JP2001286181A - Motor control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce torque ripples by removing harmonics in the induced voltage in a motor control method. SOLUTION: An AC power source is supplied to an inverter circuit 3 which drivers a motor 4 by converting an AC power source into DC with an AC/DC converting circuit 2. A control circuit 12 which controls the motor 4 with PWM (pulse width modulation) divides an induced voltage, a motor speed and a drive current into a plurality of stages within the control range of the motor. At each stage the induced voltage is developed in a Fourier series in a harmonics component analyzing part 12b, and the harmonics involved in the induced voltage is calculated. Correction values which differ the phase angle of these calculated harmonics components in 170 degrees is calculated by a phase correction part 12c and the calculated correction values are memorized in a memory part 12d. When the motor 4 is controller in PWM, each transistor of the inverter circuit 3 is driven by the current PWM control to which the correction values read from the memory part 12d where they are preliminarily memorized is added in a PWM generator 10c.

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 DC 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 and controlling a torque ripple of the motor. The present invention relates to a method for controlling a motor for reducing the motor speed.

[0002]

2. Description of the Related Art A motor control device has, for example, the configuration shown in FIG.
The converted DC power is converted by the C conversion circuit 2 and the converted DC power is switched by the inverter circuit 3 and supplied to the motor 4 as a three-phase rectangular wave voltage. The switching of the inverter circuit 3 is performed by a PWM waveform described later, and the drive current of the motor 4 is determined by the PWM waveform (in other words, the rotation speed is determined).

[0003] For example, in a control device for a high-output air conditioner, a converter section is included in an AC / DC conversion circuit 2.
There is a type in which a switching element of a converter unit is PWM-controlled to vary an output DC voltage. At this time, since the motor drive current can be changed by varying the output DC voltage of the converter section, the drive current of the motor 4 can be further increased by the PWM control of the inverter circuit 3 in addition to the control of the converter section. And the output of the air conditioner can be increased.

Further, the position of the rotor is detected by a position detection circuit 5, and a signal for the position detection is input to a control circuit (microcomputer) 6, which drives a transistor of the inverter circuit 3 to drive the motor. 4. The stator winding current of No. 4 is switched (the energization is switched).

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 the virtual neutral point voltage of the motor 4, and the virtual neutral point voltage (that is, the virtual neutral point voltage). The induced voltage) is compared with a reference voltage generated by a voltage generation circuit 5b by a comparison circuit 5c, and a result of the comparison is used as a position detection control circuit (microcomputer or the like)
6 is output.

In the case of the above-described PWM control method, the control circuit 6 switches the energization of the armature winding based on the position detection, while setting the drive current of the motor to a predetermined value (by changing the rotation speed to the target rotation speed). ), A PWM waveform is generated by the PWM generator 6a, and a control signal obtained by superimposing the generated PWM waveform on the energization switching signal is output to the inverter circuit 3 via the internal driver. 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 the energization of the armature winding of the motor 4 is switched, while the drive current of the motor is controlled in a predetermined manner. Thus, the motor rotation speed can be set to the target rotation speed.

[0007]

However, in the above-described motor control method, no consideration is given to harmonic components included in the induced voltage used for detecting the position of the rotor (see FIG. a) and (b)), and the harmonic component has caused torque ripple. 5 (a) and 5 (b) show the induced voltage waveform and the harmonic when a three-phase four-pole motor uses 24 slots as a stator.

