JP2629664B2 - 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 of an air conditioner for improving an input power factor of an air conditioner and reducing harmonics.

[0002]

2. Description of the Related Art Conventionally, in this type of air conditioner,
The AC power is converted to DC, and this DC is supplied to the inverter section, and a microcomputer generates a PWM waveform for inverter control of the compressor.
The inverter section is controlled according to the M waveform. By the way, a power supply circuit for converting an AC power supply to a DC power supply is generally of a capacitor input type. However, such a power supply circuit has a poor input power factor because the input current is distorted, and also has a disadvantage in reducing the harmonic current. Occur. Therefore, in order to improve the input power factor and reduce harmonics, for example, as shown in FIG. 6, an AC / DC conversion circuit 21, that is, a power supply and a closed circuit are configured between an AC power supply 22 and an inverter unit 23. Reactor
An input current control circuit including a switching element 24 and a switching element 25 is provided, and the switching element 25 is turned on and off at a high speed so that the input current waveform becomes a substantially sine wave. However, when the switching element 25 is turned on,
The current flows through the switching element 25, so that a loss occurs, and the conversion efficiency of the AC / DC conversion circuit 21 deteriorates.
In order to minimize this loss, a DC current sensor 26 for detecting an input current, an instantaneous value conversion circuit 27 for obtaining an instantaneous value of the detected current, an average value conversion circuit 28 for obtaining an average value of this instantaneous current, A comparator 29 and the like for comparing the average value with the instantaneous value are provided. When the instantaneous value of the input current exceeds the average value, on / off of the switching element 25 is controlled to stop.

[0003]

However, in the control method described above, the DC current sensor 26, the instantaneous value conversion circuit 27, the average value conversion circuit 28, and the like shown in FIG. Comparator 29, output current sensor
30, the average value conversion circuit 31, the switching current sensor 32, the comparator 33, and the oscillation circuit 34 are required, the number of parts is large, the number of assembly steps is increased, the cost is increased, and the reliability is reduced. There was a point. Therefore, in the present invention, by solving the above-mentioned problems, at a low cost,
It is an object of the present invention to provide a method of controlling an air conditioner that can improve an input power factor, reduce harmonics, and reduce deterioration of conversion efficiency of AC / DC conversion.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an inverter unit for converting an AC power supply to DC by AC / DC conversion means and controlling an inverter of a compressor. In the air conditioner, the AC / DC converter is provided with at least a reactor and a switching element constituting a closed circuit with the AC power supply, a timer device, and an input AC set in the timer device. A memory device that stores a plurality of time data groups for a predetermined period from the zero cross point is provided, and the switching element is switched by an on / off signal for a predetermined period from the zero cross point of the input AC manufactured by the timer device, The time data set in the above timer device is stored in memory according to the input AC power supply frequency and input current. And to select from among a plurality of time data group location. In addition, the zero-cross point, input power frequency, input current detection, etc. necessary for the above control share the existing circuit of the air conditioner, and the memory device and the timer device are also in the existing control microcomputer of the air conditioner. Decided to use.

[0005]

With the above arrangement, the switching element of the AC / DC converter is switched from the zero-cross point of the input AC in a switching pattern for one cycle (360 degrees) of the input AC, and the switching pattern is set in advance. The switching pattern is selected from among a plurality of switching patterns according to the input power supply frequency, the input current value, etc., so that when the input current of the air conditioner increases, that is, when the load increases, the switching element increases. Current flows to supply a large amount of current to the load. Also, when the input current decreases, that is, when the load decreases, the current flowing through the switching element decreases. Therefore, AC /
The output voltage of the DC converter can be stabilized, and the input power factor can be further increased. Moreover, the detection of the AC input current and the detection of the zero-cross point can be detected by the input current sensor of the existing overcurrent protection means of the air conditioner and the input AC zero-cross detection means for determining the input frequency and interrupt processing. it can.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the air conditioner, as shown in FIG.
An AC / DC conversion circuit 2 for converting an AC power supply 1 to DC;
An inverter unit 3 to which DC from the AC / DC conversion circuit 2 is supplied, and a power supply and a closed circuit provided in the AC / DC conversion circuit 2 for improving the input power factor and reducing harmonics. An input current control circuit including a reactor (choke coil) 4 and a switching element (IGBT) 5;
A reverse blocking diode 6; a compressor motor 7 driven by the inverter unit 3; an input current sensor (CT) 8 for detecting an input current; an input current conversion circuit 9 for obtaining the detected input current; , A driver circuit 11 for driving the switching element 5, a driver circuit 12 for driving the inverter unit 3, and a switching element for one AC cycle, for example, according to the detected input current. A control device (microcomputer) 13 for obtaining a switching pattern of No. 5 and controlling the switching element 5 to be turned on / off by the switching pattern.

