JP2015159666A - Motor controller and motor system including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the peak of an opposite magnetic field applied to a magnet of a motor.SOLUTION: A motor controller includes a three-phase/dq converter 20 for receiving the detection value of a current flowing to a motor 18, and converting the value into a d-axis current value and a q-axis current value, high frequency current value setting means 22 obtaining a harmonic current value for suppressing the harmonic components of the opposite magnetic field to the magnet of the motor 18, depending on the d-axis current value and q-axis current value, and current command value setting means 24 obtaining the d-axis current command value and q-axis current command value by superposing the harmonic current value on at least one of the d-axis current value and q-axis current value.

Description

  The present invention relates to an electric motor controller and an electric motor system including the electric motor controller.

  In an electric motor, there is a risk of demagnetization of the magnet due to a reverse magnetic field applied to the magnet due to an alternating current that flows when the magnetic field is weakened. When demagnetization occurs, the rotational characteristics of the motor are deteriorated.

  In view of this, a technique for reducing the influence of demagnetization by cutting away the magnet in a portion with a strong demagnetizing field or increasing the holding force in a portion with a strong reverse magnetic field is disclosed (Patent Documents 1 to 3). Moreover, the technique of reducing the reverse magnetic field applied to a magnet by devising the structure of the space | gap near a magnet is disclosed (patent documents 4 and 5).

  Moreover, the technique which suppresses the demagnetization proof reduction by a heat | fever by suppressing the heat_generation | fever of a magnet by magnet vortex loss by dividing | segmenting a magnet is disclosed (patent documents 6 and 7). Moreover, in order to reduce the influence of the demagnetization accompanying the rise in magnet temperature, the technique which suppresses energizing current itself is disclosed (patent documents 8 and 9). Furthermore, in order to reduce the influence of demagnetization accompanying a rise in magnet temperature, a technique for reducing current ripple and suppressing demagnetization due to heat generation accompanying magnet vortex loss is disclosed (Patent Documents 10 to 13).

JP 2006-158098 A JP 2012-4147 A JP 2009-516382 A JP 2003-143788 A JP 2013-118772 A JP 2000-324736 A JP 2005-354899 A JP-A-62-81950 JP 2013-198234 A JP 2012-239330 A JP 2010-93982 A JP 2012-525287 A JP 2003-284383 A

  However, in the method of suppressing demagnetization by the shape of the magnet and the gap structure near the magnet, the cost for changing or processing the material of the magnet increases, which may increase the manufacturing cost of the motor system. is there.

  In addition, in the method of suppressing the energization current itself when the temperature of the magnet rises, the fundamental wave current (current of the fundamental frequency) that generates an effective torque in the motor is also limited, which may cause a decrease in the output of the motor. There is.

  Furthermore, although the method of reducing the current ripple can be expected to have a certain effect on suppressing the temperature rise of the magnet, the effect on suppressing the demagnetizing field is small, and the demagnetizing field may be increased depending on the current adjusting method.

  One aspect of the present invention includes a dq-axis conversion unit that receives a detection value of a current flowing through an electric motor and converts the detection value into a d-axis current value and a q-axis current value, and the d-axis current value and the q-axis. Harmonic current setting means for obtaining a harmonic current value for suppressing a harmonic component of a reverse magnetic field applied to the magnet of the electric motor according to a current value; and at least one of the d-axis current value and the q-axis current value An electric motor controller comprising: current command value setting means for obtaining a d-axis current command value and a q-axis current command value by superimposing harmonic current values.

  According to another aspect of the present invention, there is provided an electric motor, dq-axis conversion means for receiving the detected value of the current flowing through the electric motor and converting the detected value into a d-axis current value and a q-axis current value, and the d-axis current value. And harmonic current setting means for obtaining a harmonic current value for suppressing a harmonic component of a reverse magnetic field applied to the magnet of the electric motor according to the q-axis current value, and the d-axis current value and the q-axis current value Current command value setting means for obtaining a d-axis current command value and a q-axis current command value by superimposing the harmonic current value on at least one of the harmonic current values; and a motor according to the d-axis current command value and the q-axis current command value. An electric motor system comprising: an inverter that controls a current to flow.

