Magnetic pole direction detection device and magnetic pole direction detection method

Abstract

The present invention provides a magnetic pole direction detection device and a magnetic pole direction detection method for accurately detecting the magnetic poles of a synchronous motor having salient polarity. The magnetic pole direction detection device for detecting the magnetic pole direction of a synchronous motor having salient polarity comprises: a high-frequency voltage application unit that applies a high-frequency voltage to the motor; an excitation phase change unit that changes the excitation phase of the motor to an arbitrary phase; a drive current detection unit that detects the drive current value of the motor; a magnetic pole direction estimation unit that detects the magnetic pole direction based on the excitation phase and the drive current value; a measurement unit that measures the inductance value of the motor; and a control unit that changes the frequency of the high-frequency voltage applied by the high-frequency voltage application unit based on the inductance value measured by the measurement unit.

Description

Technical Field

[0001] The present invention relates to a magnetic pole direction detection device and a magnetic pole direction detection method. Background Art

[0002] Conventional methods exist for detecting magnetic poles in synchronous motors with salient polarity while the motor remains stationary. Patent Document 1 discloses a technique in which a low-amplitude high-frequency voltage is applied to the motor while varying the motor's excitation phase. The technique then measures the feedback current value at each phase and estimates the magnetic pole direction based on the magnitude of the feedback current value.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-130582 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, when the inductance is large, the feedback current value is small and easily affected by noise. Therefore, the detection result of the magnetic pole direction is prone to errors, and even if the magnetic pole direction is estimated multiple times, the detection result will have large deviations.

[0008] Solutions for solving problems

[0009] One embodiment of the present invention provides a magnetic pole direction detection device (for example, the magnetic pole direction detection device 1 described later) for detecting the magnetic pole direction of a synchronous motor with salient polarity (for example, the motor 10 described later), the magnetic pole direction detection device comprising: a high-frequency voltage applying unit (for example, the high-frequency voltage applying unit 2 described later), which applies a high-frequency voltage to the motor; an excitation phase changing unit (for example, the excitation phase changing unit 3 described later), which changes the excitation phase of the motor to an arbitrary phase; a driving current detecting unit (for example, the driving current detecting unit 4 described later), which detects the driving current value of the motor; a magnetic pole direction estimating unit (for example, the magnetic pole direction estimating unit 5 described later), which performs magnetic pole direction estimation based on the excitation phase and the driving current value under the application of the high-frequency voltage; a measuring unit (for example, the measuring unit 6 described later), which measures the inductance value of the motor; and a control unit (for example, the control unit 7 described later), which changes the frequency of the high-frequency voltage applied by the high-frequency voltage applying unit based on the inductance value measured by the measuring unit.

[0010] In addition, one embodiment of the present invention provides a magnetic pole direction detection method for detecting the magnetic pole direction of a synchronous motor with salient polarity, the magnetic pole direction detection method including: a high-frequency voltage application process for applying a high-frequency voltage to the motor; an excitation phase change process for changing the excitation phase of the motor to an arbitrary phase; a drive current detection process for detecting the drive current value of the motor; a magnetic pole direction estimation process for performing magnetic pole direction estimation based on the excitation phase and the drive current value under the application of the high-frequency voltage; a measurement process for measuring the inductance value of the motor; and an applied voltage frequency change process for changing the frequency of the high-frequency voltage applied in the high-frequency voltage application process based on the inductance value measured in the measurement process.

[0011] Effects of the Invention

[0012] According to the present invention, it is possible to provide a magnetic pole direction detection device that can accurately detect the magnetic poles of a synchronous motor having salient polarity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a block diagram showing the configuration of a magnetic pole direction detection device according to one embodiment of the present invention.

[0014] Figure 2A This is an explanatory diagram for explaining the direction of magnetic poles in a magnet-embedded motor.

[0015] Figure 2B This is an explanatory diagram for explaining the direction of magnetic poles in a reluctance motor.

