JP2013233055A - Motor controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller which can suppress generation of demagnetization during operation of a motor including a permanent magnet composed while reducing or not containing a heavy rare earth element.SOLUTION: The motor controller includes: a current component determination unit for determining the basic component of a current supplied to a motor, according to the operation state of a motor and the request output for the motor; a harmonic current control unit for determining the component of a harmonic current having a frequency higher than that of a current supplied to the motor; and a superposition unit for superposing the component of a harmonic current determined by the harmonic current control unit on the basic component of a current supplied to the motor. In an electrical angle region during rotation of the rotor of the motor, the harmonic current control unit determines the component of the harmonic current so that a bottom part of the amplitude of the harmonic current matches a region of an electrical angle where the permeance for a rotary magnetic field at a corner of a permanent magnet is relatively small.

Description

  The present invention relates to a control device for an electric motor.

  A vehicle such as an EV (Electric Vehicle) or an HEV (Hybrid Electrical Vehicle) is provided with an electric motor as a drive source. FIG. 12 is a partial cross-sectional view of a permanent magnet field motor. An electric motor 50 shown in FIG. 12 includes a rotor 53 including a plurality of permanent magnets 51 concentrically provided around a rotation shaft, and a three-phase armature 55 provided on the outer diameter side of the rotor 53. And a stator 57. Each of the plurality of permanent magnets 51 is formed in a plate shape, and its side surface has four corners. Further, a pair of adjacent permanent magnets are arranged in a V shape that opens toward the outer peripheral surface of the rotor 53 when viewed from the rotation axis direction of the electric motor 50.

  The permeance of the permanent magnet 51 included in the rotor 53 is low at the corners. That is, a demagnetizing field is likely to act on the corners of the permanent magnet. For this reason, when the magnetic flux density is changed by applying a reverse external magnetic field to the permanent magnet 51, demagnetization occurs from the corner portion of the permanent magnet 51.

  For example, in the case of a two-pole three-slot motor, there are six places where permeance is lowered in one cycle. When demagnetization occurs during operation of the motor, the torque in the motor decreases, and vibration associated with an increase in torque ripple and noise associated with the occurrence of this vibration may occur. For this reason, in Patent Document 1, the permanent magnet is a rare earth sintered magnet mainly composed of light rare earth elements, and the heavy rare earth elements are partially diffused at a relatively higher concentration than other parts. A high coercive force portion is provided in a part of the permanent magnet. If the high coercive force portion is formed in the portion where the demagnetizing field acts most strongly during the operation of the electric motor, the demagnetization generated during the operation of the electric motor can be suppressed.

International Publication No. 2008/123251

  As described above, the permanent magnet constituting the permanent magnet motor of Patent Document 1 partially includes a high coercive force portion to which a heavy rare earth element is added. However, since rare earth elements such as dysprosium (Dy) and terbium (Tb) are rare, it is desirable to suppress the amount of use. However, in the case of an electric motor provided with a permanent magnet that does not contain heavy rare earth elements at the corners, torque is reduced during the operation, and vibration and noise accompanying an increase in torque ripple are generated.

  The objective of this invention is providing the control apparatus which can suppress generation | occurrence | production of a demagnetization at the time of operation | movement of the electric motor provided with the permanent magnet comprised by reducing or not including a heavy rare earth element.

