consideration the current dependency of magnetic flux fluctuation amount due to temperature change, but because a table with three parameters is used, the number of table data becomes large, which poses the problem of a large measurement work time for table creation and a large processing load for table reference. Means for solving this problem will be explained below.

[0058] <Concept of the present invention> In the present invention, first the d-axis magnetic flux fluctuation amount is calculated, which is the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value. Next, the d-axis magnetic flux fluctuation amount is corrected based on the d-axis current value and the q-axis current value to the fluctuation amount equivalent to when the d-axis current is zero. The magnet magnetic flux reference value is calculated based on the q-axis current value, and the magnet temperature estimated value is calculated based on the corrected d-axis magnetic flux fluctuation amount and the magnet magnetic flux reference value.

[0059] <Outline of magnet temperature estimation operation in the present invention> The q-axis voltage equation in the steady state can be expressed as follows, ignoring the differential terms and taking each value as an average value:

[0060] Vq * = Vdrop_q + ωe×Ψd …(3) Here, the q-axis voltage command value Vq *, electrical angular velocity ωe, d-axis magnetic flux Ψd, and q-axis voltage drop component Vdrop_q. Vdrop_q is the difference between ωeΨd, which is the speed electromotive force (induced voltage), and the q-axis voltage command value Vq*, and is the overall voltage drop component on the q-axis that includes the voltage drop due to winding resistance, the voltage drop in the switching element 32, the error voltage due to dead time, the error voltage due to the PWM method, etc. The d-axis magnetic flux Ψd can be expressed by the following equation.

[0061] Ψd=Ld×Id+Ψd0 …(4) Here, the d-axis inductance is Ld, the d-axis current value is Id, and the magnet magnetic flux is Ψd0. From equation (4), when Id is zero, the d-axis magnetic flux is Ψd, which is the magnet magnetic flux Ψd0.

[0062] Next, an overview of the magnet temperature estimation operation will be explained using Figure 7. Figure 7 is a diagram showing the relationship between the d-axis magnetic flux and the d-axis current at a certain q-axis current. In equation (4), the d-axis inductance Ld and the magnet magnetic flux Ψd0 change depending on the d-axis current value Id and the q-axis current value Iq. Therefore, the value of the d-axis magnetic flux Ψd changes not only depending on the d-axis current but also on the q-axis current. Therefore, the d-axis magnetic flux curve in Figure 4 changes depending on the value of the q-axis current.

[0063] First, measure and store the d-axis magnetic flux reference value Ψd_std, which is the d-axis magnetic flux at the reference temperature. This corresponds to measuring and storing the d-axis magnetic flux curve at the reference temperature in Figure 7, but as mentioned above, the d-axis magnetic flux also changes depending on the q-axis current value Iq, so measure the d-axis magnetic flux for the d-axis current value Id and the q-axis current value Iq and store it as Ψd_std.

[0064] Next, we will explain how magnet temperature estimation works. If the magnet temperature during estimation differs from the reference temperature, as shown in Figure 7, the d-axis magnetic flux curve during estimation will differ from the d-axis magnetic flux curve at the reference temperature. In a motor that uses a magnet such as a neodymium magnet, where the magnetic flux increases as the magnet temperature drops, if the magnet temperature during estimation is lower than the reference temperature, the d-axis magnetic flux curve during estimation will shift in the positive direction of the d-axis magnetic flux axis compared to the d-axis magnetic flux curve at the reference temperature, as shown in Figure 7. Conversely, if the magnet temperature during estimation is higher than the reference temperature, the d-axis magnetic flux curve during estimation will shift in the negative direction of the d-axis magnetic flux axis compared to the d-axis magnetic flux curve at the reference temperature.

[0065] During estimation, the d-axis current value Id and the q-axis current value Iq are controlled according to the torque command value and rotation speed command value, so it is not possible to measure the entire d-axis magnetic flux curve during estimation. Therefore, first, the d-axis magnetic flux Ψd at the d-axis current value Id and q-axis current value Iq during estimation is calculated using the following equation (5).

[0066] Ψd=(Vq * -Vdrop_q) / ωe …(5) The q-axis voltage drop component Vdrop_q includes voltage drops due to various factors. However, if we consider only the voltage drop due to the total resistance components of the windings, cables, switching element 32, etc., which is the most dominant component, we can calculate it using the following equation (6).

[0067] Vdrop_q=Rall×Iq …(6) Here, Rall is the total resistance value including the windings, cables, switching elements 32, etc. The total resistance value Rall may be obtained by measurement, or may be calculated from the cross-sectional area and length of the conductors of the windings and cables, and the current-voltage characteristics of the switching elements.