[0016] Figure 3A This diagram explains the relationship between inductance and the time differential value of current in a magnet-embedded motor.

[0017] Figure 3B This diagram explains the relationship between inductance and time differential value of current in a reluctance motor.

[0018] Figure 4 This is a diagram showing the time differential value of current with respect to the change of the excitation phase.

[0019] Figure 5A It is a graph showing the estimated magnetic pole direction when a high-frequency voltage is applied.

[0020] Figure 5B It is a graph showing the estimated magnetic pole direction when a low-frequency high-frequency voltage is applied.

[0021] Figure 6A This is a graph showing the relationship between the time differential value of the current and the current value when a high-frequency voltage of a high frequency is applied.

[0022] Figure 6B This is a graph showing the relationship between the time differential value of the current and the current value when a low-frequency high-frequency voltage is applied.

[0023] Figure 7 This is a graph illustrating the dependence of current value on inductance.

[0024] Figure 8 This is a flowchart illustrating a magnetic pole direction detection method according to one embodiment of the present invention.

[0025] Description of Reference Numerals

[0026] 1: Magnetic pole direction detection device; 2: High-frequency voltage application unit; 3: Excitation phase change unit; 4: Drive current detection unit; 5: Magnetic pole direction estimation unit; 6: Measurement unit; 7: Control unit; 8: Magnetic pole position detection unit; 10, 20: Electric motor; 11, 21: Rotor; 12, 22: Iron core; 13: Permanent magnet. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto.

[0028] Figure 1 A block diagram showing the configuration of a magnetic pole direction detection device according to one embodiment of the present invention.

[0029] The magnetic pole direction detection device 1 of this embodiment includes a high-frequency voltage application unit 2, an excitation phase change unit 3, a drive current detection unit 4, a magnetic pole direction estimation unit 5, a measurement unit 6, a control unit 7, and a magnetic pole position detection unit 8. The magnetic pole direction detection device 1 can accurately detect the magnetic pole direction of a synchronous motor 10 having salient polarity.

[0030] The synchronous motor 10 to be detected as the magnetic pole direction is not particularly limited as long as it is a motor having salient polarity. For example, it may be Figure 2A The magnet embedded motor 10 shown in FIG. 1 is a motor in which an iron core 12 is arranged on a rotor 11 and a permanent magnet 13 is embedded inside the rotor 11. Figure 2B The reluctance motor 20 shown has only an iron core 22 disposed on a rotor 21. These motors 10 and 20 have different inductances around the rotation axes of the rotors 11 and 21 due to the asymmetry of the iron cores 12 and 22 and permanent magnets 13 disposed on the rotors 11 and 21. The following description will primarily focus on the embodiment using the embedded magnet motor 10 as the test object, but will also include descriptions of the reluctance motor 20 as the test object as appropriate.

[0031] The high-frequency voltage application unit 2 can apply a high-frequency voltage to the rotor 11 of the motor 10. The excitation phase change unit 3 changes the excitation phase of the motor 10 applied by the high-frequency voltage application unit 2. The drive current detection unit 4 detects the drive current flowing in the motor 10 by applying the high-frequency voltage. The magnetic pole direction estimation unit 5 estimates the magnetic pole direction of the motor 10 based on the excitation phase of the motor 10 and the value of the drive current detected by the drive current detection unit 4 under the application of the high-frequency voltage.

[0032] The value of the drive current flowing in the motor 10 by applying the high-frequency voltage changes according to the excitation phase of the motor 10 when the high-frequency voltage is applied. By changing the excitation phase θ in the range of 0° ≤ θ ≤ 180° by the excitation phase change unit 3 and detecting the value of the drive current by the drive current detection unit 4, the relationship between the drive current value i and the excitation phase θ at this voltage frequency can be investigated. The excitation phase of the motor 10 can be changed, for example, by rotating the rotor 11.

