Parameter calculation device, parameter calculation method, and program

Abstract

To accurately calculate parameters of an induction motor having skew in a relatively short time.SOLUTION: A first inductance is calculated on the basis of the phase difference between a stator current and a rotor current corresponding to the reference cross section in the axis normal direction of an induction motor having skew and the other cross sections, respectively. A second inductance is calculated on the basis of the phase difference between the stator current and rotor current corresponding to the reference cross section. An increase / decrease rate of the first inductance with respect to the second inductance is calculated. A third inductance is calculated on the basis of the phase difference between the stator current and the rotor current corresponding to the reference cross section by using two-dimensional magnetic field analysis and a voltage equation corresponding to the induction motor A result of multiplying the third inductance by the increase / decrease rate is regarded as a corrected inductance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for calculating parameters of an induction motor.

Background Art

[0002] In an induction motor having skew, when the phase difference between the current flowing through the stator and the current flowing through the rotor changes due to the difference in the cross-section in the axial normal direction of the induction motor, that is, the change in the skew angle, the parameters of the induction motor change.

[0003] Therefore, as a parameter calculation device for calculating the parameters of an induction motor having skew, there is one that calculates parameters using three-dimensional magnetic field analysis (three-dimensional magnetic field analysis). However, since three-dimensional magnetic field analysis takes a relatively long time, there is a concern that it takes a relatively long time to calculate the parameters. As a related technique, there is Patent Document 1.

[0004] Further, as another parameter calculation device, there is one that calculates parameters by performing two-dimensional magnetic field analysis on a plurality of cross-sections in the axial normal direction of the induction motor. However, when the number of cross-sections in the axial normal direction of the induction motor is relatively large, there is a concern that it takes a relatively long time to calculate the parameters, similar to the above parameter calculation device. As a related technique, there is Patent Document 2.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] One aspect of the present invention is to calculate the parameters of an induction motor with skew in a relatively short time and with high accuracy. [Means for solving the problem]

[0007] One embodiment of the present invention is a parameter calculation device comprising: a first inductance calculation unit that calculates a first inductance based on the phase difference between the stator current and rotor current corresponding to a reference cross section in the axial normal direction of an induction motor having skew and other cross sections; a second inductance calculation unit that calculates a second inductance based on the phase difference between the stator current and rotor current corresponding to the reference cross section; an increase / decrease rate calculation unit that calculates the increase / decrease rate of the first inductance with respect to the second inductance; a parameter calculation unit that calculates a third inductance based on the phase difference between the stator current and rotor current corresponding to the reference cross section using two-dimensional magnetic field analysis and a voltage equation corresponding to the induction motor; and a correction unit that takes the result of multiplying the third inductance by the increase / decrease rate as the corrected inductance.

[0008] In the case of an induction motor with skew, the phase difference between the stator current and the rotor current changes for each cross-section (skew angle) in the direction normal to the axis of the induction motor. Therefore, the inductance calculated from the phase difference between the stator current and the rotor current also changes for each cross-section in the direction normal to the axis of the induction motor. Utilizing this, a first inductance is calculated based on the phase difference corresponding to a reference cross-section and other cross-sections in the direction normal to the axis of the induction motor, and a second inductance is calculated based on the phase difference corresponding to the reference cross-section. The rate of increase or decrease of the first inductance relative to the second inductance is calculated, and the result of multiplying the third inductance, calculated by two-dimensional magnetic field analysis and voltage equations, by this rate is obtained as the corrected inductance. This allows the corrected inductance to approach the inductance calculated by three-dimensional magnetic field analysis, thereby improving the accuracy of inductance calculation. Furthermore, since the inductance is calculated using two-dimensional magnetic field analysis, the time required for inductance calculation can be reduced compared to calculating inductance using three-dimensional induction magnetic field analysis.

[0009] Furthermore, the first inductance calculation unit may be configured to calculate the first stator current, the first rotor current, and the first rotor magnetic flux and first stator voltage corresponding to the first phase difference between the first stator current and the first rotor current in the reference cross section, and to calculate the second stator current, the second rotor current, and the second rotor magnetic flux and second stator voltage corresponding to the second phase difference between the second stator current and the second rotor current in the other cross section, and to calculate the first inductance based on the first and second rotor magnetic fluxes and the first and second stator voltages, and the second inductance calculation unit may be configured to calculate the second inductance based on the first rotor magnetic flux and the first stator voltage.

