JP5332400B2 - Torque pulsation suppression device and suppression method for electric motor - Google Patents

Description

  The present invention relates to an apparatus and a method for suppressing torque pulsation generated due to electric motor parameters in a torque control apparatus for an electric motor (rotating electric machine) that drives a rotating machine.

  Since the electric motor has structural magnetic flux distortion and cogging torque, it generates torque pulsation that contributes to vibration and noise according to the rotation. In addition, when a multi-inertia system is configured between the motor and the load, the mechanical resonance point and the torque pulsation frequency component coincide with each other, generating an excessive shaft torsion torque, which adversely affects operating characteristics and damages the system. There is a danger of.

  In order to solve these problems, there is a method for suppressing torsional resonance by feedback control. However, in the resonance suppression method using feedback, resonance suppression becomes difficult when the resonance frequency and the response frequency of the inverter are close, or when the sampling time of the control system cannot be sufficiently shortened.

In order to solve these problems, there is one in which a compensation signal for canceling the torque ripple of the IPM motor output is added to the d, q-axis current command or torque command of the IPM motor (for example, see Patent Document 1).
JP 2007-267466 A

  The torque pulsation of an electric motor is complicatedly associated with various factors such as magnetic imperfection of the motor structure, response / current error of the inverter power source that drives the motor, and mechanical system characteristics. In particular, an embedded magnet type synchronous motor (hereinafter referred to as IPMSM) is a high-efficiency motor that can effectively utilize not only the torque by a permanent magnet but also reluctance torque using magnetic anisotropy. From the viewpoint of pulsation, there is a problem that both magnet torque pulsation and reluctance torque pulsation occur in a composite manner.

  In general, the IPMSM is controlled by vector control of current on rotational coordinates (orthogonal dq coordinates) synchronized with the rotational speed of the motor. The relationship between the d-axis and q-axis currents and the steady torque equation is obtained as follows.

However, Ψ: number of flux linkages by permanent magnet, L _d : d-axis inductance, L _q : q-axis inductance, i _d : d-axis current, i _q : q-axis current In IPMSM, d depends on the application and purpose. Since it is necessary to control the ratio between the shaft current and the q-axis current (for example, to realize maximum torque control), it is necessary to separately provide an appropriate command value. When superimposing the torque pulsation compensation signal, it is necessary to consider separately so that the d-axis and q-axis currents do not interfere with each other.

Further, the above formula is a steady torque simplified by average values of Ψ, L _d , and L _q , and torque pulsation due to distortion of the motor parameters is not expressed in the formula. Therefore, for example, in Patent Document 1, it is assumed that the magnetic flux Ψ has a distortion component depending on the rotor phase θ, and a compensation signal for suppressing the distortion component is superimposed on the current command values i _d and i _q of each axis. doing. However, since the distortion components of the inductances L _d and L _q are not taken into account, it is considered that a torque pulsation compensation error strictly occurs.

  An object of the present invention is to provide a torque pulsation suppressing device and a suppression method for an electric motor that can highly accurately suppress torque pulsations caused by distortion of motor parameters (inductance, the number of flux linkages caused by permanent magnets, structural imperfections, etc.). Is to provide.

  In order to solve the above-mentioned problems, the present invention derives a torque pulsation generated due to the parameters of the motor (inductance, the number of flux linkages by a permanent magnet, structural imperfection, etc.), and this torque pulsation A new pulsation component generated by superimposing a compensation current to compensate for the inverter current command is derived, and a current compensation signal that cancels this new pulsation component is added to the inverter current command. The torque pulsation suppressing device and the suppressing method are characterized.

(1) A torque-current command conversion unit for converting the torque command value of the motor into d and q-axis current components, and an output of the torque-current command conversion unit as a d and q-axis current command value. In the torque control device for an electric motor provided with an inverter that performs electric current control of the electric motor from the output current detection value of the inverter,
Deriving torque pulsation generated due to motor parameters and deriving new pulsation component generated by superimposing compensation current to compensate for this torque pulsation on inverter current command to compensate for torque pulsation And a pulsation compensator for adding a current compensation signal for canceling a new pulsation component generated by superimposing the compensation current to be superimposed on the inverter current command to the inverter current command.