[0033] Here, the magnetic pole direction detected by the magnetic pole direction detection device 1 of the present embodiment will be described. As Figure 2A shown, let the rotation angle of the rotor 11 be θ. When the S pole of the magnet faces the rotor 11 from the outside, the angular position θ of the rotor 11 when it rotates toward this S pole is called the magnetic pole position (D phase) of the rotor 11, and the direction of the straight line (D axis) connecting the rotation center of the rotor 11 and the magnetic pole position is the magnetic pole direction. In addition, the Q axis is orthogonal to the D axis in the rotation plane of the rotor 11.

[0034] For example, in Figure 2A the rotor 11 of the magnet-embedded motor 10 shown, the direction extending along the N-S poles of the embedded permanent magnet 13 is the magnetic pole direction. In addition, in Figure 2B the rotor 21 of the reluctance motor 20 shown, the long side direction of the iron core 12 schematically drawn as a rectangle is the magnetic pole direction.

[0035] As described above, in a synchronous motor with salient poles, the D-phase inductance Ld and the Q-phase inductance Lq become different values due to the asymmetry of the rotor structure. Inductance is an index indicating the ease of passage of magnetic flux. In the rotor 11 of the magnet-embedded motor 10, Ld < Lq, and in the rotor 21 of the reluctance motor 20, Lq < Ld.

[0036] The magnetic pole direction detection device 1 of the present embodiment detects the magnetic pole direction based on the amplitude of the current time differential value (di / dt) obtained by differentiating the current value i with respect to time t. The current time differential value is expressed by the following formula (1) and changes periodically with the change of the excitation phase θ.

[0037]

[0038] in,

[0039] L0=(L d +L q ) / 2

[0040] L2=(L d -L q ) / 2

[0041] θ(t): Phase of the applied voltage at time t

[0042] θ p : Magnetic pole position

[0043] Vsinγt: high frequency voltage

[0044] like Figure 3A and Figure 3B As shown in FIG. 1 , the magnitude of the inductance is negatively correlated with the magnitude of the amplitude of the time differential value of the current. That is, for example, in the case of the magnet embedded motor 10, when the amplitude of the time differential value of the current reaches a minimum value, the inductance reaches a maximum value Lq. In addition, when the amplitude of the time differential value of the current reaches a maximum value, the inductance reaches a minimum value Ld ( Figure 3A In the case of the reluctance motor 20, when the amplitude of the current time differential value takes a minimum value, the inductance takes a maximum value Ld. In addition, when the amplitude of the current time differential value takes a maximum value, the inductance takes a minimum value Lq ( Figure 3B ).

[0045] Therefore, by varying the excitation phase θ within the range of 0° ≤ θ ≤ 360° at time t, detecting the minimum or maximum amplitude of the current-time differential value and outputting the excitation phase at that time, the magnetic pole direction can be estimated. Specifically, in the case of the aforementioned embedded magnet motor 10, when the amplitude of the current-time differential value reaches its maximum value, the inductance is Ld. When the excitation phase at that time is θ1, the magnetic pole direction is θ1 + n × 180° (0° ≤ θ1 ≤ 180°, where n is an integer). In the case of the reluctance motor 20, when the amplitude of the current-time differential value reaches its minimum value, the inductance is Ld. When the excitation phase at that time is θ2, the magnetic pole direction is θ2 + n × 180° (0° ≤ θ2 ≤ 180°, where n is an integer).

[0046] Figure 4 This graph shows the relationship between the drive current value and the excitation phase. Under constant high-frequency voltage application, the current value and the excitation phase θ are observed over time, and the magnetic pole direction is estimated based on the excitation phase θ when the amplitude of the time-differential current value reaches a minimum.

[0047] The time differential value of the current changes periodically as θ increases, and its maximum and minimum values each appear twice in each cycle. Therefore, by estimating the values of the excitation phase θ corresponding to multiple maximum and minimum values and averaging them, the magnetic pole direction can be estimated with higher accuracy. Thus, it is preferable to change the excitation phase by more than one cycle for estimating the magnetic pole direction.

