JPH08237957A - Controller and conrol method for air-conditioner - Google Patents

Abstract

PURPOSE: To make an inverter output voltage proportional to the output frequency in the high frequency region at the time of variable speed control of the induction motor of an air-conditioner and to improve the input power factor. CONSTITUTION: In the controller for air-conditioner having an inverter circuit 4 for subjecting an induction motor driving a compressor to variable speed control, a boosting converter section 10 for converting an input AC voltage Vi into a DC voltage being fed to an inverter circuit 4 includes a booster circuit. A control circuit 11 controls the IGBT 10c at the boosting converter section 10 to increase the DC output voltage higher than Vi×(2<1/2> ) or 2×Vi×(2<1/2> ) so that the output voltage from the inverter circuit 4 will be in proportion to the output frequency. The booster circuit at the boosting converter section 10 constitutes an input power factor improving circuit of a choke coil 10b, the IGBT 10c, a diode 10d, etc., so that almost sinusoidal input AC current waveform is produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air conditioner control technique, and more particularly to an air conditioner control method and apparatus for improving compressor motor efficiency and operation control. .

[0002]

2. Description of the Related Art An air conditioner of this type includes a control device shown in FIG. 3, for example.

In FIG. 3, this air conditioner control apparatus includes a converter section 2 for converting an AC power supply 1 into a DC power supply.
And an inverter circuit 4 for converting the output DC voltage of the converter unit 2 into an AC voltage and outputting it to the induction motor 3 of the compressor.
A microcomputer 5 for outputting an inverter control signal (PWM signal) for controlling ON / OFF of a plurality of transistors of the inverter circuit 4, and a drive circuit 6 for driving the transistors of the inverter circuit 4 by the control signal. ing.

The converter section 2 is provided with a rectifier circuit 2a for rectifying the AC power supply 1 into DC, a reactor 2b, and a smoothing capacitor 2c. For example, the input AC voltage Vi (200
V) is converted into a DC voltage Vo (about 280 V), and this DC voltage Vo is output to an inverter circuit 4 in which a transistor and a feedback diode are three-phase bridge connected.

The microcomputer 5 outputs a PWM signal for controlling each transistor of the inverter circuit 4,
The inverter circuit 4 is controlled via the drive circuit 6. The PWM signal output from the microcomputer 5 switches each transistor of the inverter circuit 4,
The DC voltage Vo input to the inverter circuit 4 is converted into a three-phase AC voltage and output to the induction motor 3.

At this time, the microcomputer 5 changes the PWM signal to be output according to the frequency command and the like, and changes the output voltage Vm and the output frequency fM from the inverter circuit 4 to drive the induction motor 3 that drives the compressor. Variable speed control.

Further, in controlling the induction motor 3, generally, in order to keep the motor torque constant and to make the motor efficiency and the operation controllability good, the output voltage Vm and the output frequency fM of the inverter circuit 4 are shown in FIG. Control is performed so that Vm / fM becomes constant. Therefore, the output frequency fM
Of the output voltage Vm corresponding to the output voltage Vm is stored in advance in the internal storage means of the microcomputer 5, and the microcomputer 5 outputs the output voltage Vm corresponding to the output frequency fM.
Is read from the internal storage means to generate and output a PWM signal.

With the above control, the motor efficiency and operation controllability of the induction motor 3 are improved, and as a result, the air conditioner is operated satisfactorily.

[0009]

In the air conditioner control method, however, the output DC voltage Vo of the converter unit 2 is at most Vi × (1/2 of 2) as described above.
Since it is a square root, that is, a square root of 2 (about 280 V), the output AC voltage Vm of the inverter circuit 4 is Vo / (2
1/2 power) (about 200 V).

Therefore, as shown in FIG. 4, the output frequency fM of the inverter circuit 4 is fMa (for example, 90 Hz).
When the output voltage Vm reaches the maximum value Vmmax (2
00V) and the output frequency fM is fMa (9
In the range of 0 Hz) to fMmax (140 Hz), the output voltage Vm had to be constant at Vmmax.

