JP2000287481A - Motor control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate harmonic components in the waveform of an induced voltage and reduce torque ripples in a motor control method. SOLUTION: AC power from an AC power supply 1 is converted into DC power by an AC/DC conversion circuit 2 and supplied to an inverter circuit 3 which drives a motor 4. On the other hand, a plurality of transistors of the inverter circuit 3 are PWM-controlled and the current application to the motor 4 is changed from the position of a rotor which is detected in accordance with an induced voltage generated in the non-current-application phase of the motor 4. A control circuit 10 practices PWM control of the inverter circuit 3 and changes the current application to the motor 4. The induced voltage is fetched by a harmonic component calculation unit 10a and developed into a Fourier series, and harmonic components contained in the induced voltage are calculated from the Fourier series. In order to eliminate harmonic components contained in the induced voltage, the phases of the calculated harmonic components are shifted by half periods to calculate corrected values in a phase correction unit 10b, and the calculated corrected values are taken into account for the present PWM control to drive the respective transistors of the inverter circuit 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control technique for a motor (for example, a brushless motor) used in an air conditioner or the like, and more particularly to a technique for removing a harmonic component of an induced voltage waveform to reduce a torque ripple of the motor. The present invention relates to a method for controlling a motor to be reduced.

[0002]

2. Description of the Related Art In order to control a motor by an inverter, for example, an apparatus shown in FIG. 4 is required. An AC power supply (commercial power supply) 1 is converted into a direct current by an AC / DC conversion circuit 2, and this converted DC power supply is converted into an inverter circuit. The switching is performed at 3 and supplied to the motor 4 as a three-phase alternating current. The switching of the inverter circuit 3 is performed by a PWM waveform described later, and the motor drive current is determined by the PWM waveform (in other words, the rotation speed is determined).

When the AC / DC conversion circuit 2 is provided with a converter, the switching elements of the converter are switched with a PWM waveform to determine the motor drive current, or the switching of the inverter circuit 3 is performed. There is also a method of determining the motor drive current by using the following method. The position of the rotor is detected by a position detection circuit 5, and a signal of the position detection is input to a control circuit (microcomputer) 6. Switch the winding current (switch the energization).

As a method of detecting the position, 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 the position of the rotor based on the zero-cross point. Therefore, the position detection circuit 5 combines the terminal voltages of the armature windings U, V, and W with the combining circuit 5a and divides the terminal voltages to obtain a virtual neutral point voltage of the motor. The induced voltage) is compared with a reference voltage generated by a voltage generation circuit 5b by a comparison circuit 5c, and the comparison result is output to a control circuit (microcomputer or the like) 6 as position detection.

In the above-described PWM control method, the control circuit 6 switches the energization of the armature winding based on the position detection, while controlling the PWM for setting the motor drive current to a predetermined value.
A waveform is generated by a PWM generator 6a, and a drive signal of the generated PWM waveform is supplied to an inverter circuit 3 via an internal driver.
Output to If the AC / DC conversion circuit 2 includes a converter, the PWM waveform signal is
Also output to the / DC conversion circuit 2.

Then, the respective transistors Ua, Va, Wa, X, Y and Z of the inverter circuit 3 are turned on and off in a predetermined manner, and the energization of the armature winding of the motor 4 is switched. In addition, the switching of the AC / DC conversion circuit 2 converter section is turned on and off at predetermined times, and the motor drive current has a predetermined value, that is, the motor rotation speed has a predetermined value.

[0007]

However, in the above-described motor control method, no consideration is given to harmonic components contained in the induced voltage used for detecting the position of the rotor (see FIGS. 5A and 5B). b)), torque ripples occur due to the harmonic components. FIG.
(A) and (b) show a three-phase four-pole motor with a 24
7 shows an induced voltage waveform and a harmonic when a slot is used.

For example, as the above harmonic component, when reluctance torque is generated even in a motor in which a permanent magnet is embedded, ripples (higher harmonics) generated by the interaction between the slots of the stator and the reluctance torque are included. .
This higher-order harmonic is superimposed on the induced voltage, and an induced voltage including a ripple, which is a pulsating component of the reluctance torque, is generated (see FIG. 6A). Is not optimally switched. This leads to the occurrence of torque ripple.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to remove a ripple (harmonic component) superimposed on an induced voltage and reduce a torque ripple of a motor. An object of the present invention is to provide a motor control method.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an AC / DC converter for converting AC power into DC and supplying the DC power to an inverter for driving a motor. While the PWM control of the switching element is performed, the position of the rotor is detected based on the induced voltage waveform generated in the non-energized phase of the motor, and the motor for switching the energization of the motor based on the position detection is controlled. In the control method, the induced voltage waveform is captured and developed into a Fourier series, a harmonic component of the induced voltage waveform is calculated from the developed Fourier series, and a phase of the calculated harmonic component is shifted by a predetermined value to obtain a correction value. And the correction value is the PWM
In addition to the control, a switching element of the inverter means is driven to remove a harmonic component of the induced voltage waveform.

