JP2024036042A - motor control device - Google Patents

Abstract

The present invention improves the accuracy of magnet temperature estimation by correcting the current dependence of magnetic flux variation due to temperature change when estimating magnet temperature. [Solution] A motor control unit 10 calculates a q-axis voltage command value calculated based on either a motor rotation speed command value or a torque command value, an electrical angular velocity, and a detected current value. A magnet temperature estimation unit 40 is provided which inputs the d-axis current detection value and the q-axis current detection value and estimates the temperature of the permanent magnet. The magnet temperature estimating unit 40 includes a d-axis magnetic flux variation calculation unit 41 that receives the q-axis voltage command value, electrical angular velocity, d-axis current detection value, and q-axis current detection value and calculates the d-axis magnetic flux variation; A d-axis magnetic flux fluctuation amount correction unit 42 that calculates a corrected d-axis magnetic flux fluctuation amount after correcting the axial magnetic flux fluctuation amount, a magnet magnetic flux reference value calculation unit 43 that calculates a magnet magnetic flux reference value, and a d-axis magnetic flux fluctuation amount after correction. The magnet temperature calculation unit 44 is provided to calculate an estimated magnet temperature value of the permanent magnet based on the magnet flux reference value and the magnet flux reference value. [Selection diagram] Figure 1

Description

The present invention relates to a motor control device.

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

Patent Document 1 discloses a driving device for a permanent magnet synchronous motor that estimates the variation amount of magnet magnetic flux between different times based on a voltage command value and outputs an estimated magnet temperature variation amount corresponding to the magnet magnetic flux variation amount. There is.

Further, Patent Document 2 discloses a method for estimating the magnet temperature of a motor, which changes the target current value, calculates the magnet magnetic flux based on the d-axis magnetic flux linkage, and estimates the magnet temperature according to the calculated magnet magnetic flux. are doing.

JP 2021-2949 Publication JP 2021-16226 Publication

The technique described in Patent Document 1 aims to accurately estimate magnet magnetic flux or magnet temperature by eliminating the influence of constant errors between individual motors due to manufacturing variations in motors. Patent Document 1 provides a method for calculating a d-axis magnetic flux error from 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 a d-axis magnetic flux error at a reference temperature. Calculate φ0_err, calculate the d-axis magnetic flux error φ1_err when the magnet temperature changes from the reference temperature, calculate the amount of variation in magnet magnetic flux from the difference between φ0_err and φ1_err, and estimate the amount of magnet temperature variation corresponding to the amount of magnet magnetic flux variation. A drive device for a permanent magnet synchronous motor that outputs a value is disclosed.

In Patent Document 1, the variation amount of the d-axis magnetic flux calculated from the difference between φ0_err and φ1_err when a certain d-axis current and q-axis current are present is directly used as the magnet magnetic flux variation amount. The amount of variation in d-axis magnetic flux and magnet magnetic flux due to magnet temperature change has current dependence that differs depending on d-axis current and q-axis current. There is room for improvement because an error occurs in the estimated value of the variation amount and an error also occurs in the estimated value of the magnet temperature.

Patent Document 2 discloses a motor magnet temperature estimation method that calculates d-axis magnetic flux before and after changing a target current, calculates magnet magnetic flux based on each d-axis magnetic flux, and estimates magnet temperature according to the calculated magnet magnetic flux. The method is disclosed. In Patent Document 2, when estimating the magnet temperature from the magnet magnetic flux, a table showing the correspondence relationship between the parameters of the magnet magnetic flux, d-axis current, and q-axis current and the magnet temperature is used, and the amount of magnetic flux fluctuation due to temperature change is estimated. Magnet temperature is estimated by taking current dependence into consideration, but since a table with three parameter input is used, the number of table data becomes large, and the measurement work time to create the table and the processing load of table reference are large. So, there is room for improvement.

An object of the present invention is to provide a motor control device that improves magnet temperature estimation accuracy by correcting current dependence of magnetic flux variation due to temperature change when estimating magnet temperature.

In order to achieve the above object, a motor control device of the present invention includes a control unit that controls a motor having a permanent magnet, wherein the control unit controls a rotational speed command value of the motor, a torque of the motor a q-axis voltage value calculated based on either a command value or a voltage detection value of the motor; an electrical angular velocity calculated based on the electrical angle of the motor; and a voltage detection of the motor. a magnet temperature estimating unit that inputs a d-axis current value and a q-axis current value calculated based on a value or a current detected value of the motor, or a command value, and estimates the temperature of the permanent magnet, The magnet temperature estimator inputs the q-axis voltage value, the electrical angular velocity, the d-axis current value, and the q-axis current value, and calculates a d-axis magnetic flux fluctuation amount that is the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value. a d-axis magnetic flux fluctuation amount calculation unit that calculates a corrected d-axis magnetic flux fluctuation amount that corrects the d-axis magnetic flux fluctuation amount based on the d-axis current value and the q-axis current value; a correction section, a magnet magnetic flux reference value calculation section that calculates a magnet magnetic flux reference value based on the q-axis current value, and a magnet magnetic flux reference value calculation section that calculates a magnet magnetic flux reference value of the permanent magnet based on the corrected d-axis magnetic flux fluctuation amount and the magnet magnetic flux reference value. The present invention is characterized in that it includes a magnet temperature calculation section that calculates an estimated temperature value.

According to the present invention, the accuracy of magnet temperature estimation can be improved by correcting the current dependence of the amount of magnetic flux variation due to temperature change when estimating magnet temperature.

Problems, configurations, and effects other than those described above will become clear from the description of the embodiments below.

