JPH04121098A - Controller for air-conditioner - Google Patents

Abstract

PURPOSE:To enhance performance of an air-conditioning unit without causing degradation of motor efficiency or increase of the capacity of inverter element by performing constant control of the instantaneous power factor of an induction motor based on a preset reference value so that maximum efficiency can be achieved without being subjected to pulsating instantaneous load torque. CONSTITUTION:In order to perform constant control of the instantaneous power factor at a high efficiency point without being subjected to pulsation of load, phase difference are taken out between phase voltages Vu, Vv, Vw outputted from an inverter 10d and motor currents Iu, Iv, Iw thus producing phase difference signals. Assuming the phase difference signals and an induction motor 1a have four poles, signals are produced twelve times per single revolution. The phase difference signals are fed to an instantaneous power factor detecting circuit 19 thus producing an instantaneous power factor signal cosphi. The instantaneous power factor signal is then compared, in a comparator 21, with a reference power factor command signal cosphi* fed from a reference frequency command-reference power factor command converting circuit 20, and an instantaneous power factor control circuit 22 performs learning control thus controlling the power factor constantly so that the induction motor 1a exhibits a maximum efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air conditioner, and particularly to a control device for a compressor motor thereof.

[Prior Art] Fig. 13 shows, for example, a speed control method for a brushless DC motor capable of handling pulsating loads, which was presented at the National Conference of the Institute of Electrical Engineers of Japan in 1986.

FIG. 13 shows an overall configuration diagram of a system in which the control device is applied to an air conditioner, and FIG. 14 shows a configuration diagram of a control system for a hermetic compressor, which is the main part of FIG. 13.

In the figure, (1) is a compressor, (2) is a condenser, (3) is a capillary tube, and (4) is an evaporator, which are each connected in a closed loop to form a refrigeration cycle.

(5) is a position detector that detects the rotational position of the compressor (1). (6) and (7) are detectors installed in the condenser (2) and evaporator (4), respectively;
1) Detects and detects load information applied to

(8) is a signal conversion unit, and each of the above-mentioned detectors (6), (7
) etc. is converted into a digital quantity. (9)
is a control section that performs arithmetic processing based on the input signal from this signal conversion section, and is composed of a microcomputer or the like.

(10) is a variable frequency power converter, which is a rectifier (], Ob) that converts the AC TL flow (1OA) into DC so as to supply variable frequency power to the induction motor (1a) of the compressor (1).
and a smoothing capacitor (1ob) that smoothes the rectifier (1ob).
0c) and an inverter that converts the DC output into three-phase AC of any frequency based on the control signal from the control unit (9).
(1, Od) and a DC power detector (
loe). (11) is an AC current detector; (12) is a current control unit (13) that compares and calculates the current command signal output from the control unit (9) and the current value from the DC τft detector (10e); The above control unit (
This is a base amplifier that amplifies the output signals from the current control section (9) and the current control section (2) and sends it to the inverter (10d).

Next, the operation will be explained.

Information on the load applied to the compressor (1) is detected by detectors (6) and (7) of the refrigeration cycle, and the rotational position of the compressor (1) is detected by a position detector (5).

These detection signals are converted into digital quantities by a progressive conversion section (8) and sent to a control section (9).

The control unit (9) calculates and determines the magnitude of the load 1 and the rotational position of the compressor (1) based on the signal, and outputs the result as a current command signal. The current control unit (12) that receives this current command signal performs a comparison calculation with the motor current detected by the DC current detector (10e), outputs the difference signal to the base amplifier (13), and outputs the difference signal to the base amplifier (13). The electric motor (1a) is controlled by amplifying the signal and outputting it as a control signal to the inverter (], 0ct) to control the three-phase AC power.

The controlled compressor (1) outputs the load torque T3 shown in FIG. 15 and the motor output torque T synchronized with the waveform change. Also in the rotating shaft system of the compressor (), the excitation torque (T, , -T,) on the non-rotating body side becomes zero.

Problem 1 to be Solved by the Invention Since the conventional air conditioner control device is configured as described above, it is particularly necessary to control the compressor motor output torque to follow the load torque.

There were problems that resulted in a decrease in motor efficiency and an increase in the number of conversion elements in the inverter.

Further, when the electric motor of the compressor is a brushless DC motor, there are problems in that the characteristics of the field magnet deteriorate at high temperatures and the field magnet becomes brittle when rotated at high speed.

This invention was made to solve the above-mentioned problems, and provides an air conditioner control device that can improve the performance of an air conditioner unit without causing a decrease in motor efficiency and an increase in inverter element capacity. The purpose is to

In addition, KAI 6H [an air conditioner control device equipped with a hermetic compressor with stable high-speed rotation and low vibration, using an induction motor that does not cause deterioration of the characteristics of stone at high temperatures or brittleness at high-speed rotation. The purpose is to obtain.

