JP2010136582A - Magnetic pole position estimator for electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic pole position estimator for an electric motor, capable of properly estimating the rotation speed of a motor and a magnetic pole position while suppressing deterioration in estimation response in estimating them. <P>SOLUTION: This pole position estimator includes: a magnetic pole position error estimating section 46 for setting a γδ coordinate system having a phase difference Δθe for a dq coordinate system, and calculating a phase difference Δθe based on the deviation in current between a γ-axis current Iγ and a δ-axis current Iδ of a motor, and a γ-axis model current IγM and a δ-axis model current IδM corresponding to a voltage equation of a predetermined model of the motor; a median filter 47 for performing median filter processing for the phase difference Δθe calculated by the magnetic pole position error estimating section 46; and a rotation speed-magnetic pole position operating section 48 for operating a magnetic pole position estimation value θe of the motor based on a phase difference Δθ'e obtained by the median filter processing by the median filter 47. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a magnetic pole position estimation device for an electric motor.

Conventionally, for example, the phase difference is calculated from the γ-axis current in the γδ coordinate system having a phase difference with respect to the dq coordinate system and the current deviation between the δ-axis current and the model current of each axis calculated based on the motor model, An apparatus that estimates the rotational speed of a motor based on a phase difference is known (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 08-308286

By the way, in the apparatus according to the above prior art, when the rotational speed of the motor is low, the induced voltage of the motor is lowered, and there is a possibility that an impulse-like error due to noise occurs in the calculation result of the phase difference. If a malfunction such as divergence occurs in the estimation of the rotation speed of the motor due to the error, the motor may step out. In response to such a problem, for example, if the response frequency of the process for estimating the rotation speed of the motor is reduced and the sensitivity to noise is reduced, the problem arises that the responsiveness of the process decreases.
SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is a motor magnetic pole position estimation device capable of performing appropriate estimation processing while suppressing deterioration in estimation responsiveness when estimating the rotation speed and magnetic pole position of a motor. The purpose is to provide.

  In order to solve the above problems and achieve the object, the motor magnetic pole position estimation apparatus according to the first aspect of the present invention sets a γδ coordinate system having a phase difference with respect to the dq coordinate system, and A phase difference calculating means for calculating the phase difference based on a current deviation between a current and a model current corresponding to a voltage equation of a predetermined model of the motor (for example, a magnetic pole position error estimating unit 46 in the embodiment); The median filter means (for example, the median filter 47 in the embodiment) that performs median filter processing on the phase difference calculated by the phase difference calculation means, and the phase difference subjected to the median filter processing by the median filter means. Magnetic pole position calculation means (for example, the rotational speed-magnetic pole position calculation unit 48 in the embodiment) for calculating the magnetic pole position of the motor based on the above. Yeah.

  Further, the magnetic pole position estimating apparatus for an electric motor according to the second aspect of the present invention is an inverter (for example, a commutator for sequentially energizing a three-phase AC electric motor (for example, the motor 11 in the embodiment) by a pulse width modulation signal. Inverter 13) in the embodiment, and pulse width modulation signal generation means (for example, PWM signal generation unit 23 in the embodiment) for generating the pulse width modulation signal by a carrier wave signal, the median filter means Performs the median filter processing only when the magnitude of the command voltage vector of the electric motor is less than a predetermined lower limit voltage, and the magnetic pole position calculation means is configured such that the magnitude of the command voltage vector of the electric motor is greater than or equal to a predetermined lower limit voltage. In some cases, the magnetic pole position of the motor is calculated based on the phase difference calculated by the phase difference calculating means.

  Furthermore, in the magnetic pole position estimation apparatus for an electric motor according to the third aspect of the present invention, the median filter means performs a load median filter process as the median filter process.

  According to the magnetic pole position estimation apparatus of the electric motor according to the first aspect of the present invention, an impulse error caused by noise is removed from the phase difference by performing a median filter process on the phase difference output from the phase difference calculation means. can do. Thereby, even when the rotational speed of the motor is low, for example, it is possible to perform an appropriate estimation process while suppressing deterioration in estimation responsiveness when estimating the magnetic pole position.