The AC / DC conversion circuit 2 includes a rectifier circuit 2a for rectifying AC to DC and a capacitor 2b for smoothing the DC, in addition to the reactor 4 and the switching element 5. Further, the control device 13 generates a PWM waveform corresponding to a desired number of rotations of the compressor motor 7, performs an inverter control on the compressor motor 7 based on the PWM waveform, and generates a PWM waveform based on the input current detected by the input current sensor 8. Thus, the inverter section 3 is controlled so that the overcurrent protection function is activated and, for example, when the overcurrent occurs, the rotation speed of the compressor motor 7 is reduced.

The air conditioner has an input current sensor 8 for detecting an input current as described above, and a zero-cross detection circuit 10 for detecting a zero-cross point of an input AC for discrimination of an input frequency and interruption processing. Since the microcomputer of the control device 13 incorporates the timers T1 and T2 and a memory device, the present invention utilizes these components to make the input frequency and the input current as shown in FIGS. 2A and 2B. The switching element 5 is controlled to be turned on and off with a switching pattern corresponding to the switching pattern. The timer T1 is a timer for the switching cycle, and the timer T2 is a timer for the on-time of the switching. Further, the microcomputer detects the zero-cross point and the power supply frequency based on the signal from the zero-cross detection circuit 10, and A / D converts the input current obtained by the input current conversion circuit 9 in the microcomputer. ing.

In the switching pattern shown in FIG. 2, one cycle (360 degrees) starts from zero crossing (0 degree) of the input AC.
) Is divided into 20 using the internal timer T1 of the microcomputer.
msec, and the switching time data (ON time value data) TD is changed every 1 msec. The time data TD of this switching pattern is, as shown in FIG. Four types (TD1, TD2, TD3,
TD4) is prepared and stored in the memory of the microcomputer in advance. TD1 in FIG. 3 is time data when the input power supply frequency is 50 Hz and the input current is 3 A or less, and TD2 is the input power supply frequency 50 Hz and the input current 3 A.
The time data in the above case, TD3 is the input power frequency 6
Time data at 0 Hz and input current of 3 A or less, TD
4 is time data when the input power frequency is 60 Hz and the input current is 3 A or more, TD50 is time data for one cycle (t1 shown in FIG. 2) when the input power frequency is 50 Hz, and TD60 is switching time when the input power frequency is 60 Hz. This is time data for a cycle.

Hereinafter, the control method of the present invention will be described with reference to the flowchart shown in FIG. First, when a zero-cross point of the input AC is detected in step ST1, the process proceeds to step ST2, where the power supply frequency is determined.
If z, the process proceeds to step ST3, where the input current value is determined. If the input current value is 3A or less, the process proceeds to step ST4, and the start address of the time data TD1 in FIG. 3 is set. If the input current value is 3A or more, the process proceeds to step ST5. The start address of the time data TD2 in FIG. 3 is set. When the start address of either the time data TD1 or TD2 is set as described above, the process proceeds to step ST6, and the time data TD50 is set in the timer T1.

If the result of the determination in step ST2 is 60 Hz, the process proceeds to step ST7, and the input current value is determined in the same manner as in step ST3. If the input current value is 3 A or less, step ST
8, the start address of the time data TD3 in FIG. 3 is set. If the input current value is 3 A or more, the process proceeds to step ST9, where the start address of the time data TD4 in FIG. 3 is set. . When the start address of either time data TD3 or TD4 is set in this way, the process proceeds to step ST10, and time data TD60 is set in timer T1.

Thereafter, in step ST11, the time data of the set address is set in the timer T2, and in the next step ST12, the timers T1 and T2 are started.
Proceeding to step ST13, the switching output is set to the H level. This H-level signal does not change until the timer T2 expires in step ST14. When the timer T2 expires, the process proceeds to step ST15, the switching output is set to the L level, and the process proceeds to step ST16. In step ST16, the address of the previously set time data is set to +1 and the process proceeds to the next step ST17.

In this step ST17, for example, in step ST4
It is determined whether or not the work (20 times) for one cycle of the time data TD1 set in the step is completed, and if not completed, the process proceeds to step ST18. Step ST18
Then, whether the timer T1 started earlier in step ST12 has timed out, that is, (A) in FIG.
Time t1 (1 m) of one switching cycle shown in FIG.
sec) has elapsed, and if it is determined that the time is up, the process returns to step ST11 and returns to step ST11.
The processing from 11 to step ST18 is repeated.

