Motor control device

Abstract

To shorten the time required for estimating a position of a rotor of a motor in a control device for a motor which estimates the position of the rotor using a high frequency current included in current flowing to the motor.SOLUTION: A control device 1 includes: an inverter circuit 2; an estimation unit 8 for estimating a position of a rotor of a motor M using a polarity of the rotor while determining the polarity; a current conversion unit 7; a current command value output unit 11; a voltage command value calculation unit 14; a superposing unit 15; and a voltage command value conversion unit 16. The estimation unit 8 calculates an evaluation value eh including a magnetic saturation component Ld1 using a high frequency current iγh included in a d-axis current Id and determines the polarity of the rotor in accordance with a code of the evaluation value eh.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for controlling the operation of an electric motor. [Background technology]

[0002] There is a motor control device that estimates the rotor position of the motor with 180-degree ambiguity using a high-frequency current contained in the current flowing through the motor, and then determines the polarity of the rotor based on the magnitude relationship of the current that changes by alternately superimposing a positive pulse voltage and a negative pulse voltage on a voltage command value, and determines the rotor position using the determined polarity. Related technology is described in Patent Document 1.

[0003] As described above, the control device is configured to tentatively estimate the rotor position, determine the polarity of the rotor, and then determine the rotor position using the determined polarity, so there is a concern that the time required to estimate the rotor position may be relatively long. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-171798 A Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one aspect of the present invention is to shorten the time it takes to estimate the rotor position in an electric motor control device that estimates the rotor position of a motor using a high-frequency current contained in a current flowing through the motor. [Means for solving the problem]

[0006] a current command value output unit that outputs a d-axis current command value and a q-axis current command value according to a rotation speed difference between a rotation speed of the rotor and a rotation speed command value; a voltage command value calculation unit that calculates a d-axis voltage command value so as to reduce a difference between the d-axis current and the d-axis current command value, and calculates a q-axis voltage command value so as to reduce a difference between the q-axis current and the q-axis current command value; a superposition unit that superimposes a superposition voltage having a higher frequency than the d-axis voltage command value on the d-axis voltage command value; and a voltage command value conversion unit that converts the d-axis voltage command value output from the superposition unit and the q-axis voltage command value output from the voltage command value calculation unit into the voltage command value using the position.

[0007] The estimation unit obtains an evaluation value including a change due to magnetic saturation of a d-axis inductance of the motor by using a high-frequency current included in the d-axis current, and determines the polarity of the rotor according to a sign of the evaluation value.

[0008] For example, when the evaluation value is negative, that is, when the d-axis inductance is relatively small, it can be determined that the direction of the magnetic pole generated by the d-axis current and the direction of the magnetic pole generated by the permanent magnet are the same direction because magnetic saturation occurs in the motor, and it can be determined that no error occurs between the estimated position and the actual position. On the other hand, when the evaluation value is positive, that is, when the d-axis inductance is relatively large, it can be determined that the direction of the magnetic pole generated by the d-axis current and the direction of the magnetic pole generated by the permanent magnet are different directions because magnetic saturation does not occur in the motor, and it can be determined that an error of 180 degrees occurs between the estimated position and the actual position. In this way, the evaluation value including the change due to magnetic saturation of the d-axis inductance of the motor is obtained using the high-frequency current contained in the d-axis current, and the presence or absence of an error between the estimated position and the actual position, that is, the polarity of the rotor, can be determined according to the sign of the evaluation value.

[0009] Furthermore, since the rotor position is estimated while determining the rotor polarity, the time required to estimate the rotor position can be shortened compared to a configuration in which the rotor position is tentatively estimated, the rotor polarity is determined, and the rotor position is confirmed using the determined polarity.

[0010] The estimation unit estimates a high-frequency current included in the d-axis current as i γh The amplitude of the superimposed voltage is V h and the angular frequency of the superimposed voltage is ω h Let the d-axis inductance of the motor be L d Let the q-axis inductance of the motor be L q And L d0 =(L d +L q ) / 2, and L d1 =(L d -L q ) / 2, and the d-axis current is i d Let i d =i h sinω h t, and the high frequency current is i γhIn this case, the frequency component of the superimposed voltage, sinω, is demodulated into the high frequency current. h By multiplying t, the following equation 1 is obtained, and the AC component (1-cos2ω h By removing the sinω h The following formula 4 may be obtained by multiplying by t, and a moving average filter may be used to extract a direct current component from the following formula 4 to obtain the following formula 5 as the evaluation value.