1 is a schematic configuration diagram of a motor control device 100 according to a first embodiment of the present invention. 2 is a diagram schematically showing the structure of a PM motor 20. FIG. 3 is a diagram showing the relationship between the rotor position θd and the phase of each winding 25 of the stator 21. FIG. 3 is a block diagram showing the configuration of an inverter 30 and a current detection section 50. FIG. FIG. 3 is a diagram showing an AC voltage command value and a triangular wave carrier signal for generating a drive signal. 3 is a diagram showing an example of the configuration of a voltage command value calculation section 12. FIG. FIG. 3 is a diagram showing the relationship between d-axis magnetic flux and d-axis current at a certain q-axis current. FIG. 4 is a control block diagram of a magnet temperature estimating section 40. FIG. 3 is a block diagram including a voltage sensor 70 that measures the output voltage of an inverter 30. FIG. FIG. 2 is a control block diagram of a d-axis magnetic flux fluctuation amount calculating section 41. FIG. FIG. 7 is a diagram showing an example of the relationship between the d-axis magnetic flux reference value Ψd_std and the d-axis current value Id and the q-axis current value Iq, which is stored in the d-axis magnetic flux reference value calculation unit 412 as a table or a mathematical formula. It is a figure which shows an example of the relationship between q-axis current value Iq and magnet magnetic flux reference value Ψd0_std. FIG. 4 is a control block diagram of a d-axis magnetic flux fluctuation amount correction section 42. FIG. 7 is a diagram illustrating an example of a relationship between a correction coefficient K and a d-axis current value Id and a q-axis current value Iq, which is stored as a table or a formula in a correction coefficient calculation unit 421. FIG. 4 is a control block diagram of a magnet temperature calculation section 44. FIG. FIG. 7 is a diagram illustrating an example of the relationship between the estimated magnet temperature value Tm_est and the magnetic flux change ratio KΨ, which is stored in the magnet temperature conversion unit 441 as a table or a mathematical formula. FIG. 7 is a control block diagram showing a configuration example of a magnet temperature estimating section in a case where a d-axis magnetic flux fluctuation amount correction section is not provided and a magnet magnetic flux reference value is a constant. FIG. 7 is a diagram illustrating an example of a magnet temperature estimation error of a magnet temperature estimator in a case where a d-axis magnetic flux fluctuation amount correction section is not provided and a magnet magnetic flux reference value is a constant. FIG. 7 is a control block diagram illustrating a configuration example of a magnet temperature estimation section in a case where a d-axis magnetic flux fluctuation amount correction section is not provided. FIG. 7 is a diagram illustrating an example of a magnet temperature estimation error of a magnet temperature estimator in a case where a d-axis magnetic flux fluctuation amount correction section is not provided. It is a figure which shows the example of magnet temperature estimation error of a magnet temperature estimation part. 3 is a control block diagram showing a modification of the first embodiment. FIG. It is a block diagram showing the composition of control part 10a concerning Example 2 of the present invention. 2 is a diagram illustrating a configuration example of a torque command value limiting section 16, a d-axis current command value limiting section 17, and a q-axis current command value limiting section 18. FIG. It is a block diagram showing the composition of control part 10b concerning Example 3 of the present invention.

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

The various constituent elements of the present invention do not necessarily have to exist individually and independently; a plurality of constituent elements may be formed as a single member, or one constituent element may be formed from a plurality of members. , it is allowed that a certain component is a part of another component, that a part of a certain component overlaps with a part of another component, etc.

<Schematic configuration of motor control device>
FIG. 1 is a schematic configuration diagram of a motor control device 100 according to a first embodiment of the present invention. The motor control device 100 includes a control section 10, a PM motor 20, an inverter 30, a current detection means 50, and an angle sensor 60 such as a resolver or 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.

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

The inverter 30 has a DC voltage source 120 (see FIG. 4) such as a battery, and a bridge circuit including a switching element, and outputs a voltage by switching the switching element according to an input drive signal. If the switching operation of the switching element is assumed to ideally switch without delay, the voltage output from the inverter 30 will be a pulse voltage. Using the well-known concept of pulse width modulation, the pulsed voltage can be viewed as an alternating voltage.

In addition, in pulse width modulation, it is common to set the period at which the switching element is turned on and off, that is, the switching frequency, to be sufficiently high relative to the frequency of the equivalent AC voltage (corresponding to the rotational frequency of a single-phase motor in this case). It is. However, it is also possible to consider the fundamental wave component of the pulsed voltage. For example, when the switching frequency is close to the rotational frequency of the PM motor, such as 1 to 3 times, it can be considered that the fundamental wave component of the pulsed voltage is applied to the PM motor 20. Therefore, in this specification, the following description will be made assuming that the output voltage of the inverter 30 has an AC waveform.

Note that instead of using a DC voltage source, a configuration may be used in which an AC power source is converted into DC power by rectification or the like. Alternatively, a configuration using a DC/DC converter that controls a DC voltage source of a certain voltage to a different voltage may be used.

The control unit 10 includes, as a configuration example, 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.

The coordinate conversion unit 13 inputs the current detection value, which is information on the current flowing through the PM motor 20 obtained by the current detection means 50, and the motor electrical angle detection value obtained by the angle sensor 60, and converts the defined value from the three-phase UVW axis. is converted into a dq-axis, which will be described later, and outputs a d-axis current detection value (d-axis current value) and a q-axis current detection value (q-axis current value).

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.

The current command value calculation unit 11 inputs a rotation speed command value or a torque command value, and outputs a d-axis current command value and a q-axis current command value.

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

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

In FIG. 1, the rotational speed command value and the torque command value are shown in the control unit 10, but they may be obtained from a higher-level control system or another control system (not shown), for example.

<Structure example of PM motor 20>
FIG. 2 is a diagram schematically showing the structure of the PM motor 20. As shown in FIG. The PM motor 20 includes a stator 21 and a rotor 22 arranged on the inner peripheral side of the stator 21. The stator 21 has a plurality of stator magnetic poles 28 each having a winding (coil) 25 wound around a stator core (stator iron core) 26 . The rotor 22 has permanent magnets 27 .

FIG. 2 shows an example in which the number of magnetic poles of the stator 21 (also referred to as the number of slots) is six, and the number of magnetic poles of the rotor 22 is two. The number of magnetic poles of the stator 21 and the rotor 22 can be freely selected, and the number of magnetic poles of the stator 21 and the rotor 22 may be equal. The configuration may have a different number of . Furthermore, there is no problem in connecting the plurality of windings, whether they are connected in parallel or in series. In this embodiment, the windings 25 of the opposing stator magnetic poles 28 are connected in series to constitute one phase, and the PM motor 20 will be described as an example constituted by three-phase windings.

The stator magnetic pole 28 generates a magnetic pole in the manner of an electromagnet by passing a current through the winding 25, and the polarity (N pole, S pole) can be changed depending on the direction of the current in the winding 25. In this embodiment, the rotation angle of the rotor 22 ( The rotational angular position) is defined as zero degrees. Note that from now on, the rotational angular position of the rotor will be referred to as rotor position θd. If there are multiple stator magnetic poles 28, one of them is determined as the reference position. In this embodiment, the winding 25 on the right side of FIG. 2 (the winding closest to the U-phase) will be described as a reference position. In this application, the direction in which the rotor 22 rotates counterclockwise is defined as normal rotation.

