JPH0720397B2 - Inverter device for room air conditioner - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inverter device for driving an induction motor of a compressor for room air conditioners.

[Conventional technology]

As a conventional method for driving an induction motor at an optimum voltage, as shown in Japanese Patent Publication No. 61-20236, there is a certain value of a delay phase difference (same in power factor) between a current waveform and a voltage waveform of an induction motor. A well-known method for controlling the voltage (phase difference detection optimum voltage control) is well known.

The principle of operation is that "if the voltage is too high, everything becomes small and the phase difference becomes large, and conversely if the voltage is too low,
The characteristics of the induction motor that "slip is large and the phase difference is small" are used. Therefore, if the phase difference becomes large, the voltage is too high, so lower the voltage,
If the phase difference becomes smaller, the voltage is too low,
Control to raise the voltage.

This conventional example will be described with reference to FIG.

In FIG. 6, the induction motor 21 includes a DC power source 70 which is obtained by once converting the commercial power source 204 into a DC voltage by the AC / DC converter 203.
Is then driven by an AC power supply which has been converted into a three-phase AC of a desired frequency and voltage by a DC / AC converter 10.

At that time, the polarity signal 32 of the voltage applied to the induction motor 21
Then, the phase difference detection circuit 30 detects the phase difference of the polarity signal 31 of the current flowing through the induction motor 21.

Next, the detected phase difference and the phase difference reference are compared, and if the detected value is larger than the reference value, the voltage is lowered, and if the detected value is smaller than the reference value, the voltage is raised.

[Problems to be Solved by the Invention]

The conventional phase difference detection optimum voltage control type inverter device is configured as described above, and the voltage is controlled.

However, when applied to the inverter room air conditioner shown in FIG. 3, the following problems have occurred.

First, the operation of the inverter room air conditioner will be described with reference to FIG.

The inverter room air conditioner includes an indoor exchanger 201 that exchanges heat between the indoor air and the refrigerant that flows through the refrigeration cycle, an outdoor heat exchanger 200 that exchanges heat between the outdoor air and the refrigerant that flows through the refrigerant cycle, and pressurizes and circulates the refrigerant. It is composed of a compressor 20 composed of an induction motor 21 and a compression mechanism section 22.
The induction motor 21 for driving is driven by an AC power source which has once converted the commercial power source 204 into a direct current by the AC / DC converter 203 into a three-phase alternating current of a desired frequency and voltage by the DC / AC converter 10. It

Here, since the compression mechanism section 22 has strokes of suction, compression, and discharge during one rotation, as shown in FIG. 4 (a), the torque generated by the induction motor varies depending on the rotation mechanical angle.

Next, the waveform of the current flowing through the induction motor will be described with reference to FIGS. 4 and 5.

The torque generated by the induction motor is almost indicated by the envelope of the waveform obtained by superimposing the absolute values of the phase current waveforms for three phases.
The absolute value of the phase current waveform for each phase is as shown in FIG.

That is, the phase current waveform for one phase is as shown in FIG. 4 (b).

FIG. 5 (a) shows a longer time span of the current waveform for one phase in FIG. 4 (b).

As shown in FIG. 5 (a), the amplitude of the phase current does not change, and the level changes in the slip cycle.

Therefore, the zero-cross point of the current, which should originally be at the center of the amplitude of the phase current, fluctuates in the slip cycle. As a result, the phase difference between the voltage and the current also fluctuates in the slip cycle as shown in FIG. 5 (b).

In the conventional voltage control based on the phase difference, since the voltage is controlled by the phase difference data every time, as shown in FIG. 5C, the output voltage also fluctuates in the slip cycle due to the fluctuation of the phase difference data.

As described above, when the conventional phase difference detection optimum voltage control type inverter device is applied to a room air conditioner, there is a problem that the output voltage hunts (pulsates) in a slip cycle.