  In order to solve the above-described problems and achieve the object, an electric motor control device according to a first aspect of the present invention includes a plurality of permanent magnets arranged at predetermined intervals in the circumferential direction (for example, the permanent magnet according to the embodiment). A rotor having a magnetic pole array composed of magnets 51 (for example, the rotor 53 in the embodiment) and a plurality of armatures (for example, the electric machine in the embodiment) arranged at predetermined intervals in the circumferential direction. And a rotating magnetic field that moves in the circumferential direction is interposed between the magnetic pole row and the armature magnetic poles generated in the plurality of armatures in response to power supply. A motor control device (e.g., ECU 100 in the embodiment) having a stator (e.g., stator 57 in the embodiment) having an armature row to be generated, and an operating state of the motor and Depending on the required output for the motor, A current component determining unit (for example, a current command determining unit 107 in the embodiment) that determines a basic component of current supplied to the motor, and a harmonic current component having a frequency higher than that of the current supplied to the motor. The harmonic current control unit (for example, the harmonic current control unit 117 in the embodiment) and the harmonic current component determined by the harmonic current control unit are superimposed on the basic component of the current supplied to the electric motor. A superimposing unit (for example, the superimposing units 109d and 109q in the embodiment), and the harmonic current control unit performs the rotation of the corner portion of the permanent magnet in the electrical angle region when the rotor rotates. The harmonic current component is determined such that the bottom portion of the amplitude of the harmonic current coincides with a region of an electrical angle having a relatively small permeance with respect to the magnetic field.

  Furthermore, in the electric motor control device according to the second aspect of the present invention, in the electrical angle region where the permeance is relatively small, the number of corners whose permeance is less than a threshold among the corners of the permanent magnet. It is a range of electrical angles that satisfies the condition that it is a predetermined number or more.

  Furthermore, in the motor control device according to claim 3, the harmonic current control unit is configured such that a permeance relative to the rotating magnetic field at a corner of the permanent magnet is relative to an electrical angle region during rotation of the rotor. The component of the harmonic current is determined so that the peak portion of the amplitude of the harmonic current coincides with a region of a large electrical angle.

  Furthermore, in the electric motor control device according to the fourth aspect of the present invention, in the electrical angle region where the permeance is relatively large, among the corners of the permanent magnet, the number of corners where the permeance is equal to or greater than a threshold value. It is a range of electrical angles that satisfies the condition that it is a predetermined number or more.

  Furthermore, in the motor control apparatus according to the fifth aspect of the present invention, the two adjacent permanent magnets constituting the plurality of permanent magnets are in the direction of the rotating shaft (for example, the rotating shaft 59 in the embodiment) of the motor. When viewed from above, the electrical angle region that is arranged in a V shape that opens toward the outer peripheral surface of the rotor and is susceptible to the demagnetizing field is the inner diameter of the two permanent magnets that are arranged in the V shape. Among the corners on the side, the electrical angle is in a range that satisfies the condition that the number of corners whose permeance is less than the threshold value is a predetermined number or more.

  Furthermore, in the motor control apparatus according to claim 6, the harmonic order in the dq axis coordinate system of the harmonic current component supplied to the motor is a value obtained by multiplying the number of poles and the number of phases of the motor. It is characterized by being.

According to the motor control device of the first to sixth aspects of the invention, it is possible to suppress the occurrence of demagnetization during the operation of the motor including the permanent magnet configured to reduce or not include heavy rare earth elements.
According to the electric motor control apparatus of the third and fourth aspects of the present invention, the torque in the electrical angle region where the permanent magnet is not easily affected by the demagnetizing field increases, so that the electric motor can output a desired torque.
According to the electric motor control device of the fifth aspect of the present invention, the demagnetization at the corner portion on the inner diameter side is more easily suppressed than the corner portion on the outer diameter side of the permanent magnet, and the corner on the outer diameter side is more easily suppressed. As compared with the case where the occurrence of demagnetization in the part is suppressed, the amplitude of the harmonic current can be reduced.