In the processing within the motor control device 100, information on the rotor position θd of the rotor 22 of the PM motor 20 is used, but the description will be made assuming that the angle sensor 60 is configured to detect position information using a resolver, an encoder, or the like. Of course, a configuration may also be used in which the position is obtained by position sensorless control using position estimating means that outputs the estimated rotation angle position of the PM motor 20 from the current flowing through the PM motor 20 and the voltage applied to the PM motor 20.

<Explanation of coordinate axes>
Here, the definition of the coordinate axes will be explained. FIG. 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 the UVW are arranged with a difference of 120 electrical degrees. The d-q axis is defined as the main magnetic flux direction of the permanent magnet provided in the rotor 22 as the d-axis, and the q-axis electrically extending 90 degrees (electrical angle 90 degrees) from the d-axis in the rotational direction. The dq axes are a rotating coordinate system. The definition of the d-axis can also be expressed as the rotational angular position where the magnetic flux of the permanent magnet 27 interlinking with the reference winding 25 is maximum.

<Inverter 30>
Next, the configurations of the inverter 30 and the current detection section 50 will be described with reference to the block diagram shown in FIG. FIG. 4 is a block diagram showing the configuration of the inverter 30 and the current detection section 50.

The inverter 30 includes an inverter module 131, a DC voltage source 120, and a gate driver circuit 123, as shown in FIG. Here, the output of the DC voltage source 120 is assumed to be the DC voltage Edc.

The inverter module 131 includes switching elements 32a to 32f (for example, semiconductor switching elements such as IGBTs and MOS-FETs) and a freewheeling diode connected in parallel to these switching elements. Note that the switching elements 32a to 32f are collectively referred to as "switching elements 32."

A shunt resistor 135 is connected in series to the DC voltage source 120. This protects the switching element 32 from excessive current flow.

These switching elements 32 constitute upper and lower arms of each phase by connecting two sets of switching elements 32 in series. In the example of FIG. 4, the switching elements 32a and 32b constitute the U-phase, the switching elements 32c and 32d constitute the V-phase, and the switching elements 32e and 32f constitute the W-phase upper and lower arms. The connection point of the upper and lower arms of each phase is connected to the PM motor 20.

The gate driver circuit 123 receives a pulse-like drive signal (details will be described later) output from the PWM signal generation section 14 shown in FIG. 1, and outputs drive signals 34a to 34f based on this. A known technique can be used to generate the drive signal, and an example thereof is shown in FIG.

FIG. 5 is a diagram showing an AC voltage command value and a triangular wave carrier signal for generating a drive signal. As shown in FIG. 5, an upper arm drive signal Gp and a lower arm drive signal Gn are generated as shown in the figure from the magnitude relationship between the triangular wave carrier signal and the voltage command value of each phase.

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

Depending on the switching state of the upper and lower arms, the voltage of each phase of the inverter 30 is either DC voltage Edc or zero voltage. Since the inverter 30 performs switching at a frequency sufficiently higher than the frequency of the AC voltage appearing at the PM motor 20, the output voltage of each phase of the inverter 30 can be adjusted by changing the switching ratio (switching duty) of the upper and lower arms. Can be adjusted freely. That is, a three-phase AC voltage of any frequency can be applied to the PM motor 20, thereby realizing variable speed drive and torque control of the PM motor 20.

<Current detection means 50>
The current detection means 50 detects the currents flowing in the U phase and W phase among the three-phase alternating currents flowing from the inverter 30 to the PM motor 20, and outputs the results as alternating current detection values Iu and Iw. Of course, there is no problem in detecting the alternating currents of all phases, but according to Kirchhoff's first law, if two of the three phases can be detected, the other one phase can be calculated from the detected two phases. The lower arm of the inverter module 131 can be provided with a current detection means 50 such as a CT (current transformer).

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

<How to drive PM motor 20>
When driving a motor having a permanent magnet 27 in the rotor 22, if the magnetic flux by the winding 25 is generated at a position 90 electrical degrees ahead of the magnetic flux by the permanent magnet 27 in the direction of rotation, the maximum current can be achieved with the minimum current. of torque can be obtained. By driving in this manner, not only the motor can be made smaller and lighter, but also the inverter 30 can be made smaller.

Regarding the d-axis and q-axis mentioned above, the d-axis can also be said to be the magnet magnetic flux axis, and the q-axis can be said to be the winding magnetic flux axis, and it is particularly important to appropriately control the current on the q-axis. Separating the current flowing through the motor into a field component and a torque component on the rotating coordinate axis, and controlling the phase and magnitude of the voltage in order to control the motor's rotational speed or torque is generally called vector control. . Although the PM motor is controlled on the dq axes as a driving method, a known coordinate conversion technique can be used to convert the three-phase UVW axes to the dq axes.

As the voltage command value calculation section 12, there is a structure and means described in, for example, Japanese Patent Laid-Open No. 2005-39912. An example of the configuration of the voltage command value calculation unit 12 using this is shown in FIG.

The voltage command value calculation unit 12 in FIG. 6 inputs the d-axis and q-axis current command values (Id ^* and Iq ^* ) calculated by the current command value calculation unit 11 and the electrical angular velocity ωe, and calculates the equation (1), ( 2) Perform vector calculation as shown in the formula to obtain the d-axis voltage command value Vd ^* and the q-axis voltage command value Vq ^* .
Vd ^* =R×Id ^** -ωe×Lq×Iq ^** ＿ _fil …(1)
Vq ^* =R×Iq ^** +ωe×Ld×Id ^** ＿ _fil + ωe×Ke …(2)
In addition, in equations (1) and (2), R is the winding resistance value per phase of the PM motor 20 (electric motor), Ld is the d-axis inductance, Lq is the q-axis inductance, and Ke is the induced voltage constant. It is.

In order to cause the dq-axis current to flow as instructed, a configuration of a d-axis current controller 114a and a q-axis current controller 114b is used in FIG. In the d-axis current controller 114a having the circuit configuration of FIG. 6, the subtracter 91d subtracts the d-axis current detected value Idc from the d-axis current command value Id ^* . Proportional units 92c and 92d multiply this subtraction result by predetermined gains Kp_acrd and Ki_acrd, respectively. The integrator 94c integrates the output result of the proportional device 92d, ie, “Ki_acrd×(Id ^* −Idc)”. Adder 90b adds the multiplication result of proportional device 92c and the integration result of integrator 94c, and outputs the addition result as d-axis current command value Id ^** .

Similarly, in the q-axis current controller 114b, the subtracter 91e subtracts the qc-axis current detection value Iqc from the q-axis current command value Iq ^* . Proportional units 92e and 92f multiply this subtraction result by gains Kp_acrq and Ki_acrq, respectively. The integrator 94d integrates the output result of the proportional device 92f, ie, “Ki_acrq×(Iq ^* −Iqc)”. Adder 90c adds the multiplication result of proportional device 92e and the integration result of integrator 94d, and outputs the addition result as q-axis current command value Iq ^** . In this way, the d-axis current controller 14a and the q-axis current controller 14b each constitute a proportional-integral calculator.

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 term on the right side of equations (1) and (2). .

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

The subtracter 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 equation (1). The adder 90d obtains the q-axis voltage command value Vq* of equation (2) by calculating the sum of the output of the multiplier 92i, the output of the multiplier 92j, and the output of the multiplier 92k.

In the circuit configuration example of FIG. 6, in the voltage command value calculation unit 12, a d-axis current controller 114a and a q-axis current controller 114b are connected in series to the voltage calculation, and a cutoff corresponding to the electric time constant of the motor The feature is that there are first-order lag filters (low-pass filters) 98a and 98b having frequencies. Since the inverse model of the electric motor is established by these, there is an effect that ideal vector control can be realized even when there is a restriction on the calculation cycle of the control section 10.

<Issues of increasing torque accuracy>
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, if the temperature of the magnet changes, the magnetic flux changes depending on the temperature, so if no countermeasure is taken. However, there is a problem that torque accuracy deteriorates.

If the magnet temperature can be measured, torque accuracy can be improved by adjusting the current command value depending on the temperature. However, it is difficult to directly connect the temperature sensor to the magnets present in the rotor due to durability and productivity issues. Therefore, an effective measure is to estimate the magnet temperature. Regarding estimation of the magnet temperature, there are configurations and means described in, for example, the above-mentioned Patent Document 1 (Japanese Patent Laid-Open No. 2021-2949) and Patent Document 2 (Japanese Patent Laid-Open No. 2021-16226).

In Patent Document 1, as mentioned in the problem section, the amount of variation in magnetic flux due to magnet temperature change has current dependence that differs depending on the d-axis current and the q-axis current. Estimation when is non-zero causes a problem in that an error occurs in the estimated value of the variation amount of the magnet magnetic flux, and an error also occurs in the estimated value of the magnet temperature.

Furthermore, in Patent Document 2, when estimating the magnet temperature from the magnet magnetic flux, a table showing the correspondence between the parameters of the magnet magnetic flux, d-axis current, and q-axis current and the magnet temperature is used, and magnetic flux fluctuations due to temperature changes are used. The magnet temperature is estimated by taking into account the current dependence of the quantity, but since a table with three parameter input is used, the number of table data becomes large, and the measurement work time to create the table and the processing load of table reference are large. There is a problem. Hereinafter, means for solving this problem will be explained.

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

<Outline of operation of magnet temperature estimation in the present invention>
The q-axis voltage equation in a steady state can be expressed by the following equation if the differential term is ignored and each value is taken as an average value.

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

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

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

First, the d-axis magnetic flux reference value Ψd_std, which is the d-axis magnetic flux at the reference temperature, is measured and stored in advance. This corresponds to measuring and storing the d-axis magnetic flux curve at the reference temperature in FIG. 7, but as mentioned above, the d-axis magnetic flux also changes depending on the q-axis current value Iq, so The d-axis magnetic flux is measured and stored as Ψd_std.

Next, the operation when estimating the magnet temperature will be explained. When the magnet temperature at the time of estimation is different from the reference temperature, the d-axis magnetic flux curve at the time of estimation is different from the d-axis magnetic flux curve at the reference temperature, as shown in FIG. In motors that use magnets such as neodymium magnets whose magnetic flux increases as the magnet temperature decreases, if the magnet temperature at the time of estimation is lower than the reference temperature, the d-axis magnetic flux curve at the time of estimation will change to the reference temperature as shown in Figure 7. When the d-axis magnetic flux curve moves in the positive direction of the d-axis magnetic flux axis. 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 moves in the negative direction of the d-axis magnetic flux axis from the d-axis magnetic flux curve at the reference temperature.

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

Ψd=(Vq ^* -Vdrop_q)/ωe...(5)
The q-axis voltage drop component Vdrop_q includes voltage drops due to various factors, but considering only the voltage drop due to all resistance components such as the windings, cables, and switching elements 32, which are the most dominant components, the following equation ( 6) can be calculated.

Vdrop_q=Rall×Iq…(6)
Here, Rall is the total resistance value including the winding, cable, switching element 32, etc. The total resistance value Rall may be determined by measurement, or may be calculated from the conductor cross-sectional area and length of the winding and cable, and the current-voltage characteristics of the switching element.

A pre-stored d-axis magnetic flux reference value Ψd_std is calculated based on the estimated d-axis current and q-axis current. Then, the d-axis magnetic flux fluctuation amount ΔΨd is calculated from the following equation (7).

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

Therefore, the d-axis magnetic flux fluctuation amount ΔΨd at the d-axis current value Id and the q-axis current value Iq at the time of estimation is corrected so that it corresponds to the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero. The corrected d-axis magnetic flux variation amount is defined as the corrected d-axis magnetic flux variation amount ΔΨd_cmp. ΔΨd_cmp is calculated from ΔΨd, Id, and Iq. It is desirable that the difference between ΔΨd_cmp and ΔΨd0 is small.

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

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

At the time of estimation, ΔΨd_cmp is calculated using the following equation (9).

ΔΨd_cmp=ΔΨd×K…(9)
If the 2nd temperature condition when calculating the correction coefficient K, the reference temperature, and the temperature at the time of estimation match, ΔΨd_cmp will match ΔΨd0, but the 2nd temperature condition when calculating the correction coefficient K and the estimated reference temperature When the temperature is different, ΔΨd_cmp does not match ΔΨd0. However, regardless of the selection of the two temperature conditions, the correction coefficient K, which is the ratio of ΔΨd0 and ΔΨd, remains almost constant. Even if they do not match, the difference between ΔΨd_cmp and ΔΨd0 is small.

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

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

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

KΨ=ΔΨd_cmp/Ψd0_std…(10)
An estimated magnet temperature value is calculated from the relationship between the magnetic flux change ratio KΨ and the magnet temperature. The correspondence relationship between the magnetic flux change ratio KΨ and the magnet temperature is stored by changing the magnet temperature in advance and calculating the magnetic flux change ratio KΨ by measuring or electromagnetic field simulation, and implementing it as a table. Alternatively, the magnet temperature may be calculated using a formula using the magnetic flux change ratio KΨ as input.

The outline of the magnet temperature estimation operation in the present invention has been described above. Next, details of the configuration and operation of the magnet temperature estimating section 40 will be explained.

<Configuration and operation of magnet temperature estimator>
FIG. 8 is a control block diagram of the magnet temperature estimation section 40. FIG. 9 is a block diagram including a voltage sensor 70 that measures the output voltage of the inverter 30. The operation when estimating the magnet temperature while driving the motor will be described below.

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

First, regarding the d-axis current value and q-axis current value, either use the d-axis current detection value and q-axis current detection value as shown in the connection in Figure 1, or set the d-axis current command value and q-axis current based on the command value. It may also be used as a command value. In addition, the q-axis voltage value may be set as the q-axis voltage command value as shown in the connection in FIG. input, the voltage detection value is converted from the three-phase UVW axis to the dq axis by the coordinate conversion unit 13a, and the d-axis voltage detection value and the q-axis voltage detection value are obtained. It's good as well.

The d-axis magnetic flux fluctuation amount calculation unit 41 calculates the d-axis magnetic flux fluctuation amount ΔΨd from the q-axis voltage value Vq, the electrical angular velocity ωe, the d-axis current value Id, and the q-axis current value Iq. ΔΨd is the difference between the estimated d-axis magnetic flux Ψd and the d-axis magnetic flux reference value Ψd_std, which is the d-axis magnetic flux at the reference temperature.

Next, the d-axis magnetic flux fluctuation amount correction unit corrects the d-axis magnetic flux fluctuation amount ΔΨd to the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero based on the d-axis current value Id and the q-axis current value Iq. The rear d-axis magnetic flux fluctuation amount ΔΨd_cmp is calculated.

The magnet magnetic flux reference value calculation unit 43 calculates the magnet magnetic flux reference value Ψd0_std based on the q-axis current value Iq.

Finally, the magnet temperature calculation unit 44 calculates the estimated magnet temperature value Tm_est from the corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std.

<Configuration and operation of d-axis magnetic flux fluctuation calculation section>
FIG. 10 is a control block diagram of the d-axis magnetic flux fluctuation amount calculating section 41. The d-axis magnetic flux calculation unit 411 calculates the d-axis magnetic flux Ψd by inputting the q-axis voltage value Vq, the electrical angular velocity ωe, and the q-axis current value Iq.

One method for calculating the d-axis magnetic flux Ψd is a method based on equations (5) and (6). Furthermore, as shown in equation (6), not only the voltage drop due to the total resistance component Rall among the voltage drop components, but also the nonlinear voltage drop component with respect to the q-axis current value Iq of the switching element 32 is added to Vdrop_q. , the calculation accuracy of the d-axis magnetic flux Ψd can be improved. In this case, a table or formula is used in which the q-axis current value Iq is input and the voltage drop across the switching element 32 is output. In addition, the error voltage caused by the dead time and the error voltage caused by the PWM method are input to the q-axis current value Iq, the d-axis current value Id (not shown), and the DC It may be calculated based on the voltage Edc and the switching frequency fsw and added to Vdrop_q.

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. Any calculation method may be used as long as the d-axis magnetic flux reference value Ψd_std can be calculated from the d-axis current value Id and the q-axis current value Iq.

As an example of a method for calculating the d-axis magnetic flux reference value Ψd_std, the d-axis magnetic flux for the d-axis current value Id and the q-axis current value Iq is calculated and stored in advance by measurement or electromagnetic field simulation, and Id and Iq are set as parameters. There is a configuration in which a table of Ψd_std is created and used during estimation. Alternatively, 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 may be expressed mathematically and used at the time of estimation. As an example of using a mathematical formula, there is a configuration in which the relationship between the d-axis inductance Ld_std and the d-axis current value Id and the q-axis current value Iq at a reference temperature is memorized, and the d-axis magnetic flux reference value Ψd_std is calculated using the following equation (11). There is.

Ψd_std=Ld_std×Id+Ψd0_std…(11)
In addition, when the magnet temperature can be regarded as the reference temperature while the motor is being driven, the d-axis magnetic flux Ψd output by the d-axis magnetic flux calculation unit at that time is the d-axis magnetic flux reference for the d-axis current value Id and the q-axis current value Iq at that time. It is also possible to store the value Ψd_std, update the Ψd_std table, and update the formula for calculating Ψd_std.

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).

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

Furthermore, the d-axis magnetic flux also changes depending on the q-axis current value. If the d-axis magnetic flux reference value is calculated with the magnet magnetic flux constant or the d-axis inductance constant, an error will occur in the d-axis magnetic flux fluctuation amount ΔΨd, and an error will also occur in the estimated magnet temperature value. By storing the d-axis magnetic flux reference value Ψd_std, which changes depending on the d-axis current and the q-axis current, and calculating it based on the d-axis current value Id and the q-axis current value Iq at the time of estimation, the d-axis magnetic flux fluctuation amount ΔΨd can be calculated. Can be calculated accurately.

<Configuration and operation of magnet magnetic flux reference value calculation section>
The magnet magnetic flux reference value calculation unit 43 calculates the magnet magnetic flux reference value Ψd0_std based on the q-axis current value Iq. FIG. 12 shows an example of the relationship between the q-axis current value Iq and the magnet magnetic flux reference value Ψd0_std. The magnet magnetic flux reference value calculation unit 43 does not care about the calculation method as long as it can calculate the magnet magnetic flux reference value Ψd0_std from the q-axis current value Iq.

As an example of a method for calculating the magnet magnetic flux reference value Ψd0_std, the magnet magnetic flux reference value Ψd0_std for the q-axis current value Iq at the reference temperature is calculated and stored in advance by measurement or electromagnetic field simulation, and a table of Ψd0_std in which Iq is a parameter is created. There is a configuration that is created and used during estimation. Alternatively, the relationship between the magnet magnetic flux reference value Ψd0_std and the q-axis current value Iq may be expressed mathematically and used at the time of estimation. Further, the magnet magnetic flux reference value Ψd0_std is the same value as the magnetic flux value when the d-axis current value Id in the reference d-axis magnetic flux Ψd_std stored in the d-axis magnetic flux reference value calculation unit 412 is zero. Therefore, when calculating the reference d-axis magnetic flux Ψd_std in the d-axis magnetic flux reference value calculation unit 412, the magnetic flux value when the d-axis current value Id is zero is calculated, and the magnet magnetic flux which is the output of the magnet magnetic flux reference value calculation unit 43 is calculated. The reference value Ψd0_std may also be used.

<Configuration and operation of the d-axis magnetic flux fluctuation amount correction section>
FIG. 13 is a control block diagram of the d-axis magnetic flux fluctuation amount correction section 42. Based on the estimated d-axis current value Id and q-axis current value Iq, a corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp, which is equivalent to the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero, is calculated from the d-axis magnetic flux fluctuation amount ΔΨd. The correction coefficient calculation unit 421 calculates a correction coefficient K by inputting the d-axis current value Id and the q-axis current value Iq. The correction coefficient calculation unit 421 may use any calculation method as long as it can calculate the correction coefficient K from the d-axis current value Id and the q-axis current value Iq.

As an example of how to calculate the correction coefficient K, from ΔΨd0 and ΔΨd calculated by measurement or electromagnetic field simulation for the d-axis current value Id and the q-axis current value Iq under two predetermined temperature conditions, formula (8) is used. There is a configuration in which a correction coefficient K is calculated and stored based on the above, and a table of correction coefficients K is created in which Id and Iq are parameters, and the table is used at the time of estimation. Alternatively, the relationship between the correction coefficient K and the d-axis current value Id and the q-axis current value Iq may be expressed mathematically and used at the time of estimation.

Finally, the d-axis magnetic flux fluctuation amount correction unit 42 calculates the corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp based on equation (9).

FIG. 14 shows an example of the relationship between the correction coefficient K and the d-axis current value Id and the q-axis current value Iq, which is stored as a table or a formula in the correction coefficient calculation unit 421. Since the correction coefficient K is the ratio of the d-axis magnetic flux fluctuation amount ΔΨd to the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero, the correction coefficient K is 1 on the straight line where the d-axis current value Id is zero. Characteristics vary depending on the structure of the motor, but in the case of a motor in which the absolute value of the d-axis magnetic flux fluctuation amount ΔΨd increases as the d-axis current becomes more negative, as shown in Figure 14, the more negative the d-axis current becomes, the greater the correction becomes. The coefficient K becomes smaller. Furthermore, since the d-axis magnetic flux fluctuation amount ΔΨd also changes depending on the q-axis current, the correction coefficient K also takes a different value depending on the q-axis current.

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

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

The correspondence relationship between the magnetic flux change ratio KΨ and the magnet temperature is stored by changing the magnet temperature in advance and calculating the magnetic flux change ratio KΨ by measuring or electromagnetic field simulation, and implementing it as a table. Alternatively, the magnet temperature may be calculated using a formula using the magnetic flux change ratio KΨ as input.

FIG. 16 shows an example of the relationship between the estimated magnet temperature value Tm_est and the magnetic flux change ratio KΨ, which is stored as a table or a formula in the magnet temperature conversion unit 441. When the magnetic flux change ratio KΨ is zero, the magnetic flux change due to the magnet temperature change is zero, so the magnet temperature estimated value Tm_est is equal to the reference magnet temperature. The magnetic flux change ratio with respect to temperature change varies depending on the temperature characteristics of the magnet. When a neodymium magnet has a characteristic in which the magnetic flux decreases as the temperature increases, as shown in FIG. 16, as the magnetic flux change ratio increases in the positive direction, the estimated magnet temperature value decreases.

Although we have described a configuration in which the magnetic flux change ratio KΨ, which is the ratio between the corrected d-axis magnetic flux fluctuation amount ΔΨd_cmp and the magnet magnetic flux reference value Ψd0_std, is calculated and the magnet temperature conversion unit 441 calculates the magnet temperature estimated value Tm_est, Tm_est is different. The calculation method may be used to calculate from ΔΨd_cmp and Ψd0_std.

<Effects of the present invention>
The configuration and operation of magnet temperature estimation in the present invention utilizes the fact that the ratio between the d-axis magnetic flux fluctuation amount ΔΨd0 at Id zero and the magnet magnetic flux reference value Ψd0_std is almost uniquely determined by the difference between the reference temperature and the magnet temperature at the time of estimation. ing. If the d-axis magnetic flux fluctuation amount ΔΨd, which is different from the d-axis magnetic flux fluctuation amount ΔΨd0 at the time of Id zero, is used as is for estimating the magnet temperature, an estimation temperature error will occur. The rear d-axis magnetic flux fluctuation amount ΔΨd_cmp is used. Furthermore, if the magnet magnetic flux reference value Ψd0_std is kept constant and used for magnet temperature estimation, 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, which is equivalent to ΔΨd0, and calculating Ψd0_std based on the q-axis current value Iq, it is possible to appropriately correct the current dependence of the d-axis magnetic flux fluctuation amount ΔΨd due to temperature changes, and the magnet temperature estimation Accuracy can be increased.

Furthermore, the d-axis magnetic flux fluctuation amount ΔΨd is corrected based on two parameters, the d-axis current value Id and the q-axis current value Iq, and the magnet magnetic flux reference value Ψd0_std is calculated based on the q-axis current value Iq. Compared to the method of directly calculating the magnet temperature by inputting three parameters: Id, q-axis current value Iq, d-axis magnetic flux Ψd, or magnet magnetic flux, the burden and time of adjustment work required in advance and the processing load during estimation are reduced. Significantly smaller.
Next, a description will be given of improving the accuracy of the estimated magnet temperature value by correcting ΔΨd to ΔΨd_cmp, which is equivalent to ΔΨd0, and calculating Ψd0_std based on the q-axis current value Iq.

FIG. 17 is a control block diagram illustrating a configuration example of the magnet temperature estimating section in a case where the d-axis magnetic flux fluctuation amount correction section is not provided and the magnet magnetic flux reference value is a constant. There is no d-axis magnetic flux variation correction section, and the magnet magnetic flux reference value calculation section 43a outputs a constant value of the magnet magnetic flux reference value. The d-axis magnetic flux variation calculation section 41a is the same as the d-axis magnetic flux variation calculation section 41.

FIG. 18 shows an example of the magnet temperature estimation error of the magnet temperature estimating section when the d-axis magnetic flux fluctuation amount correction section is not provided and the magnet magnetic flux reference value is 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 is plotted by subtracting the true value of the magnet temperature at the time of estimation from the estimated value of the magnet temperature against the rotation speed and torque. are doing. Since the d-axis magnetic flux variation amount correction is not performed and the magnet magnetic flux reference value is kept constant, a large estimation error of 100° C. occurs. In particular, in the high torque region where the q-axis current increases, the error in the magnet magnetic flux reference value becomes large, and a large error also occurs in the estimated magnet temperature value.

FIG. 19 is a control block diagram showing an example of the configuration of the magnet temperature estimating section in the case where the d-axis magnetic flux fluctuation amount correction section is not provided.
Although there is no d-axis magnetic flux fluctuation amount correction section, the magnet magnetic flux reference value calculation section 43b is the same as the magnet magnetic flux reference value calculation section 43, and the d-axis magnetic flux fluctuation amount calculation section 41a is the same as the d-axis magnetic flux fluctuation amount calculation section 41. be.

FIG. 20 shows an example of the magnet temperature estimation error of the magnet temperature estimation section when the d-axis magnetic flux fluctuation amount correction section is not provided. The conditions and plotting method for the true value of the magnet temperature during estimation are the same as in FIG. 18. Compared with FIG. 18, the estimated temperature error is reduced by calculating the magnet magnetic flux reference value based on the q-axis current. However, since the d-axis magnetic flux fluctuation amount ΔΨd, which is different from the d-axis magnetic flux fluctuation amount ΔΨd0 when Id is zero, is used as is for estimating the magnet temperature, an estimated temperature error of about 20° C. occurs.

FIG. 21 shows an example of the magnet temperature estimation result by the magnet temperature estimation unit 40. By correcting ΔΨd to ΔΨd_cmp, which is equivalent to ΔΨd0, and calculating Ψd0_std based on the q-axis current value Iq, it is possible to appropriately correct the current dependence of the d-axis magnetic flux fluctuation amount ΔΨd due to temperature changes, and reduce the estimated temperature error. The temperature decreases to around 5℃.

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

KΨ=ΔΨd×K/Ψd0_std…(12)
Here, it is also possible to adopt a configuration in which K/Ψd0_std is combined into one conversion coefficient Kt, and the conversion coefficient Kt is calculated from the d-axis current value and the q-axis current value. FIG. 22 shows a control block diagram of a portion where the magnetic flux change ratio is calculated from the d-axis magnetic flux fluctuation amount in this case. The conversion coefficient calculation unit 45 calculates the conversion coefficient Kt based on equation (12), and multiplies it by the d-axis magnetic flux fluctuation amount ΔΨd, thereby calculating the magnetic flux change ratio KΨ.

Example 2 of the present invention will be described. Components that are common to those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

The configuration of this embodiment is the same as that of embodiment 1 except for the following points. The present embodiment relates to a control unit 10 having means for using information on the estimated magnet temperature value estimated by the magnet temperature estimating unit 40.

A problem with motors that have permanent magnets in their rotors is thermal demagnetization of the permanent magnets. When the temperature of a permanent magnet rises above a certain level, irreversible demagnetization may occur. If the permanent magnet becomes demagnetized, it becomes difficult to control the rotational speed or torque of the motor to a desired value. Furthermore, in order to ensure the generated torque, the current flowing through the motor or inverter may increase.

FIG. 23 is a block diagram showing the configuration of the control section 10a according to the second embodiment of the present invention. The control unit 10a of the second embodiment includes means for using information on magnet temperature estimation.

In the configuration shown in FIG. 23, a torque command value limiter 16, a d-axis current command value limiter 17 that limits the d-axis current command value, and a q-axis current command value limiter 18 that limits the q-axis current command value. have. The torque command value limiter 16 uses the magnet temperature estimate estimated by the magnet temperature estimator 40 to calculate the speed command value and torque command obtained from the controller 10a or from a higher-level control system or other control system (not shown). , limits the torque command value.

FIG. 24 is a diagram showing a configuration example of the torque command value limiting section 16, the d-axis current command value limiting section 17, and the q-axis current command value limiting section 18. The estimated magnet temperature value estimated by the magnet temperature estimation section 40 is input to the command limit value calculation section 101 . The command limit value calculation unit 101 outputs a command limit value according to the input estimated magnet temperature value.

For example, if the estimated magnet temperature with no risk of thermal demagnetization is below the judgment threshold Th, the command limit value is set to the same value as when the magnet temperature is sufficiently low, and if the estimated magnet temperature exceeds the judgment threshold Th. , the command limit value is decreased and output. If the estimated magnet temperature value is high and there is a high possibility of thermal demagnetization, the command value limit value may be set to zero and the motor output may be set to zero.

The command value limiter 102 limits the maximum and minimum values of the torque command value, d-axis current command value, or q-axis current command value based on the command value limit value. Here, although the maximum value and the minimum value limit values have different signs, the absolute value may be set as the command value limit value. Alternatively, a maximum value command value limit value calculation section and a minimum value command value limit value calculation section may be provided, and the maximum value and minimum value limit values may be set to different values.

In this way, by having a configuration that includes means for using information on the estimated magnet temperature value estimated by the magnet temperature estimating section 40, thermal demagnetization of the permanent magnet of the PM motor and excessive current flowing through the PM motor and the inverter 30 can be prevented. It is possible to prevent such an increase in advance. In other words, a highly reliable motor control device can be provided. Here, the configuration may include at least one of the torque command value limiting section 16, the d-axis current command value limiting section 17, and the q-axis current command value limiting section 18. One command value limiting section can prevent thermal demagnetization of the permanent magnet of the PM motor and an excessive increase in the current flowing through the PM motor and inverter 30, but it is also possible to prevent redundancy and gradual output reduction. For this purpose, a configuration including a plurality of command value limiting sections may be used.

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

Example 3 of the present invention will be described. Components that are common to Examples 1 and 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

The configuration of this embodiment is the same as that of embodiment 1 except for the following points. The present embodiment relates to a control section 10b having means for using information on the estimated magnet temperature value estimated by the magnet temperature estimating section 40.

When controlling the torque of a motor that has a permanent magnet in its rotor to a desired value, if the temperature of the magnet changes, the magnetic flux will change depending on the temperature, so if some measure is not taken, the torque accuracy will deteriorate. be. When torque accuracy deteriorates, for example, when a motor control device is installed in an electric vehicle system, ride comfort and automatic driving accuracy deteriorate.

FIG. 25 is a block diagram showing the configuration of the control section 10b according to the third embodiment of the present invention. The control unit 10b of the third embodiment includes a current command value calculation unit that calculates a d-axis current command value and a q-axis current command value by inputting the magnet temperature estimated value estimated by the magnet temperature estimation unit 40 in addition to the torque command value. 11a.

The current command value calculation unit 11a calculates the d-axis current command value and the q-axis current command value so that the difference between the torque command value and the actual torque of the motor becomes small when the magnet temperature is the reference temperature. If the magnet temperature differs 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 due to the magnet temperature change is reduced.

In this way, by having a configuration that includes means for using information on the estimated magnet temperature value estimated by the magnet temperature estimating section 40, it is possible to reduce deterioration of torque accuracy due to changes in magnet temperature, thereby providing a motor control device with high torque accuracy. be able to.

As described above, the q-axis voltage value calculation 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 matches the command value. and d-axis magnetic flux fluctuation, which calculates the d-axis magnetic flux fluctuation amount, which is the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value, using the q-axis voltage value, electrical angular velocity, d-axis current value, and q-axis current value as input. a d-axis magnetic flux fluctuation amount correction section that calculates a corrected d-axis magnetic flux fluctuation amount based on the d-axis current value and the q-axis current value, and a magnet magnetic flux reference value based on the q-axis current value. and a magnet temperature calculation unit that calculates an estimated magnet temperature value based on the corrected d-axis magnetic flux fluctuation amount and the magnet magnetic flux reference value. In this case, it is possible to correct the current dependence of the amount of magnetic flux fluctuation due to temperature change, improve the accuracy of magnet temperature estimation, and reduce the burden and time of adjustment work required in advance and the processing load at the time of estimation.

The present invention is not limited to the embodiments described above, and includes various modifications. For example, the embodiments described above are described in detail to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to having all the configurations described.

Further, each of the above-mentioned configurations, functions, processing units, processing procedures, etc. may be partially or entirely realized in hardware by, for example, designing an integrated circuit. Furthermore, each of the configurations and functions described above may be realized by software by having a processor interpret and execute programs for realizing the respective functions.

In addition, the signal lines and information lines shown are those considered necessary for explanation, and do not necessarily show all control lines and information lines. Further, each of 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 of them may be located on a network or cloud via communication.

Furthermore, although the motor has been described as having an inner rotor structure in which the rotor is disposed inside the stator, it may have an outer rotor structure. Further, a radial gap motor or an axial gap motor may be used. In addition to the PMSM, a synchronous motor with magnets arranged therein or an SRM may be used.

10, 10a, 10b...Control units 11, 11a...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 current command value limiter 18...q-axis current command value limiter 20...PM motor 27...permanent magnet 30...inverter 40...magnet temperature estimator 41...d-axis magnetic flux variation calculation unit 42...d-axis magnetic flux variation correction unit 43...Magnet magnetic flux reference value calculation unit 44...Magnet temperature calculation unit 45...Conversion coefficient calculation unit 50...Current detection means 60...Angle sensor 70...Voltage sensor 100...Motor control device 101...Command limit value calculation unit 102...Command value limiter 411...d-axis magnetic flux calculation section 412...d-axis magnetic flux reference value calculation section 421...correction coefficient calculation section 441...magnet temperature conversion section

Claims (6)

In a motor control device including a control unit that controls a motor having a permanent magnet,
The control unit includes:
A q-axis voltage value calculated based on either a rotational speed command value of the motor, a torque command value of the motor, or a q-axis voltage value calculated based on a voltage detection value of the motor, and an electrical angle of the motor. The calculated electrical angular velocity and the d-axis current value and the q-axis current value that are calculated based on the voltage detection value of the motor or the current detection value of the motor or based on the command value are input, and the permanent magnet Equipped with a magnet temperature estimator that estimates the temperature of
The magnet temperature estimator includes:
d-axis magnetic flux fluctuation, 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 fluctuation amount, which is the difference between the d-axis magnetic flux and the d-axis magnetic flux reference value. a quantity calculation section;
a d-axis magnetic flux fluctuation amount correction unit that calculates a corrected d-axis magnetic flux fluctuation amount by correcting the d-axis magnetic flux fluctuation amount based on the d-axis current value and the q-axis current value;
a magnet magnetic flux reference value calculation unit that calculates a magnet magnetic flux reference value based on the q-axis current value;
A motor control device comprising: a magnet temperature calculation unit that calculates an estimated magnet temperature value of the permanent magnet based on the corrected d-axis magnetic flux fluctuation amount and the magnet flux reference value. The motor control device according to claim 1,
The d-axis magnetic flux fluctuation amount calculation section inputs the q-axis voltage value, the electrical angular velocity, and the q-axis current value and calculates the d-axis magnetic flux; a d-axis magnetic flux reference value calculation unit that inputs the q-axis current value and calculates a d-axis magnetic flux reference value,
A motor control device characterized in that the d-axis magnetic flux fluctuation amount is calculated from a difference between the d-axis magnetic flux and the d-axis magnetic flux reference value. The motor control device according to claim 1,
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 and calculates a correction coefficient, and calculates a correction coefficient based on the d-axis magnetic flux variation and the correction coefficient. , a motor control device that calculates the corrected d-axis magnetic flux fluctuation amount. The motor control device according to claim 1,
The magnet temperature calculation unit includes a magnet temperature conversion unit that inputs a magnetic flux change ratio calculated based on the corrected d-axis magnetic flux fluctuation amount and the magnet magnetic flux reference value, and calculates the estimated magnet temperature value. A motor control device characterized by: The motor control device according to any one of claims 1 to 4,
The control unit may include a command value limiter that limits the maximum and minimum values of the torque command value, the d-axis current value, or the q-axis current value based on the estimated magnet temperature value. Motor control device. The motor control device according to any one of claims 1 to 4,
A motor control device 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 estimated magnet temperature value.

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