Means for Solving the Problem J A control device for an air conditioner according to the first invention includes a variable frequency power converter, a control means for controlling the second variable frequency power converter, and a three-phase AC output terminal. An instantaneous power factor detection circuit comprising an instantaneous power factor detector and receiving an output from the instantaneous power factor detector, a reference frequency command reference power factor command conversion circuit, a comparator, an instantaneous power factor control circuit, and a power factor The control means includes a power factor/voltage conversion circuit and a base amplifier circuit that amplifies the output from the power factor/voltage conversion circuit and outputs the amplified output to the inverter of the variable frequency power conversion section.

The second invention includes a slip frequency calculation circuit, a single frequency control circuit, a frequency-voltage conversion circuit, and a base amplifier that amplifies the biasing force of the frequency-voltage conversion circuit and supplies it to the inverter of the variable frequency power conversion section. The control means consists of a circuit.

[Operation] In the first invention, the control means controls the instantaneous power factor of the induction motor so that it reaches the maximum efficiency based on a preset reference value, that is, so that the input power of the air conditioner becomes the minimum value. Since it is controlled at a constant level without being affected by the instantaneous pulsation of the load torque of 1 herc, the efficiency of the motor and the efficiency of the unit 1 are increased, and the unit performance is improved without causing an increase in the inverter element capacity. It is possible.

Further, in the second invention, the control means operates the power supply frequency and power supply voltage of the variable frequency power converter by the motor slip frequency signal calculated from the instantaneous motor power factor,
Since it is controlled to eliminate instantaneous rotation fluctuations of the compressor, a compressor with stable rotation and low vibration can be realized.

[Embodiments] Embodiment 1 Figure 1 shows a control device for an air conditioner according to an embodiment of the present invention, in which (1) is a compressor, and (, 19) is a three-phase induction 4 that drives the second compressor. @Motive (14) is the above compressor (1
), (4) is an indoor heat exchanger connected to this four-way valve via refrigerant distribution v (15), (1
6) is an indoor fan, and (2) is an outdoor heat exchanger.

It is connected to the four-way valve (4) via a refrigerant pipe (15). (17) is an outdoor fan, (3) is an expansion valve,
It is arranged between the L-distributed indoor heat exchanger (4) and the outdoor exchanger (2).

(10) is a variable frequency power converter that converts the AC power source (
It consists of a rectifier (101)), a smoothing capacitor (10c), an inverter (10d), and a DC current detector (1, Oe) connected to the induction motor (1a), and the three-phase AC output end is connected to the induction motor (1a). ing.

(18) is an instantaneous power factor detector provided at each of the three-phase AC output ends, and (19) is an instantaneous power factor detection circuit that shapes the power factor signal output from the power factor detector (18) into a waveform. are doing. (20) is a reference frequency command-reference power factor command conversion circuit, which receives a reference frequency command f from the outside.

The reference power factor command cosφ' is obtained from .

(21) is a comparator that outputs the reference power factor command cos ψ'' and the power factor signal c output from the instantaneous power factor detection circuit (19).

A comparison operation is performed on Sφ.

(22) is an instantaneous power factor control circuit that compares and calculates the instantaneous power factor output from this comparator, and command cosφ.

is output to the power factor/'voltage conversion circuit (23). (2
4) is the voltage command signal V converted by the power factor/voltage conversion circuit (23). The inverter (10d) of the variable frequency power converter (10) is
) to the voltage command signal■. is amplified and supplied.

(25) represents the instantaneous power factor detection circuit (19), the reference frequency command-reference power factor command conversion circuit (20), and the comparator (21).
) Instantaneous power factor control circuit (22), power factor/voltage conversion circuit (2
3) and a base amplifier circuit (24).

FIG. 3 is a peripheral and detailed block diagram of the instantaneous power factor control circuit.

In the figure, 9 frequency reference command - power factor reference command conversion circuit (
20) is a reference speed signal f. , power factor data indicating the maximum efficiency of the electric motor (1a) and the variable frequency power converter (10) at a certain frequency is referred to. The referenced power factor reference signal is a deviation (difference) from the instantaneous power factor signal cosφ output from the instantaneous power factor detection circuit (19).
and sends it to the instantaneous power factor control circuit (22). The instantaneous power factor control circuit (22) controls (0°) for each section of the instantaneous power factor signal.
12 signals in ~360° interval (for 4-pole motor),
Learn (integrate) the difference (Δcosφ) of the instantaneous power factor signal.

Next, the operation of the control device of the invention according to the first embodiment will be explained. First, the heating operation of the refrigerant circuit will be briefly explained.

The refrigerant compressed by the compressor (1) passes through the four-way valve (14) and piping (15) under high temperature and high pressure to the indoor heat exchanger (
4).

