Drive devices and driving methods for synchronous motors

Abstract

This invention provides a driving device and a driving method for a synchronous motor. The driving device for the synchronous motor includes a current detection unit for detecting the phase current flowing through the synchronous motor; and a pole position calculation unit for calculating the pole position of the rotor of the synchronous motor based on the phase current detected by the current detection unit. The pole position calculation unit includes: a first peak-to-peak detector for detecting a first peak-to-peak value representing the difference between the maximum and minimum values ​​of the phase current; a quadrature component detector for detecting quadrature components based on the phase current; and a second peak-to-peak detector for detecting a second peak-to-peak value representing the difference between the maximum and minimum values ​​of the quadrature components. When the synchronous motor stops, a first pole position is calculated based on the first peak-to-peak value and the second peak-to-peak value, and an initial pole position of the rotor is calculated based on the first pole position.

Description

Technical Field

[0001] This invention relates to a drive device for a synchronous motor and a drive method for a synchronous motor. Background Technology

[0002] Electric vehicles, such as hybrid vehicles and electric vehicles, use permanent magnet synchronous motors (hereinafter referred to as synchronous motors) with permanent magnets embedded in the rotor. Synchronous motors are broadly classified into embedded magnet type synchronous motors (where permanent magnets are embedded in the rotor) and surface magnet type synchronous motors (where permanent magnets are disposed on the surface of the rotor). In electric vehicles, embedded magnet type synchronous motors are mostly used to drive the vehicle, while surface magnet type synchronous motors are used in electric power steering and electric braking systems. To control such synchronous motors, inverters, acting as power converters, are typically used. Current vector control is a commonly known method for controlling the torque of a synchronous motor using an inverter. For current vector control, it is necessary to accurately determine the magnetic pole positions of the synchronous motor's rotor. As one means of determining these magnetic pole positions, a rotary transformer, acting as a position sensor, is usually incorporated into the synchronous motor.

[0003] However, the inclusion of a rotary transformer in a synchronous motor increases the number of components, the size of the system, and the cost. Furthermore, the output winding used to output position signals is wound in the rotary transformer, which is susceptible to failure due to wire breaks or short circuits, thus reducing system reliability.

[0004] Therefore, sensorless vector control is a commonly known technology for driving synchronous motors without using sensors such as resolvers. Sensorless vector control obtains rotor position information by detecting or calculating the induced voltage of the synchronous motor, and then performs current vector control. Since sensorless vector control eliminates the need for position sensors such as resolvers, it avoids the aforementioned problems caused by position sensors, such as system enlargement, increased cost, and reduced reliability.

[0005] To perform sensorless vector control, the rotor position (initial pole position) of the synchronous motor must be detected while it is stopped. However, the induced voltage of the synchronous motor cannot be detected or calculated when it is stopped. Therefore, alternative methods are needed to detect or calculate the initial pole position.

[0006] Patent documents 1 and 2 are known methods for calculating the initial magnetic pole position of a synchronous motor. Patent document 1 discloses a method for calculating the initial magnetic pole position using the salient polarity of the synchronous motor. Patent document 2 discloses a method for calculating the initial magnetic pole position using magnetic saturation.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2002-78391

[0010] Patent Document 2: Japanese Patent Application Publication No. 2016-171741 Summary of the Invention

[0011] The technical problem that the invention aims to solve

[0012] Synchronous motors with salient polarity exhibit a property where the inductance changes depending on the rotor position. Patent Document 1 utilizes this rotor position dependence of inductance to apply a high-order harmonic voltage to the synchronous motor, and calculates the initial magnetic pole position based on the detected current generated in the synchronous motor. However, in the case of non-salient polarity synchronous motors such as surface magnet type synchronous motors, this rotor position dependence of inductance cannot be obtained. Therefore, while the initial magnetic pole position calculation method in Patent Document 1 can be applied to embedded magnet type synchronous motors, it has the technical problem of not being applicable to surface magnet type synchronous motors.

[0013] Furthermore, when voltages are applied sequentially to the three phases of a synchronous motor, the inductance decreases due to magnetic saturation when a voltage is applied to a phase near the initial magnetic pole position, causing a change in current magnitude. Patent Document 2 utilizes the magnetic saturation of such a synchronous motor to calculate the initial magnetic pole position. This method has the advantage of being applicable to either embedded magnet type synchronous motors or surface magnet type synchronous motors. However, it suffers from a technical problem where magnetic flux in the same direction as the permanent magnet and magnetic flux in the direction orthogonal to it interfere with each other, resulting in significant errors in the calculation of the magnetic pole position.

[0014] Therefore, the object of the present invention is to provide a driving device and driving method for a synchronous motor that can be applied to either an embedded magnet type synchronous motor or a surface magnet type synchronous motor and can accurately calculate the initial magnetic pole position.

[0015] Technical means for solving technical problems

[0016] The synchronous motor drive device of the present invention includes: a power converter that sequentially applies positive and negative voltages to each phase of the synchronous motor to drive the synchronous motor; a current detection unit that detects the phase current flowing through the synchronous motor; and a magnetic pole position calculation unit that calculates the magnetic pole position of the rotor of the synchronous motor based on the phase current detected by the current detection unit. The magnetic pole position calculation unit includes: a first peak-to-peak detector for detecting a first peak-to-peak value representing the difference between the maximum and minimum values ​​of the phase current; a quadrature component detector for detecting the quadrature component of the phase current; and a second peak-to-peak detector for detecting a second peak-to-peak value representing the difference between the maximum and minimum values ​​of the quadrature component. When the synchronous motor stops, a first magnetic pole position is calculated based on the first peak-to-peak value detected by the first peak-to-peak detector and the second peak-to-peak value detected by the second peak-to-peak detector, and an initial magnetic pole position of the rotor is calculated based on the first magnetic pole position.

[0017] The synchronous motor driving method of the present invention is a driving method of a synchronous motor by a driving device for a synchronous motor. The driving device includes: a power converter that sequentially applies positive and negative voltages to each phase of the synchronous motor to drive the synchronous motor; and a current detection unit that detects the phase current flowing through the synchronous motor. The synchronous motor driving method, when the synchronous motor stops, acquires a first peak-to-peak value representing the difference between the maximum and minimum values ​​of the phase current detected by the current detection unit, and a second peak-to-peak value representing the difference between the maximum and minimum values ​​of the quadrature components of the phase current; calculates a first magnetic pole position based on the first peak-to-peak value and the second peak-to-peak value; and calculates the initial magnetic pole position of the rotor of the synchronous motor based on the first magnetic pole position.

[0018] The effects of the invention

[0019] According to the present invention, regardless of whether the synchronous motor is an embedded magnet type synchronous motor or a surface magnet type synchronous motor, the initial magnetic pole position of the rotor of the synchronous motor can be calculated with high accuracy during the synchronous motor stop (in the process of stopping). Attached Figure Description

[0020] Figure 1 This is a structural diagram of the drive device according to the first embodiment.

[0021] Figure 2 This is a detailed structural diagram of the voltage pulse generation unit in the first embodiment.

[0022] Figure 3 This is a diagram showing the relationship between the phase command, voltage command, and current flowing through the synchronous motor in the first embodiment.

[0023] Figure 4 This is a diagram illustrating the effects of magnetic saturation.

[0024] Figure 5 This is a detailed structural diagram of the magnetic pole position calculation unit in the first embodiment.

[0025] Figure 6 This is a structural diagram showing the main functions of the first magnetic pole position calculation unit.

[0026] Figure 7 This diagram illustrates the principle behind improved accuracy in calculating the initial magnetic pole position.

[0027] Figure 8 This is a structural diagram representing the main functions of the polarity discriminator.

[0028] Figure 9 This is a detailed structural diagram of the magnetic pole position calculation unit in the second embodiment.

[0029] Figure 10 This is a structural diagram showing the main functions of the third magnetic pole position calculation unit.

[0030] Figure 11 This is a structural diagram showing the main functions of the fourth magnetic pole position calculation unit.

[0031] Figure 12 This is a structural diagram of the drive device according to the third embodiment.

[0032] Figure 13 This is a detailed structural diagram of the voltage pulse generation unit in the third embodiment.

[0033] Figure 14 This is a diagram showing the relationship between the phase command, voltage command, and the current flowing in the synchronous motor in the third embodiment.

[0034] Figure 15 This is a structural diagram of the drive device according to the fourth embodiment. Detailed Implementation

[0035] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following description and drawings are examples for illustrating the present invention, and appropriate omissions and simplifications have been made for clarity. The present invention can also be implemented in various other ways. Unless otherwise specified, each constituent element may be single or multiple.