[0011]

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[0012]

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[0016] The estimation unit may be configured to include a medium to high speed range position estimation unit that estimates a position of the rotor using an extended induced voltage excited by superimposing the superimposed voltage on the d-axis voltage command value, a low speed range position estimation unit that estimates a position of the rotor using a high frequency current included in the d-axis current, a polarity determination unit that sets a position error between the position estimated by the medium to high speed range position estimation unit and the low speed range position estimation unit and an actual position to 0 degrees when the evaluation value is negative, and sets the position error to 180 degrees when the evaluation value is positive, and a position estimation unit that sets a result of adding the position error determined by the polarity determination unit to a weighted average of the position estimated by the medium to high speed range position estimation unit and the position estimated by the low speed range position estimation unit, as a position used in the current conversion unit and the voltage command value conversion unit.

[0017] The position estimation unit may be configured to increase the weight corresponding to the position estimated by the low speed range position estimation unit as the rotation speed of the rotor decreases, and the superposition unit may be configured to increase the amplitude of the superimposed voltage as the rotation speed of the rotor decreases.

[0018] As a result, since the rotor rotation speed becomes relatively small, the extended induced voltage used in the medium- to high-speed range position estimation unit becomes relatively small. Even if the estimation accuracy of the position estimated by the medium- to high-speed range position estimation unit decreases, the estimation accuracy of the position estimated by the low-speed range position estimation unit can be improved, thereby suppressing the decrease in the estimation accuracy of the position estimated by the position estimation unit. Effect of the Invention

[0019] According to the present invention, in a motor control device that estimates the position of the rotor of a motor using a high-frequency current contained in the current flowing through the motor, it is possible to reduce the time required for rotor position estimation. [Brief description of the drawings]

[0020] [Figure 1] FIG. 2 is a diagram illustrating an example of a control device for an electric motor in the first embodiment. [Diagram 2]FIG. 2 is a diagram illustrating an example of an estimation unit in the first embodiment. [Diagram 3] FIG. 11 is a diagram illustrating an example of a control device for an electric motor according to a second embodiment. [Figure 4] FIG. 11 is a diagram illustrating an example of an estimation unit in the second embodiment. [Diagram 5] 6A to 6C are diagrams illustrating another example of the overlapping portion in the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the details of the embodiment will be described with reference to the drawings.

[0022] First Embodiment FIG. 1 is a diagram illustrating an example of a control device for an electric motor in a first embodiment.

[0023] 1 controls the operation of an electric motor M mounted on a vehicle such as an electric forklift or a plug-in hybrid vehicle, and includes an inverter circuit 2 and a control circuit 3. The electric motor M is, for example, an embedded magnet motor or a surface magnet motor.

[0024] The inverter circuit 2 drives the motor M with power supplied from a power source P, and includes a capacitor C, switching elements SW1 to SW6 (for example, IGBTs (Insulated Gate Bipolar Transistors)), and current sensors Se1 and Se2. That is, one terminal of the capacitor C is connected to the positive terminal of the power source P and the collector terminals of the switching elements SW1, SW3, and SW5, and the other terminal of the capacitor C is connected to the negative terminal of the power source P and the emitter terminals of the switching elements SW2, SW4, and SW6. A connection point between the emitter terminal of the switching element SW1 and the collector terminal of the switching element SW2 is connected to a U-phase input terminal of the motor M via the current sensor Se1. A connection point between the emitter terminal of the switching element SW3 and the collector terminal of the switching element SW4 is connected to a V-phase input terminal of the motor M via the current sensor Se2. A connection point between the emitter terminal of the switching element SW5 and the collector terminal of the switching element SW6 is connected to a W-phase input terminal of the motor M.

[0025] The capacitor C smoothes the voltage output from the power source P and input to the inverter circuit 2 .

[0026] The switching element SW1 is turned on or off based on a drive signal S1 output from the control circuit 3. The switching element SW2 is turned on or off based on a drive signal S2 output from the control circuit 3. The switching element SW3 is turned on or off based on a drive signal S3 output from the control circuit 3. The switching element SW4 is turned on or off based on a drive signal S4 output from the control circuit 3. The switching element SW5 is turned on or off based on a drive signal S5 output from the control circuit 3. The switching element SW6 is turned on or off based on a drive signal S6 output from the control circuit 3. By turning on or off the switching elements SW1 to SW6, respectively, the DC voltage output from the power source P is converted into three AC voltages whose phases differ from each other by 120 degrees, and these AC voltages are applied to the U-phase, V-phase, and W-phase input terminals of the electric motor M, and the rotor of the electric motor M rotates.