  Here, the harmonic current setting means calculates the harmonic current value according to the d-axis current value and the q-axis current value based on a predetermined motor field model, or the d-axis current value and The d-axis current value and the q-axis current value corresponding to the d-axis current value and the q-axis current value based on a data map in which a harmonic current value that suppresses a harmonic component of a reverse magnetic field to the magnet of the motor is associated with the q-axis current value. It is preferable to obtain the harmonic current value.

  Further, the harmonic current value is preferably a current value having a phase opposite to that of the harmonic current that gives a reverse magnetic field to the magnet of the electric motor.

  The harmonic current value is preferably a current value that is a 3Nth harmonic of the fundamental frequency (where N is a natural number).

  The current command value setting means preferably superimposes the harmonic current value so that the time average of the d-axis current value and the q-axis current value does not change before and after the harmonic current value is superimposed. is there.

  Further, it is preferable that the current command value setting means corrects the harmonic current value according to the temperature of the magnet.

  According to the present invention, the peak of the reverse magnetic field applied to the magnet can be reduced.

It is a figure which shows the structure of the electric motor system in embodiment of this invention. It is a figure explaining the control method of the electric motor current in embodiment of this invention. It is a figure which shows another example of a structure of the electric motor system in embodiment of this invention. It is a figure which shows the suppression effect of the demagnetizing field in embodiment of this invention.

  As shown in FIG. 1, the electric motor system in the embodiment of the present invention includes an electric motor controller 10, an inverter 12, a current sensor 14, a rotation sensor 16, and an electric motor 18. The motor controller 10 is a circuit that controls the motor currents iu, iv, and iw in a dq axis coordinate system that rotates in synchronization with the rotation of the motor. The motor controller 10 controls the motor current that flows through the motor by controlling the inverter 12.

  Current sensors 14 a and 14 b detect U-phase AC current iu and V-phase AC current iv flowing in electric motor 18. The detected U-phase AC current iu and V-phase AC current iv are input to the motor controller 10. The W-phase alternating current iw is obtained as iw = −iu−iv from the U-phase alternating current iu and the V-phase alternating current iv.

  The rotation sensor 16 is connected to the output shaft of the electric motor 18 and detects the rotation angle of the electric motor 18. For example, the rotation sensor 16 outputs a pulse signal corresponding to the rotation angle of the electric motor 18. The output of the rotation sensor 16 is input to the electric motor controller 10. The electric motor controller 10 receives the output of the rotation sensor 16 and calculates the rotation speed ω of the electric motor 18 based on the pulse signal from the rotation sensor 16. Furthermore, the motor controller 10 calculates the rotation angle θe of the dq axis coordinate system (fundamental current coordinate system) viewed from the three-phase AC coordinate system.

  The motor controller 10 receives the outputs from the current sensor 14 and the rotation sensor 16 and controls the motor current so as to suppress the demagnetizing field that affects the magnet. As shown in FIG. 1, the motor controller 10 includes a three-phase / dq converter 20, a high-frequency current setting means 22, a current command value setting means 24, a current / voltage converter 26, and a dq / 3-phase converter 28. Composed. Each component of the electric motor controller 10 can be configured by a logic circuit, or can be realized by a programmable processing unit (CPU or the like).

  The three-phase / dq converter 20 corresponds to dq-axis conversion means for converting the three-phase current detected by the current sensor 14 into a dq-axis current. The three-phase / dq converter 20 converts the motor current (three-phase alternating current) iu, iv into the d-axis actual current value id and the q-axis actual current value iq using the electrical rotation angle θe synchronized with the fundamental wave current. To do.

  For example, when the motor current (three-phase currents iu, iv, iw) flows with respect to the rotation angle θe as shown in FIG. 2A, the d-axis with respect to the rotation angle θe as shown in FIG. Changes in the actual current value id and the q-axis actual current value iq can be calculated.