The invention has been made to solve the above-mentioned problems, and an object thereof is to obtain an inverter device capable of operating at an optimum voltage while suppressing hunting of the output voltage due to a compressor artery load.

[Means for Solving the Problems]

In order to achieve the above object, the present invention controls the voltage of an AC power supply with the latest multiple times of phase difference data stored and averaged, instead of controlling the voltage of an AC power supply with each phase difference data. In detail, the room air conditioner inverter device is configured as described in (1) and (2) below.

(1) A room air conditioner inverter device for converting a DC power supply into an AC power supply having a desired voltage and frequency and applying the AC power to an induction motor, which is a drive source of a compressor, and an AC voltage applied to the induction motor. Phase difference detecting means for detecting the phase difference of the currents flowing in the induction motor for each cycle of the alternating current, and phase difference data for each time detected by the phase difference detecting means, the frequency of the alternating current power supply / expected slip frequency =
The storage means for storing the N latest N times, the phase difference data averaging means for averaging the N times of data stored in the storage means, and the alternating current based on the output of the phase difference data averaging means An inverter device for a room air conditioner, comprising: a voltage control means for controlling a voltage of a power supply.

(2) A room air conditioner inverter device for converting a DC power supply into an AC power supply having a desired voltage and frequency and applying the AC power to an induction motor that is a drive source of a compressor, the AC voltage being applied to the induction motor and induction. Phase difference detection means for detecting the phase difference of the current flowing through the electric motor for each cycle of the alternating current,
The storage means for storing the latest plurality of phase difference data detected by the phase difference detection means for the latest plural times, and the average of the latest m times of phase difference data among the plural times of phase difference data stored in the storage means are averaged. Phase difference data averaging means, a slip estimating means for estimating a slip frequency or a slip cycle based on the output of the phase difference detecting means, and a frequency of the AC power supply or a cycle of the AC power supply and the slip estimating means. Based on the slip frequency or slip period, the above-mentioned m
A room air conditioner inverter device comprising: an averaging number calculation means for calculating the value of ## EQU1 ## and a voltage control means for controlling the voltage of the AC power supply based on the output of the phase difference data averaging means.

[Action]

With the configurations of (1) and (2), the voltage of the AC power supply is
The phase difference data obtained by averaging the phase difference data every time is not controlled by the pulsating load of the compressor.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to Examples.

FIG. 1 is a block diagram of a "room air conditioner inverter device" according to a first embodiment of the present invention.

In the figure, 70 is a DC power supply obtained by converting a commercial power supply to DC by an AC / DC converter (not shown), 10 is a DC / AC converter, 20 is a compressor, 30 is a phase difference between the voltage applied to the induction motor and the flowing current. Is a phase difference detection circuit for detecting the phase difference, and 60 is a voltage control means for comparing the detected phase difference with the phase difference reference and outputting a voltage correction command, which are equivalent to the conventional ones.

40 and 50 are parts added in this embodiment, and 40 is a phase difference data storage circuit with a shift register function for storing the latest N times of phase difference data (AC power supply frequency / expected slip frequency). , 50 are phase difference data averaging circuits for averaging N times of data.

Next, the operation will be described.

In FIG. 2, (a) is a diagram showing hunting with the same phase difference as in FIG. 5 (b), and A, B, C, ... N, A ', B',
C ′, ... N ′ are phase difference data strings obtained for each cycle of the drive frequency (the frequency of the alternating current applied to the induction motor 21). FIG. 2B shows a data string of the average value of the phase differences obtained by averaging N phase differences. A-A 'is the average value of N data between B and A', and BB '. Is N between C and B '
The average value of individual data is shown. In FIG. 1, the output of each phase difference detection circuit 30 is A, B, C, ..., N, A ′,
The sequence of B ', C' ..., N'is sequentially stored in the latest N times of phase difference data storage circuit with shift register function 40. That is, the data of A'in FIG. 2A is the phase difference detection circuit.
When it is obtained from 30, the A data is discarded, N pieces of data from B to A'are stored in the phase difference data storage circuit 40, and B'data is obtained from the phase difference detection circuit 30. Data of B is discarded, N from C to B'is
The individual pieces of data are stored in the phase difference data storage circuit 40.