  (2) The pulsation compensator derives the torque pulsation generated due to the motor parameters as a pulsation component of an integer multiple of 3 and an integer multiple of 6 of the rotational phase angle θ of the motor and the inverter operating frequency. The present invention is characterized in that there is provided means for obtaining a current compensation signal for canceling these torque pulsation components and adding the current compensation signal to the current command of the inverter.

(3) The pulsation compensation unit obtains a q-axis compensation current i _{qc at} which the d-axis compensation current is 0 for the pulsation component that is an integral multiple of 6 and the torque pulsation component is “0”. Means is provided for _{setting the} current i _qc to be an addition value to the q-axis current command value.

(4) The pulsation compensation unit obtains a d-axis compensation current i _{dc at} which the q-axis compensation current is 0 for the pulsation component that is an integral multiple of 6 and the torque pulsation component is “0”. Means is provided for setting the current i _dc to be a value added to the d-axis current command value.

(5) The pulsation compensation unit obtains a d-axis compensation current i _dc and a q-axis compensation current i _{qc at} which the torque pulsation component is “0” for the pulsation component that is an integral multiple of 6 to obtain a d-axis compensation current i _There is provided means for setting _dc as an addition value to the d-axis current command value and _setting a q-axis compensation current i _qc as an addition value to the q-axis current command value.

(6) The pulsation compensation unit obtains a q-axis compensation current i _{qc at} which the d-axis compensation current is set to 0 and the torque pulsation component is “0” for the pulsation component that is an integral multiple of 3 and this q-axis compensation Means is provided for _{setting the} current i _qc to be an addition value to the q-axis current command value.

(7) The pulsation compensation unit obtains a d-axis compensation current i _{dc at} which the q-axis compensation current is 0 for the pulsation component that is an integral multiple of 3 and the torque pulsation component is “0”. Means is provided for setting the current i _dc to be a value added to the d-axis current command value.

(8) The pulsation compensation unit obtains a d-axis compensation current i _dc and a q-axis compensation current i _{qc at} which the torque pulsation component is “0” for the pulsation component that is an integral multiple of 3 to obtain a d-axis compensation current i _There is provided means for setting _dc as an addition value to the d-axis current command value and _setting a q-axis compensation current i _qc as an addition value to the q-axis current command value.

(9) The pulsation compensation unit obtains a d-axis compensation current i _dc and a q-axis compensation current i _{qc at} which the torque pulsation component is “0” for the pulsation component of an integer multiple of 6 and an integral multiple of 3. The d-axis compensation current i _dc is a value added to the d-axis current command value, and the q-axis compensation current i _qc is a value added to the q-axis current command value.

  (10) The dq-axis current command value compensated with the compensation current is used as an inverter current command value through a response compensation unit having an inverse transfer function of a transfer function expressing an inverter response delay.

(11) A torque-current command conversion unit that converts the torque command value of the motor into d and q-axis current components, and an output of the torque-current command conversion unit as a d and q-axis current command value. In the torque control device for an electric motor provided with an inverter that performs electric current control of the electric motor from the output current detection value of the inverter,
The pulsation compensation unit that suppresses the torque pulsation of the motor derives the torque pulsation generated due to the parameters of the motor, and a new current generated by superimposing the compensation current for compensating the torque pulsation on the current command of the inverter. A new pulsation component is derived, and a current compensation signal that cancels the new pulsation component is added to the current command of the inverter.

  As described above, according to the present invention, the torque pulsation generated due to the parameters of the motor (inductance, the number of interlinkage magnetic fluxes by permanent magnets, structural imperfections, etc.) is derived, and this torque pulsation is calculated. A new pulsation component generated by superimposing the compensation current to be compensated on the inverter current command is derived, and a current compensation signal that cancels this new pulsation component is added to the inverter current command. The resulting torque pulsation can be suppressed with high accuracy.

(Embodiment 1)
Following the principle description of the present invention, the suppression device and the suppression method of the present embodiment will be described.

(A) Principle Description The IPMSM three-phase voltage equation can be expressed as follows.

[V]: three-phase voltage, [i]: three-phase current, [L]: inductance matrix, [ψ]: permanent magnet flux linkage, R: winding resistance, p: differential operator Assuming that “Ψ: the number of flux linkages by a permanent magnet” and “L: inductance” have some distortion components, the following series expansion formula is assumed.

