JP2002291251A - Control method of compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To aim at reducing the switching loss and also harmonic currents in stop of a compressor or in the PWM control. SOLUTION: A switching means of an active filter is driven as following so that an input AC waveform becomes sinusoidal and at the same time, the PWM control is carried out. In stop of the motor or in the PWM control, the input AC current is detected every fixed time t, until the input AC current reaches 5A, the set output DC voltage of the active filter is made 70V which is lower than the output DC voltage of the active filter (see Fig. 1), when the input AC current exceeds 5A, the set output DC voltage is made 120V which is higher than 70V and lower than the output DC voltage (see t 5 in Fig.). By this constitution, the switching means of the active filter is stopped near the input AC current peak (see figure 1 (b)).

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 controlling a motor of a compressor (for example, a brushless DC motor) of an air conditioner or the like by an inverter, and more particularly, to an output DC of a power factor improving power supply circuit (active filter). The present invention relates to a compressor control method for controlling a voltage.

[0002]

2. Description of the Related Art A recent air conditioner or the like generally employs inverter control for a compressor motor. In this inverter control, an AC power supply is converted into a DC power supply, and the converted DC voltage is converted into an arbitrary AC voltage by an inverter and applied to the motor.

When a general capacitor input type power supply circuit is used as means for converting the AC power supply into a DC power supply,
The waveform of the input AC current from the AC power supply becomes distorted, and a harmonic current is generated. In order to make the input AC current waveform substantially sinusoidal (sinusoidal), for example, as shown in FIG. 5, a control device including a power supply circuit including a boost converter type active filter has been proposed.

In FIG. 5, the control device includes a rectifying unit 2 for full-wave rectifying an input AC power supply (commercial power supply) 1 and converting the DC voltage to a DC voltage. An active filter unit 3 for controlling a waveform in a sine wave shape, an inverter unit 5 for converting an output DC voltage of the active filter unit 3 into a three-phase AC voltage and applying it to a compressor motor 4, and an active filter unit 3. An active filter control unit 6 to be controlled, and a control circuit (microcontroller) that outputs a control signal (a value of a set output DC voltage) of the active filter control unit 6 and a control signal (including a PWM waveform) of a switching element of the inverter unit 5 And a driver unit 8 that drives a switching element of the inverter unit 5 by the control signal.

The active filter section 3 includes a rectifying section 2
Choke coil 3a connected in series to the positive terminal side of
A reverse blocking diode 3b connected in series to the boost choke coil 3a, and a switching element (IGBT; insulated gate transistor) connected between the boost choke coil 3a and the reverse blocking diode 3b on the negative terminal side of the rectifier 2.
3c, a smoothing capacitor 3d for smoothing the output voltage,
An input voltage detection circuit 3e for detecting an input voltage, a current detection circuit (shunt resistor) 3f for detecting the current, and an output voltage detection circuit 3g for detecting an output voltage are provided.

According to the above control device, the active filter section 3 is used to set the rotation speed of the motor 4 to the target operating frequency of the compressor required for controlling the room temperature.
And drives the switching element of the inverter unit 5 on and off. In this case, the control circuit 7 outputs a control signal (start, value of set output DC voltage; set value) necessary for the active filter control unit 6 in order to set the current operating frequency of the compressor to the target operating frequency. ,
The motor 4 is subjected to PWM control, and then PAM control is performed.

The active filter control unit 6 receives the input voltage, current and output voltage detected by the active filter unit 3 so that the input AC current waveform becomes sinusoidal and the output DC voltage becomes a set value. And IGB
T3c is switched in a predetermined manner. By the above control, the input AC current waveform becomes the waveform shown in FIG. 6A, and the choke coil current waveform becomes the waveform shown in FIG. 6B. Since the operation of the active filter unit 3 is already known, a description thereof will be omitted.

[0008] As described above, since the input AC current waveform has a sine wave shape, the distortion wave of the input AC current waveform is reduced, so that the harmonic current can be reduced and the power factor can be improved. it can.

