JP2005354779A - Motor control device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently drive a motor by minimizing the total loss of the motor. <P>SOLUTION: This motor control device drives the motor 2 by generating a d-axis current and a q-axis current that correspond to torque commands T<SP>*</SP>, and comprises a rotational speed detection means 1 that detects the number of revolutions of the motor 2, on the basis of all the loss of the motor 2 classified as below a conversion table 8a that regulates in advance the torque commands T<SP>*</SP>, the d-axis current i<SB>d</SB>and the q-axis current i<SB>q</SB>for minimizing the total loss with respect to the number N of revolutions of the motor. There is established an expression: the total loss=iron loss (fundamental wave iron loss (I, θ, N)+harmonic iron loss (I, θ, N)+carrier iron loss (I, θ, N))+copper loss (I)+mechanical loss (N). Here, I is a motor current, θ is a current phase, and N is the number of revolutions of the motor. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor control apparatus and method for driving a motor by generating d and q axis currents corresponding to a torque command.

In order to operate a motor such as an IPM motor with high efficiency, an appropriate combination of d-axis current and q-axis current corresponding to a combination of torque command, motor rotation speed and motor temperature (for example, the motor efficiency is maximized) A held current map is formed in advance, and a d-axis current and a q-axis current corresponding to a combination of the torque command and the motor rotational speed are obtained from the current map, and the d-axis current and the q-axis current are determined as d, q A technique for controlling a motor as an axis current command has been proposed. (For example, Patent Document 1)
According to this prior art, an appropriate d and q axis current command corresponding to the motor temperature at that time can be obtained, so that the efficiency of the motor can be improved.
JP 2003-47300 A

  The motor temperature affects the iron loss of the motor. However, the above prior art does not take into account the total loss of the motor including iron loss, copper loss and mechanical loss, and therefore it is not possible to sufficiently suppress the reduction in efficiency of the motor due to the total iron loss. was there.

  In view of such circumstances, an object of the present invention is to set a d and q axis current command capable of minimizing the total loss of the motor, and to operate the motor extremely efficiently. It is to provide a method.

The present invention is a motor control device that drives a motor by generating d and q axis currents corresponding to a torque command, and is classified as follows: a rotation speed detection means for detecting the rotation speed N of the motor; A conversion table that preliminarily defines the d and q axis currents i _d and i _q for minimizing the total loss with respect to the torque command T ^* and the motor rotation speed N based on the total loss of the motor; And the motor is controlled such that the d and q axis currents i _d and i _q obtained by the conversion table flow to the motor.
Total loss = Iron loss (Basic wave iron loss (I, θ, N) + Harmonic iron loss (I, θ, N)
+ Carrier iron loss (I, θ, N)) + copper loss (I) + mechanical loss (N)
Where I: motor current, θ: current phase, N: motor rotation speed

  In this motor control device, for example, an IPM motor is used as the motor. The motor control device can include power conversion means for converting the DC output power of the battery into AC power corresponding to the d and q axis current commands and supplying the AC power to the motor. In this case, it is desirable to provide a plurality of conversion tables in order to cope with a plurality of voltages of the battery.

The present invention also provides a motor control method for driving a motor by generating d and q axis currents corresponding to a torque command, the step of detecting the rotational speed of the motor, and the motors classified as follows: _Generating a conversion table that predefines the d and q axis currents i _d and i _q for minimizing the total loss with respect to the torque command and the motor rotational speed, and the conversion Controlling the motor such that the d and q axis currents i _d and i _q obtained by the table flow to the motor. .
Total loss = Iron loss (Basic wave iron loss (I, θ, N) + Harmonic iron loss (I, θ, N)
+ Carrier iron loss (I, θ, N)) + copper loss (I) + mechanical loss (N)
Where I: motor current, θ: current phase, N: motor rotation speed

  According to the present invention, the d and q axis currents that minimize the total loss of the motor including iron loss, copper loss and mechanical loss are set, and the motor is driven by the d and q axis currents. Therefore, the driving efficiency of the motor can be significantly improved. Further, since the d and q axis currents that minimize the total loss are defined by the table, that is, it is not necessary to calculate the d and q axis currents by a calculation means such as a CPU. The burden can be reduced.