[0048] Regarding the estimation of the magnetic pole direction, it is also possible to detect either the maximum or minimum value of the amplitude of the time differential value of the current. However, it is particularly preferable to detect the maximum value for estimating the magnetic pole direction. This is because the amplitude of the time differential value of the current changes more sharply at its maximum value than at its minimum value, so it is less affected by noise, thereby improving the detection accuracy. In the case of the magnet-embedded motor 10 with Ld < Lq, the excitation phase at which the detected maximum value is taken is directly estimated as the magnetic pole direction. In the case of the reluctance motor 20 with Lq < Ld, the phase shifted by 90° from the excitation phase at which the detected maximum value is taken is estimated as the magnetic pole direction. Thus, for example, the rotor 11 is rotated S cycles and the maximum values that appear 2S times are detected to estimate the magnetic pole direction.

[0049] Figure 5A and Figure 5B show the results obtained by estimating the magnetic pole direction by changing the frequency of the high-frequency voltage. In Figure 5B show the results when a high-frequency voltage with a frequency lower than Figure 5A is applied. Figure 5B The current value detected by one side is larger, and the deviation in estimating the magnetic pole direction is smaller.

[0050] When changing the frequency of the applied high-frequency voltage, the current value increases when the frequency is decreased, so the magnetic pole direction can be detected with higher accuracy. This will be described in detail. Figure 6A and Figure 6B are graphs showing the time variations of the time differential value of the current and the current value side by side. Figure 6B show the results when a high-frequency voltage with a frequency lower than Figure 6A is applied. t1 and t2 represent the time t for half a cycle, i1 and i2 represent the amplitudes of the current i, and t1 < t2, i1 < i2.

[0051] According to formula (1), the amplitude of the current-time differential value depends only on θ and inductance, so even if the frequency of the high-frequency voltage is reduced, the amplitude of the current-time differential value remains constant. On the other hand, when the frequency is reduced, the wavelength increases, so t2 becomes larger than t1. As a result, when the frequency of the applied voltage is reduced, the area of ​​the shaded portion of the current-time differential value curve increases. Since the current-time differential value curve is obtained by differentiating the current value with time, the area of ​​the shaded portion of the current-time differential value curve represents the amplitude of the corresponding current value curve. Therefore, when the frequency of the applied high-frequency voltage is changed, the current value increases when the frequency is reduced.

[0052] On the other hand, excessively high current values ​​can cause disadvantages such as increased heating of motor 10. Therefore, it is preferable to vary the frequency of the applied voltage within an appropriate current range as the current applied to motor 10. Motor 10 also includes a limiter. If an upper limit is set for the current flowing through motor 10 to prevent overcurrent, excessively high current values ​​will prevent accurate measurement of temporal changes, making it impossible to accurately detect the maximum and minimum values ​​of the current-time differential. Therefore, in this case, it is preferable to vary the frequency of the applied voltage within a range where the current value is below the set upper limit.

[0053] In the case where the motor to be detected is a magnet embedded motor 10, it is preferable to be able to further detect the magnetic pole position by the magnetic pole position detection unit 8. As a method for detecting the magnetic pole position, a conventionally known method can be used, for example, the following method can be used for detection. First, an external magnetic field is applied to the motor 10 in parallel with the magnetic pole direction detected by the magnetic pole direction detection device 1. Then, the sign of the external magnetic field is reversed. When the direction of application of the external magnetic field is the same as the direction of the magnetic field formed by the permanent magnet 13, magnetic saturation occurs, and the inductance decreases compared to when a magnetic field in the opposite direction is applied, so the change in the current value increases. This property can be used to detect the magnetic pole position.