[0036] [First Implementation Method]

[0037] Figure 1 This is a structural diagram of the drive device 100A according to the first embodiment. The drive device 100A includes a power converter 300, a voltage pulse generation unit 400A, a current detection unit 500, and a magnetic pole position calculation unit 600A, and drives the synchronous motor 200.

[0038] The synchronous motor 200 is a permanent magnet type synchronous motor, constructed by using permanent magnets (strong magnetic materials) in the rotor and armature windings in the stator. Furthermore, in this embodiment, a position sensor for detecting the magnetic pole position of the synchronous motor 200 is omitted; instead, the magnetic pole position is calculated. By calculating the magnetic pole position, miniaturization, cost reduction, and improved reliability of the synchronous motor 200 can be achieved.

[0039] When the synchronous motor 200 is driven, the voltage pulse generation unit 400A responds to the input torque command T* and generates voltage commands Vu*, Vv*, and Vw* to sequentially apply positive and negative voltages to the u-phase, v-phase, and w-phase of the synchronous motor 200, and outputs them to the power converter 300. The voltage pulse generation unit 400A generates voltage commands Vu*, Vv*, and Vw* based on the magnetic pole position calculated by the magnetic pole position calculation unit 600A. Furthermore, when calculating the initial magnetic pole position of the synchronous motor 200, the voltage pulse generation unit 400A generates a predetermined phase command θ* and outputs it to the magnetic pole position calculation unit 600A.

[0040] The power converter 300, for example, is an inverter. When driving the synchronous motor 200, it performs pulse width modulation (PWM) on the voltage commands Vu*, Vv*, and Vw* from the voltage pulse generation unit 400A to control the on / off state of the semiconductor switching elements of the power converter. As a result, voltages Vu, Vv, and Vw are applied to the synchronous motor 200, driving the synchronous motor 200.

[0041] The current detection unit 500 consists of current sensors 500u, 500v, and 500w that detect the three-phase current flowing through the synchronous motor 200. The current sensors 500u, 500v, and 500w are respectively disposed on each phase of the synchronous motor 200. The current detection unit 500 detects the three-phase currents Iu, Iv, and Iw and outputs them to the magnetic pole position calculation unit 600A. Here, an example is shown where the current sensors 500u, 500v, and 500w are respectively disposed on the three phases of the synchronous motor 200, but it is also possible to use only two phases (e.g., phase u and phase v) when the sum of the three-phase AC currents is zero. Alternatively, a structure can be adopted to obtain the three-phase current of the synchronous motor 200 based on the current flowing through the DC bus (not shown) on the input side of the power converter 300. Using these structures reduces the number of current sensors and achieves cost reduction.

[0042] The magnetic pole position calculation unit 600A calculates the magnetic pole position corresponding to the rotor position of the synchronous motor 200 based on the three-phase currents Iu, Iv, and Iw detected by the current detection unit 500. Furthermore, during a stop (stop period) of the synchronous motor 200, the initial magnetic pole position θest of the rotor of the synchronous motor 200 is calculated based on the three-phase currents Iu, Iv, and Iw detected by the current detection unit 500 and the phase command θ* output from the voltage pulse generation unit 400A. Details of the magnetic pole position calculation unit 600A during a stop of the synchronous motor 200 will be described later.

[0043] Figure 2 This is a detailed structural diagram of the voltage pulse generation unit 400A according to the first embodiment. Furthermore, this structural diagram shows the structure when the initial magnetic pole position θest is calculated while the synchronous motor 200 is stopped. The structure when voltage commands Vu*, Vv*, and Vw* are generated according to the torque command T* during the driving of the synchronous motor 200 is known, therefore, its description is omitted in this embodiment.

[0044] The voltage pulse generation unit 400A includes a voltage command generation unit 410, a phase switcher 420, and a command coordinate transformation unit 430.

[0045] In the voltage command generation unit 410, the d-axis voltage command Vd* and the q-axis voltage command Vq* are output. In this embodiment, the following is described: Figure 3 The d-axis voltage command Vd*, which alternates between positive and negative values, is shown in (B), while the q-axis voltage command Vq* is zero.

[0046] Phase switcher 420 generates phase command θ* for converting (transforming) the d-axis voltage command Vd* and q-axis voltage command Vq* generated by voltage command generation unit 410 into three-phase voltage commands. Phase switcher 420 outputs 0 degrees (0 radians), 120 degrees (2 / 3π radians), and 240 degrees (4 / 3π radians) as phase command θ* in sequence.

[0047] The command coordinate transformation unit 430 takes the d-axis voltage command Vd* and q-axis voltage command Vq* generated by the voltage command generation unit 410, and the phase command θ* output from the phase switching unit 420 as inputs, and transforms their coordinates into three-phase voltage commands Vu*, Vv*, and Vw*. The coordinate transformation is performed according to the following equations (1), (2), and (3).

[0048] Vu*=Vd*×cos(θ*)-Vq*×sin(θ*)……(1)

[0049] Vv*=Vd*×cos(θ*-2π / 3)-Vq*×sin(θ*-2π / 3)……(2)

[0050] Vw*=Vd*×cos(θ*-4π / 3)-Vq*×sin(θ*-4π / 3)……(3)

[0051] Figure 3 This is a diagram showing the relationship between the phase command θ*, the voltage command, and the current flowing through the synchronous motor 200 in the first embodiment. Figure 3 (A) represents the phase command θ* output by the phase switcher 420. Figure 3 (B) represents the d-axis voltage command Vd* generated by the voltage command generation unit 410. Furthermore, as mentioned above, the q-axis voltage command Vq* is zero. Figure 3 (C)~ Figure 3 (E) represents the three-phase voltage commands Vu*, Vv*, and Vw* output by the command coordinate transformation unit 430, respectively. Figure 3 (F) Figure 3 (H) represents the three-phase currents Iu, Iv, and Iw detected by the current detection unit 500 and input to the magnetic pole position calculation unit 600A, respectively.

[0052] like Figure 3 As shown in (A), the phase switcher 420 outputs phase commands θ* in the order of 0 degrees (0 radians), 120 degrees (2 / 3π radians), and 240 degrees (4 / 3π radians). The three-phase voltage commands Vu*, Vv*, and Vw*, which are output by the command coordinate transformation unit 430, are as follows: Figure 3 (C)~ Figure 3 As shown in (E), the alternating positive and negative pulse voltage is applied to phase u when the phase command θ* is 0 degrees, to phase v when the phase command θ* is 120 degrees, and to phase w when the phase command θ* is 240 degrees. Thus, as... Figure 3 (F) Figure 3 As shown in (H), the three-phase currents Iu, Iv, and Iw flow through the synchronous motor 200.

[0053] Figure 5 This is a detailed structural diagram of the magnetic pole position calculation unit 600A according to the first embodiment.

[0054] The magnetic pole position calculation unit 600A includes a first peak-to-peak detector 610, a second peak-to-peak detector 620, an orthogonal component detector 630, a first magnetic pole position calculation unit 640, a polarity discriminator 650, and a second magnetic pole position calculation unit 660.

[0055] The first peak-to-peak detector 610 takes the current values ​​Iu, Iv, and Iw detected by the current detection unit 500 as input and detects the peak-to-peak values ​​Iupp, Ivpp, and Iwpp, which represent the difference between the maximum and minimum values ​​of the current in each phase.

[0056] The peak-to-peak value of the u-phase current, Iupp, is at Figure 3 In (F), Iu+ is the difference between the maximum value of the u-phase current Iu+ when the phase command θ* is 0 degrees and a positive voltage is applied to the u-phase, and the minimum value of the u-phase current Iu- when the phase command θ* is 0 degrees and a negative voltage is applied to the u-phase.

[0057] The peak-to-peak value of the phase v current, Ivpp, is at Figure 3 In (G), Iv+ is the difference between the maximum value of the phase current Iv+ when the phase command θ* is 120 degrees and a positive voltage is applied to phase v, and the minimum value of the phase current Iv- when the phase command θ* is 120 degrees and a negative voltage is applied to phase v.

[0058] The peak-to-peak value of the phase current Iwpp is at Figure 3 In (H), Iw+ is the difference between the maximum value of the phase current Iw+ when the phase command θ* is 240 degrees and a positive voltage is applied to phase w, and the minimum value of the phase current Iw- when the phase command θ* is 240 degrees and a negative voltage is applied to phase w.

[0059] like Figure 3 (F) Figure 3 As shown in (H), Iupp, Ivpp, and Iwpp are the peak-to-peak values ​​of the currents in each phase. Generally, permanent magnet synchronous motors used in the drive of electric vehicles such as electric cars have salient polarity (rotor position dependence of inductance), and the inductance varies depending on the rotor position. Therefore, the peak-to-peak values ​​of the currents Iupp, Ivpp, and Iwpp obtained when the synchronous motor 200 stops also vary depending on the initial magnetic pole position θest. Furthermore, it is known that the change in current based on salient polarity (change in inductance) occurs with a period of 1 / 2 times the rotor position. Using these factors, the initial magnetic pole position θest can be calculated from Iupp, Ivpp, and Iwpp.

