Motor control device and motor control method

Abstract

To provide a motor control device and a motor control method in which, when a magnet temperature is estimated, the error influence of a sensor error on an estimated value can be lessened.SOLUTION: A motor control device 100 includes a d-axis harmonic current superposition unit 121 that superposes a harmonic current on a d-axis current, a first d-axis inductance calculation unit 40 that, when the d-axis harmonic current resulting from superposition of the harmonic current is within a first prescribed range, calculates an estimated value Ld_est1 of a first d-axis inductance on the basis of the d-axis harmonic current, a second d-axis inductance calculation unit 41 that, when the d-axis harmonic current is within a second prescribed range having an upper limit value less than the lower limit value of the first prescribed range, calculates an estimated value Ld_est2 of a second d-axis inductance on the basis of the d-axis harmonic current, and a magnet temperature calculation unit 42 that calculates an estimated magnet temperature value emt of a motor 20 on the basis of the estimated value Ld_est1 of the first d-axis inductance and the estimated value Ld_est2 of the second d-axis inductance.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a driving device for a permanent magnet synchronous motor that includes a superposition unit that superimposes a voltage or current of a frequency different from the frequency of the fundamental wave on the d-axis, and that estimates the magnet temperature from the superimposed voltage or current and the current or voltage obtained by the superposition.

[0003] Furthermore, Patent Document 2 discloses a means for determining an equivalent inductance value of the d-axis and an estimation method for calculating an estimated value of the magnetic flux amount of a permanent magnet based on the equivalent inductance value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-133891 [Patent Document 2] Patent No. 6158115 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses a driving device for a permanent magnet synchronous motor that includes a superposition unit that superimposes a voltage or current of a frequency different from the frequency of the fundamental wave on the d-axis, and that estimates the magnet temperature from the superimposed voltage or current and the current or voltage obtained by the superposition.

[0006] Patent Document 2 discloses a determination means that includes a d-axis inductance equivalent value determination means, an estimation method that calculates an estimated value of the magnetic flux amount of a permanent magnet based on the inductance equivalent value, a high-frequency voltage application means that applies a high-frequency voltage to the d-axis, and a high-frequency current amplitude detection means that detects the amplitude of the high-frequency current that flows through the d-axis in accordance with the voltage applied by the high-frequency voltage application means, and that determines the inductance equivalent value based on the high-frequency voltage and high-frequency current amplitude.

[0007] However, in the technology described in Patent Document 1, if there is an error in the voltage sensor or current sensor, an error will occur in the superimposed voltage or current and the current or voltage obtained by the superposition, and as a result, an error will also occur in the estimated magnet temperature value.

[0008] Similarly, in the technology described in Patent Document 2, if there is an error in the voltage sensor or current sensor, an error occurs in the high-frequency voltage and high-frequency current amplitude, and as a result, an error occurs in the inductance equivalent value.

[0009] To estimate the magnet temperature or the inductance equivalent value with high accuracy, it is necessary to reduce the influence of sensor errors on the estimated value.

[0010] However, the techniques described in Patent Documents 1 and 2 do not describe a method for reducing the effect of sensor errors on the estimated value. Therefore, it is believed that there is room for improvement in the techniques described in Patent Documents 1 and 2.

[0011] An object of the present invention is to provide a motor control device and a motor control method that can reduce the influence of errors on the estimated value due to voltage sensor errors and current sensor errors when estimating magnet temperature. [Means for solving the problem]

[0012] In order to achieve the above object, the present invention is configured as follows.

[0013] A motor control device that drives a motor using an inverter includes a d-axis harmonic current superimposing unit that superimposes a harmonic current on a d-axis current, a first d-axis inductance calculation unit that calculates an estimated value of a first d-axis inductance based on the d-axis harmonic current when the d-axis harmonic current on which the harmonic current is superimposed is within a first predetermined range, a second d-axis inductance calculation unit that calculates an estimated value of a second d-axis inductance based on the d-axis harmonic current when the d-axis harmonic current is within a second predetermined range having an upper limit value that is smaller than a lower limit value of the first predetermined range, and a magnet temperature calculation unit that calculates an estimated value of a magnet temperature of the motor based on the estimated value of the first d-axis inductance and the estimated value of the second d-axis inductance.

[0014] Furthermore, in a motor control method for driving a motor with an inverter, a harmonic current is superimposed on a d-axis current, and when the d-axis harmonic current on which the harmonic current is superimposed is within a first predetermined range, an estimated value of a first d-axis inductance is calculated based on the d-axis harmonic current, and when the d-axis harmonic current is within a second predetermined range having an upper limit value that is smaller than a lower limit value of the first predetermined range, an estimated value of a second d-axis inductance is calculated based on the d-axis harmonic current, and an estimated value of a magnet temperature of the motor is calculated based on the estimated value of the first d-axis inductance and the estimated value of the second d-axis inductance. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a motor control device and a motor control method that can reduce the influence of sensor errors on estimated values ​​when estimating magnet temperature.

[0016] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram showing a motor control device according to a first embodiment. [Figure 2] FIG. 1 is a schematic diagram showing the structure of a PM motor. [Figure 3] FIG. 2 is a diagram showing the relationship between the rotor position and the phase of each winding of the stator. [Figure 4] FIG. 2 is a block diagram of a power conversion circuit and a current detection unit. [Figure 5] FIG. 4 is a diagram illustrating the relationship between a PWM carrier signal and a voltage command value. [Figure 6] FIG. 2 is a diagram illustrating an example of the configuration of a voltage command value calculation unit. [Figure 7] FIG. 3 is a control block diagram of a configuration example of a d-axis harmonic current superimposing unit of the magnet temperature calculation unit of the first embodiment. [Figure 8A] FIG. 10 is a diagram illustrating an example of the waveform of a d-axis harmonic current command value Idh*. [Figure 8B] FIG. 10 is a diagram illustrating another example of the waveform of the d-axis harmonic current command value Idh*. [Figure 8C] FIG. 10 is a diagram showing yet another example of the waveform of the d-axis harmonic current command value Idh*. [Figure 8D] FIG. 10 is a diagram showing yet another example of the waveform of the d-axis harmonic current command value Idh*. [Figure 9] FIG. 10 is a control block diagram of another example of the configuration of the d-axis harmonic current superimposing unit of the magnet temperature calculation unit in the first embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of the relationship between magnet temperature and an estimated d-axis inductance value. [Figure 11] FIG. 4 is a control block diagram of a configuration example of a magnet temperature calculation unit. [Figure 12] FIG. 10 is a diagram showing an example of the relationship between magnet temperature and the ratio of the first d-axis inductance to the second d-axis inductance. [Figure 13] FIG. 10 is a diagram showing an example of a table of magnet temperature estimated values ​​using a first d-axis inductance estimated value and a second d-axis inductance estimated value as parameters. [Figure 14A] FIG. 10 is a diagram showing the magnet temperature estimation error from the first d-axis inductance estimation value in relation to the voltage sensor error and the current sensor error. [Figure 14B] FIG. 10 is a diagram showing the magnet temperature estimation error based on the ratio of the first d-axis inductance to the second d-axis inductance relative to the voltage sensor error and the current sensor error. [Figure 15]FIG. 10 is a diagram showing an example of the characteristic of the magnet temperature change rate of the d-axis inductance estimate value in the second embodiment. [Figure 16A] FIG. 10 is a diagram showing an example of setting a first predetermined range average value and a second predetermined range average value. [Figure 16B] FIG. 10 is a diagram showing another example of setting the first predetermined range average value and the second predetermined range average value. DETAILED DESCRIPTION OF THE INVENTION