[0010] Furthermore, the first inductance calculation unit includes a first phase difference calculation unit that calculates the first rotor current and the first phase difference from the first stator current and slip frequency by two-dimensional magnetic field analysis, a map creation unit that calculates multiple rotor magnetic fluxes corresponding to multiple phase differences based on the first phase difference in the first stator current and the first rotor current by two-dimensional magnetic field analysis, calculates multiple stator voltages corresponding to the multiple phase differences, creates a rotor magnetic flux map showing the correspondence between the multiple phase differences and the multiple rotor magnetic fluxes, and creates a stator voltage map showing the correspondence between the multiple phase differences and the multiple stator voltages, and a second phase difference calculation unit that calculates the second phase difference based on the first phase difference and the skew angle corresponding to the other cross-section, and obtains the rotor magnetic flux corresponding to the first phase difference as the first rotor magnetic flux by referring to the rotor magnetic flux map and obtains the rotor magnetic flux corresponding to the second phase difference as the second rotor The rotor flux is acquired as the first rotor flux, and by referring to the stator voltage map, the stator voltage corresponding to the first phase difference is acquired as the first stator voltage, and the stator voltage corresponding to the second phase difference is acquired as the second stator voltage, the average value of the first and second rotor fluxes is calculated, and the average value of the first and second stator voltages is calculated, and the first inductance is calculated by substituting the average value of the first and second rotor fluxes and the average value of the first and second stator voltages into the voltage equation corresponding to the induction motor. The second inductance calculation unit may be configured to acquire the rotor flux corresponding to the first phase difference as the first rotor flux by referring to the rotor flux map, acquire the stator voltage corresponding to the first phase difference as the first stator voltage by referring to the stator voltage map, and calculate the second inductance by substituting the first rotor flux and the first stator voltage into the voltage equation.

[0011] Furthermore, the first inductance calculation unit may be configured to include a first phase difference calculation unit that calculates the first rotor current and the first phase difference using the first stator current and slip frequency by two-dimensional magnetic field analysis, and calculate the third rotor magnetic flux and third stator voltage corresponding to the first phase difference in the first stator current and the first rotor current using three-dimensional magnetic field analysis, and calculate the first inductance by substituting the third rotor magnetic flux and third stator voltage into the voltage equation corresponding to the induction motor, and the second inductance calculation unit may be configured to calculate the second inductance by substituting the first rotor magnetic flux and first stator voltage into the voltage equation.

[0012] Furthermore, the map creation unit may be configured to calculate the multiple rotor magnetic fluxes and the multiple stator voltages using the effective value or fundamental wave of the first rotor current.

[0013] Furthermore, the map creation unit may be configured to create a rotor magnetic flux map showing the correspondence between the multiple phase differences, the multiple rotor magnetic fluxes, and the rotor position, and to create a stator voltage map showing the correspondence between the multiple phase differences, the multiple stator voltages, and the rotor position.

[0014] Furthermore, one embodiment of the present invention is a parameter calculation method for calculating the parameters of a skewed induction motor in a parameter calculation device equipped with a processor, wherein the processor calculates a first inductance based on the phase difference between the stator current and rotor current corresponding to a reference cross section and other cross sections in the axial normal direction of the skewed induction motor, calculates a second inductance based on the phase difference between the stator current and rotor current corresponding to the reference cross section, calculates the rate of increase or decrease of the first inductance with respect to the second inductance, calculates a third inductance based on the phase difference between the stator current and rotor current corresponding to the reference cross section using two-dimensional magnetic field analysis and a voltage equation corresponding to the induction motor, and takes the result of multiplying the third inductance by the rate of increase or decrease as the corrected inductance.

[0015] Furthermore, a program in one embodiment of the present invention is a program for calculating the parameters of a skewed induction motor in a parameter calculation device equipped with a processor, wherein the program causes the processor to perform the following steps: calculate a first inductance based on the phase difference between the stator current and rotor current corresponding to a reference cross section and other cross sections in the axial normal direction of the skewed induction motor, respectively; calculate a second inductance based on the phase difference between the stator current and rotor current corresponding to the reference cross section; calculate the rate of increase or decrease of the first inductance with respect to the second inductance; calculate a third inductance based on the phase difference between the stator current and rotor current corresponding to the reference cross section using two-dimensional magnetic field analysis and a voltage equation corresponding to the induction motor; and take the result of multiplying the third inductance by the rate of increase or decrease as the corrected inductance. [Effects of the Invention]

[0016] According to the present invention, the parameters of an induction motor with skew can be calculated in a relatively short time and with high accuracy. [Brief explanation of the drawing]

[0017] [Figure 1] This figure shows a parameter calculation device in an embodiment. [Figure 2] This figure shows the phase difference between the stator current and rotor current corresponding to three different cross-sections in the axial normal direction of an induction motor with skew. [Figure 3] This figure shows the parameter calculation device in the embodiment. [Figure 4] This is a flowchart showing the parameter calculation method in the example. [Figure 5] This is a diagram illustrating the parameter calculation method. [Figure 6] This is a diagram illustrating the parameter calculation method. [Figure 7] This is a diagram illustrating the parameter calculation method. [Figure 8] This is a diagram illustrating the parameter calculation method. [Figure 9] This is a diagram illustrating the parameter calculation method. [Figure 10] This is a diagram illustrating the parameter calculation method. [Figure 11] This diagram shows the hardware configuration of the parameter calculation device. [Figure 12] This figure shows other examples of rotor flux maps and stator voltage maps. [Figure 13] This figure shows another example of the first inductance calculation unit. [Modes for carrying out the invention]

[0018] The details of the embodiments will be described below with reference to the drawings.