  Furthermore, according to the magnetic pole position estimation device for the electric motor according to the second aspect of the present invention, when the magnitude of the command voltage vector of the electric motor is less than the predetermined lower limit voltage, the error due to the dead time in the inverter and the inverter Impulse errors are likely to occur in the phase difference output from the phase difference calculation means due to an error caused by the on-voltage generated by the on-resistance of each transistor. In this case, an impulse error can be appropriately removed by performing median filtering on the phase difference. Further, when the magnitude of the command voltage vector is larger than the predetermined lower limit voltage, it is possible to prevent the processing time from becoming longer by prohibiting the execution of the median filter process.

  Furthermore, according to the magnetic pole position estimating apparatus for an electric motor according to the third aspect of the present invention, it is possible to improve the expansibility of arithmetic processing and improve the ability to remove impulse-like errors.

Embodiments of a magnetic pole position estimating apparatus for an electric motor according to the present invention will be described below with reference to the accompanying drawings.
The magnetic pole position estimation device 10 (hereinafter simply referred to as the magnetic pole position estimation device 10) of the electric motor according to this embodiment is, for example, a magnetic pole position (that is, simply referred to as the motor 11) of a three-phase AC brushless DC motor 11 (hereinafter simply referred to as the motor 11). The rotation angle of the magnetic pole of the rotor from a predetermined reference rotation position is estimated, and the motor 11 includes a rotor (not shown) having a permanent magnet used for a field and a rotating magnetic field that rotates the rotor. And a stator (not shown).
As shown in FIG. 1, for example, the magnetic pole position estimation device 10 includes an inverter 13 that uses a battery 12 as a DC power source and a motor control device 14.

The three-phase (for example, U-phase, V-phase, and W-phase) AC motor 11 is driven by the inverter 13 in response to a control command output from the motor control device 14.
The inverter 13 includes a bridge circuit 13a formed by bridge connection using a plurality of switching elements (for example, MOSFETs: Metal Oxide Semi-conductor Field Effect Transistors) and a smoothing capacitor C, and the bridge circuit 13a performs pulse width modulation ( It is driven by the PWM signal.

  In this bridge circuit 13a, for example, a high-side and low-side U-phase transistor UH, UL paired for each phase, a high-side and low-side V-phase transistor VH, VL, a high-side and low-side W-phase transistor WH, WL is bridge-connected. Each transistor UH, VH, WH has a drain connected to the positive terminal of the battery 12 to form a high side arm, and each transistor UL, VL, WL has a source connected to the grounded negative terminal of the battery 12. It constitutes the low side arm. For each phase, the sources of the high-side arm transistors UH, VH, WH are connected to the drains of the low-side arm transistors UL, VL, WL, and the transistors UH, UL, VH, VL, WH, WL. Each of the diodes DUH, DUL, DVH, DVL, DWH, DWL is connected between the drain and the source so as to be in the forward direction from the source to the drain.

  The inverter 13 is, for example, a gate signal (that is, a PWM signal) that is a switching command that is output from the motor control device 14 when driving the motor 11 and is input to the gates of the transistors UH, VH, WH, UL, VL, WL. ), The DC power supplied from the battery 12 is converted into the three-phase AC power by switching the on / off (cut-off) state of each pair of transistors for each phase. By sequentially commutating energization to the windings, AC U-phase current Iu, V-phase current Iv and W-phase current Iw are passed through the stator windings of each phase.

  As will be described later, the motor control device 14 performs feedback control (vector control) of current on the γ-δ coordinates forming the rotation orthogonal coordinates, and calculates the command γ-axis current Iγc and the command δ-axis current Iδc. The phase voltage commands Vu, Vv, and Vw are calculated based on the command γ-axis current Iγc and the command δ-axis current Iδc, and a PWM signal that is a gate signal for the inverter 13 is calculated according to the phase voltage commands Vu, Vv, and Vw. Output. Then, the γ-axis current Iγ and the δ-axis current Iδ obtained by converting the phase currents Iu, Iv, Iw actually supplied from the inverter 13 to the motor 11 on the γ-δ coordinates, the command γ-axis current Iγc, and Control is performed so that each deviation from the command δ-axis current Iδc becomes zero.