If step ST17, step ST
If it is determined that the process based on the address set in 16 has been completed, the process proceeds to step ST19, and the switching control for one cycle of the input AC is completed. Thereafter, the process returns to step ST1 again, and when the zero crossing of the input AC is detected by the zero crossing detection circuit 10, the series of processes described above is repeatedly executed. As described above, the control method of the switching element 5 has been described. With such control, the current waveform can be made closer to a sine wave, so that the power factor is improved and the harmonics are further reduced.

It is best to perform such control for each switching cycle, but the switching element 5 is turned on and off at a high speed, for example, at 20 to 100 kHz. Requires high-speed processing. However, the microcomputer of the existing air conditioner must simultaneously process the control of the switching element 5 and the control of the inverter, for example. However, the performance of the current microcomputer of the air conditioner is insufficient, and to perform a number of controls at the same time, the microcomputer must have higher performance or a hardware circuit must be added. However, higher performance microcomputers and additional hardware circuits lead to higher costs. Therefore, if the predetermined time is longer than one switching cycle, for example, every 1 msec, the existing microcomputer can sufficiently cope with it, the input current waveform becomes substantially a sine wave, and there is no problem in performance.

FIG. 5 is a main part circuit block diagram of an air conditioner illustrating a modification of the above embodiment. That is, in the case of the above embodiment, AC 200 V (50 / 60H
z) is used, but in the case of this modified example, AC 100 V (50/60 Hz) is used for the AC power supply 1. In the drawing, the same parts as those in FIG. 1 and the parts corresponding thereto are denoted by the same reference numerals, and redundant description will be omitted. In the figure, reference numeral 2c denotes a rectifier circuit for rectifying the voltage of 100 V of the AC power supply 1 to DC, and reference numerals 5a and 5b denote switching elements (IGs) having the same function as the switching element 5 of the above embodiment.
BT). Therefore, the same effect as in the above embodiment can be obtained. In the first embodiment, the switching pattern is set for each cycle of the input AC. However, the present invention is not limited to this. The zero cross (180 degrees) half a cycle after the zero cross (0 degree) of the input AC is used. Every time)
May be repeated until. In the above embodiment, one cycle of switching is set to 1 msec for convenience of explanation. However, the present invention is not limited to this.
Or 0.2 msec.

[0017]

According to the air conditioner control method as described above, the number of parts is greatly reduced by using the existing parts of the air conditioner and its circuit, and the number of assembly steps is accordingly reduced. , The cost can be reduced, and the input power factor can be improved and the harmonics can be reduced while significantly improving the reliability.

[Brief description of the drawings]

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

FIG. 2 is a schematic waveform diagram for explaining a control method of the air conditioner of the present invention.

FIG. 3 is a time data table of a switching pattern used for control of the present invention.

FIG. 4 is a flowchart illustrating an example of a control method according to the present invention.

FIG. 5 is a main part circuit block diagram of an air conditioner showing a second embodiment of the present invention.

FIG. 6 is a main part circuit block diagram of an air conditioner showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 AC / DC conversion circuit 2a Rectifier circuit 2b Capacitor 2c Rectifier circuit 3 Inverter part 4 Reactor (choke coil) 5 Switching element (IGBT) 5a Switching element (IGBT) 5b Switching element (IGBT) 6 Reverse blocking diode 7 Compression Motor 8 Input current sensor (CT) 9 Input current conversion circuit 10 Zero cross detection circuit 13 Controller (microcomputer)

Claims (5)

(57) [Claims] 1. An air conditioner wherein an AC power supply is converted to DC by AC / DC conversion means and supplied to an inverter unit for controlling the compressor by inverter.
The AC / DC converter is provided with at least a reactor and a switching element constituting a closed circuit with the AC power supply, and a timer device and a time data group for a predetermined period from a zero-cross point of the input AC set in the timer device. A plurality of memory devices are provided, and the switching element is switched by an ON / OFF signal for a predetermined period from a zero-cross point of the input AC produced by the timer device, and a time data group set in the timer device is the input AC. A method for controlling an air conditioner, comprising selecting from a plurality of time data groups of a memory device according to a power supply frequency and an input current. 2. The method according to claim 1, wherein the timer device is an internal timer of a microcomputer for controlling the air conditioner. 3. The method according to claim 1, wherein the memory device is an internal memory of a microcomputer for controlling the air conditioner. 4. The control method for an air conditioner according to claim 1, wherein the detection of the zero cross point of the input AC is performed by using a zero cross detection means used for determining a power supply frequency of the air conditioner or interrupting power supply. 5. The control method for an air conditioner according to claim 1, wherein the detection of the input current shares input current detection means for overcurrent protection of the air conditioner.