[0018] In an embodiment of the present invention, for example, during harmonic current superposition operation for the purpose of estimating the magnet temperature or magnet flux of an electric motor, the first d-axis inductance is calculated when the harmonic current is within a first predetermined range, and the second d-axis inductance is calculated when the harmonic current is within a second predetermined range, and a magnet temperature estimate is calculated based on the first d-axis inductance and the second d-axis inductance, thereby utilizing the fact that the sensor error effects of the first d-axis inductance and the second d-axis inductance are the same to calculate a magnet temperature estimate with reduced sensor error effects.

[0019] 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.

[0020] 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]

[0021] Example 1 <General configuration of motor control device 100> Fig. 1 is a schematic diagram of a motor control device 100. In Fig. 1, the motor control device 100 includes a control unit 10, an electric motor (PM motor) 20, an inverter 30, a current detection means 50, an angle sensor 60 such as a resolver or encoder, a DC voltage source 120, and a voltage sensor 70. Although not shown, a mechanism that mechanically or magnetically transmits 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.

[0022] Although the present invention does not limit the operating principle of the electric motor 20, the following description will be given using an example in which the electric motor 20 is a permanent magnet synchronous motor (PMSM) having a permanent magnet in the rotor. Various types of electric motors are applicable as the electric motor 20, and the subject of this disclosure is an electric motor having the characteristic that the magnetic flux of the permanent magnet changes depending on the temperature of the rotor.

[0023] Inverter 30 is connected to DC voltage source 120 such as a battery, has 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 inverter 30 will be a pulsed voltage. The voltage of DC voltage source 120 is detected by voltage sensor 70.

[0024] Using the well-known concept of pulse width modulation, the pulsed voltage can be regarded as an AC voltage. 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 rotation frequency of a 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, for example, about 1 to 3 times the rotation frequency of the PM motor, it is possible to consider the fundamental wave component of the pulsed voltage as being applied to the PM motor 20. Therefore, in this specification, the following description will be given assuming that the output voltage of the inverter 30 has an AC waveform.

[0025] Instead of a DC voltage source, an AC power source may be converted into DC power by rectification, etc. Alternatively, a DC / DC converter may be used to control a DC voltage source to a different voltage.

[0026] As an example configuration, control unit 10 has 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, a first d-axis inductance calculation unit 40, a second d-axis inductance calculation unit 41, and a magnet temperature calculation unit 42. Voltage command value calculation unit 12 has a d-axis harmonic current superimposition unit 121 that superimposes a harmonic current on a d-axis current, and a current control unit 122.

[0027] The coordinate conversion unit 13 receives as input the current detection value Iw, which is information about the current flowing through the electric motor (PM motor) 20 obtained by the current detection unit 50, and the motor electrical angle detection value θed, which is obtained by the Iu angle sensor 60, and converts the three-phase UVW axes into dq axes, the definitions of which will be described later, and outputs the d-axis current detection value and the q-axis current detection value.

[0028] The angular velocity calculation unit 15 receives the motor electrical angle detection value θed and outputs the electrical angular velocity ωe. The voltage command value calculation unit 12 receives the rotation speed command value or the torque command value as input and generates a d-axis voltage command value vd* and a q-axis voltage command value vq* based on the d-axis current command value id* and the q-axis current command value iq* output by the current command value calculation unit 11, the d-axis current detection value idc and the q-axis current detection value iqc output by the coordinate conversion unit 13, and the electrical angular velocity ωe output by the angular velocity calculation unit.

[0029] The voltage of DC voltage source 120 is detected as a voltage detection value Edc by voltage sensor 70, and PWM signal generation unit 14 outputs a PWM signal that controls the on / off of switching elements that make up inverter 30 based on the detected voltage value, d-axis voltage command value vd*, and q-axis voltage command value vq*. In Fig. 1, the rotation speed command value and torque command value are shown in control unit 10, but there is no problem if they are obtained from, for example, a higher-level control system or another control system not shown.

[0030] Further, the first d-axis inductance calculation unit 40 and the second d-axis inductance calculation unit 41 take as inputs the d-axis voltage command value vd*, the d-axis current detection value idc, the q-axis current detection value iqc, and the electrical angular velocity ωe. However, it is also acceptable to use only some of the values without inputting all of them.

[0031] <Structural Example of PM Motor 20> FIG. 2 is a diagram schematically showing the structure of the PM motor 20. In FIG. 2, the PM motor 20 is composed of a stator 21 and a rotor 22. The stator 21 has a plurality of stator poles 28 in which windings (coils) 25 are wound around a stator core (stator iron core) 26. The rotor 22 has permanent magnets 27.

[0032] FIG. 2 shows an example in which the number of poles of the stator (also called the number of slots) is 6 and the number of poles of the rotor 22 is 2. The number of poles of the stator 21 and the rotor 22 can be freely selected, and there is no problem even if the number of poles of the stator and the rotor 22 are not equal. Also, the connection of the plurality of windings 25 can be either in parallel or in series without any problem. In this specification, it will be described assuming that the windings 25 of the opposing stator poles 28 are connected in series to form one phase, and the PM motor 20 is composed of three-phase windings 25.