The motor control device 14 includes, for example, a phase current sensor I / F (interface) 21, a control device 22, and a PWM signal generation unit 23.
A phase current sensor I / F (interface) 21 is provided between the bridge circuit 13a of the inverter 13 and the motor 11, and each phase current of at least any two of the three phase currents (for example, the U phase current and the V-phase current) is detected, and a detection signal output from each phase current sensor 32 is output to the control device 22.

For example, as shown in FIG. 2, the control device 22 has a phase difference Δθe that is a difference between the actual rotation angle and the estimated or designated rotation angle with respect to the dq axes of the rotation orthogonal coordinates of the actual motor 11. Then, a γ-δ axis of rotation orthogonal coordinates having a rotation speed ωe is set, and current feedback control (vector control) is performed on the γ-δ coordinates.
The control device 22 generates a command γ-axis current Iγc and a command δ-axis current Iδc, calculates each phase voltage command Vu, Vv, Vw based on the command γ-axis current Iγc and the command δ-axis current Iδc, and generates a PWM signal. To the unit 23.
In addition, the control device 22 includes a γ-axis current Iγ and a δ-axis current Iδ obtained by converting the phase currents Iu, Iv, and Iw corresponding to the detection signals output from the phase current sensors 32 into γδ coordinates, Current feedback control (vector control) is performed so that each deviation between the command γ-axis current Iγc and the command δ-axis current Iδc becomes zero.
Further, the control device 22 estimates the magnetic pole position of the motor 11.
Details of the operation of the control device 22 will be described later.

  The PWM signal generation unit 23 compares each phase voltage command Vu, Vv, Vw with a carrier signal such as a triangular wave in order to pass a sinusoidal current to the three-phase stator winding, and A gate signal (that is, a PWM signal) for driving the transistors UH, VH, WH, UL, VL, WL on / off is generated. Then, the inverter 13 converts the DC power supplied from the battery 12 into three-phase AC power by switching the on (conductive) / off (cut-off) state of each transistor that forms a pair for each of the three phases. By sequentially commutating energization to each stator winding of the three-phase motor 11, AC U-phase current Iu, V-phase current Iv, and W-phase current Iw are energized to each stator winding.

  For example, as illustrated in FIG. 3, the control device 22 includes a speed control unit 41, a command current generation unit 42, a current control unit 43, a γδ-3 phase conversion unit 44, a three phase-γδ conversion unit 45, A magnetic pole position error estimation unit 46, a median filter 47, a rotation speed-magnetic pole position calculation unit 48, and an electrical angle-mechanical angle conversion unit 49 are provided.

The speed control unit 41 is based on the rotational speed command value ωrc input from the outside, for example, by the closed loop control corresponding to the rotational speed ωr (mechanical angle) output from the electrical angle-mechanical angle conversion unit 49, and the torque command Tc. Is calculated. Then, a torque command Tc is output.
Note that the control device 22 may include a torque control unit instead of the speed control unit 41, and execute torque control such as closed loop control on the torque by the torque control unit.

  The command current generator 42 calculates and outputs a command δ-axis current Iδc and a command γ-axis current Iγc based on the torque command Tc output from the speed controller 41.

  The current control unit 43 calculates a deviation ΔIγ between the command γ-axis current Iγc output from the command current generation unit 42 and the γ-axis current Iγ output from the three-phase-γδ conversion unit 45, and the command current generation unit 42 A deviation ΔIδ between the output command δ-axis current Iδc and the δ-axis current Iδ output from the three-phase-γδ converter 45 is calculated. Then, for example, by PI (proportional / integral) operation, the deviation ΔIγ is controlled and amplified to calculate the γ-axis voltage command value Vγ, and the deviation ΔIδ is controlled and amplified to calculate the δ-axis voltage command value Vδ. Then, the γ-axis voltage command value Vγ and the δ-axis voltage command value Vδ are output.