For example, as the above harmonic component, when reluctance torque is generated even in a motor in which a permanent magnet is embedded, there is a ripple (higher harmonic) generated by the interaction between the slot of the stator and the reluctance torque. 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. 5A), so that the position detection of the rotor is not appropriate. As a result, the energization switching of the motor 4 is not optimally performed, which 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]

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 inverter means for driving the motor. PWM switching means
Controlling, by detecting the position of the rotor by the induced voltage generated in the non-energized phase of the motor, the motor control method for switching the energization of the motor based on the position detection,
The magnitude of the induced voltage, the number of rotations of the motor and the magnitude of the drive current are divided into a plurality of stages in the control range of the motor, and the induced voltage waveform is taken in each of these stages and developed into a Fourier series. The harmonic component of the induced voltage waveform is calculated from the calculated Fourier series, the phase of the calculated harmonic component is shifted by a predetermined value and stored in a storage unit as a correction value. The magnitude, the number of rotations of the motor and the magnitude of the drive current are detected, and the correction value read out from the storage means is stored in the same P.
In addition to the WM control, a switching element of the inverter is driven to remove a harmonic component of the induced voltage waveform.

According to the present invention, AC power is converted to DC by AC / DC conversion means and supplied to an inverter means for driving the motor, and a switching element of the inverter means is PWM-controlled to de-energize the motor. In a motor control method for detecting the position of a rotor by an induced voltage generated in a phase and switching the energization of the motor based on the position detection, the magnitude of the induced voltage, or the number of rotations or driving of the motor is controlled. At least one of the magnitudes of the current is divided into a plurality of stages in the control range of the motor, the induced voltage waveform is taken in each stage and developed into a Fourier series, and the induced voltage waveform is derived from the developed Fourier series. A harmonic component is calculated, and a phase of the calculated harmonic component is shifted by a predetermined value and stored in a storage unit as a correction value. A correction value read from the storage means by detecting at least one of the magnitude of the induced voltage or the number of rotations of the motor or the magnitude of the drive current, and outputs the correction value to the switching element of the inverter means. In addition to the above PWM control, the 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 direct current by an AC / DC converter and supplied to an inverter for driving the motor. The switching element of the converter included in the AC / DC converter is provided. And a PWM control method of a switching element of the inverter means, a position of the rotor is detected by an induced voltage generated in a non-energized phase of the motor, and a motor control method for switching the energization of the motor based on the position detection. In the above, the magnitude of the induced voltage, the number of rotations of the motor and the magnitude of the drive current are divided into a plurality of stages in the motor control range, and an induced voltage waveform for at least one revolution is developed into a Fourier series for each of these stages. Then, a harmonic component of the induced voltage waveform is calculated from the developed Fourier series, and the phase of the calculated harmonic component is shifted by a predetermined value to compensate. Is stored in the storage means as a value,
At the time of the PWM control of the motor, the magnitude of the induced voltage, the number of rotations of the motor and the magnitude of the drive current are detected, and the correction value read from the storage unit is added to the PWM control of the switching element of the inverter unit. Alternatively, in addition to the PWM control of the switching element of the converter, the switching element of the inverter or the converter is driven to remove a harmonic component of the induced voltage waveform.

According to the present invention, the AC / DC converter converts the AC power into DC and supplies the DC to an inverter for driving the motor, and the switching element of the converter included in the AC / DC converter. And a PWM control method of a switching element of the inverter means, a position of the rotor is detected by an induced voltage generated in a non-energized phase of the motor, and a motor control method for switching the energization of the motor based on the position detection. In the method, the induced voltage waveform is captured and at least one of the magnitude of the induced voltage, the number of rotations of the motor or the magnitude of the drive current is used.
Are divided into a plurality of stages in the control range of the motor, and the induced voltage waveform captured for at least one rotation for each stage is developed into a Fourier series, and a harmonic component of the induced voltage waveform is calculated from the developed Fourier series. The phase of the calculated harmonic component is shifted by a predetermined value and stored in the storage unit as a correction value. During PWM control of the motor, the magnitude of the induced voltage, or the magnitude of the number of revolutions or current of the motor, The correction value read from the storage means by detecting at least one of them is added to the PWM control of the switching element of the inverter means, or is added to the PWM control of the switching element of the converter means. A switching element of the inverter means or the converter means is driven to remove a harmonic component of the induced voltage waveform. It is characterized in that there was Unishi.

