JP2009273302A - Controller for electric motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controller for an electric motor that controls a motor so as not to generate pulsation in motor speed and motor torque with respect to an error of a current detector and deteriorate the efficiency of the motor. <P>SOLUTION: The controller for an electric motor includes a DQ-axis current command value calculating section 13, a D-axis current command value calculating section 14, and a Q-axis current command value calculating section 15, which control the rotational speed of a three-phase AC synchronous motor 201 by control calculation for the D-axis and the Q-axis; and a high-pass filter 18 which never pass specified frequency components of three-phase currents Iu, Iv, and Iw output from a three-phase current detecting section 17 to a current converting section 19. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention belongs to the technical field of electric motor control devices.

Conventionally, when there is an offset that is an error of the current detector under the condition that the motor current at light load is small, this causes torque pulsation and rotation ripple, so it is set to the normal D-axis current command value. By adding the corrected D-axis current, the motor current is corrected to the lower limit value or more, and is less susceptible to the offset of the current detector (see, for example, Patent Document 1).
Japanese Patent No. 3796556 (page 2-6, all figures)

  However, in the past, the efficiency was deteriorated by passing more current than usual.

  The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to prevent the motor from generating motor speed and torque pulsation due to the error of the current detector and to prevent the efficiency from deteriorating. An object of the present invention is to provide a control device for an electric motor that can be controlled.

  In order to achieve the above object, in the present invention, in an electric motor control apparatus for controlling a three-phase AC synchronous motor, three-phase current detection means for detecting a three-phase current flowing in the three-phase AC synchronous motor; Current conversion means for converting current into D-axis current and Q-axis current for the D-axis and Q-axis set for the three-phase AC synchronous motor, and control for the D-axis and the Q-axis Control means for controlling the rotational speed of the three-phase AC synchronous motor by calculation, and filter means for preventing a specific frequency component of the three-phase current from the three-phase current detection means to the current conversion means. And

  Therefore, in the present invention, the motor can be controlled so that the motor speed and torque pulsation are not generated and the efficiency is not deteriorated with respect to the error of the current detector.

  Embodiments for realizing the control device for an electric motor according to the present invention will now be described with reference to the first embodiment corresponding to the first, second, and fourth aspects of the invention, and the implementation corresponding to the first, third, and fourth aspects. This will be described based on Example 2.

First, the configuration will be described.
FIG. 1 is a diagram illustrating a block configuration of an electric motor control apparatus according to the first embodiment.
Examples of the electric motor control device according to the first embodiment include an electric compressor control device in a vehicle air conditioner and an EV or HEV drive motor control device.
The electric motor control device 1 according to the first embodiment is provided as a part of a controller of a three-phase synchronous electric motor. Therefore, the target speed of the three-phase synchronous electric motor is set by the other part of the controller and is input to the electric motor control device 1. And the electric motor control apparatus 1 outputs a control signal to the motor inverter 2 which consists of an inverter and a three-phase synchronous electric motor.

  The electric motor control device 1 includes a target rotation speed calculation unit 11, an adder 12, a DQ axis current command value calculation unit 13, a D axis voltage command value calculation unit 14, a Q axis voltage command value calculation unit 15, and an inverter control signal calculation unit. 16, a three-phase current detection unit 17, a high-pass filter 18, a current conversion unit 19, a rotation angle calculation unit 20, and a rotation speed estimation unit 21.

The target rotation speed calculation unit 11 calculates a target rotation speed as a control target. For example, in the case of a vehicle air conditioner, the target air speed is set by PI control by comparing the actual air temperature with the target air temperature so that the air temperature after passing through the evaporator becomes a desired value.
The adder 12 calculates a deviation between the target rotational speed of the three-phase synchronous electric motor and the actual value of the detected rotational speed.

The DQ-axis current command value calculation unit 13 performs a feedback calculation that multiplies the speed deviation by a gain, for example, a PI control calculation, and calculates a DQ-axis current command value Ia.
Further, the current is distributed from the DQ axis current command value Ia to the D axis current command value Id ^* and the Q axis current command value Iq ^* and output. This distribution is performed by the following formula, for example. Here, β corresponds to the advance angle, and is a value determined from a motor device constant.

