Motor control device

Abstract

The purpose of the present invention is to improve magnet temperature estimation accuracy by correcting the current dependence of a magnetic flux variation amount due to a temperature change when estimating a magnet temperature. A control unit (10) of a motor includes a magnet temperature estimation unit (40) that inputs a q-axis voltage command value and an electrical angular velocity calculated on the basis of either a rotational speed command value or a torque command value of the motor, 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) includes: a d-axis magnetic flux variation amount calculation unit (41) that inputs a q-axis voltage command value, an electrical angular velocity, a d-axis current detection value, and a q-axis current detection value, and calculates a d-axis magnetic flux variation amount; a d-axis magnetic flux variation amount correction unit (42) that calculates a corrected d-axis magnetic flux variation amount in which the d-axis magnetic flux variation amount is corrected; a magnet flux reference value calculation unit (43) that calculates a magnet 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 variation amount and the magnet magnetic flux reference value.

Description

Technical Field

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

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

[0003] Patent Document 1 discloses a permanent magnet synchronous motor drive device that estimates a magnet flux variation between different times based on a voltage command value and outputs a magnet temperature variation estimation value that corresponds to the magnet flux variation.

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

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-2949 Patent Document 2: Japanese Patent Application Publication No. 2021-16226 Summary of the invention Technical problem to be solved by the invention

[0006] The purpose of the technology described in Patent Document 1 is to eliminate the influence of constant errors between individual motors caused by manufacturing differences of the motors, etc., and to estimate the magnet flux or magnet temperature with high accuracy. Patent Document 1 discloses a drive device for a permanent magnet synchronous motor, which has a method for calculating a d-axis flux error based on the difference between a q-axis voltage command value and a reference q-axis voltage calculated based on a constant used in control, and calculates the d-axis flux error at a reference temperature. Calculate the d-axis flux error when the magnet temperature changes from the reference temperature according to and The difference is used to calculate the change in the magnet flux, and an estimated value of the magnet temperature change equivalent to the change in the magnet flux is output.

[0007] In Patent Document 1, when a certain d-axis current and q-axis current are reached, and The change in d-axis magnetic flux calculated by the difference is directly used as the change in magnet magnetic flux. The change in d-axis magnetic flux and magnet magnetic flux caused by the change in magnet temperature has different current dependencies depending on the d-axis current and the q-axis current. Therefore, in the estimation when the d-axis current and the q-axis current are not zero, there will be errors in the estimated value of the change in magnet magnetic flux and errors in the estimated value of the magnet temperature. Therefore, there is room for improvement.

[0008] Patent document 2 discloses a method for estimating the magnet temperature of a motor, wherein the d-axis magnetic flux is obtained before and after changing the target current, the magnetic flux of the magnet is calculated based on each d-axis magnetic flux, and the magnet temperature is estimated based on the calculated magnetic flux. In Patent document 2, when estimating the magnet temperature based on the magnetic flux of the magnet, a table showing the correspondence between the parameters of the magnetic flux of the magnet, the d-axis current, and the q-axis current and the magnet temperature is used, and the current dependence of the magnetic flux variation caused by the temperature change is also considered to estimate the magnet temperature, but since a table with three parameter inputs is used, there is room for improvement in terms of the increase in the amount of table data, the measurement operation time for creating the table, and the processing load of the table reference.

[0009] An object of the present invention is to provide a motor control device that improves the accuracy of estimating the temperature of a magnet by correcting the current dependency of a magnetic flux variation due to temperature change when estimating the temperature of the magnet. Technical means for solving technical problems

[0010] In order to achieve the above-mentioned object, the motor control device of the present invention includes a control unit for controlling a motor having a permanent magnet, characterized in that the control unit includes a magnet temperature estimating unit, which inputs: a q-axis voltage value calculated based on any one of a rotation speed command value of the motor and 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 an electrical angle of the motor; and a d-axis current value and a q-axis current value calculated based on a voltage detection value of the motor or a current detection value of the motor, or based on a command value, and estimates the temperature of the permanent magnet, and the magnet temperature estimating unit includes: a d-axis magnetic flux variation calculation unit, The d-axis magnetic flux variation calculation unit inputs the q-axis voltage value, the electrical angular velocity, the d-axis current value and the q-axis current value, and calculates the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value, namely the d-axis magnetic flux variation; a d-axis magnetic flux variation correction unit, which calculates the corrected d-axis magnetic flux variation based on the d-axis current value and the q-axis current value; a magnet magnetic flux reference value calculation unit, which calculates the magnet magnetic flux reference value based on the q-axis current value; and a magnet temperature calculation unit, which calculates the magnet temperature estimated value of the permanent magnet based on the corrected d-axis magnetic flux variation and the magnet magnetic flux reference value. Effects of the Invention

[0011] According to the present invention, when estimating the magnet temperature, the current dependency of the magnetic flux variation due to the temperature change is corrected, thereby improving the magnet temperature estimation accuracy.

[0012] Problems, structures, and effects other than those described above will become more apparent from the following description of the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic configuration diagram of a motor control device 100 according to the first embodiment of the present invention. Figure 2 2 is a diagram schematically showing the structure of the PM motor 20 . Figure 3 2 is a diagram showing the relationship between the rotor position θd and the phase of each winding 25 of the stator 21 . Figure 4 is a block diagram showing the configuration of the inverter 30 and the current detection unit 50 . Figure 5 It is a diagram showing an AC voltage command value and a triangular wave carrier signal for generating a drive signal. Figure 6 2 is a diagram showing a configuration example of the voltage command value calculation unit 12 . Figure 7 : is a graph showing the relationship between the d-axis magnetic flux and the d-axis current at a certain q-axis current. Figure 8 2 is a control block diagram of the magnet temperature estimating unit 40 . Fig. 9 is a block diagram including a voltage sensor 70 for measuring the output voltage of the inverter 30 . Fig.10 2 is a control block diagram of the d-axis magnetic flux variation calculation unit 41 . Fig.11 1 is a diagram showing an example of the relationship between the d-axis magnetic flux reference value Ψd_std stored as a table or a mathematical expression in the d-axis magnetic flux reference value calculation unit 412 and the d-axis current value Id and the q-axis current value Iq. Fig.12 : is a diagram showing an example of the relationship between the q-axis current value Iq and the magnet flux reference value Ψd0_std. Fig.13 2 is a control block diagram of the d-axis magnetic flux variation correction unit 42 . Fig.14 4 is a diagram showing an example of the relationship between the correction coefficient K stored as a table or a mathematical expression in the correction coefficient calculation unit 421 and the d-axis current value Id and the q-axis current value Iq. Fig.15 4 is a control block diagram of the magnet temperature calculation unit 44 . Fig.16 1 is a diagram showing an example of the relationship between the magnet temperature estimated value Tm_est and the magnetic flux change ratio KΨ stored in the magnet temperature conversion unit 441 as a table or a mathematical expression. Fig.17 1 is a control block diagram showing a configuration example of a magnet temperature estimating unit when the d-axis magnetic flux variation correction unit is not included and the magnet magnetic flux reference value is set to a constant. Fig.18 1 is a diagram showing an example of a magnet temperature estimation error of a magnet temperature estimating unit when the d-axis magnetic flux variation correction unit is not included and the magnet magnetic flux reference value is set to a constant. Fig.19 : is a control block diagram showing a configuration example of a magnet temperature estimating unit when the d-axis magnetic flux variation correction unit is not included. Fig. 20 1 is a diagram showing an example of a magnet temperature estimation error of a magnet temperature estimating unit when the d-axis magnetic flux variation correction unit is not included. Fig.21 : is a diagram showing an example of a magnet temperature estimation error of a magnet temperature estimating unit. Fig. 22 This is a control block diagram showing a modification of the first embodiment. Fig.23 This is a block diagram showing the configuration of a control unit 10a according to a second embodiment of the present invention. Fig.24 1 is a diagram showing a configuration example 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 . Fig.25 This is a block diagram showing the configuration of a control unit 10b according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The same reference numerals are given to the same components, and the same description will not be repeated.

