Inductance measuring device and inductance measuring method

Abstract

The inductance measuring device (10) includes a power conversion unit (2) that applies a voltage to an AC machine (11), a voltage command generation unit (1) that generates a voltage command for the power conversion unit, and an inductance calculation unit (4) that calculates the inductance of the AC machine based on a first current that flows through the AC machine when a first voltage is applied to the AC machine and a second current that flows through the AC machine when a second voltage is applied to the AC machine after the first voltage is applied. The voltage command generation unit generates a first d-axis voltage command that commands a voltage on the d-axis of a rotating coordinate system and a first q-axis voltage command that commands a voltage on the q-axis based on a first voltage command that commands a first voltage and a determined voltage division standard, the first d-axis voltage command and the first q-axis voltage command that commands a voltage on the q-axis of a rotating coordinate system being multiple and equal in number, such that if a zero voltage command is included, the zero voltage command is executed before a non-zero voltage command, and commands the power conversion unit to apply a voltage to the AC machine multiple times based on the generated multiple first d-axis voltage commands and first q-axis voltage commands.

Description

[Technical field]

[0001] The present disclosure relates to an inductance measurement device and an inductance measurement method for measuring the inductance of an AC machine. [Background technology]

[0002] In controlling an AC machine, information such as the inductance of the AC machine is used as a control parameter. Therefore, it is necessary to obtain the control parameters before starting the control of the AC machine. Patent Document 1 discloses a control device for a rotating machine that can measure the inductance of the rotating machine.

[0003] The control device described in Patent Document 1 repeatedly applies a plurality of voltage commands so that the d-axis current or the q-axis current becomes a target current, and then measures the inductance.

[0004] Specifically, in the control device described in Patent Document 1, a first voltage command (voltage command for preparation for measurement) is given to the voltage application section multiple times to raise the shaft current of the rotating machine to the measurement point, and then a second voltage command (voltage command for measurement) is given to generate a minute current change, and the inductance is calculated from the current change and voltage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5634620 Summary of the Invention [Problem to be solved by the invention]

[0006] In the technology described in Patent Document 1, a voltage is applied in an arbitrary vector direction of a rotating coordinate system, and the currents on the d-axis and q-axis are detected to measure the inductance of each axis individually. However, when applying a voltage to both the d-axis and the q-axis to measure the inductance while current is flowing on both the d-axis and the q-axis, the measurement accuracy of the d-axis current and the q-axis current may deteriorate depending on the method of voltage application.

[0007] Here, as a comparative example, a control operation in which the measurement accuracy of the d-axis current and the q-axis current deteriorates will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a diagram showing an example of voltage commands for the d-axis and q-axis in the control operation of the comparative example, and Fig. 3 is a diagram showing an example of time changes in voltage and current when the control operation of the comparative example is executed. In the following description, the d-axis and the q-axis may be collectively referred to as the dq-axis or the d-axis and q-axis.

[0008] When measuring the inductance with both the d-axis and q-axis energized, it is necessary to simultaneously apply voltage to the d-axis and q-axis as a voltage command, using the voltage vector. However, when the axial current increases stepwise by applying voltage commands multiple times to the power conversion means that drives the AC machine, if the number of non-zero voltage commands differs between the d-axis and q-axis, for example, when the voltage command for raising the dq-axis current to the measurement point is the voltage vector shown in Figure 2, the d-axis current I d When a non-zero voltage command is given twice, the measurement point is reached and the q-axis current I q For the q-axis current I q When the measurement point is reached and the actual measurement is performed, the d-axis current I d The value shown by the white circle (○) is lower than the value at the actual measurement point shown by the black circle (●). Therefore, the measured value of the d-axis current contains an error compared to the target value that we wanted to raise, which is a factor in deteriorating the inductance measurement accuracy.

[0009] The present disclosure has been made in view of the above, and has an object to provide an inductance measuring device capable of measuring the inductance of an AC machine with high accuracy. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems and achieve the object, the inductance measuring device according to the present disclosure includes a power conversion unit that applies a voltage to an AC machine, a voltage command generation unit that generates a voltage command for the power conversion unit, and an inductance calculation unit that calculates an inductance of the AC machine based on a first current that flows through the AC machine when a first voltage is applied to the AC machine and a second current that flows through the AC machine when a second voltage is applied to the AC machine after the first voltage is applied, and is characterized in that the voltage command generation unit generates a first d-axis voltage command that commands a voltage on the d-axis of a rotating coordinate system and a first q-axis voltage command that commands a voltage on the q-axis based on a first voltage command that commands a first voltage and a determined voltage division criterion, the voltage command generation unit generates a first d-axis voltage command that commands a voltage on the d-axis of a rotating coordinate system and a first q-axis voltage command that commands a voltage on the q-axis of the rotating coordinate system in multiple and equal numbers, such that if a zero voltage command is included, the zero voltage command is executed before a non-zero voltage command, and further commands the power conversion unit to apply voltages to the AC machine multiple times based on the generated multiple first d-axis voltage commands and first q-axis voltage commands. Effect of the Invention

[0011] The inductance measuring device according to the present disclosure has an effect of being able to measure the inductance of an AC machine with high accuracy. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a configuration example of an inductance measuring device according to a first embodiment; [Diagram 2] FIG. 13 is a diagram showing an example of d-axis and q-axis voltage commands in a control operation of a comparative example; [Diagram 3] FIG. 13 is a diagram showing an example of changes in voltage and current over time when a control operation in a comparative example is executed; [Figure 4] Diagram showing steady-state inductance [Diagram 5]Diagram showing differential inductance [Figure 6] 1 is a flowchart showing an example of an inductance measuring operation of the inductance measuring device according to the first embodiment; [Figure 7] FIG. 1 is a diagram showing an example of a method for dividing a first voltage vector command by a voltage command generating unit of the inductance measuring device according to the first embodiment; [Figure 8] FIG. 1 is a diagram showing an example of an operation in which the inductance measuring device according to the first embodiment applies a voltage to an AC machine to increase a current to a first measurement point. [Figure 9] FIG. 1 is a diagram showing an example of an operation in which the inductance measuring device according to the first embodiment applies a voltage to an AC machine to increase a current to a second measurement point. [Figure 10] FIG. 13 is a diagram showing an example of a method for dividing a first voltage vector command by a voltage command generating unit of the inductance measuring device according to the second embodiment; [Figure 11] FIG. 13 is a diagram showing an example of an operation of the inductance measuring device according to the second embodiment, in which a voltage is applied to an AC machine to increase a current to a first measurement point. [Figure 12] 13 is a flowchart showing an example of an inductance measuring operation of the inductance measuring device according to the fourth embodiment. [Figure 13] FIG. 1 is a diagram showing an example of hardware for implementing an inductance measuring device according to the first to sixth embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an inductance measuring device and an inductance measuring method according to embodiments of the present disclosure will be described in detail with reference to the drawings.

