Power conversion device and power conversion method

Abstract

The present application provides a power conversion device and a power conversion method capable of easily implementing control based on an estimation result of high-reliability inductance. The power conversion device (2) includes: a check voltage application unit (115) that applies a check voltage, which varies in size according to the passage of time, from a power conversion circuit (10) to a motor; a limit control unit (116) that applies a limit voltage from the power conversion circuit (10) to the motor to limit rotation of the motor caused by the application of the check voltage; a curve generation unit (130) that generates an inductance curve indicating a relationship between a current and inductance of the motor based on a relationship between the check voltage and a check current flowing between the power conversion circuit (10) and the motor corresponding to the check voltage; an inductance estimation unit (119) that estimates the inductance based on the current flowing through the motor and the inductance curve; and a PWM control unit (114) that controls the power conversion circuit (10) based on an estimation result of the inductance.

Description

TECHNICAL FIELD

[0001] The present application relates to a power conversion device and a power conversion method. BACKGROUND

[0002] A control method is disclosed in Patent Literature 1, which controls an armature rotating magnetic field and a rotor speed of an IPM motor using an estimation signal of a rotor magnetic pole position and a rotor speed estimation signal obtained by an operation from an internal signal of a control device of the IPM motor.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent No. 4228651 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present application provides a power conversion device capable of easily performing control based on an estimation result of inductance with high reliability.

[0008] MEANS FOR SOLVING THE PROBLEMS

[0009] The power conversion device in one embodiment of the present application includes: a check voltage application section that applies a check voltage to a motor from a power conversion circuit, the check voltage varying in magnitude over time; a restriction control section that applies a restriction voltage to the motor from the power conversion circuit to restrict rotation of the motor caused by application of the check voltage; a curve generation section that generates an inductance curve representing a relationship between a current and an inductance of the motor, based on a relationship between the check voltage and a check current flowing between the power conversion circuit and the motor corresponding to the check voltage; an inductance estimation section that estimates the inductance based on the current flowing through the motor and the inductance curve; and a control section that controls the power conversion circuit based on an estimation result of the inductance.

[0010] The power conversion method in another embodiment of the present application includes: applying a check voltage to a motor from a power conversion circuit, the check voltage varying in magnitude over time; applying a restriction voltage to the motor from the power conversion circuit to restrict rotation of the motor caused by application of the check voltage; generating an inductance curve representing a relationship between a current and an inductance of the motor, based on a relationship between the check voltage and a check current flowing between the power conversion circuit and the motor corresponding to the check voltage; estimating the inductance based on the current flowing through the motor and the inductance curve; and controlling the power conversion circuit based on an estimation result of the inductance.

[0011] EFFECTS OF THE INVENTION

[0012] According to the present invention, it is possible to provide a power conversion device that can easily realize control based on a highly reliable inductance estimation result. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram illustrating a schematic configuration of a drive system.

[0014] Figure 2 This is a block diagram illustrating the configuration of the control circuit in more detail.

[0015] Figure 3 This is a block diagram illustrating the input and output of information when generating the first inductance curve.

[0016] Figure 4 This is a schematic diagram illustrating the principle of estimating the magnetic pole position when generating the first inductance curve.

[0017] Figure 5 is a graph illustrating a first inspection current and a first inspection voltage.

[0018] Figure 6 is a graph illustrating a first inspection current and a first inspection voltage.

[0019] Figure 7 is a graph illustrating a first inductance curve.

[0020] Figure 8 This is a block diagram illustrating the input and output of information when generating the second inductance curve.

[0021] Figure 9 This is a schematic diagram illustrating the principle of estimating the magnetic pole position when generating the second inductance curve.

[0022] Figure 10 is a graph illustrating the second inspection current and the second inspection voltage.

[0023] Figure 11 is a graph illustrating a second inductance curve.

[0024] Figure 12 This is a block diagram illustrating the hardware configuration of the control circuit.

[0025] Figure 13 is a flowchart illustrating a control process of the power conversion circuit.

[0026] Figure 14 is a flowchart illustrating a process of generating a first inductance curve.

[0027] Figure 15 is a flowchart illustrating a process of generating the second inductance curve. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments will be described in detail with reference to the drawings. In the description, the same elements or elements having the same function are denoted by the same reference symbols, and repeated description will be omitted.

[0029] (Drive system)

[0030] Figure 1 The illustrated drive system 1 is a system that drives a drive object by a motor 3. The drive system 1 has the motor 3 and a power conversion device 2. The motor 3 is a synchronous motor. The motor 3 can also be a synchronous motor having saliency. Having saliency means that inductance is different between coordinate axes of a rotating coordinate system. The rotating coordinate system is a coordinate system that rotates in synchronization with a magnetic pole position of the motor 3. As a specific example of the synchronous motor having saliency, an IPM (Interior Permanent Magnet) motor or a synchronous reluctance motor can be cited. The magnetic pole position of the IPM motor is, for example, a position of a magnetized pole formed by a permanent magnet embedded in an iron core. The magnetic pole position of the synchronous reluctance motor is, for example, a position of maximum inductance.

[0031] The power conversion device 2 converts primary-side electric power supplied from a power source 4 (for example, a power system) to secondary-side electric power and supplies it to the motor 3. The primary-side electric power can be direct-current electric power or alternating-current electric power. The secondary-side electric power is alternating-current electric power. Hereinafter, a structure of the power conversion device 2 will be exemplified in a case where the primary-side electric power and the secondary-side electric power are three-phase alternating-current electric power.

[0032] The power conversion device 2 has a power conversion circuit 10 and a control circuit 100. The power conversion circuit 10 converts the primary-side electric power to the secondary-side electric power and supplies it to the motor 3. As an example, the power conversion circuit 10 has a rectification circuit 11, an inverter circuit 15, and a current sensor 16.

[0033] The rectifier circuit 11 is, for example, a diode bridge circuit including a plurality of diodes 12, and converts the primary-side electric power into direct-current electric power to output to the direct-current bus 13P, 13N. The smoothing capacitor 14 smoothes the direct-current voltage in the direct-current bus 13P, 13N. The inverter circuit 15 performs the electric power conversion between the direct-current electric power and the secondary-side electric power. For example, the inverter circuit 15 converts the direct-current electric power into the secondary-side electric power to supply to the motor 3 in the motoring state, and converts the secondary-side electric power generated by the motor 3 into the direct-current electric power in the regeneration state. The inverter circuit 15 has, for example, a plurality of switching elements 17, and performs the electric power conversion by switching the on / off of the plurality of switching elements 17. The switching element 17 is, for example, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor), and switches the on / off according to a gate drive signal.

[0034] The current sensor 16 detects the current (hereinafter, referred to as "secondary-side current") flowing between the inverter circuit 15 and the motor 3. For example, the current sensor 16 can be configured to detect the current of all phases (U phase, V phase, and W phase) of the secondary-side electric power, or can be configured to detect the current of any two phases of the secondary-side electric power. As long as the zero-phase current is not generated, the sum of the currents of the U phase, the V phase, and the W phase is zero, and thus the information of the current of all phases can be obtained even in the case where the two-phase current is detected.

[0035] The configuration of the power conversion circuit 10 shown above is only an example. The configuration of the power conversion circuit 10 can be changed as follows as long as the primary-side electric power can be converted into the secondary-side electric power to be supplied to the motor 3. For example, the rectifier circuit 11 can be a PWM converter circuit that converts the alternating-current electric power into the direct-current electric power. The power conversion circuit 10 can be a matrix converter circuit that performs the bidirectional electric power conversion between the primary-side electric power and the secondary-side electric power without being direct-current. In the case where the power source electric power is the direct-current electric power, the power conversion circuit 10 can not have the rectifier circuit 11.

[0036] The control circuit 100 generates a control command for causing the motor 3 to perform a desired operation, and controls the power conversion circuit 10 to generate a secondary-side power that follows the control command. As a specific example of the desired operation, there can be mentioned generation of a torque corresponding to a target torque, rotation at a speed that follows a target speed, and the like. If the power conversion circuit 10 is of the voltage type, the control command contains at least a voltage command, and if the power conversion circuit 10 is of the current type, the control command contains at least a current command. In the case where the power conversion circuit 10 is of the voltage type, the control circuit 100 controls the power conversion circuit 10 in such a manner that a secondary-side voltage corresponding to the voltage command is applied to the motor 3. In the case where the power conversion circuit 10 is of the current type, the control circuit 100 controls the power conversion circuit 10 in such a manner that a secondary-side current corresponding to the current command is caused to flow to the motor 3.

[0037] For example, the control circuit 100 has a drive control section 111, a current information acquisition section 112, a magnetic pole position estimation section 113, and a PWM control section 114 as functional structures (functional blocks). The drive control section 111 generates a voltage command for causing the motor 3 to perform a desired operation. For example, the drive control section 111 generates a voltage command in a rotating coordinate system that rotates in synchronization with the magnetic poles of the rotor of the motor 3. As a specific example of the rotating coordinate system, there can be mentioned, for example, a γδ coordinate system that has a center of rotation of the rotor of the motor 3 as an origin. The γδ coordinate system has, for example, a γ axis that is a direction that follows the magnetic pole position of the rotor of the motor 3, and a δ axis that is perpendicular to the γ axis. The magnetic pole position is represented by, for example, a rotation angle (electric angle) of the magnetic pole in a fixed coordinate system that is fixed to the stator of the motor 3. For example, the drive control section 111 generates a γ-axis voltage command Vγ_ref and a δ-axis voltage command Vδ_ref. The γ-axis voltage command Vγ_ref is a γ-axis component of a voltage command vector that represents the voltage command. The δ-axis voltage command Vδ_ref is a δ-axis component of the above-mentioned voltage command vector.

[0038] The current information acquisition section 112 acquires information of the secondary-side current on the basis of the detection result of the current sensor 16. For example, the current information acquisition section 112 calculates a γ-axis current iγ and a δ-axis current iδ in the γδ coordinate system on the basis of the U-phase current iu, the V-phase current iv, and the W-phase current iw detected by the current sensor 16. The γ-axis current iγ is a γ-axis component of a current vector that represents the secondary-side current. The δ-axis current iδ is a δ-axis component of the above-mentioned current vector. For example, the current information acquisition section 112 calculates the current vector in the fixed coordinate system by performing three-phase two-phase conversion on the U-phase current iu, the V-phase current iv, and the W-phase current iw, performs coordinate conversion on the current vector in the fixed coordinate system on the basis of the above-mentioned magnetic pole position (including an estimated value of the magnetic pole position), and calculates the γ-axis current iγ and the δ-axis current iδ.