[0060] However, depending on the initial magnetic pole position, the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of each phase current include not only variations in current based on salient polarity, but sometimes also variations in current based on magnetic saturation. For more information on this, please refer to the following... Figure 4 Please provide an explanation.

[0061] For example, such as Figure 4 As shown, in the synchronous motor 200, with the initial magnetic pole position at 30 degrees, the N pole of the rotor (magnet) is located near the +u and -w phases. Assuming this state, the voltage pulse generator 400A outputs... Figure 3 (C)~ Figure 3The voltage commands Vu*, Vv*, and Vw* shown in (E) are applied from the power converter 300 to the synchronous motor 200 with voltages Vu, Vv, and Vw corresponding to these voltage commands. At this time, during the period when a positive voltage is applied to the u-phase in the u-phase application interval (where the phase command θ* is 0 degrees) and during the period when a negative voltage is applied to the w-phase in the w-phase application interval (where the phase command θ* is 240 degrees), the magnetic flux of the magnet is superimposed on the magnetic flux generated by the current. Therefore, the magnetic flux density in the stator of the synchronous motor 200 is high, resulting in magnetic saturation and a decrease in inductance. Therefore, in Figure 3 Iu+ and in (F) Figure 3 In (H), Iw-, there are cases where the current change is larger than that in the case where magnetic saturation does not occur.

[0062] As explained above, depending on the initial magnetic flux position, the peak-to-peak values ​​of the phase currents Iupp, Ivpp, and Iwpp sometimes exhibit changes not only due to salient polarity but also due to magnetic saturation. This is a significant reason for the increased calculation error of the initial magnetic pole position θest in the magnetic pole position estimation unit 600A.

[0063] Furthermore, in electric vehicles, the permanent magnet type synchronous motors used in braking systems and electric power steering systems are often surface magnet type synchronous motors without salient polarity. Because surface magnet type synchronous motors lack salient polarity, the initial magnetic pole position cannot be directly calculated in the magnetic pole position calculation unit 600A using the current changes caused by salient polarity as described above. Assuming the synchronous motor 200 is a surface magnet type synchronous motor, the calculation error increases when calculating the initial magnetic pole position θest based on the changes in the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of each phase current.

[0064] Therefore, in this embodiment, an orthogonal component detector 630 and a second peak-to-peak detector 620 are provided in the magnetic pole position estimation unit 600A. Then, the first magnetic pole position calculation unit 640 calculates the first magnetic pole position θest1 based on the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of each phase current output from the first peak-to-peak detector 610 and the peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp of the orthogonal components of each phase current output from the second peak-to-peak detector 620, as described below. Based on the first magnetic pole position θest1 obtained in this way, the initial magnetic pole position θest is estimated.

[0065] The quadrature component detector 630 takes the current values ​​Iu, Iv, Iw, and phase command θ* detected by the current detection unit 500 as inputs, and detects the quadrature components for each phase current based on them. Here, the orthogonal two-axis components Iγ and Iδ are calculated based on the current values ​​Iu, Iv, Iw and phase command θ* according to the following equations (4) and (5), thereby obtaining the quadrature components for each phase current.

[0066] Iγ=2 / 3×{Iu×cos(θ*)+Iv×cos(θ*-2π / 3)+Iw×cos(θ*-4π / 3)}......(4)

[0067] Iδ=-2 / 3×{Iu×sin(θ*)+Iv×sin(θ*-2π / 3)+Iw×sin(θ*-4π / 3)}......(5)

[0068] After the orthogonal component detector 630 calculates the orthogonal biaxial components Iγ and Iδ, it outputs Iδ to the second peak detector 620.

[0069] The second peak-to-peak detector 620 takes the quadrature component Iδ of the phase current obtained by the quadrature component detector 630 as input and detects the peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp, which represent the difference between the maximum and minimum values ​​of the quadrature component Iδ.

[0070] Peak-to-peak value Iδupp is the difference between the maximum and minimum values ​​of the quadrature component Iδ when the phase command θ* is 0 degrees. This is in Figure 3 In (J), the difference between the peak value Iδu+ of Iδ when the phase command θ* is 0 degrees and a positive voltage is applied to phase u, and the peak value Iδu- of Iδ when the phase command θ* is 0 degrees and a negative voltage is applied to phase u.

[0071] Peak-to-peak value Iδvpp is the difference between the maximum and minimum values ​​of the quadrature component Iδ when the phase command θ* is 120 degrees. This is in Figure 3 In (J), the difference between the peak value Iδv+ of Iδ when the phase command θ* is 120 degrees and a positive voltage is applied to phase v, and the peak value Iδv- of Iδ when the phase command θ* is 120 degrees and a negative voltage is applied to phase v.

[0072] Peak-to-peak value Iδwpp is the difference between the maximum and minimum values ​​of the quadrature component Iδ when the phase command θ* is 240 degrees. This is in Figure 3 In (J), the difference between the peak value Iδw+ of Iδ when the phase command θ* is 240 degrees and a positive voltage is applied to phase w, and the peak value Iδw- of Iδ when the phase command θ* is 240 degrees and a negative voltage is applied to phase w.

[0073] The first magnetic pole position calculation unit 640 takes the output of the first peak-to-peak detector 610, namely the peak-to-peak values ​​of each phase current Iupp, Ivpp, Iwpp, and the output of the second peak-to-peak detector 620, namely the peak-to-peak values ​​of the quadrature component Iδ, Iδupp, Iδvpp, Iδwpp, as inputs, and calculates the first magnetic pole position θest1 based on them.

[0074] The peak-to-peak values ​​of the orthogonal components Iδ, Iδupp, Iδvpp, and Iδwpp, are electrically orthogonal to the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of each phase current. Therefore, even when the inductance of the synchronous motor 200 decreases due to the aforementioned magnetic saturation, and the corresponding peak-to-peak values ​​Iupp, Ivpp, and Iwpp of the phase current increase, the peak-to-peak values ​​Iδ, Iδupp, Iδvpp, and Iδwpp of Iδ decrease because magnetic saturation does not occur in their orthogonal components Iδ. Conversely, when the peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp of Iδ increase due to magnetic saturation, the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of the phase current decrease. Thus, the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of the phase current have a relative characteristic to the peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp of the orthogonal components Iδ.

[0075] In this embodiment, the changes in the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of the phase current caused by magnetic saturation are offset by performing orthogonal biaxial component averaging processing (described later) in the first magnetic pole position calculation unit 640 using the aforementioned characteristics. As a result, it is possible to extract only the current changes caused by salient polarity.

[0076] Furthermore, when the synchronous motor 200 is a surface magnet type synchronous motor, since the synchronous motor 200 does not have salient polarity, the orthogonal component Iδ is originally fixed, and the peak-to-peak values ​​of Iδ, Iδupp, Iδvpp, and Iδwpp, are all 0. However, when magnetic saturation corresponding to the initial magnetic pole position occurs in the synchronous motor 200 as described above, the magnetic flux direction of the permanent magnet and the inductance in the direction orthogonal to it change, thus generating peak-to-peak values ​​of the orthogonal component Iδ, Iδupp, Iδvpp, and Iδwpp. In this embodiment, using these peak-to-peak values ​​of the orthogonal component Iδ, Iδupp, Iδvpp, and Iδwpp, the initial magnetic pole position θest can be calculated even when the synchronous motor 200 is a surface magnet type synchronous motor.

[0077] Figure 6 This is a structural diagram illustrating the main functions of the first magnetic pole position calculation unit 640. The first magnetic pole position calculation unit 640 includes a first coordinate transformation unit 641, a second coordinate transformation unit 642, an orthogonal two-axis component averaging processing unit 643, and a position calculation unit 644.

[0078] The first coordinate transformation unit 641 takes the output of the first peak-to-peak detector 610, i.e., the peak-to-peak values ​​of each phase current Iupp, Ivpp, and Iwpp, as input, and transforms their coordinate system to the αβ coordinate system to output Iαpp and Iβpp. Here, the transformation to the αβ coordinate system is performed according to the following equations (6) and (7).

[0079] Iαpp=2 / 3×{Iupp-1 / 2×Ivpp-1 / 2×1wpp}……(6)

[0080] Iβpp=2 / 3×{(√(3) / 2)×(Ivpp-Iwpp)}......(7)

[0081] The second coordinate transformation unit 642 takes the peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp of the orthogonal component Iδ as input from the output of the second peak-to-peak detector 620, and transforms their coordinate system to the αβ coordinate system, outputting Iδαpp and Iδβpp. Here, the transformation to the αβ coordinate system is performed according to the following equations (8) and (9).

