JP2002101684A - Inverter control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter control system capable of stable operating over the entire range of the revolutions without producing a blank area on the operation area of an electric motor. SOLUTION: The inverter control system is composed of a sensorless DC brushless motor 4 having a rotor having a plurality of magnetic poles, an inverter 3 applying inverter output voltage in response to a drive signal on the sensorless DC brushless motor 4 for driving the sensorless DC brushless motor 4, a position detection circuit 5 for detecting the position of the magnetic poles of the sensorless DC brushless motor 4, and a microcomputer 6 generating the drive signal in response to the position of the magnetic poles and the frequency of a prescribed carrier and modifying the frequency of the prescribed carrier to the other frequency stored to a memory 7 when the frequency of the prescribed carrier is the integer times of the frequency of inverter output voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sensorless DC.
The present invention relates to an air conditioner having a brushless motor and an inverter control device that generates a pulse width modulation output.

[0002]

2. Description of the Related Art Normally, an air conditioner is provided with an inverter device for driving an electric motor used for a compressor. In particular, a sensorless DC brushless motor may be used as the electric motor. This sensorless DC
The brushless motor has a rotor having a plurality of magnetic poles, and a plurality of stator windings for generating a magnetic field for the rotor, and is driven by an inverter output voltage output from the inverter device. You.

[0003] On the other hand, a system including an inverter device and a sensorless DC brushless motor has an inverter control device for controlling the inverter device. Hereinafter, a system including these devices is referred to as an inverter control system.

Here, the inverter output voltage input to the sensorless DC brushless motor is pulse width modulated (P
WM), and a PWM inverter that outputs the PWM signal is often used as the inverter. Therefore, the inverter control device is also generally a PWM inverter control device that generates a drive signal such that a desired PWM signal is output in the PWM inverter device.

In the PWM inverter control device, a drive signal having a frequency synchronized with the rotation speed of the sensorless DC brushless motor is converted into an induced voltage generated in the stator winding by the rotation of the rotor of the sensorless DC brushless motor.
That is, it is generated based on a signal obtained in accordance with a change in the position of the magnetic pole of the rotor, and based on the result of comparing the generated drive signal with a carrier signal for carrying the drive signal, the above-described operation is performed again. A drive signal is being generated.

Here, the frequency of the carrier signal (hereinafter referred to as carrier frequency) affects the induced voltage waveform of the sensorless DC brushless motor, and also affects the accuracy of detecting the magnetic pole position of the rotor of the sensorless DC brushless motor. It is known to give. In many cases, the carrier frequency is always set to be constant without depending on the rotation speed of the sensorless DC brushless motor, and the ratio between the rotation speed of the sensorless DC brushless motor and the carrier frequency is usually not constant. .

Therefore, when the rotation speed of the sensorless DC brushless motor becomes such that the carrier frequency matches the integral multiple of the frequency of the inverter output voltage (hereinafter referred to as the inverter frequency), the drive signal of the PWM inverter control device is generated. , The number of carriers included in each rotation changes every rotation, and the phenomenon that rotation speed control becomes unstable occurs. Therefore, in order to avoid this phenomenon in the conventional PWM inverter device, a PWM which does not reach the rotation speed in the unstable region is used.
Signal is being output.

In the conventional inverter control system, a capacitor is interposed between the PWM inverter device and the ground to realize insulation and noise removal.

As described above, in the conventional inverter control system, the carrier frequency of the PWM inverter controller is set to a constant condition, and in a region where the rotation speed control is unstable, the rotation speed is avoided to avoid the sensorless DC brushless. The motor is running.

[0010]

However, in the conventional inverter control system, there is a problem that the use of the sensorless DC brushless motor is restricted because the blank region exists in the operating region as described above. In addition, since the carrier frequency of the PWM inverter control device is constant, the ratio between the rotation speed and the carrier frequency of the sensorless DC brushless motor is not constant, and the accuracy of magnetic pole position detection also changes with the rotation speed. There was a possibility that stable driving could not be expected.