The active filter control section 6 activates the active filter section 3 in accordance with a set value of a control signal (start, output DC voltage) from the control circuit 7 and boosts the output DC voltage to the set value. For example, in the case of an air conditioner, the set value of the output DC voltage is (square root 2) × input voltage × 1.2 (input voltage fluctuation) +10 V in consideration of the operation guarantee range of the input voltage fluctuation. Specifically, if AC100V is rated,
The set value (set output DC voltage) of the output DC voltage at the time of startup is 180 V.

[0010]

In the above-described compressor control method, PWM control and PAM control are performed. In PWM driving, a plurality of switching elements of the inverter unit 5 are turned on and off. As a result, the switching loss increases, and the power loss of the air conditioner increases, which is not preferable from the viewpoint of energy saving.

Therefore, for example, when the motor 4 is driven by PWM, the output of the active filter section 3 is kept constant (P
When the AM drive is constant), the control of the active filter unit 3 is stopped to compensate for the increase in the loss, and
It is conceivable to stop the switching of the GBT 3c to eliminate the switching loss caused by the IGBT 3c. However, when the control of the active filter section 3 is stopped, the power supply circuit naturally becomes a capacitor input type power supply circuit, the input AC current waveform is distorted, and the harmonic current increases, which is not preferable.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to partially stop the switching operation of an active filter at the time of stopping a compressor and PWM control so as to suppress the switching loss of the active filter and to reduce air flow. It is an object of the present invention to provide a compressor control method capable of reducing a power loss of a harmony machine or the like and suppressing a harmonic current.

[0013]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention converts an AC power supply into a DC voltage by a rectifier and supplies the DC voltage as a predetermined DC voltage to an inverter by an active filter. When the inverter is applied as an arbitrary AC voltage to the motor of the compressor to operate the motor, the switching means of the active filter is driven in a predetermined manner so that at least the input AC current waveform is sinusoidal. In a control method of a compressor for performing PWM control and PAM control for driving a motor, when the motor is stopped or P
At the time of WM control, the output DC voltage of the active filter is detected, the set output DC voltage of the active filter is made lower than the output DC voltage, and the input AC current or the secondary current is detected. The output DC voltage set according to the current or the secondary current is varied in a range lower than the output DC voltage, and the switching means of the active filter is stopped at least near the peak of the input AC current waveform. It is characterized by:

The set output DC voltage is set higher when the input AC current or the secondary current is larger than a predetermined value than when the input AC current or the secondary current detected every predetermined time is equal to or smaller than a predetermined value. Good. As described above, the switching loss of the active filter is appropriately suppressed, and the PWM control is appropriately performed.

The predetermined time for detecting the input AC current or the secondary current is detected for each cycle of the input AC power supply.
As this input AC current or secondary current increases,
It is preferable to increase the set output DC voltage. This makes the control of the active filter smoother,
The switching loss of the switching means is finely suppressed.

[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. 2,
The same parts as those in FIG. 5 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 2, a control device to which the compressor control method is applied includes a current sensor (CT) 10 for detecting an input AC current Iac at predetermined time intervals when the compressor motor 4 is stopped and when PWM control is performed. When the motor 4 of the compressor is stopped and when the PWM control is performed, the set output DC voltage of the active filter unit 3 is made lower than the output DC voltage of the active filter unit 3 and the set output DC voltage is reduced. A control circuit (microcomputer) 12 that varies according to the input AC current Iac and stops switching of the IGBT 3c of the active filter unit 3 at least near the peak of the input AC current waveform.

The active filter control section 6 has a function of outputting a detected output DC voltage to the control circuit 12 unlike a general control IC. When this general control IC is used, the active filter unit 3
May be provided with a voltage detection circuit for detecting the output DC voltage on the output side of. The other parts of the control device are the same as those of the control device shown in FIG. 5, and the control circuit 12 also has the function of the control circuit 7 shown in FIG.

Next, the operation of the control device having the above configuration will be described with reference to the time chart of FIG. 1, the flowchart of FIG.
This will be described with reference to the waveform diagram of FIG. First, the control circuit 12
When the compressor is stopped, the output DC voltage of the active filter unit 3 is output to the active filter control unit 6 during PWM control, and a PWM signal is output to the inverter unit 5 during PWM control.