[0027] The current sensor Se1 is configured with a Hall element, a shunt resistor, etc., and detects a U-phase current Iu flowing through the U-phase of the electric motor M and outputs the detected current to the control circuit 3. In addition, the current sensor Se2 is configured with a Hall element, a shunt resistor, etc., and detects a V-phase current Iv flowing through the V-phase of the electric motor M and outputs the detected current to the control circuit 3.

[0028] The control circuit 3 includes a storage unit 4, a drive circuit 5, and a calculation unit 6.

[0029] The storage unit 4 is configured with a RAM (Random Access Memory) or a ROM (Read Only Memory), etc.

[0030] The drive circuit 5 is composed of an IC (Integrated Circuit) or the like, and compares the voltage value of a carrier wave (such as a triangular wave, a sawtooth wave, or an inverse sawtooth wave) with the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* output from the calculation unit 6, and outputs drive signals S1 to S6 according to the comparison results to the gate terminals of the switching elements SW1 to SW6, respectively.

[0031] For example, when the U-phase voltage command value Vu* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S1 and a low-level drive signal S2, and when the U-phase voltage command value Vu* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S1 and a high-level drive signal S2. When the V-phase voltage command value Vv* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S3 and a low-level drive signal S4, and when the V-phase voltage command value Vv* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S3 and a high-level drive signal S4. When the W-phase voltage command value Vw* is equal to or greater than the voltage value of the carrier wave, the drive circuit 5 outputs a high-level drive signal S5 and a low-level drive signal S6, and when the W-phase voltage command value Vw* is smaller than the voltage value of the carrier wave, the drive circuit 5 outputs a low-level drive signal S5 and a high-level drive signal S6.

[0032] The calculation unit 6 is configured by a microcomputer or the like, and includes a current conversion unit 7, an estimation unit 8, a subtraction unit 9, a torque command value calculation unit 10, a current command value output unit 11, a subtraction unit 12, a subtraction unit 13, a voltage command value calculation unit 14, a superposition unit 15, and a voltage command value conversion unit 16. For example, the microcomputer executes a program stored in the storage unit 4 to configure the current conversion unit 7, the estimation unit 8, the subtraction unit 9, the torque command value calculation unit 10, the current command value output unit 11, the subtraction unit 12, the subtraction unit 13, the voltage command value calculation unit 14, the superposition unit 15, and the voltage command value conversion unit 16.

[0033] The current converter 7 determines a W-phase current Iw flowing through the W-phase of the electric motor M, using the U-phase current Iu detected by the current sensor Se1 and the V-phase current Iv detected by the current sensor Se2.

[0034] In addition, the current conversion unit 7 converts the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw into a d-axis current Id (a current component for generating a weakened field in the motor M) and a q-axis current Iq (a current component for generating torque in the motor M) using the position θ^ estimated by the estimation unit 8.

[0035] For example, the current converter 7 converts the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw into a d-axis current Id and a q-axis current Iq using a conversion matrix C1 shown in the following equation 6.

[0036]

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[0037] The currents detected by the current sensors Se1 and Se2 are not limited to the combination of the U-phase current Iu and the V-phase current Iv, but may be the combination of the V-phase current Iv and the W-phase current Iw, or the combination of the U-phase current Iu and the W-phase current Iw. When the V-phase current Iv and the W-phase current Iw are detected by the current sensors Se1 and Se2, the current converter 7 determines the U-phase current Iu using the V-phase current Iv and the W-phase current Iw. When the U-phase current Iu and the W-phase current Iw are detected by the current sensors Se1 and Se2, the current converter 7 determines the V-phase current Iv using the U-phase current Iu and the W-phase current Iw.

[0038] In addition, if the inverter circuit 2 further includes, in addition to the current sensors Se1 and Se2, a current sensor Se3 that detects the W-phase current Iw flowing through the W-phase of the motor M, the current conversion unit 7 may be configured to convert the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensors Se1 to Se3 into the d-axis current Id and the q-axis current Iq using the position θ^ estimated by the estimation unit 8.

[0039] The estimation unit 8 uses the d-axis current Id and q-axis current Iq output from the current conversion unit 7, the d-axis voltage command value Vd*' output from the superposition unit 15, and the q-axis voltage command value Vq* output from the voltage command value calculation unit 14 to determine the polarity of the rotor of the electric motor M (the error between the estimated position and the actual position), and estimates the rotor position θ^ using the polarity.