[0015] The various structural elements of the present invention do not necessarily exist separately and independently, but allow multiple structural elements to be composed of one component, one structural element to be composed of multiple components, one structural element to be a part of another structural element, one part of one structural element to overlap with one part of another structural element, etc. [Example 1]

[0016] <Brief Structure of Motor Control Device> Figure 1 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 unit 50, and an angle sensor 60 such as a rotary transformer or an encoder. Although not shown, a mechanism for mechanically or magnetically transmitting a 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 description, a PM motor 20, i.e., a permanent magnet synchronous motor (PMSM) having permanent magnets, is used as an example of a motor, but the present invention is not limited thereto. The present invention is applicable to any motor having a characteristic that the magnetic flux of the permanent magnet changes with the rotor temperature.

[0018] The inverter 30 includes a DC voltage source 120 such as a battery (see Figure 4 ) and a bridge circuit composed of switching elements, and switches the switching elements according to the input drive signal to output voltage. When the switching action of the switching elements is assumed to be switched without delay and ideally, the voltage output from the inverter 30 is a pulse voltage. If the well-known pulse width modulation concept is used, the pulse voltage can be regarded as an AC voltage.

[0019] In addition, in pulse width modulation, the period for turning on / off the switching element, i.e., the switching frequency, is usually set to be high enough with respect to the frequency of the equivalent AC voltage (which is equivalent to the rotational frequency of a single-phase motor here). However, the fundamental component of the pulsed voltage can also be considered. For example, when the switching frequency is around 1 to 3 times the rotational frequency of the PM motor, it can be considered that the fundamental component of the pulsed voltage is applied to the PM motor 20. Therefore, in this specification, it is assumed that the output voltage of the inverter 30 is an AC waveform, and the following description will be given.

[0020] Alternatively, a structure that converts an AC power supply into DC power through rectification or the like can be adopted instead of a DC voltage source. Or, it can be a structure that uses a DC / DC converter that controls a DC voltage source with a certain voltage to a different voltage.

[0021] As a structural 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 unit 50, and the motor electrical angle detection value obtained by the angle sensor 60, and converts them from the three-phase UVW axes to the dq axes defined 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 rotational 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 generates the d-axis voltage command value and the q-axis voltage command value (q-axis voltage value) based on these values.

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

[0027] In Figure 1 , the rotational speed command value and the torque command value are shown in the control unit 10, but it can be a structure obtained from, for example, an upper control system or other control systems not shown.

[0028] <Structural Example of PM Motor 20> Figure 2 2 is a diagram schematically showing the structure of a PM motor 20. The PM motor 20 is composed of a stator 21 and a rotor 22 provided on the inner circumference of the stator 21. The stator 21 has a plurality of stator poles 28 in which a winding (coil) 25 is wound around a stator core (stator core) 26. The rotor 22 has a permanent magnet 27.

[0029] Figure 2 An example is shown in which the number of poles (also called the number of slots) of the stator 21 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 may be a structure in which the number of poles of the stator 21 and the rotor 22 is equal, or may be a structure in which the number of poles of the stator 21 and the rotor 22 is different. In addition, there is no problem in connecting multiple windings in parallel or in series. In the present embodiment, the windings 25 of the relative stator poles 28 are connected in series to form one phase, and are explained as an example in which the PM motor 20 is composed of three-phase windings.

[0030] By passing current through the winding 25, the principle of electromagnet is utilized to generate magnetic poles in the stator magnetic pole 28, and the polarity (N pole, S pole) is changed according to the current direction of the winding 25. In the present embodiment, when a positive direct current is passed through the winding 25, the stator magnetic pole 28 becomes an 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. In addition, the rotation angle position of the rotor is hereinafter referred to as the rotor position θd. When there are multiple stator magnetic poles 28, one of the stator magnetic poles 28 is defined as the reference position. In the present embodiment, the stator magnetic pole 28 is located at Figure 2 The right winding 25 (the winding closest to the U-phase) is described as a reference position. In the present application, the direction in which the rotor 22 rotates counterclockwise is defined as forward rotation.

[0031] In the processing in the motor control device 100, the information of the rotor position θd of the rotor 22 of the PM motor 20 is used, and the configuration is described as detecting the position information by a resolver, an encoder, etc. as the angle sensor 60. Of course, a configuration obtained by position sensorless control using a position estimating unit that outputs an estimated rotation angle position of the PM motor 20 based on the current flowing through the PM motor 20 and the applied voltage applied to the PM motor 20 may also be used.

[0032] <Description of coordinate axes> The definition of the coordinate axes is explained here. Figure 3: is a diagram showing the relationship between the rotor position θd and the phase of each winding 25 of the stator 21. The three-phase windings of UVW are arranged with an electrical angle difference of 120 degrees. The main magnetic flux direction of the permanent magnet set in the rotor 22 is set to the d-axis, and the dq axis consisting of the d-axis and the q-axis electrically advancing 90 degrees (electrical angle 90 degrees) from the d-axis in the rotation direction is defined. The dq axis is a rotating coordinate system. The definition of the d-axis can also be referred to as the rotation angle position where the magnetic flux of the permanent magnet 27 interlinked with the reference winding 25 is the largest.

[0033] <Inverter 30> Next, we will refer to Figure 4 The block diagram shown is used to explain the structure of the inverter 30 and the current detection unit 50. Figure 4 is a block diagram showing the configuration of the inverter 30 and the current detection unit 50 .

[0034] like Figure 4 As shown, the inverter 30 includes an inverter module 131, a DC voltage source 120 and a gate driving circuit 123. Here, the output of the DC voltage source 120 is a DC voltage Edc.

[0035] The inverter module 131 includes switching elements 32a to 32f (for example, semiconductor switching elements such as IGBT or MOS-FET) and return diodes connected in parallel with the switching elements 32a to 32f. The switching elements 32a to 32f are collectively referred to as "switching elements 32".

[0036] The parallel resistor 135 is connected in series to the DC voltage source 120. This serves to protect the switching element 32 from excessive current flowing therethrough.