[0054] And, as Figure 7 As shown, the inductance value depends on the current value, decreasing as the current value increases. Specifically, as the current value increases in the excitation phase where the amplitude of the time differential current value is larger, the inductance decreases, and thus the amplitude of the time differential current value increases further. As a result, the amplitude of the time differential current value changes more dramatically at its maximum value than at its minimum value, making it less susceptible to noise and enabling highly accurate detection of the magnetic pole direction.

[0055] Measuring unit 6 measures the inductance of motor 10 while varying the excitation phase to which a high-frequency voltage is applied. The measurement method is not particularly limited; for example, a conventionally known method for calculating the inductance from the measured voltage and current values ​​may be used. The inductance value may be measured at an order of magnitude.

[0056] The control unit 7 changes the frequency of the high-frequency voltage applied by the high-frequency voltage applicator 2 based on the inductance value measured by the measuring unit 6. A threshold value for the inductance is preset. When the inductance exceeds the threshold, the detected current value is small and susceptible to noise. Therefore, the frequency of the applied voltage is changed to a lower value. This increases the current value and improves the detection accuracy of the current value.

[0057] Next, use Figure 8 An example of magnetic pole direction detection according to this embodiment is described with reference to the flowchart of FIG.

[0058] First, the threshold value of the inductance is set according to the target accuracy (step S1). Then, in the high-frequency voltage application process, the high-frequency voltage application unit 2 applies a high-frequency voltage of frequency A to the rotor 11 of the motor 10 (step S2). Then, in the excitation phase change process, the excitation phase θ of the motor 10 is changed by the excitation phase change unit 3 for S cycles, and in the drive current detection process, the drive current detection unit 4 detects the drive current flowing in the motor 10. Then, in the magnetic pole direction detection process, the magnetic pole direction estimation unit 5 estimates the magnetic pole direction of the motor 10 based on the drive current detected 2S times by the drive current detection unit 4 and the excitation phase θ at that time. Then, in the measurement process, the measurement unit 6 measures the inductance value of the motor 10 under the applied voltage of frequency A (step S3).

[0059] Next, the control unit 7 compares the inductance value measured at the applied voltage at frequency A with the threshold value set in step S1 (step S4). If the inductance value is below the predetermined threshold value, the magnetic pole direction estimation result related to the inductance value is output as the magnetic pole direction detection result of the motor 10 (step S6). If the inductance value is greater than the predetermined threshold value, the frequency of the high-frequency voltage applied during the high-frequency voltage application step is changed to frequency B, which is lower than frequency A, and steps S2 to S4 are repeated (step S5).

[0060] Repeat this step to reduce the frequency of the applied voltage until the inductance value becomes below a specified threshold value. When the inductance value becomes below the specified threshold value, the magnetic pole direction estimation result related to the inductance value is output as the magnetic pole direction detection result (step S6).

[0061] As described above, a magnetic pole direction detection result with small deviation and high precision can be obtained. Further, when the motor to be detected is the magnet-embedded motor 10, after step S6, an external magnetic field can also be applied to the motor 10 in two directions parallel to the magnetic pole direction by the magnetic pole position detection unit 8, thereby further detecting the magnetic pole position.

[0062] As described above, the magnetic pole direction detection device 1 according to one embodiment of the present invention has been described. According to the present invention, the following effects can be obtained.

[0063] (1) One embodiment of the present invention is a magnetic pole direction detection device 1 for detecting the magnetic pole direction of a salient-pole synchronous motor 10. The magnetic pole direction detection device 1 includes: a high-frequency voltage application unit 2 that applies a high-frequency voltage to the motor 10; an excitation phase change unit 3 that changes the excitation phase of the motor 10 to an arbitrary phase; a drive current detection unit 4 that detects the drive current value of the motor 10; a magnetic pole direction estimation unit 5 that performs magnetic pole direction estimation based on the excitation phase and the drive current value under the application of the high-frequency voltage; a measurement unit 6 that measures the inductance value of the motor 10; and a control unit 7 that changes the frequency of the high-frequency voltage applied by the high-frequency voltage application unit 2 based on the inductance value measured by the measurement unit 6. Thus, high-precision magnetic pole direction detection can be performed.