[0040] Furthermore, the estimation unit 8 estimates the rotation speed ω^ by dividing the position θ^ by a fixed time (such as the clock period of the calculation unit 6).

[0041] The subtractor 9 calculates the rotation speed difference Δω between the rotation speed command value ω* input from the outside and the rotation speed ω^ estimated by the estimator 8.

[0042] The torque command value calculation unit 10 calculates the torque command value T* by using the rotation speed difference Δω output from the subtraction unit 9. For example, the torque command value calculation unit 10 refers to information (not shown) stored in the storage unit 4, in which the rotation speed (angular frequency) of the rotor of the electric motor M and the torque of the electric motor M are associated with each other, and determines, as the torque command value T*, the torque corresponding to the rotation speed equivalent to the rotation speed difference Δω.

[0043] The current command value output unit 11 outputs a d-axis current command value Id* and a q-axis current command value Iq* using the torque command value T*. For example, the current command value output unit 11 refers to information (not shown) stored in the storage unit 4, in which the torque of the electric motor M is associated with the d-axis current command value Id* and the q-axis current command value Iq*, to determine the d-axis current command value Id* and the q-axis current command value Iq* corresponding to the torque command value T*.

[0044] That is, the current command value output unit 11 outputs a d-axis current command value Id* and a q-axis current command value Iq* based on the rotation speed difference Δω between the rotor rotation speed ω^ and the rotation speed command value ω*.

[0045] The subtraction unit 12 calculates the difference ΔId between the d-axis current command value Id* output from the current command value output unit 11 and the d-axis current Id output from the current conversion unit 7 .

[0046] The subtraction unit 13 calculates the difference ΔIq between the q-axis current command value Iq* output from the current command value output unit 11 and the q-axis current Iq output from the current conversion unit 7 .

[0047] The voltage command value calculation unit 14 calculates the d-axis voltage command value Vd* and the q-axis voltage command value Vq* by PI control using the difference ΔId output from the subtraction unit 12 and the difference ΔIq output from the subtraction unit 13. For example, the voltage command value calculation unit 14 calculates the d-axis voltage command value Vd* by calculating the following formula 7, and calculates the q-axis voltage command value Vq* by calculating the following formula 8. Note that Kp is a constant of the proportional term of the PI control, Ki is a constant of the integral term of the PI control, Lq is the q-axis inductance of the motor M, Ld is the d-axis inductance of the motor M, ω^ is the rotation speed estimated by the estimation unit 8, and Ke is an induced voltage constant.

[0048] d-axis voltage command value Vd*=Kp×difference ΔId+∫(Ki×difference ΔId)-ω^LqIq···Equation 7

[0049] q-axis voltage command value Vq* = Kp × difference ΔIq + ∫(Ki × difference ΔIq) + ω^LdId + ω^Ke Equation 8

[0050] That is, the voltage command value calculation unit 14 calculates the d-axis voltage command value Vd* so that the difference ΔId between the d-axis current Id and the d-axis current command value Id* is small, and calculates the q-axis voltage command value Vq* so that the difference ΔIq between the q-axis current Iq and the q-axis current command value Iq* is small.

[0051] The superimposing unit 15 calculates a superimposed voltage V which has a higher frequency than the d-axis voltage command value Vd* output from the voltage command value calculation unit 14. s is superimposed on the d-axis voltage command value Vd* and output as the d-axis voltage command value Vd*'. Note that the superimposed voltage V s The amplitude of V h and the superimposed voltage V s The frequency components of sinω h Let's call it t.

[0052] For example, as shown in FIG. 1, the superimposing unit 15 adds the d-axis voltage command value Vd* and the superimposed voltage Vs by the adder 151, and sets the result of this addition as the d-axis voltage command value Vd*'.

[0053] The voltage command value conversion unit 16 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into a U-phase voltage command value Vu*, a V-phase voltage command value Vv*, and a W-phase voltage command value Vw* using the position θ^ estimated by the estimation unit 8. For example, the voltage command value conversion unit 16 converts the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into the U-phase voltage command value Vu*, the V-phase voltage command value Vv*, and the W-phase voltage command value Vw* using a conversion matrix C2 shown in the following equation 9.

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[0055] FIG. 2 is a diagram illustrating an example of the estimation unit 8 in the first embodiment.

