JP5396906B2 - Electric motor drive control device - Google Patents

Description

  The present invention relates to a drive control device for an electric motor.

PWM current control for supplying a sine wave current of amplitude and phase according to the torque command to the motor, and voltage phase control for supplying an alternating current with a phase out of a predetermined phase according to the torque command to the motor according to the torque command There is known a drive control device for an electric motor to be switched (Patent Document 1).

In this motor drive control device, the drive phase is controlled by voltage phase control, and the advance and delay between the current phase of the alternating current supplied to the motor and the control switching phase corresponding to the predetermined phase according to the torque command. When the relationship is reversed, the control is switched to the PWM current control control.

JP 2001-78495 A

  In the conventional motor drive control device, in order to prevent frequent switching between voltage phase control and PWM current control, a hysteresis may be provided by shifting the switching threshold (see paragraph [Patent Document 1] 0041]).

However, if the switching threshold is shifted in order to provide hysteresis, there is a problem that a torque step occurs when the temperature of the permanent magnet of the motor fluctuates.
The problem to be solved by the present invention is to provide a drive control device for an electric motor that can suppress the occurrence of a torque step due to fluctuations in magnet temperature.

The present invention solves the above problem by estimating the temperature of the permanent magnet of the AC motor, calculating the torque during voltage phase control and the torque during PWM current control, and correcting the torque command value after switching.

  According to the present invention, the temperature of the permanent magnet of the AC motor is estimated, and the torque at the time of voltage phase control and the torque at the time of PWM current control are calculated, so that the torque value before and after switching can be corrected to be equal. In addition, it is possible to suppress the occurrence of a torque step due to fluctuations in the temperature of the permanent magnet.

It is a block diagram which shows the drive control apparatus of the electric motor which concerns on one embodiment of this invention. It is a block diagram which shows the structure regarding PWM current control among the drive control apparatuses of FIG. It is a block diagram which shows the structure regarding voltage phase control among the drive control apparatuses of FIG. 2 is a graph showing the relationship between dq-axis current and control in the motor drive control device of FIG. 1. It is a graph which shows the relationship between torque-rotation speed and control in the drive control apparatus of the electric motor of FIG. It is a graph which shows the relationship between the electric current drive voltage-rotation speed and control in the drive control apparatus of the electric motor of FIG. 2 is a graph showing the relationship between dq-axis current and control when hysteresis is set in the drive control apparatus for the electric motor of FIG. 1. It is a graph which shows the relationship between torque-rotation speed and control at the time of setting a hysteresis in the drive control apparatus of the electric motor of FIG. FIG. 3 is a graph showing a control switching state in the motor drive control device of FIG. 1 when the magnet temperature does not change. FIG. FIG. 3 is a graph showing a state in which control is switched in the motor drive control device of FIG. 1 and a torque command value is not corrected based on a magnet temperature. FIG. FIG. 3 is a graph showing a state of control switching in the electric motor drive control device of FIG. 1 when a torque command value is corrected based on a magnet temperature. FIG. It is a graph which shows the relationship of the correction torque-rotation speed in the drive control apparatus of the electric motor of FIG. It is a graph which shows the correction torque-time relationship in the drive control apparatus of the electric motor of FIG.

  Hereinafter, embodiments of the invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing the entire drive control apparatus for an electric motor according to the present embodiment, FIG. 2 is a block diagram showing the configuration of PWM current control extracted from the configuration of FIG. 1, and FIG. It is a block diagram which extracts and shows the structure of voltage phase control among these structures.

  The motor drive control device of the present embodiment shown in FIG. 1 is mounted on an electric vehicle, for example, and drives and controls a three-phase AC motor M, and has two control modes of PWM current control and voltage phase control. The PWM current control mode and the voltage phase control mode are switched by the control switching unit 15.

In the PWM current control mode shown in FIG. 2, at the time of a predetermined phase of the PWM carrier signal, the control map 11 is the torque command value T ^* [N · m] and the rotor angular velocity (electrical angle) of the electric motor M. Based on the rotational speed ω [rad / s] and the DC voltage Vdc [V] of the power source 1, the current target values i ^* _d [A] and i ^* _q [A] of the d-axis and q-axis of the AC motor M are preliminarily determined. Obtained from the set control map.
The current control calculation unit 13 calculates the d-axis voltage command value ν ^* _d and the q-axis voltage command for the d-axis and q-axis of the AC motor M according to the following formula 1 at the time of a predetermined phase in the next carrier cycle of the PWM carrier signal. The value ν ^* _q is output.