[0039] The magnetic pole position estimation section 113 estimates the magnetic pole position θ of the motor 3 on the basis of the secondary-side voltage and the secondary-side current. For example, the magnetic pole position estimation section 113 estimates the position of the magnetic pole of the motor 3 on the basis of the γ-axis voltage command Vγ_ref, the δ-axis voltage command Vδ_ref, the γ-axis current iγ, and the δ-axis current iδ. For example, the magnetic pole position estimation section 113 calculates an induced voltage vector on the basis of the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref, the γ-axis current iγ and the δ-axis current iδ, the winding resistance R of the motor 3, the first inductance Lγ of the motor 3, and the second inductance Lδ of the motor 3, and estimates the position of the magnetic pole of the motor 3 on the basis of the direction of the induced voltage vector. The first inductance Lγ is a proportional constant of the γ-axis magnetic flux (magnetic flux generated in the γ-axis direction by the γ-axis current iγ) with respect to the γ-axis current iγ. The second inductance Lδ is a proportional constant of the δ-axis magnetic flux (magnetic flux generated in the δ-axis direction by the δ-axis current iδ) with respect to the δ-axis current iδ.

[0040] The PWM control section 114 controls the power conversion circuit 10 so that the secondary-side voltage corresponding to the voltage command calculated by the drive control section 111 is applied to the motor 3. For example, the PWM control section 114 calculates a voltage command vector in a fixed coordinate system on the basis of the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref calculated by the drive control section 111 and the magnetic pole position θ estimated by the magnetic pole position estimation section 113, performs two-phase / three-phase conversion on the voltage command vector in the fixed coordinate system, and calculates voltage commands for each phase of the U phase, the V phase, and the W phase. The PWM control section 114 switches the on / off of the plurality of switching elements 17 so as to apply a voltage corresponding to the voltage command of the U phase to the U phase of the motor 3, apply a voltage corresponding to the voltage command of the V phase to the V phase of the motor 3, and apply a voltage corresponding to the voltage command of the W phase to the W phase of the motor 3. In addition, the estimation result of the magnetic pole position θ of the magnetic pole position estimation section 113 is used for the calculation of the γ-axis current iγ and the δ-axis current iδ of the current information acquisition section 112 described above.

[0041] As exemplified above, when the power conversion circuit 10 is controlled so that the motor 3 performs a desired operation, an operation based on the winding resistance and the inductance of the motor 3 and the like is performed. In order to perform appropriate control, it is required to use a value with high reliability with respect to the winding resistance and the inductance of the motor 3. In particular, the inductance of the motor 3 changes due to saturation of the magnetic flux. Therefore, unless an operation considering the change in the inductance due to saturation of the magnetic flux is performed, it is likely that the stability of the operation of the motor 3 is reduced due to an error in the operation result.

[0042] To perform the operation taking into account the inductance variation caused by the saturation of the magnetic flux, the inductance corresponding to the current flowing at present is calculated at all times, taking into account the inductance curve representing the relationship between the secondary-side current (the current flowing between the power conversion circuit 10 and the motor 3) and the inductance. If individual differences of the motor 3 are also taken into account, it is desirable to generate and store appropriate inductance curves in advance for each motor 3, but it is not easy to generate and store the inductance curves.

[0043] To generate the inductance curve, it is necessary to calculate the inductance based on the relationship between the secondary-side current and the secondary-side voltage while changing the magnitude of the secondary-side current in a fixed direction with respect to the rotor of the motor 3. When the rotor of the motor 3 rotates due to the supply of the secondary-side current, the direction of the secondary-side current changes with respect to the rotor, and thus the secondary-side current cannot be continuously supplied in the above-described fixed direction. Therefore, it is required to supply the secondary-side current and the like in a state where the rotor of the motor 3 is fixed, and to perform the test under a condition different from the usual operation.

[0044] The control circuit 100 is configured to perform: application of a check voltage, which changes in magnitude over time, from the power conversion circuit 10 to the motor 3; application of a restriction voltage from the power conversion circuit 10 to the motor 3 to restrict the rotation of the motor 3 caused by the application of the check voltage; generation of an inductance curve representing the relationship between the current and the inductance of the motor 3, based on the relationship between the check voltage and a check current flowing between the power conversion circuit 10 and the motor 3 in correspondence with the check voltage; estimation of the inductance based on the current flowing through the motor 3 and the inductance curve; and control of the power conversion circuit 10 based on the estimation result of the inductance.

[0045] According to this structure, since the rotation of the motor 3 caused by the application of the check voltage is restricted by the applied restriction voltage, it is possible to easily change the check voltage and generate the inductance curve for a wide range of current having a wide amplitude. Therefore, it is possible to estimate the inductance with high reliability in a wide range of current having a wide amplitude. Thus, it is possible to easily achieve control based on the estimation result of the inductance with high reliability.

[0046] For example, as Figure 2As shown, the control circuit 100 also has, as functional blocks, a check voltage application section 115, a magnetic pole position estimation section 120, a restriction control section 116, a curve generation section 130, a curve storage section 118, and an inductance estimation section 119. The check voltage application section 115 applies a check voltage, whose magnitude changes according to the passage of time, from the power conversion circuit 10 to the motor 3. The check voltage can contain at least an alternating component. In this case, the check voltage application section 115 can also cause the amplitude of the check voltage to change according to the passage of time as the magnitude of the check voltage. The check voltage can contain an alternating component and a direct component. In this case, the check voltage application section 115 can also cause the magnitude of the direct component to change according to the passage of time as the magnitude of the check voltage.

[0047] For example, the check voltage application section 115 generates a voltage command for applying the check voltage, and outputs it to the PWM control section 114.

[0048] The magnetic pole position estimation section 120 estimates the magnetic pole position θ of the motor 3. The magnetic pole position estimation section 113 described above estimates the magnetic pole position θ based on the inductance of the motor 3. In contrast, the magnetic pole position estimation section 120 estimates the magnetic pole position θ by a method that is not based on the inductance of the motor 3. For example, the magnetic pole position estimation section 120 applies an alternating search voltage from the power conversion circuit 10 to the motor 3, and estimates the magnetic pole position θ from a search current that flows between the power conversion circuit 10 and the motor 3 in correspondence with the search voltage. The search voltage can be, for example, a high-frequency voltage of a frequency higher than the frequency that the motor 3 can follow. The magnetic pole position estimation section 120 generates a voltage command for applying the search voltage, and outputs it to the PWM control section 114.

[0049] The restriction control section 116 applies a restriction voltage from the power conversion circuit 10 to the motor 3, in order to restrict the rotation of the motor 3 caused by the application of the check voltage. For example, the restriction control section 116 calculates a voltage command corresponding to a restriction voltage required in the γδ coordinate system, in order to maintain the rotational speed of the motor 3 at zero, and outputs it to the PWM control section 114.

[0050] The PWM control section 114 controls the power conversion circuit 10 so that a secondary-side voltage corresponding to the voltage command calculated by the check voltage application section 115, the magnetic pole position estimation section 120, and the limit control section 116 is applied to the motor 3. For example, the PWM control section 114 calculates a voltage command vector in a fixed coordinate system based on the limit voltage calculated by the limit control section 116 and the magnetic pole position θ estimated by the magnetic pole position estimation section 120, performs two-phase / three-phase conversion on the voltage command vector in the fixed coordinate system, and calculates voltage commands for each phase of the U phase, the V phase, and the W phase. The PWM control section 114 switches the on / off of the plurality of switching elements 17 so as to apply a voltage corresponding to the voltage command of the U phase to the U phase of the motor 3, apply a voltage corresponding to the voltage command of the V phase to the V phase of the motor 3, and apply a voltage corresponding to the voltage command of the W phase to the W phase of the motor 3.

[0051] The curve generation section 130 generates an inductance curve indicating a relationship between a current and an inductance of the motor 3 based on a relationship between a check voltage and a check current flowing between the power conversion circuit 10 and the motor 3 in correspondence with the check voltage. For example, the curve generation section 130 calculates an inductance based on the check voltage and the check current in accordance with the magnitude of the check voltage varied by the check voltage application section 115 over time, and stores the inductance in association with the magnitude of the check current in the curve storage section 118. Thereby, the inductance curve is stored in the curve storage section 118.

[0052] In a case where the check voltage application section 115 varies the amplitude of the check voltage over time, the curve generation section 130 associates the inductance with the amplitude of the check current. In a case where the check voltage application section 115 varies the magnitude of the above-described direct current component over time, the curve generation section 130 can also associate the inductance with the magnitude of the direct current component of the check current.

[0053] The inductance estimation section 119 estimates the inductance of the motor 3 based on the current flowing through the motor 3 and the inductance curve stored in the curve storage section 118 after the inductance curve is stored in the curve storage section 118.

[0054] The magnetic pole position estimation section 113 performs the above-described estimation of the magnetic pole position θ based on the estimation result of the inductance estimated by the inductance estimation section 119. Therefore, the PWM control section 114 (control section) controls the power conversion circuit 10 based on the estimation result of the inductance by the inductance estimation section 119. The magnetic pole position estimation section 113 can also calculate the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref based on the estimation result of the inductance by the inductance estimation section 119 in addition to performing the estimation of the magnetic pole position θ based on the estimation result of the inductance by the inductance estimation section 119.

[0055] The inspection voltage application section 115 can also apply a first inspection voltage that varies in size over time from the power conversion circuit 10 to the motor 3 along a first coordinate axis in the rotational coordinate system of the motor 3. In addition, the voltage along the first coordinate axis refers to a voltage applied in the same direction as the current that generates a magnetic field along the first coordinate axis, represented by a vector along the first coordinate axis.

[0056] In the case where the inspection voltage application section 115 applies the first inspection voltage along the first coordinate axis from the power conversion circuit 10 to the motor 3, the restriction control section 116 can also apply a first restriction voltage along a second coordinate axis perpendicular to the first coordinate axis from the power conversion circuit 10 to the motor 3 to restrict rotation of the motor 3 caused by application of the first inspection voltage. The curve generation section 130 can also generate a first inductance curve representing the relationship between the current along the first coordinate axis and the inductance based on the relationship between the first inspection voltage and the first inspection current flowing between the power conversion circuit 10 and the motor 3. The inductance estimation section 119 can also estimate a first inductance corresponding to the first coordinate axis based on the current along the first coordinate axis and the first inductance curve.