[0082] Iδαpp=2 / 3×{Iδupp-1 / 2×Iδvpp-1 / 2×1δwpp}……(8)

[0083] Iδβpp=2 / 3×{(√(3) / 2)×(Iδvpp-Iδwpp)}......(9)

[0084] The orthogonal two-axis component averaging processing unit 643 takes the outputs of the first coordinate transformation unit 641, namely Iαpp and Iβpp, and the outputs of the second coordinate transformation unit 642, namely Iδαpp and Iδβpp, as inputs, and performs orthogonal two-axis component averaging processing (i.e., orthogonal two-axis component averaging processing) on ​​them, thereby outputting Pα and Pβ.

[0085] The orthogonal biaxial component averaging processing unit 643 calculates Pα and Pβ according to the following formulas (10) and (11). Pα is obtained by dividing the sum of Iαpp and Iδβpp by 2, and Pβ is obtained by dividing the difference between Iδαpp and Iβpp by 2.

[0086] Pα=1 / 2×(Iαpp+Iδβpp)……(10)

[0087] Pβ=1 / 2×(Iδαpp-Iβpp)……(11)

[0088] Here, embedded magnet type synchronous motors and surface magnet type synchronous motors are taken as examples respectively, with reference to Figure 7 The principle of improving the accuracy of initial magnetic pole position calculation by averaging orthogonal biaxial components is explained below.

[0089] The outputs of the first coordinate transformation unit 641, namely Iαpp and Iβpp, the outputs of the second coordinate transformation unit 642, namely Iδαpp and Iδβpp, and the outputs of the orthogonal two-axis component averaging processing unit 643, namely Pα and Pβ, change in a certain relationship with each other according to the initial magnetic pole position. Figure 7 It is a diagram depicting the trajectory of the changes for various combinations of initial magnetic pole positions. Figure 7 In the diagram, the trajectories of Iαpp and Iβpp are plotted with Iαpp on the horizontal axis and -Iβpp on the vertical axis. Similarly, the trajectories of Iδαpp and Iδβpp are plotted with Iδβpp on the horizontal axis and Iδαpp on the vertical axis. Additionally, the trajectories of Pα and Pβ are plotted with Pα on the horizontal axis and Pβ on the vertical axis. These trajectories rotate with respect to the initial magnetic pole position at a period of 1 / 2. Therefore, Figure 7 In the example, a point on the vertical axis that serves as the boundary between the first and second quadrants corresponds to an initial magnetic pole position of 45 degrees or 225 degrees.

[0090] Here, the initial magnetic pole position of the synchronous motor 200 is equivalent to setting the magnetic pole position of the synchronous motor 200 to 1. Figure 7 The horizontal and vertical components of each trajectory shown are input into the arctangent function to obtain their values. That is, the closer these trajectories are to circles, the more accurately the initial magnetic pole positions can be determined.

[0091] Figure 7 (a) shows an example of the trajectory of the above combinations when the synchronous motor 200 is an embedded magnet type synchronous motor. As mentioned above, when magnetic saturation occurs in the synchronous motor 200, the inductance decreases, and therefore the current in each phase increases. As a result, as Figure 7 As shown in (a), the trajectories of Iαpp and Iβpp are not circular, but rather depict bulging shapes near the initial magnetic pole positions of 30°, 90°, 150°, 210°, 270°, and 330°. On the other hand, because no magnetic saturation occurs in the direction orthogonal to the phase currents, the trajectories of Iδαpp and Iδβpp are smaller than those of Iαpp and Iβpp.

[0092] Using this situation, by finding the trajectories of Pα and Pβ, which are equivalent to the trajectories of Iαpp and Iβpp, and the trajectories of Iδαpp and Iδβpp, such as... Figure 7 As shown in (a), a circular trajectory can be obtained. That is, in a synchronous motor with embedded magnets, even if magnetic saturation occurs, causing the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of each phase current to increase, Pα and Pβ, which exclude the effects of magnetic saturation, can still be obtained. Therefore, it can be seen that the initial magnetic pole position can be determined with high accuracy based on Pα and Pβ.

[0093] Figure 7(b) represents an example of the trajectories of the above combinations when the synchronous motor 200 is a surface magnet type synchronous motor. In the case of a surface magnet type synchronous motor without salient polarity, Iδαpp and Iδβpp are originally zero, but when the inductance changes due to magnetic saturation, Iδαpp and Iδβpp are generated. The trajectories of Iδαpp and Iδβpp at this time are... Figure 7 The case of the embedded magnet type synchronous motor shown in (a) is similar, with characteristics opposite to the trajectories of Iδαpp and Iδβpp.

[0094] Using this, by finding the trajectories of Pα and Pβ, which are equivalent to the trajectories of Iαpp and Iβpp, and the trajectories of Iδαpp and Iδβpp, it is possible to... Figure 7 As shown in (b), a circular trajectory is obtained. Thus, it can be seen that even when the synchronous motor 200 does not have salient polarity, or has very small salient polarity, the initial magnetic pole position can be determined with high accuracy based on Pα and Pβ.

[0095] As explained above, in this embodiment, the orthogonal two-axis component averaging processing unit 643 of the first magnetic pole position calculation unit 640 calculates Pα and Pβ, excluding the influence of magnetic saturation. In the position calculation unit 644, these are used to calculate the first magnetic pole position θest1. Therefore, regardless of whether the synchronous motor 200 is an embedded magnet type synchronous motor or a surface magnet type synchronous motor, the accuracy of the initial magnetic pole position calculation can be improved.

[0096] The position calculation unit 644 takes the outputs of the orthogonal two-axis component averaging processing unit 643, namely Pα and Pβ, as inputs and calculates the first magnetic pole position θest1 based on them. The first magnetic pole position θest1 is obtained according to the following formula (12).

[0097] θest1=1 / 2×{arctan(Pβ / Pα)}……(12)

[0098] Typically, it is known that the change in inductance caused by the salient polarity in the synchronous motor 200 occurs with a period of 1 / 2 times the rotation angle. That is, when using a calculation method utilizing salient polarity, calculations can only be performed within the range of 0 to 180 degrees for the initial magnetic pole position, and it is impossible to determine whether the rotor magnet has a north (N) or south (S) pole. Therefore, the magnetic pole position calculation unit 600A of this embodiment, as... Figure 5 As shown, a polarity discriminator 650 is included to determine the polarity of the rotor's magnets.

[0099] Figure 8This is a structural diagram illustrating the main functions of the polarity discriminator 650. In this embodiment, the polarity discriminator 650 includes a peak detector 651, an absolute value calculation unit 652, a subtraction unit 653, a coordinate transformation unit 654, and a polarity calculation unit 655.

[0100] The peak detector 651 takes the phase currents Iu, Iv, and Iw detected by the current detection unit 500 as input and detects the peak values ​​Iu+, Iu-, Iv+, Iv-, Iw+, and Iw- of each phase current.

[0101] Peak current Iu+ is Figure 3 The maximum value of the phase current in phase u when the phase command θ* is 0 degrees and a positive voltage is applied to phase u in (F). The peak current Iu- is Figure 3 The minimum value of the current in phase u when the phase command θ* is 0 degrees and a negative voltage is applied to phase u in (F).

[0102] Peak current Iv+ is Figure 3 The maximum value of the phase current in phase v when the phase command θ* is 120 degrees and a positive voltage is applied to phase v in (G). The peak current Iv- is Figure 3 The minimum value of the phase current when the phase command θ* is 120 degrees and a negative voltage is applied to phase v in (G).

[0103] Peak current Iw+ is Figure 3 The maximum value of the phase current in phase w when the phase command θ* is 240 degrees and a positive voltage is applied to phase w. The peak current Iw- is... Figure 3 The minimum value of phase current when phase command θ* is 240 degrees and a negative voltage is applied to phase w in (H).

[0104] The absolute value calculation unit 652 takes the peak current values ​​Iu+, Iu-, Iv+, Iv-, Iw+, and Iw- of each phase as inputs and calculates their respective absolute values.

[0105] The subtraction unit 653 calculates the difference in absolute values ​​of the peak current of each phase according to the following formulas (13), (14), and (15), and outputs ΔIu, ΔIv, and ΔIw.

[0106] ΔIu=|Iu+|-|Iu-|……(13)

[0107] ΔIv=|Iv+|-|Iw-|……(14)

[0108] ΔIw=|Iw+|-|Iv-|……(15)

[0109] ΔIu, ΔIv, and ΔIw are the absolute values ​​of the current values ​​when a positive voltage is applied and the current values ​​when a negative voltage is applied, and therefore represent the degree of magnetic saturation of the synchronous motor 200.