The three-phase-dq converter 6 converts the three-phase current values i _u , i _v , i _w output from the inverter 2 to the motor M into the dq-axis current values i _d , i _{q according} to the following mathematical formula 4.

なお、インバータ２から電動機Ｍに出力される三相電流値ｉ_ｕ［Ａ］，ｉ_ｖ［Ａ］，ｉ_ｗ［Ａ］は電流センサにより検出することができ、電動機Ｍの回転子位相（電気角）θ［ｒａｄ］は、レゾルバやエンコーダなどの位置検出器により検出することができ、電動機Ｍの回転子角速度（電気角）ω［ｒａｄ／ｓ］は、微分回路８にて上記θ［ｒａｄ］を微分することにより演算で求めることができる。

The three-phase current values i _u [A], i _v [A], i _w [A] output from the inverter 2 to the electric motor M can be detected by a current sensor, and the rotor phase (electricity) of the electric motor M can be detected. (Angle) θ [rad] can be detected by a position detector such as a resolver or an encoder, and the rotor angular velocity (electrical angle) ω [rad / s] of the electric motor M is calculated by the differentiation circuit 8 by the above θ [rad]. ] Can be obtained by calculation.

Next, in the voltage phase control mode shown in FIG. 3, at the time of the predetermined phase of the PWM carrier signal, the control map 12 is the torque command value T ^* [N · m] and the rotor angular velocity (electrical angle) of the motor M. From the rotational speed ω [rad / s] and the DC voltage Vdc [V] of the power source 1, the voltage amplitude Va [V] and the voltage phase α [°] are obtained from a preset control map.

The voltage command value calculation unit 14 outputs the d-axis voltage command value ν ^* _d and the q-axis voltage command value ν ^* _{q according} to the following formula 5 at the time of a predetermined phase in the next carrier cycle of the PWM carrier signal .

この後のｄｑ−三相変換部５、ＰＷＭ変換部４、デッドタイム補償部３は上述したＰＷＭ電流制御モードと同じ処理を行い、ＰＷＭ指令（パルス幅）に従ってインバータを駆動することにより、電動機Ｍに電圧ν_ｕ，ν_ｖ，ν_ｗを印加して駆動する。

Thereafter, the dq-three-phase converter 5, the PWM converter 4, and the dead time compensator 3 perform the same processing as in the PWM current control mode described above, and drive the inverter according to the PWM command (pulse width). Are driven by applying voltages ν _u , ν _v , and ν _w to.

  Now, the torque equation of the motor is expressed by the following formula 6, and the dq axis voltage equation (steady state) is expressed by the following formula 7.

但し、上記数式６においてｐは電動機Ｍの極対数、Φａは磁石磁束［Ｗｅｂ］、Ｌｄはｄ軸インダクタンス［Ｈ］、Ｌｑはｑ軸インダクタンス［Ｈ］、上記数式７においてＲａは巻線抵抗［Ω］である。

Where p is the number of pole pairs of the motor M, Φa is the magnetic flux [Web], Ld is the d-axis inductance [H], Lq is the q-axis inductance [H], and Ra is the winding resistance [ Ω].

  Further, it is known that the magnetic flux Φa of the permanent magnet of the electric motor M varies depending on the temperature of the magnet, and the magnetic flux decreases as the magnet temperature increases, and the magnetic flux increases as the magnet temperature decreases.

  For this reason, since the control maps 11 and 12 used for PWM current control and voltage phase control are acquired at a specific magnet temperature, in the PWM current control mode, the amount of change in the magnetic flux Φa as apparent from Equation 6 above. Only the torque T fluctuates. Further, in the voltage phase control mode, the current value also changes due to the change of the magnet magnetic flux Φa, as is clear from Equation 7, so that the output torque is the same in the PWM current control mode and the voltage phase control mode even when the same magnet temperature changes. Different.

  Returning to FIG. 1, the switching control unit 15 of this example performs switching from the voltage phase control mode to the PWM current control mode using the current vector. FIG. 4 shows the relationship between the dq-axis current value and the control, and FIG. 5 shows the relationship between the rotation speed-torque and the control. FIG. 6 shows the relationship between the rotation speed and the voltage / current.