[0033] When an electric current flows through the winding 25 of the stator pole 28, poles are generated in the manner of an electromagnet, and the polarity (N pole, S pole) can be changed depending on the direction of the electric current in the winding 25. In this specification, when a positive direct current is passed through the winding 25, the stator pole 28 becomes the S pole, and the rotation angle (rotation angle position) of the rotor 22 when the N pole of the permanent magnet 27 of the rotor 22 is attracted is defined as zero degrees.

[0034] Hereinafter, the rotation angle position of the rotor 22 will be denoted as the rotor position θd. When there are a plurality of windings​​ 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.

[0036] <Explanation of coordinate axes> Here, the definition of the coordinate axes will be explained. FIG. 3 is an explanatory diagram of the coordinate axes, showing 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 27 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.

[0037] <Inverter 30> Next, the configurations of the inverter 30 and the current detection unit 50 will be described with reference to a block diagram of the power conversion circuit and the current detection unit 50 shown in FIG.

[0038] As shown in FIG. 4, inverter 30 is connected to DC voltage source 120 and includes inverter module 131 and gate driver circuit 132. Here, the output of DC voltage source 120 is DC voltage Edc. Inverter module 131 includes switching elements 32a-32f (semiconductor switching elements such as IGBTs and MOS-FETs) and freewheeling diodes connected in parallel to these. Switching elements 32a-32f are collectively referred to as "switching elements 32" (the same applies hereinafter). A shunt resistor 135 is connected in series to DC voltage source 120. This protects switching elements 32 from excessive current flow.

[0039] Two sets of these switching elements 32 are connected in series to form upper and lower arms of each phase. In the example shown in Fig. 4, the upper and lower arms of the U phase are formed by switching elements 32a and 32b, the V phase by switching elements 32c and 32d, and the W phase by switching elements 32e and 32f. The connection point of the upper and lower arms of each phase is connected to the motor 20. The gate driver circuit 132 receives a pulse-like 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 this signal. The drive signals 34a to 34f can be generated using known techniques, but for example, the drive signals can be generated based on the magnitude relationship between the triangular wave carrier signal and the voltage command values ​​of each phase, as shown in Fig. 5. In the inverter module 131, the switching of each switching element 32 is controlled based on these drive signals 34a to 34f.

[0040] Depending on the switching state of the upper and lower arms, the voltage of each phase of the inverter 30 becomes 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 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 electric motor 20, thereby enabling variable speed drive and torque control of the electric motor 20.

[0041] <Current detection unit 50> The current detection unit 50 detects the currents flowing in the U and W phases of the three-phase AC current flowing from the inverter 30 to the electric motor (PM motor) 20, and outputs the results as AC current detection values ​​Iu and Iw. Of course, it is possible to detect the AC current of all phases, but according to Kirchhoff's first law, if two of the three phases can be detected, the current of the remaining phase can be calculated from the detected two phases. The lower arm of the inverter module 131 can be provided with current detection means 50, such as a CT (current transformer).

[0042] As the current detection unit 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 131, and the current flowing through each phase flowing into the inverter 30 is detected from the current flowing through the shunt resistor. Instead of or in addition to the current detection unit 50, a single shunt current detection method for detecting the current on the AC side of the inverter 30 from the DC current flowing through the shunt resistor 135 added to the DC side of the inverter 30 may be adopted. 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 elements 32a to 32f constituting the inverter 30.

[0043] <Driving method of the PM motor 20> When driving a motor having a permanent magnet 27 on the rotor 22, if a magnetic flux is generated by the winding 25 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 realized, but also the inverter 30 can be miniaturized.

[0044] The aforementioned d-axis and q-axis can also be said that the d-axis is the magnet flux axis and the q-axis is the winding flux axis, and it is particularly important to appropriately control the current of the q-axis. Separating the current flowing through the motor in the rotating coordinate axis into the field component and the torque component, and controlling the phase and magnitude of the voltage to control the rotational speed or torque of the motor is generally called vector control. Note that as a driving method of the PM motor 20, control is performed on the dq-axis, and a known coordinate conversion technique can be used for the conversion from the three-phase UVW axis to the dq-axis.

[0045] A configuration example of the voltage command value calculation unit 12 is shown in 12a of FIG. 6. In the voltage command value calculation unit 12a of FIG. 6, the d-axis current command value Id* and the q-axis current command value Iq* calculated by the current command value calculation unit 11 and the motor 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*.

[0046] Vd*=R×Id**-ωe×Lq×Iqf** (1) Vq*=R×Iq**+ωe×Ld×Idf**+ωe×Φd0 ···(2) In equations (1) and (2), R is the winding resistance per phase of the PM motor 20, Ld is the d-axis inductance, Lq is the q-axis inductance, and Φd0 is the magnet magnetic flux. Φd0 is also called the induced voltage constant.

[0047] To ensure that the d-axis and q-axis currents flow as commanded, the configuration of Fig. 6 uses d-axis current control unit 114a and q-axis current control unit 114b. In the circuit configuration of Fig. 6, 91d-91f are subtractors that calculate the difference between the current command values ​​(Id* and Iq*) and their detected values ​​(Idc and Idc), 92c-92k are proportional circuits that add a predetermined gain to the difference, 94c and 94d are integrators, and 90b-90d are adders that add the proportional and integral components to calculate the proportional-integral value. The outputs are the d-axis and q-axis current command values ​​(Id** and Iq**).

[0048] Id** and Iq** are 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).

[0049] The d-axis and q-axis current command values ​​(Idf** and Iqf**) in the second terms on the right-hand sides of equations (1) and (2) are values ​​obtained by filtering the q-axis and d-axis current command values ​​(Iq** and Id**) using filter circuits 98a and 98b in Figure 6. Multipliers 92h and 92j multiply Idf** and Iqf** by the q-axis inductance Lq and the d-axis inductance Ld, respectively, and also by the motor electrical angular velocity ωe to obtain the second terms on the right-hand sides of equations (1) and (2). Furthermore, multiplier 92k multiplies the motor electrical angular velocity ωe by the magnet magnetic flux Φd0 to obtain the third term on the right-hand side of equation (2).

[0050] 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).

[0051] 6 is characterized in that d current control section 114a and q current control section 114b are connected in series to the voltage calculation in voltage command value calculation section 12a, and that first-order lag filters (low-pass filters) 98a and 98b having a cutoff frequency equivalent to the electrical time constant of motor 20 are provided. These establish an inverse model of motor 20, which has the effect of realizing ideal vector control even when the calculation cycle of control section 10 is restricted.