[0110] The coordinate transformation unit 654 transforms the absolute differences of the current peak values ​​of each phase, namely ΔIu, ΔIv, and ΔIw, using the following equations (16) and (17) to output ΔPα and ΔPβ.

[0111] ΔPα=2 / 3×{ΔIu-1 / 2×ΔIv-1 / 2×ΔIw}……(16)

[0112] ΔPβ=2 / 3×{(√(3) / 2)×(ΔIv-ΔIw)}……(17)

[0113] The polarity calculation unit 655 takes ΔPα and ΔPβ as inputs and determines whether the polarity of the magnet is N pole or S pole based on the second magnetic pole position θest2 obtained by the following formula (18).

[0114] θest2=arctan{ΔPβ / ΔPα}……(18)

[0115] Here, ΔPα and ΔPβ are values ​​obtained from the differences in the absolute values ​​of the peak current values ​​Iu+, Iu-, Iv+, Iv-, Iw+, and Iw- of each phase, namely ΔIu, ΔIv, and ΔIw. When the synchronous motor 200 experiences magnetic saturation, the absolute value of the peak current value in the saturation direction increases. Therefore, the differences in the absolute values ​​of the peak current values ​​of each phase, ΔIu, ΔIv, and ΔIw, represent the degree of magnetic saturation.

[0116] The degree of magnetic saturation does not necessarily appear in a sinusoidal pattern. Therefore, although the accuracy is not high, the magnetic pole position (including the polarity of the rotor magnets) can be calculated within a range of 0 to 360 degrees for either embedded magnet synchronous motors or surface magnet synchronous motors. In the polarity discriminator 650, this is used to determine the polarity of the second magnetic pole position θest2 obtained based on the degree of magnetic saturation, and the determination result is output as the polarity NS. For example, it is determined to be the N pole when θest2 is within a specified range, and the S pole when it is outside the specified range. Here, the specified range is, for example, the range of θest2 from 0 to 180 degrees. Specifically, it is determined to be the N pole when θest2 is between 0 and 180 degrees, and the S pole when θest2 is between 180 and 360 degrees.

[0117] Return to Figure 5 As explained, the second magnetic pole position calculation unit 660 calculates the rotor position of the synchronous motor 200 based on the first magnetic pole position θest1 calculated by the first magnetic pole position calculation unit 640 and the polarity NS determined by the second magnetic pole position θest2 calculated by the polarity discriminator 650.

[0118] The first magnetic pole position θest1 can only be obtained within the range of 0 to 180 degrees. However, when using the second magnetic pole position calculation unit 660, the initial magnetic pole position θest is calculated using the polarity NS, which is the determination result of the polarity discriminator 650. Specifically, if the polarity discriminator 650 determines that the polarity NS is the N pole, the first magnetic pole position θest1 is directly output as the initial magnetic pole position θest. On the other hand, if the polarity discriminator 650 determines that the polarity NS is the S pole, the value obtained by adding 180 degrees to the first magnetic pole position θest1 is output as the initial magnetic pole position θest.

[0119] According to the magnetic pole position calculation unit 600A of this embodiment, when the synchronous motor 200 is stopped, the peak-to-peak value of the current in each phase and the peak-to-peak value of the quadrature component of the current in each phase are detected when positive and negative voltages are sequentially applied to each phase of the synchronous motor 200 by the voltage pulse generation unit 400A. Furthermore, using the detected peak-to-peak values ​​of the current in each phase and the peak-to-peak values ​​of the quadrature component of the current in each phase, current changes caused by magnetic saturation are eliminated, and current changes caused by salient polarity are obtained. In addition, even when the synchronous motor 200 is a surface magnet type synchronous motor, the current change is obtained by utilizing the quadrature component of the phase current generated by the inductance change caused by magnetic saturation. Therefore, regardless of whether the synchronous motor 200 is an embedded magnet type or a surface magnet type, the initial magnetic pole position of the rotor can be calculated with good accuracy. Therefore, this embodiment has versatility applicable to both embedded magnet type and surface magnet type synchronous motors, and the initial magnetic pole position can be calculated with high accuracy. Therefore, sensorless control of the synchronous motor 200 can also be implemented with high accuracy. For example, when the synchronous motor 200 is used as a drive motor in an electric vehicle, the control performance of the drive motor can be improved, providing passengers with a comfortable ride. Furthermore, when the synchronous motor 200 is used in auxiliary devices such as electric power steering and electric braking systems in an electric vehicle, the control performance of these auxiliary devices can be improved, enhancing drivability.

[0120] [Second Implementation]

[0121] Figure 9 This is a detailed structural diagram of the magnetic pole position calculation unit 600B according to the second embodiment. The same reference numerals are used for parts identical to those in the magnetic pole position calculation unit 600A of the first embodiment, and their descriptions are omitted. Furthermore, Figure 1 The diagram shows the structure of the drive unit 100A for the synchronous motor 200. Figure 2 Detailed structural diagram of the voltage pulse generation unit 400A shown. Figure 3 The graph showing the relationship between the three-phase voltage command and the three-phase current is the same in this embodiment.

[0122] In the first embodiment, the polarity NS determination performed by the second magnetic pole position calculation unit 660 only utilizes the second magnetic pole position θest2 obtained from the difference in absolute values ​​of the current peak values ​​of each phase ΔIu, ΔIv, and ΔIw. However, in this embodiment, the polarity NS is determined based on the first magnetic pole position θest1 and the second magnetic pole position θest2.

[0123] In this embodiment, such as Figure 9 As shown, the magnetic pole position calculation unit 600B replaces the polarity discriminator 650 and the second magnetic pole position calculation unit 660 with a third magnetic pole position calculation unit 670 and a fourth magnetic pole position calculation unit 680. The third magnetic pole position calculation unit 670 calculates the second magnetic pole position θest2 based on the phase currents Iu, Iv, and Iw detected by the current detection unit 500. The second magnetic pole position θest2 is input from the third magnetic pole position calculation unit 670 to the fourth magnetic pole position calculation unit 680, and the first magnetic pole position θest1 is input from the first magnetic pole position calculation unit 640 to the fourth magnetic pole position calculation unit 680. The fourth magnetic pole position calculation unit 680 calculates the initial magnetic pole position θest based on these magnetic pole positions.

[0124] Figure 10 This is a structural diagram illustrating the main functions of the third magnetic pole position calculation unit 670. In this embodiment, the third magnetic pole position calculation unit 670 includes a peak detector 671, an absolute value calculation unit 672, a subtraction unit 673, a coordinate transformation unit 674, and a position calculation unit 675.

[0125] The peak detector 671, absolute value operation unit 672, subtraction unit 673, and coordinate transformation unit 674 perform the same processing as the peak detection unit 651, absolute value operation unit 652, subtraction unit 653, and coordinate transformation unit 654 of the polarity discriminator 650 in the first embodiment.

[0126] The position calculation unit 675 takes ΔPα and ΔPβ output from the coordinate transformation 674 as input and calculates the second magnetic pole position θest2 according to the above formula (18). The third magnetic pole position calculation unit 670 outputs the second magnetic pole position θest2 calculated by the position calculation unit 675 to the fourth magnetic pole position calculation unit 680.

[0127] Figure 11 This is a structural diagram illustrating the main functions of the fourth magnetic pole position calculation unit 680. The fourth magnetic pole position calculation unit 680 includes a subtraction processing unit 681, an absolute value processing unit 682, a threshold judgment unit 683, and an initial magnetic pole position calculation unit 684.

[0128] The subtraction processing unit 681 calculates the difference between the first magnetic pole position θest1 and the second magnetic pole position θest2. The absolute value processing unit 682 calculates the absolute value of the difference between the first magnetic pole position θest1 and the second magnetic pole position θest2. The threshold judgment unit 683 determines the pole as S when the absolute value of the difference between the first magnetic pole position θest1 and the second magnetic pole position θest2 is within a specified range, and determines it as N when it is outside the specified range. Here, the specified range can be set to account for the error of the second magnetic pole position θest2, for example, the absolute value of the difference between the first magnetic pole position θest1 and the second magnetic pole position θest2 is in the range of 90 to 270 degrees.

[0129] When the threshold determination unit 683 determines that the first magnetic pole position is S, the initial magnetic pole position calculation unit 684 outputs the value obtained by adding 180 degrees to the first magnetic pole position θest1 as the initial magnetic pole position θest. When the first magnetic pole position is N, the first magnetic pole position θest1 is output as the initial magnetic pole position θest.