  (Equation 1)

Id ^* = sin (β / 180 ・ π) ・ Ia

  (Equation 2)

Iq ^* = cos (β / 180 ・ π) ・ Ia

The D-axis voltage command value calculation unit 14 compares the D-axis current command value Id ^* with the detected D-axis current value Id, and calculates the D-axis voltage command value Vd ^* from PI control, for example.
The Q-axis voltage command value calculation unit 15 compares the Q-axis current command value Iq ^* with the detected Q-axis current value Iq, and calculates the Q-axis voltage command value Vq ^* from PI control, for example.
The inverter control signal calculation unit 16 performs the following calculation to calculate the three-phase command voltages (Vu ^* , Vv ^* , Vw ^* ). Vα ^* and Vβ ^* are intermediate variables and two-phase voltage command values. Further, θ is a rotation angle represented by an electrical angle (mechanical angle × number of pole pairs).

さらにインバータ制御信号演算部１６は、３相指令電圧（Vu^＊,Vv^＊,Vw^＊)と３角波を比較して、スイッチング信号を生成し、出力する。

Further, the inverter control signal calculation unit 16 compares the three-phase command voltages (Vu ^* , Vv ^* , Vw ^* ) with the triangular wave to generate and output a switching signal.

  The three-phase current detector 17 detects currents (Iu, Iv, Iw) that flow through the U-phase, V-phase, and W-phase coils of the three-phase synchronous electric motor. Since the sum of all currents is 0 amperes, two of the three phases may be sensed using the relationship, and the rest may be calculated. In that case, it shall be according to the following formula.

  (Equation 5)

  Iu =-(Iv + Iw)

  The high-pass filter 18 performs processing that passes the high-frequency component of the detection current of each phase and does not pass the low-frequency component, and outputs the detection current from the three-phase current detection unit 17 to the current conversion unit 19.

  The current conversion unit 19 obtains Id for the Q-axis current Iq and the D-axis current from the detected three-phase currents Iu, Iv, and Iw using the following equations. The current values Iq and Id are actual values because they are converted detection currents.

なお、この２つの式は、パーク変換とクラーク変換である。

These two equations are Park conversion and Clark conversion.

The rotation angle calculation unit 20 integrates the rotation speed estimated by the rotation speed estimation unit 21 and calculates the rotation angle.
The rotation speed estimation unit 21 estimates the rotation speed by an estimation calculation.
As an example of estimation calculation, the paper “The periodic speed fluctuation suppression control using BPF for PMSM position sensorless vector control for compressors” described in IEEJ Transaction (Industrial Application Division) Vol. 127, No. 7 The estimation calculation described in 1 is given.

FIG. 2 is a schematic explanatory diagram of the motor inverter 2.
The motor inverter 2 includes a three-phase AC synchronous motor 201, a power source 202 that is an inverter circuit, transistors 203 to 208, and current detection resistors 209 and 210.
The rotor structure of the three-phase AC synchronous motor 201 is assumed to be an embedded magnet type.
The power source 202 supplies driving power to the three-phase AC synchronous motor 201.
The transistors 203 to 208 each output to the three-phase (U-phase, V-phase, W-phase) coils of the three-phase AC synchronous motor 201. On the three-phase upper arm side, the emitters of the transistors 203 to 205 are connected to the respective three-phase coils, and the collector is connected to the power supply side. The input to the base is connected to the gate control signal from the inverter control signal calculation unit 16.

Next, on the three-phase lower arm side, the collectors of the transistors 206 to 208 are connected to each of the three-phase coils, and the emitter is connected to the feedback side to the power source. The input to the base is connected to the gate control signal from the inverter control signal calculation unit 16. The lower arm side receives an inverted waveform of the gate control signal on each upper arm side.
Further, among the three phases, current detection resistors 209 and 210 are provided on the two-phase lower arm side. The current values of the remaining phases are obtained by calculation (see the above formula 10). A shunt resistor is given as an example of the current detection resistors 209 and 210.