However, l: leakage inductance, θ: rotor phase, n: order of Fourier series When the above is subjected to rotational coordinate transformation (3 phase → orthogonal dq axis coordinate transformation) and arranged in a matrix expression, the result is as follows.

However, [V _dq ]: dq axis voltage, [i _dq ]: dq axis current In consideration of input power, output power, winding loss, and accumulated magnetic energy, the following formula is derived from the energy conservation law.

However, P _m : Output power, P _i : Input power, P _r : Loss power, P _L : Power corresponding to accumulated magnetic energy The torque T is obtained from Equations 4 and 5 as follows.

  Substituting the series expansion formulas defined in Formulas 2 and 3 into Formula 6 and rearranging them, the torque T is finally expressed by the following formula.

  Here, the underlined portion of Equation 7 represents the torque pulsation term ΔT, and the coefficients are as follows.

However, the suffix of M: mutual inductance, τ: cogging torque component coefficient indicates the order of series expansion based on the rotational phase θ. Further, τ _cog represents cogging torque, and its frequency component is related to the number of slots and the number of poles of the motor, but here, it is expressed by an integer multiple of “6” in consideration of generality. (Hereafter, the n-fold pulsation component of the rotation fundamental wave is expressed as nf. Example: 6-fold component → 6f)
Thus, it can be seen that the torque pulsation term due to the electric motor can be basically expressed by a sine / cosine polynomial of frequency components of multiples of 3 and multiples of 6. Focusing on the coefficient of the trigonometric function of Equation 7, a distortion component appears as a coefficient of 3f component to the first power of current, and a coefficient of 6f component to the square of current. Further, paying attention to Equation 8, it can be seen that the coefficient of the 3f component is a function related to the distortion of the linkage magnetic flux by the permanent magnet, and the coefficient of the 6f component is a function related to the distortion of the inductance, ie, the reluctance torque pulsation component. From the above, it can be seen that the torque pulsation is generally more dominant in the 6f component than in the 3f component, and has a specific periodicity with respect to the rotational phase.

Next, a compensation signal for setting ΔT = 0 based on the torque pulsation term ΔT is considered. In IPMSM, since there are two d-axis and q-axis current command values, a compensation signal can be given to both. Therefore, the pulsation compensation signal for each axis is set to i _dc : d-axis pulsation compensation current, i _qc : q-axis pulsation compensation current, and these are superimposed on the original steady dq-axis current command value. Current command values of I _do and I _qo . That is, the current command value is expressed by the following formula.

By substituting this into the current part of Equation 7, the following Equation 10 is obtained. However, here, as an example, only the 6f component, which is the dominant component of torque pulsation, is focused, and the compensation current is sufficiently smaller than the steady current (I _do >> i _dc , I _qo >> i _qc ). A first-order approximate expression given by Macrolin's expansion is used.

The underlined portion of Equation 10 above represents the torque pulsation term. Compared with the original torque pulsation term of Equation 7, a new pulsation component is generated by superimposing the compensation current signals i _dc and i _qc. I understand that. Therefore, in order to suppress the pulsation comprehensively in consideration of the effect of superimposing the compensation current in advance, the compensation formula must be considered so that the torque pulsation term in the underlined portion of Formula 10 is zero.

Therefore, in this embodiment, for convenience, i _dc = 0 and pulsation is compensated only by i _qc . That is, when i _dc = 0 is substituted into the torque pulsation term of Equation 10 and i _qc is obtained such that the torque pulsation term becomes 0, the following Equation 11 is obtained.

The motor parameters and the respective coefficients in the above formula 11 are substituted with those obtained in advance by electromagnetic field analysis based on the motor design data or a method based on actual machine measurement. As a result, the q-axis compensation current signal can be expressed by a functional expression of the rotational phase angle θ and ideal current command values I _do and I _qo , so that a compensation signal with a torque pulsation component of 0 is obtained from this functional expression, By adding to the torque command, torque pulsation can be suppressed in accordance with the load operation state.

(B) Description of Embodiment FIG. 1 shows a configuration diagram of a torque pulsation suppressing device of the present embodiment. The torque-current command converter 1 converts the torque command value T _ref of the motor load into dq-axis currents I _do and I _qo . This conversion is converted into d-axis current and q-axis current for performing maximum torque control of IPMSM, for example.