[0014] In each embodiment described below, the components of each phase of a three-phase AC are represented as U-phase, V-phase, and W-phase, and the two axes in the rotating coordinate system are represented as d-axis and q-axis. The d-axis is a reference direction in the rotating coordinate system, and is set, for example, to the direction of the field in the rotating coordinate system of a synchronous machine having a field magnet, and to the maximum or minimum direction of the inductance in the rotating coordinate system of a reluctance-type synchronous machine having no field magnet. These reference directions are referred to as θ e The reference direction θ e can be detected using known techniques, for example, the technique disclosed in Japanese Patent No. 4271397.

[0015] Embodiment 1 FIG. 1 is a diagram showing a configuration example of an inductance measurement device 10 according to a first embodiment. The inductance measurement device 10 includes a voltage command generation unit 1, a power conversion unit 2, a current detection unit 3, an inductance calculation unit 4, and a coordinate conversion unit 5. The inductance measurement device 10 measures an inductance to be used as a control parameter of an AC machine 11, such as an AC motor. Although not shown in FIG. 1, the AC machine 11 is assumed to be connected to a load machine. The hardware configuration of the inductance measurement device 10 is similar to that of a power conversion device that supplies three-phase AC power to the AC machine 11 to drive the AC machine 11. The function of measuring the inductance of the AC machine 11, which is realized by the inductance measurement device 10, may be included in the functions of the power conversion device that drives the AC machine 11.

[0016] The voltage command generator 1 generates voltage commands (V d * ,V q * ) and then transform them into (V d * ,V q * ) corresponding to the three-phase voltage command (V u * ,V v * ,V w *) and outputs it to the power conversion unit 2. The voltage command generation unit 1 also generates voltage commands (V d * ,V q * ) to the inductance calculation unit 4. The power conversion unit 2 generates a three-phase AC voltage commanded by the voltage command input from the voltage command generation unit 1, and applies the voltage to the AC machine 11. The current detection unit 3 detects the current (I u ,I v ,I w The coordinate conversion unit 5 converts the three-phase currents detected by the current detection unit 3 into d-axis currents (I d ) and q-axis current (I q ) and outputs it to inductance calculation unit 4. Inductance calculation unit 4 calculates the inductance of AC machine 11 based on the d-axis voltage command and q-axis voltage command input from voltage command generation unit 1 and the d-axis current and q-axis current input from coordinate conversion unit 5.

[0017] In the inductance measuring device 10, the inductance calculation unit 4 calculates the inductance of the AC machine 11 based on the measurement values ​​of the currents of each axis with both the d-axis and q-axis energized. At this time, the voltage command generation unit 1 outputs three-phase voltage commands corresponding to the voltage commands of the d-axis and q-axis to the power conversion unit 2 multiple times, and raises the currents of each axis to the measurement points. In addition, when raising the currents of each axis to the measurement points and measuring them, a voltage is applied that can avoid deterioration of the current measurement accuracy.

[0018] Next, a detailed operation of the inductance measuring device 10 according to this embodiment will be described.

[0019] In the following, the inductance of AC machine 11 measured by inductance measurement device 10 will be defined in two ways, as shown in the following formula (1) and formula (2). Formula (1) is the origin gradient between magnetic flux and current, and is called steady-state inductance L. Formula (2) is the gradient between local magnetic flux change and current change, and is called differential inductance L'. These are shown in Figures 4 and 5. Figure 4 shows steady-state inductance L, and Figure 5 shows differential inductance L'.

[0020]

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[0021]

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[0022] From equations (1) and (2), the steady-state inductance L and the differential inductance L' have the relationship shown in equation (3).

[0023]

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[0024] A flowchart of the operation of the inductance measuring device 10 to measure inductance is shown in Fig. 6. Fig. 6 is a flowchart showing an example of the inductance measuring operation of the inductance measuring device 10 according to the first embodiment.

[0025] When measuring inductance, the inductance measuring device 10 first generates a first voltage vector command V1 which commands a measurement preparation voltage, which is a first voltage. * Based on the first divided voltage vector command V1 * [n1] (n1=1, 2, ...) is generated (step S11). Specifically, the voltage command generating unit 1 generates a measurement preparation voltage vector command V1 * Based on this, one or more first divided voltage vector commands V1 *Generate [n1] (n1=1,2,…).

[0026] The AC machine 11 is connected to a load machine, and it is desirable to be able to measure the inductance without causing vibration or noise. To do this, it is necessary to raise the current to the target measurement point by applying a voltage for an extremely short period of time. Therefore, the voltage vector command V1 * In many cases, V1 is a large voltage that exceeds the range of voltages that can be output by the inductance measuring device 10. * Based on this, one or more first divided voltage vector commands V1 * [n1] (n1=1, 2, ...) is generated and divided into multiple voltage applications. This reduces the size of each voltage vector, making it possible to apply such a large voltage. In addition, multiple voltage applications cause the current to rise stepwise to the measurement point, and by measuring the current at each step of the rise and monitoring to see if an excessive current is flowing, it is also possible to protect the inductance measurement device 10 and the AC machine 11.

[0027] The voltage command generating unit 1 generates a first divided voltage vector command V1 * The operation of generating [n1] (n1=1, 2, . . . ) will be described in detail later.

[0028] Next, the inductance measuring device 10 calculates a first divided voltage vector command V1 * Specifically, the voltage command generating unit 1 applies one or more first divided voltage vector commands (V1 * [1],V1 * [2],V1 * [3], . . . ) in sequence to the power conversion unit 2. The power conversion unit 2 applies to the AC machine 11 voltages commanded by each of the one or more first divided voltage vector commands.

[0029] The operations in steps S11 and S12 will be described in detail below using a specific example.