[0037] By connecting two sets of switching elements 32 in series, these switching elements 32 constitute the upper and lower arms of each phase. Figure 4 In the example, the upper and lower arms of the U phase are composed of switching elements 32a and 32b, the upper and lower arms of the V phase are composed of switching elements 32c and 32d, and the upper and lower arms of the W phase are composed of switching elements 32e and 32f. The connection point of the upper and lower arms of each phase is connected to the PM motor 20.

[0038] The gate drive circuit 123 receives the Figure 1 The PWM signal generating unit 14 outputs a pulsed driving signal (details will be described later), and outputs driving signals 34a to 34f based on the pulsed driving signal. The method for generating the driving signal can use a known technique. Figure 5 An example of this is shown in FIG.

[0039] Figure 5 : is a diagram showing the AC voltage command value and the triangular wave carrier signal used to generate the drive signal. Figure 5As shown, according to the magnitude relationship between the triangular wave carrier signal and the voltage command values of each phase, the drive signal Gp for the upper arm and the drive signal Gn for the lower arm as shown in the figure are generated.

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

[0041] According to the states of the switches of the upper and lower arms, the voltage of each phase of the inverter 30 becomes either the DC voltage Edc or zero voltage. In the inverter 30, since switching is performed at a frequency sufficiently higher than the frequency of the AC voltage appearing in the PM motor 20, the output voltage of each phase of the inverter 30 can be freely adjusted by changing the switching ratio (duty ratio) of the upper and lower arms. That is, a three-phase AC voltage of any frequency can be applied to the PM motor 20, and thus variable speed drive and torque control of the PM motor 20 can be achieved.

[0042] <Current detection unit 50> The current detection unit 50 detects the currents flowing in the U phase and the W phase among the three-phase AC currents flowing from the inverter 30 to the PM motor 20, and outputs the results as AC current detection values Iu and Iw. Of course, the AC currents of all phases can be detected, but according to Kirchhoff's first law, if two of the three phases can be detected, the other phase can be calculated based on the two detected phases. For example, a current detection unit 50 such as a CT (current transformer) can be provided in the lower arm of the inverter module 131.

[0043] As the current detection unit 50, for example, a phase shunt current method can be adopted. In this phase shunt current method, a shunt resistor is added to the lower arm of the inverter module 130 instead of a CT, and the current flowing through each phase of the inverter 30 is detected based on the current flowing through the shunt resistor. A single shunt current detection method can also be adopted to replace the current detection unit 50 or added to the current detection unit 50. This single shunt current detection method detects the current on the AC side of the inverter 30 based on 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 phenomenon that the current flowing through the shunt resistor 135 changes with time according to the energization state of the switching element 32 constituting the inverter 30.

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

[0045] Of the above-mentioned d-axis and q-axis, the d-axis can be called the magnet flux axis, and the q-axis can be called the winding flux axis. It is particularly important to properly control the current of the q-axis. The current flowing through the motor is decomposed into a magnetic field component and a torque component on the rotating coordinate axis. In order to control the speed or torque of the motor, the phase and magnitude of the voltage are controlled. This is generally called vector control. In addition, as a driving method for a PM motor, control is performed on the dq axis, but the three phases can be converted from the UVW axis to the dq axis using a well-known coordinate conversion technology.

[0046] As the voltage command value calculation unit 12 , there is a configuration and method described in Japanese Patent Application Laid-Open No. 2005-39912, for example. Figure 6 2 shows a configuration example of the voltage command value calculation unit 12 when this configuration is used.

[0047] Depend on Figure 6 The voltage command value calculation unit 12 in the embodiment inputs the d-axis and q-axis current command values ​​(Id * andIq * ) and the electrical angular velocity ωe, and perform vector operations as in equations (1) and (2) to obtain the d-axis voltage command value Vd ＊ and q-axis voltage command value Vq ＊ . Vd ＊ =R×Id ＊＊ -ωe×Lq×Iq ＊＊ _ fil …(1) V Q ＊ =R×Iq ＊＊ +ωe×Ld×Id ＊＊ _ fil +ωe×Ke…(2) In equations (1) and (2), R represents the winding resistance value of each phase of the PM motor 20 (motor), Ld represents the d-axis inductance, Lq represents the q-axis inductance, and Ke represents the induced voltage constant.

[0048] In order to make the current of dq axis flow according to the instruction, use Figure 6 The structure of the d-axis current controller 114a and the q-axis current controller 114b. Figure 6 In the d-axis current controller 114a of the circuit structure, the subtractor 91d obtains the d-axis current command value Id from the d-axis current command value Id * The DC axis current detection value Idc is subtracted from the proportionality. The proportionality devices 92c and 92d multiply the subtraction results by the prescribed gains Kp_acrd and Ki_acrd, respectively. The integrator 94c calculates the output result of the proportionality device 92d, i.e., “Ki_acrd×(Id* The adder 90b adds the multiplication result of the scaler 92c and the integration result of the integrator 94c, and uses the addition result as the d-axis current command value Id. ** Output.

[0049] Similarly, in the q-axis current controller 114b, the subtractor 91e obtains the q-axis current command value Iq * The qc axis current detection value Iqc is subtracted from the proportional device 92e and 92f. The subtraction result is multiplied by the gain Kp_acrq and Ki_acrq, respectively. The integrator 94d calculates the output result of the proportional device 92f, i.e., "Ki_acrq×(Iq * -Iqc)" is integrated. The adder 90c adds the multiplication result of the scaler 92e and the integration result of the integrator 94c, and uses the addition result as the q-axis current command value Iq ** Thus, the d-axis current controller 14a and the q-axis current controller 14b each constitute a proportional-integral operator.

[0050] In the multipliers 92g and 92i, the winding resistance R of each phase of the PM motor 20 is multiplied by Id ** andIq ** , find the first term on the right side of equation (1) and equation (2).

[0051] In the second term on the right side of equations (1) and (2), the d-axis and q-axis current command values ​​(Idf ** and Iqf ** ) is by using Figure 6 The filter circuits 98a and 98b in the q-axis and d-axis current command values ​​(Iq ** 、Id ** In multipliers 92h and 92j, the q-axis inductance Lq and the d-axis inductance Ld are respectively multiplied by Idf ** and Iqf ** The second term on the right side of equations (1) and (2) is obtained by multiplying the electrical angular velocity ωe and the electrical angular velocity ωe. Furthermore, the multiplier 92k multiplies the electrical angular velocity ωe by the inductance Ld of the d-axis to obtain the third term on the right side of equation (2).

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

[0053] Figure 6The advantage of the circuit configuration example is that, in the voltage command value calculation unit 12, the d-axis current controller 114a and the q-axis current controller 114b are connected in series to the voltage calculation; and the first-order lag filter (low-pass filter) 98a, 98b having a cutoff frequency equivalent to the electrical time constant of the motor is included. Since an inverse model of the motor is thus established, even when the calculation cycle of the control unit 10 is limited, an effect of achieving ideal vector control is achieved.