[0057] The pole position estimation section 113 can also perform the above-described estimation of the pole position θ based on the estimation result of the first inductance by the inductance estimation section 119. In this case, the PWM control section 114 (control section) controls the power conversion circuit 10 based on the estimation result of the first inductance by the inductance estimation section 119. The pole position estimation section 113, in addition to performing the estimation of the pole position θ based on the estimation result of the first inductance by the inductance estimation section 119, can also calculate the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref based on the estimation result of the first inductance by the inductance estimation section 119.

[0058] The relationship between the current along the first coordinate axis and the inductance represents the relationship between the current along the first coordinate axis and the inductance of the first coordinate axis. The current along the first coordinate axis refers to the current that generates a magnetic field along the first coordinate axis. The inductance of the first coordinate axis is a proportional constant of the magnetic flux along the first coordinate axis with respect to the current along the first coordinate axis.

[0059] The inspection voltage application section 115 can also apply the first inspection voltage from the power conversion circuit 10 to the motor 3 with the direction of the γ-axis as the first coordinate axis, which aims to follow the direction through the pole position θ. For example, the inspection voltage application section 115 calculates the first inspection voltage in the γδ coordinate system in such a way as to be along the γ-axis and outputs it to the PWM control section 114. In this case, the restriction control section 116 calculates the first restriction voltage in the γδ coordinate system in such a way as to be along the δ-axis and outputs it to the PWM control section 114.

[0060] For example, the PWM control section 114 calculates a voltage command vector in the fixed coordinate system based on the first check voltage calculated by the check voltage application section 115, the first limit voltage calculated by the limit control section 116, and the magnetic pole position Θ estimated by the magnetic pole position estimation section 120, performs two-phase / three-phase conversion on the voltage command vector in the fixed coordinate system, and calculates voltage commands for each phase of the U phase, the V phase, and the W phase. The PWM control section 114 switches the on / off of the plurality of switching elements 17 so as to apply a voltage corresponding to the voltage command of the U phase to the U phase of the motor 3, apply a voltage corresponding to the voltage command of the V phase to the V phase of the motor 3, and apply a voltage corresponding to the voltage command of the W phase to the W phase of the motor 3.

[0061] Figure 3 is a block diagram illustrating the input and output of information when generating the first inductance curve. The check voltage application section 115 applies a first check voltage including an alternating voltage and a direct voltage whose magnitude changes over time from the power conversion circuit 10 to the motor 3.

[0062] For example, the check voltage application section 115 calculates the first direct voltage Vdc1 based on the deviation of the first direct current idc1 that increases over time and the γ-axis current iγ calculated by the current information acquisition section 112. The first direct voltage Vdc1 also increases over time in correspondence with the first direct current idc1 increasing over time. The check voltage application section 115 applies a first check voltage including the first search voltage Vinj1 generated by the magnetic pole position estimation section 120 and the first direct voltage Vdc1 from the power conversion circuit 10 to the motor 3. For example, the check voltage application section 115 adds the first search voltage Vinj1 and the first direct voltage Vdc1 to calculate a first check voltage V11 along the γ-axis. The check voltage application section 115 outputs the first check voltage V11 as a γ-axis voltage command Vγ_ref to the PWM control section 114.

[0063] The check voltage application section 115 calculates the first direct voltage Vdc1 using, for example, proportional operation, integral operation, proportional / integral operation, proportional / integral / differential operation, integral-proportional (I-P) operation, or the like using the deviation of the first direct current idc1 and the γ-axis current iγ.

[0064] The limit control section 116 calculates a first limit current i12 based on the deviation of zero and the rotational angular frequency ω of the rotor of the motor 3, and calculates a first limit voltage V12 along the δ-axis based on the deviation of the first limit current i12 and the δ-axis current iδ calculated by the current information acquisition section 112. The limit control section 116 outputs the first limit voltage V12 as a δ-axis voltage command Vδ_ref to the PWM control section 114.

[0065] The limit control section 116 calculates the first limit current i12, for example, using proportional operation, integral operation, proportional / integral operation, proportional / integral / derivative operation, integral-proportional (I-P) operation, and the like using the deviation of zero and the rotational angle frequency ω. The limit control section 116 calculates the first limit voltage V12, for example, using proportional operation, integral operation, proportional / integral operation, proportional / integral / derivative operation, integral-proportional (I-P) operation, and the like using the deviation of the first limit current i12 and the δ-axis current iδ.

[0066] The pole position estimation section 120 applies an alternating-current first search voltage from the power conversion circuit 10 to the motor 3, and estimates the pole position based on a first search current that flows between the power conversion circuit 10 and the motor 3 in correspondence with the first search voltage. The pole position estimation section 120 can also apply the first search voltage Vinj1 along the γ-axis to the motor 3 from the power conversion circuit 10 as the first check voltage V11, and estimate the pole position based on the direction in which the magnitude of the first search current becomes maximum or minimum. For example, the pole position estimation section 120 includes a search voltage superimposition section 121, a coordinate conversion section 122, and search current extraction sections 123 and 124.

[0067] The search voltage superimposition section 121 outputs the first search voltage Vinj1 to the check voltage application section 115. Accordingly, as described above, the check voltage application section 115 adds the first search voltage Vinj1 and the first direct-current voltage Vdc1 to calculate the first check voltage V11. Thus, the first search voltage Vinj1 is included in the first check voltage V11.

[0068] The coordinate conversion section 122 performs conversion of the γ-axis current iγ and the δ-axis current iδ calculated by the current information acquisition section 112 to a coordinate system in which the γδ coordinate system is rotated by -45°, and calculates currents iγ11 and iγ12. The current iγ11 is a component in the current that flows between the power conversion circuit 10 and the motor 3 by application of the first check voltage V11, in a direction that is +45° with respect to the γ-axis. The current iγ12 is a component in the current that flows between the power conversion circuit 10 and the motor 3 by application of the first check voltage V11, in a direction that is -45° with respect to the γ-axis.

[0069] The search current extraction section 123 extracts the first search current ih11, which is a component of the current iγ11 that corresponds to the first search voltage Vinj1, by band-pass filter processing or the like, and calculates the amplitude thereof. The search current extraction section 123 extracts the first search current ih12, which is a component of the current iγ12 that corresponds to the first search voltage Vinj1, by band-pass filter processing or the like, and calculates the amplitude thereof.

[0070] The pole position estimation unit 120 calculates the rotational angular frequency ω of the γ-axis in a manner that reduces the deviation of the amplitude of the first search current ihl 1 from the amplitude of the first search current ihl 2, and calculates the pole position θ by integrating the rotational angular frequency ω. For example, the pole position estimation unit 120 calculates the rotational angular frequency ω by using an integral operation, a proportional / integral operation, a proportional / integral / differential operation, an integral-proportional (I-P) operation, or the like of the deviation of the amplitude of the first search current ihl 1 from the amplitude of the first search current ihl 2.

[0071] When the γ-axis passes through the pole position, the value of the inductance changes linearly with respect to the direction of the pole position, and thus the deviation of the amplitude of the first search current ihl 1 from the amplitude of the first search current ihl 2 is zero, and the magnitude of the first search current ihl 0, which is the resultant of the first search current ihl 1 and the first search current ihl 2, becomes maximum or minimum. When the γ-axis deviates from the pole position, a difference is generated between the amplitude of the first search current ihl 1 and the amplitude of the first search current ihl 2. Figure 4 is a schematic diagram illustrating the principle of estimation of the pole position when generating the first inductance curve. In Figure 4 , the d-axis is a coordinate axis that passes through the pole position, and the q-axis is a coordinate axis that is perpendicular to the d-axis at an electrical angle. For example, as shown in Figure 4 (a), when the γ-axis deviates from the pole position (d-axis) in the positive direction (direction toward the q-axis), if the inductance Ld of the d-axis is smaller than the inductance Lq of the q-axis, the amplitude of the first search current ihl 2 is larger than the amplitude of the first search current ihl 1. By calculating the rotational angular frequency ω of the γ-axis in a manner that reduces the deviation of the amplitude of the first search current ihl 1 from the amplitude of the first search current ihl 2, the position of the γ-axis calculated by integrating the rotational angular frequency ω approaches the position of the d-axis that passes through the pole position.

[0072] As shown in Figure 4 (b), when the γ-axis coincides with the d-axis, the amplitude of the first search current ihl 1 is equal to the amplitude of the first search current ihl 2. In this state, the rotational angular frequency ω of the γ-axis becomes an estimation result of the rotational angular frequency ω of the pole, and the integral result of the rotational angular frequency ω becomes an estimation result of the pole position θ.

[0073] Returning to Figure 3The PWM control section 114 calculates a voltage command vector in the fixed coordinate system based on the γ-axis voltage command Vγ_ref output by the check voltage application section 115, the δ-axis voltage command Vδ_ref output by the limit control section 116, and the magnetic pole position θ estimated by the magnetic pole position estimation section 120, performs two-phase / three-phase conversion on the voltage command vector in the fixed coordinate system, and calculates voltage commands for each phase of the U phase, the V phase, and the W phase. The PWM control section 114 switches the on / off of the plurality of switching elements 17 so as to apply a voltage corresponding to the voltage command of the U phase to the U phase of the motor 3, a voltage corresponding to the voltage command of the V phase to the V phase of the motor 3, and a voltage corresponding to the voltage command of the W phase to the W phase of the motor 3.

[0074] The curve generation section 130 generates a first inductance curve PLγ that represents the relationship between the current along the γ-axis (first coordinate axis) and the inductance, based on the relationship between the first check voltage V11 and the first check current i11 (refer to FIG. 10B) that flows between the power conversion circuit 10 and the motor 3 in correspondence with the first check voltage V11. Figure 4 For example, the curve generation section 130 generates the first inductance curve PLγ based on the relationship between the first check voltage V11 that includes the above-described first search voltage Vinj1 and the first check current i11 that includes the first search current ih10.