[0019] Figure 1 shows a parameter calculation device in an embodiment.

[0020] The parameter calculation device 1 shown in Figure 1 calculates the stator's self-inductance Ls, the rotor's self-inductance Lr, and the mutual inductance M between the stator and rotor as parameters for an induction motor with skew, and comprises a first inductance calculation unit 2, a second inductance calculation unit 3, an increase / decrease rate calculation unit 4, a parameter calculation unit 5, and a correction unit 6.

[0021] The first inductance calculation unit 2 calculates the first inductance (self-inductance Ls', rotor self-inductance Lr', mutual inductance M') taking skew into account, based on the phase difference between the stator current and rotor current corresponding to the reference cross section in the axial normal direction of the induction motor and other cross sections, respectively.

[0022] The second inductance calculation unit 3 calculates the second inductance (self-inductance Ls'', self-inductance Lr'', mutual inductance M'') without considering skew, based on the phase difference between the stator current and rotor current corresponding to the reference cross section.

[0023] The increase / decrease rate calculation unit 4 calculates the increase / decrease rate R of the first inductance relative to the second inductance.

[0024] The parameter calculation unit 5 uses two-dimensional magnetic field analysis and voltage equations corresponding to induction motors to calculate the uncorrected third inductance (self-inductance Ls'', self-inductance Lr'', mutual inductance M'') based on the phase difference between the stator current and rotor current corresponding to the reference cross section.

[0025] The correction unit 6 takes the result of multiplying the third inductance by the increase / decrease rate R as the corrected inductance (self-inductance Ls, self-inductance Lr, mutual inductance M).

[0026] In the parameter calculation device 1 of the embodiment, the principle that the phase difference between the stator current and rotor current in each cross section in the axial normal direction of an induction motor with skew is shifted by the skew angle is used to calculate the inductance with the same accuracy as three-dimensional magnetic field analysis, using two-dimensional magnetic field analysis, which has a shorter analysis time than three-dimensional magnetic field analysis.

[0027] Figure 2 shows the phase difference between the stator current and rotor current corresponding to three different cross-sections in the axial normal direction of an induction motor with skew. In Figure 2, the stator and a portion of the rotor are shown to make it easier to understand that the rotor is skewed. In Figure 2, the stator and rotor cross-sections in the axial normal direction near the axial center of the induction motor are defined as the middle plane (reference cross-section), the stator and rotor cross-sections in the axial normal direction above the middle plane (other cross-sections) are defined as the upper plane, and the stator and rotor cross-sections in the axial normal direction below the middle plane (other cross-sections) are defined as the lower plane. The reference cross-section may be the upper plane or the lower plane, and is not particularly limited. For example, if the upper plane is the reference cross-section, the middle and lower planes will be the other cross-sections. If the lower plane is the reference cross-section, the upper and middle planes will be the other cross-sections.

[0028] For example, consider a case where the phase difference between the stator current and rotor current is obtained from a three-dimensional magnetic field analysis using the stator current and slip frequency as inputs in an induction motor with skew.

[0029] In this case, the second phase difference (ΔθU) between the second stator current (idsU, iqsU) and the second rotor current (idrU, iqrU) at the top surface is smaller than the first phase difference (ΔθM) between the first stator current (idsM, iqsM) and the first rotor current (idrM, iqrM) at the middle surface. Also, the second phase difference (ΔθL) between the second stator current (idsL, iqsL) and the second rotor current (idrL, iqrL) at the bottom surface is larger than the first phase difference (ΔθM) at the middle surface. Therefore, the inductance calculated based on the first phase difference and the inductance calculated based on the second phase difference are different from each other. For example, if the stator current and rotor current flow most easily when the phase difference between the stator current and rotor current is the first phase, then the second stator current and second rotor current will flow less easily than the first stator current and first rotor current. As a result, the inductance at the top or bottom surface will be larger than the inductance at the middle surface.

[0030] Thus, in the case of an induction motor with skew, when the cross-section in the axial normal direction of the induction motor is switched from a reference cross-section to another cross-section, that is, when the skew angle is changed, the phase difference between the stator current and the rotor current changes. Therefore, the inductance calculated from the phase difference between the stator current and the rotor current also changes for each cross-section in the axial normal direction of the induction motor. Utilizing this, a first inductance calculated from the phase difference corresponding to the reference cross-section and other cross-sections in the axial normal direction of the induction motor, and a second inductance calculated from the phase difference corresponding to the reference cross-section are calculated. The rate of increase or decrease of the first inductance relative to the second inductance is calculated, and the result of multiplying the third inductance, calculated from two-dimensional magnetic field analysis and the voltage equation corresponding to the induction motor, by this rate of increase or decrease is taken as the corrected inductance. This allows the corrected inductance to be calculated with the same accuracy as the inductance calculated by three-dimensional magnetic field analysis, thereby improving the accuracy of inductance calculation. Furthermore, since the inductance is calculated using two-dimensional magnetic field analysis, the time required for inductance calculation can be reduced compared to calculating inductance using three-dimensional magnetic field analysis.