Here, cold air inside the room is passed through the heat exchanger (4) by the fan (16) on the indoor side, and heat is exchanged with the high temperature and high pressure refrigerant, and the air is blown into the room to heat the room. At this time, the refrigerant flowing through the heat exchanger (4) is expanded by the expansion valve (3) and becomes a low-temperature, low-pressure liquid. This liquid refrigerant is then sent to the outdoor heat exchanger (2), absorbs heat, becomes gaseous again, returns to the compressor (1), and is compressed again.

Here, the induction motor (1a) is directly connected to the compressor (1), and nine rotation operations are converted into compression operations.

In such heating operation, the compressor (1).

For example, in the case of a rotary compressor, a dielectric motor (1
As shown in Fig. 4(c), the efficiency n of a) is as shown in Fig. 4(b).
It will pulsate due to the slip change shown in Figure 2, and the average value of efficiency will decrease. Therefore, in the control device shown in the embodiment of the first invention, in order to control the instantaneous power factor constant at a high efficiency point without being affected by the pulsating load, an inverter is used as shown in FIG. The voltage (V) of each phase outputted by (lod)
,,V,,V,) and motor current (1,,I,,I,)
The phase difference is taken and used as one phase difference signal. If the induction motor (1a) has 4 poles, the phase difference signal is 12 out of 1 rotation.
times.

I get a signal. This phase difference signal is sent to the instantaneous power factor detection circuit (
19) Obtain the feed and instantaneous power factor signal (COSφ).

A comparator (21) compares this instantaneous power factor signal with a reference power factor command signal cosφ' from a reference frequency command-reference power factor command conversion circuit (20), and learning control is performed by an instantaneous power factor detection circuit (22). By doing so, the instantaneous power factor of the induction motor (1a) is always controlled to be a power factor that exhibits maximum efficiency.

When the instantaneous power factor of the induction motor (1a) is controlled to be constant, the efficiency is also controlled to be high and constant as shown in FIG. 6(c).

Also, there is no pulsation in the motor current. This situation is shown in FIGS. 6a and 6b.

Furthermore, since the motor efficiency and the conversion efficiency of the variable frequency power converter (lO) are directly related to the performance of the air conditioning unit, high C2○, P (performance coefficient) can be obtained as a result.

Incidentally, FIG. 7 shows changes in the motor power ratio on a motor characteristic diagram, and roughly speaking, the motor power ratio changes as indicated by the arrows in accordance with the pulsating load.

Embodiment 2 The second embodiment is the same as the first embodiment up to the variable frequency power converter (10) and instantaneous power factor detection circuit (19) shown in FIGS. 1 and 2, so their explanation will be omitted.

In FIG. 8, (26) is a slip frequency calculation circuit which calculates the slip frequency fs of the electric motor (1a) from the instantaneous power factor signal output from the instantaneous power factor detection circuit (19). (2
7) is a frequency control circuit that controls the frequency fS and the frequency reference signal f. ′, the frequency command signal f0 is compared and calculated. (28) is a frequency-voltage conversion circuit and a frequency control circuit (
Frequency command signal f output from 27). ■ Voltage command signal. Convert to (24) is a base amplifier circuit that amplifies the signal output from this frequency-voltage conversion circuit (28) and supplies it (10d) to the inverter of the variable frequency power conversion section (10).

FIG. 9 is a detailed block diagram of the two-frequency control circuit. In the figure, the slip frequency fs calculated from the Veri frequency calculation circuit (26) is calculated by the delay device (27at) (27a2).
(27as) (27a4), adder (27b, ) (2
7b2) (27b3) (27b4), amplifier (27c
) etc. for each section of the instantaneous power factor signal (0° to 360
'Learning control is integrated for each section (in the case of a 4-pole motor) every 30° section (for a 4-pole motor). The learning-controlled frequency is the frequency reference signal f. ” and are added by the adder (27b,) to produce the frequency command signal f.

Next, the operation of the control device according to the second embodiment of the invention will be explained. Here, since the heating operation of the refrigerant circuit is the same as in the first embodiment, the explanation will be omitted, and the case where the compressor (1) is one, for example, a rotary compressor, will be explained.

The load torque becomes T6 in FIG. At this time, the torque generated by the induction motor (1a) is T. Assuming that the torque is almost constant as shown in FIG.

Therefore, if the generated torque is controlled to follow the load torque To, the rotor of the induction motor (1a) will rotate smoothly without being vibrated.

Next is the load torque T. A control method in which the generated torque T completely follows the torque will be described below.

As shown in Figure 5, the voltage (V, , V, , VW) of each phase output from the inverter (10d) and the motor current (1, , ,
The phase difference between Iヮ, IvN) is detected every time the polarity of each phase changes and is used as one phase difference signal. The phase difference signal is generated by an induction motor (1
Assuming that a) has four poles, a signal is obtained 12 times in one rotation. This phase difference signal is sent to an instantaneous power factor detection circuit (19) to obtain an instantaneous power factor signal.

