JP2009072056A - Motor control device and method of controlling current phase - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control device which can reduce an operation processing time and generate a torque most efficiently with respect to the same current, for a brushless motor having inverse saliency. <P>SOLUTION: The device has current phase angle deriving means 11 for storing an advanced angle amount Φ of a current phase as a predetermined function corresponding to an absolute value (magnitude) of a current command. A current command value I* determined by dividing a torque command value T by a torque constant Kt, is input to an absolute value converter 12. An absolute value ¾I*¾ of obtained current command is input into the current phase angle deriving means 11. An advanced angle amount Φ (cosΦ and -sinΦ) corresponding to the absolute value ¾I*¾ of the current command, is derived. A q-axis current command value is obtained by multiplying the current command value I* by the advanced angle amount cosΦ. A d-axis current command value is obtained by multiplying the absolute value ¾I*¾ of the current command by the advanced angle amount -sinΦ. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor control device that controls the current phase of a brushless motor having reverse saliency and maximizes output torque at the same current.

  Conventionally, as a control method of a synchronous motor (PMSM: Permanent Magnet Synchronous Motor) using a magnet as a rotor, Id = 0 control in which a d-axis current is always kept at 0 is generally used.

The torque equation of PMSM is that the generated torque is T, the number of pole pairs is Pn, the armature flux linkage is Φa, the d-axis current is Id, the q-axis current is Iq, the d-axis inductance is Ld, and the q-axis inductance is Lq.
T = Pn × Φa × Iq + Pn × (Ld−Lq) × Id × Iq (Formula 1)
Can be expressed as

In Equation 1, if the d-axis current Id is kept at 0,
T = Pn × Φa × Iq (Formula 2)
It becomes. Since the generated torque T in Expression 2 is proportional only to the q-axis current Iq, linear control of the torque can be easily realized.

  On the other hand, in a synchronous motor (SPMSM: Surface Permanent Synchronous Motor) in which a magnet is arranged on the surface of the rotor, the d-axis inductance Ld and the q-axis inductance Lq have the same non-saliency, so the second term on the right side of Equation 1 Becomes 0, and the generated torque is expressed by Equation 2.

  Therefore, in the case of SPMSM, Id = 0 control that does not flow the d-axis current Id that does not contribute to torque generation is efficient because the current for the same torque is minimized.

  However, in a synchronous motor (IPMSM: Interior Permanent Synchronous Motor) in which a magnet is arranged in a rotor, the d-axis inductance Ld <reverse saliency of the q-axis inductance Lq has a reverse saliency. The reluctance torque of the second term cannot be used. For this reason, control with Id = 0 is not necessarily an appropriate control method.

  Therefore, a method has been proposed in which the d-axis current Id is set to a negative value and the generated torque is increased using the reluctance torque, which will be described with reference to FIG.

  The q-axis current command Iq * is calculated by dividing the torque command value T * by the q-axis current command calculation unit 51, which is obtained by multiplying a magnetic flux equivalent described later by a pole pair number Pn. Next, the q-axis current command Iq * or the q-axis current command feedback value Iq is input to the current phase angle control unit 52 and converted into the absolute value (magnitude) of the current command via the absolute value converter 53, and then the current phase angle. A d-axis current command Id * is calculated by multiplying -tan (β) by using the constant current phase angle β in the setting device 54.

  By causing the d-axis current feedback value Id to follow the d-axis current command Id *, reluctance torque is generated. The magnitude of the generated reluctance torque is taken into account based on the torque equation expressed by Equation 1.

In the reluctance torque consideration unit 55, the magnetic flux equivalent Φa + (Ld−Lq) × Id * is calculated from the armature interlinkage magnetic flux Φa, the q-axis inductance Lq, the d-axis inductance Ld, and the d-axis current command Id *. The calculated magnetic flux equivalent is used when the q-axis current command Iq * is calculated by multiplying the number of pole pairs Pn by the q-axis current command calculation unit 51 (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2000-92984

  However, the above prior art has the following problems.

First, the optimum current phase angle depends on the absolute value | I * | of the current command, that is, the magnitude of the current command. | I * | is obtained by the square root of (Id * ² + Iq * ² ). Therefore, if the d-axis current command Id * is calculated using the constant current phase angle β, the optimum current phase is not obtained.

  Further, in order to derive the q-axis inductance Lq from the q-axis current command Iq * and to calculate the q-axis current command Iq * from the q-axis inductance Lq, a convergence calculation is required, which increases the processing time.

  The present invention solves the above-described conventional problems, and is a motor control capable of generating torque most efficiently for the same current for a brushless motor having a reverse saliency with a short calculation processing time. An object is to provide an apparatus.