As shown in FIG. 6, when the rotational speed increases from point C to point A in the PWM current control mode, the voltage increases, and when a certain threshold value is exceeded, the mode is switched to the voltage phase control mode. Further, as shown in FIG. 4, in the voltage phase control mode, the d-axis current flows more than the current vector in the PWM current control mode.

Then, as shown in FIG. 5, when the rotation speed changes from the point A to the point C in the voltage phase control mode, the dq axis current in FIG. 4 becomes the PWM current control line (dq axis current command value calculated by the control map 11). When the PWM current control line is reached, the voltage phase control mode is switched to the PWM current control mode.
By the way, when the switching control unit 15 performs the switching determination as described above, switching between both modes, that is, a so-called hunting phenomenon frequently occurs due to fluctuations in the rotation speed, sensor errors, and the like.
Therefore, in order to prevent such frequent switching, the switching control unit 15 of this example sets a switching threshold line P in which the d-axis current value is larger than the PWM current control line by the amount of hysteresis as shown in FIG. The rotation speed at the intersection of this line and the current value in the voltage phase control mode is D point.
FIG. 8 is a graph showing the relationship between the rotational speed-torque and the control when the switching threshold line P is set in this way. The rotational speed at point D is smaller than the rotational speed at point B. Therefore, when the voltage phase control mode is switched from the voltage phase control mode to the PWM current control mode at the point D, a step is generated in the voltage, and thus frequent switching can be suppressed.
In the switching control between the voltage phase control mode and the PWM current control mode, the switching threshold line P shown in FIG. 7 is shifted from the PMW current control line in the d-axis direction in which the d-axis current increases, thereby suppressing frequent switching. However, if the temperature of the permanent magnet of the electric motor M fluctuates, a new problem arises that a torque step occurs when the control mode is switched.
The torque step at the time of switching the control mode with respect to the magnet temperature change will be described.
FIG. 9 shows the torque command value, output torque, and output torque when the rotational speed changes from A → B → D → C when the magnet temperature does not change, that is, when the control maps 11 and 12 do not change at the magnet temperature acquired. It is a graph which shows a voltage and an electric current. In this case, as shown in FIG. 9, there is no step in the output torque because the output torque is the same as the torque command value in both the PWM current control mode and the voltage phase control mode.
On the other hand, FIG. 10 shows A → B → D → C when the magnet temperature fluctuates, that is, when the magnet temperature is higher than the magnet temperature when the control maps 11 and 12 are acquired and the magnet magnetic flux is reduced. It is a graph which shows a torque command value, output torque, a voltage, and an electric current when a rotation speed changes. In this case, as shown in FIG. 10, when the magnet temperature varies, the output torque in the voltage phase control mode does not follow the torque command value. In this state, when the rotational speed decreases and the point changes to PWM current control at point D, the output torque in the PWM current control mode is different from the output torque in the voltage phase control mode. Occur.

Therefore, the torque correction calculation unit 10 to which this embodiment is applied will be described. FIG. 11 shows that when the magnet temperature fluctuates, that is, when the magnet temperature is higher than the magnet temperature obtained from the control maps 11 and 12 and the magnetic flux is reduced, the rotational speed changes from A → B → D → C. It is a graph which shows a torque command value, output torque, voltage, and current at the time. In the case of this example, as shown in FIG. 11, the output torque in the voltage phase control mode is not the same as the torque command value as in the example of FIG.

However, in this state, when the rotational speed decreases and becomes the D point and the switching condition is satisfied, the torque correction calculation unit 10 calculates a correction torque that takes into account the fluctuation of the magnetic flux due to the fluctuation of the magnet temperature. The current command value is calculated from the control map 11 in the PWM current control mode using the corrected torque command value.

  Thereby, even if the output torque is different from the torque command value as shown in FIG. 11, the step of the output torque when the control mode is switched can be suppressed.

  Here, the magnet temperature is estimated and calculated by the magnet temperature estimation unit 9, and can be estimated from the power, the rotational speed, the voltage phase, and the voltage amplitude. The correction torque is calculated by the torque correction calculation unit 10 as described above, and the estimated torque T1 of the voltage phase control mode using the estimated magnet temperature and the estimation of the PWM current control mode using the estimated magnet temperature. A current value (a value on the PWM current control line in FIG. 7) that matches the torque T2 can be calculated and calculated.

  Incidentally, an example of estimating the magnet temperature (magnet magnetic flux) from the estimated torque in the voltage phase control mode will be described.