[0068] The d-axis magnetic flux reference value Ψd_std stored in advance is calculated based on the d-axis current and q-axis current at the time of estimation, and the d-axis magnetic flux fluctuation amount ΔΨd is calculated using the following equation (7).

[0069] ΔΨd=Ψd―Ψd_std …(7) The d-axis magnetic flux fluctuation amount ΔΨd has current dependency, meaning that it differs depending on the d-axis current value Id and the q-axis current value Iq. The main reason for this is that the magnet magnetic flux changes due to changes in magnet temperature, which changes the magnetic flux density in the iron core inside the motor, resulting in a change in inductance. Therefore, when estimating magnet temperature from the d-axis magnetic flux fluctuation amount ΔΨd, it is necessary to take into account the current dependency of the d-axis magnetic flux fluctuation amount ΔΨd.

[0070] Therefore, the d-axis magnetic flux fluctuation amount ΔΨd at the estimated d-axis current value Id and q-axis current value Iq is corrected so that it is equivalent to the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero. The corrected d-axis magnetic flux fluctuation amount is called the corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp. ΔΨd_cmp is calculated from ΔΨd, Id, and Iq. It is desirable that the difference between ΔΨd_cmp and ΔΨd0 is small.

[0071] The method for calculating ΔΨd_cmp from ΔΨd, Id, and Iq will be described. First, the ratio between ΔΨd0 and ΔΨd calculated in advance under two temperature conditions is recorded as a correction coefficient K. The correction coefficient K is expressed by the following equation (8).

[0072] K=ΔΨd0 / ΔΨd …(8) Since ΔΨd0 varies depending on the q-axis current value Iq, and ΔΨd varies depending on the d-axis current value Id and the q-axis current value Iq, the correction coefficient K is recorded for the d-axis current value Id and the q-axis current value Iq.

[0073] During estimation, ΔΨd_cmp is calculated using the following equation (9).

[0074] ΔΨd_cmp=ΔΨd×K …(9) If the temperature condition 2 condition when correction coefficient K was calculated matches the reference temperature and estimated temperature, ΔΨd_cmp will match ΔΨd0, but if the temperature condition 2 condition when correction coefficient K was calculated matches the reference temperature and estimated temperature, ΔΨd_cmp will not match ΔΨd0. However, regardless of the selection of temperature condition 2, correction coefficient K, which is the ratio of ΔΨd0 to ΔΨd, remains approximately constant, so even if the temperature condition 2 condition when correction coefficient K was calculated matches the reference temperature and estimated temperature, the difference between ΔΨd_cmp and ΔΨd0 is small.

[0075] As described above, the corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp, which is equivalent to the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero, can be calculated from the d-axis magnetic flux fluctuation amount ΔΨd.

[0076] Next, a magnet flux reference value Ψd0_std, which is the magnet flux at the reference temperature, is calculated based on the q-axis current value Iq at the time of estimation. The magnet flux, which is the d-axis magnetic flux when the d-axis current value Id is zero, changes depending on the q-axis current value Iq. The magnet flux reference value Ψd0_std may be measured and stored in advance at the reference temperature, or may be obtained from data when the d-axis current value Id is zero at the d-axis magnetic flux reference value Ψd_std.

[0077] Finally, the magnet temperature estimated value Tm_est is calculated from the corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std. The magnetic flux change ratio KΨ, which is the ratio between ΔΨd_cmp and Ψd0_std, is calculated using the following equation (10).

[0078] KΨ=ΔΨd_cmp / Ψd0_std …(10) The estimated magnet temperature is calculated from the relationship between the magnetic flux change ratio KΨ and the magnet temperature. The correspondence relationship between the magnetic flux change ratio KΨ and the magnet temperature is implemented as a table by changing the magnet temperature in advance and measuring the magnetic flux change ratio KΨ or calculating it through electromagnetic field simulation and storing it. Alternatively, the magnet temperature can be calculated using a formula that inputs the magnetic flux change ratio KΨ.

[0079] The outline of the magnet temperature estimation operation in the present invention has been explained above. Next, the configuration and operation of the magnet temperature estimation unit 40 will be explained in detail.

[0080] <Configuration and operation of magnet temperature estimation unit> Figure 8 is a control block diagram of the magnet temperature estimation unit 40. Figure 9 is a block diagram equipped with a voltage sensor 70 that measures the output voltage of the inverter 30. The operation when estimating the magnet temperature while the motor is being driven will now be described.

[0081] The estimated magnet temperature Tm_est is calculated from the q-axis voltage value Vq, the electrical angular velocity ωe, the d-axis current value Id, and the q-axis current value Iq. Details of each block will be described later.