[0052] The d-axis harmonic current superimposing unit 121 in the voltage command value calculation unit 12 will be described later.

[0053] <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 the PM motor 20, if the temperature of the magnet changes, the magnetic flux changes depending on the temperature, so if some kind of response is not taken, there is a problem that torque accuracy will deteriorate.

[0054] 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 issues with durability and productivity. Therefore, estimating the magnet temperature is an effective solution.

[0055] As a method particularly useful when the motor is stopped or rotating at a low speed, a harmonic voltage is applied to the motor to superimpose a harmonic current, the inductance is estimated from the harmonic voltage and the superimposed harmonic current, and the magnet temperature is estimated from the relationship between the magnet temperature and the inductance. However, due to the voltage sensor error of the inverter, an error occurs in the applied harmonic voltage. Similarly, due to the current sensor error of the inverter, an error occurs in the measured value of the harmonic current. Therefore, when there are voltage sensor errors or current sensor errors, an error occurs in the estimated value of the inductance. Since the change in inductance with respect to the magnet temperature is small, the error in the estimated value of the inductance becomes a large error in the estimated magnet temperature.

[0056] Therefore, in estimating the magnet temperature, it is highly necessary to reduce the influence of the voltage sensor error and the influence of the current sensor error.

[0057] <Objective of Example 1> The objective of Example 1 is to calculate the first d-axis inductance when the harmonic current is within the first predetermined range and the second d-axis inductance when the harmonic current is within the second predetermined range during the harmonic current superposition operation for the purpose of estimating the magnet temperature or the magnet flux. By calculating the estimated value of the magnet temperature based on the first d-axis inductance and the second d-axis inductance, the influence of the voltage sensor and current sensor errors represented by the first d-axis inductance and the second d-axis inductance is made the same, and the calculation of the estimated value of the magnet temperature with reduced influence of the sensor error is performed.

[0058] <Configuration and Operation of d-Axis Harmonic Current Superposition Section> Fig. 7 shows the configuration 12a of the voltage command value calculation section including the d-axis harmonic current superposition section 121a. The d-axis harmonic current command value generation section 123 generates the d-axis harmonic current command value Idh*, and the sum of the d-axis current command value id* and the d-axis harmonic current command value Idh* is input to the current control section 122. The current control section 122 controls the d-axis current detection value idc to always be equal to the sum of the d-axis current command value id* and the d-axis harmonic current command value Idh*.

[0059] The d-axis harmonic current command value generation unit 123 performs a superposition operation to change the d-axis harmonic current command value Idh* so that it passes through a first predetermined range at least once and a second predetermined range at least once. A first d-axis inductance calculation unit 40 and a second d-axis inductance calculation unit 41 (described later) calculate d-axis inductance estimates based on the d-axis current values ​​in the first and second predetermined ranges, respectively. Therefore, as long as the d-axis current passes through the first and second predetermined ranges, the waveform pattern of the d-axis harmonic current command value Idh* may have any shape.

[0060] 8A is a diagram showing an example of the waveform of the d-axis harmonic current command value Idh*. In FIG. 8A, the 1-2 predetermined value is greater than the upper limit of the first predetermined range, and the 1-1 predetermined value is less than the lower limit of the first predetermined range. Also, the 2-2 predetermined value is greater than the upper limit of the second predetermined range, and the 2-1 predetermined value is less than the lower limit of the second predetermined range.

[0061] In this example, the d-axis harmonic current command value generator 123 repeats the superimposition operation of the first predetermined range N times (N: an integer equal to or greater than 1), in which the value is changed from a 1-1 predetermined value, which is equal to or less than the lower limit of the first predetermined range, to a 1-2 predetermined value, which is equal to or greater than the upper limit of the first predetermined range, and then changed back to the 1-1 predetermined value. Then, the superimposition operation of the second predetermined range is repeated M times (M: an integer equal to or greater than 1), in which the value is changed to a 2-1 predetermined value, which is equal to or less than the lower limit of the second predetermined range, and then changed from the 2-1 predetermined value to a 2-2 predetermined value, which is equal to or greater than the upper limit of the second predetermined range, and then changed back to the 2-1 predetermined value. The example shown in FIG. 8A is a waveform example when N=3 and M=3.

[0062] A superposition pause period may be provided between the N repetitions of the superposition operation in the first predetermined range and the M repetitions of the superposition operation in the second predetermined range, during which the superposition operation is not performed consecutively and the d-axis harmonic current command value Idh* is kept at a constant value.Furthermore, a superposition pause period may be provided between the superposition operation in the first predetermined range and the superposition operation in the second predetermined range, during which the d-axis harmonic current command value Idh* is kept at a constant value.

[0063] Furthermore, after the overlapping operation in the first predetermined range and the overlapping operation in the second predetermined range are completed, the overlapping operation in the first predetermined range and the overlapping operation in the second predetermined range may be repeatedly performed.

[0064] 8B shows another example of the waveform of the d-axis harmonic current command value Idh*. This is the case where the number of repetitions N of the superimposition operation in the first predetermined range is 1, the number of repetitions M of the superimposition operation in the second predetermined range is 1, and after the superimposition operations in the first predetermined range and the second predetermined range are completed, the superimposition operations in the first predetermined range and the second predetermined range are repeatedly performed.

[0065] 8C is a diagram showing yet another example waveform of the d-axis harmonic current command value Idh*, in which the upper and lower limit values ​​of the first predetermined range are positive current values, and the upper and lower limit values ​​of the second predetermined range are negative current values.

[0066] Fig. 8D is a diagram showing yet another example waveform of the d-axis harmonic current command value Idh*, in which the 1-1 predetermined value and the 2-2 predetermined value are set to 0. In other words, the upper and lower limit values ​​of the first predetermined range are positive current values, and the upper and lower limit values ​​of the second predetermined range are negative current values. Even if the first predetermined range and the second predetermined range have a positive / negative relationship as shown in Fig. 8D, the same effect as the example shown in Fig. 8A can be obtained.

[0067] The configuration of the voltage command value calculation unit 12a shown in Fig. 7 is an example of a configuration in which a harmonic current command value is added to a current command value. In contrast, the configuration of a voltage command value calculation unit 12b, which adds a harmonic voltage command value to a voltage command value, is shown in Fig. 9.