  The torque formula of the electric motor is the following formula 8, and the steady-state voltage equation is the following formula 9 (the same as the above-described formula 6 and formula 7).

ここで電圧位相制御モードの電圧振幅と位相をＶ_ａ・αとすると下記数式１０が成立する。

Here following equation 10 is established when the voltage amplitude and phase of the voltage phase control mode and V _a · α.

上記数式９をｉ_ｄで整理すると、下記数式１１となる。

Rearranging the above equation 9 _{i d,} the following equation 11.

上記数式１１からｉ_ｄを消去してｉ_ｑで整理すると、

さらに上記数式１２を変形して、

さらに上記数式１３を整理して、

電動機Ｍの回転子角速度（電気角）ω［ｒａｄ／ｓ］、ｄ軸インダクタンスＬｄ［Ｈ］、ｑ軸インダクタンスＬｑ［Ｈ］、巻線抵抗Ｒａ［Ω］が既知であるとすると、上記数式１４はＡ，Ｂを定数として下記数式１５のように整理できる。

To summarize in _{i q} to erase _{i d} from the equation 11,

Furthermore, the above formula 12 is modified,

Furthermore, the above formula 13 is arranged,

Assuming that the rotor angular velocity (electrical angle) ω [rad / s], d-axis inductance Ld [H], q-axis inductance Lq [H], and winding resistance Ra [Ω] of the motor M are known, the above formula 14 Can be arranged as shown in the following formula 15, with A and B as constants.

このｉ_ｑと同様にしてｉ_ｄは下記数式１６のように整理できる。

In the same way as i _q , i _d can be arranged as in the following Expression 16.

電動機Ｍの回転子角速度（電気角）ω［ｒａｄ／ｓ］、ｄ軸インダクタンスＬｄ［Ｈ］、ｑ軸インダクタンスＬｑ［Ｈ］、巻線抵抗Ｒａ［Ω］が既知であるとすると、上記数式１６はＣ，Ｄを定数として下記数式１７のように整理できる。

Assuming that the rotor angular velocity (electrical angle) ω [rad / s], d-axis inductance Ld [H], q-axis inductance Lq [H], and winding resistance Ra [Ω] of the motor M are known, the above equation 16 Can be organized as shown in Equation 17 below using C and D as constants.

上記数式１５及び数式１７を電動機のトルク式（数式８）に代入すると、

一方、現在のトルクＴを電力Ｐと回転数ωから推定し、上記数式１８に代入すると下記数式１９のようになる。

Substituting Equation 15 and Equation 17 into the torque equation (Equation 8) of the motor,

On the other hand, when the current torque T is estimated from the electric power P and the rotational speed ω and substituted into the above equation 18, the following equation 19 is obtained.

この数式１９を磁束Φａで解くことにより、現在の推定トルクから磁石磁束の推定し、この磁石磁束の推定値と基準磁石磁束(基準温度時の磁石磁束)を用いることにより磁石温度を推定することができる。

Solving the mathematical formula 19 by the magnetic flux Φa, the magnet magnetic flux is estimated from the current estimated torque, and the magnet temperature is estimated by using the estimated value of the magnetic magnetic flux and the reference magnet magnetic flux (magnet magnetic flux at the reference temperature). Can do.

In this example, the electric power may be calculated from the following equation 20 using the dq-axis currents i _d and i _q and the dq-axis voltage command values ν ^* _d and ν ^* _q , or the three-phase currents iu and iv , Iw and the three-phase voltage command values ν ^* _u , ν ^* _v , ν ^* _w, may be calculated using the following Equation 21.

なお、本例では制御モードの切換判定に電流ベクトルを用いたが、トルク指令値、直流電圧および磁石温度から求めた回転数閾値を測定したモータ回転数が下回った場合に切り換えてもよい。

In this example, the current vector is used for switching determination of the control mode. However, the current vector may be switched when the rotational speed threshold obtained from the torque command value, the DC voltage, and the magnet temperature is lower.

Further, in order to suppress the step of the output torque at the time of switching the control mode, the correction torque is added to the torque command value. However, as shown in FIG. 12, the correction torque is made to gradually approach zero according to the rotation speed of the motor M. Also good. Further, as shown in FIG. 13, the correction torque may be a correction torque that gradually approaches zero according to time.

As described above, according to the drive control apparatus of the present embodiment, the torque correction calculation unit 10 shown in FIG. 1 equalizes the output torque in the voltage phase control mode and the PWM current control mode, resulting in a difference in output torque. Without switching, the voltage phase control mode and the PWM current control mode can be switched.