The pulsation compensation unit 2A uses the dq-axis currents I _do and I _qo converted by the conversion unit 1, the rotational phase angle θ measured by the encoder or estimated by the observer, the motor parameters, and the coefficients, and the equation 11 An operation is performed to obtain a current i _{qc at} which the torque pulsation term becomes zero.

The adder 3A adds the current i _qc obtained by the pulsation compensation unit 2A to the q-axis current I _qo converted by the conversion unit 1.

In the inverter 4, the output voltage of the main circuit is controlled by vector control for controlling the current command separated into the dq axis and the detected value of the load current (dq axis) by the current control system, and PWM control is also used for this control. The motor load 5 which becomes IPMSM is driven, and the output torque is made to coincide with the torque command value T _ref .

In the above configuration, the current i _qc obtained by the pulsation compensation unit 2A is added to the q-axis current command of the inverter 4, and the torque pulsation generated due to the parameters of the motor is suppressed according to the load operation state. be able to.

(Embodiment 2)
In the present embodiment, the torque pulsation is compensated only by the d-axis compensation current i _{dc with} the q-axis compensation current i _qc = 0. That is, when substituting i _qc = 0 into the torque pulsation term of Equation 10 above and _{obtaining the} d-axis compensation current i _dc so that the torque pulsation term becomes 0, Equation 12 below is obtained. Thereby, it can change to a d-axis current compensation value according to voltage saturation or the driving | running state of an electric motor.

FIG. 2 shows a configuration diagram of the torque pulsation suppressing device of the present embodiment. 1 differs from FIG. 1 in that a pulsation compensation unit 2B is used in place of the pulsation compensation unit 2A, and this output I _dc is added to the d-axis current I _do by an adder 3B so that the d-axis current command value of the inverter 4 is obtained. It is in the point to.

  Therefore, in this embodiment, torque ripple can be suppressed in accordance with voltage saturation and the operating state of the electric motor.

(Embodiment 3)
In the first and second embodiments, one of the compensation current signals is set to 0 and the other compensation calculation formula is derived. However, in this embodiment, torque pulsation is suppressed using both compensation signals.

There are various methods for applying the pulsation compensation current to both the d-axis and the q-axis. As an example, a case where the motor parameter coefficient K _idiq in Equation 10 is deleted will be given.

From Equation 10, terms related to K _IDIQ since a _{K idiq (I d0 I q0 +} I d0 I qc + I dc I q0), to the relationship according to the following equation 13.

If defined as described above, the relationship between i _dc and i _qc can be always derived irrespective of the value of K _idiq , so that the motor parameter coefficient to be _solved in advance can be reduced by one.

In the above description, i _dc is represented by the formula i _iqc , but conversely, the q-axis compensation current i _qc may be represented by the d-axis compensation current i _{dc as} in the following formula 14.

The pulsation compensation current when the relationship between i _dc and i _qc is defined as in Equation 13 can be calculated as follows.

The K _idiq component is deleted by the calculation according to the above formula 15. Thereby, the influence of the error at the time of calculating | requiring from electromagnetic field analysis or actual machine measurement, for example can be reduced.

FIG. 3 shows a configuration diagram of the torque pulsation suppressing device of the present embodiment. 1 differs from FIG. 1 in that the pulsation compensation unit 2C calculates i _dc by the calculation of Equation 13 from i _{qc obtained} by the pulsation compensation unit 2A and I _do and I _qo from the torque-current command conversion unit 1. The current i _dc is obtained and added to I _do by the adder 3B.

In the present embodiment, the method of erasing K _idiq using both i _dc and i _qc has been described. However, the coefficient K _idiq to be erased is replaced with another coefficient such as K _id2 or K _iq2 and the same processing is performed. It is also possible.

(Embodiment 4)
In the above-described embodiments, the integral multiple component (6nf) of 6 which is the dominant order of torque pulsation is taken as an example. However, as shown in Equation 7, torque pulsation of an integral multiple component of 3 (3nf component) is also used. Occur.

  Therefore, in this embodiment, torque pulsation compensation is also possible for orders (3f, 9f, 15f,...) That are multiples of 3 but not multiples of 6. From Equation 7 and Equation 9, the torque pulsation term excluding the 6nf component is as follows.