[0130] Here, as described in the first embodiment, when polarity NS is determined solely based on the second magnetic pole position θest2, the accuracy of the second magnetic pole position θest2 is low, leading to the problem of misjudging polarity NS. For example, if the second magnetic pole position θest2 is between 0 and 180 degrees and is determined to be the N pole, or between 180 and 360 degrees and is determined to be the S pole, there is an error between the actual initial magnetic pole position and the second magnetic pole position θest2, resulting in misjudgment of polarity when the initial magnetic pole position θest2 is around 180 or 360 degrees.

[0131] On the other hand, as shown in this embodiment, by determining the polarity NS based on the first magnetic pole position θest1 and the second magnetic pole position θest2, the error of the second magnetic pole position θest2 can be taken into account, so the initial magnetic pole position θest of the rotor can be calculated without misjudging the polarity NS.

[0132] The polarity NS determination shown in this embodiment is able to Figure 3 The polarity is determined during the application of the voltage pulse shown, which minimizes the time required to calculate the initial magnetic pole position θest, making it suitable. Alternatively, the polarity can be determined using commonly known methods after the first magnetic pole position θest1 has been calculated.

[0133] [Third Implementation Method]

[0134] Figure 12This is a structural diagram of the drive device 100B according to the third embodiment. The drive device 100B of this embodiment is configured such that, while the synchronous motor 200 is stopped, the power converter 300 applies positive and negative pulse voltages sequentially to each phase of the synchronous motor 200 multiple times with mutually different pulse widths. Furthermore, for... Figure 1 The same parts of the structural diagrams of the drive device 100A of the first and second embodiments shown are given the same reference numerals, and their descriptions are omitted.

[0135] In the first and second embodiments, the phase switch 420 in the voltage pulse generation unit 400A generates a phase command θ* for converting the d-axis voltage command Vd* and q-axis voltage command Vq* generated by the voltage command generation unit 410 into three-phase voltage commands. Specifically, as the phase command θ* for calculating the initial magnetic pole position θest when the synchronous motor 200 stops, 0 degrees (0 radians), 120 degrees (2 / 3π radians), and 240 degrees (4 / 3π radians) are output sequentially. In contrast, in this embodiment, as Figure 12 As shown, the drive unit 100B is equipped with a voltage pulse generation unit 400B instead of a voltage pulse generation unit 400A. When the synchronous motor 200 is stopped, the voltage pulse generation unit 400B generates and outputs a phase command θ*, enabling the power converter 300 to apply pulse voltages to the synchronous motor 200 multiple times with mutually different pulse widths.

[0136] The phase command θ* output from the voltage pulse generation unit 400B is input to the magnetic pole position calculation unit 600A described in the first embodiment or the magnetic pole position calculation unit 600B described in the second embodiment. In this embodiment, either the magnetic pole position calculation unit 600A or 600B can be used to calculate the initial magnetic pole position θest.

[0137] Figure 13 This is a detailed structural diagram of the voltage pulse generation unit 400B according to the third embodiment. The voltage pulse generation unit 400B includes a voltage command generation unit 410, a phase switcher 420, a command coordinate transformation unit 430, and a pulse width and repetition number setting unit 440. The voltage command generation unit 410, the phase switcher 420, and the command coordinate transformation unit 430 have the same structures as those included in the voltage pulse generation unit 400A in the first embodiment.

[0138] In the drive device 100B of this embodiment, the magnetic pole position calculation units 600A and 600B can calculate the initial magnetic pole position θest by repeatedly executing a series of actions described in the first or second embodiment. In the voltage pulse generation unit 400B of this embodiment, the pulse width and repetition number setting unit 440 outputs the number of repetitions Nmax of the series of actions performed by the magnetic pole position calculation units 600A and 600B, and the pulse width Dn of the d-axis voltage command Vd* output by the voltage command generation unit 410 for the nth action. Here, n is a natural number greater than or equal to 1 and less than or equal to Nmax. The values ​​of Nmax and Dn can be preset in the pulse width and repetition number setting unit 440 or can be arbitrarily specified by the user.

[0139] Reference Figure 14 The operation of the drive device 100B in the third embodiment is explained. Figure 14 This is a diagram showing the relationship between the phase command θ*, the voltage command, and the current flowing through the synchronous motor 200 in the third embodiment. Figure 14 The example shown illustrates the phase command θ*, voltage command, and current when the number of repetitions Nmax output from the pulse width and repetition count setting unit 440 is 2. Additionally, Figure 14 (A) Figure 14 (J) indicates that with Figure 3 (A) Figure 3 The (J) contents are the same.

[0140] Figure 14 In this case, since Nmax = 2, the magnetic pole position calculation units 600A and 600B perform a series of operations for initial magnetic pole position calculation as described in the first or second embodiment twice. At this time, the pulse width and repetition number setting unit 440 sets the pulse width of the d-axis voltage command Vd* for the first operation (set as the first sequence) to D1. On the other hand, for the second operation (set as the second sequence), unlike the first sequence, the pulse width of the d-axis voltage command Vd* is set to D2.

[0141] In the voltage pulse generation unit 400B of this embodiment, the voltage command generation unit 410 is based on the pulse widths D1 and D2 output from the pulse width and repetition count setting unit 440, such as... Figure 14 As shown in (B), d-axis voltage commands Vd* corresponding to these pulse widths are generated in the first and second sequences, respectively. Thus, as... Figure 14 (C)~ Figure 14 As shown in (E), in the first sequence, three-phase voltage commands Vu*, Vv*, and Vw* with alternating positive and negative values ​​are output sequentially from the command coordinate transformation unit 430 with pulse width D1 and in the second sequence with pulse width D2.

[0142] In this embodiment, such as Figure 14 (F) Figure 14 As shown in (H), in the first and second sequences, the three-phase currents Iu, Iv, and Iw, corresponding to the respectively set pulse widths D1 and D2, flow through the synchronous motor 200. Additionally, as... Figure 14 (I)~ Figure 14 As shown in (J), in the first and second sequences, the orthogonal components Iγ and Iδ of the three-phase currents corresponding to the pulse widths D1 and D2 respectively flow through the synchronous motor 200.

[0143] As described in the first embodiment, in the case of an embedded magnet-type synchronous motor, the peak-to-peak values ​​Iupp, Ivpp, and Iwpp of each phase current include not only current changes caused by salient polarity but also current changes caused by magnetic saturation. Therefore, this is a significant cause of error in the initial magnetic pole position. In the first and second embodiments, the calculation accuracy of the initial magnetic pole position θest is improved by utilizing the peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp of the orthogonal components Iδ to address this significant cause of error. However, even with this method of calculating the initial magnetic pole position θest using orthogonal components relative to the phase currents, there are still cases where the influence of magnetic saturation cannot be completely eliminated due to factors such as the structure of the synchronous motor 200 and deviations in the semiconductor elements constituting the power converter 300.

[0144] Therefore, in the drive device 100B of this embodiment, by providing a pulse width and repetition number setting unit 440 in the voltage pulse generation unit 400B, when the synchronous motor 200 is stopped, the power converter 300 sequentially applies positive and negative pulse voltages with mutually different pulse widths D1 and D2 to each phase of the synchronous motor 200. Using the magnetic pole position estimation units 600A and 600B, the initial magnetic pole position θest is estimated based on the peak values ​​Iu+, Iu-, Iv+, Iv-, Iw+, and Iw- of each phase current detected respectively when these pulse voltages are applied.

[0145] Specifically, the magnetic pole position estimation unit 600A or 600B, for a pulse voltage applied with pulse width D1 in the first sequence, calculates the first magnetic pole position θest1 by the first magnetic pole position calculation unit 640 based on the peak-to-peak values ​​Iupp, Ivpp, Iwpp of the phase currents Iu, Iv, and Iw obtained by the first peak-to-peak detector 610, and the peak-to-peak values ​​Iδupp, Iδvpp, Iδwpp of the orthogonal components Iδ of each phase current obtained by the second peak-to-peak detector 620. Furthermore, for a pulse voltage applied with pulse width D2 in the second sequence, the second magnetic pole position θest2 is calculated according to the above formula (18), and the polarity of the rotor magnet is determined by the polarity discriminator 650 or the fourth magnetic pole position calculation unit 680 as either N or S pole. Based on the first magnetic pole position θest1 obtained in this way and the polarity determination result, the initial magnetic pole position θest can be estimated.

[0146] At this point, by shortening the pulse width D1 of the first sequence to a level that prevents magnetic saturation beforehand, the influence of magnetic saturation is minimized, making it less susceptible to its effects. However, the absence of magnetic saturation can lead to incorrect polarity determination. Therefore, in the second sequence, the pulse width D2 is made larger than D1 to induce magnetic saturation, making polarity determination reliable. By using the first magnetic pole position θest1 obtained in the first sequence and the polarity obtained in the second sequence to determine the initial magnetic pole position θest, the initial magnetic pole position θest can be determined with high accuracy.