[0075] For example, the curve generation section 130 has an inductance calculation section 131 and a correlation processing section 132. The inductance calculation section 131 calculates the first inductance Lγ based on the search voltage amplitude Vh1 that is the amplitude of the first search voltage Vinj1, the amplitude of the first search current ih10, and the frequency fh1 of the first search voltage. As described above, the first inductance Lγ calculated in the state where the γ-axis coincides with the d-axis corresponds to the inductance Ld of the d-axis. The correlation processing section 132 stores the first inductance Lγ and the first direct current idc1 that corresponds to the magnitude of the first check current i11 in correlation in the curve storage section 118. By storing the record of the correlation between the first inductance Lγ and the first direct current idc1 in the curve storage section 118 in accordance with the value of the first direct current idc1 that increases as time elapses, the first inductance curve PLγ is saved in the curve storage section 118.

[0076] The check voltage application section 115 can also increase the first direct current idc1 as time elapses for both the positive direction and the negative direction. Figure 5 is a graph that illustrates the first check current and the first check voltage in the case where the first direct current idc1 increases in the positive direction as time elapses. Figure 5 The horizontal axis of (a) of indicates the elapse of time, and the vertical axis indicates the instantaneous value of the first check current. Figure 5The horizontal axis of (b) of FIG. 10 indicates the passage of time, and the vertical axis indicates the instantaneous value of the first inspection voltage. Figure 5 (b) of FIG. 10 indicates the time variation of the first inspection voltage V11 including the first direct current voltage Vdcl and the first search voltage Vinjl that increase in the positive direction with the passage of time. Figure 5 (a) of FIG. 10 indicates the time variation of the first inspection current i11 corresponding to the time variation of the first inspection voltage V11. As the first direct current idcl becomes larger in the negative direction, the amplitude of the first search current ih10 corresponding to the first search voltage Vinjl becomes smaller.

[0077] Figure 6 is a graph that illustrates the first inspection current and the first inspection voltage in the case where the first direct current idcl becomes larger in the negative direction with the passage of time. Figure 6 The horizontal axis of (a) of FIG. 10 indicates the passage of time, and the vertical axis indicates the instantaneous value of the first inspection current. Figure 6 The horizontal axis of (b) of FIG. 10 indicates the passage of time, and the vertical axis indicates the instantaneous value of the first inspection voltage. Figure 6 (b) of FIG. 10 indicates the time variation of the first inspection voltage V11 including the first direct current voltage Vdcl and the first search voltage Vinjl that increase in the positive direction with the passage of time. Figure 6 (a) of FIG. 10 indicates the time variation of the first inspection current i11 corresponding to the time variation of the first inspection voltage V11. As the first direct current idcl becomes larger in the negative direction, the amplitude of the first search current ih10 corresponding to the first search voltage Vinjl becomes smaller.

[0078] Figure 7 is a graph that illustrates the first inspection voltage and the first inspection current based on Figure 5 and Figure 6 indicated in FIG. 10. Figure 7 The horizontal axis of FIG. 11 indicates the magnitude of the first inspection current. According to the first inspection voltage and the first inspection current indicated in Figure 5 and Figure 6 indicated in FIG. 10, a first inductance curve PLy is generated in which the first inductance Ly becomes larger as the first direct current idcl increases in the negative direction, and the first inductance Ly becomes smaller as the first direct current idcl increases in the positive direction. After the first inductance curve PLy is stored in the curve storage section 118, the inductance estimation section 119 estimates the first inductance Ly based on the y-axis current iy calculated by the current information acquisition section 112 and the first inductance curve PLy.

[0079] The inspection voltage application unit 115 can also apply a second inspection voltage along the second coordinate axis from the power conversion circuit 10 to the motor 3 during a period different from the period during which the first inspection voltage is applied to the motor 3. In this case, the limit control unit 116 can also apply a second limit voltage along the first coordinate axis from the power conversion circuit 10 to the motor 3 to limit rotation of the motor 3 caused by application of the second inspection voltage. The curve generation unit 130 can also further generate a second inductance curve representing a relationship between current along the second coordinate axis and inductance, based on a relationship between the second inspection voltage and a second inspection current flowing between the power conversion circuit 10 and the motor 3 in correspondence with the second inspection voltage. The inductance estimation unit 119 can also further estimate a second inductance corresponding to the second coordinate axis, based on current along the second coordinate axis and the second inductance curve.

[0080] The pole position estimation unit 113 can also perform the above-described estimation of the pole position θ based on the estimation results of the first inductance and the second inductance by the inductance estimation unit 119. In this case, the PWM control unit 114 (control unit) controls the power conversion circuit 10 based on the estimation results of the first inductance and the second inductance by the inductance estimation unit 119. The pole position estimation unit 113 can also calculate the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref based on the estimation results of the first inductance and the second inductance by the inductance estimation unit 119, in addition to performing the estimation of the pole position θ based on the estimation results of the first inductance and the second inductance by the inductance estimation unit 119.

[0081] During the period during which the first inspection voltage is applied to the motor 3, the pole position estimation unit 120 can also apply a first search voltage along the first coordinate axis to the motor 3 from the power conversion circuit 10 by including the first search voltage in the first inspection voltage as described above, and estimate the pole position based on a first search current flowing between the power conversion circuit 10 and the motor 3 in correspondence with the first search voltage. The curve generation unit 130 can also generate the first inductance curve based on a relationship between the first inspection voltage including the first search voltage and the first inspection current including the first search current.

[0082] During the period during which the second inspection voltage is applied to the motor 3, the pole position estimation unit 120 can also apply a second search voltage along the second coordinate axis to the motor 3 from the power conversion circuit 10 by including the second search voltage in the second inspection voltage, and estimate the pole position based on a second search current flowing between the power conversion circuit 10 and the motor 3 in correspondence with the second search voltage. The curve generation unit 130 can also generate the second inductance curve based on a relationship between the second inspection voltage including the second search voltage and the second inspection current including the second search current.

[0083] Figure 8is a block diagram illustrating input and output of information at the time of generating the second inductance curve. The inspection voltage application section 115 applies a second inspection voltage including an alternating voltage and a direct voltage whose magnitude changes over time from the power conversion circuit 10 to the motor 3.

[0084] For example, the inspection voltage application section 115 calculates the second direct voltage Vdc2 based on a deviation between the second direct current idc2 that increases over time and the δ-axis current iδ calculated by the current information acquisition section 112. In correspondence with a case where the second direct current idc2 increases over time, the second direct voltage Vdc2 also increases over time. The inspection voltage application section 115 applies the second inspection voltage including the second search voltage Vinj2 generated by the magnetic pole position estimation section 120 and the second direct voltage Vdc2 from the power conversion circuit 10 to the motor 3. For example, the inspection voltage application section 115 adds the second search voltage Vinj2 and the second direct voltage Vdc2 to calculate the second inspection voltage V22 along the δ-axis. The inspection voltage application section 115 outputs the second inspection voltage V22 to the PWM control section 114 as a δ-axis voltage command Vδ_ref.

[0085] The inspection voltage application section 115 can calculate the second direct voltage Vdc2 using, for example, proportional operation, integral operation, proportional / integral operation, proportional / integral / differential operation, integral-proportional (I-P) operation, or the like on the deviation between the second direct current idc2 and the δ-axis current iδ to calculate the second direct voltage Vdc2 using proportional operation on the deviation between the second direct current idc2 and the δ-axis current iδ.

[0086] The limit control section 116 calculates the second limit current i21 based on a deviation between zero and the rotational angular frequency ω of the rotor of the motor 3, and calculates the second limit voltage V21 along the γ-axis based on a deviation between the second limit current i21 and the γ-axis current iγ calculated by the current information acquisition section 112. The limit control section 116 outputs the second limit voltage V21 to the PWM control section 114 as a γ-axis voltage command Vγ_ref.

[0087] The limit control section 116 calculates the second limit current i21 using, for example, proportional operation, integral operation, proportional / integral operation, proportional / integral / differential operation, integral-proportional (I-P) operation, or the like on the deviation between zero and the rotational angular frequency ω. The limit control section 116 calculates the second limit voltage V21 using, for example, proportional operation, integral operation, proportional / integral operation, proportional / integral / differential operation, integral-proportional (I-P) operation, or the like on the deviation between the second limit current i21 and the γ-axis current iγ.

[0088] The pole position estimation section 120 applies an alternating-current second search voltage from the power conversion circuit 10 to the motor 3, and estimates the pole position based on a second search current that flows between the power conversion circuit 10 and the motor 3 in correspondence with the second search voltage. The pole position estimation section 120 can also apply the second search voltage Vinj2 along the δ-axis to the motor 3 from the power conversion circuit 10 as the second check voltage V22, and estimate the pole position based on the direction in which the magnitude of the second search current becomes maximum or minimum.

[0089] For example, the search voltage superimposition section 121 outputs the second search voltage Vinj2 to the check voltage application section 115. In correspondence therewith, as described above, the check voltage application section 115 adds the second search voltage Vinj2 to the second direct-current voltage Vdc2 to calculate the second check voltage V22. Thus, the second search voltage Vinj2 is included in the second check voltage V22.

[0090] The coordinate conversion section 122 performs conversion of the γ-axis current iγ and the δ-axis current iδ calculated by the current information acquisition section 112 to a coordinate system in which the γδ coordinate system is rotated by +45°, and calculates a current iδ21 and a current iδ22. The current iδ21 is a component in the current that flows between the power conversion circuit 10 and the motor 3 by application of the second check voltage V22, in a direction that is -45° with respect to the δ-axis. The current iδ22 is a component in the current that flows between the power conversion circuit 10 and the motor 3 by application of the second check voltage V22, in a direction that is +45° with respect to the δ-axis. In addition, the direction that is -45° with respect to the δ-axis corresponds to a direction that is +45° with respect to the γ-axis. In addition, the direction that is +45° with respect to the δ-axis corresponds to a direction that is -45° with respect to the γ-axis in reverse. Therefore, as in the case of calculating iγ11 and iγ12 described above, conversion to a coordinate system in which the γδ coordinate system is rotated by -45° can also be performed, and instead of the currents iδ21 and iδ22, a current iδ11 (component in the -45° direction with respect to the γ-axis) and a current iδ12 (component in the +45° direction with respect to the γ-axis) can be calculated, and the operations described later based on the currents iδ21 and iδ22 can be performed based on the currents iδ11 and iδ12.