Further, in the conventional inverter control system, there is a phenomenon called demagnetization in which the magnetic force of the rotor magnetic pole of the sensorless DC brushless motor decreases. This is PWM
Inverter is used for sensorless DC brushless motor
If the motor rotor is locked and no longer rotates while applying a voltage based on the WM signal, an abnormal magnetic field is applied to the rotor magnetic poles, and the magnetic force of the rotor magnetic poles decreases. is there.

[0012] Factors that cause the motor to be locked include an increase in the load on the motor and a failure in normal rotation of the motor rotor due to failure in magnetic pole position detection of the sensorless DC brushless motor. In the conventional PWM inverter device, when an abnormal state occurs in which the motor rotor is locked, the demagnetization of the rotor magnetic pole cannot be prevented.

Further, in the conventional inverter control system, there is also a problem that a leakage current flows from the PWM inverter device to the ground via the capacitor. In particular, in the conventional PWM inverter device, when the carrier frequency of the PWM inverter control device is arbitrarily changed, the leakage current value may exceed the regulation value.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and there is no blank region in the operation region of a motor such as a sensorless DC brushless motor, and stable operation over the entire rotation speed region is achieved. It is an object to provide a possible inverter control system.

[0015]

Means for Solving the Problems To solve the above-mentioned problems,
In order to achieve the object, in the inverter control system according to the present invention, an electric motor having a rotor having a plurality of magnetic poles, and an inverter output voltage according to a drive signal to the electric motor to drive the electric motor. An inverter device to be applied, a magnetic pole position detecting circuit for detecting a position of a magnetic pole of the electric motor, and an inverter control device for generating the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmitting the drive signal to the inverter device Wherein the inverter control device changes the predetermined carrier frequency to another carrier frequency when the predetermined carrier frequency is an integral multiple of the frequency of the inverter output voltage. And generating the drive signal.

According to the present invention, for example, when the rotation speed obtained by the position detection circuit for detecting the position of the rotor magnetic pole of the motor matches a predetermined rotation speed, the carrier frequency corresponding to the rotation speed is determined. Can drive the inverter device.

In the inverter control system according to the next invention, a motor having a rotor having a plurality of magnetic poles, and an inverter output voltage is applied to the motor in accordance with a drive signal to drive the motor. An inverter device, a magnetic pole position detection circuit that detects a position of a magnetic pole of the electric motor, an inverter control device that generates the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmits the drive signal to the inverter device, Wherein the inverter control device does not output the drive signal to the inverter device when the position of the magnetic pole has not been detected for a certain period of time.

According to the present invention, when the position detection signal of the magnetic pole is not input for a certain period of time while the inverter output voltage is being applied to the motor, it is recognized that the rotor of the motor is locked. The output of the drive signal to the inverter device can be stopped.

In the inverter control system according to the next invention, an electric motor having a rotor having a plurality of magnetic poles, and an inverter output voltage is applied to the electric motor in accordance with a drive signal to drive the electric motor. An inverter device, a magnetic pole position detection circuit that detects a position of a magnetic pole of the electric motor, an inverter control device that generates the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmits the drive signal to the inverter device, In the inverter control system provided with, the inverter control device, when the rotation speed of the motor calculated based on the position of the magnetic pole and the predetermined carrier frequency has a predetermined ratio,
The driving signal is generated by changing the predetermined carrier frequency to another carrier frequency set corresponding to the predetermined ratio.

According to the present invention, when the ratio between the rotation frequency obtained by the position detection circuit for detecting the position of the rotor magnetic pole of the motor and the carrier frequency driving the inverter device matches the predetermined ratio. In addition, the inverter device can be driven at a carrier frequency corresponding to the ratio.

