JP2564981B2 - Air conditioner control method - Google Patents

Description

The present invention relates to a method for controlling an air conditioner, which detects an input current and performs current control so that the detected current value does not exceed a maximum allowable range of a rated power supply. More specifically, the present invention relates to a control method for an air conditioner that improves the followability and stability of current control and improves the air conditioning capability.

"Prior art" Conventionally, in this type of air conditioner control method, in order to prevent the input current from a commercial power source (eg 100V, 50 / 60Hz) from exceeding the rated current (eg 15A), the input current When the detected current exceeds the operating value of current control (eg 14 A), the operating frequency of the compressor is lowered by a specified value (eg 1 Hz) every specified time (eg 1 second), and When returning, current control is performed to fix the operating frequency.

Further, when the detected current becomes lower than the release value (for example, 13 A), the current control is released, the compressor is returned to the normal operation, and the input current does not exceed the rating. That is,
Most household electrical installations have a usage rating of 15 A or less, and air conditioners have a large input current compared to other home appliances.For example, when the outside air temperature is extremely high during cooling, or when heating. This is because a large current sometimes flows when the load is high, such as when the outside air temperature is very low.

The control method of the air conditioner will be described in detail with reference to FIG. 4. It is assumed that the input current from the commercial power supply rises due to some cause and becomes an operation value (for example, 14 A) or more (in the same figure). Shown at time t ₁ or t ₄ ). Then, in order to prevent the input current from further increasing, the operating frequency of the compressor is decreased by a predetermined value (for example, 1 Hz) every predetermined time (for example, 1 second) until the detected current returns to the operating value (for example, 14 A). . Then, as shown at time t _{2 in} FIG.
When the detected current falls below the operating value at the time of decrease, the operating frequency of the compressor is fixed at the frequency decreased by 5 Hz. Thereafter, as shown in t ₃ time points in the figure, when the detected current becomes the release value (e.g. 13A) or less, the current control is released, the compressor is normally operated, i.e. the target operating frequency . By the way, the detection current is to be released to the current control (t ₂ time shown in the figure) when returning to operating values, 1A hysteresis between release value and operating values for hunting prevention Have.

Since the current flowing through the compressor is suppressed as the operating frequency of the compressor is reduced in this way, the input current is reduced. Then, when the detected current becomes equal to or less than release values, (shown in t ₃ in FIG.), The current control is canceled.

"Problem to be Solved by the Invention" In the control method of the air conditioner, the fourth aspect
As shown in the t ₃ time points Fig until t ₄ time, when the change of the input current is slow, the detected current is more than the operation value, since the current control decreases the input current immediately actuated , The input current does not exceed the allowable value (eg 15A).

However, if the change of the input current as shown by t ₂ time from time point t ₁ in the figure is steep, the time until the input current returns to the operation value (in this case 5 seconds) it is only take However, as shown by arrow a in the figure, the allowable value (rated current
Sometimes it exceeds 15A). Therefore, since the peak current is large, the operating value may need to be set considerably lower than the allowable value so that the input current does not exceed the allowable value at the peak. In some cases, the wiring capacity could not be fully used up, and the capacity could not be fully exerted.

The present invention has been made in view of the above problems, and an object thereof is to improve followability and stability of current control for controlling an input current, and to improve air conditioning capacity. An object of the present invention is to provide a control method for such an air conditioner.

[Means for Solving the Problems] In order to achieve the above object, the present invention detects an input current when controlling an inverter of a compressor, and when the detected current exceeds an operating value of current control, the current is detected. In the control method of the air conditioner, which activates the control, lowers the operating frequency of the compressor by a predetermined value, and releases the current control when the detected current value becomes equal to or lower than the release value of the current control. The change amount of the input current is calculated, a predetermined time is obtained that is smaller as the calculated change amount is larger, and when the detected current value is equal to or more than the operation value, the operation frequency is set to the predetermined value every predetermined time. The point is that the price is lowered one by one.