[0054] <Technical issues in improving torque accuracy> Although the motor control device 100 controls the rotation speed or torque of the PM motor 20 to a desired value, when the temperature of the magnet changes during driving of the PM motor, the magnetic flux changes according to the temperature, and therefore there is a problem that torque accuracy deteriorates when no countermeasures are taken.

[0055] When the temperature of the magnet can be measured, the torque accuracy can be improved by adjusting the current command value according to the temperature. However, due to durability and productivity issues, it is difficult to directly connect the temperature sensor to the magnet present in the rotor. Therefore, estimating the magnet temperature is an effective countermeasure. Regarding the estimation of the magnet temperature, for example, there are structures and methods described in the above-mentioned patent document 1 (Japanese Patent Gazette No. 2021-2949) and patent document 2 (Japanese Patent Gazette No. 2021-16226). As described in the technical problem column in Patent Document 1, there is the following problem: Since the change in magnetic flux caused by the change in magnet temperature has a current dependence that is different depending on the d-axis current and the q-axis current, when estimating when the d-axis current and the q-axis current are not zero, an error will occur in the estimated value of the change in magnet magnetic flux, and an error will also occur in the estimated value of the magnet temperature.

[0057] In addition, in Patent Document 2, there is a problem that when estimating the magnet temperature based on the magnet flux, a table showing the correspondence between the parameters of the magnet flux, d-axis current, and q-axis current and the magnet temperature is used, and the magnet temperature is estimated by also considering the current dependence of the flux variation caused by the temperature change, but since a table with three parameter inputs is used, the amount of table data becomes large, and the measurement operation time for creating the table and the processing load of the table reference are large. The following is a description of a method for solving this problem.

[0058] <Concept of the Invention> In the present invention, the d-axis magnetic flux variation is first calculated as the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value. Then, based on the d-axis current value and the q-axis current value, the d-axis magnetic flux variation is corrected to a variation equivalent to that 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 estimation value is calculated based on the corrected d-axis magnetic flux variation and the magnet magnetic flux reference value.

[0059] <Overview of Magnet Temperature Estimation Operation in the Present Invention> The q-axis voltage equation in a steady state can be expressed as follows when the differential term is ignored and each value is taken as an average value.

[0060] V Q ＊ =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 sum of ωeΨd as the velocity electromotive force (induced voltage) and the q-axis voltage command value Vq * The difference between , and is the overall voltage drop component on the q-axis including the voltage drop caused by the winding resistance, the voltage drop at the switching element 32, the error voltage caused by the dead time, the error voltage caused by the PWM method, etc. The d-axis magnetic flux Ψd can be expressed by the following formula. Ψd=Ld×Id+Ψd0…(4) Here, Ld is the d-axis inductance, Id is the d-axis current value, and Ψd0 is the magnet flux. It can be seen from equation (4) that when Id is zero, the d-axis flux Ψd becomes the magnet flux Ψd0.

[0062] Next, use Figure 7 The outline of the magnet temperature estimation operation will be described. Figure 7 It is a graph showing the relationship between the d-axis magnetic flux and the d-axis current under a certain q-axis current. In equation (4), the d-axis inductance Ld and the magnetic flux Ψd0 change according to 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 with the d-axis current, but also with the q-axis current. Therefore, Figure 4 The d-axis flux curve in changes with the q-axis current value.

[0063] First, the d-axis magnetic flux reference value Ψd_std as the d-axis magnetic flux at the reference temperature is measured and stored in advance. This is equivalent to measuring and storing Figure 7 The d-axis magnetic flux curve at the reference temperature in , but as mentioned above, the d-axis magnetic flux also changes with the q-axis current value Iq, so the d-axis magnetic flux relative to the d-axis current value Id and the q-axis current value Iq is measured and stored as Ψd_std.

[0064] Next, the operation when estimating the magnet temperature is described. When the magnet temperature during estimation is different from the reference temperature, Figure 7 As shown in FIG. 1 , the d-axis magnetic flux curve at the estimated time is different from the d-axis magnetic flux curve at the reference temperature. In a motor using a magnet such as a neodymium magnet whose magnetic flux increases when the magnet temperature decreases, if the magnet temperature at the estimated time is lower than the reference temperature, Figure 7 As shown, the d-axis magnetic flux curve at the time of estimation will move toward the positive direction of the d-axis magnetic flux axis relative to the d-axis magnetic flux curve at the reference temperature. Conversely, when the magnet temperature at the time of estimation is higher than the reference temperature, the d-axis magnetic flux curve at the time of estimation will move toward the negative direction of the d-axis magnetic flux axis relative to the d-axis magnetic flux curve at the reference temperature.

[0065] Since the d-axis current value Id and the q-axis current value Iq are controlled according to the torque command value or the speed command value during estimation, it is not possible to measure all d-axis magnetic flux curves during estimation. Therefore, first, the d-axis magnetic flux Ψd at the d-axis current value Id and the q-axis current value Iq during estimation is calculated by the following formula (5).

[0066] Ψd=(Vq ＊ -Vdrop_q) / ωe…(5) The q-axis voltage drop component Vdrop_q includes voltage drops caused by various factors, but if only the voltage drop caused by the total resistance component of the winding, cable, switching element 32, etc., which is the most dominant factor, is considered, it can be calculated by the following formula (6).

[0067] Vdrop_q=Rall×Iq…(6) Here, Rall is the total resistance value including the winding, cable, switch element 32, etc. The total resistance value Rall can be obtained by measurement, or calculated based on the conductor cross-sectional area and length of the winding and cable, and the current-voltage characteristics of the switch element.

[0068] Based on the d-axis current and the q-axis current at the time of estimation, the d-axis magnetic flux reference value Ψd_std stored in advance is calculated. Then, the d-axis magnetic flux variation ΔΨd is calculated by the following equation (7). ΔΨd=Ψd-Ψd_std…(7) The d-axis magnetic flux variation ΔΨd has a current dependency that varies with the d-axis current value Id and the q-axis current value Iq. This is mainly because the magnetic flux changes due to changes in the magnet temperature, and the magnetic flux density of the iron core inside the motor changes, resulting in changes in inductance. Therefore, when estimating the magnet temperature based on the d-axis magnetic flux variation ΔΨd, the current dependency of the d-axis magnetic flux variation ΔΨd needs to be considered.

[0070] Therefore, the d-axis magnetic flux variation ΔΨd at the estimated d-axis current value Id and the q-axis current value Iq is corrected so that the d-axis magnetic flux variation ΔΨd is equivalent to the d-axis magnetic flux variation ΔΨd0 when Id is zero. The corrected d-axis magnetic flux variation is set to the corrected d-axis magnetic flux variation ΔΨd_cmp. ΔΨd_cmp is calculated based on ΔΨd, Id, and Iq. Preferably, the difference between ΔΨd_cmp and ΔΨd0 is small.

[0071] The calculation method of ΔΨd_cmp from ΔΨd, Id, and Iq is described below. First, the ratio of ΔΨd0 and ΔΨd calculated under two pre-existing temperature conditions is recorded as a correction coefficient K. The correction coefficient K is represented by the following equation (8).