  The high-frequency current setting means 22 sets a high-frequency current value for reducing the demagnetizing field for the magnet according to the d-axis actual current value id and the q-axis actual current value iq. That is, as the motor rotates, a demagnetizing field including a high-frequency component (a frequency component higher than the fundamental frequency of the motor current) is generated with respect to the permanent magnet. Therefore, a high-frequency current value for canceling it is set.

  Based on the magnetic field model considering the mechanical structure of the electric motor 18, it is possible to simulate a demagnetizing field for the permanent magnet when the d-axis current value id and the q-axis current value iq are flowing. Therefore, a high-frequency component of the demagnetizing field with respect to the rotation angle θe is obtained by simulation in advance using the d-axis current value id and the q-axis current value iq as parameters, and d-axis current values id and q for canceling out the high-frequency component of the demagnetizing field. The high frequency component of the shaft current value iq is calculated. Then, for each combination of the d-axis current value id and the q-axis current value iq, a high-frequency current value (d-axis high-frequency current value idh and q-axis high-frequency current value iqh) for canceling the high-frequency component of the demagnetizing field is registered as a data map. To do.

  Note that the high-frequency current values (d-axis high-frequency current value idh and q-axis high-frequency current value iqh) are current values that are in reverse phase to the harmonic current that causes a reverse magnetic field to be applied to the magnet of the motor 18. In other words, the high-frequency current values (d-axis high-frequency current value idh and q-axis high-frequency current value iqh) are motors in an axis coordinate system that rotates at a frequency that is an integral multiple of the frequency of the fundamental wave components of the motor currents iu, iv, and iw. It is a harmonic component that cancels the demagnetizing field by being superimposed on the currents iu, iv, iw. When the electric motor 18 is driven by a three-phase current, the high-frequency current values (d-axis high-frequency current value idh and q-axis high-frequency current value iqh) are 3N-order harmonics (where N is a natural number) of the fundamental frequency.

  Thereby, the high-frequency current setting means 22 can determine the high-frequency current values (d-axis high-frequency current value idh and q-axis high-frequency current value iqh) referring to the data map. That is, the high-frequency current value (d-axis high-frequency current value idh and q-axis high-frequency current value iqh) registered corresponding to the d-axis actual current value id and the q-axis actual current value iq in the data map is changed to the d-axis actual current value. The harmonic component of the demagnetizing field can be canceled by superimposing it on the id and q-axis actual current value iq.

The current command value setting means 24 sets the current command value by superimposing the high-frequency current value on the motor current value. The current command value setting means 24 is the d-axis high-frequency current value idh and q-axis high-frequency determined by the high-frequency current setting means 22 to the d-axis actual current value and q-axis actual current value obtained by the three-phase / dq converter 20. The d-axis current command value id ^* and the q-axis current command value iq ^* are calculated by adding the current values iqh, respectively. That is, the d-axis current command value id ^* and the q-axis current command value iq ^* are used for flowing a d-axis actual current and a q-axis actual current on which a harmonic component current that reduces a demagnetizing field generated in the electric motor 18 is superimposed. It becomes a command value.

  At this time, the current command value setting means 24 sets the d-axis high-frequency current value idh and the q-axis high-frequency to the d-axis actual current value and the q-axis actual current value so that the average value of the d-axis actual current and the q-axis actual current does not change. It is preferable to add each of the current values iqh. Thereby, it is possible to reduce the demagnetizing field without substantially changing the output of the electric motor 18.

  Further, the d-axis high-frequency current value idh and the q-axis high-frequency current value iqh may be superposed according to the magnet temperature Tm of the electric motor 18.

