JP4300375B2 - Motor control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control technique for a motor (such as a brushless motor) used in an air conditioner, and more particularly to a motor control method that removes harmonic components of an induced voltage waveform and reduces motor torque ripple. Is.
[0002]
[Prior art]
When the motor is controlled by an inverter, for example, the apparatus shown in FIG. 4 is required. An AC power source (commercial power source) 1 is converted into a direct current by an AC / DC conversion circuit 2, and this converted direct current power is switched by an inverter circuit 3. The three-phase alternating current is supplied to the motor 4. Switching of the inverter circuit 3 is performed by a PWM waveform described later, and the motor drive current is determined by this PWM waveform (in other words, the rotation speed is determined).
[0003]
When the AC / DC conversion circuit 2 is provided with a converter unit, the switching element of the converter unit is switched with a PWM waveform to determine the motor drive current, or the motor drive including the switching of the inverter circuit 3 is performed. There is also a way to determine the current. Further, the position of the rotor is detected by the position detection circuit 5, and this position detection signal is input to a control circuit (microcomputer) 6. The control circuit 6 drives the transistor of the inverter circuit 3 to drive the stator of the motor 4. Switch winding current (switch energization).
[0004]
As a position detection method, for example, there is a method of detecting a zero cross point from an induced voltage waveform induced in a non-energized phase and detecting a rotor position from the zero cross point. Therefore, the position detection circuit 5 synthesizes and divides the terminal voltages of the armature windings U, V, and W by the synthesis circuit 5a to obtain a virtual neutral point voltage of the motor, and this virtual neutral point voltage (that is, Induced voltage) and the reference voltage generated by the voltage generation circuit 5b are compared by the comparison circuit 5c, and the comparison result is output to the control circuit (microcomputer or the like) 6 as position detection.
[0005]
In the case of the PWM control method described above, the control circuit 6 switches the energization of the armature winding based on the position detection, and generates a PWM waveform for setting the motor drive current to a predetermined value in the PWM generator 6a. The drive signal of this generated PWM waveform is output to the inverter circuit 3 via an internal driver. When the AC / DC conversion circuit 2 includes a converter unit, the PWM waveform signal is also output to the AC / DC conversion circuit 2.
[0006]
Then, each of the transistors Ua, Va, Wa, X, Y, and Z of the inverter circuit 3 is turned on and off in a predetermined manner, and energization of the armature winding of the motor 4 is switched. Further, switching of the converter section of the AC / DC conversion circuit 2 is turned on and off in a predetermined manner, and the motor drive current becomes a predetermined value, that is, the motor rotation speed becomes a predetermined value.
[0007]
[Problems to be solved by the invention]
However, in the motor control method described above, no consideration is given to harmonic components contained in the induced voltage used for rotor position detection (see FIGS. 5A and 5B). This causes torque ripple. 5A and 5B show induced voltage waveforms and harmonics in the case where 24 slots are used as a stator in a three-phase four-pole motor.
[0008]
For example, when the reluctance torque is generated even in a motor in which a permanent magnet is embedded, the harmonic component includes a ripple (higher order harmonic) generated by the interaction between the stator slot and the reluctance torque. The high-order harmonics are superimposed on the induced voltage, (see FIG. 5 (a)) for the induced voltage containing the ripple is a pulsating component of the reluctance torque is generated, the position detection of the rotor is not appropriate, the motor 4 Is not optimally switched. This leads to the generation of torque ripple.
[0009]
The present invention has been made in view of the above problems, and an object of the present invention is to control a motor capable of removing ripples (harmonic components) superimposed on an induced voltage and reducing motor torque ripple. It is to provide a method.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention converts an AC power source into a DC voltage by an AC / DC conversion means, and converts the DC voltage into a predetermined voltage by a converter means included in the AC / DC conversion means. The switching means of the inverter means is PWM controlled and the switching element of the converter means is PWM controlled, while the induced voltage waveform generated in the non-energized phase of the motor is also supplied. In the motor control method of detecting the position of the rotor and switching the energization of the motor based on the position detection, the induced voltage waveform is captured and expanded into a Fourier series, and from the expanded Fourier series It said calculating a harmonic component except for the fundamental wave of the induced voltage waveform, and the correction value is shifted a half cycle phase of the harmonic component thus calculated , By adding the correction value thus calculated to the PWM control of the switching elements of said converter means to drive the switching element, is characterized in that so as to remove the harmonic component of the induced voltage waveform.