[0072] K=ΔΨd0 / ΔΨd…(8) Since ΔΨd0 changes with the q-axis current value Iq and ΔΨd changes with the d-axis current value Id and the q-axis current value Iq, the correction coefficient K is recorded with respect to the d-axis current value Id and the q-axis current value Iq. During estimation, ΔΨd_cmp is calculated by the following equation (9).

[0074] ΔΨd_cmp=ΔΨd×K…(9) When the two temperature conditions when the correction coefficient K is obtained are consistent with the reference temperature and the temperature during estimation, ΔΨd_cmp and ΔΨd0 are consistent, but when the two temperature conditions when the correction coefficient K is obtained are different from the reference temperature and the temperature during estimation, ΔΨd_cmp and ΔΨd0 are inconsistent. However, since the correction coefficient K, which is the ratio of ΔΨd0 and ΔΨd, is almost constant regardless of the selection of the two temperature conditions, even when the two temperature conditions when the correction coefficient K is obtained are inconsistent with the reference temperature and the estimated temperature, the difference between ΔΨd_cmp and ΔΨd0 is small.

[0075] Thus, based on the d-axis magnetic flux variation ΔΨd, the corrected d-axis magnetic flux variation ΔΨd_cmp corresponding to the d-axis magnetic flux variation ΔΨd0 when Id is zero can be calculated.

[0076] Next, based on the estimated q-axis current value Iq, the magnet flux at the reference temperature, i.e., the magnet flux reference value Ψd0_std, is calculated. The d-axis flux when the d-axis current value Id is zero, i.e., the magnet flux, changes with the q-axis current value Iq. The magnet flux reference value Ψd0_std can be measured and stored in advance at the reference temperature, or can be obtained from data when the d-axis current value Id is zero in the d-axis flux reference value Ψd_std. Finally, the magnet temperature estimated value Tm_est is calculated based on the corrected d-axis magnetic flux variation ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std. The magnetic flux variation ratio KΨ, which is the ratio of ΔΨd_cmp to Ψd0_std, is calculated by the following equation (10).

[0078] KΨ=ΔΨd_cmp / Ψd0_std…(10) The estimated value of the magnet temperature is calculated based on the relationship between the magnetic flux change ratio KΨ and the magnet temperature. The magnetic flux change ratio KΨ is measured by changing the magnet temperature in advance, or the magnetic flux change ratio KΨ is calculated by electromagnetic field simulation and stored, and the correspondence between the magnetic flux change ratio KΨ and the magnet temperature is realized as a table. Alternatively, the magnet temperature can be calculated by a mathematical formula with the magnetic flux change ratio KΨ as input.

[0079] The above is a description of the outline of the magnet temperature estimation operation in the present invention. Next, the structure and operation of the magnet temperature estimation unit 40 will be described in detail.

[0080] <Structure and Operation of Magnet Temperature Estimation Unit> Figure 8 2 is a control block diagram of the magnet temperature estimating unit 40 . Fig. 9 3 is a block diagram including a voltage sensor 70 for measuring the output voltage of the inverter 30. Next, the operation of estimating the temperature of the magnet during the driving of the motor will be described.

[0081] The magnet temperature estimated value Tm_est is calculated based on 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, the d-axis current value and the q-axis current value can be as follows Figure 1 The d-axis current detection value and the q-axis current detection value may be connected to the d-axis current detection value, or the d-axis current command value and the q-axis current command value may be based on the command value. In addition, the q-axis voltage value may be as follows: Figure 1 The q-axis voltage command value may be connected as in Fig. 9 As shown, the output voltage of the inverter 30 is measured by using the voltage sensor 70, and the voltage detection value is input into the control unit 10. The voltage detection value is converted from the UVW axis of the three phases to the dq axis through the coordinate conversion unit 13a, thereby obtaining a structure of a d-axis voltage detection value and a q-axis voltage detection value, thereby setting the q-axis voltage value to the q-axis voltage detection value.

[0083] The d-axis magnetic flux change amount calculation unit 41 calculates the d-axis magnetic flux change amount ΔΨd based on 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 change amount correction unit, based on the d-axis current value Id and the q-axis current value Iq, the d-axis magnetic flux change amount ΔΨd is corrected to the d-axis magnetic flux change amount ΔΨd0 corresponding to the case where Id is zero, and the corrected d-axis magnetic flux change 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 magnet temperature estimated value Tm_est is calculated based on the corrected d-axis magnetic flux change amount ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std.

[0087] <Structure and operation of the d-axis magnetic flux change amount calculation unit> Fig.10 is the control block diagram of the d-axis magnetic flux change 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] As one of the calculation methods of the d-axis magnetic flux Ψd, there is a method based on Equations (5) and (6). In addition, as shown in Equation (6), by adding not only the voltage drop caused by all the resistance components Rall in the voltage drop component to Vdrop_q, but also the non-linear voltage drop component with respect to the q-axis current value Iq of the switching element 32 to Vdrop_q, the calculation accuracy of the d-axis magnetic flux Ψd can be improved. In this case, a table or mathematical formula that takes the q-axis current value Iq as an input and outputs the voltage drop of the switching element 32 is used. In addition, based on the q-axis current value Iq, Fig.10 the error voltage caused by the dead time and the error voltage caused by the PWM method are calculated with the unillustrated d-axis current value Id, the DC voltage Edc, and the switching frequency fsw, which are inputs to the d-axis magnetic flux calculation unit 411, and they are 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. As long as the d-axis magnetic flux reference value Ψd_std can be calculated based on the d-axis current value Id and the q-axis current value Iq, the calculation method is not limited.

[0090] As an example of a method for calculating the d-axis flux reference value Ψd_std, it can be configured as follows: the d-axis flux relative to the d-axis current value Id and the q-axis current value Iq is measured in advance, or the d-axis flux relative to the d-axis current value Id and the q-axis current value Iq is calculated using an electromagnetic field simulation, and stored, a Ψd_std table with Id and Iq as parameters is created, and the table is used when estimating. Alternatively, it can be configured as follows: the relationship between the d-axis flux reference value Ψd_std and the d-axis current value Id and the q-axis current value Iq is converted into a mathematical formula, and used when estimating. As an example of using a mathematical formula, it can be configured as follows: the relationship between the d-axis inductance Ld_std at the reference temperature and the d-axis current value Id and the q-axis current value Iq is stored in advance, and the d-axis flux reference value Ψd_std is calculated using the following formula (11).

[0091] Ψd_std=Ld_std×Id+Ψd0_std…(11) In addition, during the motor driving process, when the magnet temperature can be regarded as the reference temperature, the d-axis magnetic flux Ψd output by the d-axis magnetic flux calculation unit at this time can be stored as the d-axis magnetic flux reference value Ψd_std relative to the d-axis current value Id and the q-axis current value Iq at this time, the table of Ψd_std is updated, and the mathematical formula used to calculate Ψd_std is updated.