[0031] <Examples> Figure 3 shows a parameter calculation device in an embodiment. In Figure 3, components identical to those shown in Figure 1 are denoted by the same reference numerals.

[0032] The first inductance calculation unit 2 shown in Figure 3 comprises a first phase difference calculation unit 21, a map creation unit 22, and a second phase difference calculation unit 23.

[0033] Figure 4 is a flowchart showing the parameter calculation method in the embodiment.

[0034] First, in step S1, the first phase difference calculation unit 21 calculates the first rotor current and the first phase difference based on the first stator current and slip frequency using two-dimensional magnetic field analysis. For example, as shown in Figure 5(a), the first phase difference calculation unit 21 obtains the first rotor current (idrM, iqrM) and the first phase difference (ΔθM) by performing two-dimensional magnetic field analysis on the middle plane shown in Figure 2, with the first stator current (idsM, iqsM) and slip frequency (ωs) as inputs. Note that the stator current, rotor current, stator voltage, and rotor voltage used in this embodiment are all RMS values.

[0035] Next, in step S2 shown in Figure 4, the map creation unit 22 obtains multiple rotor magnetic fluxes and multiple stator voltages by performing a two-dimensional magnetic field analysis using the first stator current, the first rotor current, and multiple phase differences based on the first phase difference as inputs. The map creation unit 22 also obtains a rotor magnetic flux map MΦ showing the correspondence between the multiple phase differences and the multiple rotor magnetic fluxes, and creates a stator voltage map Mv showing the correspondence between the multiple phase differences and the multiple stator voltages.

[0036] For example, as shown in Figure 5(b), the map creation unit 22 calculates a first stator current (idsM, iqsM), a first rotor current (idrM, iqrM), and a plurality of phase differences (ΔθM) based on the first phase difference (ΔθM). +2 ΔθM +1 ΔθM, ΔθM-1 , ΔθMM -2 ) is used as an input to perform two-dimensional magnetic field analysis, obtaining a plurality of rotor fluxes (「Φ2d +2 , Φ2q +2 」, 「Φ2d +1 , Φ2q +1 」, 「Φ2d0, Φ2q0」, 「Φ2d -1 , Φ2q -1 」, 「Φ2d -2 , Φ2q -2 」) and a plurality of stator voltages (「Vds +2 , Vqs +2 」, 「Vds +1 , Vqs +1 」, 「Vds0, Vqs0」, 「Vds -1 , Vqs -1 」, 「Vds -2 , Vqs -2 」).

[0037] In this case, as shown in FIG. 5(c), the map creation unit 22 associates the phase difference (ΔθM +2 ) with the rotor flux (Φ2d +2 , Φ2q +2 ), associates the phase difference (ΔθM +1 ) with the rotor flux (Φ2d +1 , Φ2q +1 ), associates the phase difference (ΔθM) with the rotor flux (Φ2d0, Φ2q0), associates the phase difference (ΔθM -1 ) with the rotor flux (Φ2d -1 , Φ2q -1 ), and associates the phase difference (ΔθM -2 ) with the rotor flux (Φ2d -2 , Φ2q -2 ) to create a rotor flux map MΦ.

[0038] Also, as shown in FIG. 5(d), the map creation unit 22 associates the phase difference (ΔθM +2 ) with the stator voltage (Vds +2 , Vqs +2 ), associates the phase difference (ΔθM +1 ) with the stator voltage (Vds +1 , Vqs +1) are associated with the phase difference (ΔθM) and the stator voltage (Vds0, Vqs0), and the phase difference (ΔθM -1 ) and stator voltage (Vds -1 ,Vqs -1 ) is associated with the phase difference (ΔθM -2 ) and stator voltage (Vds -2 ,Vqs -2 Create a stator voltage map Mv that corresponds to ).

[0039] Next, in step S3 shown in Figure 4, the second phase difference calculation unit 23 calculates the second phase difference based on the first phase difference and the skew angle corresponding to the other cross-section.

[0040] For example, as shown in Figure 5(e), the second phase difference calculation unit 23 calculates the phase difference between the stator current and the rotor current (ΔθM) which is determined by the first phase difference (ΔθM) and the skew angle from the middle surface to the top surface. +2 By adding this to the above, the second phase difference (ΔθM) is obtained, which is the phase difference between the stator current and the rotor current at the top surface. +2 )

[0041] Furthermore, the second phase difference calculation unit 23 calculates the second phase difference (ΔθM), which is the phase difference between the stator current and the rotor current at the middle surface, by adding the first phase difference (ΔθM) and the phase difference (0) between the stator current and the rotor current, which is determined by the skew angle from one middle surface to the other.