[0147] In this embodiment, as explained above, by providing a pulse width and repetition number setting unit 440 in the voltage pulse generation unit 400B, the calculation accuracy of the initial magnetic pole position θest can be further improved.

[0148] Alternatively, the drive device 100B in this embodiment can be configured such that the number of repetitions Nmax, set by the pulse width and repetition count setting unit 440 of the voltage pulse generation unit 400B, is set to 2 or more, and the final calculated result of the initial magnetic pole position θest is determined based on the initial magnetic pole position θest values ​​calculated by the magnetic pole position estimation units 600A and 600B for each sequence. Specifically, by storing the initial magnetic pole positions θest for each sequence in advance in the magnetic pole position estimation units 600A and 600B, multiple initial magnetic pole positions θest corresponding to the number of repetitions Nmax are obtained. For the multiple initial magnetic pole positions θest obtained, a prescribed statistical processing such as averaging and convergence calculation is performed, thereby obtaining the final calculated result of the initial magnetic pole position θest. In addition, various applications are possible.

[0149] [Fourth Implementation Method]

[0150] Figure 15This is a structural diagram of the drive device 100C according to the fourth embodiment. The drive device 100C of this embodiment includes a position sensor 210 for detecting the magnetic pole position of the synchronous motor 200. By comparing the initial magnetic pole position θest calculated when the synchronous motor 200 is stopped with the magnetic pole position detected by the position sensor 210, it is determined whether the position sensor 210 is malfunctioning. Furthermore, regarding... Figure 1 The same parts as the structural diagrams of the drive device 100A in the first and second embodiments shown, and the same as those shown in the diagrams. Figure 12 The same parts as those in the structural diagram of the drive device 100B of the third embodiment shown are given the same reference numerals, and their descriptions are omitted.

[0151] In this embodiment, the synchronous motor 200 includes a position sensor 210 for detecting the position of the magnetic poles of the synchronous motor 200. The magnetic pole position detected by the position sensor 210 is input to one side of the comparison unit 700. The other side of the comparison unit 700 is input an initial magnetic pole position θest calculated by the magnetic pole position calculation unit 600A described in the first embodiment or the magnetic pole position calculation unit 600B described in the second embodiment. The magnetic pole position calculation units 600A and 600B use a phase command θ* output from the voltage pulse generation unit 400A described in the first embodiment or the voltage pulse generation unit 400B described in the third embodiment to calculate the initial magnetic pole position θest. Alternatively, in this embodiment, either the magnetic pole position calculation unit 600A or 600B can be used to calculate the initial magnetic pole position θest. When the synchronous motor 200 stops, the comparison unit 700 compares the calculated initial magnetic pole position θest with the magnetic pole position detected by the position sensor 210, and judges whether the position sensor 210 is abnormal based on the comparison result.

[0152] The position sensor 210, such as the rotary transformer, may malfunction due to a broken or short-circuited output winding. While the synchronous motor 200 is rotating, this malfunction is difficult to detect when the synchronous motor 200 is stopped. The magnetic pole position calculation units 600A and 600B, described in the first and second embodiments respectively, can calculate the initial magnetic pole position θest when the synchronous motor 200 is stopped, thus enabling the detection of position sensor 210 malfunctions even when the synchronous motor 200 is stopped. Therefore, a more reliable synchronous motor 200 drive device 100C can be provided.

[0153] In the first to fourth embodiments, the voltage pulse generation units 400A and 400B, the magnetic pole position calculation units 600A and 600B, and the comparison unit 700 were described as hardware, but their functions can also be implemented by a computer and a program. Furthermore, the program can be processed by a computer including a CPU and memory. All or part of the processing can also be implemented by hardware logic circuits. Moreover, this program can be supplied as a computer-readable computer program product in various formats, such as storage media and data signals (carrier waves).

[0154] The following effects can be obtained by implementing the methods described above.

[0155] (1) The drive devices 100A, 100B, and 100C for the synchronous motor 200 include: a power converter 300 that sequentially applies positive and negative voltages to each phase of the synchronous motor 200 to drive the synchronous motor 200; a current detection unit 500 that detects the phase current flowing through the synchronous motor 200; and a pole position calculation unit 600A and 600B that calculates the pole position of the rotor of the synchronous motor 200 based on the phase current detected by the current detection unit 500. The pole position calculation units 600A and 600B include: a first peak-to-peak detector 610 that detects the first peak-to-peak values ​​Iupp, Ivpp, and Iwpp, representing the difference between the maximum and minimum values ​​of the phase current; an orthogonal component detector 630 that detects the orthogonal component Iδ of the phase current; and a second peak-to-peak detector 620 that detects the second peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp, representing the difference between the maximum and minimum values ​​of the orthogonal component Iδ. When the synchronous motor 200 stops, based on the first peak-to-peak values ​​Iupp, Ivpp, Iwpp detected by the first peak-to-peak detector 610 and the second peak-to-peak values ​​Iδupp, Iδvpp, Iδwpp detected by the second peak-to-peak detector 620, the first magnetic pole position θest1 is calculated by the first magnetic pole position calculation unit 640. Based on this first magnetic pole position θest1, the initial magnetic pole position θest of the rotor is calculated by the second magnetic pole position calculation unit 660 or the fourth magnetic pole position calculation unit 680. Because of this structure, regardless of whether the synchronous motor 200 is an embedded magnet type synchronous motor or a surface magnet type synchronous motor, the initial magnetic pole position θest of the rotor of the synchronous motor 200 can be calculated with high accuracy when the synchronous motor 200 stops.

[0156] (2) The magnetic pole position calculation unit 600A preferably includes a polarity discriminator 650 for determining the polarity NS of the rotor's magnets. Based on the polarity NS determined by the polarity discriminator 650 and the first magnetic pole position θest1, the second magnetic pole position calculation unit 660 calculates the initial magnetic pole position θest. Because of this structure, the initial magnetic pole position θest can be accurately calculated based on the first magnetic pole position θest1 obtained by utilizing the inductance change caused by the salient polarity that occurs with a period of 1 / 2 times the rotation angle.

[0157] (3) The polarity discriminator 650 determines the polarity NS based on the difference between the absolute values ​​of the maximum and minimum phase currents, ΔIu, ΔIv, and ΔIw. Because of this structure, the polarity NS can be correctly determined according to the degree of magnetic saturation of the synchronous motor 200.

[0158] (4) When the synchronous motor 200 is stopped, the magnetic pole position calculation unit 600B calculates the second magnetic pole position θest2 using the third magnetic pole position calculation unit 670 based on the difference between the absolute values ​​of the maximum and minimum phase currents, ΔIu, ΔIv, and ΔIw. Based on the first magnetic pole position θest1 and the second magnetic pole position θest2, the fourth magnetic pole position calculation unit 680 determines the polarity of the rotor's magnets and calculates the initial magnetic pole position θest of the rotor based on the determined polarity and the first magnetic pole position θest1. Because of this structure, the time required to calculate the initial magnetic pole position θest can be minimized, and the initial magnetic pole position θest can be calculated with high accuracy.

[0159] (5) In the drive unit 100B, when the synchronous motor 200 is stopped, the power converter 300 applies positive and negative pulse voltages to each phase of the synchronous motor 200 multiple times with different pulse widths, based on the voltage commands Vu*, Vv*, and Vw* output from the voltage pulse generation unit 400B. The magnetic pole position calculation units 600A and 600B calculate the initial magnetic pole position θest based on the maximum and minimum values ​​of the phase current detected by the multiple pulse voltage applications performed by the power converter 300. Specifically, the magnetic pole position calculation units 600A and 600B calculate the first magnetic pole position θest1 based on the first peak-to-peak values ​​Iupp, Ivpp, and Iwpp, and the second peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp. The first peak-to-peak values ​​Iupp, Ivpp, and Iwpp are obtained based on the maximum and minimum values ​​of the phase current detected when a pulse voltage with a first pulse width D1 is applied. The second peak-to-peak values ​​Iδupp, Iδvpp, and Iδwpp are obtained based on the maximum and minimum values ​​of the orthogonal components of the phase current. Furthermore, based on the subtraction values ​​ΔIu, ΔIv, and ΔIw of the absolute values ​​of the maximum and minimum values ​​of the phase current detected when a pulse voltage with a second pulse width D2 (larger than the first pulse width D1) is applied, the polarity NS of the rotor's magnets is determined. Based on the calculation result of the first magnetic pole position θest1 and the determination result of the polarity NS, the initial magnetic pole position θest is calculated. Alternatively, the magnetic pole position estimation units 600A and 600B obtain multiple initial magnetic pole positions θest by calculating the initial magnetic pole position θest for each of the multiple pulse voltages applied, and determine the estimation result of the initial magnetic pole position θest based on the obtained multiple initial magnetic pole positions θest. Because of this structure, the estimation accuracy of the initial magnetic pole position θest can be further improved.