  FIG. 1 shows an embodiment of a motor control device according to the present invention. Although the motor control apparatus according to this embodiment is applied to control of a three-phase IPM motor, other motors (an IPM motor having a larger number of phases than a three-phase, a multi-phase induction motor, a multi-phase synchronous reluctance) It can also be applied to control of a motor or the like.

In FIG. 1, a speed / position calculator 1 calculates the rotational speed N and current phase (rotational position) θ of the IPM motor 2 based on the AB phase pulse signal of the IPM motor 2 or the output of the resolver 3. The A / D conversion unit 4 performs A / D conversion on the currents i _u , i _v , and i _w flowing through the IPM motor 2 and outputs them to the three-phase / two-phase conversion unit 5. The three-phase / two-phase converter 5 converts the three-phase motor currents i _u , i _v , i _w into two-phase currents based on the current phase θ of the motor 2 and a known three-phase / 2-phase conversion formula. i _d , i _q , that is, d, q axis currents i _d , i _q for so-called vector control.

In this motor control device, the analog torque command T ^* is converted into a digital torque command T ^* by the A / D converter 6. The ramp processing unit 7 performs a ramp process on the digital torque command T ^* based on a ramp function as shown in the figure, and outputs the ramped torque command T ^* to the current command creation unit 8.
The current command generator 8 sets current commands i ^* _d and i ^* _q that minimize the total loss of the motor 2 based on the given torque command T ^* and the motor rotation speed N. A detailed description of the current command generator 8 will be described later.

The PI controller 9 outputs the d and q axis current commands i ^* _d and i ^* _q output from the current command generator 8 and the actual currents i _d and i of the motor 2 output from the three-phase / two-phase converter 3. PI (proportional / integral) processing is performed on the deviation from _q, and voltage commands v ^* _d and v ^* _q corresponding to the deviation are output. The voltage commands v ^* _d and v ^* _q output from the PI control unit 9 are input to the two-phase / three-phase conversion unit 11 via the limiter 10.

The 2-phase / 3-phase converter 11 converts the voltage commands v ^* _d , v ^* _q into a 3-phase voltage command v ^* based on the current phase θ of the motor 2 and a known 2-phase / 3-phase conversion equation ^. Convert to _u , v ^* _v , v ^* _w . The voltage commands v ^* _u , v ^* _v , and v ^* _w output from the two-phase / three-phase converter 11 are injected with the third harmonic by the third harmonic injector 12 and the duty calculator 13. After the duty ratio for PWM control is set, the signal is input to the inverter 14. Therefore, the inverter 14 converts the DC output power of a battery (not shown) into power corresponding to the voltage commands v ^* _u , v ^* _v , v ^* _w and supplies this power to the IPM motor 2.
As a result, according to this motor control device, the IPM motor 2 is driven so as to generate torque corresponding to the torque command T ^* .

Here, the loss of a motor such as the IPM motor 2 will be described. The total loss of the motor is expressed as follows:
Total loss (W) = Copper loss (Wc) + Iron loss (Wi) + Mechanical loss (Wm) (1)
Of the total loss (W), the copper loss (Wc) and the mechanical loss (Wm) are given by the following equations (2) and (3), respectively.
Wc = n × R × I ² = Wc (I) (2)
Where n: number of phases, R: winding resistance (Ω), I: motor current (Arms).
Wm = 8 × D × (l1 + 15) × va ² × 10 ⁴ = Wm (N) (3)
Here, D: outer diameter of the rotor (cm), l1: iron core thickness (cm), va: peripheral speed (m / s) of the rotor surface, N: motor rotation speed.
As is apparent from the above equations (2) and (3), the copper loss Wc and the mechanical loss Wm are given by the motor current I and the motor rotation speed N, respectively. That is, the copper loss Wc and the mechanical loss Wm are expressed as Wc (I) and Wm (N), respectively.