It is preferable that the correction value read from the storage unit is added to the PWM control of the switching elements of both the inverter unit and the converter unit. As a result, harmonic components included in the induced voltage waveform are appropriately removed, and torque ripple is sufficiently reduced.

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

[0016]

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 this motor control method is applied includes a current sensor (CT) 10 for detecting a drive current of a motor 4 and a current detection circuit 11.
A rotation speed detector 12a for detecting the rotation speed of the motor 4 based on the position detection signal, the magnitude of the induced voltage (virtual neutral point voltage), the rotation speed of the motor 4 and the driving current in a plurality of steps in the control range of the motor 4. And a harmonic component calculation unit 12b that takes in the induced voltage waveform for each of these stages, expands the waveform into a Fourier series, and calculates a harmonic component, and calculates the calculated harmonic to remove the harmonic component of the induced voltage waveform. A phase correction unit 12c that shifts the phase of the component by a predetermined value to obtain a correction value, a storage unit 12d that stores the correction value, and a PWM value that takes into account the correction value read from the storage unit 12d during the PWM control of the motor 4.
And a control circuit (microcomputer or the like) 12 having a PWM generator 12e for generating a waveform. The control circuit 12 also has the function of the control circuit 6 shown in FIG. 4, and the PWM generator 12e is a PWM generator 6a shown in FIG.
It also has the function of

More specifically, in the control of the motor 4, the number of rotations and the drive current change from the minimum to the maximum,
Since the magnitude of the induced voltage changes from the minimum to the maximum with this, the range from the minimum to the maximum is divided into a plurality of stages. In order to develop the induced voltage waveform into a Fourier series for each stage, the harmonic component calculation unit 12b performs A / D conversion on at least the induced voltage waveform by an internal A / D converter, and performs one rotation of the rotor ( 360 degrees) and store it once,
The stored data is expanded into a Fourier series to calculate a harmonic component. Such an expansion to the Fourier series will be apparent from the fact that the induced voltage is generated with the rotation of the rotor and has periodicity.

The phase correction unit 12c shifts the phase of the harmonic component by 180 degrees, calculates data for canceling out the harmonic component of the induced voltage waveform, and sets it as a correction value.
Stored in d. In this way, the storage unit 12d stores the correction value for one rotation for each step for the magnitude of the induced voltage, the number of rotations, and the magnitude of the driving current. Then, at the time of the PWM control of the motor 4, the PWM generation unit 12e outputs the correction value read from the storage unit 12d at each stage to the current P value.
Output in addition to WM waveform (output after adding or subtracting).

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. The control circuit 10 changes the magnitude of the induced voltage, the rotation speed of the motor 4, and the drive current from the minimum to the maximum in the control range of the motor 4 in order to calculate the correction value stored in the storage unit 12 d.

In this case, the control circuit 10 executes a routine shown in FIG. 2 for each stage of the magnitude of the induced voltage, the number of rotations of the motor 4 and the magnitude of the drive current, and executes the routine of FIG. The rotation speed and the drive current are detected (step ST1). Thereafter, the induced voltage waveform is A / D converted and taken in, and the data of the induced voltage waveform is stored in the rotor 1.
The rotation amount is stored (step ST2).

Subsequently, the harmonic component calculation unit 12b of the control circuit 12 expands the data for one rotation into a Fourier series of a sine function system or a cosine function system to calculate a harmonic component (step ST3). In this case, in the 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, the fundamental wave (Fig. 3
Other parts (that is, higher harmonics except for (b)); FIG.
(See (c)). The calculated harmonic is mainly the eleventh harmonic in the case of a three-phase quadrupole, 24-slot motor, but also includes some harmonics of other orders.

Subsequently, the phase correction unit 10b shifts the phase of the calculated harmonic component by 180 degrees (see FIG. 3D), and calculates a correction value for removing the harmonic component of the induced voltage waveform. (Step ST4), the correction value is stored in the storage unit 1
2d (step ST5). The above-described routine is repeated for each stage, and a correction value is calculated for each stage and stored in the storage unit 12d, that is, the correction value is stored in a table format in advance.