[0091] The search current extraction section 123 extracts a second search current ih21 that is a component in the current iδ21 that corresponds to the second search voltage Vinj2 by band-pass filter processing or the like, and calculates the amplitude thereof. The search current extraction section 123 extracts a second search current ih22 that is a component in the current iδ22 that corresponds to the second search voltage Vinj2 by band-pass filter processing or the like, and calculates the amplitude thereof.

[0092] The pole position estimation section 120 calculates the rotational angular frequency ω of the γ axis in a manner that reduces the deviation of the amplitude of the second search current ih21 from the amplitude of the second search current ih22, and calculates the pole position θ by integrating the rotational angular frequency ω. For example, the pole position estimation section 120 calculates the rotational angular frequency ω by integrating the deviation of the amplitude of the second search current ih21 from the amplitude of the second search current ih22, by proportional / integral operation, proportional / integral / derivative operation, integral-proportional (I-P) operation, or the like.

[0093] Even in the case where the second search voltage Vinj2 along the δ axis is included in the second check voltage V22, the value of the inductance changes linearly with respect to the direction of the pole position ±90° in the γ axis, and thus the deviation of the amplitude of the second search current ih21 from the amplitude of the second search current ih22 becomes zero, and the magnitude of the second search current ih20 after the second search current ih21 and the second search current ih22 are synthesized becomes maximum or minimum. Figure 9 is a schematic diagram illustrating the principle of estimation of the pole position when generating the second inductance curve. In the case where the γ axis deviates from the pole position (in the case where the δ axis deviates from the q axis), a difference is generated between the amplitude of the second search current ih21 and the amplitude of the second search current ih22. For example, as shown in (a) of Figure 9 In the case where the γ axis deviates from the pole position (d axis in the drawing) in the positive direction (direction toward the q axis in the drawing), if the inductance Ld of the d axis is smaller than the inductance Lq of the q axis, the amplitude of the second search current ih22 is larger than the amplitude of the second search current ih21, as shown in (a) of

[0094] As shown in (b) of Figure 9 When the γ axis coincides with the d axis, the amplitude of the second search current ih21 is equal to the amplitude of the second search current ih22, as shown in (b) of

[0095] Thus, even in the case where the second search voltage Vinj2 along the δ axis is included in the second check voltage V22, the rotational angular frequency ω of the pole and the pole position θ can be estimated in the same manner as in the case where the first search voltage Vinj1 along the γ axis is included in the first check voltage V11.

[0096] Returning to Figure 8The PWM control section 114 calculates a voltage command vector in the fixed coordinate system based on the δ-axis voltage command Vδ_ref output by the check voltage application section 115, the γ-axis voltage command Vγ_ref output by the limit control section 116, and the magnetic pole position θ estimated by the magnetic pole position estimation section 120, performs two-phase / three-phase conversion on the voltage command vector in the fixed coordinate system, and calculates voltage commands for each phase of the U phase, the V phase, and the W phase. The PWM control section 114 switches the on / off of the plurality of switching elements 17 so as to apply a voltage corresponding to the voltage command of the U phase to the U phase of the motor 3, apply a voltage corresponding to the voltage command of the V phase to the V phase of the motor 3, and apply a voltage corresponding to the voltage command of the W phase to the W phase of the motor 3.

[0097] The curve generation section 130 generates a second inductance curve PLδ that represents the relationship between the current along the δ-axis (second coordinate axis) and the inductance, based on the relationship between the second check voltage V22 and the second check current i22 (refer to FIG. 9B) that flows between the power conversion circuit 10 and the motor 3 in correspondence with the second check voltage V22. Figure 4 ) For example, the curve generation section 130 generates the second inductance curve PLδ based on the relationship between the second check voltage V22 that includes the above-described second search voltage Vinj2 and the second check current i22 that includes the second search current ih20.

[0098] For example, the inductance calculation section 131 calculates the second inductance Lδ based on the search voltage amplitude Vh2 that is the amplitude of the second search voltage Vinj2, the amplitude of the second search current ih20, and the frequency fh2 of the second search voltage. As described above, the second inductance Lδ calculated in the state where the γ-axis coincides with the d-axis corresponds to the inductance Lq of the q-axis. The correlation processing section 132 stores the second inductance Lδ in correlation with the second direct current idc2 that corresponds to the magnitude of the second check current i22 in the curve storage section 118. The record in which the second inductance Lδ and the second direct current idc2 are correlated is stored in the curve storage section 118 in accordance with the value of the second direct current idc2 that increases over time, whereby the second inductance curve PLδ is saved in the curve storage section 118.

[0099] In the case where the second direct current idc2 increases in the positive direction over time and the case where the second direct current idc2 increases in the negative direction over time, the relationship between the magnitude of the second direct current idc2 and the second inductance Lδ can be considered to be equal. Therefore, the check voltage application section 115 can also perform the case where the second direct current idc2 increases over time with respect to either of the positive direction and the negative direction. Figure 10 is a graph that illustrates the second check current and the second check voltage in the case where the second direct current idc2 increases in the positive direction over time. Figure 10The horizontal axis of (a) indicates the passage of time, and the vertical axis indicates the instantaneous value of the second inspection current. Figure 10 The horizontal axis of (b) indicates the passage of time, and the vertical axis indicates the instantaneous value of the second inspection voltage. Figure 10 (b) of FIG. 22 indicates the time variation of the second inspection voltage V22 including the second direct-current voltage Vdc2 that increases in the positive direction and the second search voltage Vinj2 that increases in the positive direction as time passes. Figure 10 (a) of FIG. 22 indicates the time variation of the second inspection current i22 corresponding to the time variation of the second inspection voltage V22. As the second direct-current idc2 becomes larger in the positive direction, the amplitude of the second search current ih20 corresponding to the second search voltage Vinj2 becomes larger.

[0100] Figure 11 is an example of generating the second inductance curve based on Figure 10 The second inductance curve generated based on the second inspection voltage and the second inspection current shown in FIG. 22. Figure 11 The horizontal axis of (a) indicates the magnitude of the second inspection current. If the second inspection voltage and the second inspection current shown in FIG. 22 are based on Figure 10 The second inductance curve PLδ in which the second inductance Lδ becomes smaller as the second direct-current idc2 becomes larger in the positive direction is generated based on the second inspection voltage and the second inspection current shown in FIG. 22. Hereinafter, this is referred to as the positive-direction second inductance curve PLδ. As described above, in the case where the second direct-current idc2 becomes larger in the negative direction as time passes, the relationship between the magnitude of the second direct-current idc2 and the second inductance Lδ can be considered to be equal. Therefore, the second inductance curve PLδ in the case where the second direct-current idc2 becomes larger in the negative direction is generated by inverting the positive-direction second inductance curve PLδ about the vertical axis (negative-direction second inductance curve PLδ) (refer to the dotted line in the drawing). The inductance estimation unit 119 estimates the second inductance Lδ based on the δ-axis current iδ calculated by the current information acquisition unit 112 and the second inductance curve PLδ after the second inductance curve PLδ is stored in the curve storage unit 118.

[0101] The inductance estimation unit 119 can also generate the negative-direction second inductance curve PLδ instead of the positive-direction second inductance curve PLδ, and invert it to generate the positive-direction second inductance curve PLδ. In addition, the inductance estimation unit 119 can also generate both the positive-direction second inductance curve PLδ and the negative-direction second inductance curve PLδ by actually varying the second direct-current idc2 as with the generation of the first inductance curve PLγ.

[0102] In addition, the inspection voltage application unit 115 can change the amplitude of the alternating component included in the first inspection voltage V11 instead of changing the magnitude of the first direct-current voltage Vdc1. In addition, the inspection voltage application unit 115 can change the amplitude of the alternating component included in the first inspection voltage V11 in addition to changing the magnitude of the first direct-current voltage Vdc1. Similarly, the inspection voltage application unit 115 can change the amplitude of the alternating component included in the second inspection voltage V22 instead of changing the magnitude of the second direct-current voltage Vdc2. In addition, the inspection voltage application unit 115 can change the amplitude of the alternating component included in the second inspection voltage V22 in addition to changing the magnitude of the second direct-current voltage Vdc2.

[0103] Figure 12 Fig. 1 is a diagram illustrating a hardware structure of the control circuit 100. The control circuit 100 has, for example, a circuit 190. The circuit 190 has one or more processors 191, a memory 192, a storage 193, an input-output port 194, and a switch control circuit 195.

[0104] The storage 193 includes a nonvolatile storage medium such as a flash memory or a hard disk. The storage 193 stores a program for causing the control circuit 100 to perform: application of an inspection voltage, whose magnitude changes over time, from the power conversion circuit 10 to the motor 3; application of a limit voltage from the power conversion circuit 10 to the motor 3 to limit rotation of the motor 3 caused by the application of the inspection voltage; generation of an inductance curve representing a relationship between a current and an inductance of the motor 3, based on a relationship between the inspection voltage and an inspection current flowing between the power conversion circuit 10 and the motor 3 in correspondence with the inspection voltage; estimation of the inductance based on the current flowing through the motor 3 and the inductance curve; and control of the power conversion circuit 10 based on a result of the estimation of the inductance. For example, the storage 193 stores a program for causing the control circuit 100 to constitute the above-described functional blocks.

[0105] The memory 192 temporarily stores a program loaded from the storage 193 and data generated in the course of execution of the program. The processor 191 causes the control circuit 100 to function as the functional blocks by executing the program stored in the memory 192. The input-output port 194 performs input and output of an electric signal between the current sensor 16 according to an instruction from the processor 191. The switch control circuit 195 switches on / off of the plurality of switching elements 17 according to an instruction from the processor 191. The above-described hardware structure is only an example, and can be appropriately changed. For example, at least any one of the functional blocks can be constituted by an application specific integrated circuit (ASIC) or the like.

[0106] (Control process)

[0107] Next, as an example of the power conversion method, a control process performed by the control circuit 100 is exemplified. The control process includes: applying, from the power conversion circuit 10 to the motor 3, a check voltage whose magnitude changes over time; applying, from the power conversion circuit 10 to the motor 3, a limit voltage to limit rotation of the motor 3 caused by the application of the check voltage; generating an inductance curve representing a relationship between a current and an inductance of the motor 3, based on a relationship between the check voltage and a check current flowing between the power conversion circuit 10 and the motor 3 corresponding to the check voltage; estimating the inductance based on the current flowing through the motor 3 and the inductance curve; and controlling the power conversion circuit 10 based on a result of the estimation of the inductance.