The operation will be described.
[Motor control]
In the electric motor control device 1 according to the first embodiment, information is input to the target rotation speed calculation unit 11 by the control provided at the upper level, and control is performed based on the information.
For example, in the air conditioning control in the passenger compartment, the target rotational speed of the electric compressor is set.
On the other hand, in the control device for the electric motor, the AC synchronous motor is controlled by the vector control method so as to realize the target rotation speed.
FIG. 3 is an explanatory diagram of vector control of the control apparatus for the electric motor according to the first embodiment.
In this vector control, as shown in FIG. 3, the alternating current is converted into direct current, and the D axis in the magnetic pole direction and the Q axis perpendicular to the magnetic pole are considered for the rotor of a pair of magnetic poles. Treat as Q-axis current.
Therefore, increasing the D-axis current increases the torque, and increasing the Q-axis current increases the rotational speed.

In the first embodiment, the DQ axis current command value calculation unit 13 calculates the DQ axis current command value from the deviation between the target rotation speed and the actual rotation speed, and further, the D axis current command value Id ^* and the Q axis current command value. Calculates and distributes to Iq ^* .
Then, the D-axis voltage command value calculation unit 14 and the Q-axis voltage command value calculation unit 15 perform feedback control so that the detected values Id and Iq are close to the D-axis current command value Id ^* and the Q-axis current command value Iq ^*. Perform by control.
Then, the D-axis voltage command value Vd ^* and the Q-axis voltage command value Vq ^* obtained in this way are output, and the inverter control signal calculation unit 16 outputs the three-phase command voltages (Vu ^* , Vv ^* , Vw ^*). Then, the control to output to the motor inverter 2 is performed.

FIG. 4 is an explanatory diagram showing a state in which a gate control signal is generated from a U-phase voltage command value and a triangular wave.
In the control apparatus for the electric motor of the first embodiment, the inverter control signal calculation unit 16 compares the three-phase command voltages (Vu ^* , Vv ^* , Vw ^* ) with the three-waves (see FIG. 4 (a)). A gate control signal is generated (see FIG. 4B). This gate control signal is a PWM control signal and is expressed by a duty ratio.
Although FIG. 4 shows the U phase as an example, the V phase and the W phase can be generated similarly.

[Offset suppression of detection error]
FIG. 5 is a waveform diagram of the three-phase detection current, the Q-axis current Iq, the D-axis current Id, the motor speed, and the motor torque when an offset detection error occurs.
FIG. 6 is a waveform diagram of a three-phase detection current, a Q-axis current Iq, a D-axis current Id, a motor speed, and a motor torque in a control state by the electric motor control device of the first embodiment.
When detecting a three-phase current, if there is a detection error such as an offset (see FIG. 5 (a), if current conversion is performed using that current, the currents Id and Iq that should be direct current are AC components. Are superimposed (see FIG. 5B).
When current control or the like is performed using the currents Id and Iq on which the AC components are superimposed, the motor speed and motor torque will pulsate (see FIGS. 5C and 5D). ) As a result, it causes vibration and noise.

In the electric motor control apparatus 1 according to the first embodiment, after detecting the three-phase current (see FIG. 6A), the high-pass filter 18 is passed to eliminate the detection error offset which is a low-frequency component (see FIG. 6). 6 (b)).
Then, the currents Id and Iq after current conversion are only DC components, and the motor is controlled without generating motor speed and torque pulsation that cause vibration and noise (see FIGS. 6C and 6D). be able to.
Moreover, in the control apparatus for the electric motor according to the first embodiment, no current is added, and the efficiency is maintained satisfactorily.