[0030] The voltage command generator 1 has a reference direction θ e and the first voltage vector command V1 * The first voltage vector command V1 is set. * is a voltage vector command for passing a first current vector I1, which is a target current, through the AC machine 11. The target current is a current when the AC machine 11 outputs a torque to a load machine. This first voltage vector command V1 * is set by a user via a UI (User Interface) not shown in FIG. 1, for example, before the inductance measuring device 10 starts an inductance measuring operation.

[0031] First voltage vector command V1 * The size of |V1 * |, reference direction θ e First voltage vector command V1 * The phase of θ v1 * In this case, the voltage command generating unit 1 generates a first voltage vector command V1 as shown in FIG. * Any voltage division reference V st According to this, the size is V st A plurality of first divided voltage vector commands V1 having the same phase are * [n1] (n1=1, 2, . . . ). Note that FIG. 7 shows the first voltage vector command V1 generated by the voltage command generating unit 1 of the inductance measuring device 10 according to the first embodiment. * FIG. 7 is a diagram showing an example of a division method of θ v is the first voltage vector command V1 * Phase θ v1 * That is, θ v =θ v1 * The voltage division reference V st is the first voltage division reference.

[0032] Here, the voltage division reference V stmay be set within the range of voltages that the inductance measuring device 10 can output. For example, the voltage division reference V st The rated voltage here is the voltage taking into consideration the wiring of the power conversion unit 2 and the AC machine 11. If the rated voltage is specified by the phase voltage effective value, then the phase voltage effective value = voltage vector magnitude × 1 / √3, so √3 × rated voltage is set as V st If the rated voltage is specified by the effective line voltage, then the effective line voltage = the magnitude of the voltage vector, so the rated voltage can be set to V st Just set it to

[0033] A first voltage vector command V1 corresponding to the first voltage command * In the division operation, the voltage command generating unit 1 first generates a first divided voltage vector command V1 * [n1] Determine the size of each. |V1 * | to V st The quotient and remainder are k1 (k1: integer) and V 1k Let |V1 * If the number of divisions of | is n1, then |V1 * |=k1×V st +V 1k Therefore, n1=k1+1. First divided voltage vector command V1 * Size of [n1]|V1 * |[n1] is expressed by the following equation (4).

[0034]

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[0035] Next, the voltage command generating unit 1 generates a first voltage vector command V1 * Phase θ v1 * Using V1 * [n1] is separated into d-axis and q-axis components, and multiple d-axis voltage commands V 1d * [n1]=|V1 *|[n1]×cosθ v1 * and the q-axis voltage command V 1q * [n1]=|V1 * |[n1]×sinθ v1 * By dividing in this way, the number of voltage commands on both the d and q axes becomes n1, and all voltage commands are non-zero.

[0036] The voltage command generator 1 generates the divided d-axis voltage command V 1d * [n1] and q-axis voltage command V 1q * For [n1], the reference direction θ e Based on this, dq-three-phase coordinate transformation is performed, and the three-phase voltage command V u * , V v * and V w * Then, the voltage command generator 1 generates the three-phase voltage command V u * , V v * and V w * is output to the power conversion unit 2.

[0037] The power conversion unit 2 converts the three-phase voltage command V u * , V v * and V w * According to the voltage vector V1 * [n1] is applied to the AC machine 11.

[0038] In this way, the inductance measuring device 10 detects the first voltage vector command V1 * Divide it into d-axis voltage command V 1d * [n1] and q-axis voltage command V 1q * [n1] is generated and the d- and q-axis voltage commands are repeatedly executed multiple times to apply a voltage to the AC machine 11. As a result, the d-axis current I 1d and the q-axis current I1q is changed as shown in Fig. 8 and raised to the measurement point. Fig. 8 is a diagram showing an example of the operation of the inductance measuring device 10 according to the first embodiment, in which the inductance measuring device 10 applies a voltage to the AC machine 11 to raise the current to the first measurement point. Figs. 7 and 8 show the operation of the inductance measuring device 10 when the first voltage vector command V1 * This shows an example of executing the above in four separate steps.

[0039] Returning to the description of FIG. 6, the inductance measuring device 10 next detects the first current vector I1 (step S13). Specifically, the current detector 3 detects the first current vector I1. The first current vector I1 is determined based on the first voltage vector command V1 * All d-axis voltage commands V obtained by dividing 1d * [n1] and q-axis voltage command V 1q * This is the current vector at the time when application of the measurement preparation voltage to the AC machine 11 is completed by executing [n1].

[0040] Next, the inductance measuring device 10 outputs a second voltage vector command V2 which commands a measurement voltage that is a second voltage. * Based on the second divided voltage vector command V2 * [n2] (n2=1, 2, ...) is generated (step S14), and the second divided voltage vector command V2 * [n2] is applied (step S15). Then, the inductance measuring device 10 detects the second current vector I2 (step S16). These steps S14 to S16 are the same processes as the above-mentioned steps S11 to S13. * is the first voltage vector command V1 * Similarly, it is assumed that the number of the inputs is preset.

[0041] Here, the second voltage vector command V2 * Regarding the first voltage vector command V1 *The voltage should be applied so that the current is changed by the amount of change ΔI used for inductance calculation from the current I1 at the time of completion of application. * | can be set arbitrarily. |V2 * | is the voltage division reference V st It is possible to set the voltage to the following value so that the voltage application is completed in one go, but since the inductance of the AC machine 11 is large, V st If the voltage applied is not enough to cause a change in current, V st A value exceeding the first voltage vector command V1 is determined. * Similarly to the case of * [n2]. If division is not necessary, the voltage command generator 1 generates the second voltage vector command V2 * V2 * Set it to [1].

[0042] A second voltage vector command V2 corresponding to the second voltage command * FIG. 9 shows an example of the operation of the inductance measuring device 10 according to the first embodiment, in which the inductance measuring device 10 applies a voltage to the AC machine 11 to increase the current to the second measurement point. In steps S14 to S16, as shown in FIG. 9, the first voltage vector command V1 * The first current vector I1(I 1d ,I 1q ) is conducting, and then a second current vector I2 (I 2d ,I 2q ) is energized, generating a current change ΔI = I2 - I1.

