JPH07113475B2 - Air conditioner operation control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an operation control method for an air conditioner, and more specifically, an operation for preventing an operating current of a compressor from exceeding a maximum allowable current value. Regarding control method.

[Conventional technology]

Electric power to the compressor that constitutes the refrigeration cycle of the air conditioner is supplied through a frequency conversion device provided between the compressor and a commercial power source.

This frequency conversion device includes a converter unit that converts a commercial power supply voltage into a DC voltage doubler, an inverter unit that converts a DC voltage doubled from the converter unit into three-phase AC power and supplies the AC power to the compressor, and the inverter unit. It is configured by a control unit or the like for controlling the unit, and the control unit receives operation command information from the indoor unit and information from the outdoor air temperature detection device and the operation current detection device provided in the outdoor unit, and The inverter unit is controlled by the operating frequency determined based on these pieces of information.

By the way, since the operating current of the compressor increases with an increase in load and may exceed the rated current of the air conditioner, the range of the current value supplied from the commercial power source to the compressor via the frequency conversion device. Is divided into a plurality of current control zones as shown in FIG. 4, and when the current value detected by the operating current detection device reaches a high zone of the current control zones, the output frequency of the frequency conversion device is set to a predetermined time. The operating current is reduced by lowering each by a predetermined value, and when the current value detected by the operating current detection device reaches the intermediate zone of the current control zone, the output frequency of the frequency conversion device does not change,
When the current value detected by the operating current detection device further decreases and reaches the low zone of the current control zone, the output frequency of the frequency conversion device is increased by a predetermined value at predetermined time intervals, It is controlled so as to approach the operating frequency determined by the operating command information of the above.

[Problems to be Solved by the Invention]

However, in the case of operation control as described above, when the current value detected by the operation current detection device reaches the high zone of the current control zone, the output frequency of the frequency conversion device is lowered,
The operating current value returns to the middle zone, but if the operating load increases rapidly due to a large load during operation, this operating current does not drop immediately because the output frequency of the frequency converter is lowered. Instead, as shown in FIG. 4, it goes over the upper limit value of the intermediate zone, enters the high zone of the current control zone, and then descends.

The occurrence of such an overshoot increases the amplitude (zone width) of the operating current, destabilizes the air conditioning capacity, and the operating current exceeding the upper limit causes the electric components and the frequency converter to be configured. This is not preferable because the allowable current value is exceeded for the compressor as well.

Therefore, in the present invention, the above problems are solved,
An object of the present invention is to provide an operation control method for an air conditioner that enables stable operation without the operating current value of the compressor exceeding the upper limit value of the current control zone.

[Means for Solving the Problems]

The present invention has been made to solve the above problems, based on the operation command information from the indoor unit and the information from the outside air temperature detection device or the like provided in the outdoor unit, commercial power by the frequency conversion device. When frequency-converted and supplied to the compressor, and the operating current of the compressor detected by the operating current detection device at that time reaches the maximum allowable current value which is the upper limit value of the current control zone, the output of the frequency conversion device When the frequency is lowered to suppress the operating current from exceeding the maximum allowable current value, and when the operating current falls within the current control zone, the output frequency of the frequency converter does not change, and the operating current is When the lower limit value of the current control zone is reached, in the operation control method of the air conditioner for increasing the output frequency of the frequency conversion device, if the operating current is increasing, The degree of change of the operating current is calculated, the upper limit value of the operating current according to the degree of change is set in the current control zone, and when the rising operating current reaches this upper limit, the frequency conversion device The output frequency is decreased by a predetermined value to delay the increase of the operating current so that the maximum allowable current value is gradually approached.

[Action]

With the above control method, when the operating current is increasing, the degree of change is calculated, and the upper limit value of the operating current according to the degree of change is set in the current control zone. When the operating current that is rising reaches, the output frequency of the frequency converter is lowered by a predetermined value and the operating current rises slowly, and when the operating current rises slowly, the operating current is the upper limit value of the current control zone. The operating current does not suddenly exceed the maximum permissible current value because it gradually approaches the maximum permissible current value.When the operating current reaches the maximum permissible current value, the output frequency of the frequency converter is only a predetermined value. Since it can be lowered, the operating current also drops.

Therefore, the overshoot of the operating current can be suppressed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a block diagram showing a control system of an outdoor unit of an air conditioner, 1 is a commercial power source, 2 is a frequency conversion device for converting AC power from the commercial power source 1 into three-phase AC power, and 3 is The compressor 4 driven by the three-phase AC power output from the frequency conversion device 2 is an operating current detection device provided in the input circuit of the frequency conversion device 2 for detecting the operating current of the compressor 3, and 5 is the outside air. It is a temperature detection device.