Explain the effect. The control device for the electric motor according to the first embodiment has the effects listed below.
(1) In the electric motor control device 1 that controls the three-phase AC synchronous motor 201, the three-phase current detection unit 17 that detects the three-phase currents Iu, Iv, and Iw flowing through the three-phase AC synchronous motor 201, and the three-phase current A current converter 19 that converts Iu, Iv, and Iw into a D-axis current Id and a Q-axis current Iq for the D-axis and the Q-axis set for the three-phase AC synchronous motor 201; A DQ-axis current command value calculation unit 13, a D-axis current command value calculation unit 14, a Q-axis current command value calculation unit 15 that control the rotation speed of the three-phase AC synchronous motor 201 by a control calculation for the shaft, Since the high-pass filter 18 that does not pass the specific frequency components of the three-phase currents Iu, Iv, and Iw from the current detection unit 17 to the current conversion unit 19 is provided, an error component of the detected three-phase current is removed by a filter, and a current detector The motor speed and torque pulsation are not generated for the error of The motor can be controlled so as not to deteriorate the efficiency.

  (2) In the above (1), the filter means is a high-pass filter 18 that passes high-frequency components and does not pass low-frequency components. Therefore, the detected three-phase current offset is removed, and the error of the current detector is reduced. Thus, the motor can be controlled so that the motor speed and torque pulsation are not generated and the efficiency is not deteriorated.

  (4) In the above (1) and (2), when the three-phase AC synchronous motor 201 is used to drive a compressor in a vehicle air conditioner, it generates motor speed pulsation and torque pulsation. Therefore, it is possible to provide more comfortable air conditioning with excellent controllability and maintain good efficiency, thereby contributing to power saving and fuel efficiency improvement.

The electric motor control apparatus according to the second embodiment is an example using a bandpass filter that changes the passband according to the motor speed.
The configuration will be described.
FIG. 7 is a diagram illustrating a block configuration of the electric motor control apparatus according to the second embodiment.
The band pass filter 22 varies the frequency pass band according to the motor rotation speed obtained from the rotation speed estimation unit 21 and attenuates frequency components other than the motor speed.
Since other configurations are the same as those of the first embodiment, description thereof is omitted.

The operation will be described.
[Offset suppression of detection error]
FIG. 8 is a waveform diagram of three-phase detection current, Q-axis current Iq, D-axis current Id, motor speed, and motor torque when high-frequency noise is superimposed.
FIG. 9 is a waveform diagram of the three-phase detection current, the Q-axis current Iq, the D-axis current Id, the motor speed, and the motor torque in the control state by the electric motor control device of the second embodiment.
When detecting a three-phase current when operating at a motor speed of 3000 rpm (= 50 Hz), if there is a detection error such as an offset, and noise of a frequency component of 1 (kHz) is superimposed, the high-pass filter 18 is turned on. Even if it is used, since the noise is relatively high frequency, the noise component is not sufficiently removed (see FIGS. 8A and 8B). Then, the three-phase alternating current does not have an ideal waveform, and as a result, pulsation occurs in the motor speed and torque (see FIGS. 8C and 8D).

FIG. 10 is a diagram illustrating frequency characteristics of the bandpass filter 22 according to the second embodiment.
In the second embodiment, as shown in FIG. 10, the bandpass filter 22 has a characteristic line 101 when the motor speed is 1000 rpm (105 rad / s), and has a characteristic that attenuates other than the motor speed frequency. As a result, the three-phase alternating current after passing through the band-pass filter 22 has an ideal waveform (see FIGS. 9A and 9B), and the motor speed and torque follow the target well and can be controlled stably. (See FIGS. 9 (c) and 9 (d)).

  Further, for the motor speed, for example, when the motor speed is 2000 rpm, the characteristic line 102 in FIG. 10 is obtained, and when the motor speed is 3000 rpm, the characteristic line 103 in FIG. 10 is obtained. As described above, the frequency characteristic of the bandpass filter 22 becomes variable according to the motor rotation speed, and noise superposition is extremely suppressed. For this reason, both the relatively high frequency noise and the influence of the offset are suppressed. Moreover, it is not necessary to increase the current, and efficient operation is maintained.

Explain the effect. The electric motor control apparatus according to the second embodiment has the following effects in addition to the above (1) and (4).
(3) In addition to the above (1), the filter means is a bandpass filter that changes the pass band in accordance with the motor speed, so in addition to removing the detected three-phase current offset, the motor rotation frequency In order to remove noise other than the above, for example, relatively high-frequency noise, the motor can be controlled such that the motor speed and torque pulsation are not generated and the efficiency is not deteriorated.