[0108] The application of the check voltage from the power conversion circuit 10 to the motor 3 can include applying, from the power conversion circuit 10 to the motor 3, a first check voltage along a first coordinate axis in the motor 3 whose magnitude changes over time. The application of the limit voltage from the power conversion circuit 10 to the motor 3 can also include applying, from the power conversion circuit 10 to the motor 3, a first limit voltage along a second coordinate axis perpendicular to the first coordinate axis to limit rotation of the motor 3 caused by the application of the first check voltage. The generation of the inductance curve can also include generating a first inductance curve representing a relationship between a current along the first coordinate axis and the inductance, based on a relationship between the first check voltage and a first check current flowing between the power conversion circuit 10 and the motor 3 corresponding to the first check voltage. The estimation of the inductance can also include estimating a first inductance corresponding to the first coordinate axis based on the current along the first coordinate axis and the first inductance curve. The control of the power conversion circuit 10 can include controlling the power conversion circuit 10 based on a result of the estimation of the first inductance.

[0109] The application of the check voltage from the power conversion circuit 10 to the motor 3 can include applying, from the power conversion circuit 10 to the motor 3, a second check voltage along the second coordinate axis during a period different from a period during which the first check voltage is applied to the motor 3. The application of the limit voltage from the power conversion circuit 10 to the motor 3 can also include applying, from the power conversion circuit 10 to the motor 3, a second limit voltage along the first coordinate axis to limit rotation of the motor 3 caused by the application of the second check voltage. The generation of the inductance curve can also include further generating a second inductance curve representing a relationship between a current along the second coordinate axis and the inductance, based on a relationship between the second check voltage and a second check current flowing between the power conversion circuit 10 and the motor 3 corresponding to the second check voltage. The estimation of the inductance can also include further estimating a second inductance corresponding to the second coordinate axis based on the current along the second coordinate axis and the second inductance curve. The control of the power conversion circuit 10 can include controlling the power conversion circuit 10 based on results of the estimations of the first inductance and the second inductance.

[0110] For example, as shown in FIG. 10, the control circuit 100 generates the first inductance curve in step S01 and generates the second inductance curve in step S02. The details of steps S01 and S02 will be described later. Figure 13 Next, the control circuit 100 executes step S03 and step S04. In step S03, the current information acquisition section 112 acquires information of the secondary-side current on the basis of the detection result of the current sensor 16. For example, the current information acquisition section 112 calculates the γ-axis current iγ and the δ-axis current iδ in the γδ coordinate system on the basis of the U-phase current iu, the V-phase current iv, and the W-phase current iw detected by the current sensor 16. In step S04, the inductance estimation section 119 estimates the inductance of the motor 3 on the basis of the current flowing through the motor 3 and the inductance curve stored in the curve storage section 118. For example, the inductance estimation section 119 estimates the first inductance Lγ on the basis of the γ-axis current iγ and the first inductance curve PLγ and estimates the second inductance Lδ on the basis of the δ-axis current iδ and the second inductance curve PLδ.

[0111] Next, the control circuit 100 executes step S05 and step S06. In step S05, the drive control section 111 generates a voltage command for causing the motor 3 to perform a desired operation. For example, the drive control section 111 generates the above-described γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref. In step S06, the pole position estimation section 113 calculates the direction of the induced voltage vector on the basis of the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref, the γ-axis current iγ and the δ-axis current iδ, the winding resistance R of the motor 3, the first inductance Lγ of the motor 3, and the second inductance Lδ of the motor 3, and estimates the position of the magnetic pole of the motor 3 on the basis of the direction of the induced voltage vector.

[0112] Next, the control circuit 100 executes step S07. In step S07, the PWM control section 114 starts turning on / off the plurality of switching elements 17 to apply the secondary-side voltage corresponding to the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref to the motor 3 on the basis of the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref calculated by the drive control section 111 and the position of the magnetic pole of the motor 3 estimated by the pole position estimation section 113. Then, the control circuit 100 returns the process to step S03. Thereafter, until a stop command of the operation of the motor 3 is input, the control circuit 100 repeatedly executes steps S03 to S07 at a prescribed control cycle.

[0113]

[0114] is a flowchart illustrating the generation process of the first inductance curve in step S01. As shown in FIG. 10, the control circuit 100 first acquires the information of the secondary-side current in step S01-1. For example, the control circuit 100 acquires the information of the secondary-side current on the basis of the detection result of the current sensor 16. Figure 14 Figure 14 ​As shown, the control circuit 100 executes step Sll, step S12. In step Sll, the check voltage application section 115 generates the first direct current idcl that increases with the passage of time. In step S12, the limit control section 116 performs proportional / integral operation on the deviation of zero from the rotational angular frequency ω of the rotor of the motor 3 to generate the first limit current i 12.

[0115] Next, the control circuit 100 executes step S13, step S14. In step S13, the current information acquisition section 112 acquires information of the secondary-side current based on the detection result of the current sensor 16. For example, the current information acquisition section 112 calculates the γ-axis current iγ and the δ-axis current iδ in the γδ coordinate system based on the U-phase current iu, the V-phase current iv, and the W-phase current iw detected by the current sensor 16. In step S14, the check voltage application section 115 calculates the first direct voltage Vdc1 by performing proportional / integral operation on the deviation of the first direct current idcl from the γ-axis current iγ. The limit control section 116 calculates the first limit voltage V12 by performing proportional / integral operation on the deviation of the first limit current i 12 from the δ-axis current iδ.

[0116] Next, the control circuit 100 executes step S15. In step S15, the pole position estimation section 120 outputs the first search voltage Vinj1 to the check voltage application section 115. The check voltage application section 115 adds the first search voltage Vinj1 and the first direct voltage Vdc1 to calculate the first check voltage V11.

[0117] Next, the control circuit 100 executes step S17. In step S17, the check voltage application section 115 outputs the first check voltage V11 as the γ-axis voltage command Vγ_ref to the PWM control section 114, and the limit control section 116 outputs the first limit voltage V12 as the δ-axis voltage command Vδ_ref to the PWM control section 114. The PWM control section 114 starts turning on / off the plurality of switching elements 17 so as to apply the secondary-side voltage corresponding to the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref to the motor 3.

[0118] Next, the control circuit 100 executes step S18, step S19, step S21. In step S18, the pole position estimation section 120 calculates the amplitude of the first search current ihl 1 and the amplitude of the first search current ihl 2 based on the γ-axis current iγ and the δ-axis current iδ. In step S19, the pole position estimation section 120 calculates the rotational angular frequency ω of the γ-axis in such a manner that the deviation of the amplitude of the first search current ihl 1 from the amplitude of the first search current ihl 2 is reduced. In step S21, the pole position estimation section 120 calculates the pole position θ by integrating the rotational angular frequency ω of the γ-axis.

[0119] Next, the control circuit 100 executes step S22, step S23. In step S22, the curve generating section 130 calculates the first inductance Lγ based on the relationship between the first check voltage V11 and the first check current i11 that flows between the power conversion circuit 10 and the motor 3 corresponding to the first check voltage V11. In step S23, the curve generating section 130 stores the first inductance Lγ in association with the first direct current idc1 in the curve storage section 118.

[0120] Next, the control circuit 100 executes step S24. In step S24, the curve generating section 130 confirms whether or not the association of the first inductance Lγ with the first direct current idc1 is completed over the entire frequency band predetermined in such a manner that the first direct current idc1 is varied. In step S24, in the case where it is determined that there is a frequency band in which the association of the first inductance Lγ with the first direct current idc1 is not completed, the control circuit 100 returns the process to step S11. Thereafter, the control circuit 100 repeats step S11 to step S24 until the association of the first inductance Lγ with the first direct current idc1 is completed over the entire frequency band of the first direct current idc1. In step S24, in the case where it is determined that the association of the first inductance Lγ with the first direct current idc1 is completed over the entire frequency band of the first direct current idc1, the control circuit 100 ends the process.

[0121] The control circuit 100 executes the above process for both the case where the first direct current idc1 is increased in the positive direction and the case where the first direct current idc1 is increased in the negative direction. Thereby, the first inductance curve PLγ is saved in the curve storage section 118.

[0122] Figure 15 is a flowchart illustrating the generation process of the second inductance curve in step S02. As shown in Figure 14 The control circuit 100 executes step S31, step S32. In step S31, the check voltage applying section 115 generates the second direct current idc2 that is increased with the passage of time. In step S32, the limit control section 116 generates the second limit current i21 by performing proportional / integral operation on the deviation of zero from the rotational angular frequency ω of the rotor of the motor 3.

[0123] Next, the control circuit 100 executes step S33, step S34. In step S33, the current information acquisition section 112 acquires information of the secondary-side current based on the detection result of the current sensor 16. For example, the current information acquisition section 112 calculates the γ-axis current iγ and the δ-axis current iδ in the γδ coordinate system based on the U-phase current iu, the V-phase current iv, and the W-phase current iw detected by the current sensor 16. In step S34, the check voltage application section 115 calculates the second direct-current voltage Vdc2 by performing proportional / integral operation on the deviation of the second direct-current idc2 and the δ-axis current iδ. The limit control section 116 calculates the second limit voltage V21 by performing proportional / integral operation on the deviation of the second limit current i21 and the γ-axis current iγ.

[0124] Next, the control circuit 100 executes step S35. In step S35, the pole position estimation section 120 outputs the second search voltage Vinj2 to the check voltage application section 115. The check voltage application section 115 calculates the second check voltage V22 by adding the second search voltage Vinj2 to the second direct-current voltage Vdc2.

[0125] Next, the control circuit 100 executes step S37. In step S37, the check voltage application section 115 outputs the second check voltage V22 to the PWM control section 114 as the δ-axis voltage command Vδ_ref, and the limit control section 116 outputs the second limit voltage V21 to the PWM control section 114 as the γ-axis voltage command Vγ_ref. The PWM control section 114 starts turning on / off the plurality of switching elements 17 so as to apply the secondary-side voltage corresponding to the γ-axis voltage command Vγ_ref and the δ-axis voltage command Vδ_ref to the motor 3.

[0126] Next, the control circuit 100 executes step S38, step S39, step S41. In step S38, the pole position estimation section 120 calculates the amplitude of the second search current ih21 and the amplitude of the second search current ih22 based on the γ-axis current iγ and the δ-axis current iδ. In step S39, the pole position estimation section 120 calculates the rotational angular frequency ω of the γ-axis in such a manner that the deviation of the amplitude of the second search current ih21 and the amplitude of the second search current ih22 is reduced. In step S41, the pole position estimation section 120 calculates the pole position θ by integrating the rotational angular frequency ω of the γ-axis.