In the inverter control system according to the next invention, a motor having a rotor having a plurality of magnetic poles, and an inverter output voltage is applied to the motor in accordance with a drive signal to drive the motor. An inverter device, a magnetic pole position detection circuit that detects a position of a magnetic pole of the electric motor, an inverter control device that generates the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmits the drive signal to the inverter device, In the inverter control system including: the inverter control device, from the state where the predetermined carrier frequency and the integer multiple of the frequency of the inverter output voltage match, the predetermined carrier frequency and the integer of the frequency of the inverter output voltage When transitioning to a state where the times do not match, the predetermined carrier frequency is And generating the driving signal by changing to other carrier frequency which is set in accordance.

According to the present invention, when the carrier frequency shifts from an inverter frequency at which the carrier frequency is an integral multiple of the inverter frequency to an inverter frequency at which the carrier frequency does not become an integral multiple of the inverter frequency, for example, a transition between the inverter device and the ground is performed. The inverter device can be driven at a carrier frequency that does not cause a leakage current of a prescribed value or more in a capacitor normally provided in the inverter.

In the inverter control system according to the next invention, a motor having a rotor having a plurality of magnetic poles, and an inverter output voltage is applied to the motor in accordance with a drive signal to drive the motor. An inverter device, a magnetic pole position detection circuit that detects a position of a magnetic pole of the electric motor, an inverter control device that generates the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmits the drive signal to the inverter device, In the inverter control system including: a leakage current detection circuit that detects a leakage current, the inverter control device, the predetermined carrier frequency, the other according to the value of the leakage current detected by the leakage current detection circuit The drive signal is generated by changing the carrier frequency to the above-mentioned carrier frequency.

According to the present invention, for example, the current carrier frequency can be changed to a carrier frequency at which the leakage current does not increase, according to the leakage current generated in the noise removing capacitor and the like.

[0025]

Embodiments of an inverter control system according to the present invention will be described below in detail with reference to the drawings. It should be noted that the present invention is not limited by the embodiment.

Embodiment 1 First, an inverter control system according to a first embodiment will be described. FIG.
FIG. 1 is a block diagram illustrating a schematic configuration of an inverter control system according to a first embodiment.

In FIG. 1, an inverter control system according to a first embodiment includes an AC power supply 1, a converter 2 for converting an AC to a DC voltage, and an inverter device 3 having a switching element for converting a DC voltage to a pseudo AC voltage. ,
A sensorless DC brushless motor 4, a position detection circuit 5 for detecting a magnetic pole position of a rotor of the sensorless DC brushless motor 4, a microcomputer 6 for giving a rotational speed command to the inverter device 3 by the position detection circuit 5, and a rotation used by the microcomputer 6. A memory 7 for storing a number command and a carrier frequency, a smoothing capacitor 8 for absorbing voltage ripples generated in the converter 2 and the inverter device 3
It comprises. The microcomputer 6 has the function of a conventional inverter control device.

The operation of the inverter control system will be described below. First, the position detection circuit 5 detects a magnetic pole position of the rotor based on an induced voltage waveform generated when the sensorless DC brushless motor 4 rotates, and outputs a position detection signal. The microcomputer 6 transmits a drive signal to the inverter device 3 in accordance with the position detection signal. Here, as the driving signal, the microcomputer 6 selects the optimum carrier frequency for the current rotation speed from the rotation speed information and the carrier frequency information stored in the memory 7 and drives the inverter device 3 at the carrier frequency. Is a signal generated as described above.

Here, it is assumed that the memory 7 stores a first rotational speed as an unstable rotational speed region and a first carrier frequency corresponding to the unstable rotational speed region. When the rotation speed obtained by the position detection circuit 5 is other than the first rotation speed, the microcomputer 6
The inverter device 3 is driven by a normal carrier frequency.

On the other hand, when the rotation speed obtained by the position detection circuit 5 matches the first rotation speed, the microcomputer 6 changes the normal carrier frequency to the first carrier frequency and changes the inverter frequency to the first carrier frequency. The device 3 is driven. If the number of revolutions again becomes other than the first number of revolutions,
The carrier frequency is set to the normal carrier frequency again and the inverter device 3 is driven.