[0056] The estimation unit 8 shown in FIG. 2 includes a medium / high speed range position estimation unit 81, a low speed range position estimation unit 82, a polarity determination unit 83, a position estimation unit 84, and a rotation speed estimation unit 85.

[0057] The medium-to-high speed range position estimation unit 81 estimates the rotor position θ using the d-axis current Id and the q-axis current Iq output from the current conversion unit 7, the d-axis voltage command value Vd*' output from the superimposition unit 15, and the q-axis voltage command value Vq* output from the voltage command value calculation unit 14. HIGH Estimate.

[0058] For example, the medium-to-high speed range position estimation unit 81 may add a superimposed voltage V s The extended induced voltage e excited by superimposing HIGH The model M of the motor M, which includes the d-axis inductance Ld and the q-axis inductance Lq as parameters that can be adjusted to any value, is estimated. LdLqis shown in the following formula 10. The d-axis inductance Ld in the following formula 10 is a value estimated in advance by an experiment, a simulation, or the like. Furthermore, R is the resistance component of the motor M, p is a differential operator, ω is the angular frequency of the rotor (for example, the rotation speed ω^ calculated by the rotation speed estimation unit 85 at the previous control timing), I is the unit matrix shown in the following formula 11, and J is the unit matrix shown in the following formula 12. {(R+pLd)I-ω(Ld-Lq)J} Formula 10

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[0061] First, the medium to high speed range position estimation unit 81 calculates the voltage v α , v β And Model M LdLq The extended induced voltage e corresponds to the difference between the voltage output from α , e β In addition, the voltage v α , v β is input to the motor M, and the current i α , i β Model M LdLq In addition, the voltage v α is a voltage obtained by converting the d-axis voltage command value Vd*' output from the superimposing unit 15 into the α-axis of a fixed coordinate system corresponding to the U-phase of the U-phase, V-phase, and W-phase of the motor M. Also, the voltage v β is a voltage obtained by converting the q-axis voltage command value Vq* output from the voltage command value calculation unit 14 into the β-axis of a fixed coordinate system that is advanced by 90 degrees from the α-axis. α is a current obtained by converting the d-axis current Id output from the current converter 7 into the α-axis current. β is the current obtained by converting the q-axis current Iq output from the current converter 7 into the β-axis current. Also, the extended induced voltage e α , eβ is represented by the following formula 13.

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[0063] Next, the medium to high speed range position estimation unit 81 calculates the extended induced voltage e α , e β By applying filtering to the extended induced voltage e αω , e βω Estimate.

[0064] Then, the medium to high speed range position estimation unit 81 calculates the position θ HIGH Request.

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[0066] The low-speed region position estimation unit 82 estimates the rotor position θ using the q-axis current Iq output from the current conversion unit 7. LOW Estimate.

[0067] For example, the low speed range position estimation unit 82 detects the high frequency current i δh Using the position θ Low The high-frequency current i δh is represented by the following formula 15. 0 is set to the value shown in the following formula 16, and L 1 is set to the value shown in the following formula 17, and Δθ is set to the error between the position estimated by the medium / high speed range position estimating unit 81 and the low speed range position estimating unit 82 and the actual position.

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[0071] First, the low speed region position estimation unit 82 detects the high frequency current i δh By performing synchronous detection on the high-frequency current i δh The demodulated signal is the superimposed voltage V s Frequency component sinω h After being multiplied by t, filtering is performed using a low-pass filter.

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[0073] Next, the low speed range position estimation unit 82 performs PI control so that the position error Δθ of the above formula 18 becomes zero, thereby obtaining the rotation speed ω as shown in the following formula 19. LOW Here, Kp is a constant for the proportional term of the PI control, Ki is a constant for the integral term of the PI control, and s is a differential operator.

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[0075] Then, the low speed region position estimation unit 82 calculates the rotation speed ω LOW By integrating ^ as shown in the following equation 20, the position θ LOW Get the.

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[0077] The polarity determination unit 83 includes a multiplication unit 831, a band elimination filter (BEF) 832, a reciprocal calculation unit 833, a multiplication unit 834, a moving average filter (MAF) 835, and a position error output unit 836. γh Using the change in d-axis inductance Ld of the motor M due to magnetic saturation (magnetic saturation component L d1 ) including the evaluation value e h Calculate the evaluation value e h The position error Δθ is calculated based on the sign (negative or positive).