[0043] After detecting the second current vector I2 in step S16, the inductance measuring device 10 calculates the inductance of the AC machine 11 (step S17). *From the voltage change ΔV and the current change ΔI, the inductance is calculated. The calculated inductance is stored in a storage unit (not shown in FIG. 1, for example), and can be referred to when necessary, such as when driving the AC machine 11. The inductance measuring device 10 may display the calculation result of the inductance on a display device and notify it to the outside. Details of the inductance calculation process by the inductance calculation unit 4 will be described later.

[0044] When the voltage application described in this embodiment is used, since the number of divisions of the voltage vector commands for each of the d-axis and q-axis is the same, as shown in FIGS. 7, 8, and 9, the same number of non-zero voltage applications are performed on the d-axis and q-axis. It becomes possible to reach the target current simultaneously on the d-axis and q-axis at the time when the voltage application is completed, and it is possible to prevent the current on one axis from dropping after reaching the target current.

[0045] Also, by using the d-axis voltage command V 1d * [n1] and the q-axis voltage command V 1q * [n1], each current reached by each voltage application takes a low value, and when the inductance takes a large value, the time constant becomes long. As a result, the current drop from the completion of each voltage application to the next voltage application becomes gentle, and the current can be appropriately increased by each voltage application.

[0046] Furthermore, since the command of 0 voltage is not included in the n1 voltage applications, it is also possible to set a measurement point in the middle of the n1 voltage applications. Using an integer m1 where 1 < m1 < n1, the intermediate voltage command is represented as V1 * [m1]. Considering V1 * [m1] as the first voltage command and V1 * [m1 + 1] as the second voltage command, inductance calculation is performed. Subsequently, considering V1 * [m1 + 1] as the first voltage command and V1 * [m1 + 2] as the second voltage command, inductance calculation is performed, and V1 *This is repeated until the application of I1 is completed. In this manner, it is possible to obtain an effect that not only the inductance due to the current vector I1 at the measurement point but also the inductance due to the current vector on the way to I1 can be measured at the same time.

[0047] Next, the details of the inductance calculation process performed by the inductance calculation unit 4 will be described.

[0048] The inductance calculation unit 4 calculates the inductance on the dq axes. If the voltage on one of the dq axes is v, the current is i, the winding resistance is R, and the armature interlinkage magnetic flux is φ, then the voltage equations for the dq axes when the AC machine 11 is not rotating are expressed by equations (5) and (6), ignoring terms related to the rotation speed.

[0049]

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[0050]

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[0051] From equations (5) and (6), the magnetic flux change dφ is dφ=(v-Ri)dt. Also, the d-axis current change di d The change in q-axis magnetic flux due to q / di d And the q-axis current change di q The d-axis magnetic flux change due to d / di q If we assume that the magnetic flux change due to interference between the d and q axes is sufficiently smaller than the magnetic flux change caused by current changes in the d and q axes themselves and can be ignored, then the differential inductance L' can be calculated as shown in equations (7) and (8) in addition to equation (2) above.

[0052]

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[0053]

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[0054] When calculating the inductance of the AC machine 11 by applying a voltage using the inductance measuring device 10 according to the present embodiment, the voltage vector command V2 * The magnetic flux change Δφ caused by [n2] (n2=1, 2, …) is calculated as t s This results in equations (9) and (10).

[0055]

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[0056]

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[0057] Here, when measuring inductance, particularly when the current I1 is increased to a high current, the voltage due to the resistance drop of RI1 in equations (9) and (10) is relatively small compared to V2, so approximate calculations such as those shown in equations (11) to (16) below can also be used.

[0058] If the resistance drop at the time of application of each voltage vector command is omitted and only the resistance drop at the time of application of the final voltage vector command is considered, calculations may be performed using equations (11) and (12), which are equivalent to the case where all voltage vector commands before division are applied by a single voltage application.

[0059]

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[0060]

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[0061] However, V 2d * and V 2q * is the dq-axis voltage command before division, I 1d [n2] and I 1q [n2] is the current when the final voltage vector command is applied.

[0062] Moreover, the calculation may be performed as in equations (13) and (14) in which the resistive drop is entirely omitted.

[0063]

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[0064]

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[0065] Since equations (13) and (14) are equivalent to the case where all voltage vector command values ​​before division are applied in one voltage application, calculations may be performed as in equations (15) and (16).

[0066]

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[0067]

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[0068] According to each of the calculation formulas (11) to (16), the number of current measurement points can be reduced.

[0069] In addition, the differential inductance L' can be calculated from the magnetic flux change amount obtained from any one of equations (9) to (16) and the current change amount ΔI during that time, as shown in equations (17) and (18).

[0070]

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[0071]

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[0072] Furthermore, because of the relationship in equation (3), it is possible to find the steady-state inductance L from the measurement results of the differential inductance L'. There are various possible methods for the actual calculation, but one method with a light computational load is to determine an approximation function of L(I) and express L(I) as an equation for L'(I). For example, if L(I) is approximated by a linear function related to the current, it can be expressed as L(I) = aI + b. Therefore, from equation (3), L'(I) = a·I + (aI + b) = 2aI + b, and it can be seen that L(I) is a function with the same intercept as L'(I) and a slope of 1 / 2.

[0073] Although a linear function has been described as an example of the approximation function, calculations can be performed assuming any function, such as a higher-order function or a logarithmic function.

[0074] L'(I) as a function of current can be calculated as an approximate function using a method such as the least squares method if there are measurement results for each of L'(I1) for multiple I1s.

[0075] Measurements of multiple L'(I1) can be done, for example, by multiple |V1 * | * A plurality of first voltage vector commands V1 according to | * Then, L' for multiple I1's can be measured according to the first embodiment using the above.

[0076] Alternatively, as described above, in the inductance measurement by the inductance measuring device 10 according to this embodiment, since the n1 voltage applications do not include a 0 voltage command, it is also possible to set the measurement point midway through the n1 voltage applications. Therefore, by simultaneously measuring not only the inductance at a single point due to I1 at the measurement point, but also the inductance for each current up to I1, multiple L'(I) can be obtained.

[0077] In addition, according to the inductance calculation method by the inductance measuring device 10 of the present embodiment, the application time t s Since the time may be set to an extremely short time, it is possible to perform inductance measurement while minimizing vibration and noise of the AC machine 11.