  As an example, the current command value setting unit 24 sets the d-axis high-frequency current value idh and the q-axis high-frequency current value iqh to the d-axis actual current value and the q-axis actual current value only when the magnet temperature Tm is equal to or higher than a predetermined temperature. Each is preferably added. The magnet tends to have a weaker magnetic force as the temperature Tm increases. In a ferrite magnet, the magnetic force decreases to about 90% at 50 ° C., about 80% at 100 ° C., and about 50% at 200 ° C. Therefore, for example, when the temperature exceeds 100 ° C., the d-axis high-frequency current value idh and q-axis It is preferable to add the high-frequency current value iqh. In the samarium-cobalt magnet, the magnetic force decreases to about 95% at 100 ° C. and about 85% at 200 ° C. Therefore, for example, the d-axis high-frequency current value idh and the q-axis high-frequency current value iqh are added when the temperature exceeds 150 ° C. It is preferable to do so. Further, in the neodymium magnet, the magnetic force is reduced to about 95% at 50 ° C. and about 90% at 100 ° C. Therefore, for example, the d-axis high-frequency current value idh and the q-axis high-frequency current value iqh are set when the temperature becomes 100 ° C. or higher. It is preferable to add them.

  In another example, the current command value setting means 24 increases the weighting as the magnet temperature Tm increases, and the d-axis high-frequency current value idh and the q-axis high-frequency current are added to the d-axis actual current value and the q-axis actual current value. It is preferable to add each of the current values iqh. In the ferrite magnet, for example, the weighting factor is set to 0.5 at 50 ° C., and the weighting factor is linearly changed so that the weighting factor is 1.0 at 100 ° C. or higher, so that the d-axis high-frequency current value idh and the q-axis high-frequency current value are Each iqh is multiplied by a weighting factor and added to the d-axis actual current value and the q-axis actual current value. In the samarium-cobalt magnet, for example, the weighting factor is set to 0.5 at 100 ° C., and the weighting factor is linearly changed so that the weighting factor becomes 1.0 at 200 ° C. or higher, and the d-axis high-frequency current value idh and q-axis are changed. The high-frequency current value iqh is multiplied by a weighting factor and added to the d-axis actual current value and the q-axis actual current value. Further, in the neodymium magnet, for example, the weighting factor is changed linearly so that the weighting factor is 0.5 at 50 ° C. and the weighting factor is 1.0 at 100 ° C. or more, and the d-axis high-frequency current value idh and the q-axis high-frequency are changed. The current value iqh is multiplied by a weighting factor and added to the d-axis actual current value and the q-axis actual current value.

  In this case, as shown in FIG. 3, a temperature sensor 30 may be provided in the electric motor 18 and the temperature Tm of the magnet may be measured by the temperature sensor 30. The temperature Tm detected by the temperature sensor 30 is input to the current command value setting unit 24, and the current command value setting unit 24 may perform control according to the temperature Tm.

The current / voltage converter 26 calculates a dq-axis current control voltage (d-axis voltage command value Vd ^* and q-axis voltage command value Vq ^* ) according to the d-axis current command value id ^* and the q-axis current command value iq ^*. To do. The voltage converter 26 performs PI (proportional integration) control on the difference between the d-axis current command value id ^* and the q-axis current command value iq ^* and the d-axis actual current id and the q-axis actual current iq, respectively. The dq-axis current control voltage (d-axis voltage command value Vd ^* and q-axis voltage command value Vq for matching the current id and the q-axis actual current iq with the d-axis current command value id ^* and the q-axis current command value iq ^* , respectively. ^* ) Is calculated.

The dq / 3-phase converter 28 converts the dq-axis current control voltage (d-axis voltage command value Vd ^* and q-axis voltage command value Vq ^* ) into a three-phase alternating current using the electrical rotation angle θe synchronized with the fundamental current. Conversion to fundamental wave current control voltage command values Vu ^* , Vv ^* , Vw ^* . Fundamental wave current control voltage command values Vu ^* , Vv ^* , Vw ^* are input to the inverter 12.

The inverter 12 is a circuit that converts the power of a DC power source such as a battery (not shown) into AC power using a switching element such as an IGBT. The inverter 12 generates a three-phase AC voltage corresponding to the three-phase AC fundamental current control voltage command values Vu ^* , Vv ^* , and Vw ^* output from the motor controller 10 and applies the generated voltage to the motor 18.