According to the present invention, an AC power supply is converted to a DC voltage by AC / DC conversion means, and the DC voltage is converted to the AC / D power.
A converter means included in the C conversion means supplies the voltage as a predetermined voltage to an inverter means for driving a motor, performs PWM control on a switching element of the inverter means, and performs PWM control on a switching element of the converter means. A motor control method for detecting a position of a rotor based on an induced voltage waveform generated in a non-energized phase of the motor, and switching energization of the motor based on the position detection; Take the voltage waveform and develop it into a Fourier series, calculate the harmonic component of the developed Fourier series excluding the fundamental wave of the induced voltage waveform,
The phase of the calculated harmonic component is shifted by a predetermined value to be a correction value, and the calculated correction value is added to the PWM control of the switching element of the converter means to drive the switching element, and the harmonic of the induced voltage waveform is generated. It is characterized in that components are removed.

It is preferable that the switching element is driven in consideration of the correction value in the PWM control of the switching element of the inverter means. As a result, harmonic components included in the induced voltage waveform are appropriately removed, and torque ripple can be sufficiently reduced.

Preferably, the motor is mounted on an air conditioner and used at least for a compressor motor of the air conditioner. By using a motor with reduced torque ripple, the operation efficiency of the air conditioner can be improved, and the power saving can be improved.

[0014]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to FIG. In FIG. 1,
The same parts as those in FIG. FIGS. 3A and 3C correspond to FIGS. 5A and 5B.

In FIG. 1, a control device to which the control method of the motor is applied includes a harmonic component calculating section 10a which expands an induced voltage waveform (virtual neutral point voltage waveform) into a Fourier series to calculate a harmonic component. A phase correction unit 10b that shifts the phase of the calculated harmonic component by a predetermined value to remove the harmonic component of the induced voltage waveform and corrects the phase, and a PWM generator that generates a PWM waveform in consideration of the correction value And a control circuit (microcomputer or the like) 10 having a unit 10c. 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.

More specifically, the harmonic component calculation unit 1
0a, at least an induced voltage waveform is A / D converted by an internal A / D converter to take in one rotation (360 degrees) of the rotor, and this is stored in an internal memory; Develop into Fourier series to calculate harmonic components.
In other words, the induced voltage is generated with the rotation of the rotor and has periodicity, so that it is developed into a Fourier series.

The phase corrector 10b shifts the phase of the harmonic component by a half cycle, calculates data for canceling the harmonic component of the induced voltage waveform, and sets it as a correction value. The PWM generation unit 10c
The correction value obtained by the phase correction unit 10b is added to the current PWM waveform and output (added or subtracted).

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.

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 A / D converts and stores the induced voltage waveform, and stores the A / D converted data of the induced voltage waveform for one rotation of the rotor. (Step ST1).

Subsequently, the data for one rotation is developed into a Fourier series of a sine function system or a cosine function system. In this Fourier series expansion, one cycle (cycle of the fundamental wave) T of the induced voltage waveform is used (see FIG. 3).

From this Fourier series, a fundamental wave (FIG. 3 (b)
The other parts (that is, harmonics; see FIG. 3C) except for the reference part are calculated (step ST2). In this case, the calculated harmonic is mainly the eleventh harmonic in the case of a three-phase quadrupole, 24-slot motor, but includes some harmonics of other orders.

Subsequently, the phase of the calculated harmonic component is shifted by a half cycle in the phase correction unit 10b (see FIG. 3D).
A correction value for removing a harmonic component of the induced voltage waveform is calculated (step ST3). The calculated correction value is referred to as PW
The M generator 10c takes into account the PWM waveform. That is,
The PWM waveform for driving the motor 4 is corrected (step ST4), and a pattern output process of the corrected PWM waveform is performed (step ST5).

By performing the PWM waveform pattern output process, the transistors Ua, Va, W of the inverter circuit 3 are output.
A PWM signal for switching a, X, Y, and Z is output. A correction value is added to the PWM signal, which acts to remove a harmonic component included in the induced voltage.

Further, a correction value may be added to the PWM signal for switching the switching element of the converter section included in the AC / DC conversion circuit 2. This allows
The output DC voltage of the AC / DC conversion circuit 2 changes by the correction value, which acts to remove harmonic components included in the induced voltage as described above.