[0160] (6) In the drive unit 100C, the synchronous motor 200 includes a position sensor 210 that detects the position of the magnetic poles of the synchronous motor 200. Furthermore, the drive unit 100C for the synchronous motor 200 includes a comparison unit 700 that compares the initial magnetic pole position θest obtained by the magnetic pole position calculation units 600A and 600B with the magnetic pole position obtained by the position sensor 210. When the synchronous motor 200 is stopped, the comparison unit 700 determines whether the position sensor 210 is malfunctioning based on the comparison result. Because of this structure, a fault in the position sensor 210 can be detected even when the synchronous motor 200 is stopped, providing a drive unit for the synchronous motor 200 with higher reliability.

[0161] (7) The driving method of the synchronous motor 200 is a driving method of the synchronous motor 200 including a power converter 300 that sequentially applies positive and negative voltages to each phase of the synchronous motor 200 to drive the synchronous motor 200 and a current detection unit 500 that detects the phase current flowing in the synchronous motor 200. The driving method of the synchronous motor 200, when the synchronous motor 200 is stopped, acquires a first peak-to-peak value Iupp, Ivpp, Iwpp representing the difference between the maximum and minimum values ​​of the phase current detected by the current detection unit 500, and a second peak-to-peak value Iδupp, Iδvpp, Iδwpp representing the difference between the maximum and minimum values ​​of the quadrature component Iδ of the phase current. Based on the acquired first peak-to-peak value Iupp, Ivpp, Iwpp and second peak-to-peak value Iδupp, Iδvpp, Iδwpp, a first magnetic pole position θest1 is calculated, and based on the calculated first magnetic pole position θest1, the initial magnetic pole position θest of the rotor of the synchronous motor 200 is calculated. Therefore, regardless of whether the synchronous motor 200 is an embedded magnet type synchronous motor or a surface magnet type synchronous motor, the initial magnetic pole position θest of the rotor of the synchronous motor 200 can be calculated with high accuracy when the synchronous motor 200 is stopped.

[0162] This invention is not limited to the above-described embodiments. Other embodiments conceivable within the scope of the technical concept of this invention, as long as they do not impair the characteristics of the invention, are also included within the scope of this invention. Furthermore, a portion of the structure of one embodiment can be replaced with the structure of another embodiment, or the structure of another embodiment can be added to the structure of one embodiment.

[0163] Explanation of reference numerals in the attached figures

[0164] 100A, 100B, 100C... Drive unit, 200... Synchronous motor, 210... Position sensor, 300... Power converter, 400A, 400B... Voltage pulse generation unit, 410... Voltage command generation unit, 420... Phase switcher, 430... Command coordinate transformation unit, 440... Pulse width and repetition count setting unit, 500... Current detection unit, 600A, 600B... Magnetic pole position calculation unit, 610... First peak-to-peak detector, 620... Second peak-to-peak detector, 630... Quadrature component detector, 640... First magnetic pole position calculation unit, 650... Polarity discriminator, 651... Peak detector, 652... Absolute value operation unit, 653... Subtraction unit, 654... Coordinate transformation unit, 655... Polarity operation unit, 660... Second magnetic pole position operation unit, 670... Third magnetic pole position operation unit, 671... Peak detector, 672... Absolute value operation unit, 673... Subtraction unit, 674... Coordinate transformation, 675... Position operation unit, 680... Fourth magnetic pole position operation unit, 681... Subtraction processing unit, 682... Absolute value processing unit, 683... Threshold judgment unit, 684... Initial magnetic pole position calculation unit, 700... Comparison unit.

Claims

1. A drive device for a synchronous motor, comprising: A power converter that sequentially applies positive and negative voltages to each phase of a synchronous motor to drive the synchronous motor; A current detection unit for detecting the phase current flowing through the synchronous motor; The synchronous motor drive device is characterized by having a magnetic pole position estimation unit that estimates the magnetic pole position of the rotor of the synchronous motor based on the phase current detected by the current detection unit, and a magnetic pole position estimation unit that estimates the magnetic pole position of the rotor of the synchronous motor. The magnetic pole position calculation unit includes: A first peak-to-peak detector is used to detect a first peak-to-peak value that represents the difference between the maximum and minimum values ​​of the phase current; A quadrature component detector for detecting quadrature components based on the phase current; and A second peak detector is used to detect the second peak value, which represents the difference between the maximum and minimum values ​​of the orthogonal components. During the synchronous motor's stop period, the first magnetic pole position is calculated based on the first peak-to-peak value detected by the first peak-to-peak detector and the second peak-to-peak value detected by the second peak-to-peak detector. The initial magnetic pole position of the rotor is calculated based on the position of the first magnetic pole.

2. The synchronous motor drive device as described in claim 1, characterized in that: The magnetic pole position estimation unit further includes a polarity discriminator for determining the polarity of the magnets of the rotor, and calculates the initial magnetic pole position based on the polarity determined by the polarity discriminator and the first magnetic pole position.

3. The synchronous motor drive device as described in claim 2, characterized in that: The polarity discriminator determines the polarity based on the difference between the absolute values ​​of the maximum and minimum phase currents.

4. The synchronous motor drive device as described in claim 1, characterized in that: During the period when the synchronous motor stops, the magnetic pole position estimation unit calculates the second magnetic pole position based on the difference between the absolute values ​​of the maximum and minimum phase currents, determines the polarity of the rotor's magnets based on the first and second magnetic pole positions, and estimates the initial magnetic pole position of the rotor based on the determined polarity and the first magnetic pole position.

5. The drive device for a synchronous motor as described in claim 1, characterized in that: The power converter applies positive and negative pulse voltages sequentially to each phase of the synchronous motor multiple times with different pulse widths during the period when the synchronous motor is stopped. The magnetic pole position estimation unit estimates the initial magnetic pole position based on the maximum and minimum values ​​of the phase current detected by applying multiple pulse voltages to the power converter.

6. The drive device for a synchronous motor as described in claim 5, characterized in that: The magnetic pole position estimation unit calculates the first magnetic pole position based on the first peak-to-peak value and the second peak-to-peak value. The first peak-to-peak value is obtained based on the maximum and minimum values ​​of the phase current detected when a pulse voltage with a first pulse width is applied, and the second peak-to-peak value is obtained based on the maximum and minimum values ​​of the orthogonal components of the phase current. The magnetic pole position calculation unit determines the polarity of the rotor's magnets based on the subtraction of the absolute values ​​of the maximum and minimum values ​​of the phase current detected when a pulse voltage with a second pulse width greater than the first pulse width is applied. The magnetic pole position estimation unit estimates the initial magnetic pole position based on the calculation result of the first magnetic pole position and the polarity discrimination result.

7. The drive device for a synchronous motor as described in claim 5, characterized in that: The magnetic pole position estimation unit obtains multiple initial magnetic pole positions by applying multiple pulse voltages to calculate the initial magnetic pole position, and determines the estimation result of the initial magnetic pole position based on the obtained multiple initial magnetic pole positions.

8. The drive device for a synchronous motor as described in claim 1, characterized in that: The synchronous motor includes a position sensor for detecting the position of the magnetic poles of the synchronous motor. The drive unit of the synchronous motor includes a comparison unit that compares the initial magnetic pole position obtained by the magnetic pole position calculation unit with the magnetic pole position obtained by the position sensor. The comparison unit determines whether the position sensor is malfunctioning based on the comparison result during the period when the synchronous motor is stopped.

9. A method for driving a synchronous motor, comprising a driving device for the synchronous motor, the driving device comprising: A power converter that sequentially applies positive and negative voltages to each phase of a synchronous motor to drive the synchronous motor; The synchronous motor driving method is characterized by including a current detection unit for detecting the phase current flowing through the synchronous motor and a current detection unit for detecting the phase current flowing through the synchronous motor. During the period when the synchronous motor is stopped, a first peak-to-peak value representing the difference between the maximum and minimum values ​​of the phase current detected by the current detection unit and a second peak-to-peak value representing the difference between the maximum and minimum values ​​of the quadrature components of the phase current are acquired. A first magnetic pole position is calculated based on the first peak-to-peak value and the second peak-to-peak value, and the initial magnetic pole position of the rotor of the synchronous motor is deduced based on the first magnetic pole position.

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