  In order to solve the above-mentioned problem, the motor control device according to claim 1 is a current phase control of a motor with a built-in magnet that maximizes an output torque at the same current. Current phase advance amount deriving means stored as a predetermined function corresponding to the magnitude), and the current command value obtained by dividing the torque command value by the torque constant is input to the absolute value converter and obtained The absolute value of the current command is input to the current phase advance amount deriving means to derive the advance amount Φ (cos Φ and −sin Φ) corresponding to the absolute value of the current command, and the advance amount cos Φ is derived from the current command value. To obtain the q-axis current command value, and multiply the magnitude of the current command by the advance amount −sinΦ to obtain the d-axis current command value.

  According to a second aspect of the present invention, there is provided a current phase control method comprising current phase advance amount deriving means for storing the current phase advance amount as a predetermined function corresponding to the absolute value (size) of the current command. , Step 1 for converting the torque command value into a current command value, step 2 for converting the current command value into an absolute value of the current command, and inputting the absolute value of the current command into the current phase advance amount deriving means; Step 3 for deriving an advance amount Φ (cos Φ and −sin Φ) corresponding to the absolute value of the current command, and multiplying the current command value in Step 1 by cos Φ obtained in Step 3 to obtain a q-axis current command value 3 is obtained by multiplying -sinΦ obtained in step 3 by the absolute value of the current command to obtain d-axis current command values, respectively. The actual q-axis current value and d-axis current value calculated from the actual motor current are Q-axis current command value obtained in step 4 Feedback is performed so as to follow the d-axis current command value, and the output torque of the brushless motor having the reverse saliency at the same current is maximized.

  According to the motor control device of the first aspect, by providing the current phase advance amount deriving means, it becomes possible to control the advance angle of the optimum current phase according to the absolute value of the input current command, and this is desired. Torque control that minimizes the current required to obtain the output torque can be realized.

  According to the current phase control method of the second aspect, the maximum torque control that minimizes the current required to obtain the desired output torque can be realized by four steps.

  Therefore, it is possible to provide a motor control device that can efficiently drive a magnet-embedded motor.

A step 1 for converting the torque command value into a current command value, comprising: a current phase advance amount deriving unit that stores the current phase advance amount as a predetermined function corresponding to the absolute value (magnitude) of the current command; Step 2 for converting the current command value to the absolute value of the current command, and the magnitude of the current command is input to the current phase angle deriving means, and the advance amount Φ (cosΦ and −sinΦ) corresponding to the absolute value of the current command In step 3, the current command value in step 1 is multiplied by cosΦ obtained in step 3, and the q-axis current command value is multiplied by -sinΦ obtained in step 3, and the absolute value of the current command is multiplied by d-axis. Steps 4 for obtaining current command values are provided, and the actual q-axis current value and d-axis current value calculated from the actual motor current follow the q-axis current command value and d-axis current command value obtained in Step 4. So that the feedback is the same This is a method for controlling the current phase of a magnet-embedded motor that maximizes output torque in current. Hereinafter, embodiments will be described.
(Embodiment 1)
The first embodiment will be described in detail with reference to FIGS. FIG. 1 is an explanatory diagram of a current phase advance amount derivation means that is a main part of the present invention, FIG. 2 is a block diagram of a current control system in a motor control device, and FIG. FIG. 4 is an explanatory diagram of the d-axis and q-axis inductance characteristics of a brushless motor having a reverse saliency.

  FIG. 1 shows a current phase advance amount deriving unit for deriving the advance amount of the current phase and its surroundings. The current phase advance unit 11 represents the advance amount Φ as a factor | I * |. It is memorized as a function. This function is obtained by deriving and approximating the optimum current phase angle corresponding to the absolute value of each current command from the simulation and the actual measurement results.

  The current command value I * is obtained by dividing the torque command value T by the torque constant Kt (step 1). This current command value I * is input to the absolute value converter 12, and the absolute value of the current command | I * | (Step 2) and input to the current phase advance means 11. The current phase advance means 11 derives −sinΦ and cosΦ as phase advance amounts corresponding to the absolute value | I * | of the input current command (step 3).

  The torque component current command value Iq * as the q-axis current command is obtained by multiplying the current command value I * by cosΦ, and the excitation component current command value Id * as the d-axis current command is the absolute value | I of the current command. * | Is multiplied by -sinΦ (step 4). Current control using the excitation current command value Id * and the torque current command value Iq * will be described with reference to FIG.

  In FIG. 2, an excitation current command value Id * and a torque component current command value Iq * are obtained from a torque command value T * obtained from a speed control system (not shown) using the current phase advance means 11 as described in FIG. Derived.