[0042] Furthermore, the second phase difference calculation unit 23 calculates the phase difference between the stator current and the rotor current (ΔθM), which is determined by the first phase difference (ΔθM) and the skew angle from the middle surface to the bottom surface. -2 By adding this, the second phase difference (ΔθM) is obtained, which is the phase difference between the stator current and the rotor current at the bottom surface. -2 )

[0043] Next, in step S4 shown in Figure 4, the first inductance calculation unit 2 refers to the rotor magnetic flux map and obtains the rotor magnetic flux corresponding to the first phase difference as the first rotor magnetic flux and the rotor magnetic flux corresponding to the second phase difference as the second rotor magnetic flux. It also refers to the stator voltage map and obtains the stator voltage corresponding to the first phase difference as the first stator voltage and the stator voltage corresponding to the second phase difference as the second stator voltage. Furthermore, the first inductance calculation unit 2 calculates the average value of the first and second rotor magnetic fluxes and the average value of the first and second stator voltages, and calculates the first inductance by substituting the average value of the first and second rotor magnetic fluxes and the average value of the first and second stator voltages into the voltage equation corresponding to the induction motor.

[0044] For example, as shown in Figure 6, the first inductance calculation unit 2 refers to the rotor magnetic flux map MΦ shown in Figure 5(c) and calculates the second phase difference (ΔθM) on the upper surface. +2 ) Corresponding rotor magnetic flux (Φ2d +2 ,Φ2q +2 The second rotor magnetic flux is determined as (Φ2d0, Φ2q0), and the rotor magnetic flux (Φ2d0, Φ2q0) corresponding to the first phase difference (ΔθM) on the middle surface is determined as the first rotor magnetic flux, and the second phase difference (ΔθM) on the bottom surface is determined as (Φ2d0, Φ2q0). -2 ) Corresponding rotor magnetic flux (Φ2d -2 ,Φ2q -2 ) is determined as the magnetic flux of the second rotor.

[0045] Furthermore, the first inductance calculation unit 2 refers to the stator voltage map Mv shown in Figure 5(d) and calculates the second phase difference (ΔθM) on the upper surface. +2 ) corresponding stator voltage (Vds +2 ,Vqs +2 The second stator voltage is determined as (ΔθM), and the stator voltage (Vds0, Vqs0) corresponding to the first phase difference (ΔθM) on the middle surface is determined as the first stator voltage, and the second phase difference (ΔθM) on the bottom surface is determined as (ΔθM) -2 ) corresponding stator voltage (Vds -2 ,Vqs -2 ) is calculated as the second stator voltage.

[0046] Furthermore, the first inductance calculation unit 2 calculates the rotor magnetic flux (Φ2d +2 ,Φ2q +2 ) and rotor magnetic flux (Φ2d0, Φ2q0) and rotor magnetic flux (Φ2d -2 ,Φ2q -2 The rotor magnetic flux (Φ2dA, Φ2qA), which is the average value of ), is calculated, and the stator voltage (Vds +2 ,Vqs +2 ) and stator voltage (Vds0, Vqs0) and stator voltage (Vds -2 ,Vqs -2 The stator voltage (VdsA, VqsA), which is the average value of ), is calculated.

[0047] Furthermore, the first inductance calculation unit 2 calculates the self-inductance Ls, rotor self-inductance Lr, and mutual inductance M by substituting rotor magnetic flux (Φ2dA, Φ2qA) and stator voltage (VdsA, VqsA) as rotor magnetic flux (Φ2d, Φ2q) and stator voltage (Vds, Vqs) into the voltage equations corresponding to the induction motor shown in Equations 1 and 2 below, and uses these as the first inductance (self-inductance Ls', self-inductance Lr', and mutual inductance M') with skew taken into account. Note that ids is the stator d-axis current, iqs is the stator q-axis current, idr is the rotor d-axis current, iqr is the rotor q-axis current, ω is the power supply angular velocity, and Rs is the stator winding resistance.

[0048]

number

[0049]

number

[0050] Specifically, the first inductance calculation unit 2 calculates the first rotor magnetic flux and first stator voltage corresponding to the first stator current, first rotor current, and first phase difference on the middle surface, and calculates the second rotor magnetic flux and second stator voltage corresponding to the second stator current, second rotor current, and second phase difference on the upper or lower surface, and calculates the first inductance based on the first and second rotor magnetic fluxes and the first and second stator voltages.

[0051] Next, in step S5 shown in Figure 4, the second inductance calculation unit 3 refers to the rotor magnetic flux map to obtain the rotor magnetic flux corresponding to the first phase difference as the first rotor magnetic flux, refers to the stator voltage map to obtain the stator voltage corresponding to the first phase difference as the first stator voltage, and calculates the second inductance by substituting the first rotor magnetic flux and the first stator voltage into the voltage equation corresponding to the induction motor.

[0052] For example, as shown in Figure 7, the second inductance calculation unit 3 refers to the rotor magnetic flux map MΦ shown in Figure 5(c) and determines the rotor magnetic flux (Φ2d0, Φ2q0) corresponding to the first phase difference (ΔθM) in the middle plane as the first rotor magnetic flux.

[0053] Furthermore, the second inductance calculation unit 3 refers to the stator voltage map Mv shown in Figure 5(d) and determines the stator voltage (Vds0, Vqs0) corresponding to the first phase difference (ΔθM) in the middle plane as the first stator voltage.