Further, in the pattern output processing,
The switching element of the converter section included in the AC / DC conversion circuit 2 is switched, and the inverter circuit 3
The correction value may be added to both of the PWM signals for switching the transistors Ua, Va, Wa, X, Y, and Z. In this case, since the two functions described above work simultaneously, harmonic components included in the induced voltage waveform are appropriately removed. Thus, by removing the harmonic components, the torque ripple of the motor 4 is also reduced.

When the motor 4 is controlled at a variable speed, that is, when the rotation speed of the motor 4 changes, the routine shown in FIG. 2 is executed for each rotation speed, and a correction value for correcting the current PWM waveform is determined. Calculate and add this correction value to the PWM waveform to obtain an output pattern. Thereby, the motor 4
Even if the rotation speed of the motor 4 changes, harmonic components included in the induced voltage waveform are removed, and the torque ripple of the motor 4 is also reduced.

Further, if the above control method is applied to a compressor motor or the like of an air conditioner, reduction of torque ripple contributes to improvement of operation efficiency of the air conditioner and improvement of power saving.

[0028]

According to the present invention described above, the following effects can be obtained. The present invention extracts a harmonic component included in an induced voltage waveform, obtains a correction value for offsetting the harmonic component by shifting the phase of the harmonic component, and adds the correction value to the PWM control of the motor. As a result, harmonic components of the induced voltage waveform are removed.
Therefore, since the torque ripple of the motor can be reduced by cutting the harmonic components (ripple), there is an effect that the efficiency of the motor can be improved and the power saving can be improved.

Further, the induced voltage waveform utilizing the position detection circuit of the motor is developed into a Fourier series, and a harmonic component is extracted from the Fourier series. Since the operation is performed by the computer, there is no need to add a new hardware circuit, and the cost is not increased.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a control device according to a first embodiment of the present invention, to which a motor control method is applied;

FIG. 2 is a schematic flowchart for explaining the operation of the control device shown in FIG. 1;

FIG. 3 is a schematic waveform diagram for explaining the operation of the control device shown in FIG. 1;

FIG. 4 is a schematic block diagram of a conventional motor control device.

FIG. 5 is a schematic waveform diagram for explaining a problem of the control device shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 AC / DC conversion circuit (including converter part) 3 Inverter circuit 4 Motor 5 Position detection circuit 6,10 Control circuit (microcomputer) 6a, 10c PWM generation part 10a Harmonic component calculation part 10b Phase correction part

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3L060 AA03 CC12 CC18 CC19 DD08 EE04 5H007 AA08 BB06 CA01 CB02 CC23 DA03 DB03 DB12 DC05 EA03 5H560 AA02 BB04 BB07 BB12 DA13 EB01 GG04 RR01 SS07 TT15 UA02 XA03 XA12

Claims (4)

[Claims] An AC / DC converter converts AC power into DC and supplies the DC power to an inverter for driving a motor. The switching element of the inverter is PWM-controlled, while the power is supplied to a non-energized phase of the motor. The position of the rotor is detected based on the generated induced voltage waveform, and in the motor control method for switching the energization of the motor based on the detected position, the induced voltage waveform is captured and expanded into a Fourier series. Calculating a harmonic component of the induced voltage waveform from the developed Fourier series, shifting the phase of the calculated harmonic component by a predetermined value to a correction value, and setting the correction value to the PWM.
A motor control method, characterized in that a switching element of the inverter means is driven in addition to control to remove a harmonic component of the induced voltage waveform. 2. Inverter means for converting an AC power supply into a DC voltage by AC / DC conversion means and driving the motor as a predetermined voltage by the converter means included in the AC / DC conversion means. Supply to
PWM controlling the switching element of the inverter means,
And the switching element of the converter is PWM.
A motor control method for detecting a position of a rotor based on an induced voltage waveform generated in a non-energized phase of the motor, and switching energization of the motor based on the detected position. Taking the induced voltage waveform and developing it into a Fourier series, calculating a harmonic component excluding the fundamental wave of the induced voltage waveform from the developed Fourier series, and shifting the phase of the calculated harmonic component by a predetermined value. A motor, wherein the calculated correction value is added to the PWM control of the switching element of the converter means to drive the switching element to remove a harmonic component of the induced voltage waveform. Control method. 3. The motor control method according to claim 2, wherein said correction element is driven in consideration of PWM control of the switching element of said inverter means. 4. The motor control method according to claim 1, wherein the motor is mounted on an air conditioner and used at least for a compressor motor of the air conditioner.