[0082] First, for the d-axis current value and the q-axis current value, they can be the d-axis current detection value and the q-axis current detection value as shown in the connection of FIG. 1, or the d-axis current command value and the q-axis current command value based on the command value. Also, the q-axis voltage value can be the q-axis voltage command value as shown in the connection of FIG. 1, or as shown in FIG. 9, the output voltage of the inverter 30 is measured by the voltage sensor 70, the voltage detection value is input to the control unit 10, and the voltage detection value is converted from the three-phase UVW axis to the dq axis by the coordinate conversion unit 13a to obtain the d-axis voltage detection value and the q-axis voltage detection value. In this configuration, the q-axis voltage value can be the q-axis voltage detection value.

[0083] In the d-axis magnetic flux variation amount calculation unit 41, the d-axis magnetic flux variation amount ΔΨd is calculated from the q-axis voltage value Vq, the electrical angular velocity ωe, the d-axis current value Id, and the q-axis current value Iq. ΔΨd is the difference between the d-axis magnetic flux Ψd at the time of estimation and the d-axis magnetic flux reference value Ψd_std, which is the d-axis magnetic flux at the reference temperature.

[0084] Next, in the d-axis magnetic flux variation amount correction unit, based on the d-axis current value Id and the q-axis current value Iq, the d-axis magnetic flux variation amount ΔΨd is corrected to be equivalent to the d-axis magnetic flux variation amount ΔΨd0 when Id is zero, and the corrected d-axis magnetic flux variation amount ΔΨd_cmp is calculated.

[0085] In the magnet magnetic flux reference value calculation unit 43, the magnet magnetic flux reference value Ψd0_std is calculated based on the q-axis current value Iq.

[0086] Finally, in the magnet temperature calculation unit 44, the estimated magnet temperature Tm_est is calculated from the corrected d-axis magnetic flux variation amount ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std.

[0087] <Configuration and operation of the d-axis magnetic flux variation amount calculation unit> FIG. 10 is a control block diagram of the d-axis magnetic flux variation amount calculation unit 41. The d-axis magnetic flux calculation unit 411 calculates the d-axis magnetic flux Ψd with the q-axis voltage value Vq, the electrical angular velocity ωe, and the q-axis current value Iq as inputs.

[0088] One method for calculating the d-axis magnetic flux Ψd is a method based on equations (5) and (6). Furthermore, as shown in equation (6), the accuracy of calculating the d-axis magnetic flux Ψd can be improved by adding not only the voltage drop due to the total resistance component Rall among the voltage drop components but also the nonlinear voltage drop component relative to the q-axis current value Iq of the switching element 32 to Vdrop_q. In this case, a table or formula is used that inputs the q-axis current value Iq and outputs the voltage drop of the switching element 32. Furthermore, the error voltage due to the dead time and the error voltage due to the PWM method may be calculated based on the q-axis current value Iq, or the d-axis current value Id, DC voltage Edc, and switching frequency fsw (not shown) that are input to the d-axis magnetic flux calculation unit 411 in FIG. 10, and added to Vdrop_q.

[0089] The d-axis magnetic flux reference value calculation unit 412 calculates the d-axis magnetic flux reference value Ψd_std at the reference temperature based on the d-axis current value Id and the q-axis current value Iq. The calculation method is not limited as long as the d-axis magnetic flux reference value Ψd_std can be calculated from the d-axis current value Id and the q-axis current value Iq.

[0090] One example of a method for calculating the d-axis magnetic flux reference value Ψd_std is to measure or calculate and store the d-axis magnetic flux relative to the d-axis current value Id and the q-axis current value Iq in advance by electromagnetic field simulation, and then create a table of Ψd_std using Id and Iq as parameters, and use this table during estimation. Alternatively, the relationship between the d-axis magnetic flux reference value Ψd_std relative to the d-axis current value Id and the q-axis current value Iq may be expressed as a mathematical formula, which is then used during estimation. As an example of using a mathematical formula, the relationship between the d-axis inductance Ld_std relative to the d-axis current value Id and the q-axis current value Iq at a reference temperature may be stored, and the d-axis magnetic flux reference value Ψd_std may be calculated using the following formula (11):

[0091] Ψd_std=Ld_std×Id+Ψd0_std …(11) Furthermore, when the magnet temperature can be regarded as the reference temperature while the motor is being driven, the d-axis magnetic flux Ψd output by the d-axis magnetic flux calculation unit at that time may be stored as the d-axis magnetic flux reference value Ψd_std for the d-axis current value Id and q-axis current value Iq at that time, and the Ψd_std table may be updated, and the formula for calculating Ψd_std may be updated.

[0092] Finally, the d-axis magnetic flux fluctuation amount calculation unit 41 calculates the d-axis magnetic flux fluctuation amount ΔΨd from the difference between the d-axis magnetic flux Ψd and the d-axis magnetic flux reference value Ψd_std based on equation (7).