The figure which shows the structure of the electric motor system of one Embodiment. The block diagram which shows the internal structure of ECU100, and the relationship between the electric motor 50, ECU100, and PDU11. The figure which shows the part where especially the magnetic force and permeance which act on the permanent magnet of the rotor 53 fall when the three-phase current of the sine wave advanced by 30 degree | times is supplied to the stator 57 for every 30 degree | times electrical angle. The graph which shows an example of the change of the permeance of each corner | angular part of a pair of permanent magnet when the rotor 53 rotates. The graph which shows an example of the BH curve (demagnetization curve) in the corner | angular part of a permanent magnet The graph which shows the waveform of each current at the time of superimposing the 6th harmonic current on the dq axis to the three-phase current as the fundamental wave supplied to the stator of the two-pole three-phase motor The figure which shows the vector of the fundamental wave and superposition wave on the dq axis The figure which shows the relationship between d-axis current Id_c and q-axis current Iq_c The figure which shows the operating point area | region of the electric motor 50 The graph which shows an example of the BH curve (demagnetization curve) in the outer diameter side and inner diameter side of the corner | angular part of a permanent magnet The graph which shows an example of the permeance change of the corner | angular part of the internal diameter side of a pair of permanent magnet when the rotor 53 rotates Partial sectional view of permanent magnet field motor

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the electric motor system of embodiment described below is mounted in vehicles, such as EV (Electric Vehicle: Electric vehicle) or HEV (Hybrid Electrical Vehicle: Hybrid electric vehicle).

  FIG. 1 is a diagram illustrating a configuration of an electric motor system according to an embodiment. As shown in FIG. 1, the electric motor system of this embodiment includes an electric motor 50, an ECU (Electronic Control Unit) 100 that controls the operation of the electric motor 50, and a PDU (Power Drive Unit) 11 that is a drive circuit including an inverter circuit. And a battery 13.

  The electric motor 50 is the same as the electric motor 50 shown in FIG. That is, the electric motor 50 shown in a cross-sectional view in FIG. 1 includes a rotor 53 including a plurality of permanent magnets concentrically provided around a rotation shaft 59 and a three-phase provided on the outer diameter side of the rotor 53. And a stator 57 including the armature. Each of the plurality of permanent magnets is formed in a plate shape, and its side surface has four corners. Further, when viewed from the direction of the rotation shaft 59 of the electric motor 50, a pair of adjacent permanent magnets are arranged in a V shape that opens toward the outer peripheral surface of the rotor 53.

  The ECU 100 is an electronic circuit unit including a CPU, a RAM, a ROM, an interface circuit, and the like, and controls the operation of the electric motor 50 by executing a control program for the electric motor 50 mounted in advance by the CPU. The operation control of the electric motor 50 by the ECU 100 is performed by the ECU 100 controlling the PDU 11. That is, the PDU 11 switches the switching elements constituting the inverter circuit by PWM control according to the command value from the ECU 100.

  FIG. 2 is a block diagram showing the internal configuration of the ECU 100 and the relationship between the electric motor 50, the ECU 100, and the PDU 11. As shown in FIG. 2, the ECU 100 includes an electrical angle conversion unit 101, an electrical angular velocity calculation unit 103, a three-phase / dq conversion unit 105, a current command determination unit 107, superposition units 109d and 109q, and a subtraction unit 111d. , 111q, current controller 113, dq / 3-phase converter 115, and harmonic current controller 117.

  The ECU 100 receives a torque command value Tr_c based on the accelerator pedal opening, the vehicle speed, and the like. Further, the ECU 100 detects the mechanical angle position θ of the rotor 53 of the electric motor 50 detected by the rotational position sensor 61 such as a resolver and the stator 57 of the electric motor 50 from the PDU 11 detected by the phase current sensors 63u and 63w. The detected value Iu_s of the u-phase current and the detected value Iw_s of the w-phase current output to are input.

  The electrical angle conversion unit 101 calculates the magnetic flux vector rotation angle position θmf of the rotating magnetic field in the electric motor 50 based on the mechanical angle position θ of the rotor 53. The magnetic flux vector rotation angle position θmf of the rotating magnetic field indicates an electrical angle.

  The electric angular velocity calculation unit 103 calculates the magnetic flux vector rotation angular velocity ωmf by time-differentiating the magnetic flux vector rotation angle position θmf of the rotating magnetic field in the electric motor 50. The magnetic flux vector rotation angular velocity ωmf calculated by the electrical angular velocity calculation unit 103 is input to the current control unit 113 and the harmonic current control unit 117.