On the other hand, iron loss is classified as follows.
Iron loss (Wi) = Fundamental wave iron loss (Wif) + Harmonic iron loss (Wih)
+ Carrier iron loss (Wic) (4)
The fundamental iron loss Wif, the harmonic iron loss Wih, and the carrier iron loss Wic are given by the following equations (5), (6), and (7), respectively.
Wif = K _e1 · f ₁ ² · B ₁ ² + K _h1 · f ₁ · B ₁ ² (5)
_{Wih = Σ n (K en ·} f n 2 · B n 2) ··· (6)
Wic = Σ _m (K _em · f _m ² · B _m ² + K _hm · f _m · B _m ² ) (7)
Here, B _{1 is} a magnetic flux component of the fundamental frequency f ₁ , B _{n is} a magnetic flux component of the frequency f ₁ × n, and B _{m is} a magnetic flux component of the carrier frequency f _c × m of the PWM control.
n and m are orders, and the upper limit order employed in the calculation of the loss is generally up to the ninth order.

The fundamental frequency f ₁ is the rotational speed N, the magnetic flux components B ₁ , B _n , B _m are the current I and the current phase θ,
The coefficients K _e1 and K _h1 are the magnetic flux component B ₁ and the fundamental frequency f ₁ , the coefficients K _en and K _hn are the magnetic flux component B _n and the fundamental frequency f _n , and the coefficients K _em and K _hm are the magnetic flux component B _m and the carrier frequency. in f _c, respectively, are determined.

As is apparent from the above description, the fundamental wave iron loss Wif, the harmonic iron loss Wih, and the carrier iron loss Wic are given from the current I, the current phase θ, and the rotational speed N.
FIG. 3 shows the relationship among copper loss Wc, iron loss Wi (fundamental iron loss Wif + harmonic iron loss Wih + carrier iron loss Wic), mechanical loss Wm, current I, current phase θ, and rotational speed N. It is a thing.

Next, the current command creation unit 8 will be described.
The torque of the three-phase IPM motor is expressed as follows using the current I and the current phase θ.
T = Pn × [√3 × φa × I × cos θ + (3/2) × (Ld + Lq) × I ² × sin 2θ]
... (8)
Here, Pn: number of counter electrodes, φa: flux linkage [Wb], Ld: d-axis inductance [H], and Lq: q-axis inductance [H].

  In this three-phase IPM motor, there are innumerable combinations of current I and current phase θ that output the same torque. However, as described above, since the copper loss Wc is defined by the current I, the iron loss Wi is defined by the current I, the current phase θ and the rotational speed N, and the mechanical loss Wm is defined by N, the torque, the motor rotational speed N, and Is given, it is possible to set the combination of the current I and the current phase θ that minimizes the total loss (W) among the various combinations of the current I and the current phase θ that realize the torque. .

The conversion table 8 of the current command creation unit 8 is created based on the above consideration. That is, in creating the conversion table 8, the relationship Wif (Σ, θ, N) between the fundamental wave iron loss (Wif) and Σ, θ, and N is calculated using an FEM analysis method or the like, and the harmonic iron The relationship Wih (Σ, θ, N) between the loss (Wih) and Σ, θ and N is calculated. Further, the relationship Wic (Σ, θ, N) between the carrier iron loss (Wic) and Σ, θ, and N is also obtained by calculation.
Next, a combination of the current I and the current phase θ that minimizes the total loss (W) with respect to various torque commands T ^* and the motor rotational speed N is expressed by the above relations Wif (Σ, θ, N), Wih ( The conversion table 8 is created by making a decision based on Σ, θ, N), Wic (Σ, θ, N) and the relations Wc (I) and Wm (N) and tabulating this combination.
Therefore, when the torque command T ^* and the motor rotation speed N are given to the current command creation unit 8, the optimum combination of the current I and the current phase θ that minimizes the total loss (W) is set by the conversion table 8a.
The current I can be converted into a d-axis current i _d and a q-axis current i _q based on the current phase θ. The actual outputs of the conversion table 8a are the d-axis current i _d and the q-axis current i _q .