[0092] Finally, the d-axis magnetic flux variation calculation unit 41 calculates the d-axis magnetic flux variation 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] Fig.11 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 stored in the d-axis magnetic flux reference value calculation unit 412 as a table or a mathematical expression is shown in FIG. Fig.11 As shown, in a magnetic motor designed to generate magnetic flux that weakens the magnet magnetic flux as the d-axis current increases in the negative direction, the d-axis magnetic flux decreases as the d-axis current value increases in the negative direction.

[0094] In addition, the d-axis magnetic flux also changes according to the q-axis current value. If the d-axis magnetic flux reference value is calculated by making the magnet magnetic flux constant or the d-axis inductance constant, the d-axis magnetic flux change amount ΔΨd will have an error, and the magnet temperature estimation value will also have an error. By pre-storing the d-axis magnetic flux reference value Ψd_std that changes with the d-axis current and the q-axis current, and calculating it based on the d-axis current value Id and the q-axis current value Iq during estimation, the d-axis magnetic flux change amount ΔΨd can be accurately calculated.

[0095] <Structure and Operation of 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. Fig.12 An example of the relationship between the q-axis current value Iq and the magnet flux reference value Ψd0_std is shown. In the magnet flux reference value calculation unit 43, as long as the magnet flux reference value Ψd0_std can be calculated based on the q-axis current value Iq, the calculation method is not limited.

[0096] As an example of the calculation method of the magnet flux reference value Ψd0_std, it can be configured to: measure in advance the magnet flux reference value Ψd0_std with respect to the q-axis current value Iq at the reference temperature, or calculate the magnet flux reference value Ψd0_std with respect to the q-axis current value Iq at the reference temperature by using electromagnetic field simulation, store it, create a table of Ψd0_std with Iq as a parameter, and use this table during estimation. Alternatively, it can be configured to convert the relationship between the magnet flux reference value Ψd0_std and the q-axis current value Iq into a mathematical formula and use this mathematical formula during estimation. In addition, the magnet flux reference value Ψd0_std and the reference d-axis flux Ψd_std stored in the d-axis flux reference value calculation unit 412 have the same flux value when the d-axis current value Id is zero. Therefore, when calculating the reference d-axis flux Ψd_std in the d-axis flux reference value calculation unit 412, the flux value when the d-axis current value Id is zero can be calculated and used as the magnet flux reference value Ψd0_std, which is the output of the magnet flux reference value calculation unit 43.

[0097] <Structure and operation of the d-axis flux variation correction unit> Fig.13 This is the 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 according to the d-axis flux variation ΔΨd. The correction coefficient calculation unit 421 takes the d-axis current value Id and q-axis current value Iq as inputs to calculate the correction coefficient K. The correction coefficient calculation unit 421 only needs to be able to calculate the correction coefficient K based on the d-axis current value Id and q-axis current value Iq, and the calculation method is not limited.

[0098] As an example of the calculation method of the correction coefficient K, it can be configured to: calculate and store the correction coefficient K based on Equation (8) according to ΔΨd0 and ΔΨd measured or calculated by using electromagnetic field simulation for the d-axis current value Id and q-axis current value Iq under two pre-existing temperature conditions, create a table of the correction coefficient K with Id and Iq as parameters, and use this table during estimation. Alternatively, the relationship between the correction coefficient K and the d-axis current value Id and q-axis current value Iq can be converted into a mathematical formula and used during estimation.

[0099] Finally, the d-axis magnetic flux variation correction unit 42 calculates the corrected d-axis magnetic flux variation ΔΨd_cmp based on equation (9).

[0100] Fig.14 An example of the relationship between the correction coefficient K stored in the correction coefficient calculation unit 421 as a table or a mathematical expression and the d-axis current value Id and the q-axis current value Iq is shown. The correction coefficient K is the ratio of the d-axis magnetic flux variation ΔΨd to the d-axis magnetic flux variation ΔΨd0 when Id is zero. Therefore, on the straight line where the d-axis current value Id is zero, the correction coefficient K is 1. Although the characteristics of the motor vary depending on its structure, in the case of a motor in which the absolute value of the d-axis magnetic flux variation ΔΨd increases as the d-axis current increases in the negative direction, as shown in FIG. Fig.14 As shown, as the d-axis current increases in the negative direction, the correction coefficient K decreases. In addition, since the d-axis magnetic flux variation ΔΨd also changes with the q-axis current, the correction coefficient K also changes with the q-axis current.

[0101] Although the configuration using the correction coefficient K which is the ratio of ΔΨd0 and ΔΨd has been described, another correction method may be used to calculate ΔΨd_cmp from ΔΨd, Id, and Iq. Whatever correction method is used, it is sufficient as long as ΔΨd_cmp equivalent to ΔΨd0 can be calculated.

[0102] <Structure and Operation of Magnet Temperature Calculation Unit> Fig.15 It is a control block diagram of the magnet temperature calculation unit 44. The magnet temperature estimated value Tm_est is calculated based on the corrected d-axis magnetic flux variation ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std. First, the ratio of ΔΨd_cmp to Ψd0_std, that is, the magnetic flux change ratio KΨ, is calculated based on formula (10). Next, in the magnet temperature conversion unit 441, the magnet temperature estimated value Tm_est is calculated based on the relationship between the magnetic flux change ratio KΨ and the magnet temperature.

[0103] The magnet temperature is changed in advance, the flux change ratio KΨ is measured, or the flux change ratio KΨ is calculated by electromagnetic field simulation and stored, and the correspondence between the flux change ratio KΨ and the magnet temperature is realized as a table. Alternatively, the magnet temperature can be calculated by a mathematical formula with the flux change ratio KΨ as input.

[0104] Fig.16An example of the relationship between the flux change ratio KΨ and the magnet temperature estimated value Tm_est stored in the magnet temperature conversion unit 441 as a table or a mathematical expression is shown. When the flux change ratio KΨ is zero, the flux change caused by the magnet temperature change is zero, so the magnet temperature estimated value Tm_est is equal to the reference magnet temperature. The flux change ratio for temperature change varies depending on the temperature characteristics of the magnet. In the case of a neodymium magnet having a characteristic that the magnet flux decreases as the temperature increases, such as Fig.16 As shown in FIG. 1 , there is a relationship in which the estimated magnet temperature value decreases as the magnetic flux change ratio increases in the positive direction.

[0105] Although the structure of calculating the ratio of the corrected d-axis magnetic flux variation ΔΨd_cmp to the magnet magnetic flux reference value Ψd0_std, that is, the magnetic flux change ratio KΨ, and calculating the magnet temperature estimated value Tm_est by the magnet temperature conversion unit 441 has been described, other calculation methods can be used to calculate Tm_est based on ΔΨd_cmp and Ψd0_std.