[0068] In FIG. 9, the d-axis harmonic voltage command value generating unit 124 outputs a positive voltage when increasing the d-axis current and outputs a negative voltage when decreasing the d-axis current, thereby superimposing a d-axis current similar to the examples shown in FIGS. 8A, 8B, 8C, and 8D.

[0069] Configuration 12b of the voltage command value calculation unit is not affected by the delay in the current detection value following the current command value by current control unit 122. Configuration 12a, which adds the harmonic current command value to the current command value, requires a waiting time until the current detection value follows the current command value when harmonic superposition starts and ends. In contrast, configuration 12b makes it possible to shorten the time required to start and end harmonic superposition operation.

[0070] The larger the first and second predetermined ranges are, the larger the harmonic current amplitude becomes, which allows the first d-axis inductance estimate value and second d-axis inductance estimate value (described later) to be calculated with high accuracy while minimizing the influence of disturbances such as noise. The larger the harmonic current amplitude, the greater the noise and vibration generated during harmonic current superposition operation. Since noise and vibration are unpleasant to people in the vicinity and may cause damage to the motor control device and its peripheral devices, the first and second predetermined ranges are determined taking into consideration the relationship between the calculation accuracy of the first d-axis inductance estimate value and second d-axis inductance estimate value and the generated noise and vibration.

[0071] The smaller the difference between the 1-1 predetermined value and the lower limit of the first predetermined range, the greater the proportion of the first predetermined range relative to the difference between the 1-2 predetermined value and the 1-1 predetermined value, which is the overall harmonic current amplitude when calculating the first d-axis inductance. By reducing the difference between the 1-1 predetermined value and the lower limit of the first predetermined range, noise and vibrations generated during harmonic current superposition operation can be suppressed. On the other hand, increasing the difference between the 1-1 predetermined value and the lower limit of the first predetermined range can ease the required accuracy of the measurement timing of the current sensor 50. The difference between the 1-1 predetermined value and the lower limit of the first predetermined range is determined taking into account the noise and vibrations generated during harmonic current superposition operation and the required accuracy of the measurement timing of the current sensor 50. Similarly, the differences between the 1-2 predetermined value and the upper limit of the first predetermined range, the difference between the 2-1 predetermined value and the lower limit of the second predetermined range, and the difference between the 2-2 predetermined value and the upper limit of the second predetermined range are also determined taking into account the noise and vibrations generated during harmonic current superposition operation and the required accuracy of the measurement timing of the current sensor 50.

[0072] The period from when the d-axis harmonic current changes from the 1-1 predetermined value to the 1-2 predetermined value and then returns to the 1-1 predetermined value is the harmonic current period during calculation of the first d-axis inductance. The smaller the harmonic current period, the larger the d-axis voltage amplitude when the harmonic current is superimposed, and the first d-axis inductance estimate (described below) can be calculated with high accuracy while minimizing the effects of disturbances such as noise. However, due to the switching frequency of the inverter 30 and the measurement period of the current sensor 50, there is a lower limit to the harmonic current period at which superposition and current measurement are possible. The harmonic current period is determined taking into account the calculation accuracy of the first d-axis inductance estimate, the switching frequency of the inverter 30, and the measurement period of the current sensor 50. Similarly, the period during which the d-axis harmonic current changes from the 2-1 predetermined value to the 2-2 predetermined value and then returns to the 2-1 predetermined value is the harmonic current period during calculation of the second d-axis inductance, and is determined taking into consideration the calculation accuracy of the estimated second d-axis inductance value, the switching frequency of the inverter 30, and the measurement period of the current sensor 50.

[0073] <Operations of the First d-Axis Inductance Calculation Unit 40 and the Second d-Axis Inductance Calculation Unit 41> The relationship between the d-axis voltage command value vd*, motor resistance value R, d-axis current detection value idc, q-axis current detection value iqc, d-axis inductance Ld, q-axis inductance Lq, and electrical angular velocity ωe can be expressed by the following equation (3).

[0074] Vd*=R×idc+Ld×didc / dt-ωe×Lq×iqc (3) The d-axis inductance estimate Ld_est is calculated using the following equation (4) based on equation (3).

[0075] Ld_est=(Vd*-R×idc+ωe×Lq×iqc) / (didc / dt) ···(4) Here, the gradient didc / dt of the detected d-axis current value is calculated from the gradient of the detected d-axis current value Idc as it changes within a predetermined current range. The predetermined current range for calculating the gradient didc / dt of the detected d-axis current value idc is defined as a first predetermined range by a first d-axis inductance calculation unit 40, and as a second predetermined range by a second d-axis inductance calculation unit 41. The q-axis inductance Lq is a design value, an actual measurement value, or a value calculated by electromagnetic field simulation, and is stored and used during inductance estimation.

[0076] When the PM motor 20 is running at a low speed or stopped and the electrical angular velocity ωe is approximately zero, or when the motor torque is approximately zero and the detected q-axis current value iqc is approximately zero, equation (4) can be simplified to the following equation (5).

[0077] Ld_est=(Vd*-R×idc) / (didc / dt) ···(5) Therefore, when the PM motor 20 is running at a low speed or is stopped and the electrical angular velocity ωe is approximately zero, or when the motor torque is approximately zero and the q-axis current detection value iqc is approximately zero, the first d-axis inductance calculation unit 40 and the second d-axis inductance calculation unit 41 do not receive the q-axis current detection value iqc or the electrical angular velocity ωe as input, and there is no need to store ωeLq, and it is possible to calculate the d-axis inductance estimate value from the d-axis voltage command value vd* and the d-axis current detection value idc.

[0078] The first d-axis inductance calculator 40 calculates the first d-axis inductance estimate Ld_est1 from the d-axis voltage command value vd*, the d-axis current detection value idc, the q-axis current detection value iqc, and the electrical angular velocity ωe during a period when the d-axis harmonic current superimposing unit 121 is performing the superimposing operation and the d-axis current is within the first predetermined range. The first d-axis inductance calculator 40 calculates the first d-axis inductance estimate Ld_est1 from the slope of the change from the lower limit value of the first predetermined range to the upper limit value of the first predetermined range, or from the upper limit value of the first predetermined range to the lower limit value of the first predetermined range. In this case, the slope of a portion of the first predetermined range between the lower limit value and the upper limit value of the first predetermined range may be used instead of the slope of the entire range between the lower limit value and the upper limit value of the first predetermined range.