[0127] Next, the control circuit 100 executes step S42, step S43. In step S42, the curve generating portion 130 calculates the second inductance Lδ based on the relationship between the second check voltage V22 and the second check current i22 that flows between the power conversion circuit 10 and the motor 3 in correspondence with the second check voltage V22. In step S43, the curve generating portion 130 stores the second inductance Lδ in association with the second direct current idc2 in the curve storage portion 118.

[0128] Next, the control circuit 100 executes step S44. In step S44, the curve generating portion 130 confirms whether or not the association of the second inductance Lδ with the second direct current idc2 is completed over the entire frequency band predetermined in such a manner that the second direct current idc2 is varied. In step S44, in the case where it is determined that there is a frequency band in which the association of the second inductance Lδ with the second direct current idc2 is not completed, the control circuit 100 returns the process to step S31. Thereafter, the control circuit 100 repeats step S31 to step S44 until the association of the second inductance Lδ with the second direct current idc2 is completed over the entire frequency band of the second direct current idc2. In step S44, in the case where it is determined that the association of the second inductance Lδ with the second direct current idc2 is completed over the entire frequency band of the second direct current, the control circuit 100 ends the process.

[0129] As described above, the control circuit 100 can also generate the second inductance curve PLδ in the positive direction by executing the above process in the case where the second direct current idc2 is increased in the positive direction, and generate the second inductance curve PLδ in the negative direction by reversing the second inductance curve PLδ in the positive direction.

[0130] (EFFECTS OF EMBODIMENTS)

[0131] As described above, the power conversion device 2 includes: a check voltage applying portion 115 that applies a check voltage that varies in size over time from the power conversion circuit 10 to the motor 3; a limit control portion 116 that applies a limit voltage from the power conversion circuit 10 to the motor 3 to limit rotation of the motor 3 caused by the application of the check voltage; a curve generating portion 130 that generates an inductance curve that indicates the relationship between a current and an inductance of the motor 3 based on the relationship between the check voltage and a check current that flows between the power conversion circuit 10 and the motor 3 in correspondence with the check voltage; an inductance estimating portion 119 that estimates the inductance based on the current flowing through the motor 3 and the inductance curve; and a control portion that controls the power conversion circuit 10 based on the estimation result of the inductance.

[0132] When the power conversion circuit 10 is controlled to cause the motor 3 to perform a desired operation, an operation based on the inductance of the motor 3 is performed. The inductance of the motor 3 varies due to saturation of magnetic flux. Therefore, unless an operation that takes into account the variation in inductance caused by saturation of magnetic flux is performed, it is possible that the stability of the operation of the motor 3 is reduced due to an error in the operation result. In contrast, according to the present power conversion device 2, the rotation of the motor 3 caused by the application of the check voltage is limited due to the application of the limit voltage, and thus it is possible to easily vary the check voltage in the target direction in a stopped state, and to generate an inductance curve for a wide range of current amplitudes. Therefore, in a wide range of current amplitudes, it is possible to estimate the inductance with high reliability. Therefore, it is possible to easily perform control based on the estimation result of the inductance with high reliability.

[0133] The check voltage application section 115 can also apply a first check voltage V11 that varies in magnitude along a first coordinate axis in the motor 3 with the passage of time from the power conversion circuit 10 to the motor 3, the limit control section 116 applies a first limit voltage V12 along a second coordinate axis perpendicular to the first coordinate axis from the power conversion circuit 10 to the motor 3 to limit the rotation of the motor 3 caused by the application of the first check voltage V11, the curve generation section 130 generates a first inductance curve PLy that indicates the relationship between the current along the first coordinate axis and the inductance based on the relationship between the first check voltage V11 and a first check current i11 that flows between the power conversion circuit 10 and the motor 3 corresponding to the first check voltage V11, and the inductance estimation section 119 estimates a first inductance Lγ corresponding to the first coordinate axis based on the current along the first coordinate axis and the first inductance curve PLy, and the control section can control the power conversion circuit 10 based on the estimation result of the first inductance Lγ. In this case, by making the first limit voltage V12 perpendicular to the direction of application of the first check voltage V11, it is possible to make the first check voltage V11 vary greatly without being affected by the first limit voltage V12. Therefore, it is possible to generate an inductance curve for a wider range of current amplitudes.

[0134] It is also possible to further provide a pole position estimation section 113 that estimates the pole position θ of the motor 3, and the check voltage application section 115 applies the first check voltage V11 from the power conversion circuit 10 to the motor 3 with the direction of the estimated pole position θ as the first coordinate axis. In this case, it is possible to estimate the inductance corresponding to the direction of the pole position θ with high reliability. Thus, it is possible to further improve the stability of the operation of the motor 3.

[0135] The pole position estimation section 113 can also apply an alternating-current search voltage from the power conversion circuit 10 to the motor 3, and estimate the pole position θ based on a search current that flows between the power conversion circuit 10 and the motor 3 in correspondence with the search voltage. In this case, the pole position θ can be easily estimated with high reliability, and thus the inductance corresponding to the direction of the pole position θ can be estimated with higher reliability.

[0136] The pole position estimation section 113 can also apply a search voltage along the first coordinate axis to the motor 3 from the power conversion circuit 10 as the first check voltage V11, and the curve generation section 130 can generate the first inductance curve PLy based on a relationship between the first check voltage V11 including the search voltage and the first check current i11 including the search current. In this case, the search voltage can be effectively utilized as a part of the first check voltage V11.

[0137] The pole position estimation section 113 can also estimate the pole position θ based on a direction in which the magnitude of the search current becomes maximum or minimum. In this case, the pole position θ can be more easily estimated.

[0138] The check voltage application section 115 can also apply the first check voltage V11 including a direct-current voltage whose magnitude changes with the passage of time and the search voltage to the motor 3 from the power conversion circuit 10. In this case, the search voltage can be effectively utilized, and the magnitude of the first check voltage V11 can be easily changed.

[0139] The check voltage application section 115 can also apply the first check voltage V11 including an alternating-current voltage and a direct-current voltage whose magnitude changes with the passage of time to the motor 3 from the power conversion circuit 10. In this case, vibration of the motor 3 caused by the alternating-current voltage can be suppressed, and the magnitude of the first check voltage V11 can be easily changed.

[0140] The check voltage application section 115 can also apply the first check voltage V11 including an alternating-current voltage whose amplitude changes with the passage of time to the motor 3 from the power conversion circuit 10. In this case, the magnitude of the first check voltage V11 can be easily changed.

[0141] The inspection voltage application section 115 can also apply a second inspection voltage V22 along the second coordinate axis from the power conversion circuit 10 to the motor 3 during a period different from the period during which the first inspection voltage V11 is applied to the motor 3, the limit control section 116 can apply a second limit voltage V21 along the first coordinate axis from the power conversion circuit 10 to the motor 3 to limit rotation of the motor 3 caused by application of the second inspection voltage V22, the curve generation section 130 can further generate a second inductance curve PLδ representing a relationship between current along the second coordinate axis and inductance, based on a relationship between the second inspection voltage V22 and a second inspection current i22 flowing between the power conversion circuit 10 and the motor 3 in correspondence with the second inspection voltage V22, and the inductance estimation section 119 can further estimate a second inductance Lδ corresponding to the second coordinate axis, based on current along the second coordinate axis and the second inductance curve PLδ. The control section can control the power conversion circuit 10 based on estimation results of the first inductance Lγ and the second inductance Lδ. In this case, it is possible to estimate both the first inductance Lγ and the second inductance Lδ with high reliability in a wide range of current amplitude. Therefore, it is possible to easily achieve control based on estimation results of inductances with higher reliability.

[0142] It is also possible to further provide a pole position estimation section 113 that estimates a magnetic pole position θ of the motor 3, and the inspection voltage application section 115 applies the first inspection voltage V11 from the power conversion circuit 10 to the motor 3 with a direction of the estimated magnetic pole position θ set as the first coordinate axis, and applies the second inspection voltage V22 from the power conversion circuit 10 to the motor 3. In this case, it is possible to estimate an inductance corresponding to the direction of the magnetic pole position θ and an inductance corresponding to a direction perpendicular to the direction of the magnetic pole position θ with high reliability. Thus, it is possible to further improve stability of operation of the motor 3.

[0143] The pole position estimation section 113 can also apply an alternating-current search voltage from the power conversion circuit 10 to the motor 3, and estimate the magnetic pole position θ based on a search current flowing between the power conversion circuit 10 and the motor 3 in correspondence with the search voltage. In this case, it is possible to easily estimate the magnetic pole position θ with high reliability, and thus it is possible to estimate an inductance corresponding to the direction of the magnetic pole position θ with higher reliability.

[0144] Also, during the period in which the first check voltage V11 is applied to the motor 3, the pole position estimation section 113 can apply, from the power conversion circuit 10 to the motor 3, the first search voltage Vinj1 along the first coordinate axis included in the first check voltage V11, estimate the pole position θ based on the first search current ih12 flowing between the power conversion circuit 10 and the motor 3 corresponding to the first search voltage Vinj1, the curve generation section 130 generate the first inductance curve PLγ based on the relationship between the first check voltage V11 including the first search voltage Vinj1 and the first check current i11 including the first search current ih12, during the period in which the second check voltage V22 is applied to the motor 3, the pole position estimation section 113 can apply, from the power conversion circuit 10 to the motor 3, the second search voltage Vinj2 along the second coordinate axis included in the second check voltage V22, and estimate the pole position θ based on the second search current ih22 flowing between the power conversion circuit 10 and the motor 3 corresponding to the second search voltage Vinj2, the curve generation section 130 generate the second inductance curve PLδ based on the relationship between the second check voltage V22 including the second search voltage Vinj2 and the second check current i22 including the second search current ih22. In this case, the first search voltage Vinj1 can be effectively utilized as a part of the first check voltage V11, and the second search voltage Vinj2 can be effectively utilized as a part of the second check voltage V22.

[0145] The pole position estimation section 113 can also estimate the pole position θ based on the direction in which the magnitude of the first search current ih12 becomes maximum or minimum, and estimate the pole position θ based on the direction in which the magnitude of the second search current ih22 becomes maximum or minimum. In this case, the pole position θ can be more easily estimated.