[0093] 11 shows an example of the relationship between the d-axis magnetic flux reference value Ψd_std and the d-axis current value Id and the q-axis current value Iq, which is stored as a table or formula in d-axis magnetic flux reference value calculation unit 412. In a magnet motor designed to generate magnetic flux that weakens the magnet magnetic flux as the d-axis current becomes larger in the negative direction, the d-axis magnetic flux decreases as the d-axis current value becomes larger in the negative direction, as shown in FIG.

[0094] The d-axis magnetic flux also changes depending on the q-axis current value. If the d-axis magnetic flux reference value is calculated assuming the magnet flux is constant or the d-axis inductance is constant, an error will occur in the d-axis magnetic flux fluctuation amount ΔΨd, and an error will also occur in the estimated magnet temperature value. By storing the d-axis magnetic flux reference value Ψd_std, which changes depending on the d-axis current and q-axis current, and calculating it based on the d-axis current value Id and q-axis current value Iq during estimation, the d-axis magnetic flux fluctuation amount ΔΨd can be calculated accurately.

[0095] <Configuration and operation of the magnet magnetic flux reference value calculation unit> The magnet flux reference value calculation unit 43 calculates the magnet flux reference value Ψd0_std based on the q-axis current value Iq. An example of the relationship between the q-axis current value Iq and the magnet flux reference value Ψd0_std is shown in Figure 12. The magnet flux reference value calculation unit 43 may use any calculation method as long as it can calculate the magnet flux reference value Ψd0_std from the q-axis current value Iq.

[0096] As an example of a method for calculating the reference value Ψd0_std of the magnet flux, the reference value Ψd0_std of the magnet flux with respect to the q-axis current value Iq at the reference temperature is measured or calculated by electromagnetic field simulation in advance, stored, and a table of Ψd0_std with Iq as a parameter is created for use during estimation. Alternatively, it is also possible to formulate the relationship between the reference value Ψd0_std of the magnet flux and the q-axis current value Iq for use during estimation. Further, the reference value Ψd0_std of the magnet flux is the same as the flux value when the d-axis current value Id in the reference d-axis flux Ψd_std stored in the d-axis flux reference value calculation unit 412 is zero. Therefore, when calculating the reference d-axis flux Ψd_std in the d-axis flux reference value calculation unit 412, it is also possible to calculate the flux value when the d-axis current value Id is zero and use it as the reference value Ψd0_std of the magnet flux, which is the output of the magnet flux reference value calculation unit 43.

[0097] <Configuration and Operation of d-axis Flux Variation Correction Unit> FIG. 13 is a control block diagram of the d-axis flux variation correction unit 42. Based on the d-axis current value Id and q-axis current value Iq during estimation, the corrected d-axis flux variation ΔΨd_cmp equivalent to the d-axis flux variation ΔΨd0 when Id is zero is calculated from the d-axis flux variation ΔΨd. The correction coefficient calculation unit 421 calculates the correction coefficient K with the d-axis current value Id and q-axis current value Iq as inputs. The correction coefficient calculation unit 421 only needs to be able to calculate the correction coefficient K from the d-axis current value Id and q-axis current value Iq, and the calculation method is not limited.

[0098] As an example of a method for calculating the correction coefficient K, the correction coefficient K is calculated and stored based on Equation (8) from ΔΨd0 and ΔΨd measured or calculated by electromagnetic field simulation for the d-axis current value Id and q-axis current value Iq under two temperature conditions in advance, and a table of the correction coefficient K with Id and Iq as parameters is created for use during estimation. Alternatively, it is also possible to formulate the relationship between the correction coefficient K and the d-axis current value Id and q-axis current value Iq for use during estimation.

[0099] Finally, in the d-axis flux variation correction unit 42, the corrected d-axis flux variation ΔΨd_cmp is calculated based on Equation (9).

[0100] FIG. 14 shows an example of the relationship between the d-axis current value Id and the q-axis current value Iq and the correction coefficient K, which is stored as a table or formula in correction coefficient calculation unit 421. Since correction coefficient K is the ratio between the d-axis magnetic flux fluctuation amount ΔΨd and the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero, correction coefficient K is 1 on the straight line where the d-axis current value Id is zero. Although characteristics differ depending on the motor structure, in the case of a motor in which the absolute value of the d-axis magnetic flux fluctuation amount ΔΨd increases as the d-axis current becomes more negative, as shown in FIG. 14, the correction coefficient K decreases as the d-axis current becomes more negative. Furthermore, because the d-axis magnetic flux fluctuation amount ΔΨd also changes depending on the q-axis current, the correction coefficient K also takes on a different value depending on the q-axis current.