This instantaneous power factor signal is calculated into a slip frequency using the motor characteristic diagram shown in FIG. This circuit is the slip frequency calculation circuit (26) as described above. The frequency control circuit (27) delays the obtained full frequency f5 for each instantaneous power factor signal by a delay device (27a), and further delays the obtained frequency f5 by an adder (
27b), the learning function works, and the frequency-voltage conversion circuit (28) converts the load torque T into a voltage command signal, as shown in FIG. 10(c).
. The generated torque T is controlled to follow the electric motor (1a
) can realize a control system without rotational fluctuations.

Therefore, with the control device of the present invention controlled in this manner, it is possible to control a hermetic compressor with low vibration and no speed fluctuations.

[Effect of the invention] Since this invention is configured as explained above,
This produces the effects described below.

In the invention of claim 1, the control means includes an instantaneous power factor detection circuit, a reference frequency command-reference power factor command conversion circuit, an instantaneous power factor control circuit that controls the instantaneous power factor using the output of the comparator, and a power factor/ With voltage conversion circuit.

Since the base amplifier circuit amplifies the output from this power factor/voltage conversion circuit and supplies it to the variable frequency power conversion section, the inverter element capacity does not increase.
High unit performance can be obtained.

Further, in the invention of claim 2, the control means includes an instantaneous power factor detection circuit and a perfect frequency calculation circuit.

It consists of a slip frequency control circuit, a dual frequency-voltage conversion circuit, and a base amplifier circuit that amplifies the output of this frequency-power conversion circuit and supplies it to the variable frequency power conversion section, so it is inexpensive and has no speed fluctuations. This has the effect of obtaining a control device equipped with a vibrating hermetic compressor.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of an air conditioner that is Embodiment 1 of the present invention, FIG. 2 is a block diagram showing the control device of FIG. 1, and FIG. 3 is a block diagram showing the main parts of FIG. 2. FIG. 4 is a characteristic diagram showing the efficiency of an induction motor. Figure 5 is a characteristic diagram showing three-phase phase difference signals, Figure 6 is a characteristic diagram when the instantaneous power factor of the motor is controlled to maximum efficiency, and Figure 7 is a characteristic diagram showing the three-phase phase difference signal.
The figure is a power factor change characteristic diagram of an electric motor, FIG. 8 is a block diagram showing a control device which is a second embodiment of the invention, FIG. 9 is a block diagram showing the main part of FIG. 8, and FIG. 10 is an embodiment. 2, a characteristic diagram showing the load torque of the control device, Figures 1 and 1 are the overall configuration diagram of the conventional control device, Figure 12 is the configuration diagram of the control system of the electric motor, and Figure 13 shows the load torque of Figure 12. It is a characteristic diagram. Note that (10) is a variable frequency power conversion unit, (18)
is an instantaneous power factor detector, (19) is an instantaneous power factor detection circuit,
(20) is a reference frequency command-reference power factor command conversion circuit;
(21) is a comparator, (22) is an instantaneous power factor control circuit,
(23) is a power factor/voltage conversion circuit, (24) is a base amplifier circuit, (25) is a control means, (26) is a subli frequency calculation circuit, (27) is a frequency control circuit, (2
8) is a frequency-voltage conversion circuit. In the figure. Same sign. Indicates the same or equivalent part.

Claims (2)

[Claims] (1) In a control device equipped with a variable frequency power converter that drives and controls a hermetic compressor in an air conditioner using variable frequency AC power, instantaneous power factor detection is provided at the output end of the variable frequency power converter. an instantaneous power factor detection circuit comprising a control means for controlling the variable frequency power converter and receiving an output from the instantaneous power factor detector;
A reference frequency command conversion circuit, an instantaneous power factor control circuit that controls the instantaneous power factor using the output of the comparator, a power factor/voltage conversion circuit, and an output from the power factor/voltage conversion circuit that is amplified to adjust the variable frequency. A control device for an air conditioner, characterized in that a control means is constituted by a base amplifier circuit that outputs to a power conversion section. (2) In a control device for a hermetic compressor equipped with a variable frequency power converter that drives and controls the hermetic compressor using variable frequency AC power, the instantaneous power factor detector and the variable frequency power converter are controlled. An instantaneous power factor detection circuit that includes a control means and receives an output from an instantaneous power factor detector, a slip frequency calculation circuit, a frequency control circuit, a frequency-voltage conversion circuit, and amplifies the output of this frequency-voltage conversion circuit. A control device for an air conditioner, characterized in that a control means is constituted by a base amplifier circuit which supplies the variable frequency power converter to the variable frequency power converter.