[0078] In addition, the high-frequency current i γh is expressed by the following formula 21. If it is assumed that the position error Δθ converges to 0 degrees or 180 degrees and cos2Δθ≈1, the following formula 21 is transformed into the following formula 22. If it is assumed that the following formula 23 holds for the d-axis inductance Ld in the following formula 22, the following formula 22 is transformed into the following formula 24. L d0 is the steady-state component of the d-axis inductance Ld, and L d1 is the change due to magnetic saturation of the d-axis inductance Ld (magnetic saturation component), and id is the d-axis current Id.

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[0083] In the polarity determination unit 83, the magnetic saturation component L is calculated from the above formula 24. d1 The formula containing the formula (formula 5 described later) is evaluated as e h The evaluation value e h The sign of the magnetic saturation component L d1 Determine whether the sign of is negative or positive.

[0084] For example, the evaluation value e h (Magnetic saturation component L d1 ) is negative, the d-axis inductance Ld on the left side of the above formula 23 becomes relatively small, so it can be determined that magnetic saturation occurs in the motor M, and that the direction of the magnetic pole generated by the d-axis current and the direction of the magnetic pole generated by the permanent magnet match each other. Therefore, since it is assumed that the position error Δθ converges to 0 degrees or 180 degrees, it can be determined that the error between the actual position and the position estimated by the medium / high speed range position estimator 81 or the low speed range position estimator 82 is 0 degrees.

[0085] On the other hand, the evaluation value e h (Magnetic saturation component L d1 ) is positive, the d-axis inductance Ld on the left side of the above formula 23 becomes relatively large, so it can be determined that no magnetic saturation has occurred in the motor M, and that the direction of the magnetic pole generated by the d-axis current and the direction of the magnetic pole generated by the permanent magnet do not match each other. Therefore, since it is assumed that the position error Δθ has converged to 0 degrees or 180 degrees, it can be determined that the error between the position estimated by the medium / high speed range position estimator 81 or the low speed range position estimator 82 and the actual position is 180 degrees.

[0086] The multiplication unit 831 multiplies the high-frequency current i γh The demodulated signal is the superimposed voltage V s Frequency component sinω h By multiplying by t, we obtain Equation 1 below.

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[0088] The band-stop filter 832 calculates the AC component (1-cos2ω h By removing t, we obtain the following equation 2. Note that id = i h sinω h Let's call it t.

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[0090] The reciprocal calculation unit 833 obtains the following equation 3 by taking the reciprocal of the above equation 2.

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[0092] The multiplier 834 multiplies the superimposed voltage V s Frequency component sinω h By multiplying by t, we obtain the following equation 4.

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[0094] The moving average filter 835 extracts the DC component from the above formula 4 to obtain the evaluation value e h As a result, we obtain the following equation 5.

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[0096] The position error output unit 836 outputs the evaluation value e h is negative, 0 degrees is output to the position estimation unit 84 as the position error Δθ, and the evaluation value e h is positive, 180 degrees is output to the position estimation unit 84 as the position error Δθ.

[0097] The position estimation unit 84 estimates the position θ HIGH and the position θ estimated by the low speed region position estimation unit 82. LOW and the position error Δθ output from position error output unit 836 to estimate the position θ̂.

[0098] For example, the position estimation unit 84 detects the position θ HIGH and position θ LOW The weighted average of the position error Δθ and the weighted average of the position error Δθ is set as the position θ^. HIGH The weight corresponding to the position θ LOW In addition, the position estimator 84 reduces the weighting corresponding to the position θ as the rotation speed ω^ calculated by the rotation speed estimator 85 decreases. HIGH The weight corresponding to the position θ LOW Increase the weight corresponding to

[0099] The rotation speed estimator 85 estimates the rotation speed ω^ by dividing the position θ^ calculated by the position estimator 84 by a fixed time (such as the clock period of the calculator 6).

[0100] In this way, according to the control device 1 of the first embodiment, the evaluation value e h When the evaluation value e is negative, that is, when the d-axis inductance Ld is relatively small, it can be determined that the direction of the magnetic pole generated by the d-axis current Id and the direction of the magnetic pole generated by the permanent magnet are the same because magnetic saturation occurs in the motor M, and it can be determined that there is no error between the position estimated by the medium / high speed range position estimator 81 or the low speed range position estimator 82 and the actual position. hWhen is positive, that is, when the d-axis inductance Ld is relatively large, it can be determined that the direction of the magnetic pole generated by the d-axis current Id and the direction of the magnetic pole generated by the permanent magnet are different from each other because magnetic saturation does not occur in the motor M, and it can be determined that an error of 180 degrees occurs between the position estimated by the medium / high speed range position estimator 81 and the low speed range position estimator 82 and the actual position. In this way, the high frequency current i γh Using the change in d-axis inductance Ld of the motor M due to magnetic saturation (magnetic saturation component L d1 ) including the evaluation value e h Calculate the evaluation value e h Depending on the sign of the signal, it is possible to determine whether there is an error between the estimated position and the actual position, i.e., the polarity of the rotor.