[0078] As described above, the inductance measuring device 10 according to the present embodiment uses the first voltage vector command V1 which commands the measurement preparation voltage. * The voltage division reference V st Based on the above, a first divided voltage vector command V1 * [n1] is generated, and then it is separated into a d-axis component and a q-axis component to generate voltage commands for the d-axis and q-axis. This makes the number of voltage commands for the d-axis and the number of voltage commands for the q-axis the same, preventing a deterioration in the inductance measurement accuracy due to the measured current value on one axis dropping below the actual value.

[0079] Embodiment 2 Next, a description will be given of embodiment 2. The configuration of an inductance measuring device according to embodiment 2 is similar to that of embodiment 1 (see FIG. 1), but a part of the inductance measuring operation is different from that of embodiment 1. In this embodiment, the parts different from embodiment 1 will be described.

[0080] The inductance measuring device 10 according to the second embodiment uses the first divided voltage vector command V1 * Generation process of [n1] (step S11 in FIG. 6), second divided voltage vector command V2 * The generation process of [n2] (step S14 in FIG. 6) is different from that of the first embodiment. * Generation of [n1] and second divided voltage vector command V2 * For this reason, in this embodiment, the first divided voltage vector command V1 *An example of a process for generating the second divided voltage vector command V2 * The process of generating [n2] will not be described.

[0081] The voltage command generating unit 1 generates a first divided voltage vector command V1 * When generating [n1], first, the voltage vector command V1 * is separated into d-axis and q-axis components, and the d-axis voltage command V 1d * and the q-axis voltage command V 1q * Request.

[0082] Next, the voltage command generating unit 1 divides the voltage command for each axis in the same procedure as in the first embodiment. Specifically, the voltage command generating unit 1 divides the voltage command for each axis by a voltage division reference V stdq According to this, the d-axis voltage command V 1d * and the q-axis voltage command V 1q * are divided into a plurality of first d-axis divided voltage commands V 1d * [n 1d ](n 1d =1,2,…) and multiple first q-axis divided voltage commands V 1q * [n 1q ](n 1q = 1, 2, ...) is calculated. Note that the voltage division reference V stdq Let be the second voltage division reference.

[0083] Here, the voltage division reference V stdq may be set within the range of the dq-axis voltages that the inductance measuring device 10 can output. For example, it may be set to the rated voltage of the power conversion unit 2×1 / √2 or the rated voltage of the AC machine 11×1 / √2. By setting in this way, the dq-axis voltages after division are each maximum value V stdq Even if the voltage vector is taken as above, the magnitude of the combined voltage vector will not exceed the rated voltage. The rated voltage here is a voltage that takes into consideration the connections of the power conversion unit 2 and the AC machine 11, as in the first embodiment.

[0084] d-axis voltage command V 1d * The magnitude of |V 1d * | to V stdq The quotient and remainder are k 1d (k 1d : integer) and V 1kd Then, the first d-axis divided voltage command V 1d * [n 1d ] is expressed by the following formula (19). 1d =k 1d +1.

[0085]

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[0086] In addition, the q-axis voltage command V 1q * The magnitude of |V 1q * | to V stdq The quotient and remainder are k 1q (k 1q : integer) and V 1kq Then, the first q-axis divided voltage command V 1q * [n 1q ] is expressed by the following formula (20). 1q =k 1q +1.

[0087]

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[0088] Next, the voltage command generating unit 1 calculates n 1d and 1q Here, we compare with n 1d <n 1q The following will be explained using the above case as an example.

[0089] n 1d <n 1q In this case, the first d-axis divided voltage command V 1d* [n 1d ] is the first q-axis divided voltage command V 1q * [n 1q ], the voltage command generator 1 adds n 1q -n 1d Add 0 voltage command to only n 1q Specifically, the voltage command generating unit 1 adds a zero voltage command to the first half of the d-axis voltage vector command to generate a new first d-axis divided voltage command V 1dd * [n 1q ](n 1q =1,2,…).

[0090]

number

[0091] Here, n 1d <n 1q We have taken the case of n as an example. 1d >n 1q In the case of V 1q * [n 1q ] is processed in the same way to add a 0 voltage command, and a new q-axis voltage command V 1qq * [n 1d ](n 1d =1,2,…) and n 1d =n 1q In this case, the voltage command generating unit 1 does not perform the process of adding a 0 voltage command.

[0092] d-axis divided voltage command V 1dd * [n 1q ] and q-axis divided voltage command V 1q * [n 1q ], as shown in Figs. 10 and 11, the d-axis first receives the 0 voltage command (V 1dd * [1], V 1dd *[2]) is applied, and then V 1d * [n 1d ] is equivalent to V 1dd * [n 1q ] is applied. Therefore, the timing of voltage application completion is aligned between the d and q axes, and the target current is reached simultaneously on the d and q axes at the time of voltage application completion. Therefore, as in the first embodiment, it is possible to prevent a deterioration in the measurement accuracy of the inductance caused by the measured current value on one axis dropping below the actual value.

[0093] Embodiment 3 Next, a description will be given of a third embodiment. The configuration of an inductance measuring device according to the third embodiment is similar to that of the first embodiment (see FIG. 1). In this embodiment, differences from the first embodiment will be described.

[0094] Before executing the operation shown in the flowchart of FIG. 6 described in the first embodiment, the voltage command generating unit 1 according to the third embodiment executes the first voltage vector command to calculate the magnitude |V1 of the first voltage vector command based on the current target value |I1| to be reached. * Calculates |.

[0095] The voltage command generator 1 calculates a magnitude |V1 of a first voltage vector command. * When calculating |, first calculate the effective value φ of the interlinkage magnetic flux created by the inductance. r Here, let the rated voltage of the AC motor 11 be V r [Vrms], rated current I r [Arms], field magnet φ f [Wb], rated frequency is f r [Hz], assuming that during rated operation, a terminal voltage equivalent to the rated voltage is applied, the rated current flows, and the motor is driven at the rated frequency, the effective value of the interlinkage magnetic flux created by the inductance is φ r can be calculated as shown in equation (22).

[0096]

number

[0097] In the case of a reluctance type AC machine without a field magnet, φ f = 0 and use equation (22). The voltage command generator 1 converts the inductance calculated according to equation (23) into the rated inductance L r It is stipulated that:

[0098]

number

[0099] The voltage command generator 1 then calculates the rated inductance L r Using the current target value |I1|, the magnitude of the first voltage vector command |V1 * Calculates |.