  The three-phase / dq converter 105 detects the detected values Iu_s and Iw_s of the u-phase current and the w-phase current output from the phase current sensors 63u and 63w, and the magnetic flux vector rotation angle position θmf calculated by the electrical angle converter 101. Based on the three-phase / dq conversion, a d-axis current detection value Id_s and a q-axis current detection value Iq_s are calculated.

  The current command determination unit 107 determines the command values Id_c and Iq_c for the d-axis current and the q-axis current supplied to the stator 57 of the electric motor 50 based on the torque command value Tr_c. The d-axis current command value Id_c determined by the current command determination unit 107 is input to the superimposing unit 109d. Further, the command value Iq_c of the q-axis current determined by the current command determination unit 107 is input to the superimposition unit 109q.

  The superimposing unit 109d adds the command value Id_c of the d-axis current and the value Id_h indicating the d-axis component of the harmonic current output from the harmonic current control unit 117, and outputs the added value Id_m. The added value Id_m of the d-axis component output from the superimposing unit 109d is input to the subtracting unit 111d. Similarly, the superimposing unit 109q adds the command value Iq_c of the q-axis current and the value Iq_h indicating the q-axis component of the harmonic current output from the harmonic current control unit 117, and outputs the added value Iq_m. To do. The q-axis component addition value Iq_m output from the superimposing unit 109q is input to the subtracting unit 111q.

  The subtractor 111d calculates a deviation ΔId between the added value Id_m of the d-axis component and the detected value Id_s of the d-axis current. The deviation ΔId calculated by the subtraction unit 111d is input to the current control unit 113. Similarly, the subtractor 111q calculates a deviation ΔIq between the q-axis component addition value Iq_m and the q-axis current detection value Iq_s. Deviation ΔIq calculated by subtraction unit 111q is input to current control unit 113.

  The current control unit 113 applies the deviation ΔId and ΔIq to the stator 57 of the electric motor 50 based on the deviations ΔId and ΔIq and the magnetic flux vector rotation angular velocity ωmf calculated by the electric angular velocity calculation unit 103 so that the deviation ΔId and the deviation ΔIq decrease. A command value Vd_c for the d-axis voltage and a command value Vq_c for the q-axis voltage are determined.

  The dq / 3-phase conversion unit 115 converts the d-axis voltage command value Vd_c and the q-axis voltage command value Vq_c determined by the current control unit 113 and the magnetic flux vector rotation angle position θmf calculated by the electrical angle conversion unit 101. Based on this, dq / 3-phase conversion is performed, and command values Vu_c, Vv_c, Vw_c of the three-phase voltages Vu, Vv, Vw applied to the stator 57 of the electric motor 50 are calculated. Each command value Vu_c, Vv_c, Vw_c of the three-phase voltage calculated by the dq / 3-phase conversion unit 115 is input to the PDU 11.

  The harmonic current control unit 117 determines a harmonic current component to be superimposed on the phase current output to the stator 57 of the electric motor 50. As shown in FIG. 2, the harmonic current control unit 117 includes a harmonic current amplitude determination unit 121, an amplitude weighting factor determination unit 123, a multiplication unit 125, a harmonic current phase determination unit 127, and a harmonic current determination. Unit 129 and dq converter 131. Note that the harmonic current amplitude determining unit 121, the amplitude weighting factor determining unit 123, and the harmonic current phase determining unit 127 determine desired values using different maps (look-up tables).

  The harmonic current amplitude determining unit 121 determines the amplitude component of the harmonic current based on the torque command value Tr_c. The amplitude weighting coefficient determination unit 123 determines an amplitude weighting coefficient in the harmonic current based on the magnetic flux vector rotation angular velocity ωmf calculated by the electrical angular velocity calculation unit 103. The multiplying unit 125 multiplies the amplitude component of the harmonic current determined by the harmonic current amplitude determining unit 121 by the amplitude weighting factor determined by the amplitude weighting factor determining unit 123.