[0101] Although the configuration using the correction coefficient K, which is the ratio between ΔΨd0 and ΔΨd, has been described, ΔΨd_cmp may be calculated from ΔΨd, Id, and Iq using a different correction method. Regardless of the correction method, it is sufficient if ΔΨd_cmp equivalent to ΔΨd0 can be calculated.

[0102] <Configuration and operation of magnet temperature calculation unit> 15 is a control block diagram of the magnet temperature calculation unit 44. The magnet temperature estimation value Tm_est is calculated from the corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std. First, the magnetic flux change ratio KΨ, which is the ratio between ΔΨd_cmp and Ψd0_std, is calculated based on equation (10). Next, the magnet temperature conversion unit 441 calculates the magnet temperature estimation value Tm_est from the relationship between the magnetic flux change ratio KΨ and the magnet temperature.

[0103] The correspondence relationship between the magnetic flux change ratio KΨ and the magnet temperature is implemented as a table by changing the magnet temperature and measuring the magnetic flux change ratio KΨ in advance or calculating it through electromagnetic field simulation and storing it. Alternatively, the magnet temperature may be calculated using a formula that inputs the magnetic flux change ratio KΨ.

[0104] FIG. 16 shows an example of the relationship between the magnetic flux change ratio KΨ and the magnet temperature estimate Tm_est, which is stored as a table or formula in the magnet temperature conversion unit 441. When the magnetic flux change ratio KΨ is zero, the magnetic flux change caused by magnet temperature changes is zero, and so the magnet temperature estimate Tm_est is equal to the reference magnet temperature. The magnetic flux change ratio relative to temperature change differs depending on the temperature characteristics of the magnet. In the case of a magnet with characteristics such as a neodymium magnet where the magnet magnetic flux decreases as the temperature increases, as shown in FIG. 16, the magnet temperature estimate decreases as the magnetic flux change ratio increases in the positive direction.

[0105] In the above description, the magnetic flux change ratio KΨ, which is the ratio between the corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std, is calculated, and the magnet temperature estimated value Tm_est is calculated by the magnet temperature conversion unit 441. However, Tm_est may also be calculated from ΔΨd_cmp and Ψd0_std using a different calculation method.

[0106] <Effects of the present invention> The configuration and operation of magnet temperature estimation in this invention utilizes the fact that the ratio between the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero and the magnet magnetic flux reference value Ψd0_std is almost uniquely determined by the difference between the reference temperature and the estimated magnet temperature. If a d-axis magnetic flux fluctuation amount ΔΨd, which is different from the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero, is used directly to estimate the magnet temperature, an estimated temperature error will occur, so a corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp, which is equivalent to the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero, is used. Furthermore, since an estimated temperature error will occur if the magnet magnetic flux reference value Ψd0_std is used as a constant to estimate the magnet temperature, a value calculated based on the q-axis current value Iq is used for Ψd0_std. By correcting ΔΨd to ΔΨd_cmp, which is equivalent to ΔΨd0, and calculating Ψd0_std based on the q-axis current value Iq, the current dependency of the d-axis magnetic flux fluctuation amount ΔΨd due to temperature changes can be appropriately corrected, thereby improving the accuracy of magnet temperature estimation.

[0107] Furthermore, because the d-axis magnetic flux variation amount ΔΨd is corrected based on two parameters, the d-axis current value Id and the q-axis current value Iq, and the magnet magnetic flux reference value Ψd0_std is calculated based on the q-axis current value Iq, the burden of the adjustment work required in advance, the time required, and the processing load during estimation are significantly smaller than in methods that directly calculate the magnet temperature by inputting three parameters, the d-axis current value Id, the q-axis current value Iq, and the d-axis magnetic flux Ψd or magnet magnetic flux. Next, the improvement in accuracy of the magnet temperature estimation value by correcting ΔΨd to ΔΨd_cmp, which is equivalent to ΔΨd0, and calculating Ψd0_std based on the q-axis current value Iq will be described.

[0108] 17 is a control block diagram showing an example configuration of a magnet temperature estimator when a d-axis magnetic flux fluctuation amount corrector is not provided and the magnet flux reference value is set to a constant. There is no d-axis magnetic flux fluctuation amount corrector, and a magnet flux reference value calculation unit 43a outputs a constant magnet flux reference value. The d-axis magnetic flux fluctuation amount calculation unit 41a is the same as the d-axis magnetic flux fluctuation amount calculation unit 41.