[0106] <Effects of the Invention> In the structure and operation of the magnet temperature estimation of the present invention, the following characteristics are utilized: the ratio of the d-axis magnetic flux variation ΔΨd0 when Id is zero to the magnet magnetic flux reference value Ψd0_std is almost uniquely determined according to the difference between the reference temperature and the magnet temperature at the time of estimation. If the d-axis magnetic flux variation ΔΨd different from the d-axis magnetic flux variation ΔΨd0 when Id is zero is directly used for magnet temperature estimation, an estimated temperature error will occur, so a corrected d-axis magnetic flux variation ΔΨd_cmp equivalent to the d-axis magnetic flux variation ΔΨd0 when Id is zero is used. In addition, if the magnet magnetic flux reference value Ψd0_std is set to a constant value for estimating the magnet temperature, an estimated temperature error will occur, so a value calculated based on the q-axis current value Iq is used as Ψd0_std. By correcting ΔΨd to ΔΨd_cmp equivalent to ΔΨd0 and calculating Ψd0_std based on the q-axis current value Iq, the current dependency of the d-axis magnetic flux variation ΔΨd due to temperature change can be appropriately corrected, thereby improving the accuracy of magnet temperature estimation.

[0107] In addition, since the d-axis magnetic flux change ΔΨd is corrected based on the two parameters of the d-axis current value Id and the q-axis current value Iq, and the magnet flux reference value Ψd0_std is calculated based on the q-axis current value Iq, the load, time and processing load of the adjustment work required in advance and the processing load during estimation are greatly reduced compared to the method of directly calculating the magnet temperature using the three parameters of the d-axis current value Id, the q-axis current value Iq, the d-axis magnetic flux Ψd or the magnet flux as input. Next, a description will be given of how the accuracy of the estimated magnet temperature value can be improved by correcting ΔΨd to ΔΨd_cmp equivalent to ΔΨd0 and calculating Ψd0_std based on the q-axis current value Iq.

[0108] Fig.17 1 is a control block diagram showing a configuration example of a magnet temperature estimation unit when the d-axis magnetic flux variation correction unit is not included and the magnetic flux reference value is set to a constant. When the d-axis magnetic flux variation correction unit does not exist, the magnetic flux reference value calculation unit 43a outputs a fixed value of the magnetic flux reference value. The d-axis magnetic flux variation calculation unit 41a is the same as the d-axis magnetic flux variation calculation unit 41.

[0109] Fig.18 An example of the magnet temperature estimation error of the magnet temperature estimation unit is shown when the d-axis magnetic flux variation correction unit is not included and the magnet flux reference value is set to a constant. This is the estimation result when the true value of the magnet temperature at the time of estimation is set to a value different from the reference temperature, and the estimated temperature error obtained by subtracting the true value of the magnet temperature at the time of estimation from the magnet temperature estimation value relative to the speed and torque is plotted. Since the magnet flux reference value is made constant without correcting the d-axis magnetic flux variation, a large estimation error of 100°C is generated. In particular, in the high torque region where the q-axis current becomes large, the error of the magnet flux reference value becomes large, and a large error also occurs in the magnet temperature estimation value.

[0110] Fig.19 1 is a control block diagram showing a configuration example of a magnet temperature estimation unit without including a d-axis magnetic flux variation correction unit. Although there is no d-axis magnetic flux variation 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 variation calculation unit 41a is the same as the d-axis magnetic flux variation calculation unit 41.

[0111] Fig. 20 An example of the magnet temperature estimation error of the magnet temperature estimation unit when the d-axis magnetic flux variation correction unit is not included is shown. The conditions and plotting method of the magnet temperature true value during estimation are similar to those of FIG. Fig.18 Same as Fig.18 By contrast, the estimated temperature error is reduced by calculating the magnet flux reference value based on the q-axis current. However, since the d-axis flux variation ΔΨd, which is different from the d-axis flux variation ΔΨd0 when Id is zero, is used directly for magnet temperature estimation, an estimated temperature error of about 20°C occurs.

[0112] Fig.21The figure shows an example of the magnet temperature estimation result obtained by the magnet temperature estimation unit 40. By correcting ΔΨd to ΔΨd_cmp equivalent to ΔΨd0 and calculating Ψd0_std based on the q-axis current value Iq, the current dependency of the d-axis magnetic flux variation ΔΨd caused by temperature change can be appropriately corrected, thereby reducing the estimated temperature error to about 5°C.

[0113] <Variation of Example 1> In the above description, the correction coefficient K and the magnet flux reference value Ψd0_std are calculated by separate calculation units. Based on equations (9) and (10), the magnetic flux change ratio KΨ is expressed by equation (12). KΨ=ΔΨd×K / Ψd0_std…(12) Here, K / Ψd0_std may be integrated into one conversion coefficient Kt, and the conversion coefficient Kt may be calculated from the d-axis current value and the q-axis current value. Fig. 22 The control block diagram of the part for calculating the flux change ratio based on the d-axis magnetic flux variation in this case is shown in . The conversion coefficient calculation unit 45 calculates the conversion coefficient Kt based on equation (12) and multiplies it by the d-axis magnetic flux variation ΔΨd to calculate the magnetic flux change ratio KΨ. [Example 2]

[0115] Embodiment 2 of the present invention will be described. The same reference numerals are given to the same structures as those in Embodiment 1, and detailed description thereof will be omitted.

[0116] The structure of the present embodiment may be the same as that of Embodiment 1 except for the following points. The present embodiment is directed to a control section 10 including a unit that uses information of a magnet temperature estimation value estimated by a magnet temperature estimation section 40 .

[0117] As a technical problem of electric motors having permanent magnets in the rotor, the permanent magnets have thermal demagnetization. When the temperature of the permanent magnets rises above a certain level, it sometimes causes irreversible demagnetization. When the permanent magnets are demagnetized, it is difficult to control the speed or torque of the motor to a desired value. In addition, in order to ensure the generation of torque, the current flowing through the motor or inverter is sometimes increased.

[0118] Fig.23 1 is a block diagram showing the configuration of a control unit 10a according to a second embodiment of the present invention. The control unit 10a according to the second embodiment includes means for using information of magnet temperature estimation.

[0119] exist Fig.23The structure shown includes a torque command value limiting unit 16, a d-axis current command value limiting unit 17 for limiting the d-axis current command value, and a q-axis current command value limiting unit 18 for limiting the q-axis current command value. The torque command value limiting unit 16 limits the torque command value based on the magnet temperature estimated value estimated by the magnet temperature estimating unit 40, with respect to the speed command value and the torque command obtained from the control unit 10a or obtained from the upper control system or other control system not shown in the figure.

[0120] Fig.24 1 is a diagram showing a configuration example 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 the command limit value based on the input magnet temperature estimated value.

[0121] For example, when the estimated magnet temperature value without the risk of thermal demagnetization is below the determination threshold Th, the command limit value is set to the same value as when the magnet temperature is sufficiently low. If the estimated magnet temperature value exceeds the determination threshold Th, the command limit value is reduced and output. When the estimated magnet temperature value is high and the risk of thermal demagnetization is high, the command value limit value can be set to zero, thereby setting the motor output to zero.