[0100]

number

[0101] The voltage command generator 1 calculates a magnitude |V1 of a first voltage vector command. * After calculating |, this |V1 * Using |, the inductance measurement described in the first embodiment (steps S11 to S17 shown in FIG. 6) is performed.

[0102] In this way, before the inductance measurement starts, the magnitude of the first voltage vector command |V1 * By calculating |, it is possible to know the approximate value of the magnitude of the voltage vector command required for each current when the inductance is unknown, and the first voltage vector command V1 required to reach the target current I1 can be obtained. * It is possible to reduce the number of steps required for adjustment, and it is also possible to prevent an excessive current that may destroy the device from flowing.

[0103] In addition, the magnitude of the first voltage vector command |V1 *The calculation of | may be performed outside the voltage command generating unit 1. For example, a voltage command calculation unit may be separately provided, and the voltage command calculation unit may calculate the magnitude |V1 of the first voltage vector command. * | and output it to the voltage command generating unit 1.

[0104] Also, the magnitude of the first voltage vector command |V1 * After the calculation of |, the inductance is measured by the method described in the first embodiment, but the inductance may be measured by the method described in the second embodiment.

[0105] Embodiment 4 Next, a fourth embodiment will be described. The configuration of an inductance measuring device according to the fourth embodiment is similar to that of the first embodiment (see FIG. 1). In this embodiment, differences from the first embodiment will be described.

[0106] FIG. 12 is a flowchart showing an example of an inductance measuring operation of the inductance measuring device 10 according to the fourth embodiment.

[0107] 12, the inductance measuring device 10 according to the fourth embodiment first applies a fixing voltage to the d-axis (step S21). Specifically, the voltage command generating unit 1 generates a voltage command for commanding application of a fixing voltage to the d-axis and outputs the voltage command to the power converting unit 2. In accordance with the voltage command from the voltage command generating unit 1, the power converting unit 2 applies a DC voltage to the AC machine 11 as a fixing voltage in the d-axis direction at sufficiently long time intervals.

[0108] Next, the inductance measuring device 10 performs a reflux operation of the current of the AC machine 11 (step S22). Specifically, the gate voltage of the power module in the power conversion unit 2 is cut off to set the current flowing through the AC machine 11 to zero.

[0109] Next, the inductance measuring device 10 performs an operation of measuring the inductance of the AC machine 11 (step S23). In this step S23, the inductance of the AC machine 11 is measured by the method described in the first embodiment, that is, the method shown in steps S11 to S17 in Fig. 6. Note that the inductance may also be measured by the method described in the second embodiment.

[0110] Next, the inductance measuring device 10 performs a return operation of the current of the AC machine 11, similar to step S22, to set the current flowing through the AC machine 11 to zero (step S24). This return operation makes it possible to instantly set the current of the AC machine 11 to zero, and therefore it is possible to further suppress the vibration and noise of the drive unit of the AC machine 11.

[0111] Next, the inductance measuring device 10 applies a reverse voltage command (step S25). Specifically, the voltage command generating unit 1 generates a voltage vector command that commands a voltage in the reverse direction to that during inductance measurement, and outputs the voltage vector command to the power converting unit 2, and the power converting unit 2 applies the commanded voltage to the AC machine 11. The voltage vector command V inv * is V inv * =-V1 * -V2 * By this process, even if the vibration and noise of the shaft cannot be sufficiently suppressed by setting the current to zero during the return current operation, a driving force in the opposite direction to that during the inductance measurement is generated, thereby making it possible to further suppress the vibration and noise.

[0112] Next, the inductance measuring device 10 performs a reflux operation similar to steps S22 and S24 (step S26).

[0113] According to the above-described fourth embodiment, it is possible to further suppress vibration and noise of the AC machine 11, and to perform more accurate inductance measurement, as compared with the first to third embodiments.

[0114] 12, the processes other than step S23 may be selected as appropriate depending on the status of the AC machine 11 and the device connected to the AC machine 11. For example, steps S21 and S22 may be omitted if it is clear that the drive unit of the AC machine 11 is fixed before the measurement is started. Steps S24 to S26 may be omitted if the AC machine 11 is difficult to drive, for example, if the rotating shaft inertia is large in the case of a rotating machine, or if the mover mass is large in the case of a linear motor.

[0115] Embodiment 5. Next, a fifth embodiment will be described. The configuration of an inductance measuring device according to the fifth embodiment is similar to that of the first embodiment (see FIG. 1). In this embodiment, differences from the first embodiment will be described.

[0116] In the fifth embodiment, a case will be described in which only one of the d-axis inductance and the q-axis inductance is measured when current is applied to both the d-axis and q-axis by any of the methods described in the first to fourth embodiments. The fifth embodiment is different from the first to fourth embodiments in that the second voltage vector command V2 * Phase θ v2 * The setting method is different.

[0117] In the inductance measuring device 10 according to the fifth embodiment, when only the d-axis inductance is measured, θ v2 * If you set θ = 0[deg] and only measure the q-axis inductance, v2 * = 90[deg]. In other words, the current is changed only in the d-axis direction or only in the q-axis direction to measure the d-axis inductance or the q-axis inductance.

[0118] In the derivation of the above equations (5) and (6), the d-axis current change di d The change in q-axis magnetic flux due to q / di d , and q-axis current change di q The d-axis magnetic flux change due tod / di q The magnetic flux change due to interference between the d- and q-axes is assumed to be negligible, as it is much smaller than the magnetic flux change caused by current changes on the d- and q-axes themselves. However, for example, if you want to perform a more accurate inductance measurement to compare with the results of a magnetic field analysis, you can perform a more accurate inductance calculation by causing current changes only in the d-axis and only in the q-axis direction, thereby eliminating the effects of magnetic flux changes due to interference between the d- and q-axes.

[0119] Embodiment 6 Next, a sixth embodiment will be described. The configuration of an inductance measuring device according to the sixth embodiment is similar to that of the first embodiment (see FIG. 1). In this embodiment, differences from the first embodiment will be described.