The γδ-3 phase conversion unit 44 uses the estimated magnetic pole position value θe of the motor 11 output from the rotation speed-magnetic pole position calculation unit 48 to generate a γ-axis voltage command value Vγ and a δ-axis voltage command value on the γ-δ coordinate. Vδ is converted into a U-phase voltage command Vu, a V-phase voltage command Vv, and a W-phase voltage command Vw, which are voltage command values on a three-phase AC coordinate that is a stationary coordinate.
The three-phase-γδ converter 45 is based on the detection signals of the phase currents Iu and Iv output from the phase current sensor I / F (interface) 21 and the sum of the current values of the phase currents at the same timing is zero. Using this, the current value of the other one-phase phase current (for example, W-phase current Iw) is calculated from the current value of the two-phase phase current (for example, each phase current Iu, Iv). The phase currents Iu, Iv, and Iw are converted into the γ-axis current Iγ and the δ-axis current Iδ on the γ-δ coordinates based on the estimated magnetic pole position θe of the motor 11 output from the rotation speed-magnetic pole position calculation unit 48. Convert to

  The magnetic pole position error estimation unit 46, for example, the γ-axis voltage command value Vγ and the δ-axis voltage command value Vδ output from the current control unit 43 and the γ-axis currents Iγ and δ output from the three-phase-γδ conversion unit 45. Based on the shaft current Iδ, the phase difference Δθe is estimated using the fact that the induced voltage generated by the motor 11 when the motor 11 rotates changes with the rotational speed.

  As shown in FIG. 4, for example, the magnetic pole position error estimation unit 46 includes a motor model current calculation unit 51, a γ-axis current deviation calculation unit 52a and a δ-axis current deviation calculation unit 52b, and a magnetic pole position error calculation unit 53. Configured.

The motor model current calculation unit 51 uses the γ-axis voltage command value Vγ and the δ-axis voltage command value Vδ output from the current control unit 43 to calculate the γ-axis model current IγM and δ-axis according to the voltage equation of a predetermined model of the motor 11. The model current IδM is calculated, and the model currents IγM and IδM are output.
First, the voltage equation of a predetermined model of the motor 11 will be described below.
The voltage equation of the motor 11 in the γδ coordinate system (that is, the voltage equation in continuous time) is, for example, the γ-axis voltage command value Vγ and the δ-axis voltage command value Vδ, the winding resistance R, and the differential operator p. , D-axis inductance Ld and q-axis inductance Lq, phase difference Δθe, rotational speed estimation value ωe, d-axis current Id and q-axis current Iq, and magnetic flux component (induced voltage constant) φ of the permanent magnet, for example, It is described as shown in the following mathematical formula (1).

  In the above formula (1), if terms relating to the magnetic pole position and the rotational speed are deleted as disturbances, a simple voltage equation of the motor 11 is described as shown in the following formula (2).

  When the above equation (2), which is a simple voltage equation in continuous time, is discretized using, for example, Euler approximation, the discrete time state equation is expressed by, for example, the following equation using one period Ts of the carrier signal and an arbitrary natural number n. It is described as shown in (3). In the following mathematical formula (3), an arbitrary natural number n is an index corresponding to the peak of the carrier signal on the peak side of the carrier signal in an arbitrary control cycle, for example.

  The motor model current calculation unit 51 outputs the (n−1) th value of the γ-axis voltage command value Vγ and the δ-axis voltage command value Vδ output from the current control unit 43, that is, the γ-axis voltage command value Vγ [n−1]. And the δ-axis voltage command value Vδ [n−1], the (n) -th γ-axis model current IγM [n] and δ-axis are obtained by the voltage equation of the predetermined model of the motor 11 shown in the above equation (3). A model current IδM [n] is calculated, and each model current IγM [n], IδM [n] is output.

  The γ-axis current deviation calculation unit 52a and the δ-axis current deviation calculation unit 52b have the same timing, for example, at the (n) -th peak of the carrier peak on the peak side of the carrier signal, as shown in the following formula (4). Currents of the γ-axis current Iγ [n] and δ-axis current Iδ [n] output from the conversion unit 45 and the model currents IγM [n] and IδM [n] output from the motor model current calculation unit 51 Deviations ΔIγM [n] and ΔIδM [n] are calculated, and current deviations ΔIγM [n] and ΔIδM [n] are output.