The memory 7 can store a plurality of rotation speeds and carrier frequencies of a plurality of patterns in addition to the first rotation speed and the first carrier frequency. When the numbers match those patterns, the inverter device 3 can be driven by one carrier frequency predetermined for the number of rotations.

As described above, according to the inverter control system according to the first embodiment, the sensorless DC
When the number of rotations obtained by the position detection circuit 5 for detecting the position of the rotor magnetic pole of the brushless motor 4 matches the number of rotations stored in the memory 7, the inverter device 3 uses a carrier frequency corresponding to the number of rotations. To drive
It is possible to perform stable operation over the entire rotation speed range.

Embodiment 2 FIG. Next, an inverter control system according to the second embodiment will be described. The inverter control system according to the second embodiment is different from the inverter control system of FIG.
Inverter device 3 is sensorless DC brushless motor 4
When the position detection circuit 5 cannot detect the magnetic pole position for a certain period of time or more while outputting the inverter output voltage, the output of the inverter output voltage is stopped.

The operation of the inverter control system will be described below. First, the microcomputer 6
Transmits a drive signal to the inverter device 3,
An inverter output voltage which is a pseudo AC voltage is applied to the sensorless DC brushless motor 4. At this time, the rotor of the sensorless DC brushless motor 4 rotates, and a magnetic pole position detection signal is input to the microcomputer 6 via the position detection circuit 5.

At this time, if the inverter output voltage is continuously applied in a state where the rotor of the sensorless DC brushless motor 4 is locked and not rotating, as described above, the demagnetization in which the magnetic force of the rotor magnetic poles decreases. This phenomenon occurs. Therefore, as a means for preventing this, when the position detection signal is not input to the microcomputer 6 for a certain period of time during the application of the inverter output voltage, the microcomputer 6 stops outputting the drive signal to the inverter device 3.

As described above, according to the inverter control system according to the second embodiment, the microcomputer 6 detects the position of the magnetic pole while the inverter output voltage is applied to the sensorless DC brushless motor 4. If a signal is not input for a certain period of time, it is recognized that the rotor of the sensorless DC brushless motor 4 is locked, and the output of the drive signal to the inverter device 3 is stopped.
Can be prevented from being demagnetized.

Embodiment 3 Next, an inverter control system according to the third embodiment will be described. The inverter control system according to the third embodiment differs from the inverter control system of FIG.
It is characterized in that the carrier frequency is changed in accordance with the ratio between the rotation speed detected by the position detection circuit 5 and the carrier frequency in the drive signal transmitted to the inverter device 3.

Hereinafter, the operation of the inverter control system will be described. First, the memory 7 stores rotational speed information and carrier frequency information, and rotational speed and carrier frequency ratio information. Here, the ratio information is referred to as a first ratio and a second ratio, and The corresponding carrier frequency information is a first carrier frequency and a second carrier frequency, respectively. In particular, the carrier frequency set corresponding to these ratios becomes low when the rotation speed of the sensorless DC brushless motor 4 is low,
It is a value that increases when the rotation speed of the brushless motor 4 is high.

In this state, the microcomputer 6
Based on the current rotation speed and the carrier frequency of the sensorless DC brushless motor 4, the ratio between the rotation speed and the carrier frequency is calculated, and if this ratio matches the above-described first ratio, the first carrier frequency is changed. The second carrier frequency is selected when the selection is made and the ratio matches the above-described second ratio. Then, the inverter device 3 is driven at the selected carrier frequency.

As described above, according to the inverter control system of the third embodiment, the sensorless DC
The rotation speed obtained by the position detection circuit 5 for detecting the position of the rotor magnetic pole of the brushless motor 4 and the inverter device 3
Of the memory 7
, The inverter device 3 is driven at the carrier frequency corresponding to the ratio, so that stable operation can be performed over the entire rotation speed range.