In addition, since the voltage phase control mode is switched to the PWM current control mode when the current vector in the voltage phase control mode reaches the threshold value, the switching can be performed only by the current value.

Moreover, since the voltage phase control mode is switched to the PWM current control mode using the rotation speed, torque command value, DC voltage, and estimated magnet temperature, the torque command value, DC voltage, and magnet temperature fluctuations are not affected. It is possible to switch at an appropriate timing.

Further, by making the torque value (corrected torque) for correcting the torque command value asymptotic to zero as a function of the rotation speed, it is possible to calculate the current command value as the torque command value.

Further, by making the torque value (corrected torque) for correcting the torque command value asymptotic to zero as a function of time, it is possible to calculate the current command value as the torque command value.

In addition, when the amplitude of the AC voltage applied to the electric motor reaches the threshold during the PWM current control mode, switching from the PWM current control mode to the voltage phase control mode does not cause voltage, current, and torque fluctuations. The PWM current control mode can be switched to the voltage phase control mode.

2 corresponds to the PWM current control means of the present invention, the configuration of FIG. 3 of this example corresponds to the voltage phase control means of the present invention, and the control switching unit 15 of this example corresponds to the present invention. The magnet temperature estimation unit 9 of this example corresponds to the magnet temperature estimation unit of the present invention, and the torque correction calculation unit 10 of this example corresponds to the correction unit of the present invention.

M ... Electric motor 1 ... DC power supply 2 ... Inverter 3 ... Dead time compensation unit 4 ... PWM conversion unit 5 ... dq-three phase conversion unit 6 ... Three phase-dq conversion unit 7 ... Power calculation unit 8 ... Differentiation circuit 9 ... Magnet temperature Estimating unit 10 ... torque correction computing unit 11, 12 ... control map 13 ... current control computing unit 14 ... voltage command value computing unit 15 ... control switching unit 16 ... adder

Claims (6)

PWM current control means for supplying a sine wave current having a predetermined amplitude and a predetermined phase according to the torque command value to the AC motor;
Voltage phase control means for supplying an alternating current having a phase out of the predetermined phase according to a torque command value to the alternating current motor;
Control switching means for switching between PWM current control by the PWM current control means and voltage phase control by the voltage phase control means;
Magnet temperature estimating means for estimating the temperature of the permanent magnet of the AC motor;
When switching from the voltage phase control to the PWM current control with a step in the voltage amplitude, the torque during the voltage phase control and the torque during the PWM current control are calculated from the temperature of the permanent magnet estimated by the magnet temperature estimation means. The torque command value for the PWM current control is calculated by adding a torque difference obtained by subtracting the torque for the PWM current control from the calculated torque for the voltage phase control to the torque command value for the PWM current control. And a correction means for correcting the motor drive control device. In the electric motor drive control device according to claim 1,
The PWM current control means takes in the phase current value and rotation angle of the AC motor at a predetermined phase of the PWM carrier signal, and compares the difference between the current command value calculated from the phase current value and the torque command value and the rotation angle. Based on the voltage command value, the voltage command value is output at the time of a predetermined phase in the next carrier cycle of the PWM carrier signal,
The voltage phase control means calculates a voltage command value from the voltage phase and voltage amplitude calculated from the torque command value, and outputs a voltage command value at a predetermined phase in the next carrier cycle of the PWM carrier signal. An electric motor drive control device. In the motor drive control device according to claim 1 or 2,
The drive control device for an electric motor, wherein the control switching means performs switching from the voltage phase control to the PWM current control when the current vector of the voltage phase control reaches a threshold value. In the drive control device of the electric motor according to any one of claims 1 to 3 ,
The motor drive control apparatus according to claim 1, wherein the correction means gradually makes the correction value of the torque command value approach zero as the rotational speed of the AC motor becomes smaller than the switching rotational speed . In the drive control device of the electric motor according to any one of claims 1 to 3 ,
The motor drive control apparatus according to claim 1, wherein the correction means gradually makes the correction value of the torque command value as close to zero as the time from the switching time elapses . In the drive control device for an electric motor according to any one of claims 1 to 5 ,
The control switching means performs switching from the PWM current control to the voltage phase control when the amplitude of the AC voltage applied to the AC motor reaches a threshold during the PWM current control. Electric motor drive control device.

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