  The d-axis voltage command value Vd * and the q-axis voltage command value Vq * are the excitation current command value Id *, the torque current command value Iq *, the excitation current feedback value Id obtained from the 3-phase / 2-phase converter 27, and Deviations from the torque current feedback value Iq are calculated by the PI controller 22, respectively.

The d-axis voltage command value Vd * and the q-axis voltage command value Vq * are converted into a three-phase AC voltage command value Vu * and an AC voltage command value Vv * using the current phase angle θ by the two-phase / three-phase converter 23. The three-phase AC voltage converted into the AC voltage command value Vw * and amplified by the power converter 24 is input to the magnet-embedded motor 26 having reverse saliency.

  The three-phase AC current value Iu and the AC current value Iv supplied to the magnet-embedded motor 26 are detected by a current detector 25, and a current phase angle θ is detected by a three-phase / two-phase converter 27, thereby exciting current. It converts into the feedback value Id and the torque current feedback value Iq.

  Next, the relationship between the current phase angle, output torque, and current of a magnet-embedded motor having reverse saliency will be described with reference to FIG. In FIG. 3, the current phase angle when current flows in the q-axis direction orthogonal to the d-axis, which is the magnetic flux direction of the permanent magnet, is shown as 0.

  The output torque of the magnet-embedded motor having the reverse saliency is the sum of the magnet torque generated by the permanent magnet and the reluctance torque resulting from the saliency as represented by Equation 1. Therefore, there is a current phase advance amount Φ that maximizes the output torque when a certain constant current is input.

  However, the d-axis inductance Ld and the q-axis inductance Lq depend on the magnitudes of the excitation current feedback value Id and the torque component current feedback value Iq, and have the relationship shown in FIG. Therefore, when the absolute value of the current changes, the d-axis inductance Ld and the q-axis inductance Lq also change, so the advance amount Φ changes depending on the absolute value of the current.

  In the present invention, focusing on this relationship, the current phase advance amount is stored in the current phase advance means as a predetermined function corresponding to the absolute value of the current command, and is determined according to the absolute value of the input current command. The excitation current command value Id * and the torque component current command value Iq * can be derived from the advance amount Φ.

  As a result, torque control that minimizes the current required to obtain the desired output torque can be realized.

  The motor control device of the present invention is optimal for high-efficiency driving of a brushless motor having reverse saliency such as a magnet-embedded motor, and is useful for high output.

Explanatory drawing of the electric current phase advance amount derivation | leading-out means in Embodiment 1 of this invention Block diagram of current control system of motor control device in Embodiment 1 of the present invention Illustration of torque-current phase angle curve of brushless motor with reverse saliency D-axis and q-axis inductance characteristics of brushless motor with reverse saliency Block diagram of main parts of current control system in conventional motor control device

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Current phase advance means 12 Absolute value converter 21 Current command value calculating circuit 22 PI controller 23 Two-phase / 3-phase converter 24 Power converter 25 Current detector 26 Magnet built-in type motor (brushless motor having reverse saliency) )
27 3-phase / 2-phase converter 51 q-axis current command calculation unit 52 current phase angle control unit 53 absolute value converter 54 current phase angle setting unit 55 reluctance torque consideration unit

Claims (2)

In the current phase control of the motor, there is provided a current phase advance amount deriving means for storing the advance amount of the current phase as a predetermined function corresponding to the absolute value (magnitude) of the current command, and the torque command value as a torque constant. The current command value obtained by division is input to the absolute value converter, and the absolute value of the obtained current command is input to the current phase advance amount deriving means, and the advance amount according to the absolute value of the current command Deriving Φ (cos Φ and −sin Φ), multiplying the current command value by the advance amount cos Φ to obtain a q-axis current command value, and multiplying the magnitude of the current command by the advance angle amount −sin Φ, the d-axis current command value A motor control device characterized by that. A step 1 for converting the torque command value into a current command value, comprising: a current phase advance amount deriving unit that stores the current phase advance amount as a predetermined function corresponding to the absolute value (magnitude) of the current command; Step 2 for converting the current command value into an absolute value of the current command, and inputting the absolute value of the current command into the current phase advance amount deriving means, and an advance amount Φ (cos Φ and -SinΦ) is obtained by multiplying the current command value of step 3 by the current command value of step 1 by cos Φ obtained in step 3 and the q-axis current command value, and -sinΦ obtained in step 3 by the absolute value of the current command. The d-axis current command value and the d-axis current command value obtained in step 4 are obtained by calculating the actual q-axis current value and the d-axis current value calculated from the actual motor current. Feedback to follow Control method of current phase to be controlled.

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