[0054] Furthermore, the second inductance calculation unit 3 calculates the self-inductance Ls, self-inductance Lr, and mutual inductance M by substituting the rotor magnetic flux (Φ2d0, Φ2q0) and stator voltage (Vds0, Vqs0) as rotor magnetic flux (Φ2d, Φ2q) and stator voltage (Vds, Vqs) into the voltage equations shown in equations 1 and 2 above, and uses these as the second inductance (self-inductance Ls'', self-inductance Lr'', and mutual inductance M'') without considering skew.

[0055] In other words, the second inductance calculation unit 3 calculates the second inductance based on the first rotor magnetic flux and the first stator voltage.

[0056] Next, in step S6 shown in Figure 4, the increase / decrease rate calculation unit 4 calculates the increase / decrease rate of the first inductance with respect to the second inductance.

[0057] For example, as shown in Figure 8(a), the increase / decrease rate calculation unit 4 takes the result of dividing the self-inductance Ls' by the self-inductance Ls'' as the increase / decrease rate RLs corresponding to the stator's self-inductance.

[0058] Furthermore, as shown in Figure 8(b), the increase / decrease rate calculation unit 4 takes the result of dividing the self-inductance Lr' by the self-inductance Lr'' as the increase / decrease rate RLr corresponding to the rotor's self-inductance.

[0059] Furthermore, as shown in Figure 8(c), the increase / decrease rate calculation unit 4 takes the result of dividing the mutual inductance M' by the mutual inductance M'' as the increase / decrease rate RM corresponding to the mutual inductance between the stator and the rotor.

[0060] Next, in step S7 shown in Figure 4, the parameter calculation unit 5 uses two-dimensional magnetic field analysis and voltage equations corresponding to induction motors to calculate the uncorrected third inductance (self-inductance Ls, rotor self-inductance Lr, mutual inductance M) based on the phase difference with the stator current and rotor current corresponding to the reference cross section.

[0061] For example, as shown in Figure 9, the parameter calculation unit 5 performs a two-dimensional magnetic field analysis using the first stator current (idsM, iqsM), the first rotor current (idrM, iqrM) and the first phase difference (ΔθM) obtained in step S1 as inputs to obtain the first rotor magnetic flux (Φ2dM, Φ2qM) and the first stator voltage (VdsM, VqsM).

[0062] Furthermore, the parameter calculation unit 5 calculates the self-inductance Ls, self-inductance Lr, and mutual inductance M by substituting the rotor magnetic flux (Φ2d, Φ2q) and stator voltage (Vds, Vqs) as the first rotor magnetic flux (Φ2dM, Φ2qM) and the first stator voltage (VdsM, VqsM) into the voltage equations shown in equations 1 and 2 above, and uses these as the third inductance (stator self-inductance Ls'', self-inductance Lr'', and mutual inductance M'').

[0063] Then, in step S8 shown in Figure 4, the correction unit 6 takes the result of multiplying the third inductance by the increase / decrease rate R as the corrected inductance (self-inductance Ls, rotor self-inductance Lr, mutual inductance M).

[0064] For example, as shown in Figure 10(a), the correction unit 6 takes the result of multiplying the self-inductance Ls'' by the increase / decrease rate RLs as the corrected self-inductance Ls.

[0065] Furthermore, as shown in Figure 10(b), the correction unit 6 takes the self-inductance Lr'' multiplied by the increase / decrease rate RLr as the corrected self-inductance Lr.

[0066] Furthermore, as shown in Figure 10(c), the correction unit 6 takes the result of multiplying the mutual inductance M'' by the increase / decrease rate RM as the corrected mutual inductance M.

[0067] If the input values, the first stator current and slip frequency, are changed to other values, steps S1 to S8 shown in Figure 4 are repeated for the changed first stator current and slip frequency.

[0068] In the parameter calculation device 1 of the embodiment, the first inductance (self-inductance Ls', self-inductance Lr', mutual inductance M') is calculated using the first phase difference corresponding to the middle surface in the axial normal direction of the induction motor and the second phase differences corresponding to the top and bottom surfaces, and the second inductance (self-inductance Ls'', self-inductance Lr'', mutual inductance M'') is calculated using the first phase difference corresponding to the middle surface. The rate of increase or decrease R of the first inductance relative to the second inductance is calculated, and the result of multiplying the rate of increase or decrease R by the third inductance (self-inductance Ls'''', self-inductance Lr'''', mutual inductance M'''') calculated by two-dimensional magnetic field analysis and voltage equations is taken as the corrected inductance (self-inductance Ls, self-inductance Lr, mutual inductance M). As a result, the corrected inductance can be calculated with the same accuracy as the inductance calculated by three-dimensional magnetic field analysis, thereby improving the accuracy of inductance calculation. Furthermore, since the system calculates inductance using two-dimensional magnetic field analysis, the time required to calculate inductance can be reduced compared to when using three-dimensional magnetic field analysis.

[0069] <Hardware configuration of parameter calculation device 1> Figure 11 shows an example of the hardware configuration of an information processing device (computer) used as a parameter calculation device 1.