  The harmonic current phase determination unit 127 determines the phase component of the harmonic current based on the torque command value Tr_c. Based on the multiplication result of the multiplier 125 and the phase component of the harmonic current determined by the harmonic current phase determination unit 127, the harmonic current determination unit 129 sets the magnetic flux vector rotation angle position θmf of the rotating magnetic field in the electric motor 50. Determine the corresponding harmonic current. The dq conversion unit 131 converts the harmonic current determined by the harmonic current determination unit 129 into each component on the dq axis. A value Id_h indicating the d-axis component of the harmonic current converted by the dq converter 131 is input to the superimposing unit 109d, and a value Iq_h indicating the q-axis component is input to the superimposing unit 109q.

  Next, the detail of the harmonic current in the electric motor system of this embodiment is demonstrated.

  As described above, a plurality of permanent magnets are concentrically arranged on the rotor 53 of the electric motor 50. In addition, a three-phase current is supplied to the stator 57 of the electric motor 50 via the PDU 11, and a rotating magnetic field is generated. When the permanent magnet of the rotor 53 receives the action of the attractive force and the repulsive force by the rotating magnetic field, the rotor 53 rotates around the rotation shaft 59. At this time, demagnetization occurs particularly in the corners of the permanent magnet. However, the degree of demagnetization differs for each corner of the permanent magnet, and also differs depending on the positional relationship between the armature and the permanent magnet constituting the stator 57. For this reason, during the rotation of the rotor 53, the location where the demagnetization occurs strongly in the permanent magnet, that is, the location where the permeance decreases, changes every moment.

  FIG. 3 shows a portion where the magnetic force and permeance acting on the permanent magnet of the rotor 53 are particularly lowered at every 30 electrical degrees when a three-phase current of a sine wave advanced by 30 degrees is supplied to the stator 57. FIG. As shown in FIG. 3, when the rotor 53 rotates as the electrical angle of the three-phase current changes, the location where the permeance of the permanent magnet decreases changes according to the position of the rotor 53 with respect to the armature. In the example shown in FIG. 3, the permeance change cycle is 120 degrees.

  FIG. 4 is a graph showing an example of a change in permeance of each corner portion of the pair of permanent magnets when the rotor 53 rotates. As shown in FIG. 4, the permeances of the eight corner portions 1 to 8 constituting the side surfaces of the pair of permanent magnets change according to the change of the electrical angle. In the example of FIG. 4, the permeance is less than the threshold value in an area of about 45 degrees to about 75 degrees and an area of about 85 degrees to about 130 degrees (about 10 degrees) among the eight corners 1 to 8. The number of corners is a predetermined number (for example, four) or more. Thus, when a three-phase current is supplied to the electric motor 50, the permanent magnet is easily affected by the demagnetizing field due to the rotating magnetic field of the stator 57 for each region of the electric angle.

  In addition, suppression of generation | occurrence | production of a demagnetization is realizable by reducing the level of the electric current supplied to the stator 57 of an electric motor. FIG. 5 is a graph showing an example of a BH curve (demagnetization curve) at one corner of the permanent magnet. As the rotor 53 rotates and the positional relationship between the rotor 53 and the stator 57 (that is, the electrical angle of the rotor 53) changes, the permeance decreases at a predetermined location (for example, a corner) of the permanent magnet. Then, at the predetermined location, the permeance straight line indicated by the straight line in FIG. 5 falls as indicated by the dotted arrow, and the operating point A indicated by the solid line circle moves to the operating point B indicated by the dotted circle. Since demagnetization occurs when the bending point of the BH curve shown in FIG. 5 is exceeded, demagnetization occurs at the operating point B. However, if the operating point moves from the operating point B to the operating point C by reducing the demagnetizing field as shown by the solid arrows, it is possible to suppress the occurrence of demagnetization even when the permeance is lowered. .