[Operation] Since the above method is used, the change amount of the input current is calculated based on the detected current value before and after the predetermined time period, and further, the predetermined time period corresponding to the change amount is obtained. Further, when the detected input current value becomes equal to or higher than the current control operation value, the operating frequency of the compressor is decreased by a predetermined value every predetermined time according to the change. That is, when the change of the input current is abrupt, the operating frequency is greatly reduced in a short time by shortening the predetermined time, so that the input current can be quickly reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. In Fig. 1, the air conditioner has an AC / DC conversion circuit 2 composed of a diode bridge, a capacitor, etc., which rectifies the AC voltage of a commercial power supply (AC100V; 50 / 60Hz) 1 by doubling the voltage (about 280V), and this DC voltage. A frequency conversion circuit (inverter device) 3 for switching the variable frequency and converting it to a variable frequency three-phase alternating current by PWM, a compressor motor 4 driven by the converted variable frequency three-phase alternating current, and an input current from the commercial power supply 1. Current transformer (CT) to detect
And a current detection circuit 5 including a current exchange circuit, an indoor temperature detection device 6 including a thermistor that detects an indoor temperature, and a compressor using an indoor temperature, an indoor temperature set value (a set value by a remote controller, etc.), and the like. A control device (microcomputer) 7 is provided for outputting a switching signal having a target operating frequency of V and varying the operating frequency of the compressor with the detected current to control the current.
Further, although not shown, the control device 7 has a storage unit (eg, register I1, register I1, which temporarily stores the input current before and after a predetermined time).
I2) is provided, and it has a calculation function that calculates the change amount (ΔI / Δt) of the input current based on the contents of the registers I1 and I2 and reads the predetermined time corresponding to the calculated change amount from the table. are doing. The predetermined time may be obtained by multiplying the coefficient by a constant value by using the calculated change amount as a coefficient. Next, the operation of the control method applied to the air conditioner having the above configuration will be described with reference to the flowchart of FIG.
This will be described with reference to the time chart in FIG.

First, it is assumed that the target operating frequency of the compressor is determined by the indoor temperature set value, the indoor temperature, etc., and the compressor motor 4 is driven at this target operating frequency. Then
The controller 7 temporarily stores the detected current value in the register I2 by the signal of the input current detected by the current detector 5 (ST1). Next, when a predetermined time TM1 (for example, 1 second) has passed (ST2), the contents of the register I2 are changed to the register I1.
Is moved to (ST3). Next, the detected current value is temporarily stored in the register I2 (ST4). That is, the detected current values before and after the predetermined time TM1 (1 second) are temporarily stored in the registers I1 and I2, respectively.
If the predetermined time TM1 (1 second) has not elapsed in step ST2, the processes of ST3 and ST4 are not performed. Then, it is judged whether or not the detected current value is equal to or higher than the operation value (for example, 14 A) (ST5). Here, if the input current of the air conditioner suddenly increases for some reason and the input current exceeds the operating value as shown at time t _{1 in} Fig. 3, go to ST6. move on. Here, in ST3 and ST4, register I1
A change (ΔI / Δt) in the input current is calculated from the detected current value before and after the predetermined time TM1 (1 second) temporarily stored in I2 and I2 (ST6), and the predetermined time TM2 (for example, according to the calculated change) is calculated.
0.2 seconds) is obtained (ST7). Then the current control is activated,
The current operating frequency of the compressor is reduced by a predetermined value (for example, 1 Hz) (ST8). Next, when the predetermined time TM2 (0.2 seconds) obtained in ST7 has elapsed (ST9), the process loops to ST2, and the processes from ST2 to ST9 are repeated until the above input current returns to the operating value (t21 in Fig. 3). It is replaced and executed. That is, TM2 (0.2
Every 5 seconds, the process of lowering the operating frequency by a predetermined value (1 Hz) is repeated 5 times, and the operating frequency is reduced by 5 Hz in a total of 1 second.

When the amount of change in the input current is large as described above, the predetermined time is shortened and the amount of decrease in the operating frequency per unit time is made larger than the conventional 1 Hz per second, so that the input current drops extremely quickly and the peak becomes small. It is possible to shorten the time required to return to the operating value, that is, the time during which a current equal to or more than the operating value flows, without exceeding the allowable value. That is, the followability and stability of the current control of the input current are better than those of the related art.