That is, fMa (90 Hz) to fMm
In the range up to ax (140 Hz), the Vm / fM ratio can be set so that the motor efficiency and the operation controllability are good characteristics, that is, the ratio between Vm and fM is constant. As a result, the motor efficiency was poor and it was difficult to operate the air conditioner well.

The present invention has been made in view of the above problems, and an object thereof is a region in which the output frequency of the inverter means is high (fMa (90 Hz) to fMmax (140 Hz).
Up to)), the output voltage of the inverter means can be made proportional to the output frequency, the motor efficiency and operation controllability can be made good characteristics, and as a result, the operation of the air conditioner can be made good. An object of the present invention is to provide an air conditioner control method and an apparatus thereof.

[0013]

In order to achieve the above-mentioned object, the present invention has inverter means for variable speed control of an induction motor for driving a compressor, and converts an input AC voltage into a DC voltage. Output to the inverter means, and by controlling a plurality of switching means of the inverter means, the DC voltage is converted into an AC voltage and output to the induction motor, and the output voltage and the output frequency of the inverter means are output. A method for controlling an air conditioner that variably controls the induction motor at a variable speed, wherein when converting the input AC voltage to a DC voltage, the converted DC voltage is boosted, and at least the output frequency of the inverter means is high. It is characterized in that the ratio of the output voltage of the inverter means to the output frequency of the inverter means is made constant in the region.

The present invention further comprises inverter means for variable speed control of the induction motor driving the compressor,
The input AC voltage is converted into a DC voltage and output to the inverter means, and by controlling a plurality of switching means of the inverter means, the DC voltage is converted into an AC voltage and output to the induction motor, and A control device for an air conditioner in which an output voltage and an output frequency of an inverter means are varied to control the induction motor at a variable speed, and a booster circuit is provided in a converter means for converting the input AC voltage Vi into a DC voltage. , The output DC voltage is Vi × (2 1/2 power) or 2 × Vi × by the booster circuit.
The output voltage of the inverter means is proportional to the output frequency of the inverter means at least in a region where the output AC voltage of the inverter means is larger than Vi or 2 × Vi. It is characterized by that.

In this case, it is preferable that the booster circuit of the converter means is composed of at least a choke coil, a switching means and a diode, and has a function of a power factor correction circuit for making an input AC current waveform substantially a sine wave.

[0016]

Since the above means is adopted, when the input AC voltage Vi of the air conditioner is converted into a DC voltage, the output DC voltage of the converter means becomes Vi × by the booster circuit of the converter means.
(2 to the power of 1/2, in other words the square root of 2) or 2
It is made larger than × Vi × (2 to the power of 1/2) and output to the inverter means.

As a result, the maximum value of the AC voltage output from the inverter means to the induction motor is increased, and the output AC voltage of the inverter means becomes the input AC voltage Vi or 2
In the range larger than × Vi, that is, in the region where the output frequency of the inverter means is high, the ratio between the output voltage of the inverter means and the output frequency of the inverter means is made constant.

Further, since the booster circuit of the converter means has at least the function of the input rate improving circuit including the choke coil, the switching means and the diode,
The input AC current waveform is almost sinusoidal, and the input power factor is improved.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, by increasing the output voltage of the inverter means (voltage applied to the induction motor) by boosting the DC voltage output to the inverter means for variable speed control of the induction motor of the air conditioner, the inverter means is provided. It is noted that it is possible to make the output voltage of the inverter means proportional to the output frequency of the inverter means in a region where the output frequency is high.

Therefore, the control device to which this air conditioner control method is applied has the configuration shown in FIG. In addition,
In the figure, the same parts as those in FIG.