[0146] The check voltage application section 115 can also apply, from the power conversion circuit 10 to the motor 3, the first check voltage V11 including the first search voltage Vinj1 and the first direct current voltage Vdc1 whose magnitude changes with the passage of time, and apply, from the power conversion circuit 10 to the motor 3, the second check voltage V22 including the second search voltage Vinj2 and the second direct current voltage Vdc2 whose magnitude changes with the passage of time. In this case, the first search voltage Vinj1 and the second search voltage Vinj2 can be effectively utilized, and the magnitudes of the first check voltage V11 and the second check voltage V22 can be easily changed.

[0147] The above describes the embodiments, but the present application is not limited to the illustrated embodiments and can be appropriately changed without departing from the gist thereof. For example, the motor 3 can also be provided with a sensor that outputs information related to the magnetic pole position. As a specific example of the sensor, a pulse generator or the like can be given. In the case where the sensor is an absolute type pulse generator, the magnetic pole position can be detected based on the output of the pulse generator, the rotational angular frequency ω can be calculated based on the detection result of the magnetic pole position, and the limit voltage can be generated based on the detection result of the magnetic pole position and the calculation result of the rotational angular frequency ω. In the case where the sensor is an incremental type pulse generator, the initial magnetic pole position can be estimated based on the search voltage and the search current. The magnetic pole position can be detected based on the estimation result of the initial magnetic pole position and the output of the pulse generator, that is, the cumulative number of incremental pulses, the rotational angular frequency ω can be calculated based on the count value of the incremental pulses per prescribed time, and the limit voltage can be generated based on the detection result of the magnetic pole position and the calculation result of the rotational angular frequency ω.

[0148] Symbol explanation

[0149] 3... motor, 2... power conversion device, 10... power conversion circuit, 111... drive control section, 113... magnetic pole position estimation section, 114... PWM control section, 119... inductance estimation section, 115... inspection voltage application section, 116... limit control section, 130... curve generation section, V11... first inspection voltage, V12... first limit voltage, PLγ... first inductance curve, Lγ... first inductance, Vinj1... first search voltage, Vdc1... first direct current voltage, i11... first inspection current, V12... first limit voltage, ih11... first search current, ih12... first search current, θ... magnetic pole position, V22... second inspection voltage, PLδ... second inductance curve, Lδ... second inductance, Vinj2... second search voltage, Vdc2... second direct current voltage, i22... second inspection current, V21... second limit voltage, ih21... second search current, ih22... second search current.

Claims

1. A power conversion device comprising: a check voltage application section that applies a check voltage, which varies in magnitude over time, from a power conversion circuit to a motor; a limit control section that applies a limit voltage from the power conversion circuit to the motor to limit rotation of the motor caused by application of the check voltage; a curve generation section that generates an inductance curve representing a relationship between current and inductance of the motor, based on a relationship between the check voltage and a check current that flows between the power conversion circuit and the motor in correspondence with the check voltage; an inductance estimation section that estimates the inductance based on current flowing through the motor and the inductance curve; and a control section that controls the power conversion circuit based on a result of the estimation of the inductance, the check voltage application section applies a first check voltage from the power conversion circuit to the motor, the first check voltage varying in magnitude over time along a first coordinate axis in the motor, the limit control section applies a first limit voltage from the power conversion circuit to the motor along a second coordinate axis perpendicular to the first coordinate axis to limit rotation of the motor caused by application of the first check voltage, the curve generation section generates a first inductance curve representing a relationship between current along the first coordinate axis and the inductance, based on a relationship between the first check voltage and a first check current that flows between the power conversion circuit and the motor in correspondence with the first check voltage, the inductance estimation section estimates a first inductance corresponding to the first coordinate axis based on current along the first coordinate axis and the first inductance curve, the control section controls the power conversion circuit based on a result of the estimation of the first inductance.

2. The power conversion device according to claim 1, wherein a pole position estimation section that estimates a pole position of the motor is further included, the check voltage application section applies the first check voltage from the power conversion circuit to the motor in a direction passing through the estimated pole position as the first coordinate axis.

3. The power conversion device according to claim 2, wherein the pole position estimation section applies an alternating-current search voltage from the power conversion circuit to the motor, and estimates the pole position based on a search current that flows between the power conversion circuit and the motor in correspondence with the search voltage.

4. The power conversion device according to claim 3, wherein the pole position estimation section includes the search voltage along the first coordinate axis into the first check voltage to apply from the power conversion circuit to the motor, the curve generation section generates the first inductance curve based on a relationship between the first check voltage including the search voltage and the first check current including the search current.

5. The power conversion device according to claim 3 or 4, wherein the pole position estimation section estimates the pole position based on a direction in which a magnitude of the search current becomes maximum or minimum.

6. The power conversion device according to claim 4, wherein the inspection voltage application section applies the first inspection voltage, which includes the search voltage and a direct-current voltage whose magnitude changes over time, from the power conversion circuit to the motor.

7. The power conversion device according to any one of claims 1 to 3, wherein the inspection voltage application section applies the first inspection voltage, which includes an alternating-current voltage and a direct-current voltage whose magnitude changes over time, from the power conversion circuit to the motor.

8. The power conversion device according to any one of claims 1 to 4, wherein the inspection voltage application section applies the first inspection voltage, which includes an alternating-current voltage whose amplitude changes over time, from the power conversion circuit to the motor.

9. The power conversion device according to claim 1, wherein the inspection voltage application section applies a second inspection voltage along the second coordinate axis from the power conversion circuit to the motor during a period different from the period during which the first inspection voltage is applied to the motor, the limit control section applies a second limit voltage along the first coordinate axis from the power conversion circuit to the motor to limit rotation of the motor caused by application of the second inspection voltage, the curve generation section generates a second inductance curve representing a relationship between current along the second coordinate axis and the inductance, further based on a relationship between the second inspection voltage and a second inspection current that flows between the power conversion circuit and the motor in correspondence with the second inspection voltage, the inductance estimation section estimates a second inductance corresponding to the second coordinate axis further based on current along the second coordinate axis and the second inductance curve, and the control section controls the power conversion circuit based on the first inductance and an estimation result of the second inductance.

10. The power conversion device according to claim 9, further comprising a pole position estimation section that estimates a pole position of the motor, the inspection voltage application section applies the first inspection voltage from the power conversion circuit to the motor and the second inspection voltage from the power conversion circuit to the motor with a direction passing through the estimated pole position as the first coordinate axis.

11. The power conversion device according to claim 10, wherein the pole position estimation section applies an alternating-current search voltage from the power conversion circuit to the motor and estimates the pole position based on a search current that flows between the power conversion circuit and the motor in correspondence with the search voltage.

12. The power conversion device according to claim 11, wherein during the period in which the first inspection voltage is applied to the motor, The pole position estimation section includes a first search voltage along the first coordinate axis into the first check voltage to be applied to the motor from the power conversion circuit, estimates the pole position based on a first search current flowing between the power conversion circuit and the motor corresponding to the first search voltage, and The curve generation section generates the first inductance curve based on a relationship between the first check voltage including the first search voltage and the first check current including the first search current, During the period in which the second check voltage is applied to the motor, The pole position estimation section includes a second search voltage along the second coordinate axis into the second check voltage to be applied to the motor from the power conversion circuit, estimates the pole position based on a second search current flowing between the power conversion circuit and the motor corresponding to the second search voltage, and The curve generation section generates the second inductance curve based on a relationship between the second check voltage including the second search voltage and the second check current including the second search current.

13. The power conversion device according to claim 12, wherein The pole position estimation section estimates the pole position based on a direction in which the magnitude of the first search current becomes maximum or minimum, and estimates the pole position based on a direction in which the magnitude of the second search current becomes maximum or minimum.

14. The power conversion device according to claim 12 or 13, wherein The check voltage application section applies the first check voltage including the first search voltage and a first direct current voltage whose magnitude changes with the passage of time from the power conversion circuit to the motor, and applies the second check voltage including the second search voltage and a second direct current voltage whose magnitude changes with the passage of time from the power conversion circuit to the motor.

15. A power conversion method comprising: applying a check voltage whose magnitude changes with the passage of time from a power conversion circuit to a motor; applying a limit voltage from the power conversion circuit to the motor to limit rotation of the motor caused by the application of the check voltage; generating an inductance curve representing a relationship between a current and an inductance of the motor based on a relationship between the check voltage and a check current flowing between the power conversion circuit and the motor corresponding to the check voltage; estimating the inductance based on a current flowing through the motor and the inductance curve; and controlling the power conversion circuit based on a result of the estimation of the inductance, the application of the check voltage from the power conversion circuit to the motor includes the application of a first check voltage from the power conversion circuit to the motor, the first check voltage changing in magnitude with the passage of time along a first coordinate axis in the motor; ​ applying the limit voltage from the power conversion circuit to the motor includes applying a first limit voltage along a second coordinate axis perpendicular to the first coordinate axis from the power conversion circuit to the motor to limit rotation of the motor caused by application of the first check voltage, generating the inductance curve includes generating a first inductance curve representing a relationship between current along the first coordinate axis and the inductance based on a relationship between the first check voltage and a first check current flowing between the power conversion circuit and the motor corresponding to the first check voltage, estimating the inductance includes estimating a first inductance corresponding to the first coordinate axis based on current along the first coordinate axis and the first inductance curve, controlling the power conversion circuit includes controlling the power conversion circuit based on a result of the estimation of the first inductance.

16. The power conversion method according to claim 15, wherein applying the check voltage from the power conversion circuit to the motor includes applying a second check voltage along the second coordinate axis from the power conversion circuit to the motor during a period different from a period during which the first check voltage is applied to the motor, applying the limit voltage from the power conversion circuit to the motor includes applying a second limit voltage along the first coordinate axis from the power conversion circuit to the motor to limit rotation of the motor caused by application of the second check voltage, generating the inductance curve includes generating a second inductance curve representing a relationship between current along the second coordinate axis and the inductance based on a relationship between the second check voltage and a second check current flowing between the power conversion circuit and the motor corresponding to the second check voltage, estimating the inductance includes estimating a second inductance corresponding to the second coordinate axis based on current along the second coordinate axis and the second inductance curve, controlling the power conversion circuit includes controlling the power conversion circuit based on results of the estimations of the first inductance and the second inductance.

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