Then, when the input current returns to the operating value as shown at time t _{21 in} FIG. 3, the process proceeds from ST5 to ST10, and it is determined whether or not the current control is in operation. in this case,
Since the current control is operating, the process proceeds to ST11, where it is determined whether the detected input current is less than the release value (eg 13A),
If it is not less than the release value, the operation proceeds to step ST12 and the operating frequency of the compressor is fixed. After detecting current process becomes less clear value from (FIG. 3 t ₃₁ time) until ST2 ST12 are repeated.

Subsequently, as shown at time t _{31 in} FIG. 3, when the input current gradually decreases and becomes lower than the release value, the process proceeds from ST11 to ST13 to release the current control,
The compressor is returned to normal operation.

On the other hand, as shown from the time point t _{31 to the} time point t _{41 in} FIG. 3, when the change amount of the input current is small until the input current becomes the operation value or more, in ST7,
A predetermined time TM2 (for example, 1 second) corresponding to the change is obtained. Therefore, as shown at time t _{51 in} FIG. 3, the input current is immediately returned to the operating value as in the conventional case. At this time, since the amount of change in the input current is small, by lowering it by 1 Hz in 1 second, the peak value of the input current and the time during which current exceeding the operating value is not a problem, and the input current is extremely stable and reliable. Can be reduced to

FIG. 5 and FIG. 6 show flowcharts of other embodiments. FIG. 5 shows the processing order of ST6, ST7 and ST8 of FIG. 2 changed, and FIG. 6 shows that the detected current is temporarily stored in the register every predetermined time TM1 and ST6 of FIG. And S
This is an example in which the process of T7, that is, the process of calculating the current change amount and the process of obtaining the predetermined time TM2 corresponding thereto is performed.

In this way, the change amount of the input current is calculated, and the predetermined time corresponding to the calculated change amount is obtained, and when the input current becomes equal to or higher than the operation value, the current operating frequency of the compressor is set at the predetermined time intervals. Since the input current changes sharply when the input current changes abruptly, the operating frequency decrease amount per unit time can be increased by reducing the predetermined time, and the operating frequency can be greatly reduced. , The peak value becomes small, the input current greatly exceeds the operating value as in the prior art, and in some cases, does not reach the allowable value, and the time to return to the operating value can be shortened.

In addition, since the input current is immediately lowered to the operating value and suppressed below the allowable value, that is, the peak value of the input current is small, the operating value can be set higher than before, for example, set to 14.5A. The capacity of the air conditioner can be further improved because the outlet capacity can be used more than ever before.

[Effect] As described above, according to the control method of the air conditioner of the present invention, the change amount (ΔI / Δt) of the detected input current is detected.
To obtain a predetermined time according to the calculated change,
That is, when the change is large, a small predetermined time is obtained, and when the change is small, a large predetermined time is obtained,
When the detected current exceeds the operating value of current control,
Since the operating frequency of the compressor is lowered by a predetermined value at each predetermined time, the amount of decrease in the operating frequency per unit time can be changed according to the change in the input current, so that the input current is immediately increased. Returning to the operating value, the peak current value becomes smaller, and the time for current to flow over that operating value is shortened. In other words, the followability and stability of the current control can be improved, and the operating value can be increased. It can be set on the eyes and the capacity of the air conditioner can be improved.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a control method for an air conditioner according to the present invention, FIG. 2 is a flow chart diagram for explaining the same action, and FIG. 3 is a time chart diagram for explaining the same action. The drawings are time charts for explaining the operation of the conventional air conditioner control method, and FIGS. 5 and 6 are flowcharts for explaining the operation as another embodiment of the present invention. In the figure, 1 is a commercial power source, 2 is an AC / DC exchange circuit, 3 is a frequency variable device (inverter unit), 4 is a compressor-like motor,
Reference numeral 5 is a current detection device, 6 is an indoor temperature detection device, and 7 is a control device (microcomputer).

Claims (1)

(57) [Claims] 1. When controlling an inverter of a compressor, an input current is detected, and when the detected current value exceeds an operation value of the current control, the current control is activated to set an operating frequency of the compressor to a predetermined value. Gradually, and when the detected current value becomes less than the current control release value, in the control method of the air conditioner that releases the current control, the change amount of the detected input current is calculated, and the calculated change An air conditioner characterized in that a smaller predetermined time is obtained as the minute is increased, and the operating frequency is lowered by a predetermined value at each predetermined time when the detected current value becomes equal to or higher than the operation value. Control method.