[0109] Fig. 18 shows an example of the magnet temperature estimation error of the magnet temperature estimator when there is no d-axis magnetic flux fluctuation correction unit and the magnet flux reference value is a constant. This is the estimation result when the true magnet temperature during estimation is set to a value different from the reference temperature, and the estimated temperature error, obtained by subtracting the true magnet temperature during estimation from the estimated magnet temperature, is plotted against rotation speed and torque. Because no d-axis magnetic flux fluctuation correction is performed and the magnet flux reference value is kept constant, a large estimation error of 100°C occurs. In particular, in the high torque region where the q-axis current is large, the error in the magnet flux reference value becomes large, resulting in a large error in the estimated magnet temperature value as well.

[0110] FIG. 19 is a control block diagram showing an example of the configuration of a magnet temperature estimator when a d-axis magnetic flux fluctuation amount corrector is not provided. Although there is no d-axis magnetic flux fluctuation amount correction unit, the magnet magnetic flux reference value calculation unit 43b is the same as the magnet magnetic flux reference value calculation unit 43, and the d-axis magnetic flux fluctuation amount calculation unit 41a is the same as the d-axis magnetic flux fluctuation amount calculation unit 41.

[0111] Fig. 20 shows an example of the magnet temperature estimation error of the magnet temperature estimator when there is no d-axis magnetic flux fluctuation correction unit. The conditions for the true magnet temperature value during estimation and the method of plotting are the same as Fig. 18. Compared to Fig. 18, the estimated temperature error has been reduced by calculating the magnet magnetic flux reference value based on the q-axis current. However, because the d-axis magnetic flux fluctuation ΔΨd, which is different from the d-axis magnetic flux fluctuation ΔΨd0 when Id is zero, is used as is to estimate the magnet temperature, an estimated temperature error of around 20°C occurs.

[0112] An example of the magnet temperature estimation result by the magnet temperature estimator 40 is shown in Fig. 21. By correcting ΔΨd to ΔΨd_cmp, which is equivalent to ΔΨd0, and calculating Ψd0_std based on the q-axis current value Iq, the current dependency of the d-axis magnetic flux fluctuation amount ΔΨd due to temperature changes can be appropriately corrected, and the estimated temperature error is reduced to around 5°C.

[0113] <Modification of Example 1> In the above explanation, the correction coefficient K and the magnet magnetic flux reference value Ψd0_std are calculated by separate calculation units. From equations (9) and (10), the magnetic flux change ratio KΨ is expressed by the following equation (12).

[0114] KΨ=ΔΨd×K / Ψd0_std …(12) Here, K / Ψd0_std can be combined into a single conversion coefficient Kt, which can be calculated from the d-axis current value and the q-axis current value. In this case, a control block diagram of the part that calculates the magnetic flux change ratio from the d-axis magnetic flux fluctuation amount is shown in Figure 22. The magnetic flux change ratio KΨ can be calculated by calculating the conversion coefficient Kt in conversion coefficient calculation unit 45 based on equation (12) and multiplying it by the d-axis magnetic flux fluctuation amount ΔΨd. [Example]

[0115] A description will now be given of a second embodiment of the present invention. The same components as those in the first embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0116] The configuration of this embodiment can be the same as that of the first embodiment, except for the following points: This embodiment relates to a control unit 10 having means for using information on the magnet temperature estimated value estimated by the magnet temperature estimation unit 40.

[0117] One issue facing motors with permanent magnets in the rotor is thermal demagnetization of the permanent magnets. If the temperature of the permanent magnet rises above a certain level, it can become irreversibly demagnetized. If the permanent magnets become demagnetized, it becomes difficult to control the motor's rotation speed or torque to the desired value. In addition, the current flowing through the motor and inverter may increase in order to ensure the generated torque.

[0118] 23 is a block diagram showing the configuration of a control unit 10a according to Example 2 of the present invention. The control unit 10a of Example 2 has a means for using information for estimating the magnet temperature.

[0119] 23 includes a torque command value limiting unit 16, a d-axis current command value limiting unit 17 that limits the d-axis current command value, and a q-axis current command value limiting unit 18 that limits the q-axis current command value. The torque command value limiting unit 16 limits the torque command value using a magnet temperature estimated value obtained by a magnet temperature estimating unit 40 from a speed command value or a torque command obtained from within the control unit 10a or from a higher-level control system or other control systems (not shown).

[0120] 24 is a diagram showing an example of the configuration of the torque command value limiting unit 16, the d-axis current command value limiting unit 17, and the q-axis current command value limiting unit 18. The magnet temperature estimated value estimated by the magnet temperature estimating unit 40 is input to the command limit value calculating unit 101. The command limit value calculating unit 101 outputs a command limit value according to the input magnet temperature estimated value.

[0121] For example, when the estimated magnet temperature value is equal to or less than the judgment threshold Th and there is no risk of thermal demagnetization, the command limit value is set to the same value as when the magnet temperature is sufficiently low, and when the estimated magnet temperature value exceeds the judgment threshold Th, the command limit value is reduced and output. When the estimated magnet temperature value is high and there is a high risk of thermal demagnetization, the command limit value may be set to zero, and the motor output may be set to zero.