[0070] The information processing device 100 shown in Figure 11 comprises a processor 101, memory 102, storage device 103, reader 104, communication interface 106, and input / output interface 107. These components are connected to each other, for example, via a bus 108.

[0071] The processor 101 may be, for example, a single processor, a multi-processor, or a multi-core processor. The processor 101 provides the functionality of the parameter calculation device 1 by using the memory 102 to execute a program that describes, for example, the procedure for the parameter calculation method described above.

[0072] Memory 102 is, for example, a semiconductor memory and may include a RAM area and a ROM area. Storage device 103 is, for example, a semiconductor memory such as a hard disk or flash memory, or an external storage device. RAM is an abbreviation for Random Access Memory, and ROM is an abbreviation for Read Only Memory.

[0073] The reader 104 accesses the removable storage medium 105 according to instructions from the processor 101. The removable storage medium 105 can be implemented as, for example, a semiconductor device (such as a USB memory stick), a medium in which information is input / output by magnetic action (such as a magnetic disk), or a medium in which information is input / output by optical action (such as a CD-ROM or DVD). Note that USB is an abbreviation for Universal Serial Bus. CD is an abbreviation for Compact Disc. DVD is an abbreviation for Digital Versatile Disk.

[0074] The communication interface 106 sends and receives data via the communication network, for example, in accordance with instructions from the processor 101.

[0075] The input / output interface 107 is, for example, a keyboard, a pointing device, etc., and is used for inputting instructions or information from an operator or user.

[0076] Each program executed by processor 101 is provided, for example, in the following form:

[0077] (1) It is pre-installed on the storage device 103.

[0078] (2) Provided by a removable storage medium 105.

[0079] (3) Provided from a server such as a program server to the communication interface 106 via a communication network.

[0080] The hardware configuration of the information processing device 100 is illustrative, and the embodiments are not limited thereto. For example, some or all of the functions of the above-described functional units may be implemented as hardware such as an FPGA and an SoC. FPGA is an abbreviation for Field Programmable Gate Array, and SoC is an abbreviation for System-on-a-chip.

[0081] Furthermore, the present invention is not limited to the embodiments described above, and various improvements and modifications are possible without departing from the spirit of the invention.

[0082] <Example 1> If multiple input values ​​for the first stator current and slip frequency are available, steps S1 to S8 shown in Figure 4 may be performed simultaneously for each of these first stator currents and slip frequencies.

[0083] <Modification 2> In step S2 shown in Figure 4, when inputting the first rotor current to the two-dimensional magnetic field analysis, the fundamental wave of the first rotor current calculated in step S1 may be input.

[0084] <Variation 3> In step S2 shown in Figure 4, when calculating the rotor flux map and stator voltage map, rotor position information may be included, as shown in the rotor flux map MΦ' and stator voltage map Mv' in Figure 12. When configured in this way, spatial harmonic components can be included in the rotor current, stator voltage, and rotor voltage dealt with in the embodiment.

[0085] <Modification 4> In step S4 shown in Figure 4, when calculating the first inductance, the rotor magnetic flux (Φ2dA, Φ2qA) and stator voltage (VdsA, VqsA) may be determined by performing a three-dimensional magnetic field analysis using the first stator current (idsM, iqsM), the first rotor current (idrM, iqrM), and the first phase difference (ΔθM) as inputs, as shown in Figure 13. In this configuration, step S3 shown in Figure 4 can be omitted.

[0086] <Modification 5> When calculating the rate of increase or decrease, by preparing the results of a two-dimensional forced current analysis at a phase greater than or equal to the skew amount in advance, it is possible to calculate parameters with varying skew amounts without performing any analysis. [Explanation of symbols]

[0087] 1. Parameter calculation device 2. First Inductance Calculation Unit 3. Second Inductance Calculation Unit 4. Increase / Decrease Rate Calculation Unit 5. Parameter calculation unit 6. Correction Unit 21 First phase difference calculation section 22 Map Creation Department 23 Second phase difference calculation section

Claims

1. A first inductance calculation unit calculates the first inductance based on the phase difference between the stator current and rotor current corresponding to a reference cross section in the axial normal direction and other cross sections of an induction motor having skew, A second inductance calculation unit calculates a second inductance based on the phase difference between the stator current and the rotor current corresponding to the aforementioned reference cross-section, A unit for calculating the rate of increase or decrease of the first inductance relative to the second inductance, A parameter calculation unit calculates a third inductance based on the phase difference between the stator current and rotor current corresponding to the reference cross-section, using two-dimensional magnetic field analysis and the voltage equation corresponding to the induction motor. A correction unit that takes the result of multiplying the third inductance by the increase / decrease rate as the corrected inductance, A parameter calculation device equipped with the following features.