For example, the magnetic pole position error calculation unit 53 includes (n) -th current deviations ΔIγM [n] and ΔIδM [n] output from the γ-axis current deviation calculation unit 52a and the δ-axis current deviation calculation unit 52b, The (n-1) th rotational speed estimation value ωe [n-1] and the (n-1) th γ-axis current Iγ [n-1] and δ-axis output from the three-phase-γδ converter 45. Based on the following formula (5), the current Iδ [n−1] and the electric circuit constant of the motor 11 that is known in advance (that is, each inductance Ld, Lq and one period Ts of the carrier signal) The first phase difference Δθe is calculated. Then, the phase difference Δθe is output.
The following equation (5) is a discrete time state equation obtained by discretizing the voltage equation of the motor 11 shown in the equation (1), and a voltage equation of a predetermined model of the motor 11 shown in the equation (3), that is, It is calculated based on a discrete time state equation obtained by discretizing a simple voltage equation of the motor 11.

The median filter 47 outputs an odd number of sample values of the phase difference Δθe output from the magnetic pole position error calculator 53, for example, three phase differences Δθe [n], Δθe corresponding to k = 2 in the following equation (6). As in [n−1], Δθe [n-2], the (n) -th phase difference Δθe [n], and a predetermined number of phase differences Δθe [n−1],. Then, the median when the magnitudes are rearranged in ascending or descending order is output as the (n) th new phase difference Δθ′e [n].
Note that the median filter 47 may perform median filter processing according to the following equation (6) only when the magnitude of the command voltage vector Vγδ is less than the predetermined lower limit voltage. In this case, if the magnitude of the command voltage vector Vγδ is equal to or greater than the predetermined lower limit voltage, the (n) -th phase difference Δθe [n] output from the magnetic pole position error calculation unit 53 is changed to a new phase difference Δθ′e. Output as [n].

  The median filter 47 may be a load median filter, for example, as shown in the following mathematical formula (7). At this time, the median filter 47 has the phase differences Δθe [n], Δθe [n−1],. For each Δθe [n−k], sample values are copied by weights w0, w1,.

  Based on the phase difference Δθ′e output from the median filter 47, the rotation speed-magnetic pole position calculation unit 48 performs phase synchronization processing using a PLL (Phase-locked loop).

  As the phase synchronization processing, the phase synchronization unit 56 performs, for example, a PI (proportional / integral) operation, and, for example, based on the transfer function Ge (s) described as shown in the following formula (8), the proportional gain Kp and the integral Based on the gain Ki, for example, the rotational speed estimation value ωe is calculated from the phase difference Δθ′e as shown in the following formula (9). Then, the estimated rotational speed value ωe is output.

  The integration calculation unit 57 calculates the magnetic pole position estimation value θe by integrating the rotation speed estimation value ωe output from the phase synchronization unit 56, for example, as shown in the following formula (10). Then, the magnetic pole position estimated value θe is output.

  Note that the rotation speed-magnetic pole position calculation unit 48 is not limited to the PI operation, and is based on a one-dimensional observer using the phase difference Δθ′e as an input value, for example, as in a modification example shown in FIG. 6 and the following formula (11). A follow-up calculation process may be executed to calculate the rotational speed estimated value ωe and the magnetic pole position estimated value θe.

  The electrical angle-mechanical angle conversion unit 49 converts the rotation speed estimated value ωe output from the rotation speed-magnetic pole position calculation unit 48 into a rotation speed ωr (mechanical angle) according to the number of pole pairs q of the motor 11, and rotates the rotation. The speed ωr (mechanical angle) is output.

  As described above, according to the magnetic pole position estimation apparatus 10 of the electric motor according to the present embodiment, an impulse-like error caused by noise is performed by performing the median filter process on the phase difference Δθe output from the magnetic pole position error estimation unit 46. Can be removed from the phase difference Δθe. Thereby, even when the rotational speed of the motor 11 is low, for example, the response frequency of the rotational speed-magnetic pole position calculation unit 48 that performs phase synchronization processing such as PLL (Phase-locked loop) is reduced, and the sensitivity to noise is reduced. Therefore, it is possible to perform appropriate estimation processing while suppressing deterioration in estimation responsiveness when estimating the magnetic pole position estimated value θe. Moreover, in the median filter process, only one sample value is selected from a plurality of sample values of the phase difference Δθe, so that the time delay of the output value can be suppressed.