[0122] The command value limiter 102 limits the maximum and minimum values ​​of the torque command value, d-axis current command value, or q-axis current command value based on the command value limit value. Here, the limit values ​​of the maximum and minimum values ​​may be set as command value limit values ​​with different signs but absolute values. Alternatively, a command value limit value calculation unit for the maximum value and a command value limit value calculation unit for the minimum value may be provided, and the limit values ​​of the maximum and minimum values ​​may be set to different values.

[0123] In this way, by configuring the motor control device to include a means for using information about the magnet temperature estimated by the magnet temperature estimator 40, it is possible to prevent thermal demagnetization of the permanent magnets of the PM motor and an excessive increase in the current flowing through the PM motor and the inverter 30. In other words, it is possible to provide a highly reliable motor control device. Here, the motor control device may be configured to include at least one of the torque command value limiter 16, the d-axis current command value limiter 17, and the q-axis current command value limiter 18. Although it is possible to prevent thermal demagnetization of the permanent magnets of the PM motor and an excessive increase in the current flowing through the PM motor and the inverter 30 with one command value limiter, it is also possible to configure the motor control device to include multiple command value limiters in order to ensure redundancy and to reduce output in stages.

[0124] Furthermore, if there is no means for estimating the permanent magnet temperature of the PM motor, the continuous rated output may be set to a small value with a margin relative to the maximum output in order to prevent thermal demagnetization. According to this embodiment, if there is a means for limiting the command value based on the estimated magnet temperature value and suppressing the output, it is possible to set the continuous rated output by minimizing the margin relative to the maximum output. In other words, it is possible to improve the continuous rated output while keeping the motor structure the same. [Example]

[0125] A description will now be given of a third embodiment of the present invention. The same components as those in the first and second embodiments are given the same reference numerals, and detailed descriptions thereof will be omitted.

[0126] The configuration of this embodiment can be the same as that of the first embodiment, except for the following points: This embodiment relates to a control unit 10b having means for using information on the magnet temperature estimated value estimated by the magnet temperature estimation unit 40.

[0127] When controlling the torque of a motor with a permanent magnet in the rotor to a desired value, the magnetic flux changes depending on the temperature of the magnet, which poses a problem of degraded torque accuracy unless some countermeasure is taken. For example, if the motor control device is installed in an electric vehicle system, the degraded torque accuracy can lead to a deterioration in ride comfort and a deterioration in the accuracy of autonomous driving.

[0128] 25 is a block diagram showing the configuration of a control unit 10b according to Example 3 of the present invention. The control unit 10b of Example 3 has a current command value calculation unit 11a that calculates a d-axis current command value and a q-axis current command value using as input the magnet temperature estimated value estimated by a magnet temperature estimation unit 40 in addition to the torque command value.

[0129] When the magnet temperature is at a reference temperature, the current command value calculation unit 11a calculates the d-axis current command value and the q-axis current command value so that the difference between the torque command value and the actual torque of the motor is small. If the magnet temperature differs from the reference temperature, a torque error occurs. Therefore, the d-axis current command value and the q-axis current command value are calculated based on the magnet temperature estimate value and the torque command value so that the torque error due to changes in magnet temperature is small.

[0130] In this way, by configuring the motor control device to have a means for using information on the magnet temperature estimated value estimated by the magnet temperature estimation unit 40, it is possible to reduce deterioration in torque accuracy due to changes in magnet temperature, and to provide a motor control device with high torque accuracy.

[0131] As described above, by providing a q-axis voltage value calculation unit that calculates a q-axis voltage value based on the measured voltage value of the magnet motor, or a voltage command value calculated so that the torque or current of the magnet motor matches a command value, a d-axis magnetic flux fluctuation amount calculation unit that calculates a d-axis magnetic flux fluctuation amount, which is the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value, using the q-axis voltage value, electrical angular velocity, d-axis current value, and q-axis current value as inputs, a d-axis magnetic flux fluctuation amount correction unit that calculates a corrected d-axis magnetic flux fluctuation amount based on the d-axis current value and the q-axis current value, a magnet flux reference value calculation unit that calculates a magnet temperature estimated value based on the corrected d-axis magnetic flux fluctuation amount and the magnet flux reference value, it is possible to correct the current dependency of magnetic flux fluctuation amount due to temperature changes when estimating the magnet temperature, thereby improving the accuracy of magnet temperature estimation, and reducing the burden, time, and processing load during estimation that are required in advance for adjustment work.

[0132] The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations.