At this time, the input AC current Iac is detected every predetermined time t (step ST1), and the input AC current Ia is detected.
If c is equal to or smaller than a predetermined value (for example, 5 A), the process proceeds to step ST
The process proceeds from step 2 to ST3, where the set output DC voltage of the active filter unit 3 is set to a predetermined value lower than the output DC voltage of the active filter unit 3. The output DC voltage is a value at the time when the input AC current Iac is detected.

As shown in FIG. 1, when the compressor is stopped, the input AC current is 100 V.
The output DC voltage of the active filter unit 3 becomes 140V. Therefore, at the time point t1, the set output DC voltage of the active filter unit 3 is set to 70V which is lower than the output DC voltage 140V. Further, even when the PWM control of the compressor is started (see time points t2 to t4), since the input AC current Iac is 5 A or less, the set output DC voltage of the active filter unit 3 is reduced to 70 V which is lower than the output DC voltage 140 V. Leave it alone.

As described above, since the set output voltage is 70 V, which is lower than usual, the switching of the IGBT 3c by the active filter control unit 6 is stopped near the peak of the input AC current waveform. This is because the output DC voltage of the active filter unit 3 exceeds 70 V near the peak of the input AC current waveform.

The fact that the switching of the IGBT 3c is partially stopped means that, as shown in FIG. 4B, the active filter unit 3 is stopped in the section B in FIG. 4 and operates in the section A in FIG. Will be. In this case, since the set output DC voltage is as low as 70 V, the section A is short and the section B is long.

When the motor 4 is stopped and the PWM control is performed, there is a section in which the IGBT 3c is not switched. Therefore, the switching loss of the active filter unit 3 is suppressed in a wide range including the peak of the input AC current waveform (see section B in FIG. 4B), and the loss during PWM control is reduced. Power loss. In the section A, since the input AC current waveform is controlled to have a sinusoidal waveform (see FIG. 4A), the harmonic current can also be reduced. In the choke coil current waveform of FIG. 4B, the shape shown by the dashed curve in FIG. 4B is realistic, and the input AC current also has the accompanying waveform (FIG. 4A, the dashed curve). reference).

At the time of the PWM control, since the set output DC voltage is low, when the applied voltage of the motor 4 is increased by changing the duty of the PWM waveform in order to set the rotation speed of the motor 4 to the target rotation speed, Input AC current Iac
Rises. Then, when the input AC current Iac detected at time t5 becomes 5 A or more (see FIG. 1), the process proceeds from step ST2 to ST4, and the active filter unit 3
Is set to 120 V which is higher than the previous 70 V and lower than the output DC voltage 140 V.

As a result, the range of the PWM control is widened, that is, the PWM control is appropriately performed, and the rotation speed of the motor 4 can be set to the target rotation speed. Further, since the set output DC voltage is lower than the output DC voltage 140 V as before, the IGBT
The switching of 3c is stopped near the peak of the input AC current waveform. When the switching of the IGBT 3c is partially stopped, as shown in FIG. 4, the active filter unit 3 stops in the section D in FIG. 4D and operates in the section C in FIG.

As described above, since a section in which the IGBT 3c is not switched occurs, near the peak of the input AC current waveform (see section D in FIG. 4D).
The switching loss of the active filter unit 3 is suppressed,
By reducing the loss during the PWM control, the power loss of the air conditioner is suppressed. Further, in the section D, since the input AC current waveform is controlled to have a sine wave shape (see FIG. 4C), the harmonic current can be reduced. In addition, since the switching section of the IGBT 3c is longer than before, that is, the operating range of the active filter unit 3 is wider than that when the set output DC voltage is 70 V, the input AC current waveform becomes closer to a sine wave, and the The current can be reduced than before.

In driving the motor 4, PWM control and PAM control are performed. In the PWM control, when the duty ratio becomes 100%, the control is switched to the PAM control (see FIG. 1). Further, as described above, in order to suppress the switching loss of the active filter unit 3, the duty ratio of the PWM control becomes 100% at a timing earlier than before.

As shown in FIG. 1, assuming that the duty ratio has reached 100% after the time point t6 in FIG.
It will be switched to M control. In the PAM control, the output DC voltage becomes equal to the set output DC voltage (see FIG. 1). Also, the harmonic current is reduced as in the conventional case.