Consider a compensation formula when I _do >> i _dc and I _qo >> i _qc are satisfied and the compensation current of either the d-axis or the q-axis is 0 as in the first and second embodiments. In this case, the condition for the torque pulsation term of Formula 16 to be 0 is as follows.

  Therefore, with respect to the integral multiple frequency component of 3 (excluding the integral multiple of 6), torque pulsation can be suppressed by Equation 17.

Specifically, in the configuration of FIGS. 1 to 3, the pulsation compensation units 2A to 2C are _operated to obtain the compensation current i _qc or i _dc , or both the compensation currents i _qc and i _dc are obtained.

(Embodiment 5)
From Equations 7 and 8, the torque pulsation component due to the distortion of the motor parameters is composed of an integer multiple of 6 and an integer multiple frequency component of 3.

  Therefore, in the present embodiment, both are comprehensively suppressed. Here, as in the first embodiment, the case where d-axis compensation current = 0 is described as an example.

  According to the first embodiment, the integral multiple frequency component of 6 can be suppressed by Expression 11. Further, the integral multiple component of 3 (excluding the integral multiple of 6) can be suppressed by the upper compensation equation of Equation 17. Therefore, if these are superimposed and superimposed on the q-axis current command value, torque pulsation caused by the distortion of the motor parameters can be comprehensively suppressed.

FIG. 4 is a configuration diagram of the torque pulsation suppressing device of the present embodiment. 1 differs from FIG. 1 in that the pulsation compensation unit 2D obtains i _qc to compensate the 6nf component pulsating current by the calculation of Equation 11, and the pulsation compensation unit 2E compensates the 3nf component pulsating current by the calculation of Equation 17. I _qc is obtained, added by the adder 3C, and added to the q-axis current command value Iqo by the adder 3D.

  With this configuration, it is possible to comprehensively suppress torque pulsation of 6 nf components and 3 nf components due to distortion of the motor parameters.

  In this example, the d-axis compensation current is set to 0 and the torque pulsation is suppressed only by the q-axis compensation current. However, the reverse is also possible.

(Embodiment 6)
Since an actual motor drive device is operated at a variable speed using an inverter or the like, a current corresponding to an ideal command value cannot be applied to the motor load due to an inverter response, communication / calculation dead time, or the like, resulting in a compensation error.

Therefore, in this embodiment, the response delay of the inverter is expressed by an approximate transfer function G (s) using a means such as general system identification, and the current command value is obtained via the inverse function G (s) ^−1. To the inverter.

  An example of the configuration is shown in FIG. As an example, this configuration shows a case where compensation is performed only on the q axis. In the configuration of FIG. 1, the dq axis current command value is set as the current command value of the inverter 4 through the response compensation unit 6. The transfer function of the response compensation unit 6 is designed to be an inverse function of the transfer function of the inverter 4.

  According to the present embodiment, the phase and magnitude of the current command value are corrected in consideration of the response delay of the drive system such as an inverter, so that torque pulsation compensation error can be reduced.

  The present embodiment can be applied to the apparatus having the configuration shown in FIGS.

1 is a configuration diagram of a torque pulsation suppressing device according to Embodiment 1. FIG. FIG. 3 is a configuration diagram of a torque pulsation suppressing device according to a second embodiment. FIG. 6 is a configuration diagram of a torque pulsation suppressing device according to a third embodiment. FIG. 6 is a configuration diagram of a torque pulsation suppressing device according to a fifth embodiment. FIG. 10 is a configuration diagram of a torque pulsation suppressing device according to a sixth embodiment.

Explanation of symbols

1 Torque-current command converter 2A, 2B, 2C, 2D, 2E Pulsation compensation unit 3A, 3B, 3C Adder 4 Inverter 5 Motor load 6 Response compensation unit

Claims (11)