In FIG. 1, this control device is provided with a boost converter section 10 instead of the converter section 2 shown in FIG. 3, a control circuit 11 for controlling the boost converter section 10, and other functions of 5 shown in FIG. And at least the inverter circuit 4
And a microcomputer 12 for controlling the output voltage VM / output frequency fM ratio of the inverter circuit 4 to be constant in a region where the output frequency is high.

The boost converter section 10 includes a rectifying circuit 10a.
, The choke coil 10b, and the switching element IG
BT (insulated gate transistor) 10c, reverse blocking diode (FRD) 10d, smoothing capacitor 10e
And a resistor circuit 10f for detecting the boosted voltage
A current detection resistor 10g and a resistor circuit 10h for detecting the output of the rectifier circuit 10a.

The control circuit 11 is composed of, for example, a power factor improving IC, and detects the output voltage Voo of the boost converter unit 10 and the output voltage of the rectifier circuit 10a by the resistance circuits 10f and 10h to generate a command signal of a current waveform. Meanwhile, a PWM signal for controlling the IGBT 10c is created and output based on the current waveform detected by the current detection resistor 10g and its command signal.

Next, the operation of the control device having the above-mentioned configuration will be described with reference to the graph of FIG. 2. First, the rectifier circuit 10a of the boost converter section 10 rectifies the input AC voltage Vi into a DC voltage and rectifies the DC voltage. The boosted DC voltage is boosted to a DC voltage Voo by the booster circuit. The control circuit 11 controls the IGBT 10 so that the output voltage Voo of the boost converter unit 10 becomes larger than Vi × (2 to the power of 1/2, in other words, the square root of 2).
For example, when the input AC voltage Vi = 200V, the output DC voltage Voo is converted to 350V by controlling c.

Further, the control circuit 11 is a boost converter unit 1.
The output voltage Voo of 0 is boosted to 350 V, while the IGBT 10c is controlled so that the input AC current waveform becomes a substantially sine wave.

The boost converter unit 10 outputs the output DC voltage Vo.
While outputting o to the inverter circuit 4, the microcomputer 12 controls the transistor of the inverter circuit 4 and outputs the boosted output DC voltage Voo to the output voltage Voo.
M, the output frequency fM is converted to a three-phase alternating current and the induction motor 3
Output to.

At this time, the microcomputer 12 stores the VM / fM pattern shown in FIG. 2 in the internal memory (built-in R
OM), and controls the transistors of the inverter circuit 4 according to this pattern.

For example, when the output DC voltage Voo of the boost converter unit 10 is boosted to 350V, the maximum output voltage VM of the inverter circuit 4 is VMmax = Voo /
(2 to the power of 1/2) (about 250V). This allows
When the induction motor 3 is controlled at a constant VM / fM ratio, the output frequency fM is the frequency fMa (90 Hz) to fMmax.
In the range of (140 Hz), the output voltage VM (voltage applied to the induction motor 3) of the inverter circuit 4 is set to VMa (20
It can be varied from 0V) to VMmax (250V).

Therefore, the output AC voltage VM of the inverter circuit 4 (the voltage applied to the induction motor 3) is the input AC voltage V.
In a region larger than i (range between VMa and VMmax), the output voltage VM can be made proportional to the output frequency fM, that is, the ratio VM / fM can be made constant (see FIG. 2).

As is apparent from FIG. 2, in the range where the output voltage VM of the inverter circuit 4 is VMa (200 V) or less, the control for keeping the VM / fM ratio constant is performed as in the conventional case.

Further, when the control circuit 11 controls the IGBT 10c of the boost converter section 10, the output DC voltage Voo is boosted and the input AC current waveform is controlled to be a substantially sine wave to improve the input power factor. be able to.

As described above, since the boost converter unit 10 has both the boost circuit and the power factor correction circuit, it is in the high frequency region (fMa to f shown in FIG. 2).
Even in the range (Mmax), the VM / fM ratio can be kept constant, and the input power factor can be improved.