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

[0123] Thus, by configuring a unit including information using the magnet temperature estimation value estimated by the magnet temperature estimation unit 40, thermal demagnetization of the permanent magnet of the PM motor and excessive increase in current flowing through the PM motor or the inverter 30 can be prevented in advance. That is, a highly reliable motor control device can be provided. Here, it can be configured to include at least one 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. Although thermal demagnetization of the permanent magnet of the PM motor and excessive increase in current flowing through the PM motor or the inverter 30 can be prevented in advance by one command value limiting unit, multiple command value limiting units can be included for the purpose of ensuring redundancy or gradually reducing the output.

[0124] In addition, in the case where there is no means for estimating the permanent magnet temperature of the PM motor, in order to prevent thermal demagnetization, the continuous rated output is sometimes set to a small value with a margin relative to the maximum output. In the present embodiment, in the case where there is a means for limiting the command value based on the magnet temperature estimation value and suppressing the output, the continuous rated output can be set by minimizing the margin relative to the maximum output. That is, the continuous rated output can be increased while keeping the motor structure the same. [Example 3]

[0125] Embodiment 3 of the present invention will be described. The same reference numerals are given to the same structures as those of Embodiments 1 and 2, and detailed description thereof will be omitted.

[0126] The structure of the present embodiment may be the same as that of the embodiment 1 except for the following points. The present embodiment is directed to a control section 10 b including a unit that uses information of a magnet temperature estimated value estimated by a magnet temperature estimating section 40 .

[0127] When the torque of a motor having a permanent magnet in the rotor is controlled to a desired value, if the temperature of the magnet changes, the magnetic flux changes with the temperature, so there is a problem that the torque accuracy deteriorates without any countermeasures. When the torque accuracy deteriorates, for example, if the motor control device is installed in an electric vehicle system, the ride comfort and the accuracy of the autonomous driving may deteriorate.

[0128] Fig.25 1 is a block diagram showing the structure of the control unit 10b of the third embodiment of the present invention. The control unit 10b of the third embodiment includes a current command value calculation unit 11a, which calculates the d-axis current command value and the q-axis current command value using the magnet temperature estimated value estimated by the magnet temperature estimation unit 40 as input in addition to the torque command value.

[0129] The current command value calculation unit 11a calculates the d-axis current command value and the q-axis current command value so that when the magnet temperature is the reference temperature, the difference between the torque command value and the actual torque of the motor becomes smaller. When the magnet temperature is different from the reference temperature, a torque error will occur. Therefore, the d-axis current command value and the q-axis current command value are calculated based on the magnet temperature estimation value and the torque command value so that the torque error caused by the change in the magnet temperature becomes smaller.

[0130] Thus, by configuring the device to use information of the magnet temperature estimation value estimated by the magnet temperature estimation unit 40, it is possible to reduce the deterioration of torque accuracy due to the change in magnet temperature, and provide a motor control device with high torque accuracy.

[0131] As described above, the invention comprises: a q-axis voltage value calculation unit, which calculates the q-axis voltage value based on the voltage measurement value of the magnet motor or the voltage command value calculated so that the torque or current of the magnet motor is consistent with the command value; a d-axis magnetic flux variation amount calculation unit, which calculates the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value, i.e., the d-axis magnetic flux variation amount, by taking the q-axis voltage value, the electrical angular velocity, the d-axis current value, and the q-axis current value as input; and a d-axis magnetic flux variation amount correction unit, which calculates the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value, i.e., the d-axis magnetic flux variation amount correction amount, based on the d-axis current value and the q-axis current value. A d-axis magnetic flux variation after correction by calculating the q-axis current value; a magnet magnetic flux reference value calculation unit, which calculates the magnet magnetic flux reference value based on the q-axis current value; and a magnet temperature calculation unit, which calculates the magnet temperature estimation value based on the corrected d-axis magnetic flux variation and the magnet magnetic flux reference value, thereby correcting the current dependence of the magnetic flux variation caused by temperature changes when estimating the magnet temperature, improving the accuracy of magnet temperature estimation, and reducing the load and time of the adjustment work required in advance and the processing load during estimation.

[0132] The present invention is not limited to the above-mentioned embodiments, and includes various modified examples. For example, the above-mentioned embodiments are described in detail to facilitate understanding of the present invention, and are not limited to having all the structures described.

[0133] In addition, the above-mentioned structures, functions, processing units, processing procedures, etc. may also be implemented in hardware by designing a part or all of them, such as through integrated circuits, etc. In addition, the above-mentioned structures, functions, etc. may also be implemented by software by interpreting and executing programs that implement the respective functions through a processor.

[0134] In addition, signal lines and information lines necessary for explanation are shown, but it is not limited to showing all control lines and information lines necessary for the product. In addition, each of the above structures, functions, processing units, processing processes, etc. does not necessarily have to be physically located in the same location, and for example, a part may be located in a network or cloud through communication, etc.

[0135] In addition, although the motor is described as an inner rotor structure in which the rotor is arranged inside the stator, it can also be an outer rotor structure. In addition, the motor can be a radial gap motor or an axial gap motor. In addition to PMSM, a synchronous motor or SRM equipped with a magnet can also be used. Description of symbols

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

Claims

1. A motor control device, comprising a control unit for controlling a motor having a permanent magnet, characterized in that: The control unit includes a magnet temperature estimating unit, The magnet temperature estimation unit inputs: a q-axis voltage value calculated based on any one of the rotation speed command value of the motor and the torque command value of the motor, or calculated based on the 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 the command value, and estimates the temperature of the permanent magnet. The magnet temperature estimating unit comprises: a d-axis magnetic flux variation calculation unit which inputs the q-axis voltage value, the electrical angular velocity, the d-axis current value, and the q-axis current value, and calculates the d-axis magnetic flux variation which is the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value; and a d-axis magnetic flux variation correction unit which calculates a corrected d-axis magnetic flux variation by correcting the d-axis magnetic flux variation 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; and A magnet temperature calculation unit calculates an estimated magnet temperature value of the permanent magnet based on the corrected d-axis magnetic flux variation and the magnet magnetic flux reference value.

2. The motor control device according to claim 1, characterized in that: The d-axis magnetic flux variation calculation unit includes: a d-axis magnetic flux calculation unit that inputs 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 inputs the d-axis current value and the q-axis current value and calculates the d-axis magnetic flux reference value. The d-axis magnetic flux variation amount is calculated based on a difference between the d-axis magnetic flux and the d-axis magnetic flux reference value.

3. The motor control device according to claim 1, characterized in that: The d-axis magnetic flux variation 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. The d-axis magnetic flux variation correction unit calculates the corrected d-axis magnetic flux variation based on the d-axis magnetic flux variation and the correction coefficient.

4. The motor control device according to claim 1, characterized in that: The magnet temperature calculation unit includes a magnet temperature conversion unit that receives as input a magnetic flux change ratio calculated based on the corrected d-axis magnetic flux variation and the magnet magnetic flux reference value, and calculates the magnet temperature estimation value.

5. The motor control device according to any one of claims 1 to 4, characterized in that: The control unit includes a command value limiter that limits a maximum value and a minimum value of the torque command value, the d-axis current value, or the q-axis current value based on the magnet temperature estimation value.

6. The motor control device according to any one of claims 1 to 4, 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.

Images