Embodiment 4 FIG. Next, an inverter control system according to a fourth embodiment will be described. The inverter control system according to the fourth embodiment differs from the inverter control system of FIG.
When shifting from an inverter frequency at which the carrier frequency is an integral multiple of the inverter frequency to an inverter frequency at which the carrier frequency is not an integral multiple of the inverter frequency,
The carrier frequency for driving the inverter device 3 is selected from the carrier frequencies stored in the memory 7.

The carrier frequency selected at this time is such that the microcomputer 6 does not generate a leakage current exceeding a specified value in a capacitor (not shown) normally provided between the inverter device 3 and the ground. The carrier frequency is selected from the memory 7.

As described above, according to the inverter control system according to the fourth embodiment, the inverter frequency is shifted from the inverter frequency at which the carrier frequency is an integral multiple of the inverter frequency to the inverter frequency at which the carrier frequency is not an integral multiple of the inverter frequency. In doing so, the inverter device 3 can be driven at a carrier frequency at which a leakage current of a specified value or more does not occur in a capacitor normally provided between the inverter device 3 and the ground.

Embodiment 5 FIG. Next, an inverter control system according to a fifth embodiment will be described. The inverter control system according to the fifth embodiment is characterized in that a leakage current of a noise removing capacitor is detected, and it is determined whether or not to allow an increase in a carrier frequency according to a value of the detected leakage current. .

FIG. 2 is a block diagram showing a schematic configuration of the inverter control system according to the fifth embodiment. In FIG. 2, portions common to FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The inverter control system shown in FIG. 2 is different from the inverter control system shown in FIG.
And different.

The leakage current detecting circuit 10 is a circuit for detecting a current flowing from the device to the ground via the noise removing capacitor 9 and outputting the detected current to the microcomputer 6. The microcomputer 6 compares the value of the leakage current obtained from the leakage current detection circuit 10 with the threshold value of the leakage current stored in the memory 7, and determines that the value of the detected leakage current is greater than the threshold value. If it is determined to be low, the rise of the carrier frequency is permitted. Conversely, when it is determined that the value of the detected leakage current is higher than the threshold value, the increase of the carrier frequency is prohibited.

As described above, according to the inverter control system according to the fifth embodiment, the carrier frequency is allowed to increase in accordance with the leakage current of the noise removing capacitor. It is possible to prevent the leakage current of the noise removing capacitor from exceeding a specified value.

[0048]

As described above, according to the present invention, when a predetermined carrier frequency becomes an integral multiple of the frequency of the inverter output voltage, the predetermined carrier frequency is changed to another carrier frequency. For example, when the rotation speed obtained by the position detection circuit that detects the position of the rotor magnetic pole of the motor matches a predetermined rotation speed, the inverter device can be driven at a carrier frequency corresponding to the rotation speed. This makes it possible to expand the operating range of the electric motor.

According to the next invention, when the position detection signal of the magnetic pole is not inputted for a certain period of time while the inverter output voltage is being applied to the motor, it is recognized that the rotor of the motor is locked. Since the output of the drive signal to the inverter device is stopped, an effect is obtained that the rotor magnetic poles of the electric motor can be prevented from being demagnetized.

According to the next invention, the ratio between the rotation frequency obtained by the position detection circuit for detecting the position of the rotor magnetic pole of the motor and the carrier frequency driving the inverter device matches the predetermined ratio. In this case, since the inverter device is driven at the carrier frequency corresponding to the ratio, the difference in the position detection accuracy due to the rotation speed is reduced, and the stable operation can be performed over the entire rotation speed range. .

According to the next invention, from the inverter frequency at which the carrier frequency becomes an integral multiple of the inverter frequency,
When the carrier frequency shifts to an inverter frequency that does not become an integral multiple of the inverter frequency, for example, the inverter device is driven at a carrier frequency that does not cause a leakage current of a specified value or more in a capacitor normally provided between the inverter device and the ground. Therefore, there is an effect that the leakage current can be reduced.

