JP2891343B2 - Control method of air conditioner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for an air conditioner, and more particularly to a means for improving a power factor of the air conditioner and reducing a harmonic current.

[0002]

2. Description of the Related Art An air conditioner generally uses a power supply circuit of a capacitor input type. However, since an input current is distorted, a power factor is reduced and a harmonic current is generated. Therefore, in order to improve these, for example, as shown in FIG. 4, a power source 21 and at least a reactor 22 and a switching element 23 which constitute a closed circuit are provided.
Is controlled in a predetermined switching pattern such that the input current waveform is substantially a sine wave to improve the power factor and reduce harmonics. The illustrated input current detection circuit 24 is for operating the air conditioner within a range where the input current does not exceed the rating of the power supply 21, and the zero-cross detection circuit 25 is for determining the frequency of the power supply 21 and for controlling the microcomputer.
26 are used to determine the timing of interrupt processing, the timing of signal transmission / reception between the indoor unit and the outdoor unit, and the like, all of which are general existing circuits of an air conditioner. In the figure, reference numeral 27 denotes a compressor motor.

[0003]

However, when the switching element 23 is controlled in a predetermined switching pattern as shown in FIG. 5A using the above-mentioned power supply circuit, as shown in FIG. Although the current waveform is substantially a sine wave, even when controlled by the same switching pattern (a), when used with a power supply different from that of (b), a distorted current as shown in (c) due to the influence of power supply impedance and the like. In some cases, a waveform is formed, the power factor is reduced, and the harmonic current cannot be reduced. Accordingly, an object of the present invention is to provide a method of controlling an air conditioner in which a power factor does not decrease and a harmonic current does not increase even if a different power supply is used.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and is an air conditioner having an inverter device, which comprises an input AC power supply, at least a reactor constituting a closed circuit, and a switching element. The switching element is switched in a predetermined switching pattern so that the input current becomes a substantially sine wave having substantially the same phase as the input voltage, and the input current and the instantaneous value of the input current waveform are detected. The reference value of the instantaneous value corresponding to the current is read from a storage unit that stores the current value in advance, and the reference value is compared with the detected instantaneous value. The predetermined switching pattern is switched so that the instantaneous value becomes equal to the reference value. We decided to increase, maintain, and decrease the duty cycle on-time.

[0005]

According to the above control method, the input current and the instantaneous value of the input current waveform are detected, and the instantaneous value is compared with a reference value of the instantaneous value corresponding to the input current. Since the switching of the switching element is controlled by the switching signal obtained by increasing or decreasing the ON time of the switching signal of the (active filter), the input current waveform can be made substantially a sine wave having substantially the same phase as the input voltage.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, the air conditioner has a converter circuit 2 for converting an input AC power supply 1 into a DC.
And an inverter circuit 3 to which a direct current from the converter circuit 2 is supplied, and a power supply provided in the converter circuit 2 to improve the input power factor and reduce harmonics (reactor (choke coil) ) 4 and a switching element (IGBT) 5, an input current control circuit including a reverse blocking diode 6, a compressor motor 7 driven by the inverter circuit 3, and an input current sensor (CT) 8. An input current instantaneous value detection circuit 9 for detecting an instantaneous value of a current, and a zero cross detection circuit for detecting an AC zero cross.
10 and a drive circuit 11 for driving the switching element 5
And a drive circuit 12 for driving the inverter circuit 3 and a microcomputer (hereinafter referred to as a microcomputer) 13 for controlling the drive circuit 12. The converter circuit 2 includes a rectifier circuit 2a and a smoothing capacitor 2b.

The air conditioner has a zero-cross detection circuit 10 for detecting an input AC zero-cross point for discriminating an input frequency, interrupt processing, and the like, and a microcomputer 13 includes an A / D converter, a timer, and the like. , A storage unit, etc., are utilized in the present invention, and the switching element 5 is switched in a predetermined switching pattern so that the input current becomes a substantially sine wave having substantially the same phase as the input voltage, and the input signal is input. Detects current and instantaneous value of input current waveform,
The reference value of the instantaneous value according to the input current is read from a storage unit that stores the current value in advance, and the reference value is compared with the detected instantaneous value, and the predetermined value is set so that the instantaneous value becomes equal to the reference value. The on-time of the duty cycle of the switching pattern is increased, maintained, and reduced.