[0079] When the d-axis current detection value idc is within the first predetermined range, the d-axis voltage command value vd* is Vd1*, the d-axis current detection value is Id1, and the gradient didc / dt of the d-axis current detection value is G1, then the first d-axis inductance estimate value Ld_est1 is given by the following equation (6) using equation (5).

[0080] Ld_est1=(Vd1*-R×Id1) / G1 ···(6) The second d-axis inductance calculation unit 41 calculates the estimated value Ld_est2 of the second d-axis inductance from the d-axis voltage command value vd*, the d-axis current detection value idc, the q-axis current detection value iqc, and the electrical angular velocity ωe during the period when the d-axis harmonic current superposition unit 121 is performing the superposition operation and the d-axis current is within a second predetermined range.

[0081] The second d-axis inductance calculation unit 41 calculates the second d-axis inductance from the gradient of the change from the lower limit of the second predetermined range to the upper limit of the second predetermined range, or from the upper limit of the second predetermined range to the lower limit of the second predetermined range. In this case, the gradient of a portion of the range between the lower limit of the second predetermined range and the upper limit of the second predetermined range may be used, rather than the gradient of the entire range between the lower limit of the second predetermined range and the upper limit of the second predetermined range. When the d-axis current detection value idc is within the second predetermined range, the d-axis voltage command value is Vd2*, the d-axis current detection value is Id2, and the gradient didc / dt of the d-axis current detection value is G2. Based on equation (5), the second d-axis inductance estimate Ld_est2 is expressed by the following equation (7).

[0082] Ld_est2=(Vd2*-R×Id2) / G2 ···(7) When an error exists in voltage sensor 70 and the detected voltage value is Kv times larger than the true voltage value of DC voltage source 120, the d-axis voltage applied to PM motor 20 becomes 1 / Kv times the d-axis voltage command value. Compared to when there is no error, the d-axis voltage becomes 1 / Kv times larger, and therefore the slopes G1 and G2 of the detected d-axis current also become 1 / Kv times larger.

[0083] Furthermore, if there is an error in the current sensor 50 and the measured value is Kc times larger than the true value, the detected d-axis current will be Kc times the d-axis current flowing through the PM motor 20. Compared to when there is no error, the detected d-axis current value idc is Kc times larger, so the slopes G1 and G2 of the detected d-axis current value idc are also Kc times larger. Therefore, the slopes G1 and G2 are Kc / Kv due to the voltage sensor error and current sensor error.

[0084] When there is a voltage sensor error and a current sensor error, if the first d-axis inductance estimated value is Ld_est1' and the second d-axis inductance estimated value is Ld_est2', the following equations (8-1) and (8-2) are obtained from equations (6) and (7).

[0085] Ld_est1'=Vd1* / (Kc / Kv×G1)=Kv / Kc×Ld_est1 ···(8-1) Ld_est2'=Vd2* / (Kc / Kv×G2)=Kv / Kc×Ld_est2 ···(8-2) Here, the resistance voltage drop R × Id is ignored because it is minute. From equations (8-1) and (8-2), when there is a voltage sensor error and a current sensor error, both the first d-axis inductance estimated value and the second d-axis inductance estimated value are Kv / Kc times the value when there are no errors.

[0086] <Operation of magnet temperature calculation unit 42> The magnet temperature calculation unit 42 calculates the magnet temperature estimate from the ratio between the first d-axis inductance estimate and the second d-axis inductance estimate. As the magnet temperature rises, the magnet magnetic flux decreases, reducing the magnetic flux density inside the motor. This alleviates magnetic saturation inside the motor, increasing the d-axis inductance. Using this relationship, the magnet temperature is estimated from the d-axis inductance estimate.

[0087] An example of the relationship between the d-axis inductance estimate and the magnet temperature is shown in Fig. 10. In order to focus on the tendency of the d-axis inductance estimate to change with temperature, in Fig. 10 the first d-axis inductance estimate and the second d-axis inductance estimate at the reference temperature are normalized to 1.

[0088] The change in the estimated d-axis inductance value relative to the magnet temperature is affected by the magnetic flux density inside the motor, and therefore differs depending on the current range when calculating the estimated d-axis inductance value. Figure 10 shows an example in which the temperature change rate of the first estimated d-axis inductance value is greater than that of the second estimated d-axis inductance value.

[0089] It is possible to estimate the magnet temperature using only the estimated d-axis inductance value calculated over one current range. However, if there is a voltage sensor error and a current sensor error, the estimated d-axis inductance value will be multiplied by Kv / Kc, causing an error in the estimated magnet temperature value.

[0090] In contrast, by using the first d-axis inductance estimated value and the second d-axis inductance estimated value, the impact of voltage sensor error and current sensor error on the magnet temperature estimated value can be reduced. With only one d-axis inductance estimated value, it is not possible to distinguish whether a change in the d-axis inductance estimated value is due to a change in magnet temperature or a sensor error. By using the first d-axis inductance estimated value and the second d-axis inductance estimated value, which have different temperature change rates, it is possible to distinguish whether a change in the d-axis inductance estimated value is due to a change in magnet temperature or a sensor error.

[0091] 11 shows a configuration example of the magnet temperature calculation unit 42. This is a configuration example that uses the ratio between the first d-axis inductance estimated value and the second d-axis inductance estimated value. A divider 421 calculates the first / second d-axis inductance ratio, which is the ratio between the first d-axis inductance estimated value and the second d-axis inductance estimated value.

[0092] An example of the relationship between the ratio of the first d-axis inductance to the second d-axis inductance and the magnet temperature is shown in Fig. 12. The rate of change of the ratio of the first d-axis inductance to the second d-axis inductance with respect to magnet temperature is, by approximation, the difference between the rates of change of the estimated first d-axis inductance and the estimated second d-axis inductance with respect to magnet temperature.

[0093] Therefore, if the rates of change of the first d-axis inductance estimate and the second d-axis inductance estimate with respect to magnet temperature are different, the first-second d-axis inductance ratio will change according to the magnet temperature, and it will be possible to estimate the magnet temperature from the first-second d-axis inductance ratio.