The frequency conversion device 2 converts the AC power supplied from the commercial power source 1 into a DC voltage doubler, and the DC voltage from the converter unit 6 into a three-phase AC power to compress the compressor 3. It is composed of an inverter unit 7 for supplying to the inverter unit and a control unit 8 for driving and controlling the inverter unit 7.

This control unit 8 is an A / D converter 8a for converting an analog signal output from the operating current detecting device 4 or the outside air temperature detecting device 5 into a digital signal, information on the operating current and the outside air temperature which are A / D converted, and A microcomputer 8b that generates a PWM (pulse width modulation) waveform signal based on operation command information from an indoor unit (not shown), a drive circuit 8c that converts the PWM waveform signal from this microcomputer 8b into an inverter drive signal, etc. It is configured.

FIG. 2 is a time chart showing an example of the operation control of the present invention, where I is the operation current of the compressor 3 and f is the output frequency of the frequency conversion device 2.

Now, assuming that the maximum allowable current value (rated current) of the air conditioner is 20A, the value 18A obtained by removing the operating current 2A of the fan motor (not shown) other than the compressor 3 from this value is 18A. Is the maximum allowable current value, that is, the upper limit value Imax of the operating current of the compressor 3.

The value 16A, which is obtained by subtracting 2A from the upper limit value Imax18A, is the lower limit value Im.
Set as in and set the high zone over 18A to the A zone, 1
The intermediate zone from 8A to 16A is divided into three zones, the B zone, and the lower zone below 16A is the C zone.
The zone is the current control zone of the compressor 3.

When the compressor 3 is started, the frequency conversion device 2
The rising output frequency f is increased at a rate of 1 Hz / 0.4 seconds, for example.

As the output frequency f increases, the operating current I of the compressor 3
However, the degree of increase ΔI of the operating current I is repeatedly calculated by the microcomputer 8b at every predetermined time after the start of operation, and the temporary upper limit of the operating current I is set in the current control zone according to the calculated value. The value I'is set.

This upper limit value I'is for temporarily suppressing the rising speed of the rapidly rising operating current I and gradually approaching the upper limit value Imax. If the rising of the operating current I is steeper than the illustrated state, the upper limit value I'is set. The value I ′ is set lower, and conversely, if the rising of the operating current I is gentler than the illustrated state, the upper limit value I ′ is set to a position higher than the illustrated position.

By the way, when the operating current I detected by the operating current detecting device 2 reaches the upper limit value I ′, the frequency converting device 2
Lowers its output frequency f by, for example, 1 Hz / 0.4 seconds,
After that, the output frequency f is maintained constant and the degree of increase ΔI of the operating current I is reduced.

At this time, if the load is small, the running current I whose rise is suppressed drops toward the lower limit value Imin of the current control zone, but since the actual running has just started, the load state is Even if the output frequency f of the frequency conversion device 2 is maintained constant as shown in the figure, the operating current I continues to increase.

The degree of increase ΔI of the operating current I at this time is calculated by the microcomputer 8b as described above, and the upper limit value Imax is finally set according to the calculated value.

When the operating current I reaches the upper limit value Imax, the frequency conversion device 2 lowers its output frequency by, for example, 1 Hz / 0.4 seconds,
The operating current I is prevented from exceeding the upper limit value Imax and entering the A zone.

As described above, the output frequency f of the frequency conversion device 2 is lowered at a predetermined frequency for a predetermined time when the operating current I reaches the upper limit value Imax, but thereafter it is maintained constant as shown in the center of the figure. .

If the load becomes small during this time period, the operating current I also gradually drops and reaches the lower limit value Imin. When the operating current I reaches the lower limit value Imin, the output frequency f of the frequency conversion device 2 starts to increase, but the degree of increase ΔI of the operating current I at this time is calculated by the microcomputer 8b in the same manner as described above, Based on the calculation result, an upper limit value I ″ for setting the rising speed of the operating current I again to be gentle is set. In the operation control method of the present invention, since such control is repeatedly executed, the operating current I Does not exceed the upper limit value Imax.

FIG. 3 is a flowchart showing a series of these control operations. When the air conditioner is started in step ST1, timer 1 and timer 2 start counting (not shown), and in step ST2 It is determined whether or not the timer 1 is in the time-up state. If it is not in the time-up state, the process proceeds to step ST8, but if it is in the time-up state, the process proceeds to the next step ST3, and the timer 1 Is set.