For example, when a switching pattern as shown in FIG. 2A is output from the microcomputer 13 to the drive circuit 11 to control the switching of the switching element 5, the input current waveform at this time becomes as shown in FIG. As shown,
The output of the input current instantaneous value detection circuit 9 is as shown by a solid line in FIG. The output of the input current instantaneous value detection circuit 9 is input to the microcomputer 13.
Is t for each zero cross detected by the zero cross detection circuit 10.
The instantaneous value I at the timing of 0, t1, t2,.
A, D, 0, I1, I2,... I10 are A / D converted and detected, and these instantaneous values I0, I1, I2,.
Is stored in the storage unit inside the microcomputer 13. Thereafter, that is, after time t10, the microcomputer 13 stores the stored instantaneous values I0 and I0.
, I2,..., I10 are calculated and detected. The detection of the input current is not necessarily limited to this method, but may be detected by a conventional input current detection circuit 24 as shown in FIG.

By the way, as shown in FIG. 3, as many input currents 2A, 3A as necessary are stored in the storage unit of the microcomputer 13.
A,... Instantaneous values I0, I1, I2,.
-The reference value of I10 is stored in advance. Therefore, for example, the input current shown in FIG.
, The reference value data I03A, I13A, I23A,... Stored from the address I3A of the storage unit of the microcomputer 13
..Reading I103A, instantaneous value I0 and reference value data I0
3A, the instantaneous values I0 to I10 and the reference value data I03A to I10, such as the instantaneous value I1 and the reference value data I13A.
Compare with 3A. The broken line shown in FIG. 2C is a reference value when the input current is 3 A.

As a result of the comparison, if the instantaneous value is larger than the reference value, that is, the instantaneous values I4 and I4 shown in FIG.
5, I6 exceeds the reference value indicated by the broken line, the duty cycle on-time data D4, D5, of the switching signal corresponding to these instantaneous values I4, I5, I6.
D6 is decreased, and the instantaneous values I4, I5, I6 are decreased. Also, t1, t2, t whose instantaneous value is smaller than the reference value.
3, t7, t8, and t9, the on-time data D1, D2, D3 of the duty cycle of the switching signal
D7, D8 and D9 are increased, and the instantaneous values I1, I2 and I
3, I7, I8, and I9 are increased. Further, D10 is maintained for t0 and t10 in which the instantaneous value and the reference value are equal.
As described above, when the ON time of the switching duty is adjusted, a switching pattern as shown in FIG. 2D is obtained. When the switching element 5 is driven, the instantaneous value becomes a reference value as shown in FIG. As shown in FIG. 2F, the input current waveform is substantially a sine wave.

[0011]

According to the air conditioner controlled by the control method as described above, the input current waveform is not distorted due to the influence of the power source impedance and the like, and is always high regardless of the power source used. Harmonic current can be suppressed at the power factor.

[Brief description of the drawings]

FIG. 1 is a main part circuit block diagram of an air conditioner showing one embodiment of the present invention.

FIG. 2 is a schematic waveform diagram for explaining one embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between timing of switching control according to the present invention and reference value data thereof.

FIG. 4 is a main part circuit block diagram of an air conditioner showing a conventional example.

FIG. 5 is a schematic waveform diagram when switching control is performed by a conventional control method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input AC power supply 2 Converter circuit (AC / DC conversion circuit) 3 Inverter circuit 5 Switching element (IGBT) 7 Compressor motor 9 Input current instantaneous value detection circuit 10 Zero cross detection circuit 11 Drive circuit 12 Drive circuit 13 Microcomputer

Claims (1)

(57) [Claims] 1. An air conditioner having an inverter device,
An input AC power supply and at least a reactor constituting a closed circuit and a switching element, wherein the switching element is switched in a predetermined switching pattern so that an input current becomes a substantially sine wave having substantially the same phase as the input voltage, and The current and the instantaneous value of the input current waveform are detected, the reference value of the instantaneous value corresponding to the input current is read out from a storage unit stored in advance, and the reference value is compared with the detected instantaneous value. A method for controlling an air conditioner, comprising increasing, maintaining, and decreasing an on-time of a duty cycle of the predetermined switching pattern so that a value becomes equal to a reference value.