[0094] Using the ratio between the first d-axis inductance and the second d-axis inductance as input, the inductance ratio to magnet temperature conversion unit 422 calculates an estimated magnet temperature value. The inductance ratio to magnet temperature conversion unit 422 can be configured to measure or calculate by electromagnetic field simulation the magnet temperature versus the ratio between the first d-axis inductance and the second d-axis inductance, store the calculated value, and create a table of estimated magnet temperature values ​​using the ratio between the first d-axis inductance and the second d-axis inductance as a parameter to use during estimation. Alternatively, the relationship between the magnet temperature and the ratio between the first d-axis inductance and the second d-axis inductance may be expressed as a mathematical formula, which is used during estimation.

[0095] When there is a voltage sensor error and a current sensor error, the ratio between the first d-axis inductance and the second d-axis inductance is given by the following equation (9).

[0096] Ld_est1' / Ld_est2' =Kv / Kc×Ld_est1 / (Kv / Kc×Ld_est2) = Ld_est1 / Ld_est2 (9) From equation (9), the ratio Ld_est1' / Ld_est2' between the first d-axis inductance and the second d-axis inductance when there is a voltage sensor error and a current sensor error is the same as the ratio Ld_est1 / Ld_est2 between the first d-axis inductance and the second d-axis inductance when there is no sensor error.

[0097] This reduces the influence of voltage sensor error and voltage sensor error that appears in the magnet temperature estimate.

[0098] Another example of the configuration of magnet temperature calculation unit 42 is to calculate and store the relationship between the magnet temperature and the first d-axis inductance estimated value or the second d-axis inductance estimated value by measurement or electromagnetic field simulation, and create a table of magnet temperature estimated values ​​using the first d-axis inductance estimated value and the second d-axis inductance estimated value as parameters to use during estimation. Alternatively, the relationship between the magnet temperature and the first d-axis inductance estimated value and the second d-axis inductance estimated value may be expressed as a mathematical formula to be used during estimation.

[0099] Figure 13 shows an example of a magnet temperature estimate table, with the first d-axis inductance estimate and the second d-axis inductance estimate as parameters. The magnet temperature estimate (unit: °C) corresponding to the input parameters, the first d-axis inductance estimate and the second d-axis inductance estimate, are shown as contour lines. One way to create a table is to vary the magnet temperature, voltage sensor error, and current sensor error within the ranges expected by the motor control device, calculate the first d-axis inductance estimate and the second d-axis inductance estimate through measurement or circuit and electromagnetic field simulation, and save the results as a table. The minimum and maximum values ​​of the change in the first d-axis inductance estimate when the magnet temperature, voltage sensor error, and current sensor error change correspond to Ld1_min and Ld1_max in Figure 13. Similarly, the minimum and maximum values ​​of the change in the second d-axis inductance estimate correspond to Ld2_min and Ld2_max in Figure A1. During estimation, even if there is a voltage sensor error or a current sensor error, the relationship between the magnet temperature and the first d-axis inductance estimated value and the second d-axis inductance estimated value after they have changed due to the voltage sensor error or the current sensor error is stored in the table, so the effects of the voltage sensor error and the current sensor error that appear on the magnet temperature estimated value can be reduced. In the first embodiment, it is sufficient that the magnet temperature estimated value can be calculated from the first d-axis inductance estimated value and the second d-axis inductance estimated value, and the calculation method is not important.

[0100] <Effects of Example 1> Fig. 14A shows the magnet temperature estimation error versus voltage sensor error and current sensor error when estimating the magnet temperature from the first d-axis inductance estimate value and when estimating the magnet temperature from the first / second d-axis inductance ratio. Fig. 14B shows the magnet temperature estimation error versus voltage sensor error and current sensor error when estimating the magnet temperature from the ratio between the first d-axis inductance estimate value and the second d-axis inductance estimate value. The magnet temperature estimation error (unit: °C) versus voltage sensor error and current sensor error is shown by contour lines.

[0101] When estimating the magnet temperature from the first d-axis inductance estimate shown in Figure 14A, a large estimated temperature error occurs due to the voltage sensor error and the current sensor error. A voltage sensor error of +5% and a current sensor error of -5% results in an estimated temperature error of +50°C.

[0102] When estimating the magnet temperature from the ratio between the first d-axis inductance estimate and the second d-axis inductance estimate shown in Figure 14B, the estimated temperature error is within ±4°C compared to the voltage sensor error and current sensor error of ±5%, making it possible to significantly reduce the impact of sensor errors.

[0103] That is, according to the first embodiment of the present invention, it is possible to provide a motor control device and a motor control method that can reduce the influence of errors on the estimated value due to voltage sensor errors and current sensor errors when estimating the magnet temperature.

[0104] Example 2 Next, a description will be given of Example 2. The configuration of Example 2 can be the same as that of Example 1 except for the following points. Example 2 relates to the d-axis harmonic current superimposing unit 121 and the magnet temperature calculation unit .

[0105] The ratio between the first d-axis inductance and the second d-axis inductance varies for each calculation due to the influence of noise. Therefore, in order to reduce the estimated temperature variation, it is desirable that the rate of change of the ratio between the first d-axis inductance and the second d-axis inductance with respect to the magnet temperature of the PM motor 20 is large.

[0106] For this reason, it is necessary to increase the difference in the rate of change of the first d-axis inductance estimated value and the second d-axis inductance estimated value relative to the magnet temperature.

[0107] Figure 15 shows an example of the relationship between the rate of change of the estimated d-axis inductance per 10°C of magnet temperature and the average value of the specified d-axis current range when the estimated d-axis inductance is calculated. The average value of the specified d-axis current range is the average of the upper limit and lower limit of the specified d-axis current range. The rate of change of the estimated d-axis inductance with temperature varies depending on the average value of the specified d-axis current range when the estimated d-axis inductance is calculated. Although characteristics differ depending on the motor structure, Figure 15 shows an example of a motor that exhibits small characteristics in the negative d-axis current range and large characteristics in the positive d-axis current range.

[0108] FIG. 16A shows an example of setting the first and second predetermined range average values. The first predetermined range average value is the average of the two values: the upper limit value of the first predetermined range and the lower limit value of the first predetermined range. The second predetermined range average value is the average of the two values: the upper limit value of the second predetermined range and the lower limit value of the second predetermined range. The rate of change of the ratio of the first d-axis inductance to the second d-axis inductance with respect to magnet temperature is preferably 1% or more per 10°C change in magnet temperature. This value is equivalent in magnitude to the rate of change of the magnetic flux of a neodymium magnet with temperature, which is approximately -1% per 10°C. One method for estimating magnet temperature during motor rotation uses the temperature change in magnet flux. To maintain the same level of estimated temperature variation due to noise, the temperature change rate of the physical property values ​​used to estimate the magnet temperature must also be approximately the same.