[0101] 2, in the control device 1 of the first embodiment, the medium to high speed region position estimating unit 81, the low speed region position estimating unit 82, and the polarity determining unit 83 are connected in parallel with each other, so that the medium to high speed region position estimating unit 81, the low speed region position estimating unit 82, and the polarity determining unit 83 can each perform processing simultaneously. Therefore, according to the control device 1 of the first embodiment, it is possible to estimate the rotor position θ^ while determining the polarity of the rotor, and it is possible to shorten the time required for estimating the rotor position compared to a configuration in which the rotor position is tentatively estimated, the rotor polarity is determined, and the rotor position is confirmed using the determined polarity.

[0102] Furthermore, according to the control device 1 of the first embodiment, compared to the case where the polarity of the rotor is determined using the extended induced voltage excited by superimposing a high-frequency current on the d-axis current command value Id*, no processing is required to obtain the extended induced voltage, and therefore the load on the calculation unit 6 can be reduced accordingly.

[0103] <Second embodiment> Fig. 3 is a diagram showing an example of a motor control device in the second embodiment. Note that the same components as those shown in Fig. 1 are given the same reference numerals, and the description thereof will be omitted.

[0104] A control device 1' shown in FIG. 3 differs from the control device 1 shown in FIG.

[0105] The estimation unit 8' uses the d-axis current Id and the q-axis current Iq output from the current conversion unit 7 to determine the polarity of the rotor of the electric motor M while estimating the rotor position θ^.

[0106] Moreover, the estimation unit 8' estimates the rotation speed ω^ by dividing the position θ^ by a fixed time (such as the clock period of the calculation unit 6).

[0107] Fig. 4 is a diagram showing an example of an estimation unit 8' in the second embodiment. Note that the same components as those shown in Fig. 2 are denoted by the same reference numerals, and the description thereof will be omitted.

[0108] 4 includes a low speed range position estimation unit 82, a polarity determination unit 83, a position estimation unit 84', and a rotation speed estimation unit 85'. Note that the control device 1' does not include the medium to high speed range position estimation unit 81 in the estimation unit 8', and is therefore suitable for an electric motor M whose rotation speed ω^ is steadily relatively low.

[0109] The position estimation unit 84' estimates the position θ LOW and the position error Δθ determined by the polarity determination unit 83 to estimate the position θ^.

[0110] For example, the position estimation unit 84′ estimates the position θ LOW The result of adding the position error Δθ to this is the position θ^.

[0111] The rotation speed estimation unit 85' estimates the rotation speed ω^ by dividing the position θ^ calculated by the position estimation unit 84' by a fixed time (such as the clock period of the calculation unit 6).

[0112] According to the control device 1' of the second embodiment, similarly to the control device 1 of the first embodiment, the rotor position θ^ is estimated while determining the polarity of the rotor. Therefore, the time required for estimating the rotor position can be shortened compared to a configuration in which the rotor position is tentatively estimated, the rotor polarity is determined, and the rotor position is confirmed using the determined polarity.

[0113] Furthermore, in the control device 1' of the second embodiment, since the medium to high speed range position estimating unit 81 is omitted in the estimating unit 8', the load on the calculating unit 6 can be reduced compared to the control device 1 of the first embodiment.

[0114] The present invention is not limited to the above-described embodiment, and various improvements and modifications are possible without departing from the gist of the present invention.

[0115] <Modification> FIG. 5 is a diagram showing another example of the overlapping unit 15 in the first embodiment.

[0116] The superimposing section 15 shown in FIG. 5 includes an adding section 151, a multiplying section 152, and an amplitude output section 153.

[0117] The amplitude output unit 153 outputs a larger amplitude V h The larger the rotation speed ω^, the closer the amplitude V h Output.

[0118] The multiplication unit 152 multiplies the frequency component sinω h t and the amplitude V output from the amplitude output unit 153 h Multiplying by and gives the superimposed voltage V s Output.

[0119] The adder 151 calculates the superimposed voltage V on the d-axis voltage command value Vd* output from the voltage command value calculator 14. s The result of the addition is output as the d-axis voltage command value Vd*'.