At the time of PWM control of the motor 4, a correction value is read from the storage unit 12d in accordance with the magnitude of the induced voltage, the number of rotations, and the magnitude of the drive current, and the read correction value is stored in the PWM generation unit 12e. Is added to the PWM waveform. That is, the PWM waveform for driving the motor 4 is corrected, and a pattern output process of the corrected PWM waveform is performed.

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

As described above, the torque ripple of the motor 4 is reduced by removing the harmonic components. In addition, when the motor 4 is controlled at a variable speed, for example,
Is changed, the correction value for correcting the current PWM waveform is newly read out from the storage unit 12d, and the new correction value is added to the PWM waveform to obtain an output pattern. Therefore, even if the number of revolutions of the motor 4 changes and the magnitude of the induced voltage or the drive current changes, harmonic components included in the induced voltage waveform are appropriately removed, and the torque ripple of the motor 4 is also reduced. Is done.

In the above-described embodiment, the correction value of the PWM waveform for removing the harmonic component is calculated for each step for the magnitude of the induced voltage, the number of rotations, and the magnitude of the drive current. , For at least one of them, that is, the magnitude of the induced voltage, or the number of revolutions or the drive current, calculate the correction value of the PWM waveform for each stage, and store it in the storage unit 12d. You may put it. In this case, there is an advantage that the capacity of the storage unit 12d may be small.

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 contained in the induced voltage as described above, and the torque ripple of the motor 4 is reduced.

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 above-described two actions are simultaneously performed, harmonic components included in the induced voltage waveform are appropriately removed, and the torque ripple of the motor 4 is appropriately reduced.

If the above-described control method is applied to a compressor motor of an air conditioner, etc., reduction in torque ripple contributes to improvement in operation efficiency of the air conditioner and improvement in power saving.

[0031]

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 furthermore, the magnitude of the induced voltage and the rotation speed of the motor. And the magnitude of the drive current is divided into a plurality of stages in the control range of the motor, and a correction value for canceling out the harmonic component is obtained and stored at each of these stages or at least at each one of them. Since the correction value is read from the storage means and added to the PWM control during the PWM control of the motor, the harmonic component of the induced voltage waveform is removed. Therefore, the torque ripple of the motor can be reduced by cutting the harmonic component (ripple), and the fluctuation of the motor (the fluctuation of the magnitude of the induced voltage,
(Fluctuations in the number of rotations and fluctuations in the magnitude of the driving current) also remove the harmonic components, thereby properly reducing the torque ripple of the motor, and thus improving the efficiency of the motor and saving power. There is an effect that it is possible to achieve improvement of the structure.

Further, the induced voltage waveform using the position detection circuit of the motor is developed into a Fourier series, and a harmonic component is extracted from the Fourier series. This processing is performed by a microcontroller which is control means of the motor. 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]

 REFERENCE SIGNS LIST 1 AC power supply 2 AC / DC conversion circuit (including converter section) 3 Inverter circuit 4 Motor 5 Position detection circuit 6, 12 Control circuit (microcomputer) 6 a, 12 e PWM generator 10 Current sensor (CT) 11 Current detection circuit 12 a Rotation Number calculation unit 12b Harmonic component calculation unit 12c Phase correction unit 12d Storage unit

Claims (6)