[0011]
Further, the present invention is to convert the DC voltage AC / DC converting means AC power, an inverter for driving the motor as a predetermined voltage by the converter means for the direct current voltage contained in the AC / DC converting means The switching means of the inverter means is PWM controlled and the switching element of the converter means is PWM controlled, while the rotor voltage is generated based on the induced voltage waveform generated in the non-energized phase of the motor. In a motor control method for detecting a position and switching energization of the motor based on the position detection , the induced voltage waveform is captured and expanded into a Fourier series, and the fundamental of the induced voltage waveform is derived from the expanded Fourier series. calculating a harmonic component except for the wave, the phase of the harmonic components and the correction value is shifted a half cycle of the calculated correction values the calculated Said by pressurized taste both the PWM control of the switching elements of the PWM control and the inverter unit of the switching elements of the converter means to drive the respective switching elements, and so as to remove the harmonic component of the induced voltage waveform It is a feature.
[0012]
The motor may be mounted on an air conditioner and used at least as a compressor motor of the air conditioner. By using a motor with reduced torque ripple, it is possible to improve the operating efficiency and power saving of the air conditioner.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an actual 施形 condition of the present invention with reference to FIGS. 1 to 3 will be described in detail. In FIG. 1, the same parts as those in FIG. 3 (a) and 3 (c) correspond to FIGS. 5 (a) and 5 (b).
[0014]
In FIG. 1, a control device to which this motor control method is applied includes a harmonic component calculation unit 10 a that expands an induced voltage waveform (virtual neutral voltage waveform) into a Fourier series and calculates a harmonic component, and an induction A phase correction unit 10b that shifts the phase of the calculated harmonic component by a predetermined value to remove a harmonic component of the voltage waveform to make a correction value, and a PWM generation unit 10c that generates a PWM waveform by taking this correction value into account The control circuit (microcomputer etc.) 10 which has is provided. The control circuit 10 also has the function of the control circuit 6 shown in FIG. 4, and the PWM generator 10c also has the function of the PWM generator 6a shown in FIG.
[0015]
More specifically, the harmonic component calculation unit 10a performs A / D conversion on at least the induced voltage waveform by an internal A / D converter and takes in one rotation (360 degrees) of the rotor, The harmonic data is calculated by expanding the stored data into a Fourier series. That is, the induced voltage is generated with the rotation of the rotor and has periodicity, so that it is expanded into a Fourier series.
[0016]
The phase correction unit 10b shifts the phase of the harmonic component by a half cycle, calculates data that cancels out the harmonic component of the induced voltage waveform, and sets it as a correction value. The PWM generator 10c adds the correction value obtained by the phase corrector 10b to the current PWM waveform and outputs (adds or subtracts it).
[0017]
The operation of the control device having the above configuration will be described with reference to the flowchart of FIG. 2 and the waveform diagram of FIG.
[0018]
First , it is assumed that the control circuit 10 controls the rotation of the motor 4. At this time, the harmonic component calculation unit 10a of the control circuit 10 stores the induced voltage waveform after A / D conversion and stores the A / D converted induced voltage waveform data for one rotation of the rotor. (Step ST1).
[0019]
Subsequently, the data for one rotation is expanded into a Fourier series of a sine function system or a cosine function system. In this Fourier series expansion, one period (period of the fundamental wave) T of the induced voltage waveform is used (see FIG. 3).
[0020]
From this Fourier series, the other part excluding the fundamental wave (see FIG. 3B) (that is, harmonics; see FIG. 3C) is calculated (step ST2). In this case, the calculated harmonic is mainly the 11th harmonic in the case of a three-phase quadrupole, 24-slot motor, but it also includes some other harmonics.
[0021]
Subsequently, the phase of the calculated harmonic component is shifted by a half period by the phase correction unit 10b (see FIG. 3D), and a correction value for removing the harmonic component of the induced voltage waveform is calculated (step ST3). .
The calculated correction value is added to the PWM waveform by the PWM generator 10c. That is, the PWM waveform for driving the motor 4 is corrected (step ST4), and the corrected PWM waveform pattern output process is performed (step ST5).
[0022]
By this PWM waveform pattern output processing, PWM signals for switching the transistors Ua, Va, Wa, X, Y, and Z of the inverter circuit 3 are output. According to the present invention, the AC / DC conversion circuit 2 is supplied with the PWM signal. The correction value is added to the PWM signal for switching the switching element of the included converter unit. As a result, the output DC voltage of the AC / DC conversion circuit 2 changes by the correction value, and this acts to remove the harmonic component contained in the induced voltage.