Next, when N pieces of data are shifted, the phase difference data averaging circuit 50 averages the phase difference data.

The voltage control means 60 determines the magnitude of the averaged phase difference data and the phase difference reference, and as in the conventional case, if the average value is larger than the reference value, lower the voltage, and if the average value is smaller than the reference value, A voltage correction command is sent to the DC / AC converter 10 so as to increase the voltage.

According to this method, as shown in FIG. 2 (b), the phase difference (average value) does not fluctuate in the cycle of the slip frequency, so that the output voltage does not fluctuate as shown in FIG. 2 (c).

FIG. 7 is a block diagram of a "room air conditioner inverter device" according to a second embodiment of the present invention.

In FIG. 7, except for parts 40, 50, 71 to 73, the configuration is the same as that of the first embodiment shown in FIG. 1, and therefore the description thereof is omitted here. 40 is the latest n times of phase difference data (multiple times)
Phase difference data storage circuit with shift register function to store,
50 is a phase difference data averaging circuit for averaging the latest m times of phase difference data among the plurality of times, 71 is a phase difference detection circuit 30
A storage circuit that stores the latest multiple times of phase difference data detected in step 72, a slip frequency estimation circuit that estimates the slip frequency from the multiple times phase difference data stored in the storage circuit 71, and 73 is a phase difference This is an averaging circuit calculation circuit for calculating the number of samples m to be averaged by the data averaging circuit 50 from the output of the slip frequency estimating circuit 72 and the inverter drive frequency.

Next, the operation will be described.

In FIG. 8, (a) is a diagram showing hunting with the same phase difference as in FIG. 5 (b), and A, B, C, ... P are drive frequencies (frequency of alternating current applied to the induction motor 21). ) Is a phase difference data string obtained for each cycle.

In FIG. 7, the data for each phase difference detection circuit 30 is
A, B, C, ... I are sequentially stored in the phase difference data storage circuit 40 with the shift register function for the latest plural times, for example, 14 times. That is, in FIG. 8 (a), when the O data is obtained from the phase difference detection circuit 30, the A data is discarded, the 14 data from B to O, and the P data are detected as the phase difference. When it is obtained from the circuit 30, the data of B is discarded and 14 pieces of data from C to P are stored in the phase difference data storage circuit. Each time the data in the phase difference data storage circuit 40 is shifted, the phase difference data averaging circuit 50 follows the instruction of the averaging count calculation circuit 40 and outputs the latest m times of data from the plurality of data in the phase difference storage circuit 40. Select and average.

The voltage control means 60 determines the magnitude of the averaged phase difference data and the phase difference reference. If the average value is larger than the reference value, the voltage is lowered, and conversely the average value is the reference, as in the first embodiment. If it is smaller than the value, a voltage correction command is sent to the DC / AC converter 10 so as to increase the voltage.

The slip frequency estimating circuit 72 estimates the slip frequency based on the cycle in which substantially the same data appear in the phase difference data similar to A to P of FIG.

The averaging count calculation circuit 73 determines the averaging count by the following calculation, and instructs the phase difference averaging circuit 50 on the averaging count m.

An example of the operation will be described with reference to FIG. (B),
The averaged phase difference data is shown in (c).
(B) shows, for example, a data string of the average value of the phase difference data obtained by averaging the phase difference data for seven times, A-G is the average value of the data of seven times A to G in (a), and B-H is B to H
The average value of the data of 7 times is shown. Similarly, (c) shows a data string of the average value of the phase difference data obtained by averaging the phase difference data for 9 times, and AI is 9 from A to I.
The average value of the batch days, BJ indicates the average value of the data of 9 batches from B to J.

In (b), since the average value period is shorter than the slip period, the averaged phase difference data is hunting.