[0120] As a result, the rotation speed ω^ of the rotor becomes relatively small, so that the extended induced voltage e used in the medium to high speed region position estimator 81 becomes relatively small, and the position θ estimated by the medium to high speed region position estimator 81 becomes HIGH Even if the estimation accuracy of the position θ LOW Since the estimation accuracy of the position θ^ can be improved, a decrease in the estimation accuracy of the position θ^ estimated by the position estimation unit 84 can be suppressed. [Explanation of symbols]

[0121] 1, 1´ Control device 2. Inverter circuit 3 Control Circuit 4 Storage section 5 Drive circuit 6 Arithmetic section 7 Current conversion section 8 Estimation part 9. Subtraction section 10 Torque command value calculation section 11 Current command value output section 12 Subtraction section 13 Subtraction section 14 Voltage command value calculation section 15 Superimposed section 16 Voltage command value converter 81 Medium-high speed region position estimation section 82 Low speed region position estimation section 83 Polarity judgment section 84, 84´ Position estimation part 85, 85´ RPM Estimation Unit P power supply C Capacitor Se1, Se2 current sensors M electric motor

Claims

1. an inverter circuit that drives an electric motor based on a comparison result between a voltage value of the carrier wave and a voltage command value; an estimation unit that estimates a rotor position using an evaluation value including a change due to magnetic saturation of a d-axis inductance of the electric motor; a current converter for converting a current flowing through the electric motor into a d-axis current and a q-axis current using the position; a current command value output unit that outputs a d-axis current command value and a q-axis current command value according to a difference between a rotation speed of the rotor and a rotation speed command value; a voltage command value calculation unit that calculates a d-axis voltage command value so as to reduce a difference between the d-axis current and the d-axis current command value, and calculates a q-axis voltage command value so as to reduce a difference between the q-axis current and the q-axis current command value; a superimposing unit that superimposes a superimposed voltage having a higher frequency than the d-axis voltage command value on the d-axis voltage command value; a voltage command value conversion unit that converts the d-axis voltage command value output from the superimposition unit and the q-axis voltage command value output from the voltage command value calculation unit into the voltage command value by using the position; Equipped with The estimation unit is a medium to high speed range position estimating unit that estimates a position of the rotor using an extended induced voltage excited by superimposing the superimposed voltage on the d-axis voltage command value; a low speed range position estimator that estimates a position of the rotor using a high frequency current included in the d-axis current; a polarity determination unit that sets a position error between the position estimated by the medium / high speed range position estimation unit and the low speed range position estimation unit and an actual position to 0 degrees when the evaluation value is negative, and sets the position error to 180 degrees when the evaluation value is positive; a position estimator that adds a weighted average of a position estimated by the medium / high speed range position estimator and a position estimated by the low speed range position estimator to a position error determined by the polarity determination unit, and sets the result as a position used in the current conversion unit and the voltage command value conversion unit; A control device for an electric motor comprising:

2. The motor control device according to claim 1, The estimation unit is The high frequency current included in the d-axis current is iγh, the amplitude of the superimposed voltage is Vh, the angular frequency of the superimposed voltage is ωh, the d-axis inductance of the motor is Ld, the q-axis inductance of the motor is Lq, Ld0=(Ld+Lq) / 2, Ld1=(Ld-Lq) / 2, the d-axis current is id, id=ihsinωht, the high frequency current is iγh, and In the case where the symbol BEF indicates a value obtained by removing AC components from a value, and the symbol MAF indicates a value obtained by extracting DC components from a value, When the high frequency current is multiplied by sinωht, which is the frequency component of the superimposed voltage as a demodulation signal, to obtain the following formula 1, the AC component (1-cos2ωht) is removed from the following formula 1 by a band rejection filter to obtain the following formula 2, the reciprocal of the following formula 2 is obtained as the following formula 3, the following formula 3 is multiplied by the sinωht to obtain the following formula 4, and the DC component is extracted from the following formula 4 by a moving average filter to obtain the following formula 5, The value on the left side of the following formula 5 is the evaluation value. [0010] [0025] [0030] [0045] [0050] A control device for an electric motor.

3. The motor control device according to claim 1, the position estimation unit increases a weight corresponding to the position estimated by the low speed range position estimation unit as the rotation speed of the rotor decreases, The superimposing unit increases the amplitude of the superimposed voltage as the rotation speed of the rotor decreases. A control device for an electric motor.

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