A torque-current command conversion unit that converts the torque command value of the motor into d and q-axis current components, and an output of the torque-current command conversion unit as a d and q-axis current command value. The current command value and the output of the inverter In the torque control device for an electric motor provided with an inverter that performs electric current control of the electric motor from the detected current value,
Deriving torque pulsation generated due to motor parameters and deriving new pulsation component generated by superimposing compensation current to compensate for this torque pulsation on inverter current command to compensate for torque pulsation A torque pulsation suppressing device for an electric motor, comprising: a pulsation compensation unit that adds a current compensation signal that cancels a new pulsation component generated by superimposing a compensation current to be superimposed on an inverter current command to the inverter current command.   The pulsation compensation unit derives the torque pulsation generated due to the parameters of the motor as a pulsation component of an integer multiple of 3 and an integer multiple of 6 of the rotational phase angle θ of the motor and the operating frequency of the inverter. 2. The torque pulsation suppressing device for an electric motor according to claim 1, further comprising means for obtaining a current compensation signal for canceling the torque pulsation component and adding the current compensation signal to the current command of the inverter. The pulsation compensation unit obtains a q-axis compensation current i _{qc at} which the d-axis compensation current is 0 for the pulsation component that is an integral multiple of 6 and the torque pulsation is “0”, and this q-axis compensation current i _qc The torque pulsation suppressing device for an electric motor according to claim 2, further comprising means for adding a value to the q-axis current command value. The pulsation compensation unit obtains a d-axis compensation current i _{dc at} which the q-axis compensation current is 0 for the pulsation component that is an integral multiple of 6 and the torque pulsation component is “0”, and this d-axis compensation current i _dc The torque pulsation suppressing device for an electric motor according to claim 2, further comprising means for adding a value to the d-axis current command value. The pulsation compensation unit obtains a d-axis compensation current i _dc and a q-axis compensation current i _{qc at} which the torque pulsation component is “0” for a pulsation component that is an integral multiple of 6, and _calculates the d-axis compensation current i _{dc 3.} The torque pulsation suppression for an electric motor according to claim 2, further comprising means for adding the q-axis compensation current i _qc to the d-axis current command value and adding the q-axis compensation current i _qc to the q-axis current command value. apparatus. The pulsation compensation unit, for an integer multiple of the ripple component of the 3, the d-axis compensation current is set to 0 to obtain the q-axis compensation current i _qc of the torque ripple component becomes "0", the q-axis compensation current i _qc The torque pulsation suppressing device for an electric motor according to claim 2, further comprising means for adding a value to the q-axis current command value. The pulsation compensation unit obtains a d-axis compensation current i _{dc at} which the q-axis compensation current is 0 for the pulsation component that is an integral multiple of 3 and the torque pulsation component is “0”, and this d-axis compensation current i _dc The torque pulsation suppressing device for an electric motor according to claim 2, further comprising means for adding a value to the d-axis current command value. The pulsation compensation unit obtains a d-axis compensation current i _dc and a q-axis compensation current i _{qc for} which the torque pulsation component is “0” for the pulsation component that is an integral multiple of 3, and _calculates the d-axis compensation current i _{dc 3.} The torque pulsation suppression for an electric motor according to claim 2, further comprising means for adding the q-axis compensation current i _qc to the d-axis current command value and adding the q-axis compensation current i _qc to the q-axis current command value. apparatus. The pulsation compensation unit obtains a d-axis compensation current i _dc and a q-axis compensation current i _{qc at} which the torque pulsation component is “0” for the pulsation component of an integer multiple of 6 and an integer multiple of 3, and d-axis compensation The means according to claim 2, further comprising means for setting a current i _dc as an addition value to the d-axis current command value and a q-axis compensation current i _qc as an addition value to the q-axis current command value. Torque pulsation suppression device for electric motors.   9. The dq-axis current command value compensated by the compensation current is used as an inverter current command value through a response compensation unit having an inverse transfer function of a transfer function expressing the response delay of the inverter. The torque pulsation suppressing device for an electric motor according to any one of claims. A torque-current command conversion unit that converts the torque command value of the motor into d and q-axis current components, and an output of the torque-current command conversion unit as a d and q-axis current command value. The current command value and the output of the inverter In the torque control device for an electric motor provided with an inverter that performs electric current control of the electric motor from the detected current value,
The pulsation compensation unit that suppresses the torque pulsation of the motor derives the torque pulsation generated due to the parameters of the motor, and a new current generated by superimposing the compensation current for compensating the torque pulsation on the current command of the inverter. A method for suppressing torque pulsation of an electric motor, wherein a current pulsation component is derived and a current compensation signal for canceling out the new pulsation component is added to an inverter current command.

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