[0133] Furthermore, the above-described configurations, functions, processing units, processing procedures, etc. may be partly or entirely realized in hardware, for example, by designing them as integrated circuits, etc. Furthermore, the above-described configurations, functions, etc. may be realized in software, by a processor interpreting and executing a program that realizes each function.

[0134] Furthermore, the signal lines and information lines shown are those considered necessary for explanation, and do not necessarily represent all control lines and information lines. Furthermore, the above-mentioned configurations, functions, processing units, processing procedures, etc. do not necessarily need to be located in the same physical location; for example, some may be located on a network or in the cloud via communication, etc.

[0135] Also, while the motor has been described as having an inner rotor structure with the rotor placed inside the stator, it can also have an outer rotor structure. It can also be a radial gap motor or an axial gap motor. In addition to PMSM, it can also be a synchronous motor or SRM with magnets. [Explanation of symbols]

[0136] 10, 10a, 10b...Control section 11, 11a...Current command value calculation unit 12...Voltage command value calculation unit 13... Coordinate conversion section 14...PWM signal generation section 15...Angular velocity calculation section 16...Torque command value limiting section 17...d-axis current command value limiter 18...q-axis current command value limiter 20...PM motor 27...Permanent magnet 30...Inverter 40...Magnet temperature estimation section 41...d-axis magnetic flux fluctuation calculation unit 42...d-axis magnetic flux fluctuation correction section 43...Magnet magnetic flux reference value calculation unit 44...Magnet temperature calculation section 45...Conversion coefficient calculation section 50...Current detection means 60...Angle sensor 70...Voltage sensor 100...Motor control device 101...Command limit value calculation unit 102...Command value limiter 411...d-axis magnetic flux calculation unit 412...d-axis magnetic flux reference value calculation unit 421...Correction coefficient calculation unit 441...Magnet temperature conversion section

Claims

1. A motor control device including a control unit for controlling a motor having a permanent magnet, The control unit a magnet temperature estimating unit that receives as input a q-axis voltage value calculated based on either a rotation speed command value of the motor or a torque command value of the motor, or calculated based on a voltage detection value of the motor, an electrical angular velocity calculated based on the electrical angle of the motor, and a d-axis current value and a q-axis current value calculated based on the voltage detection value of the motor or the current detection value of the motor, or based on command values, and estimates a temperature of the permanent magnet; The magnet temperature estimation unit a d-axis magnetic flux fluctuation amount calculation unit that receives the q-axis voltage value, the electrical angular velocity, the d-axis current value, and the q-axis current value and calculates a d-axis magnetic flux fluctuation amount that is a difference between the d-axis magnetic flux and a d-axis magnetic flux reference value; a d-axis magnetic flux fluctuation amount correction unit that calculates a corrected d-axis magnetic flux fluctuation amount by correcting the d-axis magnetic flux fluctuation amount based on the d-axis current value and the q-axis current value; a magnet flux reference value calculation unit that calculates a magnet flux reference value based on the q-axis current value; a magnet temperature calculation unit that calculates an estimated magnet temperature value of the permanent magnet based on the corrected d-axis magnetic flux fluctuation amount and the magnet magnetic flux reference value.

2. 2. The motor control device according to claim 1, the d-axis magnetic flux variation calculation unit comprises: a d-axis magnetic flux calculation unit that receives as input the q-axis voltage value, the electrical angular velocity, and the q-axis current value and calculates the d-axis magnetic flux; and a d-axis magnetic flux reference value calculation unit that receives as input the d-axis current value and the q-axis current value and calculates a d-axis magnetic flux reference value, The motor control device according to claim 1, wherein the d-axis magnetic flux fluctuation amount is calculated from a difference between the d-axis magnetic flux and the d-axis magnetic flux reference value.

3. 2. The motor control device according to claim 1, the d-axis magnetic flux fluctuation amount correction unit includes a correction coefficient calculation unit that receives the d-axis current value and the q-axis current value as input and calculates a correction coefficient, and calculates the corrected d-axis magnetic flux fluctuation amount based on the d-axis magnetic flux fluctuation amount and the correction coefficient.

4. The motor control device according to claim 1, the magnet temperature calculation unit comprises a magnet temperature conversion unit that receives as input a magnetic flux change ratio calculated based on the corrected d-axis magnetic flux fluctuation amount and the magnet magnetic flux reference value, and calculates the magnet temperature estimated value.

5. 5. The motor control device according to claim 1, the control unit is provided with a command value limiter that limits maximum and minimum values ​​of the torque command value, the d-axis current value, or the q-axis current value based on the magnet temperature estimated value.

6. 5. The motor control device according to claim 1, The motor control device is characterized in that the control unit includes a current command value calculation unit that calculates a d-axis current command value and a q-axis current command value based on the torque command value and the magnet temperature estimated value.

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