  In the present embodiment, a higher-order harmonic current component than the basic component is superimposed on the basic component obtained by converting the three-phase current supplied to the stator 57 of the electric motor 50 into the dq axis coordinate system. This suppresses the occurrence of demagnetization. At this time, the harmonic order n of the harmonic current component in the dq axis coordinate system is a value (= P × S) obtained by multiplying the number of poles P and the number of phases S of the electric motor 50 on the electrical angle. Here, the harmonic current component whose harmonic order is n in the dq-axis coordinate system means that it vibrates at a frequency n times the frequency of the three-phase current in the three-phase coordinate system in the dq-axis coordinate system. The order of the basic component in the dq axis coordinate system is 0 (that is, the basic component in the dq axis coordinate system is a constant value). Note that the nth-order current in the dq-axis coordinate system becomes an n + 1-order current waveform when inversely transformed into the three-phase coordinate system. The phase of the harmonic current is set so that the bottom portion of the amplitude of the harmonic current coincides with the electrical angle region in which the permanent magnet is easily affected by the demagnetizing field. For example, in the example shown in FIG. 4, the permanent magnet is easily affected by the demagnetizing field in the range of about 45 degrees to about 75 degrees in electrical angle and in the range of about 85 degrees to about 130 degrees (about 10 degrees). A harmonic current whose phase is 60 degrees and whose phase is shifted to about 60 degrees in the bottom portion of the amplitude is superimposed on the three-phase current.

  In addition, the electrical angle region in which the permanent magnet is easily affected by the demagnetizing field has a predetermined number (for example, 4) of the corners whose permeance is less than the threshold value among the eight corners 1 to 8 of the pair of permanent magnets. The range of electrical angles that satisfies the above condition. In the electric motor system of the present embodiment, simulation is performed on the electric motor 50, and it is recognized in advance in which electric angle region the permanent magnet is easily affected by the demagnetizing field.

  FIG. 6 is a graph showing waveforms of currents when a sixth-order harmonic current is superimposed on the dq axis on a three-phase current as a fundamental wave supplied to the stator of a two-pole three-phase motor. FIG. 7 is a diagram showing the vectors of the fundamental wave and the superimposed wave on the dq axis. FIG. 8 is a diagram showing the relationship between the d-axis current Id_c and the q-axis current Iq_c as the fundamental wave and the vector Ic. Hereinafter, the superposition of the harmonic current on the dq axis will be described with reference to FIGS.

  As shown in FIG. 8, the d-axis current Id_c and the q-axis current Iq_c as the fundamental wave and the vector Ic thereof are expressed by the following equation (1). γ represents the current phase of the fundamental wave.

  Sixth-order harmonics Id_h and Iq_h shown in (C) of FIG. 6 are expressed by the following equation (2). Α is the order of the harmonic current, β is the current phase of the harmonic, and θ is the electrical angle. When the order of the harmonic current is sixth, α = 6. As shown in FIG. 6C, the harmonic is a variable of the electric angle of the electric motor, and thus fluctuates according to the rotation of the electric motor.

  The relationship of equation (2) is shown in FIG. When the harmonic current is superimposed on the fundamental wave on the dq axis, the superimposed waves Id_m and Iq_m are expressed by the following equation (3). As shown in FIG. 7, the vector Im of the superimposed waves Id_m and Iq_m is a combination of the fundamental wave vector Ic and the harmonic Ih vector.

  The vector magnitude Im of the superimposed waves Id_m and Iq_m is expressed by the following equation (4).

  When the value indicated by the underline on the right side of Expression (4) is minimum, the size of the vector Im shown in Expression (4) is also minimum. Therefore, the harmonic current phase determination unit 127 determines the phase β of the harmonic so that the bottom of the value indicated by the underline coincides with a low-permeance region (for example, 50 degrees).

  Note that the superposition of the high frequency described above may be performed only in the regions indicated by I and II in the operating point region of the electric motor 50 shown in FIG. Further, the harmonic amplitude may be changed as (Ia in region I)> (Ia in region II). Further, for example, harmonics may be superimposed when the ambient temperature T measured from the temperature of the cooling ATF exceeds the threshold Th.