[0120] In the inductance measuring device 10 according to the sixth embodiment, a first voltage vector command V1 generated by a voltage command generating unit 1 is * The size of |V1 * A plurality of values ​​|V1 can be set so that a current vector of a plurality of magnitudes ranging from 0 to the rated current of the AC machine 11 can be applied. * | and the first voltage vector command V1 * The phase of θ v1 * Then, multiple phases ranging from 0 to 90 deg are calculated as θ v1 * and set these |V1 * | and θ v1 * Inductance measurements are performed for all combinations of

[0121] That is, the voltage command generating unit 1 generates a voltage command |V1 * | and phase θ v1 * While changing the first voltage vector command V1 * The voltage command generating unit 1 repeatedly generates the second divided voltage vector command V2 according to the procedure described in the first embodiment and outputs the first divided voltage vector command to the power conversion unit 2.* The magnitude and phase of the first voltage vector command V1 generated by the voltage command generating unit 1 are fixed. * For each of these, the inductance is calculated using the method described in the first embodiment.

[0122] Then, the inductance calculation unit 4 calculates all I 1d and I 1q The inductance measurement results are tabulated to generate table data of inductance.

[0123] First voltage vector command V1 * The size of |V1 * |, a plurality of values ​​are set so that current vectors of a plurality of magnitudes ranging from 0 to the rated current of the AC machine 11 can be applied, and the phase θ v1 * Since multiple phases are set in the range of 0 to 90 degrees as the first voltage vector command V1, multiple first voltage vector commands V1 obtained from all combinations of these are * This covers all the voltage vectors that the AC machine 11 can take while it is driving. According to the sixth embodiment, it is possible to obtain table data that covers all the inductances that the AC machine 11 can take while it is driving.

[0124] The voltage command generating unit 1 may generate the first divided voltage vector command and the second divided voltage vector command in the procedure explained in the second embodiment.

[0125] Next, the hardware for realizing the inductance measuring device 10 described in the first to sixth embodiments will be described.

[0126] The power conversion unit 2 of the inductance measurement device 10 is realized by, for example, an inverter. The current detection unit 3 of the inductance measurement device 10 is realized by, for example, a current sensor.

[0127] Moreover, the voltage command generating unit 1, the inductance calculating unit 4 and the coordinate converting unit 5 of the inductance measuring device 10 are realized, for example, by a processor 91 and a memory 92 shown in Fig. 13. Note that Fig. 13 is a diagram showing an example of hardware for realizing the inductance measuring device 10 according to the first to sixth embodiments.

[0128] An example of the processor 91 is a CPU (also called a Central Processing Unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). An example of the memory 92 is a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), or a flash memory, a magnetic disk, etc.

[0129] The voltage command generating unit 1, inductance calculation unit 4, and coordinate conversion unit 5 of the inductance measuring device 10 described in each embodiment are realized by a processor 91 executing a program for implementing each of these units. The program for implementing the voltage command generating unit 1, inductance calculation unit 4, and coordinate conversion unit 5 of the inductance measuring device 10 is stored in advance in a memory 92. The processor 91 reads out and executes this program from the memory 92, thereby operating as the voltage command generating unit 1, inductance calculation unit 4, and coordinate conversion unit 5 of the inductance measuring device 10.

[0130] Although the voltage command generating unit 1, the inductance calculating unit 4, and the coordinate conversion unit 5 of the inductance measuring device 10 are realized by a general-purpose processor 91 and memory 92 in the above description, each of these units may be realized by a dedicated processing circuit. Examples of the dedicated processing circuit include a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), and an FPGA (Field Programmable Gate Array). Each unit of the inductance measuring device may be realized by combining two or more of these processing circuits. In addition, the voltage command generating unit 1, the inductance calculating unit 4, and the coordinate conversion unit 5 of the inductance measuring device 10 may be realized by combining the processor 91 and memory 92 shown in FIG. 13 with a dedicated processing circuit. For example, the voltage command generating unit 1 and the inductance calculating unit 4 may be realized by the processor 91 and memory 92, and the coordinate conversion unit 5 may be realized by a dedicated processing circuit.

[0131] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0132] 1 voltage command generation unit, 2 power conversion unit, 3 current detection unit, 4 inductance calculation unit, 5 coordinate conversion unit, 10 inductance measurement device, 11 AC machine.

Claims

1. a power conversion unit that applies a voltage to the AC machine; a voltage command generating unit that generates a voltage command for the power conversion unit; an inductance calculation unit that calculates an inductance of the AC machine based on a first current that flows through the AC machine when a first voltage is applied to the AC machine and a second current that flows through the AC machine when a second voltage is applied to the AC machine after the first voltage is applied; Equipped with the voltage command generation unit generates a first d-axis voltage command that commands a voltage on the d-axis of a rotating coordinate system and a first q-axis voltage command that commands a voltage on the q-axis, the first d-axis voltage command commanding a voltage on the d-axis of the rotating coordinate system being plural and the same in number, based on a first voltage command that commands the first voltage and a determined voltage division criterion, such that when a zero voltage command is included, the zero voltage command is executed before a non-zero voltage command; and further commands the power conversion unit to apply a voltage to the AC machine a plurality of times, based on the generated plurality of first d-axis voltage commands and first q-axis voltage commands. An inductance measuring device characterized by:

2. the voltage division reference is a first voltage division reference which is a voltage division reference on the same phase as the first voltage command, or a second voltage division reference which is a voltage division reference on the d-axis and q-axis of the rotating coordinate system; 2. The inductance measuring device according to claim 1 .

3. the voltage command generation unit divides the first voltage command into a plurality of first divided voltage commands having the same phase as the first voltage command based on the first voltage division criterion, and separates each of the plurality of first divided voltage commands into a d-axis component and a q-axis component to generate a plurality of the first d-axis voltage commands and the first q-axis voltage commands; 3. The inductance measuring device according to claim 2.

4. the voltage command generation unit generates a plurality of second d-axis voltage commands that command a voltage on the d-axis and a second q-axis voltage command that command a voltage on the q-axis, based on a second voltage command that commands the second voltage and the first voltage division criterion, and further commands the power conversion unit to apply a voltage to the AC machine a plurality of times, based on the generated plurality of second d-axis voltage commands and second q-axis voltage commands.

3. The inductance measuring device according to claim 2.

5. the voltage command generation unit divides the second voltage command into a plurality of second divided voltage commands having the same phase as the second voltage command based on the first voltage division criterion, and separates each of the plurality of second divided voltage commands into a d-axis component and a q-axis component to generate a plurality of second d-axis voltage commands and a plurality of second q-axis voltage commands; 5. The inductance measuring device according to claim 4.

6. the first voltage division reference is a rated voltage of a power converter constituting the power conversion unit; 3. The inductance measuring device according to claim 2.