[0023]
Further, in the pattern output process, PWM for switching the switching elements of the converter unit included in the AC / DC conversion circuit 2 and switching the transistors Ua, Va, Wa, X, Y, and Z of the inverter circuit 3. A correction value may be added to both signals. According to is this, induced harmonic components included in the generated voltage waveform is appropriately removed, it attained sufficient reduction of torque ripple.
[0024]
By the way, when the motor 4 is controlled at a variable speed, that is, when the rotational speed of the motor 4 changes, the routine shown in FIG. 2 is executed for each rotational speed to calculate a correction value for correcting the current PWM waveform, This correction value is added to the PWM waveform to obtain an output pattern. Thereby, even if the rotation speed of the motor 4 changes, the harmonic component contained in the induced voltage waveform is removed, and the torque ripple of the motor 4 is also reduced.
[0025]
Moreover, if the control method is applied to a compressor motor of an air conditioner, etc., the torque ripple is reduced, which contributes to the improvement of the operation efficiency and power saving of the air conditioner.
[0026]
【The invention's effect】
According to the present invention described above, to extract a harmonic component contained in the induced electromotive voltage waveform, obtain a correction value for canceling harmonic components by shifting the phase of the harmonic components, the motor of this correction value Therefore, the harmonic component of the induced voltage waveform is removed. Therefore, since the torque ripple of the motor can be reduced by cutting this harmonic component (ripple), it is possible to improve the motor efficiency and power saving.
[0027]
Further, the induced voltage waveform using the motor position detection circuit is expanded into a Fourier series, and a harmonic component is extracted from the Fourier series. This processing is performed by a microcomputer which is a control means of the motor. As a result, there is no need to add a new hardware circuit, and the cost is not increased.
[Brief description of the drawings]
[1] relates to the implementation type state of the present invention, a schematic block diagram showing a control apparatus for a motor control method is applied.
2 is a schematic flow chart diagram for explaining the operation of the control apparatus shown in FIG.
3 is a schematic waveform diagram for explaining the operation of the control apparatus shown in FIG.
Figure 4 is a schematic block diagram showing a conventional motor control system.
Figure 5 is a schematic waveform diagram for explaining the problem of the control device shown in FIG.
[Explanation of symbols]
1 AC power supply 2 AC / DC conversion circuit (including converter)
3 Inverter circuit 4 Motor 5 Position detection circuit 6, 10 Control circuit (microcomputer)
6a, 10c PWM generator 10a Harmonic component calculator 10b Phase corrector

Claims (3)

AC power is converted into DC voltage by AC / DC conversion means, and the DC voltage is supplied to inverter means for driving a motor as a predetermined voltage by converter means included in the AC / DC conversion means, PWM control of the switching element of the inverter means and PWM control of the switching element of the converter means, while detecting the position of the rotor based on the induced voltage waveform generated in the non-energized phase of the motor, In a motor control method for switching energization of the motor based on position detection ,
Takes the induced voltage waveform and expands it into a Fourier series, calculates a harmonic component obtained by removing the fundamental wave of the induced voltage waveform from the expanded Fourier series, and corrects the phase of the calculated harmonic component by shifting it by a half cycle the value, the switching element is driven by adding the correction value thus calculated to the PWM control of the switching elements of said converter means, the motor being characterized in that so as to remove the harmonic component of the induced voltage waveform Control method. AC power is converted into DC voltage by AC / DC conversion means, and the DC voltage is supplied to inverter means for driving a motor as a predetermined voltage by converter means included in the AC / DC conversion means, PWM control of the switching element of the inverter means and PWM control of the switching element of the converter means, while detecting the position of the rotor based on the induced voltage waveform generated in the non-energized phase of the motor, In a motor control method for switching energization of the motor based on position detection,
Takes the induced voltage waveform and expands it into a Fourier series, calculates a harmonic component obtained by removing the fundamental wave of the induced voltage waveform from the expanded Fourier series, and corrects the phase of the calculated harmonic component by shifting it by a half cycle a value, drives the respective switching elements by pressurized taste both PWM control of the switching elements of the PWM control and pre Symbol inverter means of the switching elements of said converter means a correction value the calculated, harmonic of the induced voltage waveform A method of controlling a motor, characterized in that wave components are removed .   The motor control method according to claim 1 or 2, wherein the motor is mounted on an air conditioner and used at least as a compressor motor of the air conditioner.

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