  The harmonic current control unit 117 of the ECU 100 determines the frequency, phase, and amplitude of the harmonic current described above. That is, the harmonic current amplitude is determined by the harmonic current amplitude determining unit 121, the amplitude weighting coefficient determining unit 123, and the multiplying unit 125 of the harmonic current control unit 117, and the harmonic current phase determining unit 127 determines the phase of the harmonic current. Is determined. The fundamental frequency of the harmonic current is the same as the frequency of the fundamental current detected by the rotational position sensor 61 such as a resolver.

  As described above, according to the electric motor system of the present embodiment, a sinusoidal harmonic current having a frequency higher than that of the three-phase current is superimposed on the three-phase current supplied to the stator 57 of the electric motor 50. The phase of the harmonic current is such that the permanent magnet in the rotor 53 of the electric motor 50 is easily demagnetized due to the influence of the demagnetizing field due to the rotating magnetic field of the stator 57 (that is, the electric current during rotation of the rotor). In the angle region, the bottom portion of the amplitude of the same harmonic current is determined to coincide with an electrical angle region in which the permeance with respect to the rotating magnetic field at the corner of the permanent magnet is relatively small. As a result, in the electrical angle region in which the permanent magnet is easily demagnetized due to the influence of the demagnetizing field, the current level on which the harmonic current supplied to the stator 57 is superimposed is smaller than the three-phase current. For this reason, the demagnetizing field in the electrical angle region is reduced, and the occurrence of demagnetization can be suppressed.

  The motor system according to the present embodiment has the above-described control for adjusting the bottom of the amplitude of the harmonic current to the electrical angle region in which the permanent magnet is easily affected by the demagnetizing field, and even if the permanent magnet is affected by the demagnetizing field. In the electrical angle region where demagnetization is difficult (that is, the electrical angle region where the permeance of the corner of the permanent magnet is relatively large in the electrical angle region during rotation of the rotor), the peak portion of the harmonic current amplitude is You may adjust the frequency of a harmonic current so that it may correspond. In addition, as shown in FIG. 4, the electrical angle region in which the permanent magnet is difficult to demagnetize even if it is affected by the demagnetizing field has a permeance threshold value among the eight corners 1 to 8 of the pair of permanent magnets. This is a range of electrical angles that satisfies the condition that the number of corners is a predetermined number (for example, four) or more. In the electrical angle region where the permanent magnet is not easily affected by the demagnetizing field, the level of the current on which the harmonic current supplied to the stator 57 is superimposed is greater than the three-phase current. For this reason, the torque in the said electrical angle area | region increases and the electric motor 50 can output desired torque.

  In addition, in the electric motor system of this embodiment, based on the condition that the number of corners whose permeance is less than the threshold value among the eight corners 1 to 8 of the pair of permanent magnets is a predetermined number or more, The electrical angle region in which the permanent magnet is susceptible to the demagnetizing field is determined. At this time, the eight corners 1 to 8 of the pair of permanent magnets are divided into inner corners 1, 2, 7, and 8 and outer corners 3, 4, 5, and 6, and the same electrical angle. An area may be determined. FIG. 10 is a graph showing an example of a BH curve (demagnetization curve) on the outer diameter side and inner diameter side of the corner portion of the permanent magnet. As shown in FIG. 10, the corner portion on the outer diameter side of the permanent magnet receives a larger demagnetizing field than the inner diameter side. That is, since the corner portion on the outer diameter side of the permanent magnet is closer to the stator 57 than the corner portion on the inner diameter side, it is easily affected by the demagnetizing field and is easily demagnetized. On the other hand, the corner on the inner diameter side is less affected by the demagnetizing field than the corner on the outer diameter side. Thus, by changing the electrical angle of the rotor 53, demagnetization is likely to occur beyond the bending point at the corner on the outer diameter side, and demagnetization is less likely to occur at the corner on the inner diameter side. For this reason, the demagnetization at the corner portion on the inner diameter side is easier to suppress, and the amplitude of the harmonic current can be reduced as compared with the case where the occurrence of demagnetization at the corner portion on the outer diameter side is suppressed. For this reason, in the electric motor system of another embodiment, as shown in FIG. 11, of the corners 1, 2, 7, and 8 on the inner diameter side of the pair of permanent magnets, the permeance is less than the threshold. Based on the condition that the number is a predetermined number (for example, three) or more, an electrical angle region in which the permanent magnet is easily affected by the demagnetizing field may be determined. In this embodiment, an increase in power consumption when the harmonic current is superimposed can be suppressed.