Then, in step ST4, the rising operating current value is detected, and this operating current value is stored as the newly detected current value Ib.

In step ST5, the degree of change (increase) in the operating current I is decreased by subtracting the already detected current value Ia from the current value Ib.
Calculate I.

At step ST6, an upper limit value I'of the operating current I corresponding to the degree of change .DELTA.I of the operating current is set.

In step ST7, the previously detected current value Ib is stored as Ia, and then the process proceeds to the next step ST8.

In step ST8, it is determined whether or not timer 2 has timed out. If not, step ST8
Proceeding to 13, the normal operation is executed at the output frequency of the frequency conversion device 2 determined by the room temperature, the set temperature, etc., and the process returns to step ST2.

If it is determined in step ST8 that the timer 2 has timed out, the process proceeds to step ST9, the timer 2 is set, and the process proceeds to the next step ST10.

In step ST10, it is determined whether the operating current I exceeds the upper limit value I'of the operating current I set in step ST6,
If the upper limit value I'is exceeded, the process proceeds to step ST11 to decrease the output frequency f of the frequency conversion device 2 by, for example, 1 Hz, and in the next step ST12, the operating current I becomes 1 to the upper limit value I '.
Set the flag indicating that the number of times has been reached and set step ST2
Return to.

If the determination result in step ST10 does not exceed the upper limit value I ', the process proceeds to step ST14. Here, it is determined whether the flag set in step ST12 is in the set state or the reset state. If it is in the reset state, the process proceeds to step ST13 to execute the normal operation, and returns to step ST2.

If the flag is set in the determination in step ST14, the process proceeds to step ST15, in which the operating current detector 4
The operating current I detected at is the lower limit value Imin of the current control zone.
Is determined, and if not reached, the output frequency of the frequency conversion device 2 is maintained constant in step ST16, and the process returns to step ST2.

If it is determined in step ST15 that the operating current I has reached the lower limit value Imin of the current control zone, the process proceeds to step ST17 and the normal operation similar to step ST13 is executed, and in step ST17, in step ST12. Reset the set flag and return to step ST12.

The control method of the operating current I of the compressor 3 has been described above.
When it approaches Imax gradually and reaches the upper limit value Imax, the output frequency of the frequency conversion device 2 is lowered, so that the overshoot of the operating current I can be suppressed.

〔The invention's effect〕

If the operation control method of the air conditioner as described above is used, the operation is performed without lowering the output frequency of the frequency conversion device until the operating current of the compressor exceeds at least the lower limit value of the current control zone. The increase in capacity is not hindered, and after the operating current enters the current control zone, the increase of the operating current is gradually suppressed to reach the upper limit value of the current control zone, and the operating current reaches the upper limit value. For example, since the output frequency of the frequency converter can be lowered, the operating current does not overshoot.If the operating current drops to the lower limit value, the output frequency of the frequency converter is increased and the operating current is returned to the current control zone. Since the above control operation is repeated, electrically safe and stable air conditioning capability can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of a control system of an outdoor unit of an air conditioner showing an embodiment of the present invention, FIG. 2 is a time chart of current control of the embodiment, and FIG. 3 is control of the embodiment. The flowchart and FIG. 4 are time charts of current control showing a conventional example. In the figure, 1 ... Commercial power source, 2 ... Frequency conversion device, 3 ...
Compressor, 4 ... Operating current detector, 5 ... Outside air temperature detector, 6 ... Converter, 7 ... Inverter, 8 ...
… Control unit, 8a …… A / D converter, 8b …… Microcomputer, 8c ……
Drive circuit.

Claims (1)

[Claims] 1. A commercial power is frequency-converted by a frequency converter based on operation command information from the indoor unit and information from an outside air temperature detecting device provided in the outdoor unit and supplied to the compressor at that time. When the operating current of the compressor detected by the operating current detection device reaches the maximum allowable current value which is the upper limit value of the current control zone, the output frequency of the frequency conversion device is reduced to reduce the operating current to the maximum allowable current. Suppressing so as not to exceed the value, when the operating current drops in the current control zone, the output frequency of the frequency converter does not change, when the operating current reaches the lower limit of the current control zone, In an air conditioner operation control method for increasing the output frequency of the frequency conversion device, if the operation current is increasing, the degree of change in the operation current is calculated, and the change is calculated. The upper limit of the operating current according to the degree is set in the current control zone, and when the rising operating current reaches this upper limit, the output frequency of the frequency converter is lowered by a predetermined value to increase the operating current. The air conditioner operation control method is characterized in that: