JP2020010456A - Motor control device - Google Patents

Abstract

To suppress generation of irreversible demagnetization of a permanent magnet of a motor in consideration of a harmonic current.SOLUTION: A motor control device 400 for controlling a motor 100 includes: a current command generation unit 220 for generating current commands Id*, Iq* according to required torque for a motor; a current control unit 230 for generating voltage commands Vd*, Vq* according to a difference between a current command and detection currents Id, Iq flowing through the motor detected by a current sensor 110; a PWM inverter 300 for applying AC voltages Vu, Vv, Vw according to the voltage commands to the motor to drive the motor; a harmonic current estimation unit 280 for estimating, from the voltage applied to the motor and the current flowing through the motor in accordance with the applied voltage, a harmonic current that cannot be detected by the current sensor during a time period after a current detection is performed and before a next current detection is performed; and a demagnetization control unit 290 for suppressing a current flowing through the motor in accordance with the harmonic current.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a motor control device.

  Patent Literature 1 discloses a control device for a synchronous machine that accurately estimates the temperature of a permanent magnet of the synchronous machine without a magnetic pole sensor. In this control device, the magnet temperature estimating unit calculates the armature interlinkage magnetic flux amount, and estimates the magnet temperature from the ratio to the reference armature interlinkage magnetic flux amount. When the irreversible demagnetization determination unit may cause irreversible demagnetization from the phase between the magnet temperature and the current flowing through the synchronous machine, the carrier frequency and the modulation method are increased to reduce the permanent magnet magnet temperature.

JP 2006-254521 A

  The above-described reduction of the magnet temperature of the permanent magnet is performed in accordance with the magnet temperature of the permanent magnet so that the amplitude value (also referred to as “peak value”) of the current flowing through the synchronous machine does not exceed the current value causing irreversible demagnetization. This is performed by increasing the carrier frequency to suppress the amplitude value of the current flowing through the synchronous machine. This is because the reduction in the magnet temperature of the permanent magnet suppresses the occurrence of irreversible demagnetization, so that the amplitude value of the current flowing through the synchronous machine causes irreversible demagnetization (hereinafter also referred to as “irreversible demagnetization threshold”). ). From this, in order to prevent irreversible demagnetization, it is required that the current flowing through the synchronous machine does not exceed the irreversible demagnetization threshold value even instantaneously.

  However, a current of a harmonic component of a carrier frequency (hereinafter, also referred to as “harmonic current”) is superimposed on a current flowing through the synchronous machine. If the amplitude value of the current on which the harmonic current is superimposed becomes equal to or greater than the irreversible demagnetization threshold at a timing different from the timing of detecting the current flowing through the synchronous machine, irreversible demagnetization may occur. Therefore, it is desired to suppress the occurrence of irreversible demagnetization by suppressing the current flowing through the synchronous machine in consideration of the harmonic current.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following embodiments.
According to one aspect of the invention, there is provided a motor control device (400) for controlling a motor (100). The motor control device includes: a current command generation unit (220) that generates a current command (Id *, Iq *) according to a required torque to the motor; and a current command detected by the current sensor (110). A current control unit (230) for generating a voltage command (Vd *, Vq *) according to a deviation from a detection current (Id, Iq) flowing through the motor; and an AC voltage (Vu, Vv, Vw) is generated by PWM, and the generated AC voltage is applied to the motor to drive the motor; a PWM inverter (300); from the time when the current is detected by the current sensor to the time when the next current is detected Between the voltage applied to the motor and the current flowing through the motor in accordance with the voltage applied to the motor, the harmonic current that cannot be detected by the current sensor. Comprises; a harmonic current estimation unit that estimates an (280); suppressing demagnetization controller a current flowing through the motor according to the estimated harmonic current (290).
According to this aspect, it is possible to control the operation of the motor while suppressing the occurrence of irreversible demagnetization of the permanent magnet in accordance with the harmonic current estimated by the harmonic current estimator.
It should be noted that the present invention can be realized in various forms, for example, in the form of a motor control method in addition to a motor control device.

FIG. 1 is an explanatory diagram schematically illustrating a configuration of a motor control device according to an embodiment. 9 is a flowchart illustrating magnet temperature estimation processing. FIG. 4 is an explanatory diagram illustrating an example of a magnet temperature characteristic depending on a reduction rate of a magnetic flux. 9 is a flowchart illustrating a harmonic current estimation process. FIG. 4 is an explanatory diagram showing voltage vectors corresponding to the states of switches of the inverter. FIG. 3 is an explanatory diagram showing a SW state and a voltage value at a fixed coordinate in each voltage vector. FIG. 3 is an explanatory diagram showing a state of generation of a harmonic current. 9 is a flowchart illustrating irreversible demagnetization suppression processing. It is explanatory drawing which shows an example of irreversible demagnetization, a current limit threshold, and an irreversible current threshold. FIG. 4 is an explanatory diagram illustrating an example of a relationship between a current flowing through a motor and a residual torque ratio. FIG. 3 is an explanatory diagram illustrating an example of a relationship between a magnet temperature and a carrier frequency.

A. Embodiment:
A1. Configuration of motor control device:
The main parameters used in this embodiment are as follows. These are parameters used in vector control of a three-phase permanent magnet synchronous motor.
Id *, Iq *: d, q-axis current commands Id, Iq ,: d, q-axis detection currents Iu, Iv, Iw: u, v, w-phase detection currents Ld, Lq: d, q-axis inductance R: armature winding resistance of the motor Vd *, Vq *: d, q-axis voltage commands Vu *, Vv *, Vw *: u, v, w-phase voltage commands Vu, Vv, Vw: u, v, w-phase applied voltage θ: detected electrical angle ω: detected electrical angular velocity φd, φq: permanent magnet d, q-axis magnetic flux φ: permanent magnet magnetic flux

  As shown in FIG. 1, the motor control device 400 according to the embodiment includes a control unit 200 and a PWM inverter 300. The motor control device 400 controls the three-phase permanent magnet synchronous motor 100. In the following description, the permanent magnet synchronous motor 100 is also simply referred to as “motor 100”.

  As the permanent magnet synchronous motor 100, an embedded magnet synchronous motor or a surface magnet synchronous motor can be used. In a synchronous motor having a permanent magnet, it is general that the direction of the N pole of one permanent magnet is the d-axis and the direction orthogonal thereto is the q-axis.

  The motor 100 is provided with a current sensor 110. The current sensor 110 measures detection currents Iu, Iv, Iw flowing through the uvw-phase coil. However, it is not necessary to measure all the uvw phases, and if the detection current of any two phases is measured, the detection current of the remaining one phase can be obtained based on the relationship of Iw + Iv + Iw = 0. Therefore, in FIG. 1, the configuration is such that the detection currents Iu and Iv of the uv phase are measured. The current flowing through the motor 100 is an AC current flowing according to an AC voltage applied to a uvw-phase coil of the motor 100 from a PWM inverter 300 described later, and the current sensor 110 outputs an amplitude value of the AC current, that is, And measure the peak value. In the following description, “current” means a peak value of an alternating current unless otherwise specified.

  The control unit 200 performs the speed feedback using the detected electrical angular velocity ω and the current feedback using the detected currents Id and Iq on the d-axis and the q-axis, thereby obtaining the voltage commands Vd * and Vq * on the d-axis and the q-axis. Then, the operation of the motor 100 is controlled by executing the voltage two-phase three-phase conversion and supplying the three-phase voltage commands Vu *, Vv *, Vw * to the PWM inverter 300. The control unit 200 includes a speed subtractor 205, a speed control unit 210, a current command generation unit 220, a current subtractor 225, a current control unit 230, a voltage two-phase / It has a three-phase converter 240, a current three-phase / two-phase converter 250, and an observer 260. In the following description, the d-axis and the q-axis are also simply referred to as “two axes”.

  The observer 260 obtains the detected electrical angle θ from the detected currents Id and Iq of the two axes and the voltage commands Vd * and Vq * of the two axes, and obtains the detected electrical angular velocity ω from the detected electrical angle θ. The detected electrical angle θ is used for conversion of the voltage two-phase / three-phase converter 240 and the current three-phase / two-phase converter 250. The detected angular velocity ω is used for speed control by the speed control unit 210, magnet temperature estimation by the magnet temperature estimation unit 270, and harmonic current estimation by the harmonic current estimation unit 280.

  The current three-phase / two-phase converter 250 converts the three-phase detection currents Iu, Iv, Iw of the motor 100 into two-axis detection currents Id, Iq. This conversion is performed based on the detected electrical angle θ, as is well known. Is typically the angle formed between the d axis and the u-phase coil axis.

  The speed control unit 210 obtains a torque command Trq * to be required of the motor 100 with respect to an angular speed deviation Δω which is a difference between the electrical angular speed command ω * calculated by the speed subtractor 205 and the detected electrical angular speed ω. This is executed using, for example, an arithmetic expression or a map indicating the relationship between the angular velocity deviation and the required torque.

  The current command generator 220 generates two-axis current commands Id * and Iq * according to the torque command Trq *. As described later, the maximum value that can be set as the two-axis currents Id and Iq is set by the demagnetization control unit 290, as described later. Within this range, two-axis current commands Id * and Iq * corresponding to the torque command Trq * are generated.

  The current subtractor 225 subtracts the detected currents Id and Iq of the two axes from the current commands Id * and Iq * of the two axes to calculate current deviations ΔId and ΔIq of the two axes. The current control unit 230 generates two-axis voltage command voltages Vd * and Vq * for operating the motor 100 such that the two-axis current deviations ΔId and ΔIq become zero. The voltage two-phase / three-phase converter 240 converts the two-axis voltage commands Vd *, Vq * into three-phase voltage commands Vu *, Vv *, Vw *. This conversion is also performed based on the detected electrical angle θ. The three-phase voltage commands Vu *, Vv *, Vw * thus obtained are supplied to the PWM inverter 300.

  The PWM inverter 300 executes the switching of the three-phase inverter circuit (not shown) according to the three-phase voltage commands Vu *, Vv *, Vw * to thereby apply the three-phase AC applied voltages Vu, Vv, Vw. generate. These applied voltages Vu, Vv, Vw are supplied to a three-phase coil of the motor 100.

  As described above, the control unit 200 determines the two-axis current commands Id * and Iq * by performing the speed feedback control using the detected electrical angular velocity ω on the electrical angular velocity command ω *. Further, the control unit 200 performs current feedback control using the detected currents Id and Iq of the two axes with respect to the current commands Id * and Iq * of the two axes to determine the voltage commands Vd * and Vq * of the two axes. , The three-phase voltage commands Vu *, Vv *, Vw * to be supplied to the motor 100 are determined. Then, three-phase applied voltages Vu, Vv, Vw according to the three-phase voltage commands Vu *, Vv *, Vw * are supplied from the PWM inverter 300 to the three-phase coil of the motor 100. Thereby, the control unit 200 can control the operation of the motor 100.

  Further, in addition to the function of controlling the operation of the motor 100, the control unit 200 controls the magnet temperature estimating unit 270 in order to realize a function of suppressing irreversible demagnetization generated by the permanent magnet of the motor 100. It has a wave current estimator 280 and a demagnetization controller 290.

  The magnet temperature estimating unit 270 estimates the permanent magnet magnet temperature Tme from the detected electrical angular velocity ω, the detected currents Id and Iq of the two axes, and the voltage commands Vd * and Vq * of the two axes. The harmonic current estimating unit 280 estimates a harmonic current generated according to the switching operation in the PWM inverter 300 from the detected electrical angular velocity ω, the detected currents Id and Iq of the two axes, and the applied voltages Vd and Vq of the two axes. , Its maximum value Ia_peak is determined. The demagnetization control unit 290 changes the carrier frequency of the carrier used in the PWM inverter 300 according to the magnet temperature Tme in order to avoid occurrence of irreversible demagnetization of the permanent magnet, and changes the maximum value of the harmonic current Ia_peak. , The maximum value of the current command in the current command generation unit 220 is limited. The magnet temperature estimating unit 270, the harmonic current estimating unit 280, and the demagnetizing control unit 290 operate specifically as described below, respectively, to thereby generate the irreversible generated in the permanent magnet of the motor 100. Suppress the occurrence of demagnetization.

A2. Magnet temperature estimation by magnet temperature estimator:
As shown in FIG. 2, the magnet temperature estimating unit 270 calculates the magnet magnetic flux of the permanent magnet of the motor 100 (step S110) and determines the rate of decrease of the calculated magnet magnetic flux in the control cycle in which the current is detected by the current sensor 110. Is estimated (step S120). Note that the control cycle in which the current is detected by the current sensor 110 corresponds to a half cycle (Tc / 2) of the carrier cycle Tc of the carrier used for the PWM executed in the PWM inverter 300. The carrier cycle Tc is the cycle of the carrier having the carrier frequency fc.

  The calculation of the magnet magnetic flux in step S110 is executed using, for example, a voltage equation related to control of the motor 100, as described below.

ここで、左辺の「ωφｄ」，「ωφｑ」は永久磁石の磁束により発生するｄ軸，ｑ軸の誘起電圧を表している。また、右辺の「ｖｄ」，「ｖｑ」はモータ１００に印加されるｄ軸とｑ軸の電圧を表し、「ｉｄ」，「ｉｑ」はモータ１００に流れるｄ軸とｑ軸の電流を表している。なお、ｄ軸のインダクタンスＬｄはｄ軸の電流ｉｄに応じて決定されるパラメータであり、ｑ軸のインダクタンスＬｑはｑ軸の電流ｉｄに応じて決定されるパラメータである。ｐは時間微分（ｄ／ｄｔ）を表す演算子である。 The voltage equation relating to the control of the motor 100 is expressed by equation (1).

Here, “ωφd” and “ωφq” on the left side represent d-axis and q-axis induced voltages generated by the magnetic flux of the permanent magnet. “Vd” and “vq” on the right side represent d-axis and q-axis voltages applied to the motor 100, and “id” and “iq” represent d-axis and q-axis currents flowing through the motor 100. I have. The d-axis inductance Ld is a parameter determined according to the d-axis current id, and the q-axis inductance Lq is a parameter determined according to the q-axis current id. p is an operator representing time derivative (d / dt).

なお、電流が０Ａの時に電流検出が行なわれるとすれば、インダクタンス、電流センサのゲイン誤差の影響を排除することができ、（３）式に示すように、ｄ軸とｑ軸の印加電圧Ｖｄ，Ｖｑからｄ軸とｑ軸の誘起電圧ωφｄ，ωφｑを求めることができる。

Assuming that current detection is not performed at the time of excessive current, the differential term of equation (1) can be deleted, and the voltage equation is expressed by equation (2).

If the current detection is performed when the current is 0 A, it is possible to eliminate the influence of the inductance and the gain error of the current sensor. As shown in the equation (3), the applied voltage Vd on the d-axis and the q-axis is obtained. , Vq, the induced voltages ωφd, ωφq on the d-axis and the q-axis can be obtained.

従って、（２）式を解くことで算出されたｄ軸とｑ軸の誘起電圧ωφｄ，ωφｑを（４）式に代入することで、現在の永久磁石の磁石温度Ｔｍｅがｔ［℃］での永久磁石の磁石磁束φ（ｔ）を算出することができる。但し、磁石磁束算出時点での磁石温度ｔ［℃］の値は不明である。 Here, the magnet magnetic flux φ (t) when the magnet temperature Tme of the permanent magnet is t [° C.] is expressed by Expression (4) using induced voltages ωφd and ωφq of the d-axis and the q-axis.

Therefore, by substituting the d-axis and q-axis induced voltages ωφd and ωφq calculated by solving the equation (2) into the equation (4), the current magnet temperature Tme of the permanent magnet at t [° C.] The magnetic flux φ (t) of the permanent magnet can be calculated. However, the value of the magnet temperature t [° C.] at the time of calculation of the magnet magnetic flux is unknown.

Then, the estimation of the magnet temperature Tme of the permanent magnet corresponding to the reduction rate of the magnet magnetic flux in step S120 is executed, for example, as described below. The decrease rate Rφ [%] of the magnet magnetic flux is represented by the ratio of the magnet magnetic flux φ (t) to the reference magnet magnetic flux φ (tr) at the reference temperature tr [° C.], as shown in Expression (5). For example, a typical temperature at which demagnetization does not occur in the permanent magnet, for example, a temperature t in the range of 20 ° C. to 30 ° C. is defined as a reference temperature tr, and a magnetic flux φ (t) at the temperature t is a reference magnetic flux φ. (Tr). In this example, tr = 30 ° C.

  Here, the decrease in magnet magnetic flux decreases as the magnet temperature increases. Therefore, if the relationship between the magnet flux decrease rate Rφ and the magnet temperature Tme as shown in FIG. 3 is obtained in advance, the permanent magnet magnet temperature at the magnet magnetic flux decrease rate Rφ [%] obtained by the equation (5) is obtained. Tme [° C.] can be estimated from the relationship between the magnet flux decrease rate Rφ and the magnet temperature Tme. Note that this relationship can be obtained in advance by measuring the rate of decrease in magnetic flux using the magnet temperature as a parameter, and prepared as a map or a polynomial that indicates the relationship between the rate of decrease Rφ in magnet flux and the magnet temperature Tme. Good. The rate of decrease in magnetic flux corresponds to the “amount of decrease in magnetic flux”.

A3. Harmonic current estimation by harmonic current estimator:
In the harmonic current estimating unit 280, a predicted current value that changes according to a change in a voltage vector corresponding to a switching state in the PWM inverter 300 in a control cycle in which the current is detected by the current sensor 110, as shown in FIG. (Step S210) and the estimation of the maximum value Ia_peak of the harmonic current based on the calculated expected current value (Step S220).

  As shown in FIG. 5, there are eight voltage vectors V0 to V7 corresponding to the states of the switches of the inverter (hereinafter, also referred to as “SW”) set by the PWM executed by the PWM inverter 300. (U, v, w) indicates the state of the upper switch in each of the voltage vectors V0 to V7, where "1" is ON and "0" is OFF. The state of the lower switch of each phase is opposite to the state of the upper switch.

  The six voltage vectors V1 to V6 have directions at intervals of 60 ° with respect to the voltage vector V1 (0 °), and the two voltage vectors V0 and V7 have no magnitude and direction. It is a zero vector.

そして、各電圧ベクトルＶ０〜Ｖ７における固定座標軸ａ，ｂでの電圧ｖａ，ｖｂは、電源電圧Ｖｄｃを基準として、それぞれ、図６に示す値をとる。従って、各電圧ベクトルＶ０〜Ｖ７における固定座標軸ａ，ｂでの電圧ｖａ，ｖｂを、（６）式に代入することにより、各電圧ベクトルＶ０〜Ｖ７におけるｄ軸，ｑ軸の電圧ｖｄ，ｖｑが求められる。 The d-axis and q-axis voltages vd and vq in each of the voltage vectors V0 to V7 are obtained from equation (6) using the voltages va and vb on the fixed coordinate axes a and b as parameters.

The voltages va and vb on the fixed coordinate axes a and b in each of the voltage vectors V0 to V7 take the values shown in FIG. 6 based on the power supply voltage Vdc. Therefore, by substituting the voltages va and vb on the fixed coordinate axes a and b in each of the voltage vectors V0 to V7 into the equation (6), the voltages vd and vq of the d-axis and the q-axis in each of the voltage vectors V0 to V7 are obtained. Desired.

  As shown in FIG. 7, current detection by the current sensor 110 is performed at times td1, td2, td3,... At intervals (Tc / 2) of a half cycle of the carrier cycle Tc. Then, the switching operation of the inverter in the PWM inverter 300 is determined at the timing of each current detection, and the voltage vector is sequentially set at the timing according to the switching operation. In the example of FIG. 7, the voltage vector is changed from V0 to V1 when the discrete time ΔT = T1 from the time td1 has elapsed, V1 to V2 when the next discrete time ΔT = T2 has elapsed, and further the next discrete time ΔT = V7 from V2 when T3 has elapsed. Then, when each discrete time elapses, the d-axis and q-axis currents id and iq according to the d-axis and q-axis voltages vd and vq that change according to the voltage vector during each discrete time elapse. appear.

ここで、「ｉｄ（ｎ＋１）」，「ｉｑ（ｎ＋１）」は、ある時点（ｎ）におけるｄ軸，ｑ軸の電圧ｖｄ（ｎ），ｖｑ（ｎ）及び電流ｉｄ（ｎ），ｉｑ（ｎ）に対して、離散時間ΔＴが経過時して電圧ベクトルが変化する時点（ｎ＋１）において予測されるｄ軸，ｑ軸の電流値である。なお、「ｉｄ（ｎ）」，「ｉｑ（ｎ）」は、時点（ｎ）が電流センサ１１０による電流検出時である場合には、電流センサ１１０による検出電流値であり、それ以外の電圧ベクトルが変化する時点の場合には、一つ前の離散時間ΔＴ経過時点において予測される電流値である。また、離散時間ΔＴは、図７に示したように、変化する電圧ベクトルに応じて定められる値である。また、「ｐＬｄ」はｄ軸の過渡インダクタンス、「ｐＬｑ」はｑ軸の過渡インダクタンスである。また、「φ」は永久磁石の磁束であり、「ω・φ」は、永久磁石による誘起電圧を表している。永久磁石の磁束φは、（４）式に従って求められる値であり、磁石温度推定部２７０から供給される。 The d-axis current id and the q-axis current iq generated according to the d-axis and q-axis voltages vd and vq that change according to the voltage vector are expressed by the equations (7a) and (7b).

Here, “id (n + 1)” and “iq (n + 1)” are d-axis and q-axis voltages vd (n) and vq (n) and currents id (n) and iq (n) at a certain time point (n). ) Are the d-axis and q-axis current values predicted at the time (n + 1) when the voltage vector changes after the elapse of the discrete time ΔT. Note that “id (n)” and “iq (n)” are current values detected by the current sensor 110 when the time point (n) is a time when current detection is performed by the current sensor 110, and other voltage vectors Is the current value predicted at the time point at which the previous discrete time ΔT has elapsed. Further, the discrete time ΔT is a value determined according to a changing voltage vector as shown in FIG. “PLd” is the transient inductance on the d-axis, and “pLq” is the transient inductance on the q-axis. “Φ” is a magnetic flux of the permanent magnet, and “ω · φ” represents a voltage induced by the permanent magnet. The magnetic flux φ of the permanent magnet is a value obtained according to the equation (4), and is supplied from the magnet temperature estimating unit 270.

  Therefore, the calculation of the predicted current value in step S210 (FIG. 4) is performed by calculating the predicted current values of the d-axis and the q-axis that change in accordance with the change of the voltage vector during the current detection timing by the current sensor 110 as (7a ) And (7b).

  Then, in the estimation of the maximum value Ia_peak of the harmonic current in step S220, the maximum value of the calculated predicted current values is set to the maximum value Ia_peak of the harmonic current generated during the current detection timing by the current sensor 110. It is performed by:

A4. Irreversible demagnetization suppression by demagnetization controller:
The demagnetization control unit 290 has the same control cycle as that of the magnet temperature estimating unit 270 and the harmonic current estimating unit 280, and as shown in FIG. 8, the magnet temperature Tme and harmonic of the permanent magnet estimated by the magnet temperature estimating unit 270. The operation of suppressing occurrence of irreversible demagnetization is performed based on the maximum value Ia_peak of the harmonic current estimated by the wave current estimation unit 280.

  If the magnet temperature Tme of the permanent magnet is estimated by the magnet temperature estimation unit 270 and the magnet temperature Tme is supplied to the demagnetization control unit 290 (step S310: YES), in step S320, the supplied magnet temperature Tme Is set in accordance with the current limit threshold value Ilth and the cutoff threshold value Isth.

  Here, for example, the relationship between the magnet temperature Tme [° C.] and the current limit threshold [Apeak], and the magnet temperature Tme [° C.] and the cutoff threshold are previously stored in the demagnetization control unit 290, for example, as shown in FIG. A map indicating the relationship with [Apeak] is prepared. Then, the demagnetization controller 290 selects and sets the current limit threshold Ilth [Apeak] and the cutoff threshold Isth [Apeak] corresponding to the magnet temperature Tme supplied from the magnet temperature estimator 270 from the map.

  The current limit threshold value Ilth is a threshold value used to limit the maximum value [Apeak] of the current flowing to the motor 100 by PWM in a process described later, and as shown in FIG. It is set to a value lower than the irreversible demagnetization threshold value Iirth [Apeak] indicating the current for generating magnetism. Further, the cutoff threshold value Isth is a threshold value used for stopping the supply of the applied voltage to the motor 100 by the PWM inverter 300 in a process described later. This is to prevent the possibility that irreversible demagnetization occurs in the permanent magnets of the motor 100 when the current flowing through the motor 100 becomes larger than the threshold value.

  Note that the map of the current control threshold value and the map of the cutoff threshold value shown in FIG. 9 are, for example, the current [Apeak] flowing through the motor that changes depending on the magnet temperature and the residual torque ratio [%] of the motor as shown in FIG. Are created so as to satisfy the allowable torque remaining rate, respectively.

  Next, in step S330 of FIG. 8, it is determined whether or not the magnet temperature Tme is higher than the rising threshold value Tuth. If the magnet temperature Tme is equal to or lower than the rising threshold value Tuth (step S330: NO), in step S340a, the setting of the carrier frequency fc is maintained at the initial setting. On the other hand, when the magnet temperature Tme is higher than the rising threshold value Tuth (step S330: YES), in step S340b, the carrier frequency fc corresponding to the magnet temperature Tme is set to be increased, and the carrier change command Sc * is set to PWM. It is supplied to the inverter 300. As a result, the PWM is executed at the changed carrier frequency fc in the PWM inverter 300. The setting for increasing the carrier frequency fc is executed, for example, by determining the value of the carrier frequency fc corresponding to the magnet temperature Tme from the map shown below.

  In the demagnetization control unit 290, for example, a map indicating the relationship between the magnet temperature Tme [° C.] and the carrier frequency fc [kHz] as shown in FIG. 11 is prepared in advance. In the example of FIG. 11, when the magnet temperature Tme is 100 ° C. or less, the carrier frequency fc is set to 5 kHz as an initial setting. At a temperature higher than 100 ° C., the carrier frequency fc becomes 20 kHz according to the increase in the magnet temperature Tme. It is set to rise up. In the case of this example, the magnet temperature Tme = 100 ° C. is set as the rising threshold Tuth.

  The relationship between the magnet temperature Tme and the carrier frequency fc as shown in FIG. 11 can be obtained, for example, as follows. First, from the relationship between the current [Apeak] flowing through the motor that changes depending on the magnet temperature as shown in FIG. 10 and the torque remaining rate [%] of the motor, the maximum value of the set current (for example, FIG. In this case, the temperature at which the magnet temperature needs to be lowered in order to satisfy the allowable torque residual ratio can be obtained, thereby obtaining the rising threshold Tuth. At a magnet temperature higher than the rising threshold value Tuth, a current that satisfies the allowable torque remaining rate is obtained from the relationship between the current flowing through the motor and the motor remaining rate as shown in FIG. The relationship between the magnet temperature Tme and the carrier frequency fc can be obtained by obtaining the carrier frequency fc that can be lowered to the maximum. Note that the prepared map may include data indicating a relationship between the magnet temperature Tme and the carrier frequency fc, limited to a value equal to or higher than the rising threshold.

  Next, when the harmonic current is estimated by the harmonic current estimation unit 280 and the maximum value Ia_peak is supplied to the demagnetization control unit 290 (step S350: YES), in step S360, the harmonic current is calculated. The maximum value Ia_peak is compared with the current limit threshold value Ilth set in step S320. If Ia_peak> Ilth (step S360: YES), a limit command CL * for limiting the maximum value of the current command to be equal to or less than the current limit threshold value Ilth is supplied to the current command generation unit 220, and the current command The maximum value is restricted (step S370). Then, in step S380, the maximum value Ia_peak of the harmonic current is compared with the cutoff threshold value Isth set in step S320. If Ia_peak> Isth (step S380: YES), in step S390, a stop command Sstp * is supplied to the PWM inverter 300, and the operation of the switch (SW) of the PWM inverter 300 is stopped. The operation of suppressing the occurrence of demagnetization is ended.

  On the other hand, if Ia_peak ≦ Ilth (step S360: NO) or Ia_peak ≦ Isth (step S380: NO), the operation of suppressing the occurrence of irreversible demagnetization in this control cycle is terminated.

  If the operation of suppressing the occurrence of irreversible demagnetization without any processing is completed from steps S360 and S380, the operation of suppressing the occurrence of irreversible demagnetization again in the next control cycle is performed. Be executed. On the other hand, when the operation of the switch of the PWM inverter 300 is stopped in step S390 and the operation of suppressing the occurrence of irreversible demagnetization is terminated, the operation of suppressing the occurrence of irreversible demagnetization is performed. Not. In this case, the motor control device 400 can restart the control operation of the motor 100, for example, when there is an operation instruction from a higher-level device of the motor control device 400 or when the motor control device 400 is reset.

A5. effect:
As described above, the motor control device 400 of the present embodiment can estimate the magnet temperature Tme of the permanent magnet of the motor 100 from the current detected by the current sensor 110. When the magnet temperature Tme becomes higher than the rising threshold Tuth, the carrier frequency fc of the carrier used in the PWM inverter 300 is increased according to the magnet temperature Tme, so that the peak value of the current flowing through the motor 100 is increased. Can be suppressed. Thus, it is possible to suppress the occurrence of irreversible demagnetization of the permanent magnet due to a rise in the magnet temperature.

  In addition, during an interval of current detection by the current sensor 110, a harmonic current that changes with a switch operation of the PWM inverter 300 according to a change in a voltage vector due to PWM is calculated, and a maximum value Ia_peak of the harmonic current is estimated. can do. When the estimated maximum value Ia_peak of the harmonic current becomes larger than the current limit threshold value Ilth set to a value smaller than the irreversible demagnetization threshold value Iirth indicating the current that causes irreversible demagnetization, By limiting the maximum value of the flowing currents Id and Iq to be smaller than the current limit threshold value Ilth, it is possible to suppress the maximum value Ia_peak of the harmonic current from exceeding the irreversible demagnetization threshold value Iirth. This suppresses the occurrence of irreversible demagnetization of the permanent magnet by suppressing the current according to the magnet temperature of the permanent magnet, and also suppresses the occurrence of irreversible demagnetization of the permanent magnet by suppressing the current according to the maximum value of the harmonic current. can do.

  When the estimated maximum value Ia_peak of the harmonic current is smaller than the irreversible demagnetization threshold value Iirth and larger than the current limit threshold value Ilth, and becomes larger than the cutoff threshold value Isth set to the PWM inverter 300, The switch operation can be stopped. Thus, the occurrence of irreversible demagnetization of the permanent magnet can be avoided by stopping the operation of the motor 100.

  In the present embodiment, the current limit threshold Ilth corresponds to a “first current threshold”, and the cutoff threshold Isth corresponds to a “second current threshold”.

B. Other embodiments:
(1) In the above embodiment, as shown in FIG. 8, it is determined whether or not the magnet temperature Tme is higher than the rising threshold Tuth (step S330), and when the magnet temperature Tme is higher than the rising threshold Tuth, the carrier frequency fc is determined. (Step S340b). However, the carrier frequency fc corresponding to the magnet temperature Tme may be obtained from the map (see FIG. 11) and set without performing the determination in step S330. According to the embodiment and the other embodiments, the carrier frequency fc can be increased in accordance with the estimated increase in the magnet temperature Tme of the permanent magnet, and the current flowing through the motor 100 can be suppressed. Irreversible demagnetization can be suppressed.

(2) In the above embodiment, the occurrence of irreversible demagnetization of the permanent magnet is suppressed by suppressing the current according to the magnet temperature of the permanent magnet, and the irreversible decrease of the permanent magnet is suppressed by suppressing the current according to the maximum value of the harmonic current. Although the case where the generation of the magnetism is suppressed has been described as an example, the occurrence of the irreversible demagnetization of the permanent magnet due to the suppression of the current corresponding to the maximum value of the harmonic current may be suppressed.

(3) As in the above embodiment, when the estimated maximum value Ia_peak of the harmonic current is larger than the current limit threshold value Ilth, the maximum values of the d-axis and q-axis currents Id and Iq flowing through the motor 100 are reduced. Although the current limit is set to be smaller than the current limit threshold Ilth, an alarm signal may be output in addition to this.

(4) In the above embodiment, the three-phase motor is controlled. However, the present invention is not limited to the three-phase motor, and another multilayer motor such as a six-phase motor may be controlled. Generally, an N-phase (N is an integer of 3 or more) motor can be controlled. When a polyphase motor other than the three-phase motor is to be controlled, the content of the conversion process of the voltage two-phase / three-phase converter 240 and the current three-phase / two-phase converter 250 depends on the number of phases of the motor. It is changed as appropriate.

(5) In the above embodiment, the magnet temperature is estimated from the magnetic flux decrease rate indicating the amount of reduction of the magnetic flux of the permanent magnet, but the present invention is not limited to this. The magnet temperature may be obtained using a temperature measurement sensor such as a thermistor or a thermocouple.

(6) The control unit 200 of the motor control device 400 can be realized by a microprocessor or hardware other than the microprocessor (for example, an application-specific integrated circuit (ASIC)). When the control unit 200 is realized by a microprocessor, the function of each component of the control unit 200 is realized by a program instruction.

  The present invention is not limited to the above-described embodiment, and can be implemented with various configurations without departing from the spirit of the invention. For example, the technical features of the embodiments corresponding to the technical features in each embodiment described in the summary of the invention may be used to solve some or all of the above-described problems, or to provide some of the above-described effects. Or, in order to achieve all of them, replacement and combination can be appropriately performed. If the technical features are not described as essential in this specification, they can be deleted as appropriate.

    100: motor, 110: current sensor, 220: current command generator, 230: current controller, 280: harmonic current estimator, 290: demagnetization controller, 300: PWM inverter, 400: motor controller, Id, Iq: detected current, Vd *, Vq *: voltage command, Vu, Vv, Vw: applied voltage

Claims (7)

A motor control device (400) for controlling a motor (100),
A current command generation section (220) for generating a current command (Id *, Iq *) according to a required torque for the motor;
A current controller (230) for generating a voltage command (Vd *, Vq *) according to a deviation between the current command and a detection current (Id, Iq) flowing through the motor detected by the current sensor (110); ,
A PWM inverter (300) that generates an AC voltage (Vu, Vv, Vw) according to the voltage command by PWM, applies the generated AC voltage to the motor, and drives the motor;
From the current detection by the current sensor to the next current detection, between the voltage applied to the motor and the current flowing through the motor according to the voltage applied to the motor, A harmonic current estimator (280) for estimating a harmonic current that cannot be detected by the current sensor;
A demagnetization control unit (290) that suppresses a current flowing through the motor according to the estimated harmonic current;
A motor control device comprising: The motor control device according to claim 1,
The demagnetization control unit increases the carrier frequency of the PWM in the PWM inverter in accordance with an increase in the magnet temperature of the permanent magnet of the motor, thereby suppressing an increase in the magnet temperature of the permanent magnet. A motor control device that suppresses irreversible demagnetization of permanent magnets. The motor control device according to claim 2, wherein
A motor control device comprising: a magnet temperature estimating unit (270) for obtaining a magnetic flux of the permanent magnet from the voltage command and the detected current, and estimating a magnet temperature of the permanent magnet from the obtained reduction amount of the magnetic flux. The motor control device according to claim 3, wherein
The demagnetization control unit obtains a carrier frequency corresponding to the estimated magnet temperature of the permanent magnet from a map indicating a relationship between the magnet temperature of the permanent magnet and the carrier frequency, and increases the magnet temperature of the permanent magnet. A motor control device for increasing the carrier frequency of the PWM according to the following. The motor control device according to any one of claims 1 to 4, wherein
The demagnetization control unit generates the current command generation unit when the estimated harmonic current is larger than a first current threshold at which irreversible demagnetization of the permanent magnet of the motor is likely to occur. A motor control device that suppresses the occurrence of irreversible demagnetization of the permanent magnet by limiting the current command to suppress the maximum value of the current flowing through the motor. The motor control device according to claim 3 or claim 4, which is dependent on claim 2.
The demagnetization control unit is configured to increase the carrier current of the PWM in the PWM inverter so that the estimated harmonic current is highly likely to cause irreversible demagnetization in the permanent magnet of the motor. When the current is larger than a current threshold, the current command generated by the current command generator is limited to suppress the maximum value of the current flowing through the motor, thereby suppressing occurrence of irreversible demagnetization of the permanent magnet. To control the motor. The motor control device according to claim 5 or 6, wherein:
The demagnetization control unit is configured such that the estimated harmonic current is larger than the first current threshold, and the second current threshold is more likely to cause irreversible demagnetization of the permanent magnet than the first current threshold. A motor control device for stopping the switching operation of the PWM inverter when the switching speed becomes larger than the threshold value.

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