50 Electric motor 51 Permanent magnet 53 Rotor 55 Armature 57 Stator 59 Rotating shaft 100 ECU
11 PDU
13 Battery 101 Electrical angle conversion unit 103 Electrical angular velocity calculation unit 105 Three-phase / dq conversion unit 107 Current command determination unit 109d, 109q Superimposition unit 111d, 111q Subtraction unit 113 Current control unit 115 dq / 3-phase conversion unit 117 Harmonic current control Unit 61 rotational position sensor 63u, 63w phase current sensor 121 harmonic current amplitude determining unit 123 amplitude weighting factor determining unit 125 multiplying unit 127 harmonic current phase determining unit 129 harmonic current determining unit 131 dq converting unit

Claims (6)

A rotor having a magnetic pole array composed of a plurality of permanent magnets arranged at predetermined intervals in the circumferential direction;
A plurality of armatures arranged at predetermined intervals in the circumferential direction are arranged to face the magnetic pole row, and are moved in the circumferential direction by armature magnetic poles generated in the plurality of armatures in response to power supply. And a stator having an armature row that generates a rotating magnetic field between the magnetic pole row and a motor control device,
A current component determining unit that determines a basic component of a current to be supplied to the motor in accordance with an operation state of the motor and a required output for the motor;
A harmonic current control unit for determining a harmonic current component having a frequency higher than the current supplied to the electric motor;
A superimposing unit that superimposes the harmonic current component determined by the harmonic current control unit on a basic component of current supplied to the electric motor,
The harmonic current control unit has a bottom of the amplitude of the harmonic current in an electrical angle region where the permeance of the corner portion of the permanent magnet with respect to the rotating magnetic field is relatively small in the electrical angle region during rotation of the rotor. A control device for an electric motor, wherein a component of the harmonic current is determined so that the portions coincide with each other. The motor control device according to claim 1,
The electrical angle region having a relatively small permeance is a range of electrical angles that satisfies a condition that the number of corners having a permeance less than a threshold value is not less than a predetermined number among corners of the permanent magnet. An electric motor control device. The motor control device according to claim 1 or 2,
The harmonic current control unit has an amplitude peak of the harmonic current in an electrical angle region where the permeance of the corner portion of the permanent magnet with respect to the rotating magnetic field is relatively large in the electrical angle region during rotation of the rotor. A control device for an electric motor, wherein a component of the harmonic current is determined so that the portions coincide with each other. The motor control device according to claim 3,
The electrical angle region where the permeance is relatively large is a range of electrical angles satisfying a condition that the number of corners whose permeance is equal to or greater than a threshold value among the corners of the permanent magnet is equal to or greater than a predetermined number An electric motor control device. The motor control device according to claim 1, 3 or 4,
Two adjacent permanent magnets constituting the plurality of permanent magnets are arranged in a V shape that opens toward the outer peripheral surface of the rotor when viewed from the rotation axis direction of the electric motor,
The electrical angle region susceptible to the influence of the demagnetizing field has a predetermined number or more of corners whose permeance is less than a threshold value among corners on the inner diameter side of the two permanent magnets arranged in the V shape. An electric motor control device having a range of electrical angles that satisfies the condition of. A control device for an electric motor according to any one of claims 1 to 5,
The harmonic motor order in the dq axis coordinate system of the harmonic current component supplied to the motor is a value obtained by multiplying the number of poles and the number of phases of the motor.

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