[0109] 16A is the rate of change of the ratio of the first d-axis inductance to the second d-axis inductance with respect to the magnet temperature, the first and second predetermined ranges are determined so that this is 1% or more per 10° C. In other words, the first and second predetermined ranges are set so that the difference between the rate of change of the first d-axis inductance estimate value Ld_est1 with respect to the magnet temperature or rotor temperature of the motor 20 and the rate of change of the second d-axis inductance estimate value Ld_est2 with respect to the magnet temperature or rotor temperature is 1% or more per 10° C.

[0110] Another example of setting the first and second predetermined range average values ​​is shown in Figure 16B. Figure 16B shows a case where the first predetermined range average value is positive and the second predetermined range average value is negative. In the setting example shown in Figure 16B, if the temperature change rate difference is set to 1% or more per 10°C, as in Figure 16A, the absolute values ​​of the first and second predetermined range average values ​​can be made smaller than in the case of Figure 16A.

[0111] Note that the temperature range of the magnet temperature or rotor temperature when calculating the rate of change of the estimated values ​​of the first d-axis inductance and the second d-axis inductance and the difference between each rate of change are not limited to 1% per 10°C as described above; the predetermined difference value for a predetermined temperature range may be, for example, 2% per 20°C or 3% per 30°C. If the predetermined temperature range is A x 10°C (A: real number greater than 0), the predetermined difference value may be A x 1%. In these examples, when the predetermined temperature is converted to 10°C, the predetermined difference value becomes 1%.

[0112] Therefore, according to the second embodiment, it is possible to obtain the same effect as in the first embodiment, and in addition, compared to the first embodiment, it is possible to further reduce the amplitude of the superimposed harmonic current, thereby reducing the power consumption during superimposition and the vibration noise generated by the superimposed harmonic current.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] Also, while the motor has been described as having an inner rotor structure with the rotor placed inside the stator, it can of course also have an outer rotor structure. It also does not matter whether it is a radial gap motor or an axial gap motor. Apart from PMSM, a synchronous motor or SRM with magnets can also be used. [Explanation of symbols]

[0117] 10...control unit, 11...current command value calculation unit, 12...voltage command value calculation unit, 13...coordinate conversion unit, 14...PWM signal generation unit, 15...angular velocity calculation unit, 16...torque command value limiting unit, 17...d-axis voltage command value limiting unit, 18...q-axis current command value limiting unit, 20...electric motor (PM motor), 27...permanent magnet, 30...inverter, 40...first d-axis inductor d-axis inductance calculation unit, 41...second d-axis inductance calculation unit, 42...magnet temperature calculation unit, 50...current detection unit, 70...voltage sensor, 100...motor control device, 114a...d-axis current control unit, 114b...q-axis current control unit, 121...d-axis harmonic current superposition unit, 122...current control unit, 123...d-axis harmonic current command value generation unit, 124...d-axis harmonic voltage command value generation unit

Claims

1. In a motor control device that drives a motor using an inverter, a d-axis harmonic current superimposing unit that superimposes a harmonic current on the d-axis current; a first d-axis inductance calculation unit that calculates an estimated value of a first d-axis inductance based on the d-axis harmonic current when the d-axis harmonic current superimposed thereon is within a first predetermined range; a second d-axis inductance calculation unit that calculates an estimated value of a second d-axis inductance based on the d-axis harmonic current when the d-axis harmonic current is within a second predetermined range; a magnet temperature calculation unit that calculates an estimated value of a magnet temperature of the motor based on the estimated value of the first d-axis inductance and the estimated value of the second d-axis inductance; A motor control device characterized by:

2. 2. The motor control device according to claim 1, The first d-axis inductance calculation unit and the second d-axis inductance calculation unit are a rate of change of the estimated value of the first d-axis inductance with respect to a predetermined temperature range of the magnet temperature or the rotor temperature of the motor; so that a difference in the rate of change of the estimated value of the second d-axis inductance over a predetermined temperature range of the magnet temperature or the rotor temperature is equal to or greater than a predetermined value. A motor control device, characterized in that the first predetermined range and the second predetermined range are set.

3. 3. The motor control device according to claim 1, The d-axis harmonic current superimposing unit a superimposing operation of changing the d-axis harmonic current from a 1-1 predetermined value that is equal to or less than the lower limit value of the first predetermined range to a 1-2 predetermined value that is equal to or more than the upper limit value of the first predetermined range, and then changing the d-axis harmonic current back to the 1-1 predetermined value is repeated N times (N is an integer equal to or greater than 1); Thereafter, the d-axis harmonic current is changed from a 2-1 predetermined value that is equal to or less than the lower limit value of the second predetermined range to a 2-2 predetermined value that is equal to or greater than the upper limit value of the second predetermined range, and then the superposition operation of changing the d-axis harmonic current to the 2-1 predetermined value again is repeated M times (M is an integer equal to or greater than 1).

4. 3. The motor control device according to claim 1, The magnet temperature calculation unit A motor control device comprising: a motor controller that calculates an estimated magnet temperature value based on a ratio between an estimated value of the first d-axis inductance and an estimated value of the second d-axis inductance.

5. 4. The motor control device according to claim 3, The motor control device according to claim 1, wherein the upper and lower limit values ​​of the first predetermined range are positive current values, and the upper and lower limit values ​​of the second predetermined range are negative current values.

6. 4. The motor control device according to claim 3, The motor control device is characterized in that the first-1 predetermined value and the second-2 predetermined value are 0.

7. 2. The motor control device according to claim 1, The first predetermined range and the second predetermined range A motor control device, characterized in that the estimated values ​​of the first d-axis inductance and the second d-axis inductance are determined based on the relationship between the calculation accuracy of the estimated values ​​and the generated noise and vibration.

8. A motor control method for driving a motor using an inverter, comprising: Harmonic current is superimposed on the d-axis current, When the d-axis harmonic current on which the harmonic current is superimposed is within a first predetermined range, an estimated value of a first d-axis inductance is calculated based on the d-axis harmonic current; When the d-axis harmonic current is within a second predetermined range, an estimated value of a second d-axis inductance is calculated based on the d-axis harmonic current; a motor control method comprising: calculating an estimated value of a magnet temperature of the motor based on the estimated value of the first d-axis inductance and the estimated value of the second d-axis inductance;

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