According to the next invention, the change to another carrier frequency is permitted in accordance with the leakage current generated in the noise removing capacitor or the like. Can be prevented from exceeding the specified value.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of an inverter control system according to first to fourth embodiments.

FIG. 2 is a block diagram illustrating a schematic configuration of an inverter control system according to a fifth embodiment;

[Explanation of symbols]

1 AC power supply, 2 converters, 3 inverters,
4 brushless DC motor, 5 position detection circuit, 6 microcomputer, 7 memory, 8 smoothing capacitor, 9 noise removal capacitor, 10 leakage current detection circuit.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Sadao Yajima 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term within Mitsubishi Electric Corporation (reference) 5H560 AA02 AA10 BB04 BB12 DA13 DC20 EB01 JJ13 JJ15 RR10 SS07 TT08 TT11 TT15 UA02 XA12

Claims (5)

[Claims] An electric motor having a rotor having a plurality of magnetic poles, an inverter device for applying an inverter output voltage to the electric motor in accordance with a drive signal to drive the electric motor, and a position of a magnetic pole of the electric motor. An inverter control system comprising: a magnetic pole position detection circuit for detecting; and an inverter control device for generating the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmitting the drive signal to the inverter device. An inverter, wherein when the predetermined carrier frequency is an integral multiple of the frequency of the inverter output voltage, the predetermined carrier frequency is changed to another carrier frequency to generate the drive signal. Control system. 2. An electric motor having a rotor having a plurality of magnetic poles, an inverter device for applying an inverter output voltage to the electric motor in accordance with a drive signal to drive the electric motor, and a position of a magnetic pole of the electric motor. An inverter control system comprising: a magnetic pole position detection circuit for detecting; and an inverter control device for generating the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmitting the drive signal to the inverter device. An inverter control system, wherein the device does not output the drive signal to the inverter device when the position of the magnetic pole has not been detected for a predetermined time. 3. An electric motor having a rotor having a plurality of magnetic poles, an inverter device for driving the electric motor and applying an inverter output voltage to the electric motor in accordance with a drive signal, and determining a position of a magnetic pole of the electric motor. An inverter control system comprising: a magnetic pole position detection circuit for detecting; and an inverter control device for generating the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmitting the drive signal to the inverter device. The apparatus sets the predetermined carrier frequency corresponding to the predetermined ratio when the rotation speed of the motor calculated based on the position of the magnetic pole and the predetermined carrier frequency have a predetermined ratio. An inverter control system for generating the drive signal by changing the carrier frequency to another carrier frequency. 4. An electric motor having a rotor having a plurality of magnetic poles, an inverter device for applying an inverter output voltage to the electric motor in accordance with a drive signal to drive the electric motor, and a position of a magnetic pole of the electric motor. An inverter control system comprising: a magnetic pole position detection circuit for detecting; and an inverter control device for generating the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmitting the drive signal to the inverter device. The apparatus is configured such that when the predetermined carrier frequency and the integer multiple of the frequency of the inverter output voltage match, the state shifts to a state where the predetermined carrier frequency does not match the integer multiple of the frequency of the inverter output voltage. Changing the predetermined carrier frequency to another carrier frequency set according to the state, Inverter control system and generating a motion signal. 5. An electric motor having a rotor having a plurality of magnetic poles, an inverter device for applying an inverter output voltage to the electric motor in accordance with a drive signal to drive the electric motor, and a position of a magnetic pole of the electric motor. A magnetic pole position detection circuit for detecting, and an inverter control device for generating the drive signal according to the position of the magnetic pole and a predetermined carrier frequency and transmitting the drive signal to the inverter device, A leakage current detection circuit for detecting, the inverter control device, the predetermined carrier frequency is changed to another carrier frequency according to the value of the leakage current detected by the leakage current detection circuit, the drive signal An inverter control system characterized by generating.