  As mentioned above, although the control apparatus of the electric motor of this invention has been demonstrated based on Example 1, it is not restricted to these Examples about a concrete structure, The invention which concerns on each claim of a claim Design changes and additions are permitted without departing from the gist of the present invention.

For example, the three-phase AC synchronous motor may be used for driving a hybrid vehicle (HEV) or may be used for driving an electric vehicle (EV). Suppression of torque vibration leads to a reduction in operating noise, and securing a wide driving range leads to miniaturization of the motor.
In the embodiment, the inverter is composed of a transistor, but another switching element may be used.

It is a figure which shows the block configuration of the control apparatus of the electric motor of Example 1. FIG. 2 is a schematic explanatory diagram of a motor inverter 2. FIG. It is explanatory drawing of the vector control of the control apparatus of the electric motor of Example 1. FIG. It is explanatory drawing which shows the state which produces | generates a gate control signal from the voltage command value and triangular wave of U phase. FIG. 6 is a waveform diagram of a three-phase detection current, a Q-axis current Iq, a D-axis current Id, a motor speed, and a motor torque in a state where an offset detection error occurs. FIG. 3 is a waveform diagram of a three-phase detection current, a Q-axis current Iq, a D-axis current Id, a motor speed, and a motor torque that are controlled by the electric motor control device according to the first embodiment. It is a figure which shows the block configuration of the control apparatus of the electric motor of Example 2. FIG. FIG. 6 is a waveform diagram of a three-phase detection current, a Q-axis current Iq, a D-axis current Id, a motor speed, and a motor torque when high-frequency noise is superimposed. FIG. 6 is a waveform diagram of a three-phase detection current, a Q-axis current Iq, a D-axis current Id, a motor speed, and a motor torque that are controlled by the electric motor control device according to the second embodiment. It is a figure which shows the frequency characteristic of the band pass filter of Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor control apparatus 11 Target rotational speed calculating part 12 Adder 13 DQ-axis current command value calculating part 14 D-axis voltage command value calculating part 15 Q-axis voltage command value calculating part 16 Inverter control signal calculating part 17 Three-phase current detection part DESCRIPTION OF SYMBOLS 18 High pass filter 19 Current conversion part 20 Rotation angle calculating part 21 Rotational speed estimation part 22 Band pass filter 2 Motor inverter 201 Three-phase alternating current synchronous motor 202 Power supply 203-208 Transistor 209 Current detection resistance 210 Current detection resistance
Ia DQ axis current command value
Id ^* D-axis current command value
Id Real D-axis current
Iq ^* Q-axis current command value
Iq Actual Q axis current
Iu U phase current
Iv V phase current
Iw W phase current
Vd D-axis voltage command value
Vq Q-axis voltage command value 101 Characteristic line 102 (of the frequency characteristic of the bandpass filter) Characteristic line 103 (of the frequency characteristic of the bandpass filter) Characteristic line (of the frequency characteristic of the bandpass filter)

Claims (4)

In the control device for the electric motor that controls the three-phase AC synchronous motor,
Three-phase current detection means for detecting a three-phase current flowing in the three-phase AC synchronous motor;
Current converting means for converting the three-phase current into a D-axis current and a Q-axis current for the D-axis and the Q-axis set for the three-phase AC synchronous motor;
Control means for controlling the rotational speed of the three-phase AC synchronous motor by a control calculation for the D axis and the Q axis;
Filter means that does not pass a specific frequency component of the three-phase current from the three-phase current detection means to the current conversion means;
An electric motor control device comprising: In the control apparatus of the electric motor according to claim 1,
The filter means is a high-pass filter that passes high-frequency components and does not pass low-frequency components.
A control apparatus for an electric motor. In the control apparatus of the electric motor according to claim 1,
The filter means is a bandpass filter that changes the passband according to the motor speed.
A control apparatus for an electric motor. In the control apparatus of the electric motor of any one of Claims 1-3,
The three-phase AC synchronous motor is used to drive a compressor in a vehicle air conditioner.
A control apparatus for an electric motor.

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