[0064] (2) The magnetic pole direction detection device 1 further includes a magnetic pole position detection unit 8 that can apply an external magnetic field to the motor 10 in two directions parallel to the detected magnetic pole direction. Thus, the magnetic pole position can be detected with high precision.

[0065] (3) The excitation phase change unit 3 of the magnetic pole direction detection device 1 rotates the motor 10 for S cycles (S is an integer of 1 or more). Thus, the accuracy of deviation calculation is improved, and therefore the magnetic pole direction can be detected with higher precision.

[0066] (4) The magnetic pole direction estimation unit 5 of the magnetic pole direction detection device 1 detects the excitation phase when the time differential value of the drive current value is maximum, and estimates this excitation phase as the magnetic pole direction when Ld < Lq, and estimates the phase changed by 90° with respect to this excitation phase as the magnetic pole direction when Lq < Ld. Thus, the accuracy of current value detection is improved, and therefore the magnetic pole direction can be detected with higher precision.

[0067] (5) In addition, one embodiment of the present disclosure provides a magnetic pole direction detection method for detecting the magnetic pole direction of a synchronous motor 10 having salient polarity, the magnetic pole direction detection method comprising the following steps: a high-frequency voltage application step of applying a high-frequency voltage to the motor 10; an excitation phase change step of changing the excitation phase of the motor 10 to an arbitrary phase; a drive current detection step of detecting the drive current value of the motor 10; a magnetic pole direction estimation step of estimating the magnetic pole direction based on the excitation phase and the drive current value under the application of the high-frequency voltage; a measurement step of measuring the inductance value of the motor 10; and an applied voltage frequency change step of changing the frequency of the high-frequency voltage applied in the high-frequency voltage application step based on the inductance value measured in the measurement step. Thus, high-precision magnetic pole direction detection can be performed.

Claims

1. A magnetic pole direction detection device for detecting the magnetic pole direction of a synchronous motor having salient polarity, the magnetic pole direction detection device comprising: a high-frequency voltage applying unit for applying a high-frequency voltage to the motor; an excitation phase changing unit configured to change the excitation phase of the motor to an arbitrary phase; a driving current detection unit configured to detect a driving current value of the motor; a magnetic pole direction estimation unit that estimates the magnetic pole direction based on the excitation phase and the drive current value under application of the high-frequency voltage; a measuring unit configured to measure an inductance value of the motor; as well as A control unit changes the frequency of the high-frequency voltage applied by the high-frequency voltage applying unit based on the inductance value measured by the measuring unit.

2. The magnetic pole direction detection device according to claim 1, wherein: The magnetic pole direction detection device further includes a magnetic pole position detection unit capable of applying an external magnetic field to the motor in two directions parallel to the detected magnetic pole direction.

3. The magnetic pole direction detection device according to claim 1 or 2, characterized in that: The excitation phase changing unit changes the excitation phase by 360° or more.

4. The magnetic pole direction detection device according to claim 1, wherein: The magnetic pole direction estimation unit detects the excitation phase when the time differential value of the drive current value is maximum, and estimates a phase that is 90° different from the detected excitation phase as the magnetic pole direction.

5. A method for detecting a magnetic pole direction of a synchronous motor having salient polarity, the method comprising the following steps: a high-frequency voltage applying step of applying a high-frequency voltage to the motor; an excitation phase changing step of changing the excitation phase of the motor to an arbitrary phase; a driving current detection step of detecting a driving current value of the motor; a magnetic pole direction estimating step of estimating the magnetic pole direction based on the excitation phase and the drive current value under application of the high-frequency voltage; a measuring step of measuring the inductance value of the motor; as well as The applied voltage frequency changing step changes the frequency of the high-frequency voltage applied in the high-frequency voltage applying step based on the inductance value measured in the measuring step.

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