[Claims] An AC / DC converter converts AC power into DC and supplies the DC power to an inverter for driving the motor. A switching element of the inverter is PWM.
Controlling, by detecting the position of the rotor by the induced voltage generated in the non-energized phase of the motor, the motor control method for switching the energization of the motor based on the position detection,
The magnitude of the induced voltage, the number of rotations of the motor and the magnitude of the drive current are divided into a plurality of stages in the control range of the motor, and the induced voltage waveform is taken in each of these stages and developed into a Fourier series. The harmonic component of the induced voltage waveform is calculated from the calculated Fourier series, the phase of the calculated harmonic component is shifted by a predetermined value and stored in a storage unit as a correction value. The magnitude, the number of rotations of the motor and the magnitude of the drive current are detected, and the correction value read out from the storage means is stored in the same P.
A method of controlling a motor, comprising: driving a switching element of the inverter means in addition to WM control to remove a harmonic component of the induced voltage waveform. 2. The method according to claim 1, wherein the AC power is converted into a direct current by an AC / DC converter and supplied to an inverter for driving the motor.
Controlling, by detecting the position of the rotor by the induced voltage generated in the non-energized phase of the motor, the motor control method for switching the energization of the motor based on the position detection,
At least one of the magnitude of the induced voltage, or the number of rotations of the motor or the magnitude of the drive current is divided into a plurality of stages in the control range of the motor, and the induced voltage waveform is taken in each stage to obtain a Fourier series. The calculated harmonic component of the induced voltage waveform is calculated from the expanded Fourier series, and the phase of the calculated harmonic component is shifted by a predetermined value and stored in a storage unit as a correction value.
At the time of the WM control, the magnitude of the induced voltage or at least one of the number of rotations of the motor or the magnitude of the driving current is detected, and a correction value read from the storage means is read by the switching means of the inverter means. A method for controlling a motor, comprising driving a switching element of the inverter means in addition to PWM control of the element to remove a harmonic component of the induced voltage waveform. 3. An AC / DC converter converts AC power into DC and supplies the DC power to an inverter for driving the motor. The AC / DC converter includes a switching element of a converter included in the AC / DC converter and the inverter. PWM control of the switching element of the inverter means, detecting the position of the rotor by the induced voltage generated in the non-energized phase of the motor,
In the motor control method for switching the energization of the motor based on the position detection, the magnitude of the induced voltage,
The number of rotations of the motor and the magnitude of the driving current are divided into a plurality of stages in the motor control range, and an induced voltage waveform for at least one rotation is developed into a Fourier series for each of these stages,
A harmonic component of the induced voltage waveform is calculated from the expanded Fourier series, and a phase of the calculated harmonic component is shifted by a predetermined value and stored in a storage unit as a correction value. The magnitude of the voltage, the number of revolutions of the motor and the magnitude of the drive current are detected and the correction value read from the storage means is added to the PWM control of the switching element of the inverter means, or the switching element of the converter means is added. A motor that drives a switching element of the inverter means or the converter means in addition to the PWM control of the above, and removes a harmonic component of the induced voltage waveform. 4. An AC / DC converter converts AC power into DC and supplies the DC power to an inverter for driving the motor. The AC / DC converter includes a switching element of a converter included in the AC / DC converter and the inverter. PWM control of the switching element of the inverter means, detecting the position of the rotor by the induced voltage generated in the non-energized phase of the motor,
In the motor control method for switching the energization of the motor based on the position detection, the induced voltage waveform is captured, and at least one of the magnitude of the induced voltage, the number of rotations of the motor, or the magnitude of the driving current is determined. Are divided into a plurality of stages in the control range of the motor, and the induced voltage waveform captured for at least one rotation for each stage is developed into a Fourier series, and a harmonic component of the induced voltage waveform is calculated from the developed Fourier series. The phase of the calculated harmonic component is shifted by a predetermined value and stored in the storage unit as a correction value. During PWM control of the motor, the magnitude of the induced voltage, or the magnitude of the number of revolutions or current of the motor, The correction value read from the storage means by detecting at least one of the above-mentioned ones is used as the PW of the switching element of the inverter means. In addition to the control or the PWM control of the switching element of the converter means, the switching element of the inverter means or the converter means is driven to remove a harmonic component of the induced voltage waveform. Motor control method. 5. The correction value read from the storage means,
The method of controlling a motor according to claim 3 or 4, wherein said method is added to PWM control of switching elements of both said inverter means and said converter means. 6. The method of controlling a motor 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.