2. A parameter calculation device according to claim 1, The first inductance calculation unit calculates the first stator current, the first rotor current, and the first rotor magnetic flux and first stator voltage corresponding to the first phase difference between the first stator current and the first rotor current in the reference cross section, and calculates the second stator current, the second rotor current, and the second rotor magnetic flux and second stator voltage corresponding to the second phase difference between the second stator current and the second rotor current in the other cross section, and calculates the first inductance based on the first and second rotor magnetic fluxes and the first and second stator voltages. The second inductance calculation unit calculates the second inductance based on the first rotor magnetic flux and the first stator voltage. A parameter calculation device characterized by the following features.

3. A parameter calculation device according to claim 2, The first inductance calculation unit is: A first phase difference calculation unit calculates the first rotor current and the first phase difference from the first stator current and slip frequency by two-dimensional magnetic field analysis, A map creation unit that, using two-dimensional magnetic field analysis, calculates multiple rotor magnetic fluxes corresponding to multiple phase differences with respect to the first phase difference in the first stator current and the first rotor current, calculates multiple stator voltages corresponding to the multiple phase differences, creates a rotor magnetic flux map showing the correspondence between the multiple phase differences and the multiple rotor magnetic fluxes, and creates a stator voltage map showing the correspondence between the multiple phase differences and the multiple stator voltages, A second phase difference calculation unit calculates the second phase difference based on the first phase difference and the skew angle corresponding to the other cross-section, Equipped with, By referring to the rotor flux map, the rotor flux corresponding to the first phase difference is acquired as the first rotor flux, and the rotor flux corresponding to the second phase difference is acquired as the second rotor flux. Referring to the stator voltage map, the stator voltage corresponding to the first phase difference is acquired as the first stator voltage, and the stator voltage corresponding to the second phase difference is acquired as the second stator voltage. The average values ​​of the first and second rotor magnetic fluxes are calculated, and the average values ​​of the first and second stator voltages are calculated. The first inductance is calculated by substituting the average values ​​of the first and second rotor magnetic fluxes and the average values ​​of the first and second stator voltages into the voltage equation corresponding to the induction motor. The second inductance calculation unit is: By referring to the rotor flux map, the rotor flux corresponding to the first phase difference is acquired as the first rotor flux. By referring to the stator voltage map, the stator voltage corresponding to the first phase difference is obtained as the first stator voltage. The second inductance is calculated by substituting the first rotor magnetic flux and the first stator voltage into the voltage equation. A parameter calculation device characterized by the following features.

4. A parameter calculation device according to claim 2, The first inductance calculation unit includes a first phase difference calculation unit that calculates the first rotor current and the first phase difference using the first stator current and slip frequency by two-dimensional magnetic field analysis. Using three-dimensional magnetic field analysis, the third rotor magnetic flux and third stator voltage corresponding to the first phase difference are calculated for the first stator current and the first rotor current, and the first inductance is calculated by substituting the third rotor magnetic flux and third stator voltage into the voltage equation corresponding to the induction motor. The second inductance calculation unit is: The second inductance is calculated by substituting the first rotor magnetic flux and the first stator voltage into the voltage equation. A parameter calculation device characterized by the following features.

5. A parameter calculation device according to claim 3, The map creation unit calculates the multiple rotor magnetic fluxes and the multiple stator voltages using the effective value or fundamental wave of the first rotor current. A parameter calculation device characterized by the following features.

6. A parameter calculation device according to claim 3, The map creation unit creates a rotor magnetic flux map showing the correspondence between the multiple phase differences, the multiple rotor magnetic fluxes, and the position of the rotor of the induction motor, and also creates a stator voltage map showing the correspondence between the multiple phase differences, the multiple stator voltages, and the position of the rotor of the induction motor. A parameter calculation device characterized by the following features.

7. A parameter calculation method for calculating the parameters of an induction motor having skew, in a parameter calculation device equipped with a processor, The aforementioned processor, The first inductance is calculated based on the phase difference between the stator current and rotor current corresponding to the reference cross section in the axial normal direction and other cross sections of an induction motor with skew. Based on the phase difference between the stator current and rotor current corresponding to the aforementioned reference cross-section, the second inductance is calculated. The rate of increase or decrease of the first inductance relative to the second inductance is calculated, Using two-dimensional magnetic field analysis and the voltage equation corresponding to the induction motor, the third inductance is calculated based on the phase difference between the stator current and rotor current corresponding to the reference cross-section. The corrected inductance is obtained by multiplying the third inductance by the increase / decrease rate. A parameter calculation method characterized by the following:

8. A program for calculating the parameters of an induction motor having skew, in a parameter calculation device equipped with a processor, The aforementioned processor, A step of calculating the first inductance based on the phase difference between the stator current and rotor current corresponding to a reference cross section in the axial normal direction and other cross sections of an induction motor having skew, The steps include: calculating the second inductance based on the phase difference between the stator current and the rotor current corresponding to the aforementioned reference cross-section; A step of calculating the rate of increase or decrease of the first inductance with respect to the second inductance, The steps include: calculating the third inductance based on the phase difference between the stator current and rotor current corresponding to the reference cross-section, using two-dimensional magnetic field analysis and the voltage equation corresponding to the induction motor; The steps include: multiplying the third inductance by the increase / decrease rate to obtain the corrected inductance; A program to execute.

Images