According to the motor control device and the motor control method according to this embodiment including the current command generating unit 8 as described above, the d and q-axis currents that minimize the total loss are uniquely set in the current command generating unit 8. The d and q axis currents are output from the current command generator 8 as d and q axis current commands i ^* _d and i ^* _q . Therefore, the motor 2 can be efficiently operated so that the total loss is minimized. In addition, since it is not necessary to calculate the d, q-axis current commands i ^* _d , i ^* _q by a calculation means such as a CPU, the burden on the control calculation means is reduced.

The motor control device and the motor control method according to the embodiment are applied to control of motors used in, for example, EVs (electric vehicles), HEVs (hybrid vehicles), forklifts, special vehicles, various robots, trains, and the like. can do.
By the way, the above-mentioned various motor drive devices are equipped with a battery having an output voltage corresponding to the model. In order to cope with this, the current command generation unit 8 may be provided with a plurality of conversion tables adapted to various battery output voltages, and the conversion table corresponding to the battery output voltage may be selected. FIG. 2 shows a plurality of conversion tables 8a-1 to 8a-N adapted to the output voltages V1, V2, V3... VN of various batteries.

It is a block diagram showing an embodiment of a motor control device concerning the present invention. It is a block diagram which shows the some conversion table adapted to battery voltage V1, V2, V3 ... VN. It is the block diagram which showed the relationship between copper loss, iron loss (fundamental wave iron loss, harmonic iron loss, carrier iron loss) and mechanical loss, and an electric current, a current phase, and a motor rotation speed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Speed / position calculation part 2 IPM motor 3 Resolver 4,6 A / D conversion part 5 3 phase / 2 phase conversion part 8 Current command preparation part 8a, 8a-1-8a-N Conversion table 9 PI control part 11 2 phase / 3 phase converter 14 Inverter

Claims (4)

A motor control device for driving a motor by generating d and q axis currents corresponding to a torque command,
A rotational speed detection means for detecting the rotational speed of the motor;
A conversion table in which the d and q axis currents i _d and i _q for minimizing the total loss with respect to the torque command and the motor rotational speed are preliminarily defined based on the total loss of the motor classified as follows. And comprising
A motor control device that controls the motor such that the d and q axis currents i _d and i _q obtained by the conversion table flow to the motor.
Total loss = Iron loss (Basic wave iron loss (I, θ, N) + Harmonic iron loss (I, θ, N)
+ Carrier iron loss (I, θ, N)) + Copper loss (I) + Mechanical loss (N)
Where I: motor current, θ: current phase, N: motor speed   The motor control apparatus according to claim 1, wherein the motor is an IPM motor.   Power conversion means for converting the DC output power of the battery into AC power corresponding to the d and q axis current commands and supplying it to the motor is provided, and a plurality of the conversion tables are provided to correspond to the plurality of voltages of the battery. The motor control device according to claim 1. A motor control method for driving a motor by generating d and q axis currents corresponding to a torque command,
Detecting the number of rotations of the motor;
A conversion table in which the d and q axis currents i _d and i _q for minimizing the total loss with respect to the torque command and the motor rotational speed are preliminarily defined based on the total loss of the motor classified as follows. The steps of creating
Controlling the motor such that the d and q axis currents i _d and i _q obtained by the conversion table flow to the motor;
A motor control method comprising:
Total loss = Iron loss (Basic wave iron loss (I, θ, N) + Harmonic iron loss (I, θ, N)
+ Carrier iron loss (I, θ, N)) + Copper loss (I) + Mechanical loss (N)
Where I: motor current, θ: current phase, N: motor speed

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