In the above embodiment, the input AC current Ia
c is detected every predetermined time t, and the set output DC voltage is set to 70 V or 12
Although the voltage is set to 0 V, a plurality of set output DC voltages may be set by setting a plurality of input AC currents Iac. In this case, the suppression of the switching loss of the active filter unit 3 and the reduction of the loss at the time of the PWM control can be performed more finely.
A sinusoidal waveform (reduction of harmonic current) of the input AC current waveform can be performed more finely.

The detection interval of the input AC current Iac is
It may be every cycle (one cycle or half cycle) of the input AC power supply 1. In this case, since the set output DC voltage of the active filter unit 3 can be switched for each cycle, the control becomes smooth. Furthermore, instead of detecting the input AC current Iac, the same operation and effect as in the above embodiment can be obtained even if a secondary current (a so-called current of the active filter unit 3) is detected.

[0032]

According to the present invention described above, the following effects can be obtained. The present invention relates to a compressor control method for performing PWM control and PAM control on a motor of a compressor, wherein the output DC voltage of the active filter is detected and the set output DC voltage of the active filter is adjusted when the motor is stopped or during PWM control. Lower than the output DC voltage, detect the input AC current or the secondary current, and vary the set output DC voltage in a range lower than the output DC voltage according to the detected input AC current or the secondary current; Since the switching means of the active filter is stopped at least near the peak of the input AC current waveform, the switching loss of the active filter is suppressed when the motor is stopped or the PWM control is performed, and the power loss of the air conditioner is reduced. Reduce harmonic current as well as reduce There is an effect that theft can be.

[Brief description of the drawings]

FIG. 1 is a schematic time chart illustrating a method of controlling a compressor according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram for explaining a control device to which the control method of the compressor shown in FIG. 1 is applied.

FIG. 3 is a schematic flowchart for explaining the operation of the control device shown in FIG. 2;

FIG. 4 is a schematic waveform diagram for explaining the operation of the control device shown in FIG. 2;

FIG. 5 is a schematic block diagram for explaining a conventional motor control device.

FIG. 6 is a schematic graph for explaining the operation of the control device shown in FIG. 5;

[Explanation of symbols]

 Reference Signs List 1 input AC power supply (commercial power supply) 2 rectifier 3 active filter 3a boost choke coil 3c switching element (IGBT) 3d smoothing capacitor 4 motor (of compressor) 5 inverter 6 active filter controller 7, 12 control circuit (microcomputer) ) 10 Current sensor (CT) 11 Current detection circuit t Predetermined time Iac Input AC current

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02M 7/5387 H02M 7/5387 Z F term (Reference) 3L060 AA03 AA05 CC10 DD02 EE02 5H006 AA02 BB05 CA01 CA07 CA12 CB01 CC02 DA02 DA04 DC02 DC05 5H007 AA02 BB06 CA01 CB04 CB05 CC12 CC23 DA05 DA06 DB01 DB12 DC02 DC05 EA01 EA02

Claims (3)

[Claims] An AC power supply is converted into a DC voltage by a rectifier, the DC voltage is supplied to an inverter as a predetermined DC voltage by an active filter, and the AC power is applied to the motor of the compressor as an arbitrary AC voltage by the inverter. When operating the motor, a method of controlling a compressor that performs a PWM control and a PAM control for driving the motor while driving the switching means of the active filter in a predetermined manner so that at least the input AC current waveform has a sine wave shape. When the motor is stopped or PWM
During control, the output DC voltage of the active filter is detected, the set output DC voltage of the active filter is made lower than the output DC voltage, the input AC current or the secondary current is detected, and the detected input AC current is detected. Alternatively, the output DC voltage set in accordance with the secondary current is varied in a range lower than the output DC voltage, and the switching means of the active filter is stopped at least near the peak of the input AC current waveform. A compressor control method characterized by the above-mentioned. 2. The method according to claim 1, wherein the set output DC voltage is larger when the input AC current or the secondary current is larger than a predetermined value than when the input AC current or the secondary current detected every predetermined time is equal to or smaller than a predetermined value. The method of controlling a compressor according to claim 1, wherein the pressure is increased. 3. A predetermined time for detecting the input AC current or the secondary current is detected for each cycle of the input AC power supply, and as the input AC current or the secondary current increases, the set output DC voltage increases. The method for controlling a compressor according to claim 1, wherein the control is performed.