In the above embodiment, the input AC voltage Vi is
Is described as being 200V, but this is an example. For example, when the input AC voltage Vi is 100V, 2 × Vi is conventionally used by using a voltage doubler rectifying and smoothing circuit.
It is set to x (1/2 power of 2) (about 280V). Even in this case, the present invention can be applied, and the output voltage Voo in the boost converter unit 10 is 2 × Vi ×.
The same control as described above can be performed by boosting the voltage higher than (2 to the power of 1/2).

[0034]

As described above, according to the present invention, in an air conditioner control method and apparatus having inverter means for variable speed control of an induction motor for driving a compressor, an input AC voltage Vi is a DC voltage. The converter means for converting to and outputting to the inverter means has a booster circuit,
The booster circuit greatly boosts the output AC voltage of the converter means so that the output voltage of the inverter means is proportional to the output frequency of the inverter means at least in a region where the output AC voltage of the inverter means is larger than Vi or 2 × Vi. Therefore, the output voltage of the inverter means can be made proportional to the output frequency also in the high range of the output frequency of the inverter means (the range from fMa (90 Hz) to fMmax (140 Hz) shown in FIG. 2), and the motor efficiency and The operation controllability can be made good, and as a result, the operation of the air conditioner can be made good.

Further, since the booster circuit is composed of at least a choke coil, a switching means and a diode and has a function of a power factor improving circuit for making an input AC voltage a sine wave, the input power factor is improved. The effect is that it can be achieved.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a control device to which an air conditioner control method according to an embodiment of the present invention is applied.

FIG. 2 is a schematic graph illustrating the operation of the control device shown in FIG.

FIG. 3 is a schematic block diagram of a control device for a conventional air conditioner.

4 is a schematic graph illustrating the operation of the control device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 3 Induction motor 4 Inverter circuit (inverter means) 5,12 Microcomputer 10 Boost converter section (converter means) 10a Rectifier circuit 10b Choke coil (reactor) 10c IGBT (insulated gate transistor) 10d Reverse blocking diode (FRD) 10e Smoothing capacitor 10f, 10h Resistor circuit 10g Current detection resistor 11 Control circuit

Claims (3)

[Claims] 1. An inverter means for variable speed control of an induction motor for driving a compressor, which converts an input AC voltage into a DC voltage and outputs the DC voltage to the inverter means, and a plurality of switching operations of the inverter means. Control of the air conditioner for converting the DC voltage into an AC voltage and outputting it to the induction motor by controlling the means, and varying the output voltage and the output frequency of the inverter means to control the induction motor at a variable speed. A method, wherein when converting the input AC voltage into a DC voltage, the converted DC voltage is boosted, and the output voltage of the inverter means and the output frequency of the inverter means are at least in a region where the output frequency of the inverter means is high. A method for controlling an air conditioner, characterized in that the ratio of the air conditioners is made constant. 2. Inverter means for variable speed control of an induction motor for driving a compressor, wherein an input AC voltage is converted into a DC voltage for output to the inverter means, and a plurality of switching operations of the inverter means. Control of the air conditioner for converting the DC voltage into an AC voltage and outputting it to the induction motor by controlling the means, and varying the output voltage and the output frequency of the inverter means to control the induction motor at a variable speed. In the apparatus, a converter circuit for converting the input AC voltage Vi into a DC voltage has a booster circuit, and the booster circuit outputs the output DC voltage as Vi × (2 1/2 power) or 2 × Vi × (2 ½ power), and at least in the region where the output AC voltage of the inverter means is larger than Vi or 2 × Vi, the output of the inverter means is increased. A control device for an air conditioner, wherein the input voltage is proportional to the output frequency of the inverter means. 3. The air according to claim 2, wherein the booster circuit of the converter means comprises at least a choke coil, a switching means, and a diode, and has a function of a power factor correction circuit for making an input AC current waveform a substantially sine wave. Harmonic controller.