7. the first voltage division reference is the rated voltage of the AC machine; 3. The inductance measuring device according to claim 2.

8. the voltage command generation unit separates the first voltage command into the d-axis component and the q-axis component, divides each of the d-axis component of the first voltage command and the q-axis component of the first voltage command based on the second voltage division criterion, and, when the number of the d-axis components of the first voltage command after division differs from the number of the q-axis components of the first voltage command after division, adds a 0 voltage command to the side with the smaller number, thereby generating the same number of the first d-axis voltage commands and the first q-axis voltage commands.

3. The inductance measuring device according to claim 2.

9. the voltage command generation unit generates a plurality of second d-axis voltage commands that command a voltage on the d-axis and a plurality of second q-axis voltage commands that command a voltage on the q-axis, based on a second voltage command that commands the second voltage and the second voltage division criterion, and further commands the power conversion unit to apply a voltage to the AC machine a plurality of times, based on the generated plurality of second d-axis voltage commands and second q-axis voltage commands.

9. The inductance measuring device according to claim 8.

10. the voltage command generation unit separates a second voltage command into the d-axis component and the q-axis component, divides each of the d-axis component of the second voltage command and the q-axis component of the second voltage command based on the second voltage division criterion, and, when the number of the d-axis components of the second voltage command after division differs from the number of the q-axis components of the second voltage command after division, adds a zero voltage command to the side with the smaller number to generate the same number of the second d-axis voltage commands and the second q-axis voltage commands, and further commands the power conversion unit to apply a voltage to the AC machine a plurality of times based on the generated plurality of second d-axis voltage commands and the second q-axis voltage commands.

10. The inductance measuring device according to claim 9.

11. the voltage command generation unit adds the zero voltage command so that the zero voltage command is executed first.

9. The inductance measuring device according to claim 8.

12. The second voltage division standard is set to 1 / √2 times the rated voltage of the power converter constituting the power conversion unit.

9. The inductance measuring device according to claim 8.

13. The second voltage division standard is 1 / √2 times the rated voltage of the AC machine.

9. The inductance measuring device according to claim 8.

14. The voltage command generation unit The magnitude of the current vector equivalent to the current flowing when the first voltage is applied to the AC machine is |I 1 |Tosi, The rated voltage of the AC machine is V r , rated current is I r , the field is φ f , rated frequency is f r , one control processing period is t s In this case, The magnitude of the first voltage command is calculated based on the following equations (1), (2), and (3):

14. An inductance measuring device according to claim 1. [Equation 1] [Equation 2] [Equation 3]

15. The voltage command generation unit outputting the first voltage command to the power conversion unit, and then outputting a reverse voltage command to the power conversion unit to command a voltage having the same magnitude as the first voltage but in the opposite direction, thereby suppressing generation of a driving force for the AC machine; 14. An inductance measuring device according to claim 1.

16. The voltage command generation unit before outputting the first voltage command to the power conversion unit, outputting a command to the power conversion unit to apply a constant DC voltage in the direction of the d-axis of the AC machine to fix the AC machine; 14. An inductance measuring device according to claim 1.

17. the inductance calculation unit calculates the inductance of either the d-axis or the q-axis, When the inductance calculation unit calculates the d-axis inductance, the voltage command generation unit generates the voltage command for setting a phase of a second voltage command that commands the second voltage to 0 deg and outputs the voltage command to the power conversion unit, and when the inductance calculation unit calculates the q-axis inductance, the voltage command generation unit generates the voltage command for setting a phase of the second voltage command to 90 deg and outputs the voltage command to the power conversion unit, and generates a current change in an axis for inductance calculation when a voltage applied to the AC machine changes from the first voltage to the second voltage.

14. An inductance measuring device according to claim 1.

18. the voltage command generation unit generates the first voltage command for controlling the power conversion unit so that a plurality of the first voltages, which differ in at least one of magnitude and phase within a range determined based on a rated current of the AC machine, are repeatedly applied to the AC machine; the inductance calculation unit calculates an inductance of the AC machine for each of the plurality of first voltages applied to the AC machine, and creates table data of inductance based on the calculation results.

14. An inductance measuring device according to claim 1.

19. An inductance measurement method executed by an inductance measurement device that includes a voltage command generation unit that generates a voltage command for a power conversion unit that applies a voltage to an AC machine, and that calculates an inductance of the AC machine based on a first current that flows through the AC machine when a first voltage is applied to the AC machine and a second current that flows through the AC machine when a second voltage is applied to the AC machine after the first voltage is applied, a first step in which the voltage command generation unit generates a first d-axis voltage command that commands a voltage on a d-axis of a rotating coordinate system and a first q-axis voltage command that commands a voltage on a q-axis of the rotating coordinate system based on a first voltage command that commands the first voltage and a determined voltage division criterion, the first d-axis voltage command and the first q-axis voltage command that commands a voltage on a q-axis of the rotating coordinate system being plural and equal in number, and in such a way that when a zero voltage command is included, the zero voltage command is executed before a non-zero voltage command; a second step in which the voltage command generating unit commands the power converting unit to apply a voltage to the AC machine a plurality of times based on the generated plurality of first d-axis voltage commands and the generated plurality of first q-axis voltage commands; An inductance measurement method comprising:

20. the voltage division reference is a first voltage division reference which is a voltage division reference on the same phase as the first voltage command, or a second voltage division reference which is a voltage division reference on the d-axis and q-axis of the rotating coordinate system; 20. The inductance measurement method according to claim 19.

21. In the first step, the first voltage command is divided into a plurality of first divided voltage commands having the same phase as the first voltage command based on the first voltage division criterion, and each of the plurality of first divided voltage commands is separated into a d-axis component and a q-axis component to generate a plurality of the first d-axis voltage commands and the first q-axis voltage commands.

21. The inductance measurement method according to claim 20.

22. In the first step, the first voltage command is separated into the d-axis component and the q-axis component, and each of the d-axis component of the first voltage command and the q-axis component of the first voltage command is divided based on the second voltage division criterion, and when the number of the d-axis components of the first voltage command after division differs from the number of the q-axis components of the first voltage command after division, a zero voltage command is added to the side with the smaller number, thereby generating the same number of the first d-axis voltage commands and the first q-axis voltage commands.

21. The inductance measurement method according to claim 20.

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