  For example, when the magnitude of the command voltage vector Vγδ is less than a predetermined lower limit voltage, it is caused by an error caused by a dead time in the inverter 13 and an error caused by an on-voltage generated by the on-resistance of each transistor of the inverter 13. Thus, an impulse-like error is likely to occur in the phase difference Δθe output from the magnetic pole position error estimation unit 46. In this case, an impulse error can be appropriately removed by performing median filtering on the phase difference Δθe. Further, when the magnitude of the command voltage vector Vγδ is larger than the predetermined lower limit voltage, it is possible to prevent the processing time from becoming longer by prohibiting the execution of the median filter process.

  Furthermore, by making the median filter 47 a weighted median filter, it is possible to improve the scalability of the arithmetic processing, and it is possible to improve the ability to remove impulse-like errors.

  In the above-described embodiment, the magnetic pole position error estimation unit 46 estimates the phase difference Δθe by utilizing the fact that the induced voltage generated by the motor 11 changes according to the rotation speed when the motor 11 rotates. For example, the phase difference Δθe is utilized by applying a harmonic voltage to the γ-axis voltage command value Vγ and the δ-axis voltage command value Vδ output from the current control unit 43 and changing the inductance depending on the magnetic pole position. May be estimated.

  In the above-described embodiment, instead of each phase current sensor 32, the DC side current of the bridge circuit 13a of the inverter 13 is between the bridge circuit 13a of the inverter 13 and the negative terminal or the positive terminal of the battery 12. A DC-side current sensor that detects Idc may be provided. In this modification, each phase current is estimated based on the detection signal output from the DC side current sensor and the gate signal input to the inverter 13 from the PWM signal generation unit 23, and the estimated value of each phase current is set to the three-phase value. Input to the −γδ converter 45. In this case, the voltage equation shown in the mathematical formula (3) may be synchronized at the same timing as the timing of the estimated value of each phase current.

It is a block diagram of the magnetic pole position estimation apparatus of the electric motor which concerns on embodiment of this invention. It is a figure which shows an example of the (gamma) -delta axis | shaft of a rotation orthogonal coordinate and dq axis which concerns on embodiment of this invention. It is a block diagram of the magnetic pole position estimation apparatus of the electric motor which concerns on embodiment of this invention. It is a block diagram of the magnetic pole position error estimation part shown in FIG. It is a block diagram of the rotational speed-magnetic pole position calculating part shown in FIG. It is a block diagram of the rotational speed-magnetic pole position calculating part which concerns on the modification of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric pole position estimation apparatus 11 Motor 13 Inverter 22 Control apparatus 23 PWM signal generation part (pulse width modulation signal generation means)
46 Magnetic pole position error estimation unit (phase difference calculation means)
47 Median filter 48 Rotational speed-magnetic pole position calculator (magnetic pole position calculator)

Claims (3)

A phase difference calculation that sets a γδ coordinate system having a phase difference with respect to the dq coordinate system and calculates the phase difference based on a current deviation between a real current of the motor and a model current corresponding to a voltage equation of a predetermined model of the motor. Means,
Median filter means for performing median filter processing on the phase difference calculated by the phase difference calculation means;
A magnetic pole position estimating device for an electric motor, comprising: magnetic pole position calculating means for calculating the magnetic pole position of the electric motor based on the phase difference subjected to the median filter processing by the median filter means. An inverter that sequentially commutates the energization of a three-phase AC motor by a pulse width modulation signal; and a pulse width modulation signal generation unit that generates the pulse width modulation signal from a carrier wave signal;
The median filter means performs the median filter processing only when the magnitude of the command voltage vector of the electric motor is less than a predetermined lower limit voltage,
The magnetic pole position calculating means calculates the magnetic pole position of the electric motor based on the phase difference calculated by the phase difference calculating means when the magnitude of the command voltage vector of the electric motor is not less than a predetermined lower limit voltage. The apparatus for estimating a magnetic pole position of an electric motor according to claim 1. 3. The motor magnetic pole position estimation apparatus according to claim 1, wherein the median filter means performs a load median filter process as the median filter process.

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