However, in the present embodiment, in the averaging count calculation circuit 73,
Since the averaging number m = 9 that matches the slip cycle is calculated, the averaged phase difference data has a stable value without fluctuation as shown in (c), and the output voltage of the DC / AC converter 10 is As shown in (d), it stabilizes and does not hunt. Even if the slip cycle fluctuates, an appropriate averaging count m is calculated by the averaging count calculation circuit 73 according to the fluctuation, so that the output voltage of the DC / AC converter 10 does not hunt.

In the present embodiment, the number of times of averaging is calculated based on the ratio of the slip frequency and the power supply frequency, but the present invention is not limited to this. Of course, the number of times of averaging may be calculated based on

Further, in the present embodiment, the memory circuit 71 is provided separately from the phase difference data memory circuit 40, but the data of the circuit 40 can be introduced into the slip frequency estimating circuit 72 and the memory circuit 71 can be omitted.

Further, the slip frequency estimation circuit 72 does not necessarily have to be operated every time the phase difference detection circuit 30 detects data, and may be operated in a cycle longer than the data detection cycle.

〔The invention's effect〕

As described above, according to the present invention, the voltage-current phase difference of the induction motor that drives the pulsating load of the compressor is used for voltage control by averaging in the cycle of the fluctuation.
Hunting of the output voltage can be suppressed.

[Brief description of drawings]

FIG. 1 is a block diagram of the first embodiment of the present invention, FIG. 2 is a diagram showing the operation of the same embodiment, showing the fluctuation of the phase difference, the averaged phase difference, and the waveform of the output voltage. FIG. 3 is the inverter. FIG. 4 is a block diagram of a room air conditioner, FIG. 4 is a waveform diagram of torque generated by an induction motor and a phase current, FIG. FIG. 7 is a block diagram of a conventional inverter of the phase difference detection optimum voltage control system, FIG. 7 is a block diagram of a second embodiment of the present invention, and FIG. 8 is an explanatory diagram of the same embodiment. In the figure, 10 is a DC / AC converter, 20 is a compressor, 21 is an induction motor, 30 is a phase difference detection circuit, 40 is a phase difference data storage circuit, 50 is a phase difference data averaging circuit, 60 is a voltage control means, 72 is a slip frequency estimating circuit, and 73 is an averaging frequency calculating circuit. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (2)

[Claims] 1. An inverter device for a room air conditioner, which converts a DC power supply into an AC power supply of a desired voltage and frequency and applies the AC power to an induction motor which is a drive source of a compressor, the AC voltage being applied to the induction motor. And the phase difference detection means for detecting the phase difference between the currents flowing in the induction motor for each cycle of the alternating current, and the phase difference data for each time detected by the phase difference detection means, the frequency of the alternating current power source / expected Based on the storage means for storing the latest N times of slip frequency = N, the phase difference data averaging means for averaging the N times of data stored in the storage means, and the output of the phase difference data averaging means. A room air conditioner inverter device, comprising: a voltage control unit that controls the voltage of the AC power supply. 2. An inverter device for a room air conditioner, which converts a DC power supply into an AC power supply having a desired voltage and frequency and applies the AC power to an induction motor which is a drive source of a compressor, the AC voltage being applied to the induction motor. And a phase difference detecting means for detecting the phase difference between the currents flowing through the induction motor for each cycle of the alternating current, and a storage means for storing the latest multiple times of the phase difference data detected by the phase difference detecting means, Phase difference data averaging means for averaging the latest m times of phase difference data among a plurality of times of phase difference data stored in the storage means, and a slip frequency or a slip cycle based on the output of the phase difference detecting means. And a value of m based on the frequency of the AC power supply or the cycle of the AC power supply and the slip frequency or slip cycle estimated by the slip estimation means. Averaging count and calculation means, the phase difference data averaging means room air conditioner inverter apparatus characterized by comprising a voltage control means for controlling the voltage of said AC power supply based on the output of that.