  The electric motor 18 is a permanent magnet synchronous electric motor in the present embodiment. The electric motor 18 is not limited to a permanent magnet synchronous electric motor, and any type of AC electric motors such as other synchronous electric motors and induction motors can be applied.

  Thus, by superimposing the harmonic current that cancels the high-frequency component of the demagnetizing field generated in the electric motor 18, the harmonic component of the reverse magnetic field is canceled, and the peak of the reverse magnetic field applied to the magnet can be reduced. .

  FIG. 4 shows the result of a simulation of the magnitude of the demagnetizing field at each position (1 to 4) of the rotor magnet of the electric motor 18 as shown in FIG. FIG. 4B shows the magnitude of the demagnetizing field when the high-frequency current superimposing process in the present embodiment is not performed, and FIG. 4C is the high-frequency current superimposing process in the present embodiment. The magnitude of the demagnetizing field is shown. As can be seen from a comparison between FIG. 4B and FIG. 4C, when the high-frequency current superimposing process in the present embodiment is applied, the peak of the demagnetizing field for the motor 18 is reduced, and the rotor magnet is applied to the rotor magnet. The influence of the demagnetizing field is suppressed.

DESCRIPTION OF SYMBOLS 10 Electric motor controller, 12 Inverter, 14 Current sensor, 16 Rotation sensor, 18 Electric motor, 20 3 phase / dq converter, 22 High frequency current setting means, 24 Current command value setting means, 26 Current / voltage converter, 28 dq / 3 Phase converter, 30 temperature sensor.

Claims (7)

Dq axis conversion means for receiving a detected value of the current flowing through the electric motor and converting the detected value into a d axis current value and a q axis current value;
Harmonic current setting means for obtaining a harmonic current value for suppressing a harmonic component of a reverse magnetic field applied to the magnet of the electric motor according to the d-axis current value and the q-axis current value;
Current command value setting means for obtaining a d-axis current command value and a q-axis current command value by superimposing the harmonic current value on at least one of the d-axis current value and the q-axis current value;
An electric motor controller comprising: The electric motor controller according to claim 1,
The harmonic current setting means calculates the harmonic current value according to the d-axis current value and the q-axis current value based on a predetermined motor field model, or the d-axis current value and the q-axis current. The harmonic current corresponding to the d-axis current value and the q-axis current value based on a data map in which the harmonic current value for suppressing the harmonic component of the reverse magnetic field to the magnet of the electric motor is associated with the value An electric motor controller characterized by obtaining a value. The electric motor controller according to claim 1 or 2,
The motor controller according to claim 1, wherein the harmonic current value is a current value having a phase opposite to that of the harmonic current that gives a reverse magnetic field to the magnet of the motor. The electric motor controller according to any one of claims 1 to 3,
The motor controller according to claim 1, wherein the harmonic current value is a current value that is a 3Nth harmonic of a fundamental frequency (where N is a natural number). The electric motor controller according to any one of claims 1 to 4,
The electric current command value setting means superimposes the harmonic current value so that the time average of the d-axis current value and the q-axis current value does not change before and after the harmonic current value is superimposed. controller. The electric motor controller according to any one of claims 1 to 5,
The electric motor controller, wherein the current command value setting means corrects the harmonic current value according to the temperature of the magnet. An electric motor,
Dq-axis conversion means for receiving a detected value of the current flowing through the electric motor and converting the detected value into a d-axis current value and a q-axis current value;
Harmonic current setting means for obtaining a harmonic current value for suppressing a harmonic component of a reverse magnetic field applied to the magnet of the electric motor according to the d-axis current value and the q-axis current value;
Current command value setting means for obtaining a d-axis current command value and a q-axis current command value by superimposing the harmonic current value on at least one of the d-axis current value and the q-axis current value;
An inverter that controls a current that flows through the motor in accordance with the d-axis current command value and the q-axis current command value;
An electric motor system comprising:

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